As the title suggests, I was wondering if there were any planetary based weapons that could destroy an orbiting Imperial Cruiser, that was of imperial origin, could a vortex missile do it? Or would it be less straightforward than that?

Cheers!

i think basic nova cannons and other planetary defensive weapons would be capable.

Planetary Defence Lasers are capable of doing so. I think in Storm of Iron there's a planetary torpedo defence installation too. No real reason (other than not STC allowed) that any ship based Imperial weapon could not be based on a planet. I suspect it would take multiple shots from Imperial weaponry though. They'd have to penetrate the void shields of the vessel first.

As for a vortex missile in particular, I'm unsure if they can be scaled up to naval warfare. If a normal battlefield one was set off in the right place though it could well destroy or at least cripple the ship.

Usually they're described as batteries of equivalent to naval weapons.

You do get naval torpedos which can be fired from the surface. One appears in storm of iron, which targets the ground. And one appears in the first blood angels book, where it knocks a chaos space marine battle barge out of orbit.

For information about planet to orbit weapons and their relative strength compared to cruiser weapons and durability please refer to BFG rulebook page 146, specifically the entries for defence laser silos, missile silos, and planetary air bases.

Realistically it would be hard for a surface weapon to target and destroy an orbiting vessel due to the distances involved, especially if the ship was randomly adjusting course to protect itself.

Conversely static surface weapons would be ridiculously easy to track and destroy from orbit.

 Ugly Green Trog wrote:
Realistically it would be hard for a surface weapon to target and destroy an orbiting vessel due to the distances involved, especially if the ship was randomly adjusting course to protect itself.

Conversely static surface weapons would be ridiculously easy to track and destroy from orbit.

It's not nearly so clear-cut as that; like many SF/scifi related things, there's a lot of "meta" stuff involved, like tech base, development of a planet, where the strategic objectives are, strategic/tactical doctrine, yadda yadda yadda, etc etc ad nauseum.

In the case of 40K, planetary installations can boast firepower and durability comparable to an orbiting warship, and there's enough evidence throughout numerous sources that alternative deployment methods are sometimes required because the desired target is defended by heavy anti-orbital weaponry. One of the short stories in the Damocles anthology, for example, gives the reason for why a proper drop pod assault isn't possible by a small force of two SM squads- the ship that they took would have to close into low orbit, which would be within range of the anti-orbital guns of the city that they're supposed to cleanse of Tau presence.

Realism-wise, planets tend to be a bit of a clusterfeth of gak that messes with accurate targeting. Depending on technical assumptions, a planetary defense laser can easily be more durable and longer-firing than an equivalent warship installation, on account of the defense battery being able to use the planet as a heat sink, and bury most of its important bits (FCS, C3, power supply) deep underground, beyond the reach of enemy fire. Similarly, there's also plenty of room for submarine-deployed anti-orbital lasers, which could even be fired from underwater, or more likely operated as a "hit and run" weapon, that surfaces, fired, and then dives and hides once more. For missile armaments, it's entirely possible that semi-disposable anti-orbital missile artillery could be deployed a la the WW2-era Katyushas, at which point if you see it, it's already fired, and the only thing you scragged was a $10k truck, instead of the $10 million missile payload it carried (and already fired) at your $10 billion spaceship.

But again, this is generally dependent on your going in assumptions. It's entirely possible that it could be as you say, but it's equally the case that it might be the complete opposite. It could be considered a bit of a Purple-vs-Green conundrum.

If you'd like to know more, then I'd refer you to the website "Atomic Rockets", which has a lot of useful information on the subject.

Planetary defense installations do have a distinct advantage over a ship - they can be as large as needed while the ship can only fit so many things. Planetary power stations aren't limited to what fits in a hull, targeting installations can be large and widely spread out and might even get targeting data from orbital assets before the ship is in range to pinpoint ground targets. And the guns could be much larger than you'd fit on a warship since space isn't a problem.

Ground installations might well get to shoot while the cruiser is still outside the range of it's own guns.

A ground-based torpedo is basically an ICBM. Hell, some ship torpedos are half the size of a Saturn rocket or more.

 Melissia wrote:
Usually they're described as batteries of equivalent to naval weapons.

Indeed! That's the stats that they were given in the BFG rulebook, anyway. Page 146 describes three types of surfaced-based defenses you could have: Laser silos (acted as lances), missile silos (acted as torpedoes), and air bases (generated attack craft). The book doesn't specifically state what the size or warhead of the missiles are, but given their stats it stands to reason they would be the same plasma torpedoes Imperial warships employ. No mention of a surface-based Nova cannon, though there is no reason to think that the short list in the BFG rulebook is all-inclusive.

The better question is if you really want to blow up a kilometer plus long object in orbit that's going to act like a fragmentation grenade detonated near you. See the Endor Holocaust after the destruction of the Second Death Star.

But, if you don't care about skyscraper sized objects raining on your head, you certainly can blow up a ship in orbit. Planets, especially fortress worlds or Adeptus Astartes monastaries typically have ginormous lance (laser) batteries able to blast targets out of orbit. IIRC, they typically are also stronger than most lance batteries outside those mounted on large battleships, as they can generate more power. There's more free space on a planet, so you can store bigger reactors to power even more powerful shots to carve through void shields.

There are indeed planet based weapons capable of firing on orbiting ships. They're roughly the same weapons as on the ships themselves. Planet based lance, macrocannon, and missile silo emplacements.

Planet based weapon systems are individually more powerful than the guns mounted on the ships due to not having size constraints, they're also usually very well shielded as well. Both by being underground and having actual shields. Especially since ships have to go into low orbit to fire on the planet, thus putting themselves in range of the planetary guns. Many planets have truly formidable defenses.

Defensive emplacements like this are usually so strong that it forces attacking forces to land elsewhere on the planet and neutralize the guns before the ships can move into position.

 Grey Templar wrote:
There are indeed planet based weapons capable of firing on orbiting ships. They're roughly the same weapons as on the ships themselves. Planet based lance, macrocannon, and missile silo emplacements.

Planet based weapon systems are individually more powerful than the guns mounted on the ships due to not having size constraints, they're also usually very well shielded as well. Both by being underground and having actual shields. Especially since ships have to go into low orbit to fire on the planet, thus putting themselves in range of the planetary guns. Many planets have truly formidable defenses.

Defensive emplacements like this are usually so strong that it forces attacking forces to land elsewhere on the planet and neutralize the guns before the ships can move into position.

Ships don't need to go into low orbit. The orbit of the planet can be calculated from outside the system or even greater distance, slap some thrusters on a large chunk of rock or metal, and sent directly to where the enemy installation will be in a year's time. There is no friction in space, just fire a torpedo several years in advance.

That presumes, however, that a "destroyed" ship explodes. It's more likely- and is generally the case in 40K, AFAIK- that the ship is "hulked"; the majority of the hull is torn open to vacuum, hemorrhaging air, supplies, and personnel into the void, and completely unable to fight back or even really run away... but otherwise "relatively" intact.

Realistically, a ship is more likely to be "hulked" than explode, but this is more due to the fact that fission plants will be built with substantial safeguards, and fusion reactors have a bit of a built-in safeguard in that it's really really hard to make a fusion plant go into a catastrophic failure mode a la a meltdown*.

40K does seem, like many sci-fi franchises, to have powerplants that have substantially destructive fail-deadly modes... but they also tend to not happen. Using the only source I have on hand, the BFG rules, you roll 2D6 for catastrophic damage; it's only on a 9-12 that the ship actually explodes in a type of fail-deadly mode, while on 2-8 (~64% of all results) the ship is hulked, and just drifts forward a random distance.

It might also be on fire, and receive further damage, depending on if you roll 2-6 (straight drifting) or 7-8 (blazing).

Amusingly enough, it would seem that 40K has safer naval vessel scale power generation systems than Star Trek, given that most warships, when "destroyed" are left as mostly-lifeless hulks, rather than expanding fields of debris.

*Fusion reactors are hard to force into a fail-deadly meltdown on account of the difficulties involved in sustaining the fusion reaction. Containment vessel breaches of the fusion plant is more likely to cause a localized explosion as the plasma explosively decompresses, but will otherwise leave the ship fairly intact.

 Wyzilla wrote:

 Grey Templar wrote:
There are indeed planet based weapons capable of firing on orbiting ships. They're roughly the same weapons as on the ships themselves. Planet based lance, macrocannon, and missile silo emplacements.

Planet based weapon systems are individually more powerful than the guns mounted on the ships due to not having size constraints, they're also usually very well shielded as well. Both by being underground and having actual shields. Especially since ships have to go into low orbit to fire on the planet, thus putting themselves in range of the planetary guns. Many planets have truly formidable defenses.

Defensive emplacements like this are usually so strong that it forces attacking forces to land elsewhere on the planet and neutralize the guns before the ships can move into position.

Ships don't need to go into low orbit. The orbit of the planet can be calculated from outside the system or even greater distance, slap some thrusters on a large chunk of rock or metal, and sent directly to where the enemy installation will be in a year's time. There is no friction in space, just fire a torpedo several years in advance.

This presumes that tactical/strategic consideration can be made that far in advance. Circumstances can and probably will change drastically in that timeframe. It also presumes that the enemy is a complete and utter moron, and won't be able to intercept said ordnance. There's enough evidence in 40K, that low orbit stationkeeping is required for accurate ortillery fire. If you want to just burn an entire world, then sure, higher orbits (or your mentioned torpedo drop) can work just fine... but the Imperium generally seems to hold such measures in reserve as a last resort. Most of the time they seem to want to take planets intact, so that's not necessarily the best of ideas.

It is also the case that, as I mentioned a little earlier, planetary surfaces tend to be a clusterfeth of ridiculous proportions in terms of sensor clutter. Fighting in space could be likened to two preeminent marksman with tripod-mounted, high-accuracy sniper weapons taking aim at each from across a football field.

Doing a space-to-surface fire support mission is like sticking said marksman in the middle of the Amazon. The amount of clutter can make it very difficult to actually pick out things you want to destroy with utter impunity.

 Wyzilla wrote:


Ships don't need to go into low orbit. The orbit of the planet can be calculated from outside the system or even greater distance, slap some thrusters on a large chunk of rock or metal, and sent directly to where the enemy installation will be in a year's time.

You do if you want to actually take the system in a timely manner. And you do realize that if they can hit a ship in orbit that is actually actively trying to avoid being hit they'll definitely be capable of shooting down an asteroid?

There is no friction in space, just fire a torpedo several years in advance.

Actually, that's not entirely true. There is a lot of dust and microscopic particles floating around in space. Plus solar radiation itself actually applies pressure, enough to where actual sails that use Solar wind as a propulsion method are under serious consideration as a method of moving about our solar system. Enough to throw your calculations off by quite a bit.

And again, you're not always going to have years to wait for your torpedo to hit its target. That just gives your opponent a few years to shoot it down.

Whiskey144 wrote:
That presumes, however, that a "destroyed" ship explodes. It's more likely- and is generally the case in 40K, AFAIK- that the ship is "hulked"; the majority of the hull is torn open to vacuum, hemorrhaging air, supplies, and personnel into the void, and completely unable to fight back or even really run away... but otherwise "relatively" intact.

Realistically, a ship is more likely to be "hulked" than explode, but this is more due to the fact that fission plants will be built with substantial safeguards, and fusion reactors have a bit of a built-in safeguard in that it's really really hard to make a fusion plant go into a catastrophic failure mode a la a meltdown*.

40K does seem, like many sci-fi franchises, to have powerplants that have substantially destructive fail-deadly modes... but they also tend to not happen. Using the only source I have on hand, the BFG rules, you roll 2D6 for catastrophic damage; it's only on a 9-12 that the ship actually explodes in a type of fail-deadly mode, while on 2-8 (~64% of all results) the ship is hulked, and just drifts forward a random distance.

It might also be on fire, and receive further damage, depending on if you roll 2-6 (straight drifting) or 7-8 (blazing).

Amusingly enough, it would seem that 40K has safer naval vessel scale power generation systems than Star Trek, given that most warships, when "destroyed" are left as mostly-lifeless hulks, rather than expanding fields of debris.

Except when they do explode, the plasma reactors 40K ships use turns into a miniature star that goes full supernova- dumping radiation, plasma, and shrapnel on everything unfortunate enough to be caught in the very large blast radius.


Automatically Appended Next Post:

 Grey Templar wrote:

 Wyzilla wrote:


Ships don't need to go into low orbit. The orbit of the planet can be calculated from outside the system or even greater distance, slap some thrusters on a large chunk of rock or metal, and sent directly to where the enemy installation will be in a year's time.

You do if you want to actually take the system in a timely manner. And you do realize that if they can hit a ship in orbit that is actually actively trying to avoid being hit they'll definitely be capable of shooting down an asteroid?

Which is why you aim your macrocannons/bombardment cannons and fire continuous volleys to pump rounds down rage and make it impossible to shoot down. Especially when their batteries are typically too large to intercept enemy munitions (especially when if the munition has its own fuel source, it will simply continue to accelerate until a certain point).

Also if you're besieging a planet in 40K, you have all the time in the world unless it's Necrons. Warp Travel is horrifically slow, and reinforcements take ages to actually arrive. Besides depending on the acceleration of the object or sling-shotting it, years can easily turn into months or less.

There is no friction in space, just fire a torpedo several years in advance.

Actually, that's not entirely true. There is a lot of dust and microscopic particles floating around in space. Plus solar radiation itself actually applies pressure, enough to where actual sails that use Solar wind as a propulsion method are under serious consideration as a method of moving about our solar system. Enough to throw your calculations off by quite a bit.

We already are capable of launching probes into asteroids, and are already planning a manned mission to an asteroid. Hitting one with a projectile is child's play. Hitting a planet is even easier. Radiation doesn't knock your projectile off course, gravity wells do. Alternatively if a missile or torpedo has its own fuel source, you can use the gravity of another planet to actually accelerate it by orbiting it several times to serve as a sling-shot.

The besieger dictates the battlefield when assaulting a planet. There should never even be a need to physically engage the enemy or risk getting shot at unless you're being rushed.

And for all the Imperium bitching about how it wants worlds intact, it completely forgets how durable planets are. The Chicxulub Asteroid hit Earth with the energy of a hundred teratons and utterly failed to kill off life on the planet. It experienced a nasty natural disaster, but that isn't even an problem for the Imperium as the average Hive World is WORSE off than Earth during the snowball effect when the atmosphere is filled with dust that blocks out sunlight and causes the temperature to plummet. There is zero reason why the Imperium simply can't fly up to a world, drop an ungodly powerful bomb on it, then just pick off any survivors and set down colonists. They don't care about the health of the biosphere to begin with. Nukes also cause zero permanent damage to a planet. You could drop a hundred H-Bombs with the energy of a hundred megatons each and the planet wouldn't even notice. All that might interfere with continued use is radiation, but it's not like the Imperium cares about its civilians.

 Grey Templar wrote:

 Wyzilla wrote:


Ships don't need to go into low orbit. The orbit of the planet can be calculated from outside the system or even greater distance, slap some thrusters on a large chunk of rock or metal, and sent directly to where the enemy installation will be in a year's time.

You do if you want to actually take the system in a timely manner. And you do realize that if they can hit a ship in orbit that is actually actively trying to avoid being hit they'll definitely be capable of shooting down an asteroid?

There is no friction in space, just fire a torpedo several years in advance.

Actually, that's not entirely true. There is a lot of dust and microscopic particles floating around in space. Plus solar radiation itself actually applies pressure, enough to where actual sails that use Solar wind as a propulsion method are under serious consideration as a method of moving about our solar system. Enough to throw your calculations off by quite a bit.

And again, you're not always going to have years to wait for your torpedo to hit its target. That just gives your opponent a few years to shoot it down.

In regards to solar sails, photon pressure is unfortunately very negligible under most conditions... as in, you need exceedingly (read: impractically) light platforms in order for it to have a measurable effect. Dust/microscopic particles can also be considered negligible as well; Voyager hasn't been affected by such variables, and it was launched with what, 1960s/1970s era hardware?

Pretty sure that 40K, for all its "technological decline", can still do just as well.

But yes, time-on-target is a major, unavoidable issue.

 Wyzilla wrote:
Except when they do explode, the plasma reactors 40K ships use turns into a miniature star that goes full supernova- dumping radiation, plasma, and shrapnel on everything unfortunate enough to be caught in the very large blast radius.

True that may be, but the likelihood of such a catastrophic explosion (or an even worse warp engine breach) is outweighed by the statistical likelihood of the ship simply being left adrift, possibly burning. AFAIK in the fluff- and I'm a bit rusty on this I'll admit- ships rarely explode, and mostly end up hulked. Even taking the BFG rules as absolutely accurate*, it's only around 36% of the time (IE, a tad over 1 out of 3) that such catastrophic results occur.

*It's my opinion that the BFG rules have a higher incidence of catastrophic explosions because exploding spaceships are pretty cool for wargaming purposes.

 Wyzilla wrote:
And for all the Imperium bitching about how it wants worlds intact, it completely forgets how durable planets are. The Chicxulub Asteroid hit Earth with the energy of a hundred teratons and utterly failed to kill off life on the planet. It experienced a nasty natural disaster, but that isn't even an problem for the Imperium as the average Hive World is WORSE off than Earth during the snowball effect when the atmosphere is filled with dust that blocks out sunlight and causes the temperature to plummet. There is zero reason why the Imperium simply can't fly up to a world, drop an ungodly powerful bomb on it, then just pick off any survivors and set down colonists. They don't care about the health of the biosphere to begin with. Nukes also cause zero permanent damage to a planet. You could drop a hundred H-Bombs with the energy of a hundred megatons each and the planet wouldn't even notice. All that might interfere with continued use is radiation, but it's not like the Imperium cares about its civilians.

It's not about personnel or biospheres, it's about the man-made infrastructure. Most of the time, the Imperium is either conquering uninhabited balls of dirt, of fighting wars of defense/reconquest on worlds that they already have substantial infrastructure on. It is a really bad idea to just bomb those worlds into oblivion and then mop up whatever's left alive, because doing so destroys most of the reason that said ball of dirt is desirable in the first place: all the industrial infrastructure that's present.

Yes yes, you can argue that they'll just have to rebuild it anyways after fighting a bloody battle through it all, but the point remains that it's generally easier to fix it than it is to start from scratch.

There's all kinds of planet-based defenses that can cripple or destroy a ship in orbit. Also, capital ships in this setting are rarely fast-moving vessels. The various space-battle games of the franchise are based around naval combat scenarios, not dog-fights between kilometers-long vessels.

 Psienesis wrote:
Also, capital ships in this setting are rarely fast-moving vessels.

Only relative to other sci-fi universes.

Given that BFG had a rough time equivalent that 1 turn = 5 minutes, even the slowest capital ship with a speed of 20cm was traveling at a speed of roughly 240,000 kph. That's 2% of the speed of light if my math is correct.

Thats fast enough to where you start having time distortions due to relativity.

 Psienesis wrote:
There's all kinds of planet-based defenses that can cripple or destroy a ship in orbit. Also, capital ships in this setting are rarely fast-moving vessels. The various space-battle games of the franchise are based around naval combat scenarios, not dog-fights between kilometers-long vessels.

Capital ships move EXCEPTIONALLY fast, as do all naval ships. They just can't bank for gak. But ships move at a fraction of C. IE stupidly fast.

Oddly enough, 40k is much more realistic in this regard than other universes like Star Trek.

In order to have engines worth anything, you need a very large ship. Bigger engines means faster ships, despite the increased mass the economies of scale work out in favor of a larger ship. Smaller is only faster in atmospheres where there is a massive amount of friction. Large mass does of course mean you can't change direction very easily. Inertia is a heartless b-word.

Of course that gets broken by the inclusion of fighter craft as a practical method of fighting, but we couldn't expect reality to hold for long.

Like many things, small parasite "fighters" being viable or not is typically dependent on the going-in assumptions that are made regarding technical capabilities.

Small fightercraft work in 40K and Star Wars, but not Star Trek.

 Grey Templar wrote:
Oddly enough, 40k is much more realistic in this regard than other universes like Star Trek.

In order to have engines worth anything, you need a very large ship. Bigger engines means faster ships, despite the increased mass the economies of scale work out in favor of a larger ship. Smaller is only faster in atmospheres where there is a massive amount of friction. Large mass does of course mean you can't change direction very easily. Inertia is a heartless b-word.

Of course that gets broken by the inclusion of fighter craft as a practical method of fighting, but we couldn't expect reality to hold for long.

This brings up some interesting points too:

-due to actual engineering principles, some powerplant/engine types actually have a minimum practical size. We see this very obviously in 40K as actual warships are the only things that commonly zip around with warp motors; IE, it's not practical to make Warp-capable fighters
-bigger ships can not only carry larger engines, but also larger remass/fuel reserves. The catch is that this kicks off a Red Queen's Race in that in order to haul all of that around you need even more engine power and remass reserve, which means you get even bigger ships, etc etc

As a point of interesting trivia, one of the best examples of the idiocy of Star Trek naval design in reference to actual warships, is the Defiant vs the Galaxy; they're actually comparable in firepower, but the Defiant is like a quarter to a third the size of a Galaxy, if that. It mostly comes from the fact that the Defiants stripped out all the useless gak that a Galaxy had to carry around- civilian quarters, excessively large aquariums, the numerous (and also excessively large) holodecks, the presence of a large and well-equipped bar, things like that. The Defiant is all warship, instead of warship-science ship-explorer ship-whatever other useless things we can shove into it ship.

The Defiant also was sensibly shaped, unlike the stupid saucer design. AKA: Shoot the engines, Sever the little spine holding the engines to the saucer, etc...

The Galaxy-class was a science vessel. The Defiance class was a warship.

The scale given by Andy Chambers, who designed BFG, was 1cm= 1,000 km and the time scale a telescoping one with 1 turn = 1 hour at long ranges (like 60cm) and 1 turn = 15 minutes at short ranges (like 15cm).
( http://www.wolfedengames.com/battlefleetgothic/scale.htm )

An Imperial cruiser has a Speed characteristic of 20 cm and maximum move of 44cm on All Ahead Full special orders. That means at the absolute max that is 20,000 km in 15 minutes or 80,000 kph and 44,000 km in 15 minutes or 176,000 kph on All Ahead Full orders.

As for planetary defenses, with reference to the BFG rulebook p. 146, the average planetary defense laser silo packs almost as much firepower as the broadside of a Gothic cruiser, with greater range than the Gothic. Likewise, the average planetary defense missile silo has the launch capacity of a full cruiser, and the average planetary defense air base has enough short range aerospace fighters and bombers to match a Dictator cruiser.

From the old GW Armageddon 3 website archived at http://web.archive.org/web/20010820235454/www.armageddon3.com/English/Campaign/BFG/BFGmap.html

we can see the defenses of each hive on Armageddon comprised at least 4 air bases, 8 missile silos, and 8 laser silos. That kind of firepower would be enough to shred your average navy frigate, and even your average cruiser, if they tried to bombard the hive. Even if one takes Armageddon to be a more heavily defended than usual hive world, it still gives a rough gauge of the defenses a typical hive might have, which still is likely to overpower most spaceships.

some of the defense weapons are massive, well capable of taking out warships in orbit with ease. and one torpedo alone in a critical hit can cause massive damage.

In storm of iron the laser and torpedo batteries where deemed a threat enough that 3 or even 6 months was spent locating and tagging them for bombardment.

and they may not fire on the first ship, they might wait hidden till you try to land your transports, big, vulnerable and lacking armour. then boom there goes x % of your army in a single shot.

a titan is pretty invunrable, but its big transport ship is a juicey target for a oribital defense weapon laying in wait beneath the sand.

Ground based weapons have the advantages of, substantially more support systems allowing for greater power of shots, and greater firing rate, due to heat sinks and as mentioned power plants.

They can be 'more durable' due to being able to be based mostly underground and allowing again for more and more powerful shielding.

Downsides are mobility, they have none, that have a limited firing arc, and usually depend upon planetary rotation (if any) to target a ship in orbit.

If a world was bristled with them, like nearly every 20 square miles there is one at least, it would be a nightmare to invade, arguable not worth it. A planet that heavily defended would probably not be able to support anything worth protecting that much though due to the space they would take up. I imagine it is a sound strategy for orbiting moons though to be so heavily armed on worlds of extreme strategic value.


Automatically Appended Next Post:

 jhe90 wrote:
some of the defense weapons are massive, well capable of taking out warships in orbit with ease. and one torpedo alone in a critical hit can cause massive damage.

In storm of iron the laser and torpedo batteries where deemed a threat enough that 3 or even 6 months was spent locating and tagging them for bombardment.

and they may not fire on the first ship, they might wait hidden till you try to land your transports, big, vulnerable and lacking armour. then boom there goes x % of your army in a single shot.

a titan is pretty invunrable, but its big transport ship is a juicey target for a oribital defense weapon laying in wait beneath the sand.

Yeah, if there is a titan transport in orbit, and you are aware the titans have currently not landed, and you estimate you can take the whole fleet in an attack. You take out the ships, purposely cripple the titan ship, then take your time boarding and sweeping the titan ship. Why destroy the titans or any valuable war machines for that matter when you have a chance of capturing them.

Providing they are imperial titans, and the world is imperial. Obviously no good taking gargents, or trying to take elder titans, or daemonicly infested ones.

With the talk of dropping rocks on planets, here is an oldie but goody:

Rocks are NOT ‘free’, citizen.
Firstly, you must manoeuvre the Emperor’s naval vessel within the asteroid belt, almost assuredly sustaining damage to the Emperor’s ship’s paint from micrometeoroids, while expending the Emperor’s fuel.
Then the Tech Priests must inspect the rock in question to ascertain its worthiness to do the Emperor’s bidding. Should it pass muster, the Emperor’s Servitors must use the Emperor’s auto-scrapers and melta-cutters to prepare the potential ordinance for movement. Finally, the Tech Priests finished, the Emperor’s officers may begin manoeuvring the Emperor’s warship to abut the asteroid at the prepared face (expending yet more of the Emperor’s fuel), and then begin boosting the stone towards the offensive planet.
After a few days of expending a prodigious amount of the Emperor’s fuel to accelerate the asteroid into an orbit more fitting to the Emperor’s desires, the Emperor’s ship may then return to the planet via superluminous warp travel and await the arrival of the stone, still many weeks (or months) away.
After twiddling away the Emperor’s time and eating the Emperor’s food in the wasteful pursuit of making sure that the Emperor’s enemies do not launch a deflection mission, they may finally watch the ordinance impact the planet (assuming that the Emperor’s ship does not need to attempt any last-minute course correction upon the rock, using yet more of the Emperor’s fuel).

Given a typical (class Bravo-CVII) system, we have the following:
Two months, O&M, Titan class warship: 4.2 Million Imperials
Two months, rations, crew of same: 0.2 MI
Two months, Tech Priest pastor: 1.7 MI
Two months, Servitor parish: 0.3 MI
Paint, Titan class warship: 2.5 MI
Dihydrogen peroxide fuel: 0.9 MI
Total: 9.8 MI

Contrasted with the following:
5 warheads, magna-melta: 2.5 MI
One day, O&M, Titan class warship: 0.3 MI
One day, rations, crew of same: 0.0 MI
Dihydrogen peroxide fuel: 0.1 MI
Total: 2.9 MI

Given the same result with under one third of the cost, the Emperor will have saved a massive amount of His most sacred money and almost a full month of time, during which His warship may be bombarding an entirely different planet.
The Emperor, through this – His Office of Imperial Outlays – hereby orders you to attend one (1) week of therapeutic accountancy training/penance. Please report to Areicon IV, Imperial City, Administratum Building CXXI, Room 1456, where you are to sit in the BLUE chair.

For the Emperor,
Bursarius Tenathis,
Purser Level XI,
Imperial Office of Outlays.

The one thing a lot of sci fi fails to get across is the sheer vastness and scale of space (along with ships flying if there is an atmosphere)

In a lot of scifi (40k too) ships seem to hold a completely static orbit over a planet.

With such woefully inaccurate distances, static orbits and flying through an atmosphere whilst in space then it's very easy for ground facilities to own the gak out of naval vessels.

One does not simply shoot straight up (unless it's lances I guess)

 Psienesis wrote:
The Galaxy-class was a science vessel. The Defiance class was a warship.

Science vessels don't have guns. The Galaxy was the leading design of the Federation fleet for a long time, and there's enough evidence to indicate that it was also produced in much larger numbers than the Defiant ever was (IIRC there were 5-6 Defiants built, of which at least two were lost).

endlesswaltz123 wrote:
Ground based weapons have the advantages of, substantially more support systems allowing for greater power of shots, and greater firing rate, due to heat sinks and as mentioned power plants.

They can be 'more durable' due to being able to be based mostly underground and allowing again for more and more powerful shielding.

Downsides are mobility, they have none, that have a limited firing arc, and usually depend upon planetary rotation (if any) to target a ship in orbit.

If a world was bristled with them, like nearly every 20 square miles there is one at least, it would be a nightmare to invade, arguable not worth it. A planet that heavily defended would probably not be able to support anything worth protecting that much though due to the space they would take up. I imagine it is a sound strategy for orbiting moons though to be so heavily armed on worlds of extreme strategic value.

In 40K, yes, mobility is a notable limitation. Fire arc isn't actually a big deal, as it's generally the case that any defensive battery has a sufficient "field of fire" to cover whatever it's set up to protect. It's also unlikely that a world would have that many spread out in such a fashion- that's a lot of space wasted on doing nothing but protecting empty and useless territory.

The logical methods are generally that your big infrastructure tends to get the defensive emplacements; large cities/hives, capital buildings, that sort of thing.

Though natural satellites being turned into veritable fortresses does have some supporting evidence- IIRC the Moon in 40K is actually armor plated in its entirety!

Johnson & The Juice Crew wrote:
The one thing a lot of sci fi fails to get across is the sheer vastness and scale of space (along with ships flying if there is an atmosphere)

In a lot of scifi (40k too) ships seem to hold a completely static orbit over a planet.

With such woefully inaccurate distances, static orbits and flying through an atmosphere whilst in space then it's very easy for ground facilities to own the gak out of naval vessels.

One does not simply shoot straight up (unless it's lances I guess)

Define "static orbit". It's entirely possible that a ship could be in a geosync orbit, or just using some kind of apogee motor to keep station at a lower orbit. There's also the fact that you could adjust your orbit so that you have extended periods over a target area. While that usually means that you'd have equally extended periods over non-target areas, it's entirely possible to dynamically adjust an orbit track to swing around non-target zones faster and then loiter over target areas for extended durations.

And again, surface emplacements have the benefit of being in an enormous clusterfeth of ground clutter that it can use as concealment, at the very least preventing accurate bombardment from higher orbits.

That's actually something that nobody really thinks about- ortillery accuracy is less likely to be an issue of "can my weapon system shoot the wings off of a fly", and more of a "can my targeting controls aim my gun well enough to shoot the wings off of a fly". So it's very likely that 40K warships are actually able to accurately bombard things from higher orbits, base purely on mechanical weapon limitations. The issue is that the clusterfeth ground clutter that is a planetary surface will generally prevent them from actually picking out the juicy targets that they want to asplode to tiny pieces.

When the batteries are concentrated though, they are very vulnerable to an army landing out of their firing arc and taking or destroying said batteries. Hence why I said if they were more spread out, they would be a nightmare.

There are evidently massive pro's and cons for either, and I would go with your option also. But those pesky marines are going to storm up fast to an unguarded area and drop everything as close as possible with supporting vehicles and take it in one fell swoop.

Having said that, marines are also mental enough to attack the cities, batteries or not, due to their method of invasion, being able to fast drop straight on to the defence batteries command location, holding it long enough for other imperial forces to capture the actual batteries, and the weapons on their ships being quite nasty at bombarding planets themselves, and generally causing carnage as a smoke screen for said marines dropping down.

I wouldn't call it "mental" for Marines to do that, as it's always been part of their mission profile to be capable of that. To that end, they've also generally been equipped with much better-protected warships.

It's also the case that it's a lot easier to defend a fortress from a ground assault than it is to cover a planet with anti-orbital batteries... though that does assume that anti-orbital batteries are exponentially more expensive than a traditional fortress and defending army.

Also, it does lead to a question, if a weapon is powerful enough to send a projectile of energy or of matter into high orbit with enough force once there to damage an orbiting star cruiser, what would that do to the are surrounding it, and if the cruiser is in a geosynchronous orbit, what do they do about the dangers posed by falling debris?

Many cities that have orbital defenses are also equipped with void shield generators that cover the city.

If they don't? It's the Imperium, life is cheap.

I would imagine that a fleets priority would be to destroy any static defences capable of causing damage to them from a distance before entering a static or geosyncranous orbit.

Realistically a solid slug weapon launched at an installation would be difficult to intercept but would be able to be targeted at a predictable point.

At the distances we are potentially talking about the combatants could be looking at time delayed images of each other unless they have some kind of FTL sensors. A planet mounted weapon would be easy to target because its location would be entirely predictable, hitting a ship based on an image of where it was a few minutes or even hours ago could be impossible.

 GKTiberius wrote:
Also, it does lead to a question, if a weapon is powerful enough to send a projectile of energy or of matter into high orbit with enough force once there to damage an orbiting star cruiser, what would that do to the are surrounding it, and if the cruiser is in a geosynchronous orbit, what do they do about the dangers posed by falling debris?

Probably nothing; debris is either a non-issue due to void shielding, or because the majority of the debris will either normalize into an orbital track or be flung into deep space. Geosync orbits are also high enough up that it's more likely for debris to spall off into deep space anyways.

 Ugly Green Trog wrote:
I would imagine that a fleets priority would be to destroy any static defences capable of causing damage to them from a distance before entering a static or geosyncranous orbit.

Realistically a solid slug weapon launched at an installation would be difficult to intercept but would be able to be targeted at a predictable point.

At the distances we are potentially talking about the combatants could be looking at time delayed images of each other unless they have some kind of FTL sensors. A planet mounted weapon would be easy to target because its location would be entirely predictable, hitting a ship based on an image of where it was a few minutes or even hours ago could be impossible.

Not necessarily; there's more than a few examples of battlegroups landing ground forces from outside the field of fire of the anti-orbital defenses, rather than trying to take on the defenses "head to head". There's also the issue that while surface batteries in 40K tend to be big and visible, that's not a hard-and-fast rule. Also, in the case of 40K, the surface defenses either boast enormous amounts of old-fashioned "put dirt between me and the bullets" shielding, or they boast void shields that can rival or exceed that of an Imperial cruiser.

And, again, positive identification of surface emplacements, especially at interplanetary distance, is not a given. Surface clutter is a big deal for modern aircraft. Spacecraft are going to have the same problem, only turned up to 11 because they'll be looking through all the cloud layers as well. It's theoretically possible to dump slugs into a planet from across a star system, and put them very accurately down... but the targeting and aiming apparatus* may limit your accuracy substantially. By which I mean your sensor systems probably aren't going to be able to penetrate the surface clutter and cloud layers with perfect accuracy every single time, and the method you use to adjust point-of-aim may have sufficient mechanical imperfection/error to prevent you from taking advantage of such precision sensor apparatus anyways.

*I separate "targeting" and "aiming" because they are technically two different devices; targeting refers to the sensor systems which detect, identify, and then maintain "lock" on a target object, while aiming refers to the mechanical systems which adjust the weapon system so that any shots fired are "on target".

As an example of surface weapons which are nearly undetectable, there's:

-laser subs
-anti-orbital missile subs
-anti-orbital missile trucks

In the case of the subs, they can easily surface, fire, and submerge before counter-battery fire can be brought to bear. Depending on the laser/missile system design, it's also entirely possible that the sub can fire while submerged, achieving total surprise and cutting off effective counterfire via using ocean water and atmosphere as a shield.

In the case of truck systems, there's mobile ICBM-launchers as the basis; it's a truck carrying one or more anti-orbital missile systems, which means that it's mobile, can displace/emplace as needed, easily concealable (compared to a large laser/missile installation at least), and also not worth scragging once it's fired.

In 40k lore the Fang and other notable locations have massive lasers that can strike ships in low orbit within line of sight of the installations.

In the Fangs case the generators and emitters are deep underground and the barrels are shafts cut into the mountains.

In Space Marine giant macro cannons shooting shells larger in caliber then the marines are tall are shot at ships in the upper atmosphere. The installation survived getting hit by a Rok.

Whiskey144 wrote:

 Psienesis wrote:
The Galaxy-class was a science vessel. The Defiance class was a warship.

Science vessels don't have guns. The Galaxy was the leading design of the Federation fleet for a long time, and there's enough evidence to indicate that it was also produced in much larger numbers than the Defiant ever was (IIRC there were 5-6 Defiants built, of which at least two were lost).

Even the original NCC-1701 was armed, and it was certainly a science vessel, "Its five-year mission to seek out new life and new civilizations, to boldly go where no man had gone before", as the line goes. The first (as far as the TV show is concerned) was "designed for long duration missions with minimal outside support and are best known for their celebrated missions of galactic exploration and diplomacy which typically lasted up to five years."

The Galaxy-class is also a science vessel, rather than a warship. In fact, this entire class of vessel is given the notation of "explorer", rather than something like dreadnought.

Most Imperial planets have defense lasers and surface-to-orbit missile silos. These can feth up warships of any class.

Whiskey144 wrote:

 Psienesis wrote:
The Galaxy-class was a science vessel. The Defiance class was a warship.

Science vessels don't have guns. The Galaxy was the leading design of the Federation fleet for a long time, and there's enough evidence to indicate that it was also produced in much larger numbers than the Defiant ever was (IIRC there were 5-6 Defiants built, of which at least two were lost).

The classification of the Galaxy as a Science vessel was just a PR stunt. Truthfully, the Galaxy was a dual purpose vessel. It had all the equipment necessary to serve as both a ship of the line and as a research vessel. And it was always intended to be the workhorse of the fleet.

Federation politics made making actual warships politically undesirable. So instead they made "science" vessels that were heavily armed, but not as much as their size would have allowed.

Hence other faction's warships being much smaller than the Galaxy class, but often being more maneuverable and heavily armed.

Historically, most vessels were armed in some fashion. Non-military vessels being unarmed is a very recent development. Private citizens often boasted stronger warships than some actual navy ships, hence why Privateers were always getting hired. And even podunk merchant ships always had a few cannon to protect from pirates.

 Grey Templar wrote:
Historically, most vessels were armed in some fashion. Non-military vessels being unarmed is a very recent development. Private citizens often boasted stronger warships than some actual navy ships, hence why Privateers were always getting hired. And even podunk merchant ships always had a few cannon to protect from pirates.

Quite true. As I recall long-range merchantmen like the East Indies ships were built big, tough and well armed to keep pirates, privateers and hostile naval ships at bay. Not as heavily armed as a similar size ship of the line but enough to make the ships likely to be encountered on the long journey think twice about engaging.

Spetulhu wrote:

 Grey Templar wrote:
Historically, most vessels were armed in some fashion. Non-military vessels being unarmed is a very recent development. Private citizens often boasted stronger warships than some actual navy ships, hence why Privateers were always getting hired. And even podunk merchant ships always had a few cannon to protect from pirates.

Quite true. As I recall long-range merchantmen like the East Indies ships were built big, tough and well armed to keep pirates, privateers and hostile naval ships at bay. Not as heavily armed as a similar size ship of the line but enough to make the ships likely to be encountered on the long journey think twice about engaging.

Yup, and they were certainly far better armed than any pirates they would encounter in Asia.

As I recall the first battles of the opium war were fought entirely by merchant ships. By the time actual warships arrived the Chinese had already been beaten 6 shades of black and blue on the ocean.

 Psienesis wrote:
Even the original NCC-1701 was armed, and it was certainly a science vessel, "Its five-year mission to seek out new life and new civilizations, to boldly go where no man had gone before", as the line goes. The first (as far as the TV show is concerned) was "designed for long duration missions with minimal outside support and are best known for their celebrated missions of galactic exploration and diplomacy which typically lasted up to five years."

The Galaxy-class is also a science vessel, rather than a warship. In fact, this entire class of vessel is given the notation of "explorer", rather than something like dreadnought.

The Constitution-class was also generally classified as a "Heavy Cruiser", not a science vessel. While a 5-year mission was typically exploratory in nature, it must also be remembered that the Connies were intended as the primary ship of the line of the Feddie fleet.

Also, as mentioned, the Galaxy was sold as a "science" or "explorer" ship because Starfleet and the Federation as a whole considers a pure warship to be an uncivilized and barbaric idea, despite the fact that they are surrounded by expansionist, imperialist neighbors. There's a few people, I'm sure, who would call that the height of arrogance and stupidity both.

 Grey Templar wrote:
Historically, most vessels were armed in some fashion. Non-military vessels being unarmed is a very recent development. Private citizens often boasted stronger warships than some actual navy ships, hence why Privateers were always getting hired. And even podunk merchant ships always had a few cannon to protect from pirates.

While true historically, it's often a scifi convention that research/science/exploratory vessels are totally unarmed. This isn't an unreasonable approach either; because of the severe limitations on total mass and useful payload that a spacecraft would actually have to face, it's very logical and economic to omit any kind of weapon system for a platform that is intended to never get into a fight.

There's also the issue that a science/R&D/explorer vessel could be built such that it has very high performance engines, and substantial remass reserves in particular. Doesn't much matter if your opposition can catch you in a sprint, if they can't last the marathon, after all. Substantial remass/fuel reserve is, in fact, the most likely solution to the "will I get attacked" problem. Anything looks remotely suspicious? Just leave- you've got the remass to outrun the suspicious thing, and then come back to whatever interestingly dull rock you were looking at. Oh, and you'll still have plenty to go home with too!

That was always my biggest beef with Star Trek. Their moronic pacifism. And the ''morally superior'' self absorption.

 Grey Templar wrote:
That was always my biggest beef with Star Trek. Their moronic pacifism. And the ''morally superior'' self absorption.

If viewed withing the cultural context of the show in the 1960's in america, the idea of pacificsm and alturistic scientific exploration wasnt moronic or naieve, it was an outright rejection of the hawkish nature of the american foreign policy at the time. This show came out at the height of the Vietnam war, so a show about space wars would have probably tanked even harder than the original series did . It allowed a degree of escapism.

However the cultural shift of the 1970's combined with the nostalgia of childhood made it popular again, and as time went on, the show got more and more conflict oriented. TNG, and Voyager specifically are almost exclusively driven by conflict. This shift is also why star wars was so popular.

Without the altruism and the pacifism the view wouldn't get a sense of moral superiority of the protagonists. Without that moral superiority and a clear cut good versus bad narrative we would have future grimdark, and that isn't a setting we were culturally ready for.

We live in a society that is a direct result of these clear cut good versus evil tropes which is why complex, mufti layered characters and story lines are so refreshing to us. IF you transplanted the same narrative to 1968 propel would think you are some sort of strange warmongering hawk.

Cultural context is super important. Imagine the reaction in america if a movie came out depicting a terrorist attack on a western country as a positive and deserved outcome. It would be reviled now, but in 50 years, it may be a topic people consider entertaining, once the cultural impact of that concept lessens to the point it isn't a major factor in microscopic or macroscopic cultural discussions.

 GKTiberius wrote:

 Grey Templar wrote:
That was always my biggest beef with Star Trek. Their moronic pacifism. And the ''morally superior'' self absorption.

If viewed withing the cultural context of the show in the 1960's in america, the idea of pacificsm and alturistic scientific exploration wasnt moronic or naieve, it was an outright rejection of the hawkish nature of the american foreign policy at the time. This show came out at the height of the Vietnam war, so a show about space wars would have probably tanked even harder than the original series did . It allowed a degree of escapism.

However the cultural shift of the 1970's combined with the nostalgia of childhood made it popular again, and as time went on, the show got more and more conflict oriented. TNG, and Voyager specifically are almost exclusively driven by conflict. This shift is also why star wars was so popular.

Without the altruism and the pacifism the view wouldn't get a sense of moral superiority of the protagonists. Without that moral superiority and a clear cut good versus bad narrative we would have future grimdark, and that isn't a setting we were culturally ready for.

We live in a society that is a direct result of these clear cut good versus evil tropes which is why complex, mufti layered characters and story lines are so refreshing to us. IF you transplanted the same narrative to 1968 propel would think you are some sort of strange warmongering hawk.

Cultural context is super important. Imagine the reaction in america if a movie came out depicting a terrorist attack on a western country as a positive and deserved outcome. It would be reviled now, but in 50 years, it may be a topic people consider entertaining, once the cultural impact of that concept lessens to the point it isn't a major factor in microscopic or macroscopic cultural discussions.

I'm well aware of the context. It was still moronic and naive.

Besides, the smugness and preachy moral superiority didn't really come to the front till Next Generation. Well after the Vietnam war. The original series was less preachy.

I still like NG better as the superior show.

TNG had Picard, what I found most stupid there was that the senior officers and NCO's always were beaming down and solving crisis. But I'm a Gater, not a Trekkie.

SG>ST for sure.

[youtube]

 Grey Templar wrote:
SG>ST for sure.

Nice.

 Beaviz81 wrote:
TNG had Picard, what I found most stupid there was that the senior officers and NCO's always were beaming down and solving crisis. But I'm a Gater, not a Trekkie.

I am more of a SG fan myself, but flinging a Colonel in a new and unknown doesn't seem smart, either. Might make more sense during late episdoe, where having the weight of the rank be useful for represneting the US army. Just like its kinda weird having such a young Lt-Colonel (in Atlantis)

 Bobthehero wrote:

 Beaviz81 wrote:
TNG had Picard, what I found most stupid there was that the senior officers and NCO's always were beaming down and solving crisis. But I'm a Gater, not a Trekkie.

I am more of a SG fan myself, but flinging a Colonel in a new and unknown doesn't seem smart, either. Might make more sense during late episdoe, where having the weight of the rank be useful for represneting the US army. Just like its kinda weird having such a young Lt-Colonel (in Atlantis)

I always thought that to be Hollywood wanting someone beautiful there, and ain't the minimum age like 29? It can happen, but not that often.

For a lieutenant-colonel? Minimum 15 years cumulative time-in-service, so absolute youngest one could be is 32 (assuming they enlisted at 17 with a parent's authorization and then went green-to-gold).

Wasn't his rank a result of politics? IIRC the military wanted to replace him with someone of appropriate rank but Weir said no, they eventually relented and gave him appropriate rank instead.

 GKTiberius wrote:

 Grey Templar wrote:
That was always my biggest beef with Star Trek. Their moronic pacifism. And the ''morally superior'' self absorption.

If viewed withing the cultural context of the show in the 1960's in america, the idea of pacificsm and alturistic scientific exploration wasnt moronic or naieve, it was an outright rejection of the hawkish nature of the american foreign policy at the time. This show came out at the height of the Vietnam war, so a show about space wars would have probably tanked even harder than the original series did . It allowed a degree of escapism.

However the cultural shift of the 1970's combined with the nostalgia of childhood made it popular again, and as time went on, the show got more and more conflict oriented. TNG, and Voyager specifically are almost exclusively driven by conflict. This shift is also why star wars was so popular.

Without the altruism and the pacifism the view wouldn't get a sense of moral superiority of the protagonists. Without that moral superiority and a clear cut good versus bad narrative we would have future grimdark, and that isn't a setting we were culturally ready for.

We live in a society that is a direct result of these clear cut good versus evil tropes which is why complex, mufti layered characters and story lines are so refreshing to us. IF you transplanted the same narrative to 1968 propel would think you are some sort of strange warmongering hawk.

Cultural context is super important. Imagine the reaction in america if a movie came out depicting a terrorist attack on a western country as a positive and deserved outcome. It would be reviled now, but in 50 years, it may be a topic people consider entertaining, once the cultural impact of that concept lessens to the point it isn't a major factor in microscopic or macroscopic cultural discussions.

except the smug pacifism isn't a product of the original series. but rather more a thing of TNG

TNG was Roddenberry's magnum opus. He was the driving force behind the radical socialism and pacifism, but that aside. The concept of the show wouldn't work if the federation was warlike and aggressive. I mean, don't get me wrong, firefly and other future space shows where the protagonists are a aggressive are awesome, but if the federation was imperialistic and aggressive, the show would have a hard time painting the protagonists in a positive light. Self advancement and preservation through aggression are permissible as long as it is a small group trying to make it in an uncaring universe. If a government or organization does it they are seen as power hungry and imperialist. Which, due to post wwII norms are seen as negative qualities for entities on that level. So in order to have a federation, they would have to be peaceful and benign to be relatable and likable to mass audiences.

They didn't need to be aggressive. Just not total wussies.

The thing is excitement, and not having to pay a bevy of actors top wage. I mean you could have a strike-team and their bosses doing stuff, but seeing Picard and company sitting on their bums twiddling thumbs while some grunts were down there in case they had to fire guns and such wouldn't be exciting. While the strike-team would mean they had to develop a host of new characters for every actor.

SomeRandomEvilGuy wrote:
Planetary Defence Lasers are capable of doing so. I think in Storm of Iron there's a planetary torpedo defence installation too. No real reason (other than not STC allowed) that any ship based Imperial weapon could not be based on a planet. I suspect it would take multiple shots from Imperial weaponry though. They'd have to penetrate the void shields of the vessel first.

Actually there are several reasons why they would not be possible.

First you ahve the planets gravity. It takes a huge rocket to get even a small package into orbit, then once in orbit it takes more power to get a speed going that will get your to a cruiser. Ground based guns, rockets or torpedos would have to be an order of magnitude larger to achive the same power as an orbital weapon.

The second is the atmosphere. A laser would lose half it's power going through the atmophere of the planet getting to space. If the laser is powerful enough to do damage to a space craft, it is going to do damage to the planet as well.

Third is recoil and gravity together. Aiming a weightless gun in space isnt an issue, just turn it to the desired direction and then fire. When firing the recoil is absorbed into the ship and gives the ship a momenet. Then the ships thrusters can slowly correct it.
On a planet, holding up the massive guns would be difficult, moving them around would be more difficult. Dealing with the recoil would shock and destroy those systems. This is why naval guns were larger than land based guns since the late 19th century. It was easier to just bolt to the ship and let the water take care of the recoil than build a massive steel emplacement that could contain the force.

 GKTiberius wrote:
...if the cruiser is in a geosynchronous orbit, what do they do about the dangers posed by falling debris?

Falling debris? That's not really how orbits work. Blow up an object in orbit and you have a cloud of smaller objects in very similar orbits. Unless the original orbit passed very close to the surface (which is never the case with a geosynchronous orbit) the fragments aren't going to hit the planet.

Orbital velocities are measured in thousands of meters per second. Fragments from an explosion are going to leave at maybe hundreds of metres a second at most. There simply isn't enough change in velocity to make a big difference.

Thinking of something in an orbit as flying or floating isn't accurate. It's falling. It's falling straight towards the planet (or whatever) as fast as it possibly can. The reason it doesn't hit the surface isn't because it's being lifted up, it's because it's moving sideways so fast that it keeps missing the planet it is falling towards. To change things so that it hits the planet, you don't stop it's lift, because there is no lift. You have to stop it from moving sideways and the speed at which it is going sideways makes bullets seem like they are moving at walking pace. You would need to hit the ship with an equal sized ship going just as fast in the opposite direction to make it stop and fall out of the sky.

it's because it's moving sideways so fast that it keeps missing the planet it is falling towards

That's an interesting way to put it.

Anyway, eventually the debris of the ship would make planetfall. There is always some drag on the ship while it is in orbit. So without constant corrections and firing the thrusters it will fall even without getting hit with anything. Blowing it up will proly cause it to enter the atmo a lot sooner, therefor causing more drag, slowing the velocity normal to the gravitational pull and leading the debris "falling" faster.

Unless you were able to hit it with something "heavy" (in the sense of having a large mass) and knock it further way from the planet and break orbit. Even so, it wouldnt hit the same place it was in orbit over, it would hit "behind" it (relative to the rotation of the planet) and a bunch of it would burn up (depending on the atm) and hopefully the rest you could mop up with smaller guns

or..................

send a rag tag group of astronauts/scientists/sassy models/and a guy with a troubled past, to stop anything from crashing into the planet by attaching some sort of nuke or other-such equally unbelivable plan to redirect the ships hull into the sun or something. Failing that, a group of over the hill retired astronauts, I have seen that work too, cant remember where, but it has to be based on fact. At worst you can laugh at the hijinks as they try to get along and save the world, but more importantly discover something else......themselves.......

 Grey Templar wrote:
They didn't need to be aggressive. Just not total wussies.

Well, their ships were heavily armed and even the Startfleet pacificsts knew war and conflict. It's just that they didn't like the thought of building an outright warship when their official policy was founded on peaceful compromise and cooperation. If you want true stupidity in Startrek then ask about the exploding consoles and why basic bodyarmour (even if it is just to stop some savages knive...or a thrown rock), helmets and anything more useful than the equivalent of a bolt action rifle are apparently no longer possible in the 24. century.

taurising wrote:

it's because it's moving sideways so fast that it keeps missing the planet it is falling towards

That's an interesting way to put it.

Anyway, eventually the debris of the ship would make planetfall. There is always some drag on the ship while it is in orbit. So without constant corrections and firing the thrusters it will fall even without getting hit with anything. Blowing it up will proly cause it to enter the atmo a lot sooner, therefor causing more drag, slowing the velocity normal to the gravitational pull and leading the debris "falling" faster.

Unless you were able to hit it with something "heavy" (in the sense of having a large mass) and knock it further way from the planet and break orbit. Even so, it wouldnt hit the same place it was in orbit over, it would hit "behind" it (relative to the rotation of the planet) and a bunch of it would burn up (depending on the atm) and hopefully the rest you could mop up with smaller guns

or..................

send a rag tag group of astronauts/scientists/sassy models/and a guy with a troubled past, to stop anything from crashing into the planet by attaching some sort of nuke or other-such equally unbelivable plan to redirect the ships hull into the sun or something. Failing that, a group of over the hill retired astronauts, I have seen that work too, cant remember where, but it has to be based on fact. At worst you can laugh at the hijinks as they try to get along and save the world, but more importantly discover something else......themselves.......

The problem is that debris is a non-issue in terms of "what will hit the planet". The debris will pretty much fall into one of three categories:

-sufficient velocity imparted to break orbit, wherein it's now heading into deep space.
-insufficient velocity imparted, orbit is normalized at a lower altitude; likely decays over the course of several decades (IE, relative non-issue)
-sufficient velocity imparted and at an appropriate vector to cause a "planet strike". Rarely will this be large enough to not burn up during "reentry".

So the problem with debris is not "oh noes, the sky is falling", but more likely to be "we have a lot of garbage in orbit that makes it hard to do STO/OTS runs".

-sufficient velocity imparted to break orbit, wherein it's now heading into deep space.

No, it wouldn't. A ground-based laser cannon, for example, would "peel" parts of the orbiting ship off, which is then in free-fall at the velocity of its parent vessel, +/-

insufficient velocity imparted, orbit is normalized at a lower altitude; likely decays over the course of several decades (IE, relative non-issue)

That is not a non-issue if that chunk of debris is a multi-megaton hunk of adamantine that's going to crash into a populated area. The friction of re-entry is likely insufficient to deplete the mass of, say, half of a cruiser-class starship.

sufficient velocity imparted and at an appropriate vector to cause a "planet strike". Rarely will this be large enough to not burn up during "reentry".

We're talking about entirely-metallic "asteroids" that are comprised of plasma-forged adamantine that are possibly kilometers in length and that are, more or less, semi-aerodynamic in shape. Re-entry will not cause significant burn-off of this material.

 Psienesis wrote:
No, it wouldn't. A ground-based laser cannon, for example, would "peel" parts of the orbiting ship off, which is then in free-fall at the velocity of its parent vessel, +/-

That is not even close to how an efficiently weaponized laser system would work. You'd actually have thousands-to-millions of nano- or micro-second pulses that explosively drill through the target.

 Psienesis wrote:
That is not a non-issue if that chunk of debris is a multi-megaton hunk of adamantine that's going to crash into a populated area. The friction of re-entry is likely insufficient to deplete the mass of, say, half of a cruiser-class starship.

A decades-long decay cycle is a non-issue because it means that you have plenty of time to stabilize the orbital track. This also assumes that the wreckage won't be recovered and reused.

 Psienesis wrote:
We're talking about entirely-metallic "asteroids" that are comprised of plasma-forged adamantine that are possibly kilometers in length and that are, more or less, semi-aerodynamic in shape. Re-entry will not cause significant burn-off of this material.

To be fair, something that I glossed over and that you've completely ignored is that an orbital warship isn't going to go into orbital decay unless there are some very extenuating circumstances. Things doesn't fall out of orbit because just it gets shot at.

What if the ship ignites the atmosphere? I know about O3, which is why you don't want to fly high without a pressured cabin. I would love for a Hawkins-like mathematician to enter this forum and explain stuff.

Extremely unlikely to happen. If the atmo was so volatile in the first place, the battle over the planet that brought the cruiser into orbit, or the lasers firing from the ground at said cruiser, would have ignited it already.

Yeah. Stable atmospheres, which any inhabited planet will have, aren't full of any compounds that would combust.

Our atmosphere isn't capable of igniting. And even a very high oxygen atmosphere is only a fire hazard when you have something that can burn, the oxygen itself just helps any fires that do occur.

 Grey Templar wrote:
Yeah. Stable atmospheres, which any inhabited planet will have, aren't full of any compounds that would combust.

Our atmosphere isn't capable of igniting. And even a very high oxygen atmosphere is only a fire hazard when you have something that can burn, the oxygen itself just helps any fires that do occur.

a high oxygen enviroment would be incredible corrosive. Increase the pressure and it will tear human life apart.

Our Terran atmo isn't even all that high in oxygen. It's, what, ~80% nitrogen, with some ~5% of various trace gases (xenon and argon and such)?

Yeah, but it could be much higher without any danger. Only once you get huge amounts would it be a problem.

 Psienesis wrote:
Our Terran atmo isn't even all that high in oxygen. It's, what, ~80% nitrogen, with some ~5% of various trace gases (xenon and argon and such)?

yup, 21% O 78% N 1% Ar

Good to a pressure of about 4 atmospheres before the nitrogen starts to cook your brain as a hallucinogen.
If you took it to 8 atmoshperes the oxygen will burn(well oxidize) your lungs and kill you pretty quickly.

The ratios are not the only thing that is important, the pressure makes a huge difference. If you take 100% pure O and up it to 2 atmospheres it will kill you.

 Psienesis wrote:
Our Terran atmo isn't even all that high in oxygen. It's, what, ~80% nitrogen, with some ~5% of various trace gases (xenon and argon and such)?

Isn't that about the size of the planet? I have seen the Universe-programs on Discovery.

I'm not sure what you mean about the "size" of the planet? I mean, Earth is like 25k miles around, 8k miles in diameter and like 200m square miles in surface area.

Yeah, but too large and pressure basically gets too great and crushes you. I think we can live on a planet a few times the size of Earth, but beyond that and gravity would crush us.

 Beaviz81 wrote:
Yeah, but too large and pressure basically gets too great and crushes you. I think we can live on a planet a few times the size of Earth, but beyond that and gravity would crush us.

Not necessarily. If the planet isn't as dense as Earth it could be much larger surface area. A molten core of mostly aluminum instead of iron for example.

 Grey Templar wrote:

 Beaviz81 wrote:
Yeah, but too large and pressure basically gets too great and crushes you. I think we can live on a planet a few times the size of Earth, but beyond that and gravity would crush us.

Not necessarily. If the planet isn't as dense as Earth it could be much larger surface area. A molten core of mostly aluminum instead of iron for example.

Do you know about the Goldilocks-hypothesis? Too small and its too light in gravity and we will die from both atrophy and lack of atmosphere. Too large and the atmosphere comes down and crushes stuff on the ground because of pressure. And you likely know enough to know what a too hot or cold planet would do to human physiology. But I will iterate. The planet can not be too cold, nor too warm, nor too small, nor too big. I highly recommend you to watch Discovery channel.

And yet, 40K has demonstrated that the "Goldilocks Zone" is not relevant to human interests or colonization of worlds. This is how Squats and Ogryns both came about.

Actually, low and high-gravity are words used to explain that. Nice try, but no dice.

 Beaviz81 wrote:

 Grey Templar wrote:

 Beaviz81 wrote:
Yeah, but too large and pressure basically gets too great and crushes you. I think we can live on a planet a few times the size of Earth, but beyond that and gravity would crush us.

Not necessarily. If the planet isn't as dense as Earth it could be much larger surface area. A molten core of mostly aluminum instead of iron for example.

Do you know about the Goldilocks-hypothesis? Too small and its too light in gravity and we will die from both atrophy and lack of atmosphere. Too large and the atmosphere comes down and crushes stuff on the ground because of pressure. And you likely know enough to know what a too hot or cold planet would do to human physiology. But I will iterate. The planet can not be too cold, nor too warm, nor too small, nor too big. I highly recommend you to watch Discovery channel.

I think you misunderstand.

You can have a planet with a larger surface area, but is less dense, leading to similar gravity to earth. Or at least close enough to allow habitation.

 Grey Templar wrote:

 Beaviz81 wrote:

 Grey Templar wrote:

 Beaviz81 wrote:
Yeah, but too large and pressure basically gets too great and crushes you. I think we can live on a planet a few times the size of Earth, but beyond that and gravity would crush us.

Not necessarily. If the planet isn't as dense as Earth it could be much larger surface area. A molten core of mostly aluminum instead of iron for example.

Do you know about the Goldilocks-hypothesis? Too small and its too light in gravity and we will die from both atrophy and lack of atmosphere. Too large and the atmosphere comes down and crushes stuff on the ground because of pressure. And you likely know enough to know what a too hot or cold planet would do to human physiology. But I will iterate. The planet can not be too cold, nor too warm, nor too small, nor too big. I highly recommend you to watch Discovery channel.

I think you misunderstand.

You can have a planet with a larger surface area, but is less dense, leading to similar gravity to earth. Or at least close enough to allow habitation.

You really need to watch Discovery Channel. If a planet is too large the gravity goes seriously up, too small and down by a serious degree. Plus you have the magnetic fields which protects the planet. Too much and you are dead meat, too little and the nearby star would kill you.

 Beaviz81 wrote:

 Grey Templar wrote:

 Beaviz81 wrote:

 Grey Templar wrote:

 Beaviz81 wrote:
Yeah, but too large and pressure basically gets too great and crushes you. I think we can live on a planet a few times the size of Earth, but beyond that and gravity would crush us.

Not necessarily. If the planet isn't as dense as Earth it could be much larger surface area. A molten core of mostly aluminum instead of iron for example.

Do you know about the Goldilocks-hypothesis? Too small and its too light in gravity and we will die from both atrophy and lack of atmosphere. Too large and the atmosphere comes down and crushes stuff on the ground because of pressure. And you likely know enough to know what a too hot or cold planet would do to human physiology. But I will iterate. The planet can not be too cold, nor too warm, nor too small, nor too big. I highly recommend you to watch Discovery channel.

I think you misunderstand.

You can have a planet with a larger surface area, but is less dense, leading to similar gravity to earth. Or at least close enough to allow habitation.

You really need to watch Discovery Channel. If a planet is too large the gravity goes seriously up, too small and down by a serious degree. Plus you have the magnetic fields which protects the planet. Too much and you are dead meat, too little and the nearby star would kill you.

Do you even know what mass is?

 Wyzilla wrote:

 Beaviz81 wrote:

 Grey Templar wrote:

 Beaviz81 wrote:

 Grey Templar wrote:

 Beaviz81 wrote:
Yeah, but too large and pressure basically gets too great and crushes you. I think we can live on a planet a few times the size of Earth, but beyond that and gravity would crush us.

Not necessarily. If the planet isn't as dense as Earth it could be much larger surface area. A molten core of mostly aluminum instead of iron for example.

Do you know about the Goldilocks-hypothesis? Too small and its too light in gravity and we will die from both atrophy and lack of atmosphere. Too large and the atmosphere comes down and crushes stuff on the ground because of pressure. And you likely know enough to know what a too hot or cold planet would do to human physiology. But I will iterate. The planet can not be too cold, nor too warm, nor too small, nor too big. I highly recommend you to watch Discovery channel.

I think you misunderstand.

You can have a planet with a larger surface area, but is less dense, leading to similar gravity to earth. Or at least close enough to allow habitation.

You really need to watch Discovery Channel. If a planet is too large the gravity goes seriously up, too small and down by a serious degree. Plus you have the magnetic fields which protects the planet. Too much and you are dead meat, too little and the nearby star would kill you.

Do you even know what mass is?

You basically seem to fail to even grasp the concept of gravity. Watch Discovery Channel.

 Beaviz81 wrote:

 Wyzilla wrote:

 Beaviz81 wrote:

 Grey Templar wrote:

 Beaviz81 wrote:

 Grey Templar wrote:

 Beaviz81 wrote:
Yeah, but too large and pressure basically gets too great and crushes you. I think we can live on a planet a few times the size of Earth, but beyond that and gravity would crush us.

Not necessarily. If the planet isn't as dense as Earth it could be much larger surface area. A molten core of mostly aluminum instead of iron for example.

Do you know about the Goldilocks-hypothesis? Too small and its too light in gravity and we will die from both atrophy and lack of atmosphere. Too large and the atmosphere comes down and crushes stuff on the ground because of pressure. And you likely know enough to know what a too hot or cold planet would do to human physiology. But I will iterate. The planet can not be too cold, nor too warm, nor too small, nor too big. I highly recommend you to watch Discovery channel.

I think you misunderstand.

You can have a planet with a larger surface area, but is less dense, leading to similar gravity to earth. Or at least close enough to allow habitation.

You really need to watch Discovery Channel. If a planet is too large the gravity goes seriously up, too small and down by a serious degree. Plus you have the magnetic fields which protects the planet. Too much and you are dead meat, too little and the nearby star would kill you.

Do you even know what mass is?

You basically seem to fail to even grasp the concept of gravity. Watch Discovery Channel.

You mean a garbage channel with incredibly basic shows compared to say, textbooks or actual books written by physicists?

Size does not matter if the mass is too low due to less density, or if there is no magnetosphere to prevent solar winds from blowing away the atmosphere entirely (Mars). What you're thinking off is the actual mass of the atmosphere itself.

The atmosphere weights down on a planet of course. So a really big planet has a really big atmosphere which weight down on the ground on the planet. Its the main reason scientists has failed to pierce the atmosphere of Jupiter.

In fluff heavy gravity eventually produced the Squats and Ogryns. Thats canon. It has been stated since the first edition.

 Beaviz81 wrote:

 Wyzilla wrote:

Do you even know what mass is?

You basically seem to fail to even grasp the concept of gravity. Watch Discovery Channel.

Actually Beaviz, it's you who fails to grasp the concept of gravity.

Gravity is a function of mass. Mass is determined via density and volume being multiplied together. By having a very large volume (IE, "size") and a very low density, you can have an Earth-like mass, and therefore, an Earth-like gravity field. As such, yes, you can indeed have very "large" planets that are of comparable gravitational condition to Earth. Whether or not it has a sufficient magnetic field or atmospheric composition for a shirtsleeve-inhabitable environment is a totally separate issue.

EDIT: and as to this:

 Beaviz81 wrote:
The atmosphere weights down on a planet of course. So a really big planet has a really big atmosphere which weight down on the ground on the planet. Its the main reason scientists has failed to pierce the atmosphere of Jupiter.

That's not how atmospheric pressure works. It's a function of atmospheric composition and *gasps* gravity. Jupiter has a very high gravity, due to its large mass. Neutron stars, for example, are incredibly dense and high-gravity objects, to the point that a human would be less than a smear on the surface of such a stellar object. A neutron star is also (relatively) small, but due to its high density (IIRC it's been said that a teaspoon of neutron-star-stuff has a comparable mass to Earth) it has an incredibly "heavy" gravity.

Put simply, Jupiter doesn't have a high density atmosphere that's difficult to penetrate* because it's "big", it's because it has an enormous gravity and a high-density atmospheric composition.

*Part of the problem with 'penetrating' Jupiter's cloud layers has more to do with the extreme turbulence therein. And much more relevantly, the incredible distance and expense of sending a probe mission to Jupiter.

Whiskey144 wrote:

 Beaviz81 wrote:

 Wyzilla wrote:

Do you even know what mass is?

You basically seem to fail to even grasp the concept of gravity. Watch Discovery Channel.

Actually Beaviz, it's you who fails to grasp the concept of gravity.

Gravity is a function of mass. Mass is determined via density and volume being multiplied together. By having a very large volume (IE, "size") and a very low density, you can have an Earth-like mass, and therefore, an Earth-like gravity field. As such, yes, you can indeed have very "large" planets that are of comparable gravitational condition to Earth. Whether or not it has a sufficient magnetic field or atmospheric composition for a shirtsleeve-inhabitable environment is a totally separate issue.

Then give me the nifty links for that since its complete knowledge I have never even heard about. I don't mind a long boring read, but please tell me which pages to look for.

 Beaviz81 wrote:

Whiskey144 wrote:

 Beaviz81 wrote:

 Wyzilla wrote:

Do you even know what mass is?

You basically seem to fail to even grasp the concept of gravity. Watch Discovery Channel.

Actually Beaviz, it's you who fails to grasp the concept of gravity.

Gravity is a function of mass. Mass is determined via density and volume being multiplied together. By having a very large volume (IE, "size") and a very low density, you can have an Earth-like mass, and therefore, an Earth-like gravity field. As such, yes, you can indeed have very "large" planets that are of comparable gravitational condition to Earth. Whether or not it has a sufficient magnetic field or atmospheric composition for a shirtsleeve-inhabitable environment is a totally separate issue.

Then give me the nifty links for that since its complete knowledge I have never even heard about. I don't mind a long boring read, but please tell me which pages to look for.

Well you could just look up how gravity is calculated.

http://en.wikipedia.org/wiki/Gravity

F=G*(M1*M2/r^2)

The force of gravity is entirely dependent on the mass of the two objects in question. A planet with a high volume, but very low density, can easily have lower gravity than a low volume, but high density, planet. See neutron star example, or a black hole.


Say we have two spheres, both the exact size of earth. One is made out of gold, the other is made out of styrofoam. The one made out of gold will have a much higher gravity than Earth does. The one made out of styrofoam will have much less gravity than Earth.

Earth's molten core is made out of mostly iron and nickel. This actually causes Earth to be the densest planet in the solar system. Oddly enough, some of the other planets would actually float if they were submersed in water. So really, for its size Earth is actually pretty high gravity.

If Earth's core wasn't made out of iron and nickles, and was something lighter like Aluminum, or it had no molten core at all and was just some porous rock like pummace, it would be much less.

 Beaviz81 wrote:

 Grey Templar wrote:

 Beaviz81 wrote:

 Grey Templar wrote:

 Beaviz81 wrote:
Yeah, but too large and pressure basically gets too great and crushes you. I think we can live on a planet a few times the size of Earth, but beyond that and gravity would crush us.

Not necessarily. If the planet isn't as dense as Earth it could be much larger surface area. A molten core of mostly aluminum instead of iron for example.

Do you know about the Goldilocks-hypothesis? Too small and its too light in gravity and we will die from both atrophy and lack of atmosphere. Too large and the atmosphere comes down and crushes stuff on the ground because of pressure. And you likely know enough to know what a too hot or cold planet would do to human physiology. But I will iterate. The planet can not be too cold, nor too warm, nor too small, nor too big. I highly recommend you to watch Discovery channel.

I think you misunderstand.

You can have a planet with a larger surface area, but is less dense, leading to similar gravity to earth. Or at least close enough to allow habitation.

You really need to watch Discovery Channel. If a planet is too large the gravity goes seriously up, too small and down by a serious degree. Plus you have the magnetic fields which protects the planet. Too much and you are dead meat, too little and the nearby star would kill you.

The size of the planet is not directly comparable to its mass. A planet could be large, but comprised mostly of silicate and aluminum, and thus would have less mass than a smaller planet of igneous rock and ferrous metals. The big planet would have less gravitic pull than the smaller in such a case.

How about starting with the Wikipedia pages for "Gravity", "Mass", and "Density"?

Think about it this way: density is an expression of mass per unit volume; for example, kilogram/m^3 would be an unit of density.

Volume is a measure of how much space something takes up, and is express by cubing a unit of length, like so: m^3.

kilogram/m^3 * m^3, would be kilogram*m^3/m^3, in which case the volume unit cancels out (via dividing itself), leaving only kilograms.

Thus, we have determined mass.

Mass is very relevant to gravity, particularly because weight and mass are separate concepts and measures; weight is more accurately applied as a measurement of how much gravity affects a given object, whilst mass is constant even without the influence of gravity.

For example, I weigh ~110 pounds, roughly 50 kilograms. In open space, however, I would weigh 0 lbs, but still mass 50 kilos. This is why weight is not especially relevant when considering gravitational effects, because it is a measure of easily varying value.

Consider Mars and Mercury, two planets whose gravitational values are actually within ~1% of each other. Yet Mars is both larger and more massive, whilst Mercury is much denser. In fact, Mercury has a density of ~98% that of the Earth, whilst Mars is ~71% the density of Earth.

Mars is also ~11% the mass of Earth, whilst Mercury is only ~5.5% the mass of Earth... and yet Mercury and Mars both have a surface gravity of ~0.38 g.

But if what you say is true, that if a planet is too small or too big, its surface gravity goes wildly down or up, respectively, how is that possible?

To cut to the chase, it obviously cannot be possible, as otherwise Mercury would have a vastly lower surface gravity.

Let's look at Jupiter as our final example; Jupiter has a mass of ~3178% that of the Earth, but a density of only ~24% that of the Earth and a gravity field that's ~250% that of the Earth.

In terms of volume, it's ~13213% that of the Earth... but if it's so much bigger, why is gravity only 2.5x heavier?

I submit that mass plays an enormously important role in how gravity works. I admit that I am far from an expert, being at best an amateur in the field.

But overall size (IE, volume/surface area) are only tangentially related to gravitational effects. Mass and density play a much larger role in gravitational effects, considering the "curious" case of Mercury and Mars, wherein they have nearly identical gravity fields.

To add on to the above, it is such features as this that cause "high-grav" or "low-grav" worlds, which gave us the Ogryns and the Squats of 40K.

Then you have all the many, many Death Worlds in the Imperium that are inimical to human life for one reason or another... and, yet, many of them do have human populations.

A planet could, conceivably, be extremely high-gravity... but have no atmosphere to speak of. It may lie too close to (or too far from) its star, or have lost its atmosphere due to some celestial cataclysm (or the action of Xenos). This will not change the gravitic measure of the planet to any appreciable degree. If Earth's atmosphere suddenly vanished, we wouldn't go drifting off into space, the planet's mass is what causes its gravity, not its atmosphere.

You fail to even grasp the very simple point I'm making. Mass causes gravity, mass comes in some degree from size, some degree from what the core is made of. But in the end, big planets has big atmospheres, small planet has small atmospheres. Size matters, its just that simple.

Read the Horus heresy novels... in plenty of novels these cruisers get shot out of the sky.. Plenty of refenrance!

 Beaviz81 wrote:
You fail to even grasp the very simple point I'm making. Mass causes gravity, mass comes in some degree from size, some degree from what the core is made of. But in the end, big planets has big atmospheres, small planet has small atmospheres. Size matters, its just that simple.

No, I understand what you're saying, but what you're saying is just incorrect. The planet's size has very little to do with the size (or presence) of its atmosphere.

 Psienesis wrote:

 Beaviz81 wrote:
You fail to even grasp the very simple point I'm making. Mass causes gravity, mass comes in some degree from size, some degree from what the core is made of. But in the end, big planets has big atmospheres, small planet has small atmospheres. Size matters, its just that simple.

No, I understand what you're saying, but what you're saying is just incorrect. The planet's size has very little to do with the size (or presence) of its atmosphere.

You have yet to disprove me in any way except stating I'm wrong and not forking up any facts.

 Beaviz81 wrote:

 Psienesis wrote:

 Beaviz81 wrote:
You fail to even grasp the very simple point I'm making. Mass causes gravity, mass comes in some degree from size, some degree from what the core is made of. But in the end, big planets has big atmospheres, small planet has small atmospheres. Size matters, its just that simple.

No, I understand what you're saying, but what you're saying is just incorrect. The planet's size has very little to do with the size (or presence) of its atmosphere.

You have yet to disprove me in any way except stating I'm wrong and not forking up any facts.

It has been shown multiple times. Look at the formula for gravity. It only cares about mass, not physical size.

Yes, being bigger(all other things equal) will result in higher mass. But not all things are equal. Composition of different planets will be different, thus their gravity will be mostly determined by their mass.

Jupiter is tens of thousands of times bigger than Earth, but its not tens of thousands of times the gravity.

You showed zero source. So I assume you just made it up.

 Beaviz81 wrote:
You showed zero source. So I assume you just made it up.

You think I would make up a well known and documented scientific equation?

I linked the wikipedia page on gravity, which has the equation. Here it is again. http://en.wikipedia.org/wiki/Gravity

And I really shouldn't have to source a very simple equation like that. Its common knowledge and anyone can verify it.

I think you misunderstand at least partly. A planet must have a certain size in order to have an atmosphere. Just look at Mars for example of a planet a bit too small to achieve that. And it can't be too large or the atmospheric pressure would crush anything on the ground.

 Beaviz81 wrote:

 Psienesis wrote:

 Beaviz81 wrote:
You fail to even grasp the very simple point I'm making. Mass causes gravity, mass comes in some degree from size, some degree from what the core is made of. But in the end, big planets has big atmospheres, small planet has small atmospheres. Size matters, its just that simple.

No, I understand what you're saying, but what you're saying is just incorrect. The planet's size has very little to do with the size (or presence) of its atmosphere.

You have yet to disprove me in any way except stating I'm wrong and not forking up any facts.

I feel like I'm getting suckered into doing all the research for a 7th grade science class report.

http://tinyurl.com/ylp2k5o
http://tinyurl.com/oopwn59
http://tinyurl.com/oq7oalu
http://tinyurl.com/qhey4d3

 Beaviz81 wrote:
I think you misunderstand at least partly. A planet must have a certain size in order to have an atmosphere. Just look at Mars for example of a planet a bit too small to achieve that. And it can't be too large or the atmospheric pressure would crush anything on the ground.

No, the real reason Mars doesn't have much of an atmosphere is because it lacks a magnetic field to keep solar radiation from blowing the atmosphere away.

And sure, on a large enough planet we'd have an atmosphere too dense for humans. But it would have to be a HUGE planet.

 Beaviz81 wrote:
You fail to even grasp the very simple point I'm making. Mass causes gravity, mass comes in some degree from size, some degree from what the core is made of. But in the end, big planets has big atmospheres, small planet has small atmospheres. Size matters, its just that simple.

but it really doesn't

case in point, the Planet Venus

Very similar size to the earth: 95% of the size of earth
Similar Gravity: 91% of earth's
Similar Mass: 81% of earth (less dense)
Drastically different atmosphere: 9000% greater atmospheric pressure

Now part of that pressure difference has to do with temperature. Venus is the hottest planet in the solar system, despite being much further out than Mercury. Most of it just has to do with Venus having more gas on it than earth.

Composition matters a lot more than raw size or even mass.

To capitalize on what Exergy's said, consider Mercury and Mars.

Mars is significantly larger than Mercury, and is even masses more. But Mercury has a gravity field that's almost identical to that of Mars... despite the fact that Mars is both larger and "heavier".

Could it perhaps be that the composition/density of Mercury is the reason for that?

The spinning iron core that creates our magnetic field makes our atmosphere possible. Which means that liquid aluminum core would not generate a magnetic field. Also gravity is directly proportional to mass, and mass is dictated by the amount of matter in a object, not its size (we call that volume). Mass and its relation to volume are dictated by a principle called Density (how compactly the matter is packed into a finite space), for instance, neutron stars, the most dense objects known in the galaxy short of black holes have gravity millions of times higher than earth because the density of the stars are huge, it is the same mass as a star packed into something a few hundred miles across. A table spoon of it would weigh as much as several hundred tons... so yea size of a planet relative to density dictates gravity, but size alone doesn't.

 GKTiberius wrote:
The spinning iron core that creates our magnetic field makes our atmosphere possible. Which means that liquid aluminum core would not generate a magnetic field. Also gravity is directly proportional to mass, and mass is dictated by the amount of matter in a object, not its size (we call that volume). Mass and its relation to volume are dictated by a principle called Density (how compactly the matter is packed into a finite space), for instance, neutron stars, the most dense objects known in the galaxy short of black holes have gravity millions of times higher than earth because the density of the stars are huge, it is the same mass as a star packed into something a few hundred miles across. A table spoon of it would weigh as much as several hundred tons... so yea size of a planet relative to density dictates gravity, but size alone doesn't.

It's not pure Iron, it's a mixture of Iron and Nickel largely with heavy elements mixed in to create something far denser than a normal Iron Nickel alloy.

Regardless of its actual composition, however, the fact that it's comprised of fairly heavy metals contributes to the total mass of Earth, which is where our gravity comes from. If our core were, say, silicates and aluminium, we'd have a low-gravity planet, even if it were the same size.

 Psienesis wrote:
Regardless of its actual composition, however, the fact that it's comprised of fairly heavy metals contributes to the total mass of Earth, which is where our gravity comes from. If our core were, say, silicates and aluminium, we'd have a low-gravity planet, even if it were the same size.

And even with an iron core, the day it stops spinning it doesn't matter what the mass of Earth is. The atmosphere simply gets blown off.

Theoretically, but not definitely. The spinning of the planet is not what creates its gravitic pull. All bodies of mass generate gravity; the more mass, the more gravity. While the centrifugal force of the planet's rotation is responsible, in part, for our weather patterns, it's theoretical whether or not it would somehow float off if we stopped spinning.

The main question on that is "why?". There's not another body within range to overcome Earth's own gravity well that would pull the atmosphere off.

 Wyzilla wrote:

 Psienesis wrote:
Regardless of its actual composition, however, the fact that it's comprised of fairly heavy metals contributes to the total mass of Earth, which is where our gravity comes from. If our core were, say, silicates and aluminium, we'd have a low-gravity planet, even if it were the same size.

And even with an iron core, the day it stops spinning it doesn't matter what the mass of Earth is. The atmosphere simply gets blown off.

We'd still have some atmosphere. Mars actually still has a, very weak, magnetic field despite having no molten core. And if it had the correct composition it would still be breathable. Of course solar radiation would be a huge concern for life, and this is the biggest reason a strong magnetosphere is needed. Atmosphere retention is a close second in terms of concern.

So any terraforming attempts on Mars would succeed in creating a breathable atmosphere, but it would always remain thin and you couldn't spend long periods outside without protective gear. Only the hardiest plants and animals would be able to survive.


Automatically Appended Next Post:

 Psienesis wrote:
Theoretically, but not definitely. The spinning of the planet is not what creates its gravitic pull. All bodies of mass generate gravity; the more mass, the more gravity. While the centrifugal force of the planet's rotation is responsible, in part, for our weather patterns, it's theoretical whether or not it would somehow float off if we stopped spinning.

The main question on that is "why?". There's not another body within range to overcome Earth's own gravity well that would pull the atmosphere off.

He meant the Core spinning, not the entire planet.

And without the strong magnetosphere our atmosphere would become thinner, probably still breathable. But it would wreak havoc.