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MarshallSam
17-11-2010, 22:30
No not Halo: Combat Evolved, I mean High Altitude Low Orbit. What I was wondering was is it possible for a Strike Cruiser to enter the HALO zone and then for Assault Marines to just jump off the ship? I know that it says assault marines leap from high flying thunderhawks, but if a marine strike force is low on thunderhawks, could they just jump from the ship itself?

Jonny_N
17-11-2010, 22:32
I like the idea, it sounds pretty desperate and heroic!, like it was crashing through the atmosphere and they made an emergency drop!

carldooley
17-11-2010, 22:38
if power armor can survive nuclear blasts, submersion and other adverse conditions, why can't it survive re-entry? for that matter, fluff advocates could say that all the gene-seed enhancements would allow an unsuited SM to survive the drop (if he doesn't land in lava or on granite :p).

Hellebore
17-11-2010, 23:34
The only thing a human has to worry about in a halo drop is lack of oxygen (perhaps some pressure problems). A marine could easily perform a halo jump naked, because they can hold their breath for a while and they can survive vacuum.

The problem is in the terminal velocity impact. A jump pack isn't designed as a retrothruster, but as a controlled falling device. They might be able to burn off all their fuel to slow themselves down to a normal jump speed.

Hellebore

Son of Sanguinius
18-11-2010, 01:54
if power armor can survive nuclear blasts, submersion and other adverse conditions, why can't it survive re-entry? for that matter, fluff advocates could say that all the gene-seed enhancements would allow an unsuited SM to survive the drop (if he doesn't land in lava or on granite :p).

Since when can they survive nuclear blasts?


The only thing a human has to worry about in a halo drop is lack of oxygen (perhaps some pressure problems). A marine could easily perform a halo jump naked, because they can hold their breath for a while and they can survive vacuum.

The problem is in the terminal velocity impact. A jump pack isn't designed as a retrothruster, but as a controlled falling device. They might be able to burn off all their fuel to slow themselves down to a normal jump speed.

Hellebore

Do you think the power armor could resist a sudden burn of all the fuel?

MarcoSkoll
18-11-2010, 02:12
The problem is in the terminal velocity impact.
And for a Marine in power armour, terminal velocity is probably about 400 miles an hour.

*SPLAT*

Although I wonder if perhaps some systems include suspensor units that act in a similar way to a Grav chute, nullifying some of the weight of the wearer.

MEcorp
18-11-2010, 02:41
I would certainly consider it possible for a marines jump-pack to contain grav-chute-type technology and thus for them to be able to survive a drop from low orbit. Not necessarily the best idea, but since when do marines do things the smart way ;)?

The Orange
18-11-2010, 03:02
I was under the impression that their jump packs were designed for only short bursts of thrust (in a forward direction), so I'd think they'd be inadequate from a high altitude. I mean, if it was so easy why would there be a need for Drop Pods at all? So no, I think it's unlikely.

Iuris
18-11-2010, 06:23
Well, a space vessel certainly can land on a planet, at least once. We have several instances of it happening. Only landing, of course - getting off again is an entirely different matter.

As for invulnerable marines in armor immune to nukes and capable of orbital reentry... well, some people like their heroes to be heroes on autopilot. Me, I cast "physics" at any of them that come near, and reduce their armor down to APC (ie, nto MBT) levels etc. Makes them at least slightly interesting.

Askil the Undecided
18-11-2010, 07:14
If we re going to get cagey about HALO jumps then we should remember this: humans can do them, so can a marine.

Jumpacks have a god damn reactor inside them (as do all SM backpacks) so power isn't really such a problem, also in the Space Worlf novels jumpacks are used to travel in a vaccuum so we know they can work without air (bafflingly) in addition if you actually read about characters using jump packs they grant the ability to hover briefly, thrust retroactively and change direction in midair. Although they are however designed to be used only intermittently.

When you think about it it begins to make sense, if jump packs couldn't do these things jumping out of a thunderhawk with one on would just make you hit the ground travelling faster than the thunderhawk you jumped out of.

Hellebore
18-11-2010, 08:25
Do you think the power armor could resist a sudden burn of all the fuel?

I was thinking more in terms of a several minute burn. A HALO jump takes a while, so they could spend the last part building up burn, keeping the engine continuously on. Not a massive thrust burn where all the fuel disappears in 5 seconds, because that'd probably put their skulls through their spleens. :p

Hellebore

Phoebus
18-11-2010, 10:31
It could be done, but the time it would take for the Assault Marines to reach the ground would be significantly greater than if the Strike Cruiser first launched Thunderhawks laden with Assault Marines.

Woodsman
18-11-2010, 10:54
I thought HALO was a parachuting technique.

How high up do you class HALO as being?

MarcoSkoll
18-11-2010, 11:02
I was thinking more in terms of a several minute burn.
Kinda counter to the point of a HALO jump, given that it stands for "High Altitude, Low Opening". (Well, generally. O sometimes means Oxygen, but that's rarer).

If you start a burn several minutes before impact, you'd be at quite some altitude when you did.

Hellebore
18-11-2010, 11:16
Well, the OP was describing more of a high altitude jump from low orbit (which is what he described the HALO acronym as). HALO is only around 25,000 feet, which is far too low for a space ship to come in at. High altitude jumps of 30 km are more like the OP's original description:
http://en.wikipedia.org/wiki/Project_Excelsior

Those jumps took 10+ minutes to complete due to the sheer distance Kittinger fell.

Hellebore

Phoebus
18-11-2010, 11:17
I thought HALO was a parachuting technique.

How high up do you class HALO as being?
Military combat freefall can technically include jumps above 10,000ft, though operationally we're talking 20,000ft and higher.

Technically there is no ceiling where the term is concerned; it's more of an operational capability thing. The pioneers of HALO did jumps as high as 30km above the surface back in to '60s.

MajorWesJanson
18-11-2010, 11:38
Drop pods are basically HALO devices for groups. Drop in from orbit, retro burn just before you hit.

narrativium
18-11-2010, 12:10
I'm just not sure the ship would survive the dive.

carldooley
18-11-2010, 12:17
I'm just not sure the ship would survive the dive.

well they ARE single use vehicles :D

as for using jump packs for deceleration burns - I can't be the only FPS player that used the HALO Reach and Tribes Jet Packs to survive falls from **splat** height. :p

x-esiv-4c
18-11-2010, 12:18
Space Marines can survive a nuclear detonation? Is this a new Mat-Wardism?

carldooley
18-11-2010, 12:27
Space Marines can survive a nuclear detonation? Is this a new Mat-Wardism?

sorry. Universe mixup (http://www.webscription.net/10.1125/Baen/0671319418/0671319418.htm)

Jonny_N
18-11-2010, 14:24
Space Marines can survive a nuclear detonation? Is this a new Mat-Wardism?

Only if they happen to be throttling a nearby Avatar or 15.

Phoebus
18-11-2010, 15:00
You know, this one's not that out of control as far as ideas go.

I'm not talking about being at ground zero. Go far out enough, though, and both the blast and combustive effects of the explosion soon fall to levels that power armour (at least the same power armour that gives you a reasonable chance of surviving a flamer blast) has a chance of protecting you from.

Remember, the blast, fragmentation, and combustive effects of most weapons--including nuclear ones, far enough away from ground zero--are deadly to unarmored humans... not supermen in futuristic, environmentally sealed suits of armor.

Wolfblade670
18-11-2010, 15:31
Well if we are using the standard of an armoured Marine being comparable to a modern IFV, many modern IFVs and other armoured vehicles such as the M1 Abrams were designed with the expectation that they could be used on a nuclear battlefield and as such were expected to survive a nuclear detonation at a reasonable distance from ground zero. Thus I don't see a problem with a Space Marine surviving such a blast as long as he is far enough away from the explosion.

massey
18-11-2010, 15:38
Well, marine armor is airtight, so coming in from low earth orbit is possible. It's theoretically possible for them to just jump off of a passing ship and do it. The reason you get such high reentry temperatures with things like the Space Shuttle is because they're moving so fast. A marine in armor wouldn't experience near the same level of heat since he wouldn't be travelling Mach 20+.

Terminal velocity is only about 120 mph for a skydiver. Remember that all objects fall at the same speed, regardless of weight, absent wind resistance. The fastest a human can go in freefall is about 200 mph, if he tucks in his arms and legs and points himself straight down (minimizing wind resistance). A big ungainly marine wouldn't be able to go any faster. So at max, you're looking at a 200 mph fall. If your jump pack produces 1G of thrust, it will take you about 9 seconds to come to a complete stop from a 200 mph fall. So we're really not looking at that big a deal.

Col. Tartleton
18-11-2010, 16:13
In my fluff this sort of stuff is built into the suit. They have grav dampeners (so that a half ton marine can can spring around all nimbly bimbly) and the fusion reactor vents can be used as retrojets to direct them around (usually for space combat).

Basically a marine can fall from any height with little wear and tear on the suit. Then they add Jump Packs on and controlled fall is the last thing on their mind. Marines would essentially be able to almost hover just using their grav dampener and vents, so when they strap a few compact jet engines on their back they're pretty swift. The thrust just has to move the mass, it doesn't have to worry about much gravity. So a Marine can fight equally well on planets with different masses and gravities.

Power Armor should be like Ironman Armor or Batman's utility belt. A billion randomly useful gadgets to give the marine his superhuman edge.

spetswalshe
18-11-2010, 17:20
We would probably need to know the limitations of jump packs to answer this kind of question. Presumably they would be extremely powerful, able to lift the weight of a fully armoured Marine over a building (even if he did give it a running jump to help set off), but unable to keep that up for more than ten seconds or so, otherwise they'd just be Flying Marines. Do they use fuel, or some kind of science-magic? If they use science-magic, what is the reason for the packs not being able to keep it up for some time? Heat?

I can't really see a higher jump being much more of a problem than a lower one for the actual Marine. However, isn't there something to suggest that spaceships built in-orbit wouldn't likely be atmosphere capable?

carldooley
18-11-2010, 17:29
Terminal velocity is only about 120 mph for a skydiver. Remember that all objects fall at the same speed, regardless of weight, absent wind resistance. The fastest a human can go in freefall is about 200 mph, if he tucks in his arms and legs and points himself straight down (minimizing wind resistance). A big ungainly marine wouldn't be able to go any faster. So at max, you're looking at a 200 mph fall. If your jump pack produces 1G of thrust, it will take you about 9 seconds to come to a complete stop from a 200 mph fall. So we're really not looking at that big a deal.

hold on. I was about to say that Kittinger managed to break the sound barrier on his jump, but after reading (http://en.wikipedia.org/wiki/Joseph_Kittinger) up on it, he fell short. I still maintain though, that when we are able to make suits that can survive reentry, we'll have a new million dollar sport - skydive from 100+ miles up.

MEcorp
18-11-2010, 17:29
Ironically, it appears it is the ship that is less likely to survive this type of deployment than the marine himself. Perhaps the ship could sort of 'skip' off the atmosphere and deploy the marines at just the right moment? Astartes vessels are heavily armoured after all and likely to be take a fair deal of heat/resistance from the atmosphere. I am not really familiar with the mechanics of atmospheric re-entry but presumably angle and speed (tangential speed?) play a large role. So if a ship is moving slowly (relative to the planet, maybe in the spinward direction) and mostly parallel to the planet might it only take minimal stress? Obviously the goal is not to get the ship into atmosphere but rather to get the Assault marines closest to the target.

The main problem I have with the idea of Low-orbit jumps is that they aren't really necessary. Thunderhawks and Drop pods are both void and re-entry capable and offer far smaller targets than a starship.

The Orange
19-11-2010, 00:02
Wasn't sure how relevant it is but Samial (Dark Angel guy on a jetbike) was the only marine that dropped out of a downed thunder hawk successfully.

Admittedly its hard to compare a jetbike to a jump pack, but my guess would be that Thunderhawks probably have to slow down a bit to allow Assault Marines to jump out successfully, Samial might have had to jump out of one moving faster and being on a bike that can continue moving when it lands worked in his favor. How fast would a strike cruiser be moving though the atmosphere I think would be another important consideration.

The Ginger Ninja
19-11-2010, 11:44
Space Marines can survive a nuclear detonation? Is this a new Mat-Wardism?

'News just in, Space Marines are giant cockroaches' :p
The only time I have heard of space marines surviving a nuke, was in the Space Marine Trailer, and I'm not even sure if that is a nuke or an orbital bombardment. Also do trailers for unreleased games count as cannon?

Polaria
19-11-2010, 12:42
Several things about real life HALO jumps:

1) Lack of oxygen is not an issue for a paratrooper with oxygen supply, so its not an issue for Marine with life-support in his power armor.

2) Jump pack that can carry a marine off the ground is, by definition, powerfull enough to slow his descent even after terminal velocity is reached. However, if jump pack is based on airbreathing jet technology the jet can't slow down the descent without afterburn because the intake is pointed wrong way. Whether the afterburner alone is powerfull enough, we don't know.

3) HALO jumpers of today use a drag-chute to slow down and stabilize their fall before the main chute opens. This is because once the velocity of the jumper rises up (the terminal velocity in upper atmosphere where the air is less dense is huge) there is a considerable risk of jumper losing his balance and starting an uncontrollable spin. Uncontrollable spin that high up leads to g-forces pooling your blood to extremities and induces unconsciousness in seconds. Whether marine jet packs can stabilize themselves enough in that thin air or whether the g-forces involved would be enough to drop a marine is something we don't know.

The point is that HALO jump isn't just about the terminal velocity. There is a whole new world of things-that-can-go-wrong-and-kill-you up there. However, considering that Marines are supposed to be best-of-the-best I'm sure they can do HALO jumps. Whether they need additional equipment than just jump packs to survive it is another matter altogether. I'd personally like to think that Assault Marine are both trained and equipped to do it. It would surely fit the portfolio of the best assault troops in galaxy.

Zweischneid
19-11-2010, 12:46
So the short answer to the OP would be... if you want them to be able to, they can.

Also.. all answers so far assume Earth gravity and atmosphere. Just adjust either, or both (double-Earth-gravity, much thinner athmosphere? half-Earth-gravity, much thicker athmosphere?, etc...), to suit your needs for HALO Assault Marines on the table, in a story or whatever you need em for.

MarshallSam
19-11-2010, 13:47
Thank you very much for all the responses. I'm working on a chapter that is down to one Company with a few supporting elements, and one strike cruiser. When looking at my strike cruiser the other day and the forward launch bay it just kinda occured to me that what if the ship were close enough to the planet, could assault marines just leap out rather than fly down in thunderhawks? I thank you all for answering my question.

carldooley
19-11-2010, 14:00
Also.. all answers so far assume Earth gravity and atmosphere. Just adjust either, or both (double-Earth-gravity, much thinner athmosphere? half-Earth-gravity, much thicker athmosphere?, etc...), to suit your needs for HALO Assault Marines on the table, in a story or whatever you need em for.

or how about jovians(Jupiter\Saturn) assault marines would be worth their weight in gold when fighting on or around gas mines and refineries. :shifty:

Easy E
19-11-2010, 14:36
or how about jovians(Jupiter\Saturn) assault marines

Not to be confused with Jovial Assault Marines, becasue no one wants those guys around... no body.

MarcoSkoll
19-11-2010, 14:38
Terminal velocity is only about 120 mph for a skydiver. Remember that all objects fall at the same speed, regardless of weight
Sorry, but no. While acceleration due to gravity is always the same, terminal velocity is highly dependent on the weight/drag ratio.

To demonstrate, take a hammer and a feather. Drop both. In a vacuum, they would hit the floor at the same time. Indeed, they did just that on the Apollo 15 misson. (http://www.youtube.com/watch?v=5C5_dOEyAfk)
But in an atmosphere, the feather hits its terminal velocity very fast and takes much longer to reach the ground.

Heavier objects might not accelerate faster in freefall, but they will have a higher terminal velocity. A Marine's terminal velocity (given all his extra bulk and power armour) will be massively more than that of a normal human, and probably more like the 400 miles an hour I guessed earlier.

AlphariusOmegon20
19-11-2010, 15:52
Well, marine armor is airtight, so coming in from low earth orbit is possible. It's theoretically possible for them to just jump off of a passing ship and do it. The reason you get such high reentry temperatures with things like the Space Shuttle is because they're moving so fast. A marine in armor wouldn't experience near the same level of heat since he wouldn't be travelling Mach 20+.

Terminal velocity is only about 120 mph for a skydiver. Remember that all objects fall at the same speed, regardless of weight, absent wind resistance. The fastest a human can go in freefall is about 200 mph, if he tucks in his arms and legs and points himself straight down (minimizing wind resistance). A big ungainly marine wouldn't be able to go any faster. So at max, you're looking at a 200 mph fall. If your jump pack produces 1G of thrust, it will take you about 9 seconds to come to a complete stop from a 200 mph fall. So we're really not looking at that big a deal.


LOL someone did the math.

*thumbs up*

Zweischneid
19-11-2010, 16:17
The reason you get such high reentry temperatures with things like the Space Shuttle is because they're moving so fast. A marine in armor wouldn't experience near the same level of heat since he wouldn't be travelling Mach 20+.

Terminal velocity is only about 120 mph for a skydiver. Remember that all objects fall at the same speed, regardless of weight, absent wind resistance. The fastest a human can go in freefall is about 200 mph, if he tucks in his arms and legs and points himself straight down (minimizing wind resistance). A big ungainly marine wouldn't be able to go any faster. So at max, you're looking at a 200 mph fall. If your jump pack produces 1G of thrust, it will take you about 9 seconds to come to a complete stop from a 200 mph fall. So we're really not looking at that big a deal.

Well, the reason Space Shuttles and such are moving so fast, is because they meet less/no resistance in HALO. The heat builds up as the drag slows them down. The same would happen to your Marine. He would initially be much, much faster than the 120 mph or whatever and would subsequently burn up through frictional heat as he gets lower and the air slows him down.

Your logic applies to Space Shuttles too. Just throwing them off a cliff wouldn't speed them up to Mach20 either. And they certainly don't have supersonic engines to move at speeds like that (in athmosphere) on their own.

madd0ct0r
20-11-2010, 02:00
I think massey was assuming the marine just steps out of the spaceship or, more correctly, is ejected behind the spaceship to eliminate the orbital speed.

So he is initially at zero velocity, and accelerates due to gravity only.
So, while potential Terminal Velocity is very high at that altitude, the marine is initially moving slowly. As he plummets, his velocity increases, the atmosphere thickens and his potential terminal velocity decreases.
At some point, the two meet. It is only after that point we start to see heat build up due to the Marine's potential terminal velocity being lower then his actual speed.

If he starts firing bursts of the jet pack from this point, enough to brake and stay just below the ever decreasing potential terminal velocity, the deceleration is done by the pack and not by wind resistance, therefore much less heat on the marine.


The Space Shuttle is orbiting at incredible speeds, and it's these speeds, not the acceleration due to gravity, that creates the huge heat build up.

johnmcl7
20-11-2010, 15:06
I can't see it being at all possible, I think it's in Helsreach they assault jump out a Thunderhawk and that seems at the limit of what the armour and jetpacks can take. The Strike Cruiser clearly couldn't come very low in to the atmosphere nor particularly slowly (relative to the planet's motion), I can't see how the marine armour would have any chance of surviving such a drop. The Thunderhawks themselves even at lower speeds seem to take a real beating on their hull from the stress of re-entry and they're much more solid than power armour.

John

J-rock
20-11-2010, 23:05
This reminds of an issue I had with Thunderhawk Transporters. The fluff goes to great lengths to explain how all the special technology that Thunderhawks have prevent them from burning up on rapid entry into an atmosphere. However, Thunderhawk Transporters carry their cargo outside of themselves. Rhinos don't have special anti-burning-up-on-re-entry technology. The same applies to Stormravens carrying Dreadnoughts underneath themselves.

Also, have there been any descriptions in the fluff of how Land Speeders are deployed? Presumably from Thunderhawk Transporters.

OT: Assault marines deploying from low orbit is the kind of insane out-of-the-box tactics I'd expect marines to use and get away with in desperate circumstances, but not a tactic they'd use without a real and desperate need.

GodofWarTx
21-11-2010, 10:53
i am just mentally picturing the Angry Marines riding down the wreckage of their ship right about now.

Always Angry. All the time.

Zweischneid
21-11-2010, 11:51
I think massey was assuming the marine just steps out of the spaceship or, more correctly, is ejected behind the spaceship to eliminate the orbital speed.

So he is initially at zero velocity, and accelerates due to gravity only.
So, while potential Terminal Velocity is very high at that altitude, the marine is initially moving slowly. As he plummets, his velocity increases, the atmosphere thickens and his potential terminal velocity decreases.
At some point, the two meet. It is only after that point we start to see heat build up due to the Marine's potential terminal velocity being lower then his actual speed.

If he starts firing bursts of the jet pack from this point, enough to brake and stay just below the ever decreasing potential terminal velocity, the deceleration is done by the pack and not by wind resistance, therefore much less heat on the marine.


The Space Shuttle is orbiting at incredible speeds, and it's these speeds, not the acceleration due to gravity, that creates the huge heat build up.

Gravity is enough. In HALO, without air friction stopping him, gravity alone will accelerate a marine fast enough (and irrespective of mass, as there is no drag). Above a 1g planet, and starting from 0 velocity, he'd break the sound barrier after a little over 30 seconds.

Also, a Space Shuttle in orbiting is.. as a matter of fact.. in free fall, but with enough tangential velocity to stay there. That's what orbiting is.. free fall. A Space Shuttle is orbiting at incredible speeds because of gravity!!! They are the same thing. It's not like Space Shuttles actually use engines to move that fast. A Space Marine jumping out of an orbiting ship would effectively reduce his tangential velocity (using a Jump Pack I'd assume) to get into a re-entry vector.

[edit]
Indeed, assuming a Marine has a worse mass-to-drag ratio than a Shuttle, he'd probably even outpace a re-entering Space Shuttle on an identical vector fairly quickly as he breaks less in thin, high athmosphere. The heat-shielding of a Space Shuttle would likely be inefficient for the much more compact body of a Marine/Human entering from Low Orbit all by himself.

J-rock
21-11-2010, 22:48
We're getting a little confused here. Re-entry from orbit and HALO jumps are completely different things.

The space shuttle typically orbits at 300 km and is travelling at 28,000 km/h due to that orbit. If it lands at the equator then it needs to decelerate to 1,500 km/h, since that is the velocity of the surface of the Earth at the equator with respect to the Earth's axis of rotation. To put Project Excelsior in context, the jump was from 30 km and the top speed reached was 1000 km/h. This speed, however, was essentially downward since the balloon was not orbiting the planet. The two cannot be compared since they're using different frames of reference. Or, to put it more simply, you're confusing uppy downy motion with spinny roundy motion. Something that's easily done (http://xkcd.com/123/).

To further complicate matters, all our orbital devices are in free fall (as stated by the above poster) and so their velocity is entirely dependent upon their altitude, whereas space ships in 40k have their own propulsion systems. Presumably, they could simply adjust their orbital velocity to whatever is appropriate before jumping out. Please let me know if you agree with my opinion of the mechanics of the situation, professional pride is at stake!

madd0ct0r
22-11-2010, 02:55
That was my argument too, although i should have been more clear.

I'm also assuming the jetpacks don't need an air intake, as they operate on worlds with other atmoshperes

Col. Tartleton
22-11-2010, 03:26
Negative acceleration. Unless I'm mistaken you can't decelerate.

(Might be misremembering my Physics)