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The situation I'm considering is as follows:

A space ship (a transport ship operated by two people) crashes onto a planet on which a swing-by was planned. The crew could escape using an escape capsule and land on the planet, while the space ship crashed on it. The escape capsule lands not too far from the crashed ship.

The planet has only a very thin atmosphere, so one can assume that the space ship did not burn up in the uncontrolled fall (however, I don't know how thin the atmosphere has to be to allow that, but since the planet is very hostile and the crew will need space suits outside anyway, I can make is as thin as needed).

Now my idea is that the crew will rescue some things from the ship wreck (like food reserves). But that of course assumes that anything could actually have survived the crash.

Therefore my question: Could such a crash realistically happen in a way that things could be rescued from the ship afterwards? Note that the things don't have to be in a particularly good shape, just good enough to be useful at all.

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    $\begingroup$ I don't have anything authoritative for an answer, but the description of an object with the mass of a space ship moving at space travel speeds hitting a stationary object the size of a planet is described in terms of 'megatons of TNT' $\endgroup$ – Tritium21 Nov 4 '14 at 21:09
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    $\begingroup$ Although the trajectory was miscalculated, can we assume that the ship and the planet still have roughly the relative velocity required for the originally intended slingshot maneuver? This will make it less likely for the ship to surive, and more difficult for the crew to survive ejection. $\endgroup$ – trichoplax Nov 4 '14 at 22:07
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    $\begingroup$ As a general tip for getting an intuition for realistic space maneuvering, go download Kerbal Space Program and play with it. Seriously. It's just a silly little game, but just going through the tutorial will teach you a lot more about how things work in space than you're likely to learn anywhere else outside an advanced physics class. (One thing you will learn is that landing a spacecraft almost intact is easy: just try to land it intact and almost succeed. If you try lithobraking straight from orbital speeds, though... you'll just make a crater.) $\endgroup$ – Ilmari Karonen Nov 5 '14 at 1:11
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    $\begingroup$ Doesn't a space-ship crash land at the beginning of "Pitch Black"? It's mostly intact and plenty of people survived with plenty of supplies. I might check out the opening of that movie to see if that crash is explained. $\endgroup$ – nhgrif Nov 5 '14 at 3:23
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    $\begingroup$ Much as I enjoyed it, I don't think Pitch Black is a source of much realism... $\endgroup$ – trichoplax Nov 5 '14 at 10:30

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This is all down to velocity, the only way to make anything of the ship survive is to slow down the descent a lot.

My suggestion would be to have the ship come in under power, but only just. At the last minute the crew eject when they realize they are still coming in too fast.

This both gives you a good explanation for why they end up close together and explains as much or as little of the crash as you would like surviving.

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    $\begingroup$ I'd go just a little bit further and say that some part of the very final landing procedure is broken, instead of the main deceleration failing. Astronomical speeds are fast and the slowdown predictable. It's unlikely that the deceleration doesn't either suffice or is so far off that the whole ship gets pulverized. But depending on terrain, winds, and ship damage, the last bit of landing might turn out messy. $\endgroup$ – Vandroiy Nov 4 '14 at 21:31
  • $\begingroup$ I'm more thinking some sort of incident in orbit, they try and come in for emergency landing. Realize at last minute they won't make it and bail. $\endgroup$ – Tim B Nov 4 '14 at 21:33
  • $\begingroup$ One doesn't exclude the other. One incident in orbit could make them decide to do a risky landing in the first place, with little time to check their destination. When they're close to the ground, that risk kicks in and they're faced with an environment where they can't find a safe way for touch-down (turbulence, mountains, fog, swamp, damage...), burning fuel rapidly as they hover around. They find a spot that would work for the escape pod, eject, and the ship drifts down close by. It's the same idea, but the last bit has the ship fairly stable, so it takes less damage. $\endgroup$ – Vandroiy Nov 4 '14 at 21:43
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    $\begingroup$ @celtschk Consider that failure of space-engines not necessarily means failure of atmospheric engines and/or emergency rockets or air-brake parachutes. If the ship under normal circumstances has planetary landing capability it is bound to have several independent engine systems. Even if on-board hierarchy fails (as you suggest) emergency automated landing sequence might take over and give the ship a reasonably controlled descent to the surface. $\endgroup$ – Tonny Nov 6 '14 at 10:09
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    $\begingroup$ Clouds with rocks in. The spaceship either doesn't have radar because normally it would be guided in to a spaceport, or the radar is kaput. So it clips a mountainside on the way down and the crew "bail out". $\endgroup$ – nigel222 Jan 28 '16 at 21:03
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It depends.

There are a few main factors to consider in determining whether any given thing will have survived.

1) The Speed(and angle) of Impact The faster the fall, the less likely it is that any given thing will have survived. High speed collisions could embed the ship in the ground and/or pulp it entirely, making recovery effectively impossible, regardless of other factors. The angle also plays an important role: a ship falling straight down is going to be in worse shape than one impacting at the same speed but at an angle. On the other hand, a ship impacting at an angle could have parts thrown a great distance from the impact site, making recovery easier in some ways, but much more time consuming.

2) The Site of Impact Harder surfaces will cause more stuff to be destroyed, but less stuff to be lost. If something goes flying, it's more likely to embed itself in the ground somewhere if that ground is soft. Flatter surfaces are probably going to be more amenable to recovery in general than forests or hills.

3) What you Want to Recover Different supplies take different amounts of force to break and are stored in different ways. Food could be much more difficult to recover because it's much more fragile than the plasma guns, but it could also be much easier because it is likely to be stored loosely, and therefore could be thrown out of the ship to safety much more easily if the hull is broken. Which brings us to the last consideration.

4) The Ship's Design Did the people who made the ship anticipate that it might need to survive a crash landing? If so, what parts did they prioritize for survival? Did it have emergency systems to kill speed during a crash? Did they activate in this case? How effective were they? Did the designers include some sort of emergency black-box thing which could survive things the rest of the ship couldn't? What did they put in it? Why those things and not others? You can justify almost anything surviving in some quantity provided that you can come up with some reason why the designers would think it cost-effective for it to do so. You just have to figure out who made the ship, and what their incentives were.

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    $\begingroup$ +1 angle of impact seems the biggest factor in determining how much of this ship survives the crash. $\endgroup$ – Twelfth Nov 4 '14 at 21:32
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Most of the current answers assume that you're very set on the characteristics of the planet and offer suggestions on what sort of ship and what sort of scenario would be necessary to recover what bits.

But you state:

The planet has only a very thin atmosphere, so one can assume that the space ship did not burn up in the uncontrolled fall

For the sake of this answer, I'm assuming you've decided the planet has a thin atmosphere because:

  1. You don't want the ship to burn up during entry.
  2. You want the planet to be hostile.

So first, let me address those two issues.

On point one, is the ship never intended to ever have a controlled landing on any other planet ever? Is this purely a single surface launch vehicle that then just goes between space stations in orbit?

If this ship is intended to ever land on any other planet, isn't it safe to assume that it could survive some degree of entry effects?

On point two, this is probably pretty obvious, but it's quite easy for the planet to be hostile without having a thin atmosphere. Thick atmosphere's aren't inherently breathable atmospheres.


I also want to second the recommendation of checking out Kerbal Space Program. In fact, it'd be a good way for you to simulate in a moderately realistic manner crash-landing into planets of various characteristics and seeing what kind of somewhat realistic results you might get. And the rest of this answer will based on some of my observations of the pretty realistic physics of Kerbal Space Program.

So with that said, assuming the ship would be capable of withstanding a thicker atmosphere in entry (because it's probably designed to land somewhere at some point), here are my observations of landings (and attempted landings) on planets of various characteristics.

The two factors of a body that most effect landing are their gravity and their atmosphere. Lower gravity means the planet pulls you in with less acceleration, and denser atmosphere means there's more aerodynamic drag to slow you do. So an ideal planet to have to crash land on would be one with low gravity and high atmosphere (presuming it's not so high the ship burns up).

We can also improve our chances by making the insertion angle quite shallow. Another answer addresses the angle of impact with the actual surface of the planet, but the angle of "impact" with the atmosphere can be important as well.

With too shallow of an insertion angle, the craft will essentially skid right across the atmosphere. If the ship hasn't escape the planet's sphere of influence, it will be forming a highly elliptical orbit, which if still crossing through the atmosphere, will eventually mean a disastrous landing as the ship will eventually come in with a very deep insertion angle.

A better insertion angle would be one that allows us to spend much more time in the atmosphere. The exact angle you'd want? I'm not quite sure.

If your vertical velocity is too high, everything will be destroyed. If your horizontal velocity is too high, everything will be destroyed.

On a planet with a very thin (or nonexistent) atmosphere and a non-functional ship, I'm not sure I can imagine a successful landing at all. However, with low gravity and some functional engines for some retroburning, it wouldn't be too terribly far-fetched depending on the exact scenario.

On a planet with a thicker atmosphere however, there's much more to be done to slow the ship down--particularly if it's equipped with parachutes that could be manually deployed. Without functional engines for retroburning however, a survivable landing still seems very far-fetched. With no engines whatsoever, you essentially need an atmosphere to almost completely nullify the vertical velocity (lower gravity helps but makes gravitational capture less plausible), and a very, very shallow impact angle... and a ship capable of skidding across the surface... and a little bit of luck to ensure there's no geologic features to crash into. (It is suspected that the satellite "Beagle 2" which was intended to have one of these skid-landings on Mars was destroyed when it skidded into the cliff-wall of a crater.)


It might be worth reading about how the Space Shuttle re-enters and lands back on earth. The space shuttle uses OMS to alter its orbit into the atmosphere. From here, it relies purely on RCS thrusters and control-surfaces (which is a fancy name for flaps--essentially the same as what's on any other airplane) to control itself in order to get the perfect balance of aerodynamic drag. Have to be mindful of heat, but also need to slow down. Once it reaches the lower atmosphere, it's not much more than a really expensive glider.

Once the shuttle actually touches down, a drag chute is applied to slow it down.

The space shuttle lands on a paved runway on wheeled landing gear. This seems unlikely for a crash... but presumably your ship could land in a very similar situation but simply skid across a plain and take fairly minimal damage given that it's just been in a crash... in space...

It'd also be completely believable for the engines to be completely useless but for RCS thrusters and control surfaces to still be completely functional. Control surfaces are most likely powered by electric servos and therefore powered solely. RCS thrusters generally use a different type of fuel. It's just an entirely different system altogether from the main engines.

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  • $\begingroup$ You're exactly on spot on the reasons for a thin atmosphere. Thank you also for the detailed information. $\endgroup$ – celtschk Nov 6 '14 at 7:57
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Thin atmosphere may be both a blessing and a curse in this scenario. While a thin atmosphere reduces the chances that the spaceship will burn up during an uncontrolled reentry, it also reduces the opportunity for aerobraking (slowing the spacecraft through friction by grazing the atmosphere), which is your best way to reduce the speed with which the spacecraft plows into the ground.

A lot of the outcome depends on the point at which the ship becomes an uncontrolled projectile. Assuming that the crew are able to perform at least some degree of deceleration (either via aerobraking or retroburning), then they may not need to bail out until the craft is in the low atmosphere, at which point the craft will be traveling relatively slowly, and a significant portion of the craft could survive impact.

The recent crash of Virgin Galactic's Spaceship Two provides some evidence to support this theory. Despite the tragic loss of life, photographs from the crash site indicate that significant portions of the spacecraft remain intact.

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  • $\begingroup$ SpaceShipTwo wasn't exactly failed re-entry, but just a drop from the launch-plane at relatively low altitude. But you have a point: A problematic emergency landing may be enough of a landing to limit the damage. $\endgroup$ – Tonny Nov 6 '14 at 10:12
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I would want to know what "crash" means. There would be some level of control during descent which would be utterly mandatory if the vessel was traveling from anywhere but the planet itself (i.e. from another planet or other solar system).

Think about the speeds you need to travel from one planet to another. If there is no slowing down, your impact will be faster than anything NASA has been able to reproduce in a lab (easily in excess of 100x faster than a bullet).

Now if you successfully slow down to orbital velocity and THEN lose control and crash, now it gets more interesting. Just doing $E=mgh$ will show the amount of energy to disparate would crush anything in existence unless it was a very small object and the entire space-ship was designed to cradle it during impact.

Which brings me to a final answer: what if "crash" just means "we couldn't control it as well as we wish?" The Apollo mission capsules returned by using ablative shielding to slow down from orbital speeds and then relied on parachutes to slow it down the rest of the way for impact. Martian landers have relied on parachutes as well. I think it would be totally reasonable for a ship to be equipped with emergency measures such as parachutes which do not technically constitute a landing, but could be easily controlled by computers like we had 30-50 years ago with a high degree of reliability.

The only question would be whether someone would justify the mass of the parachutes as a safety mechanism. They might intentionally design the ship to break up into unessential pieces and essential pieces, so they didn't have to bring enough parachutes for the entire ship, only the parts which one would wish to salvage in such an extreme event. Alternatively, there could be a political pressure demanding such safety mechanisms exist, such as to avoid polluting foreign planets with debris.

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  • $\begingroup$ This is a great answer, I would say the best yet. The question implies that the density of the atmosphere can be varied; it could be a little too thin for the main ship's parachutes, but not for the smaller emergency capsules' ones (this is likely from how parachutes scale). This scenario could allow fairly late separation from the main ship. I hope everyone hasn't moved on from voting on this question yet. $\endgroup$ – Vandroiy Nov 5 '14 at 16:52
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As people have said, for an interplanetary ship to hit a planet in full flight, the question is more whether you could retrieve items from the planet afterwards. So, you'd have to assume some kind of emergency system allows the ship to land anywhere near intact.

Perhaps most of the ship's mass is its mechanical systems, and the crew compartments are a relatively small capsule at one end; as a last resort, it fires the crew module backwards with some sort of explosive bolts, sacrificing the bulk of the ship as reaction mass to put the most valuable part into a survivable landing trajectory.

That would explain why a ship with no engines can do a controlled landing, but also make it plausible that the landing would damage it badly (the damage is expected, but this is a last-ditch measure). Unlike boats or even planes, spaceship crashes are pretty black-or-white-- it's either a perfect landing or a smoking crater.

It might be convincing for the ship to take a long time (days?) to come out of orbit; as it descends it looks for survivors / good landing sites, slowly adjusting course with small drag chutes.

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The NASA Genesis Mission (see recovery phase) is relevant. The plan was to enter the atmosphere, descend by parachute and be caught by a helicopter before it hit the ground. The chute failed to deploy and the craft slammed into the dessert but scientists were still able to recover useful samples from the craft even in its damaged state.

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Depending on how 'soft' the landing is, there might be some salvageable raw materials, and maybe a few recognizable pieces, but have you seen pictures of aircraft crashes? It's a mess.

Food stuffs would be most likely almost unusable probably unrecognizable. However, I would expect an escape pod to have the minimum supplies needed for however many people it was designed for. Enough for a minimum expected possible rescue attempt. It should also contain some minimum equipment such as shelters for a landing and a water purifier/recycler etc.

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  • $\begingroup$ Well, part of the planned story is that they are already far off the course (with defective communication, so nobody knows about their situation; them trying to get communication work again is an essential part of the story); they definitely will have to remain there for much longer than normally expected. $\endgroup$ – celtschk Nov 4 '14 at 21:37
  • $\begingroup$ Does the escape pod at least have an emergency beacon they can try to modify? $\endgroup$ – bowlturner Nov 4 '14 at 21:43
  • $\begingroup$ The idea wasn't that communication equipment from the ship was rescued (I'd expect anything that complex to not survive anyway). Actually, the main point is that I need a good reason for them to leave their rescue containment and walk over the planet's surface (the planet itself doesn't seem to be worth it). Trying to get things (especially food) from the ship wreck is a good reason, but only if you can hope to actually find something that survived. $\endgroup$ – celtschk Nov 4 '14 at 22:48
  • $\begingroup$ Could it simply be that the ship launches a bunch of lifeboats (on similar courses, so they land near each other), and the characters' lifeboat is missing its box of rations or whatever, so they need to find another one? $\endgroup$ – bobtato Nov 6 '14 at 12:18
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I would say it depends.

What is the ship made of, how much if an impact can it take, what's the gravity of the planet, mass of the ship (and tberefore force of impact)

Look at the effects of plane crashes. Full speed into the ground is worse than gliding in to a hard skid or river. Both are crashes. Coming in from orbit with no atmosphere and earth like gravity I'd expect it to be a very violent collision at 5km/s or more, creating a crater and/or tearing apart any current manmade materials.

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  • $\begingroup$ Wrote this hours ago it didn't post. Didn't mean to copy the "it depends" from everyone! $\endgroup$ – evandentremont Nov 4 '14 at 23:14
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    $\begingroup$ 5 km/s won't even keep you in Earth orbit. Coming home for Apollo was on the order of 10-11 km/s before aerobraking and parachutes, and if I recall correctly somewhere around the speed of sound when approaching ground after only aerobraking (so you needed those parachutes!). When translunar, Apollo 11 travelled at 10.8 km/s. $\endgroup$ – a CVn Nov 5 '14 at 9:31
  • $\begingroup$ True enough. I just doubled kerbal. $\endgroup$ – evandentremont Nov 5 '14 at 20:25
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I think another defining factor is how large the ship is to begin with. If you have more components (more engines, wings (for a spaceplane), landing gear, etc.), there's a greater chance that something will be damaged, but a smaller chance that everything will be damaged. If you take 10 engines and spread them out along a spaceship, the craft would have to be totally obliterated for none of them to work. Chances are, you'll get a couple that are okay. And if one of the crew is mechanically adept (I hope!), a few more could be salvaged.

That said, you won't be able to rebuild the original ship. A lot of crucial components will be damaged or destroyed. But you can probably make do. If an X-wing fighter crashes on a planet, the upper (or lower, depending on the angle) two engines could be intact. You might also have damage to one set of wings (again, it depends on the approach angle and, in this case, if the wings were spread out or bunched together). You won't be able to re-build the X-wing, but you might be able to cobble together some two-engine craft that can get off the planet.

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    $\begingroup$ Size has a huge problem here. Weight scales in the third power of a ship's size (e.g. radius), while surface drag and effect of wings or parachutes scale only with the square. Thus, in a thin atmosphere, slowing a large ship down would only work with thrusters. But the question talks of an "uncontrolled fall" (however long). A failure to significantly slow down the ship will totally obliterate it. It doesn't matter what it's made of when it is slammed into the ground with the free-fall speed at low pressure or worse. $\endgroup$ – Vandroiy Nov 5 '14 at 0:02
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The premise I've read thus far adds that there is little to no engine power, yet the crew are working through a gravity assist. That would mean the trajectories were calculated some time prior and the ship is coasting through.

An undetected moon might be more than capable of changing a gravity assist's result. Coming in at the wrong angle with respect to a large moon could result in an accidental gravity-assisted brake. The ship could drop into a high altitude orbit around the planet instead of being expelled from it as originally planned. In a scenario like that, the orbit of the ship after the braking would probably be further out than the moon.

Given the lack of engine power, the ship might be stuck in orbit. Toss in a failure of the solar radiation safety mechanism for impetus to get off the boat. They bail using emergency escape pods, where some contain people and some contain supplies. Instead of seeking out the ship as originally desired, the crew would be seeking out the supply pods like Easter eggs.

An additional quest might be figuring out how to get back to the ship in its high orbit for some MacGuffin.

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  • $\begingroup$ The supply pods are a great idea. They would also have the advantage that seeking them would need a much closer examination of the planet's surface, as those pods will not be as easily spotted as a big ship wreck. $\endgroup$ – celtschk Nov 6 '14 at 8:06
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Some material does survive from the bigger ships falling from space. When Skylab went down, debris were found on the ground. Or Columbia. Mir space station required deorbiting into uninhabited area of the ocean, and it is known that parts of Hubble may survive reentry. Of course, depends on the spacecraft and depends on the planet, but generally possible. You may assume that the ship has completed some part of the landing sequence to make this more realistic.

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