Realistic large spaceship crash effects

Question

So I've got a colony ship crashing onto a world, and I want to reality check its effects on ship, crew and landscape.

Firstly the ship is fairly large. Its job is to seed human colonies on alien worlds, and while it can move faster than light, its journey time length it still expected to be decades and thus it carries families and extensive facilities with it to cover every expected need.

However, on its final approach to the earth-like planet, it was planning to colonise, things go very wrong, and it loses the ability to properly slow down as it enters the atmosphere and crashes into the planet.

Couple of key points that need to be true for the sake of the story.

1. Most of the crew need to die, but I need to be able technobable my way how a small number didn't. So I need to avoid a 100% fatality rate crash.
2. I need some of the ship systems to still be repairable, the ship can -mostly- be a wreck, but not annihilated.

Now here come the bit where I'm wondering about the details.

Would it be reasonable to assume that a large ship would likely create a new canyon-like effect if it crashed at the right angle and slide across the surface?

What kind of damage would a mostly metallic hull likely suffer and what would it look like? Crumpling, discolouration?

I'm going to assume the main causes of death would likely be g-force related and fire.. so broken bones and people being smashed against walls? Along with people being burned alive and smoke inhalation?

Another factor that's important, is the crash site been left for a few hundred years in a earth like climate. Besides the obvious rotting, are there other factors I need to be aware of?

Answer 1

The ship breaks into pieces in high atmosphere, each with separate aerodynamic properties

I'm assuming the failure comes pretty late in the entry sequence, after a heat shield has slowed the craft considerably - otherwise, this will be a short story.

A big generation ship wont be built for high G loads like tumbling through the atmosphere, when air resistance hits the wrong parts of it (probably for the first time ever if it was built in space), it will rip into pieces.

This is the key to your story. Big light chunks fall slowly as they get air resistance. Small dense chunks fall quickly. Imperfect chunks tumble. Chunks deform on impact, decelerating survivors slowly enough that they survive.

The chunks will be spread over hundreds or thousands of km; eg this is where from the space shuttle Columbia ended up:

It's not only plausible for there to be a small number of survivors after an event like this - it's happened multiple times. Wikipedia list 5 people who have fallen to the planet's surface at terminal velocity without a parachute and survived, 2 of which were able to walk away from their impact with minor injuries, and 3 who needed immediate medical attention but survived:

• Vesna Vulović, 10.1km. Pinned between an airline food cart and a chunk of the aircraft cabin. Major injuries and needed first aid on the ground
• Alan Magee, 6.7km. Slowed down by a glass roof of a train station. Broken bones and organ damage but recovered in POW camp.
• Juliane_Koepcke, 3km. Still strapped in her seat and seat rows were joined together, and they deformed optimally on impact. Walked away and was found next morning.
• Ivan_Chisov, 7km. Hit the edge of a snowy ravine. Needed major surgery.
• Nicholas Alkemade, 5.5km. Hit pine trees and snow cover. Only injury was a leg sprain.

Will it create a canyon?

Only if it's made of unobtainium. When big metal things impact the ground at high speed the ground tends to win. Look at aviation crashes for example.

It depends exactly on how its constructed - but I'd expect each individual chunk that reaches the ground to be about the same size, composition, and velocity of the worst aviation disasters. They may scratch the ground, but they're not going to create a massive geological feature like a canyon.

What's the most common cause of death?

Someone's actually published a paper on this. Head injury is the most common single cause of death.

Multiple injuries were listed as the immediate cause of death in 42% of the fatalities, followed by head injury (22%); internal injury of thorax, abdomen, or pelvis (12%); burns (4%); and drowning (3%). Head injuries were most common among children. The majority (86%) died at the scene or were dead on arrival at the hospital. Eighteen percent of the victims were reported to have sustained a single injury, with head injury being the cause of death in nearly a third of these fatalities. Blunt injuries resulting from deceleration forces, in particular head injury, are still the most important hazard threatening occupants' survival in aviation crashes.

Are there any other factors? Yes - nudity

The corpses will be naked. Very little clothing (including underwear) will survive free fall from these altitude. Eg In MH17:

the New York Times’ Sabrina Tavernise took a grim inventory of the victims, noting that they included a woman “naked except for a black bra,” a man lying “still in his socks but without pants,” and a boy in “blue shorts, wearing red Nike sneakers but no pants,” who “lay with his arms and legs splayed outward, an iPhone by his side.”

The sudden exposure to 500km/hr+ wind of an inflight breakup will rip most clothes at the seams.

Answer 2

Bail out.

Some of the people in the crashing ship see what is going on. They are close enough to the shuttlecraft equivalents to get aboard and get out.

The big ship goes down and people inside are asphyxiated as the big ship breaks apart from air resistance entering the atmosphere. The broken apart pieces are slowed by atmosphere (and heated up) then they all fall at terminal velocity. Big pieces will leave a dent in the ground. As in a plane crash the bodies inside are smashed up when they hit. No-one is burned alive. If gory specifics are needed for your story I am sure you can find online exactly what happens to people in a plane crash.

The shuttlecraft free of the big ship try to shed velocity thru various improvised maneuvers of varying success. Some of these craft make it to the surface more or less intact. They would probably be able to find pieces of the big ship large enough to salvage for repairs although parts would likely be spread over a huge area and possibly nowhere near where the shuttlecraft come down.

Maybe there were other last minute launces besides the shuttlecrafts. I like the idea of the shuttlecraft parties later finding a lady and a cat that got into her gas giant atmosphere probe that then methodically lowered itself and its cargo down into the atmosphere. To make sure of the methodical part she tweaked the program from the inside on the way down.

Answer 3

You want a big ship crashed from orbital+speeds, with a nice canyon dug out by the ship, and you want some, but few survivors. Many systems intact-ish, but broken.

Canyon: Requires high impact inertia, huge mass, and something harder than unobtanium. But not extremely high impact speeds, as otherwise you just get nice round impact craters.

Survivors: Normally speaking, forget about it. Human bodies will turned to a bowl of soup-with-bone-shards at impact energies way below the "canyon-forming" levels.

Only practical solution: Limited range and location

Stasis Fields

Your travelers have the means to set up a complete motion stasis field, wherein nothing moves. At all. Effectively, time is suspended within the sphere.
These stasis spheres cannot be too large, otherwise they would have just covered the whole ship with it and landed like a brick. Say the stasis field is a bubble 5m in radius, max. It will completely protect its contents in perfect condition, unless the field collapses under enormous stresses. In which case, the field fails and it crumples like a tin can.
Shield bubbles cannot touch, cannot overlap. They must be discrete.

When the ship tries landing, it is like a bag full of walnuts. The guidance, propulsion and navigation cannot be inside the spheres, as being frozen would prevent them from working. Nor, unfortunately, can the crew who are manning these emergency systems. Nonvital crew and passengers and sections of the ship that are not required to do a landing, are suitably protected. Mostly. Some of the protective fields fail, most survive.

End result: The ship lands 80% or so intact, but the engines and computers and bridge crew and engineering are completely wiped out.
The ship gouges a huge canyon in the ground as it impacts. Quite destroying the exposed segments, but leaving many of the passengers and stores and non-ship equipment intact.
Ship structure on unshielded segments between stasis bubbles is crumpled, bent and generally badly damaged. Ship structure and mechanisms that were inside stasis bubbles that survived are in pristine shape.

You could even make a plotline out of having some of these stasis fields survive the landing, only to fail to switch off after the event. So there's this metallic-looking sphere sitting in the wreckage. It is an active field. What is inside? Maybe some other crew, maybe food, maybe those repair robots we so desperately want.

Answer 4

You have your solution right there: it loses the ability to properly slow down.

This doesn't mean it can't improperly slow down. Things went very wrong, but it didn't just crash into the planet.

Sliding is possible, and it may do some damage to the surface, but a full-blown canyon is improbable, because the earth being tossed aside will dampen its forward motion, and the harder the earth, the less damage the ship will be able to do, and the softer the earth, the more quickly the damage can erode away.

Damage to the ship is likely to look very like the damage to a car when it collides with rock: crumpling of the metal, breaking of fragile parts, people tossed about. Note that unlike today's cars, it will not have crumple zones.

Answer 5

Some replicators survive. The ship can't decelerate, but the atmosphere slows it down a little. It comes down as a flaming half-kilometer ball at twenty times the speed of sound, tearing branches off the trees a hundred miles away. But the computers enact one of their worst case scenarios and use maneuvering thrusters and aerodynamics to spin it up as it moves into the atmosphere until it breaks apart, and one of the pieces thrown backwards suffers comparatively little damage. That means that a few of the myriad solid state replicators, built from solid blocks of patterned silicon, are still able to produce expert technicians with portable equipment from the rapidly dwindling chemical feedstocks embedded in their microfluidic architecture.

The crash site is essentially a large meteor impact, decorated with blocks of alien stone (actually sophisticated electronics/microfluidics). The diversity of feedstocks present, and the centralized nature of some of them used for particularly specialized equipment, means that miners may occasionally tap a wondrous lode of silver or gold hidden within these ancient stones.

Answer 6

Crumple zones.

The centre of the biggest pieces remain mostly intact as the bits in front of it take the impact.

The ESA Schiaparelli used an analogous mechanism for the final landing. Though obviously the mechanism wasn't proven given the failure of the landing.

The touchdown speed will be a few metres per second, with the impact absorbed by a crushable structure similar to the crumple zone in a car, on the underside of the lander, preventing damage to the rest of the module.