Starship wrecks

[rancke]

There's a question that has occurred to me while thinking about the quest for Norris' warrant. How tough are ultra-tech spaceship hulls?

It seems to me that there are three possible outcomes of a ship hitting the ground:

Hull intact, crew alive.
Hull intact, crew injured or dead.
Hull broken, crew pulped.

The hull broken, some people not dead outcome doesn't seem to me to be an option.

Am I wrong? Can you see a TL15 cruiser strike Algine's surface hard enough to break it open yet lightly enough for (some of) the crew to survive?


Hans

 

[jcrocker]

On the whole, no.

Of course, if the Chief Engineer makes a Miraculous task roll vs. technobabble, and they manage to time the landing so they impact on a downhill slope while the inertial compensators are burned out in an emergency overdrive... [bonus points for reversing polarity]

If you need/want survivors in the wreck, a more logical way to write it would be to have some crew land nearby in escape pods or lifeboats and move into the wreck if there's no other shelter nearby.

 

[Lycanorukke]

Was the ship breaking up before it hit the ground or did it break open on impact? If it was already breaking up, the impact velocity wouldn't have to be as hard as turning the crew into chunky salsa.

Some aircraft crashes have had people in the detached tail survive as the front/middle is what absorbs the (relatively low) impact energy. But even in that case the number of survivors would probably be small, and none of them would be dancing anytime soon.

Unless of course the ship actually came down mostly intact, but then the magazines cooked off or something and blew it open later.

 

[robject]

If it's coming in at high speed, it's smushed. It's difficult to hit the ground in such a way that just enough hits break the ship but doesn't cause grav compensation to fail. Or worse.

 

[BlackBat242]

Some aircraft crashes have had people in the detached tail survive as the front/middle is what absorbs the (relatively low) impact energy. But even in that case the number of survivors would probably be small, and none of them would be dancing anytime soon.

http://abcnews.go.com/US/year-plane-crash-survivor-made-miracle-walk-safety/story?id=27980085

How 7-Year-Old Plane Crash Survivor Made 'Miracle' Walk to Safety
Jan 3, 2015, 2:46 PM ET

For a young girl to be able to walk away from a plane crash that killed everyone else on board, and then make her way through rough, densely wooded terrain at night to find help is being called an incredible miracle.

The crash happened late Friday in Kuttawa, Kentucky, according to the Federal Aviation Administration.

Disoriented and barefoot, the girl walked roughly three-quarters of a mile* through the remote wooded area in southwestern Kentucky to the home of Larry Wilkins, who called 911 and tried to get her warm and cleaned up.

Kentucky State Police Lt. Brent White told The Associated Press the girl had to cross two embankments, a hill and a creek bed to get from the site of the crash to Wilkins' house, and the temperatures were below 40 degrees last night.

"She literally fell out of the sky into a dark hole and didn't have anybody but her own will to live and get help for her family," White said. "Absolutely amazing."

Despite what she went through, the girl was coherent and calm when interviewed by authorities, White said.

The girl's parents, Marty Gutzler, 48 and his wife, Kimberly Gutzler, 46; her sister, Piper Gutzler, 9; and, a cousin, Sierra Wilder, 14, were all killed in the crash. They were all from Nashville, Illinois.

That the girl suffered only non-life threatening injuries was astonishing in itself, officials said. She was treated for a broken wrist and other injuries at Lourdes Hospital in Paducah, Kentucky, and released to a family member Saturday morning, police said.

"There really isn't any medical or scientific reasoning for that," said Ashton. "I mean, we know kids are incredibly resilient, but factors that we do know are associated with survival of a plane crash again, where you're seated and again with any high speed trauma, whether you're restrained or unrestrained, so what that means is if you have a seat belt on or not."

"There's a principle that we use in emergency medicine when there's, let's say, a motor vehicle accident - if there are fatalities at the scene, it gives us an indication of the degree of trauma," Ashton added. "Clearly this is no different."

* While this text originally said "a quarter of a mile" all other reports cite three-quarters of a mile actual distance traveled, the "quarter" is apparently straight-line distance.

 

[aramis]

If it's coming in at high speed, it's smushed. It's difficult to hit the ground in such a way that just enough hits break the ship but doesn't cause grav compensation to fail. Or worse.

Almost any failure of G-Comps means dead or dying crew on impact.

 

[rancke]

Almost any failure of G-Comps means dead or dying crew on impact.

I hadn't thought about inertial compensators. But would they make any difference? If the impact is hard enough to crack a starship hull, would a mere 6G of compensation be enough to protect the crew?

My problem here is that I have no idea how tough a crystaliron or superdense or bonded superdense hull is (even without armor, let alone with), but that I suspect that it's quite tough.


Hans

 

[aramis]

I hadn't thought about inertial compensators. But would they make any difference? If the impact is hard enough to crack a starship hull, would a mere 6G of compensation be enough to protect the crew?

My problem here is that I have no idea how tough a crystaliron or superdense or bonded superdense hull is (even without armor, let alone with), but that I suspect that it's quite tough.


Hans

The fleshies break before the inertial comp. A typical vehicle crash at 30mph causes a 20G deceleration on the belted passengers with stretchy seatbelts, and a 150 G (at impact with the car) for the unbelted ones. Knocking 6 G's off is going to matter a good bit. 7 actually - the AG can be reversed, too.

And the unbelted crew can be, if the computer is working, programmed to move them to the furthest spot back prior, so that it can have the maximum distance to slow them in. Effectively, a 3m+ "stretchy seatbelt" if the G-comp holds, which is going to make the felt G's considerably less.

So, it matters. If the G-Comp fails, and the standard lateral thrusting layouts are used, it matters a lot on a nose it, and a lot less on a belly flop; reverse those for vertical thrust.

http://hyperphysics.phy-astr.gsu.edu/hbase/carcr2.html

 

[Travellerspud]

...My problem here is that I have no idea how tough a crystaliron or superdense or bonded superdense hull is (even without armor, let alone with), but that I suspect that it's quite tough. Hans

part of my job is to destroy things, to better understand how to avoid damaging them in shipment for the lowest cost.

Traveller says bonded super-dense is equivalent to 14x it's thickness in steel....at appx. 2x the weight

there is a very crude estimate of g's during impact that is sometimes useful;

D/d = g

D= drop height
d= stopping distance

so a 100 inch drop stopping in 1 inch would be ~100 g's

this is extemely crude, and does not account for terminal velocity in atmosphere....but surprisingly accurate (on 1-g Earth at least)

then there is F=Mg (force = mass x g's)

and of course, P=FA (pressure = force x area)

combing these we get;

F=MgA

steel yields between 36,000-80,000 psi (pounds per square inch), so by definition super-dense would yield at 504,000-1,120,000 psi (14x)

this is a long-winded way of saying that you basically, for the same drop/impact/shape, be able to have the same damage to the structure for a drop 7x as high with super-dense as you would with steel (14x stronger but twice the mass)...and the "g's" would be 14x as high (to those inside) at failure...

also, for some ideas of what a starship with a hull equivalent to meters of steel could do on impact (depending on speed & impact angles);

https://www.youtube.com/watch?v=5kDbwE7mFck
https://www.youtube.com/watch?v=NLHP9h8zYD0
https://www.youtube.com/watch?v=o1vAqkdPlTk
https://www.youtube.com/watch?v=svFwsJsHHGs
https://www.youtube.com/watch?v=tHwTodgGA-M
https://www.youtube.com/watch?v=QfDoQwIAaXg

 

[Reban]

Can you see a TL15 cruiser strike Algine's surface hard enough to break it open yet lightly enough for (some of) the crew to survive?

When you say "break it open" are you saying the hull has been ruptured or just that there is access to the interior.

If the descent was in anyway controlled and it didn't hit with "smushing" force, things like airlocks, exterior hatches, cargo doors etc. could pop open due to the impact or because the hull gets bent out of shape.

There may also be other access points to a crashed hull like exhaust ports and nozzles which are not normally accessible in space. Missile ports might provide access if you can crawl down one into the turret.

No matter how strong the hull is, it has to have weak points built into it to provide access or exits for the crews.

 

[robject]

Mapping impact velocity to the number of hits to apply to the ship is the Traveller Way To Do It. But free-fall to the surface is going to smush...

 

[rancke]

Mapping impact velocity to the number of hits to apply to the ship is the Traveller Way To Do It. But free-fall to the surface is going to smush...

The story so far -- my story, that is, not canon -- is that the maneuver drive was weakened by the misjump explosion, so when the the Blue Heron goes to full emergency military speed, the drive is strained and fails part way down the atmosphere. So I can pretty much suit myself as to final impact speed.

The thing is, the crash alone leaves Norris' task a little short of complications: just get to the wreck and retrieve the warrant. I can add any number of obstacles to his route from where he is put down to the wreck, but it would be nice if someone had picked up the warrant and moved away from the wreck. It seems to me that that someone has to be the captain. If the messenger is alive, he would have been evacuated at the earliest possible moment, but the captain is the only other person I can see having access to a safe where the warrant is kept.


Hans

 

[robject]

The thing is, the crash alone leaves Norris' task a little short of complications: just get to the wreck and retrieve the warrant.

Could the vault have had a safety ejection before impact, so that it lands in a rather inaccessible location with a damaged transponder?

 

[Reban]

Even if its not ejected, the vault being a massive object may come loose from its position within the hull and travel a long way forward of the point of impact.

I'm thinking here of WW2 air crash archaeology where once the point of impact is determined the searchers can look along the vector of the crash to find the engine. Being massive and heavy it continues forward, but understanding the kinetics of the crash makes it relatively easy to locate.

Along the same theme you might want to think about underwater archeology on shipwrecks.

First comes the research, pulling together all the known facts and rumors to narrow down the location of the wreck.

Then comes the actual location of the hull or debris field.

Once you understand the location/orientation/shape of the debris field or hull you can make a much better guess as to where the vault will be found. This holds through even if it was ejected before the crash.

Even if Norris didn't undertake this kind of work once he got to the wreck thinking about it helps paint a picture for the players/readers.

And if he did have to do some of this work, it slows him down and presents complications for him, which is what you're looking for Hans.

 

[Carlobrand]

part of my job is to destroy things, to better understand how to avoid damaging them in shipment for the lowest cost.

Traveller says bonded super-dense is equivalent to 14x it's thickness in steel....at appx. 2x the weight

there is a very crude estimate of g's during impact that is sometimes useful;

D/d = g

D= drop height
d= stopping distance

so a 100 inch drop stopping in 1 inch would be ~100 g's

this is extemely crude, and does not account for terminal velocity in atmosphere....but surprisingly accurate (on 1-g Earth at least)

then there is F=Mg (force = mass x g's)

and of course, P=FA (pressure = force x area)

combing these we get;

F=MgA

steel yields between 36,000-80,000 psi (pounds per square inch), so by definition super-dense would yield at 504,000-1,120,000 psi (14x)

this is a long-winded way of saying that you basically, for the same drop/impact/shape, be able to have the same damage to the structure for a drop 7x as high with super-dense as you would with steel (14x stronger but twice the mass)...and the "g's" would be 14x as high (to those inside) at failure...

also, for some ideas of what a starship with a hull equivalent to meters of steel could do on impact (depending on speed & impact angles);

https://www.youtube.com/watch?v=5kDbwE7mFck
https://www.youtube.com/watch?v=NLHP9h8zYD0
https://www.youtube.com/watch?v=o1vAqkdPlTk
https://www.youtube.com/watch?v=svFwsJsHHGs
https://www.youtube.com/watch?v=tHwTodgGA-M
https://www.youtube.com/watch?v=QfDoQwIAaXg

Okay, but the question isn't what the ship does on impact, it's what the impact does to the ship. Terminal velocity's gonna vary all over the place depending on the way the ship's hitting air, it's density, and yaddata yaddata (meaningless lingo intended to describe all the unknowns we're dealing with concerning the ship and its circumstances immediately prior to re-entry). Then there's the question of what it hits: a nose dive into deep water is gonna hurt less than a belly flop into a mountain. And, if I understand you correctly, another way of looking at that stopping distance is to ask how deep the resulting crater is.

I'm gonna wildly guess we're dealing with impact velocities greater than a couple hundred kph - maybe a lot greater - but I've no way of figuring how deep a crater the ship ploughs since I don't know the nature of the terrain it impacted in, ergo I have no way of guesstimating the impact Gs. I'm guessing, if there's any control at all, that the pilot is doing his damnedest to kill velocity, so I presume the ship is gonna more or less bellyflop it unless he's over deep water and sees a last minute opportunity to preserve the ship's structure by diving instead of bellyflopping. The real question, given your statement regarding the hypothetical yield strength of bonded superdense and assuming a bellyflop, is, "How hard does this thing have to hit before the sides split and the top of the hull comes down to squish everything and everyone beneath it?"

 

[wbyrd]

A high velocity impact, is a sure fire way to ruin both ship and crew. However even a slight bit of control during the unscheduled mission event could reduce the velocity of the impact to withing human tolerances.

If the ships internal systems..grav plates particularly were still functioning, they could be used to generate some counter force to soften the effect on the crew. Add in restraints and acceleration couches the survival rate goes up a bit more.

I recall during some testing a man survived a 40 gee deceleration without serious injury, so if the gee forces could be brought to less than fifty or sixty Gees on impact between the grav plates, and restraints a good number of crew might survive...they might need some attention from the medical staff, auto=doc etc..but survival wouldn't be out of the question.


If the ship itself had only lost main drives and still retained some portion of its maneuvering systems a bit of skill on the helmsman and engineers could get the ship to the ground without loosing all the crew in the process.

 

[Travellerspud]

...if there is any attitude control, a last-minute change in vector to a glancing blow vs. a nose-dive could make all the difference...effectively changing the "stopping distance" from the depth of the crater, to the length of the skid....

the Air Force has a book on "limits of human endurance" (or something like that), which details how many g's in various positions the human body can take. It was pretty gruesome reading, things like 50% death rate or 50% injury rate, etc. The studies were done using cadavers and live test subjects. 10 g's was about where bad stuff started happening, as I recall, unless you were properly seated and the direction was just so.

so, assuming g-compensators, a 16g impact could be survivable without injury if strapped in, and maybe a 30g impact with injury and a 30g-60g with serious injury/death....all of these are within the realm of a skid landing, and the hull would be essentially intact (although possibly not working so well, with gaps in hull plates, twisted frame, etc).

and a trick for getting around calculating air resistance, etc - decide what your impact velocity is (say 5000 kph, or 10,000 kph) then determine what the height would need to be, ignoring air resistance to get that equivalent falling speed. That becomes your dropping height, and the skid length the stopping distance....or to simplify - for a "20g impact" (survivable with some injuries), the dropping height (equivalent speed) should be appx. 20x the skid length....

 

[CosmicGamer]

Not an expert or even an amateur in all the math and science involved here, but I do have some thoughts which can be ignored if they are way off.

First, I've dropped a carton of eggs before and had the end that impacted damaged and several eggs broken but others remain intact. Granted, an egg carton is no ship hull but it is many times stronger than the fragile eggs inside. Also there is no grav tech protecting the eggs.

Next, the size of the ship.
Would the larger the ship is increase the likelihood one section could take the majority of the impact and sections of the ship further out take less and could have survivors?

Some silliness.
Get into your armor and go into the cargo bay and crawl into the middle of the container that is shipping several dtons of pillows.

 

[rancke]

I appreciate the ideas about the cruiser crash on Algine. However, the reason I posted this as a separate thread was that I was interested in starship crashes in general.

I have no doubt that a (suitably braked) ship can hit the ground gently enough to allow for survivors. What I am dobtful about is whether such an impact would be hard enough to break the hull. Or in other words, how many G impact would it take to break a TL15 hull? Few enough to allow survivors?

Reban's point about air locks being weak spots is a good one.


Hans

 

[WistfulD]

The story so far -- my story, that is, not canon -- is that the maneuver drive was weakened by the misjump explosion, so when the the Blue Heron goes to full emergency military speed, the drive is strained and fails part way down the atmosphere. So I can pretty much suit myself as to final impact speed.

The thing is, the crash alone leaves Norris' task a little short of complications: just get to the wreck and retrieve the warrant. I can add any number of obstacles to his route from where he is put down to the wreck, but it would be nice if someone had picked up the warrant and moved away from the wreck. It seems to me that that someone has to be the captain. If the messenger is alive, he would have been evacuated at the earliest possible moment, but the captain is the only other person I can see having access to a safe where the warrant is kept.


Hans

AH! It's a failed landing, that's the information we need! People survive crashes that are failed landings. In fact, they do it a lot more often than the cable news cycle would leed us to believe.

I haven't recently read any stats on the physical properties of Traveller starship hulls, but thematically they seem much more heavy, thick, barge-like than Star Wars or Star Trek ships, for instance. Thus I think they probably break their spines (and those of their passengers) before they split open like over-ripe tomatoes, but let me posit another scenario:
Depending on what part of the descent the drive failure happens in, the pilot could dead-stick the thing into not so much a head-on-collision-with-the-ground crash as a landing-not-on-an-airstrip. That wouldn't break the thing up, but a sufficiently anchored rocky outcropping could shear open the ship like an iceberg to the Titanic, exposing exactly as much of the ship as you like while still making the crash survivable to anyone you need, especially with inertial dampening, seatbelts, accelleration couches, and/or impact foam/crashwebs/whatever airbag-equivalents you put in your ships.