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What would a hull breach look like?
#1
We're planning to add hull breach from a small asteroid or space-debris impact to the possible crisis scenarios in version 0.23.  But as we prepared to implement it we realized that we're not sure:

What would a hull breach actually look like?

Would the hull material be bent in and then punctured, so that from the inside, it looks something like a volcano?  Or would it actually be bent outward from the air blowing out while the metal is still hot?  Or would it simply be a ragged hole, where the hull material was instantly vaporized on impact?

Joe Strout
Lead Developer, High Frontier

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#2
Forgive my ignorance, I'm not intimately familiar with your game - but now that I know about it I am excited to find out more! However you (Joe) also sent the question in to the Space Studies Institute and said it was ok for SSI folks to contemplate it here goes my personal knee-jerk...

Good question.

For a game, even one trying to stick to hard-physics it has to look cool and exciting and it can break some minor rules of reality for effect, but for the real things I think it should be part of the design to accommodate such unusual possibilities a bit better. Either way I think the first answer is the same, and is a question...

How big a rock, why kind of "rock" (or type of debris), what's the internal pressure? (O'Neill researched and described a realistic average hit on an Island 3 as being not so beg a deal because while even losing one or more of the proposed windows would cause a full leak the amount of internal air volume would make loss take a long while and replacing such windows was determined to likely be a regular maintenance issue but not a catastrophic issue. For larger issues the plans for the colonies was to keep the length-wise transports available to all and no more than a few minutes ride to the escape ports at the ends plus the High Frontier book describes how the lengths would be set so that even if power loss occurred and individual physical mobility was required (aka running like a chicken with it's head cut off) the distances to locks would be measured in minutes.

But if you got a big ol' un-hollowed Dandridge Cole hard rock hitting you square then it might just be a Hollywood movie event.

Guess it all depends on the size of the object, the impact angle and location of the impact on the colony, the size and type of the colony (in O'Neill terms that's an Island 1, 2, 3 or Stanford Torus... or a modular Job Shop or a now-lost-to-us arrangement of pressurized SSMEs).

Big lingering fires would likely be out of the image - except for games and movies, just as they are allowed to make big boomy noises in a vacuum for effect - but aside from that I guess it's all up to how jarring you want the images to be.

In reality - High Frontier Concept reality - it is a great thing to keep top-of-mind for designers. Perhaps every structure in an O'Neill colony would be modular with the lower "floor" that ties into the shell being an enhanced escape pod. No need to run to locks if all you have to do is bring in the cat, close your doors and when the impact is over look out the window and wave to your friends in their free-flying houses. Then it's drag them back together and lock them back in place... kind of like using the lunar slag to make big lego bricks instead of a seamless outer shell (or, for folks from Seattle, making it like the Floating Bridge out from Yarrow Point, when the big storms come it breaks apart, when the storms are over they bring out barges, grab the floating pieces, snap them back together and the cars start driving across again)

Nothing is perfect even with perfect design though, we used to have two big buildings in New York and Titanic was unsinkable. However, the Titanic didn't go down in seconds but the movies made many individual human parts fast and exciting so there's challenge in a game and in life to get past the short difficult moments but still make the entire event less totally destructive than the half-second complete destruction of the death star... unless the reason for the event itself is to cause randomized debris for a 1st person game's cockpit level of flying through the mess and maybe picking up folks in bottle-suit mini-pods.

Guess it's up to you. Can't wait to see it!
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#3
Hey, thanks for jumping in!

You're right, the question of "what should it look like in a game" might be different from "what would it look like in real life," but this is the Real Space sub-forum so here I'm interested in what it would actually look like.

I'm assuming the impactor isn't all that big, but it's traveling at a very high relative velocity.  (This seems reasonable to me because if it were big enough to wipe out the colony, we hopefully would have known about it years in advance and would have done something about it long ago.)

I think you're right that a hole a few meters in diameter would be an emergency, but not a colony-killing event.  I'm going to actually calculate the rate of air loss, which I haven't done yet (but here's the math if anyone wants to try!).  But I suspect it's going to take hours to lose half the air.  So, plenty of time to dispatch engineering crews to patch things up, but you probably shouldn't procrastinate.

But that still leaves the question of what the hole would look like.  If it doesn't actually penetrate, I'm pretty sure I know the answer: it would look like a crater.  But if it goes through?  I think it would simply be a crater that's torn through on bottom.  I doubt the 1 atmosphere or less of air pressure would make much difference over the split-second that the metal was hot enough to flow.  But I'm only guessing.  I still hope we can find a more definitive answer!

Joe Strout
Lead Developer, High Frontier

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#4
(03-24-2016, 12:10 PM)JoeStrout Wrote: ...

But that still leaves the question of what the hole would look like.  If it doesn't actually penetrate, I'm pretty sure I know the answer: it would look like a crater.  But if it goes through?  I think it would simply be a crater that's torn through on bottom.  I doubt the 1 atmosphere or less of air pressure would make much difference over the split-second that the metal was hot enough to flow.  But I'm only guessing.  I still hope we can find a more definitive answer!

The absolute way to know is to find a way to test a mock.  Yeah, a really good computer model can go pretty far but seems to me that some companies and agencies learned a lesson from scrapping their actual wind tunnels in a rush to embrace the power of the simulation.   

There's that NASA guy who is in every documentary showing his giant NASA impactor slamming a pea into a dish of salt to demonstrate craters and ejecta (if you collect documentaries you have seen him go from brown hair to white and still that same machine is doing the tests and making the most understandable images).

O'Neill started with the Math but then moved to bending tin and seeing the Mass-Drivers working said a whole lot more than just reading the equations.  I know, it's not the answer you wanted... but that IS the answer you will usually get from O'Neill's Space Studies Institute: "Make it!"  Let us all see it!  :-)

One good real world mock that can be touched would answer your needs and the questions of so many others.

If you're not worried about explosive decompression effects - darn - then I guess a quickie would be to point a .22 at a bent piece of layered sheet metals.  Or, if your structures are from lunar slag then using a some type of simulant or even a brick or carbon fiber ... or layers of them perhaps with some spacers for air pocket shielding. Testing that (safely kids, use lots of goggles and keep a far distance and best to leave it to an expert on a safe shooting range) would of course put heat on the bullet impactor due to air molecules in it's travel, but if you want to test with "rocks" of various types that won't melt like lead then you can use a "wrist-rocket" professional slingshot instead of a gun.

My wife was working on a game a few years back and they wanted to know some certain things so they went to doctors and asked "let's just say someone's face... what would that look like?"  Some doctors took the consulting fee but in the end they just delivered photos.  Maybe instead of using a shooting range and renting a high frame-rate camera you could find similar images and videos already done ... but like Jack Whitesides Parsons use to say down in the arroyo: "It sure is fun to blow stuff up" :-)   
  
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#5
All fair points.  It's easy enough to find metal shot with guns: many street signs in rural parts of the country suffer just such damage.
[Image: bullet_holes_stop_signs_hd-wallpaper-235388.jpg]

And this is the closest analogue I think we're likely to find to a space colony hull holed by an impactor.  But it doesn't take air pressure into account.  Again, I think that won't affect the shape of the hole, but it's hard to be sure.

Also, you always have to be careful with scale tests... some effects scale differently than others, which can lead to surprising effects.  So scale test results should always be suspect unless you also have detailed theory to back them up.

Joe Strout
Lead Developer, High Frontier

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#6
(03-24-2016, 04:29 PM)JoeStrout Wrote: ...
Also, you always have to be careful with scale tests... some effects scale differently than others, which can lead to surprising effects.  So scale test results should always be suspect unless you also have detailed theory to back them up.

I guess it's a blessing and a curse that we truly don't know at scale... yet.

Logic says that a\the use of a high speed camera (the kickstarter for the FPS1000 has been calling to me) would give you a great deal of information for checking your rendered models with the exception of the effects of explosive degassing.  Space changes everything though and being stuck in a 1g environment does have some chaos impact but I think that at the speed of the event it is relatively minor at the small scale with the light masses of the test artifacts - it's close enough for the visual idea.

Air release after the event on a spinning habitat adds to the complete question also.  Debris with highest force of impact should be forced into the habitat and "up" toward the center where some of them will likely stay and bump around "in the air" since they are no longer trapped by the centrifugal force of the spin.  Other debris will "fall" back to the interior "floor", but will it fall out of the hole?  There's the effect of the speed of the spin and the amount of the force - if any? - that it creates at varying distances to add to the mix. 

And even the air molecules are effected by the artificial gravity of a spinning shell and are forced out of the hole so it's not just air pressure that would create the stunning, spiraling rainbows of ice emanating outward into space as the damaged habitat continues to turn. 

And that brings to mind the effect on the habitat's spin in relation to various masses and trajectories.

I know that you asked about the look of the hole, but my personal camera can't help pull back and see the grander view.

It really is an excellent question, so simple at first glance but so complex once you go down the rabbit hole.  And, because of our place at the bottom of a gravity well, so difficult to fully test until we get some kind of free-flyer SSI G-Lab running.

By the way, we just posted the March-April 1994 SSI Update newsletter at http://ssi.org/reading/ssi-newsletter-archive/ssi-newsletters-1994-march-april/  it has a four page article on Artificial Gravity and Moving Environments that is quite interesting.  Dr. Hall has written other documents on the subject (and SSI has other information in newsletters and in conference proceedings) but this quick one is a nice read that may be of interest to folks just getting "up to speed".
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#7
A big impactor (10 lbs) at relevant speeds (Mach 5-7) find rail-gun test videos. That is some UGLY impactor video.
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#8
A search for "hypervelocity impact" returned http://www.cbsnews.com/news/navys-newest-weapon-kills-at-seven-times-the-speed-of-sound/ which has a dramatic image of what a projectile at Mach 7 can do to armor plate. Some deformation of the plates, and a whole lot of vaporization. At the higher speeds of orbital debris collisions I'd expect even more vaporization.
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