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Light objects travelling at high velocity

Discussion in 'General Gun Discussions' started by 4v50 Gary, Jul 8, 2003.

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  1. 4v50 Gary

    4v50 Gary Moderator Staff Member

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    Well, the verdict is in regarding the Columbia. A piece of foam that came off the shuttle struck the leading edge of the wing at high spead, creating a 16" x 16" gap in the tile insulation. That was to prove fatal upon reentry.

    Now, didn't wildcatter P. O. Ackley prove the feasibility of fast light bullets many years ago? Turning to the 9mm v. 45, clearly the 9 mm isn't going fast enough.

    Hmmm, does this post have a point?:confused:
     
  2. benEzra

    benEzra Moderator Emeritus

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    Although I am firmly in the "light and fast" camp, I have to point out that the foam that hit Columbia's wing was only going about 530 mph, which is pretty close to the speed of a .45 ACP out of a 4" barrel, IRRC.

    Still, goes to show that even something light and soft going 530 mph is dangerous, particularly to a brittle substance like RCC.
     
  3. George Hill

    George Hill Member

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    I was going to joke about the grains of the foam...
    But considering the loss of the ship and crew?
    :(
    At least we know now.

    Damn.
     
  4. Steel

    Steel Member

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    Someone please educate me on what this "foam" is. I suspect it is not foam, to which most of us are accustomed.
     
  5. Nathaniel Firethorn

    Nathaniel Firethorn Member

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    It's polyurethane. Similar to the "Great Stuff" you can buy at Home Depot.

    It covers the External Tank and is used to keep the liquid hydrogen and liquid oxygen cold.

    Some years ago, NASA actually had problems with red-bellied woodpeckers, who thought that the external tank was a great place to build a nest. (They were right, but NASA didn't appreciate their tenancy.)

    http://www.orlandosentinel.com/news/custom/space/orl-asec-tankgraphic020303,0,7321813.graphic

    - pdmoderator
     
  6. TallPine

    TallPine Member

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    Do you have a link to an article announcing this?
     
  7. Nathaniel Firethorn

    Nathaniel Firethorn Member

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  8. Mike Irwin

    Mike Irwin Member

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    A piece of straw, at the proper velocity, can penetrate concrete block or a steel shell door.
     
  9. JPM63US

    JPM63US Member

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    The foam used on the space shuttle is not exatly "soft and squishy" and the tiles are not extremely strong either.

    That said, I remember seing pictures of straw embedded into wooden structures after a tornado.
     
  10. Keith

    Keith Member

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    The foam in question was frozen solid and sheathed in ice from the liquid nitrogen or CO2, or super whacked-out fuel (or whatever the hell it is) being pumped through all of those hoses.

    You can see that ice falling away on any launch. In this case, the foam itself broke away and carried a larger amount of weight than would normally be the case.

    The damage was due to kinetic energy rather than mere velocity...

    Keith
     
  11. Mal H

    Mal H Administrator

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    One thing that puzzles me about the experiment is how accurately their estimate is of the velocity of the foam piece when it struck the wing. When it broke off, it was going at the same vel as the shuttle/ET system. The only force to cause deceleration would be air resistance. At the altitude it had already achieved, air resistance is somewhat lower. So achieving a -550 MPH vel in the distance from where it broke off the ET to the wing is quite spectacular. Would we have even been able to see the foam piece if it was going that fast relative to the shuttle when it hit? Recalling the experiment where the foam was shot from the cannon, anyone see the foam piece before it hit the wing or after it hit? Nope, you're looking at the wing and suddenly a hole appears.

    I think the NASA folks know what they're doing, in fact I know they do, so I'm not all that worried about the problem. But, it is something to think about.


    Keith - Are you thinking about other launches other than shuttle launches when you mention the ice buildup? I didn't think the ET gathered much ice from the stored LOX as does, say, the Saturn. The foam is supposed to prevent that.
     
  12. Keith

    Keith Member

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    Mal,

    Watch a tape of ANY launch and as the engines roar to life, a veritable avalanche of ice falls away.
     
  13. MrAcheson

    MrAcheson Member

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    Keith,

    Air resistance and gravity. Gravity is a big part of it since it fell a significant distance. Still a deltav of 530mph seems really high to me.
     
  14. bountyhunter

    bountyhunter member

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    Yeah, but what pissed me off was that they knew exactly what happened about 30 seconds after it burned up. They showed the video from flight control at the time of the "incident" and the temp sensors were lighting up in the wheel well and wing as the thing was burning up. The sensors were telling the story before the crew even knew there was a problem. Amatuer video shooters saw the breakup and it was relayed to flight control almost immediately, and they went into damage control mode.

    They should have been straight with the public from the outset. The only reason it has been made public now is because there was video in the public domain showing the foam breakoff and the shuttle burning up into pieces. I think they behaved like a bunch of lawyers, and that's about the worst insult I can think of.
     
  15. bountyhunter

    bountyhunter member

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    You are correct. They are being deceptive about the velocity of the foam relative to the wing to try and not admit just how fragile the leading edge of the wing is. If they admit that, they are admitting how prone the spacecraft is to another incident of this type and that would require them to spend money and fix it.

    Back when the first major shuttle disaster occurred, NASA had actually published data on the probability of a major accident at something like one in ten million. That was disputed by engineers who are familiar with MTBF (mean time before failure) analyses of such systems. The numbers offered by such folks were more like one in one hundred. In retrospect, even that value seems to be optimistic.
     
  16. Mal H

    Mal H Administrator

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    Keith,
    Seriously, I don't think the ice buildup and subsequent avalanche happens with shuttle launches like it does with Saturns and Titans. I have watched many launch tapes and just watched a few more just to help jog my memory. There was no evidence of an ice cascade at launch or after.

    Think about this aspect of it, if a great deal of ice built up and remained on the ET, I can assure you the engineers would have devised a way for it to be removed prior to or just at launch. Wasting the fuel required to launch any extra weight is something they would definitely strive to prevent. With Saturns and Titans and Soyuz (oh my!), the ice comes off in sheets seconds after main ignition from the initial engine vibrations.
     
  17. Nathaniel Firethorn

    Nathaniel Firethorn Member

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    The ice cascade at T=0 does happen. But the ice has relative velocity of zero to the vehicle. Apparently the foam got decelerated by drag to 500-umpty mph relative. Big difference.

    Some enterprising person could check the velocity of the foam themselves from the videos. It's impossible to be deceptive about it.

    - pdmoderator
     
  18. RVSinOK

    RVSinOK Member

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    Just out of curiosity, do we know how fast the shuttle was going at the time the insulation came off? I don't remember how far into the flight it was when it happened, but I do know that the shuttles accelerate pretty dang quickly! If the shuttle was moving at 1500 mph or something, a delta of 500 might be a little more believable. I know I wouldn't want to stick my arm out the window at those kind of speeds!

    Just a thought......
     
  19. Bainx

    Bainx member

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    bountyhunter......what really pisses me off is the fact that NASA saw the foam do its damage real-time as it happened and did not abort.
     
  20. 280PLUS

    280PLUS Member

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    problem is,,,

    once they light the fuse on that thing, theres no turning back, you can't just shut it off...

    ive always thought nasa should spend the time and money to develop a capsule that totally protects the crew in all failures, regardless of how catastrophic, and can return them to earth if need be

    and then design a spacecraft around it.

    now lets get this straight,,,

    we take our best and brightest

    put them on a great big bomb

    light it, and once we do if one, just one tiny flaw turns up somewhere

    theres no way to save them?

    hello, what brilliant aerospace engineers dreamed this up?

    :rolleyes:
     
  21. MrAcheson

    MrAcheson Member

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    HAHAHA Abort? Once the shuttle is off the pad on liftoff? Because a wing was hit with some ice, which always happens on liftoff? Please. I understand NASA's decision. Abort of a shuttle launch at that point is probably as, if not more, dangerous than re-entry with unknown damage to the heat shielding.
     
  22. TallPine

    TallPine Member

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    No, they can do an RTLS (Return To Launch Site). I don't remember the time window for this, or how they separate from the boosters.

    Also, there is a sub orbital abort which lands them in Dakar, West Africa. This is why they have to launch by a certain time (around noon) Eastern time so that it is still daylight in Africa at the time of a possible abort/landing.
     
  23. Brat7748

    Brat7748 Member

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  24. benewton

    benewton Member

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    Brat:
    I've seen that info before, and I believe it.

    As noted by others before, PC can kill you.

    Believe it!
     
  25. benEzra

    benEzra Moderator Emeritus

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    RTLS is so dangerous that some astronauts question how likely the vehicle is to actually survive it, so it's a REALLY last-ditch effort. And all the other abort modes (TAL, AOA, or ATO) all involve a high-speed reentry, so that doesn't help you much.

    Also, the foam strike wasn't actually caught until the launch tapes were reviewed, I think the next day.

    As far as rigidity and ice buildup, that's always a possibility, but they were able to get a really accurate estimate of the size, mass, and density from the ascent video. (Telemetry tells you how fast the vehicle was going--probably in excess of Mach 3 at that point--atmospheric tables tell you how dense the air is at that altitude, and Isaac Newton gives you the numbers.)

    And if they were really trying to "cover up" how fragile the RCC leading edge panels are, blowing a hole in them on national TV isn't the way to do it. Face it, engineers make honest mistakes. In hindsight, the foam shedding SHOULD have been taken seriously, but let's not make it into a coverup.

    BTW, lots of good links on www.nasawatch.com, for those interested in an inside view of the agency.
     
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