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The US Space Shuttle (google for "boondoggle") has a problem with losing insulation from the external tank while moving at high speed. Great deals of effort have gone into trying to tie the insulation more tightly to the tank so that it is not shed during flight.
I propose instead that the insulation
be very loosely attached to the tank, then moments after launch, just after clearing the tower, while the shuttle is still moving quite slowly, blow the insulation free and let it fall to earth. The tank should need little or no insulation during flight (it is only used for about five minutes) So leave it behind.
The insulation may hit the shuttle at this moment, but because it is moving so slowly it should cause no damage, and no worries of it separating later during high speed flight.
The insulation is needed during countdown, but should be completly unnecessary during flight. Somebody call NASA.
XCOR thermoplastic fluoropolymer composite
http://www.spacedai...ial_Aces_Tests.html
[Ling, Apr 18 2006]
Sound Supression Water System
http://science.ksc.....html#stsover-sound
There is a lot more than bubble bath being sprayed on the Shuttle. [reensure, Apr 18 2006]
Sublimation at high altitudes.
http://ga.water.usg...clesublimation.html
[Klaatu, Apr 21 2006]
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If the insulation were made from the highly flammable foam that catches fire at clubs, rather than fall away, it could burn away. The shuttle is immune to heat, so no harm done. It would be very impressive. People would be more inclined to spend tax money on launches such as this. |
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For added effect, the insulation could be impregnated with colorful metal salts to produce green, blue and magenta flames. |
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Sigh. I know most of my entries are farsical, but this is intended to be a serious suggestion. |
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Um, why did you post it on the Halfbakery in the first place, then? |
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The insulation, I imagine, is to stop ice forming on the tanks of frozen gas. Wouldn't that still be a problem as the rocket rises through the atmosphere? The air gets pretty steamy in Florida. |
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Oh, it is certainly half baked. But it seems that entries here are sometimes serious, but incomplete (as in this case) rather than purely silly, like Fuel Cell for Weight Control. Some are a combination of the two, like Safe Glasses for Drunken Fuckwits. |
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I kind of doubt that ice accumulation will be a problem during the less than five minutes that the tank is draining. But that is something for the big brains to calcuate. |
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Excellent idea that would translate directly into increased cargo capacity. An explosive layer directly on the tank would take it off--hopefully not five days ahead of time. |
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How would this scheme assure that no damage occurs? There's still going to be foam falling. |
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Did they determine that the foam hitting the leading edge of the wing was only a problem at high speed? I thought I remembered video of the foam falling while the shuttle was just taking off. |
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How long is the tank fueled before takeoff? Is the fuel and/or oxydizer cold before it begins to be depleted? |
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A piece of foam hitting the shuttle while it is moving slowly has little kinetic energy to impart. All worrisome incidents of foam shedding that I have seen occur after booster separation (3,600 miles/hr). |
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The tank is empty and discarded about five minutes after launch. And yes, it is stored at very low tempuratures. (Thus the insulation.) |
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In a discussion from 1994, Darrell Holloway says, “The foam insulation used on the ET serves to protect the ET and it's contents from the aerodynamic heating of ascent but in some areas it also protects the ET from the hot recirculation zone at the base of the LH2 tank where SRB/SSME exhaust gasses are a threat.” He ends up by saying that taking off the insulation (in space, in order to use the tank for habitation) was only “half baked.” Hah! |
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Ok, from that annotation it looks like some of the insulation needs to be kept on, probably mostly at the bottom of the tank. (where it isn't a threat anyway). You could still discard most of it. |
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<off topic> Later in that discussion, they say that the ET reaches 98% of the velocity needed to reach orbit. Since it weights 66,000 pounds, that seems like an enormous waste. |
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[Galby] - I am sorry if my suggestion about the colorful flames hurt your feelings. Now that I understand your intent, I will meet you halfway. The foam could fall off, _then_ catch fire! Alternatively, if the foam were encased in a flameproof outerjacket, one could burn the foam for fuel, providing added thrust. Shuttle launch attendees (and aficionados off site) could carve large space-associated figures (eg: the Hubble) from the foam then light them up when the shuttle launches and dance naked around them, whooping space-oriented chants! |
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OK, maybe that wasn't exactly halfway. But I am enthusiastic! Have a blue flaming space fish carved of insulating foam. |
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//I kind of doubt that ice accumulation will be a problem during the less than five minutes that the tank is draining. But that is something for the big brains to calcuate.// Heh. You'd think the entire problem would best be solved by the big brains, considering they know the exact requirements of the shuttle. They also have big brains, but there is little scientific evidence of a link between brain size and intellegence. |
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[Bungson] Ok, I will accept part way! Yeah, flaming chunks falling away would add some excitement. Maybe they could burn in the colors of the corporate sponsor of the launch. |
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[Worldengineer} Well if the brains are not used for thinking are they just for insulation? |
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Ice buildup would be a concern early in the launch. Overpressure due to frictional heating would be a serious concern later in the launch. |
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How do you figure that 100% of major failures have been due to insulation problems? Does anyone remember Challenger? (O-ring burn-through, resulting in flame jet impingement on the main tank) |
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//if the brains are not used for thinking are they just for insulation?//
The brain is for cooling of the blood, according to Aristotle. Today we know that he was wrong. The brain is for heating the blood. |
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[freefall] I shall add the word "recent". (Even though the o-ring failed due to improper installation of its insulation, resulting in a freeze) |
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AFAIK, the o-rings were installed properly, but the powers-that-be decided to ignore the input from the engineers, who stated in no uncertain terms that the o-rings, shrunken by the low temperatures, would be prone to failure. |
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Feynman gives an interesting account of the failure, in his book. If I remember correctly, he gave a report on the failure, and one of the comments that he made was that the philosophy of the shuttle test method was different from the aircraft industry. The aircraft industry tests individual items to destruction, so that working parameters are known before assembly, whereas the shuttle boosters, for example, were assembled and then tested. |
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Silly question: Why isn't the insulation put on the inside of the tanks? |
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It originally was inside of an outer shell. (which is the same as being inside the tanks.) The shell was added a not insignificant weight, so it was eliminated in the early 1980's |
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I don't think it is the same: If the insulation was on the inside, there wouldn't be any extra weight from a third layer.
This assumes, of course, that the insulation can work in that type of environment. |
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Insulation in direct contact with liquid propellants would be no insulation at all. |
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Because insulation only works with air pockets? Or you think it would chemically react? |
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Air pockets! Any air would condense into a liquid, and liquid hydrogen and oxygen would seep through the stuff and come into direct contact with the outer skin, where it would vaporize and blow chunks of the insulation into the tanks, which would then get sucked into the engines and destroy them.
Otherwise, it would work fine. |
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Is this insulation to keep the shuttle from burning up, or to keep it from freezing? I can't figure out what from this discussion. |
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On a morbid note, my science textbook last year had a picture of the shuttle Columbia being made, with the caption 'Space shuttles need insulation to keep them from burning up under high speeds' (or something like that). |
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[dbmage] The short answer is yes. Insulation on the ET serves three purposes. First it prevents the liquid hydrogen and oxygen fuel from vaporizing while sitting in the tank. Secondly it keeps ice from forming on the outside of the tank. Third it keeps the tank from overheating during the actual launch. |
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My suggestion is that the first two requirements are fulfilled by the time the shuttle has cleared the launch gantry and could be jettisoned. The third requirement I suspect could be fulfilled with much less insulation, perhaps none at all. |
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You could pump a continuous stream of bubble bath foam
over the tank while it's on the ground - bath bubbles
never knocked a hole in anything. Extract the
bubbles from a battery of baths on the top gantry
occupied by volunteer bathers. |
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interesting link, [ling], but it does not address the issue of the tank shedding external insulation at high speed. |
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Perhaps you are suggesting that with this, the insulation could go inside the tank, that might help, but then the tanks would have to be made bigger, and therefore heavier. |
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I was first asking: is there an insulation that could go inside the tank, but on checking around, all good insulation seems to contain air or vacuum. It seems even Nanopore material would absorb the liquid oxygen.
Then I saw the XCOR material which forms the insulation AND the structure, in a composite. |
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According to NASA, the Shuttles' external fuel tank carries about 5000 pounds of insulation, including sprayed-on foam, premolded ablator materials, the use of phenolic thermal insulators to preclude air liquefaction, and thermal isolators -- required for liquid hydrogen tank attachments |
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There's *got* to be a better way of going to space than that old thing. |
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/air would condense into a liquid, and liquid hydrogen and oxygen would seep through the stuff and come into direct contact with the outer skin, where it would vaporize and blow chunks of the insulation into the tanks, which would then get sucked into the engines and destroy them./ |
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This sounds great! You would want this whole process to start at liftoff. |
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Thinking about those tanks - I bet they get even colder on the outside after liftoff. Consider a handheld freon horn - they get frosty cold on venting the pressurized gas. Rising through the Florida dawn, I bet those tanks would accumulate quite a coating of ice. You would want to ditch the insulation once you were high enough that the humidity was low. |
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//The insulation may hit the shuttle at this moment, but because it is moving so slowly it should cause no damage, and no worries of it separating later during high speed flight.// |
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This is not true. The shuttle tiles are surprisingly fragile. I've had one in my hands and it crumbles like soft chalk. In fact, blackboard chalk is more substantial. |
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Some additional thoughts... |
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//The tank should need little or no insulation during flight (it is only used for about five minutes) So leave it behind.// |
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The shuttle is going along at 17,000 mph at 7 minutes 40 seconds into the mission. I'm not sure what you mean when you say the insulation is only used for about 5 minutes. At the 5 minute point, it's WAY past the tower. |
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[bungston] I don't care how cold something is, it is not going to accumulate much ice in the one to two minutes that the shuttle is rising through the lower atmosphere. |
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[zigness] I too have held shuttle tiles and I think you exagerate the fragility. They are not as sturdy as say a ceramic dinner plate, but they are stronger than gypsum sheetrock. Personally I would compare them to an old-fashioned plaster wall. A slow bit of foam should do them no harm. It is fast moving foam that has caused trouble. |
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[zigness] I am proposing that the insulation be discarded at the beginning of that burn, not at the end as it currently is (ejected along with the tank). |
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The tank is only used for five to seven minutes, I suggest that the insulation is not needed during this time. (The tank certainly is. |
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For some reason, every time I see this title I read it as "Ejaculate foam tank..." because of the way "Eject" and "Insulation" sit one on top of the other on my root page. |
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An HB entry about a rocket and almost a week before the first penis joke. I call that a victory for rationality. |
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I wouldn't consider it a penis joke so much as proof that I'm a pervert. |
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Ok, Penis/ejaculate reference. |
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Ice accumulation: A fine experiment for some Halfbaker with an experimental bent (emphasis on bent) and access to liquid nitrogen. |
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Question - In an uninsulated container (eg: empty pop can) how fast does ice accumulate in a humid environment. This could be done outside on a humid day, or perhaps in a closed bathroom during a hot shower. One could have a series of cans and weigh them before and after given periods of time. Alternately, different sized cans: ice accumulated (- nitrogen lost) could be plotted as a function of surface area. |
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I like this idea. I was concerned about ice accumulating and crashing into the shuttle. I found an interesting article on sublimation <link> which said that at high altitudes, that the ice would sublimate. Whether it would happen fast enough to preclude ice damage to the shuttle remains to be seen. [+] |
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