Shuttle Tank Foam FIX

[halman]

1207,<br /><br />I wonder if the materials science genius types could come up with an insulation material which would revert back to a liquid when a certain condition occurs, such as a strong acceleration, very small electric current, spraying with a catalyst, etcetera. This way, the insulation would perform its duty up until launch, then just run off the tank as it lifs off. (Maybe it would add pretty colors to the Main Engine exhuast!)<br /><br />I still would like to know the feasability of launching modules on Evolved Expendable Launch Vehicles, and collecting them with the shuttle to be hauled to the International Space Station. This would allow adding a few tons to the External Tank weight, if required. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[awuj2]

hey! Can anybody tell how much weight can be added<br />to ET to prevent foam loss? (considering need for STS to carry ISS modules) - 10 tonnes? 2 tonnes? less ?...

 

[cuddlyrocket]

"I am of the belief that changing the way the system is used may be the only way out...."<br /><br />Unless the engineers can come up with some easy fix, I agree that this seems the only likely outcome.<br /><br />The foam is a danger on descent, but as far as I'm aware there is no concern to the safety of the Shuttle on the ascent. I think therefore that a likely solution is to launch and hope that, in the remaining 20 flights or so, there's no critical damage caused. This should be a reasonable hope - after all, the foam (which has probably always been coming off) didn't cause such damage in over a hundred flights. (And the loss of one more (unmanned) orbiter wouldn't stall the programme.)<br /><br />By 'critical damage', I mean damage that would prevent austronauts returning in an orbiter. With the new inspection techniques, we're not talking about losing a crew here. They would come down in some other manner.<br /><br />And if it was possible to modify the orbiters to allow automatic return, you might not even lose the orbiter even though it sustained sufficient damage on takeoff to make it unsafe to do a manned return.

 

[halman]

1207,<br /><br />Well, thinking outside the box is sometimes considered an asset!<br /><br />I am sure that none of the existing launchers can put the bigger ISS modules into the correct orbit. However, if the shuttle could be used as a third stage, by having the module boosted on an intercept course after the shuttle as acheived orbit, and I mean RIGHT after, because the shuttle would be hanging around in a very low orbit waiting for the module, the shuttle could collect the module with the arm, stow it in the payload bay on supports specific to the module, lock the module down electronically, (solenoid latches, that sort of thing,) and then do an OMS burn to reach the ISS orbit.<br /><br />I seem to remember shuttle_guy saying that the heaviest ISS modules are really straining the capacity of the shuttle, not because of the weight, but because of the orbital inclination required. The tolerance is pretty critical, as I recall, which would possibly explain why there have been no additions to the foam in terms of restraining materials.<br /><br />If no foam loss is acceptable, then something radically different may be the only solution. Using the shuttle as a space tug to haul materials launched on another booster may be the only way to get the job done before the space station falls apart from neglect. And the deadline for shuttle retirement is approaching quickly.<br /><br />Which begs the question of how equipment is going to be returned to Earth for repair and restocking. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[drwayne]

Now why does that proposal sound familiar?<br /><br /><img src="/images/icons/wink.gif" /><br /><br />My only concern about automated return is that you might get a craft out of control at a bad time, resulting in ground issues. That is why my recommendation was for a destructive ditch, but, as always, there may be alternatives.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[plasticman]

I still like the "no-foam" solutions -<br />In addition to the removable cover (the styrofoam cup halves..), I like this one:<br /><br />Thermally heat the ET's metal exterior surface to above the icing point - right up to some time before launch.<br /><br />Outside of my area of expertise - so I don't know how much trouble this would cause inside the cyro ET tank...<br /><br />The FREON gas is used to do 2 things - 1 expand the foam, but you could CO2 for that, and 2- provide thermal insulation. The gas itself is trapped inside the Polyureathane foam, and itself is insulative. (In fact there are recycle/recovery means to capture CFC's from your refigerator foam...). The type of FREON gas can also effect the vitally (in this case) important cell size and its size distribution. It is well known that the earlier ozone affecting FREONS created better (ie smaller, more uniform) cell structures, generally (but they may have improved since I last looked at this).<br /><br />SG - do you know if there is experience with using Mylar (PET film) in any exterior surface during a rocket launch - just curious to see if NASA has explored its use during the high velocity launch --<br /><br />

 

[drwayne]

"Outside of my area of expertise - so I don't know how much trouble this would cause inside the cyro ET tank... "<br /><br />It would seem a lot, as previous discussions have mentioned, there are places where the outside of the ET is the outside the actual tank.<br /><br />I sense that people have started thinking of the foam as being primarily an anti-icing beast. The reality is that it is there to keep the cool stuff cool.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[plasticman]

Thanks for the links

 

[plasticman]

Some answers by NASA on the foam failure and the "netting" idea:<br /><br />http://www.nasa.gov/returntoflight/main/email_responses.html<br /><br />The cohesive failure mode is the one to be expected in any case - PU has excellent adhesive properties. Note they highlight another usually common problem in open atmosphere applied foams - voids !<br />

 

[drwayne]

"Our assessment is that the process of certifying a netting material for flight would take several years"<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[7419]

Maybe the primary reason the foam falls off is it's FOAM for Gnu's sake. I for one can see that if the ET had ever been hauled all the way to orbit for recycling into usable volume either for on orbit fuel storage or conversion to habital volume the foam problem would of been solved a long time ago. Most likely by inclosing the foam in a second skin of either Aluminum or some form of composite. In any non-manned rated STS derived unmanned HHLV of course the foam is not an issue and the loss of payload due to the possible second skin is in many ways minor. And I think any future STS derived HHLV will continue to use side mounting simply because the handling and launching procedures are in effect.<br /><br />As an aside I wonder just how much Delta V would be required to lower the ISS's orbital inclination to something closer to the Cape's latitude.<br /><br />new here, been lurking for a while

 

[lunatio_gordin]

What if the foam keeps falling off in space? have a nice debris cloud around your station...

 

[strandedonearth]

It takes a lot of delta-V to change inclination. I once asked SG how much dV it would take to go from the ISS inclination to an equatorial orbit, and while I forget the rough number he quoted, the answer was about half the dV needed to reach orbit in the first place! <br /><br />I keep thinking perhaps the best bet would be to place a shroud or fairing over the feedlines and cable trays, but that would take too long to certify, probably add too much weight, and would only fix that area anyways. Perhaps the best bet is to fast-track the Shuttle-C to carry up some/the rest of the pieces (possibly 2 modules at a time?), and then work on an inline SDHLV for the extra capacity for the VSE. I say Shuttle-C because the modules should require minimal if any mods to fly on it.<br /><br />Of course, I'm sure that has it's own set of problems and hurdles to clear....

 

[drwayne]

This is an interesting discussion involving Henry Spencer in this area:<br /><br />http://www.spacebanter.com/showthread.php?t=53983<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[drwayne]

Are you asking why the launch windows are what they are?<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[anotheridiot]

I'm sorry but the last shuttle took 15 tons?<br />The next shuttle is planning on taking 2 tons.<br />And we cant add a ton to get the shuttle to fly?<br /><br />When the choice is take 15 tons or dont go at all isnt it better to take 14 tons than not go?

 

[ltm_se]

Why not use the biggest of all ISS orbital modules waiting at the ground. Put two inflatable tanks inside for LOX and LH and replace the ET with the by nature were well isolated ISS module. On orbit. Simply remove the inflatable tanks and mount all needed equipment dock it to the ISS. I its to small. take two modules. Or a temporary halvsized ET inline with the module.

 

[ltm_se]

What if you changed so that the ET is instead two ET's (two smaller ones) with extra heavy robust isolation. Use fuel from the one closest to the SRB's in the beginning of the ascent. During SRB separation, separate the empty ET to loose some weight as compensation for the extra hardware weight of two robust ETs. Would that work?

 

[dwilson]

Ok, here it is.. lol.. maybe we are lookn at the wrong end of the microscope.. Following on the idea of shedding the foam safely at launch, instead of trying to keep it from breaking apart at all..<br /><br />I was reminded of a mechanical item that used to be just as hazardous when it would come apart in use.. In 2 stroke engines .. they used a set of reeds on a cage between the carb and cylinder.. this was used to meter out the fuel mix entering the engine and would open more fully as the rpms increase. In the beginning of this device the reeds were made of metal and were made that way to be more durable and last longer.. however too often these reeds would get damaged and get sucked into the engine and cause numerous problems.. seizure, piston disentegration, etc.. they went thru various fixes making the reeds and installation more sturdy but this only put more shrapnel in the engine when a failure occured.. then they came upon a fix.. they changed the reed material to a phenolic <spellling? /> reed that was like a plastic type of material.. more like a very thin piece of circuit board might be.. and they constructed the material with fibers that created a square lattice type configuration within the thin reeds.. they worked just the same.. but during failure would disintegrate to the small size of all the squares it was made up of.. and in doing so saved the engine from any damage when the pulverized reed would get sucked into the engine.. u would then just replace the reed and continue on.. <br /><br />So maybe the foam should be made to shred into tiny pieces on liftoff.. so small that they can do no damage and would look like snow.. that way tons of weight could be saved.. the system would remain in temp specs and no chunks would be large enough to do any damage.. a spray could be used on the surface to keep the FOAM PARTICLES in place until liftoff.. <br /><br />Just trying to stay out of the box figuring this out.. since the obvious fixes create catch 22's

 

[zenofjazz]

It seems to me that perhaps the problem is that NASA is trying to solve the wrong problem . If the problem is that the foam insulation falls off during launch, and can damage the orbiter, perhaps "hardening" the foam, is going the wrong way. <br /><br />Let me put it this way. Right now, the problem is that the foam (and any ice attached) breaks off, at high speeds, under acceleration, when it can do significant damage to the orbiter tiles. rather than trying to keep the foam from breaking off (which tends to lead to a situation where when you do have breaks, they're larger and harder), why not go the other direction entirely. A foam lining that is designed to shatter when the engines start, causing it all to fall off and drop to the ground at extremely low speed, before it can do damage?<br /><br />The primary purpose of the foam is to insulate the tank, but once launch is underway, the need for the insulation decreases significantly.<br /> <br />-ZenOfJazz

 

[drwayne]

"but once launch is underway, the need for the insulation decreases significantly."<br /><br />I wonder, is that really true? With ascent heating on the bare tank, what would the boil-off be? I know by definition the time of this boiloff would be limited, I just don't have a good feel for the numbers involved.<br /><br />I am *not* saying you're wrong, simply that I really don't know - which means I *can't* say you are wrong - right? <img src="/images/icons/wink.gif" /> <br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[plasticman]

Any breakage is bad news - period.<br /><br />To prove it, just take a range these items in size:<br /><br />Ball bearing<br />Pinball<br />Steel Billiard ball<br />1 foot chunk of concrete<br /><br />Go to your roof.<br /><br />Place your wife's or your mother's favorite china (ie ceramic) dinner plate on the concrete driveway.<br /><br />Drop items.<br /><br />See (and hear screaming) results -<br /><br />That is the correct way to think of foam falling in this situatin - <br /><br />nuff- said

 

[anotheridiot]

It just seems to be an adhesion problem. I just cant understand it. If you get a can of great stuff insulating foam that junk will stick to anything. Something else is wrong.<br /><br />Possibly stupid question, When they dump the 300,000 gallons of water to eliminate the echo effect and possible tile fracturing, the water turns into steam and it rises with the shuttle for a bit. Is that steam thawing ice that might not thaw otherwise and taking foam with it?<br /><br />

 

[plasticman]

.. and it is the cohesive (meaning tearing apart from within vs at the surface) that is the big clue that the little tiny cells (or bigger unknown/unchecked (?) voids) are the source of the cohesive tearing/fracture...

 

[drwayne]

"Those folks are experts in their fields."<br /><br />Let me give you another perspective on that. Having worked a program that had quite a few failures in early test flights, I have seen my share of renowned experts brought in for reviewing the program. I will tell you that they made some good suggestions and they made some of the most idiotic ones as well. And because many of them were aware of their stature as "experts", they would get really bent out of shape if you did not take their recommendations. Accusations/ recriminations/wailing and gnashing of teeth and the sort of stuff you would expect to see in an adolecent romance would follow. They would be proclaiming frm the highest mountains that the folks working the program were the most stupid fools god ever put on this Earth.<br /><br />Now, that is my experience. It is NOT on the shuttle, or even shuttle related. I just wanted to give a perspective that having a blue-ribbon panel raking you over the coals is not *always* an indication that you are doing something wrong.<br /><br />Wayne<br /><br />p.s. The program I am talking about kept having failures with little stuff like wires coming lose, things breaking etc., they were not the result of the operational design of the system. Yet most of the "experts" just wanted to redesign the whole system....very few good suggestions on - quality control! <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>