Space Shuttle Foam Fixes

[rlb2]

Sorry if I missed other people’s suggestions up to this point, I didn’t have time to read everything.<br /><br />That makes since and probably is of concerns to the Shuttle people, that’s why they must use a particular type of foam insulation that allows for expansion and not something even lighter but more rigid such as arrogell. Voids do have trapped gas under pressure would seem to be a problem going from 1 ATM to the voids of space.<br /><br /><font color="orange">sometimes engineers can become so focused, so overloaded with detail and imagination, that the simple, basic and logical can become lost or unseen. I understand that time and weight are huge factors here,<font color="white"><br /><br />I agree, sometimes the focus can be in the wrong area, but sometimes an idea that has a thousand reasons why it would work is struck down because of one main un-fixable reason why it wouldn't work. <br /><br />If weight is such a big issue then why does the Space Shuttle Orbiter which is designed to carry up to 65,000 pound payload into orbit not fudge a little for the safety of the crew if the foam fix is going to add just 1000 pounds to the weight to obtain orbital speeds??? Sure it will take more fuel, money well spent. I'm sure this same thought must have been brought up many time before but I would like to here the logic for the reason for this....<br /><br />How many times did the Space Shuttle Obiter cargo bay ever go up fully loaded to its maximum weight???<br /><br /></font></font> <div class="Discussion_UserSignature"> Ron Bennett </div>

 

[skywalker01]

<<Unresolved issue on this thread with fibres is the danger that this may just make bigger chunks rip away as the piece falling off takes more of the surrounding material with it. >><br /><br />I think a far more likely result would be for the fibers to hold the piece in place as the fibers would carry the loads from the broken piece into a much larger area, distributing the loads such that the load per unit area would be much less and well within the capabilities of the surrounding foam. <br />I also suspect there is an optimum fiber length that will take a little testing to determine.<br />It might also be worthwhile to try and orient a good portion of the fibers in the lengthwise direction on the tank so that any broken pieces of foam will hang on the fibers versus having the sideways fibers trying to tear their way out of the surrounding foam. But then again, if a high enough fiber fraction is used in the foam that probably wouldn't be necessary.

 

[plasticman]

Actually fibers would make the situation worse. The reason is that unless you are considering a mesh fiber fabric or filament winding, short fibers that can in fact be placed into th layup will embrittle the structure.<br /><br />The problem with the foam, is that most readers, and most of NASA think of it as foam.<br /><br />It is not foam.<br /><br />It is concrete and steel ball bearings... <br /><br />That is the better analogy at the low temperatures and high rates in the launch. Think of chunks of small concrete or bearings hitting ceramic tile (like the shuttle tiles, and the non-elastic "ceramic" RCC front leading edge).<br /><br />The foam can not be fixed and should not be used - another approach is 100% needed -

 

[plasticman]

As to the experts, I haven't seen one identified who has done research in high rate (speed, strain rate), low temperature, viscoelastic fracture of polymeric materials - which is the precise science related to the a) foam and long ago b) 0-ring Tg. So people advising glass fibers are not experts in this arena -<br /><br />The foam on the inside of "SOMETHING" makes sense - either make a double wall (they could have different thicknessess) - is plausible - a sandwhich thermos with a smooth high impact capable structure on the outside - ie steel or aluminum. <br /><br />Potentially a smooth filament wound structure might work but would be very expensive - <br /><br />I favored a double-walled insulator (there are also metal foams) as one approach - but they don't want the weight - hence, the idea suggested above of keeping the tank insulated with a pre-launch removable structure I like too -<br /><br />A clamshell styrofoam held around the tank and removed a half hour or so prior to launch -

 

[skywalker01]

So what is the big deal about making some sample panels of fiber reinforced foam on a small LH2 tank and testing them thru a simulated launch?<br />Try them with different fiber lengths, different fiber types, different fiber densities, and different orientations (including Z-axis). Try the fishnet that someone suggested too.<br />There is always a learning curve and even if none of these ideas work they could lead to ideas that would.<br /><br />So enough pontification and argument, how about some test data, eh?

 

[skywalker01]

Thank you.

 

[plasticman]

Essentially, yes - a temperture colder (or speed faster) than the engineers understood as far as the material properties.<br /><br />The saran wrap idea is just a toss - but frankly I like it better than what they did - which was not much.<br /><br />Better likely would be stretched high strength film - like PET, of which one form is Mylar - <br /><br />Still, it is rather easy to do the high strain rate, low temperature testing in the lab, and then again larger scale like the cannon shots of foam at the leading edge done to establish the foam-RCC failure. This type of testing has been done for over 30 years - essentially to look at bird strikes on aircraft canopies.

 

[gawin]

thier has been many interesting ideas through around in here from crazy to simplistic. and i honestly hope some engineers read this and start to actualy think.<br /><br />a couple of things are quite obvious at this point. <br /><br />1. yes they did cut down on the shedding but the part that they concintrated the most on STILL FAILED.<br /><br />2. They NEVER ran one single real world test on the improvements This is about the stupidist mistake they have made yet.<br /><br />3. if all they did was rework the same type of foam that isi n essence is 20+ years old then its obvious that the people involved need to try at least to work with some technology that is a couple decades newer.<br /><br />4. i cant seem to stress this point enough and thier are a couple of others here as well who see this. TEST what ever you try to do to fix it if the test fails try somthing else. DO NOT run simulations and calculations and say well it looks good on paper so lets launch and see what happens.<br /><br />i know i sound like im beating a dead horse with this one but as my background comes from the real world testing field ive seen to many disasters happen because some engineer "belived" his numbers were right and didnt need to be tested in a RW enviroment.<br /><br />gawin

 

[tomnackid]

From Jerry Pournelle's blog:<br /><br />"What ought to have been done with NASA's billion and a half was: (1) Hire a dozen smart people to design a condom for the Shuttle Tank. Peter Glaskowsky and I discussed this last night: surely the right material for the condom would be America's Cup sailcloth which isn't a cloth but a reinforced carbon fiber film, as light as anything made for its strength. Make a condom of that, encase the tank in epoxy and that condom, and foam chunks won't fall off. It might weigh a few hundred pounds, and so what? (2) use the remaining funds -- a billion at least -- to pay a bunch of small companies out there to work on SSTO, recoverable first stage rocket boosters, and air drop. Get each to build the best X project flying hardware they can build incorporating their approach for the $333 million each will get. Fly those ships. Observe the results and decide which concepts to encourage."<br /><br /><br />Go to http://www.jerrypournelle.com for the entire essay.

 

[wilmywood8455]

And so there it is............just read the NY Times article on the Lockheed Martin internal memo regarding the foam. When do you suppose NASA will start requiring contractors to share with them all information on contractors' employess, engineers, etc. who disagree with the contractors' company position on readiness? Shouldn't NASA be the ones who make the call on these concerns instead of a program manager down the food chain who is just looking to keep to a schedule? The ghost of Morton Thiokol lives. What a shame.

 

[anotheridiot]

I would like to see the outer shell around the foam. It would take less than trying to get foam on the inside of the tank in contact with the hazardous materials. Also what would a chunk of foam do to the fuel mixture if it gets caught in a filter and leans the mixture to liquid o2.<br /><br />What about just air space without insulation to an outer shell? If the outer shell condensated it wouldnt freeze.<br /><br />But the paint, back to the paint. It wasnt the fact that the paint kept the foam together that I found interesting, it was the fact that the foam would not become waterlogged while it sat on the pad. The waterlogged foam would freeze within the actual structure of the foam and would cause chunks to fall off.

 

[cyrostir]

why not make a metal shield that fits tight against the tank's belly, which is the closet part to the orbiter. anything that would come off would slide down past the orbiter and out at the bottom of the tank, airflow would be able to flow in between this shield and the tank<br /><br />please pardon the crappy drawing.....<br />just an idea<br />

 

[thetan1]

I'm not sure if anyone here is old enough to remember but the original design for the Space Shuttle had a second larger reuable Shuttle to do the inital boost phase of the space launch. This concept was scraped early on because of cost constaints. If this had been implemented we wouldn't have had this problem to start with. <br /><br />As for placing the foam on the inside of the tank. What the public sees is the external shell of the tank. There is a hydrogen and an oxygen tank inside the external cover. It seems to me that the insulation could be placed between these 2 surfaces and function well. I hope that the reason that this isn't being done, isn't because of monetary concerns.

 

[thetan1]

Shuttle_guy, have a look at http://www.nasa.gov/centers/marshall/images/content/119006main_External_Tank_Cutaway_5530x2060.jpg , it looks to me like there is a double wall.

 

[rlb2]

<font color="orange">Bill Gerstenmaier, the space agency official leading the investigation into the foam loss, said Thursday the shuttle's fuel tanks will need modifications, which eliminates any chance of launching in September.<br /><br />The next available launch window would be November. After that, NASA will have to wait until next year because of strict lighting requirements needed to photograph any flyaway foam or shuttle damage.<br /><br />"There's no immediate answer or problem that jumps out at us," Gerstenmaier said.<br /><br />Two days after Discovery's safe landing in California, Gerstenmaier told reporters that of the 4,192 pounds of foam on the spacecraft's fuel tank, only about 1.2 pounds came off at undesirable -- even potentially dangerous -- times.<br /><br /><font color="yellow">"Frankly," he said, "even the next time we fly the tank, I would expect to see a little bit of foam loss somewhere in the tank. I think it's an extremely difficult engineering problem to solve."<font color="white"><br /><br />http://www.cnn.com/2005/TECH/space/08/12/space.shuttle.ap/index.html<br /><br /><br /></font></font></font> <div class="Discussion_UserSignature"> Ron Bennett </div>