Space Shuttle Foam Fixes

[mrmorris]

Of course -- another covering that comes to mind that might help would be a polyurethane sheath over the ET. The manufacturing process is well-established and the weight should be considerably less than that of the paint. <br /><br />*Edit -- just to be clear -- this would be to stop foam shedding, not to provide insulation as per the ET cozy.

 

[tap_sa]

<font color="yellow">"The idea was to whip off the cozy just before launch..."</font><br /><br />I think you underestimate the power of -253C cold metal to condence humid Florida air. It's not just the water moisture, the oxygen gets condenced too <img src="/images/icons/wink.gif" /> Liquid oxygen on outside surface of the tank is bad.<br /><br />edit: Oops -253, not -273.

 

[haywood]

Why not go back to the "CFC" foam.<br />My understanding is that the CFC foam was much less likely to flake off than the non-CFC foam.<br />Environmental concerns?...rubbish. How many ET's launch in one year and for that matter would 15-20 more ET launches over the next 5 years cause significant damage to the ozone layer...No!<br />If no large pieces of foam ever came off the ET with CFC foam...and I realize that that may be hard to determine. then the fix is simple.<br />Anyway...congrats to NASA for being so vigilant. The increased surveillance worked.<br />

 

[askold]

They should stick the ET into a giant pair of Hanes panyhose. Use the no-run type.<br /><br />And leave the Hanes label on and charge Hanes millions for the advertising.<br />

 

[rlb2]

Their you go an old fashion nylon panty hose fix.<br /><br />Another reason for using netting if placed slightly embedded under the top coating of foam insulation is that there would be a short term insulation of the netting material that would be shielded for the 8.5 minutes the external liquid fuel tank is attached to the Shuttle during ascent. <div class="Discussion_UserSignature"> Ron Bennett </div>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>Why not go back to the "CFC" foam. <p><hr /></p></p></blockquote><br /><br />I thought they did -- <i>before</i> the recent Atlantis, Columbia, and Discovery foam shedding incidents. But I may be misremembering. Anybody remember if they abandoned the freon-free foam application process? <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>In addition, NASA would have to pay me royalties for inventing the concept. I'd be sure to pass along a small percentage of the money to you for your contribution in materials estimation materials though...<br /><br /><br />*edit * And the aerodynamics wouldn't be a problem. The idea was to whip off the cozy just before launch... <p><hr /></p></p></blockquote><br /><br />Ah yes, it was you who came up with the idea!<br /><br />I remember for a while we were talking about tying the tail of the yarn to the pad so it would unravel as the vehicle ascended. <img src="/images/icons/tongue.gif" /> Although that probably wouldn't work (the yarn would have to endure prolonged immersion in the SSME and SRB exhaust, and probably scares the blazes out of astronauts anyway), it's a very comical image. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[tomnackid]

The only reason the foam causes damage is because the tiles are so fragile. The tiles are fragile because they have to be light weight. They have to be light weight because the orbiter is so big. The orbiter is so big because the Air Force demanded it (and the Air Force abandoned the shuttle after Challenger--can you say "irony").<br /><br />Most of the problems can be solved by having a smaller, lighter orbiter with a more robust heat shield--obviously not a near term solution, but probably the best one. <br /><br />

 

[Testing]

Good morning Calli. I spoke with one of my customers yesterday regarding Freon. He stated that foam loss increased 150% after Freon was banned. Can't quote him, can't back it up with data. I believe him. <div class="Discussion_UserSignature"> </div>

 

[nacnud]

Does anyone still make CFCs in sufficient quantities for the foam?

 

[yurkin]

I think the best idea was discussed a year or so ago. The insulation all falls away or retracts just at the moment of lift off. After they launch its only added weight anyway. <br />No foam insulation no foam insulation problem.<br />

 

[mxm111]

I am not sure if the net will work. The goal should be to prevent the initial damage of the foam, not how to hold the pieces together. I believe if you already have the foam piece hanging on the Spectra, then it is only a matter of time when the temperature increases to such values that the net will brake. The surface needs to be hardened to prevent the very initial damage which leads to creation of the air pockets and so on. The other potential problem with the net is that it may create ripples of the surface due to different thermal expansion coefficients of the foam and Spectra. Though it is probably small, but even the small ripples can lead to the air pocket with known consequences.

 

[fortytwo]

1. A giant space blanket of suffcient insulation qualities that is dropped just before takeoff.<br /><br />2. Maybe the propultion system needs to be retired, not the shuttle. <br /><br />3. How about a giant refrigerator?

 

[tomnackid]

"Why not go back to the CFC foam?"<br /><br /><br />Apparently the chunk of foam that hit Columbia's wing WAS the original CFC foam. It is still used in areas of the ET where the new foam will not work.

 

[ehs40]

what if a shield of some kind of metal (im not sure what the right kind of metal would be good for this job) was put in between the et and the shuttle and came of with the ET i know this could cause payload weight problems but do they load the shuttle to is capacity every time it is launched?

 

[skywalker01]

Another possibility would be to add some chopped fibers (fiberglass, graphite, kevlar, spectra, etc.) to the foam as it is sprayed on.

 

[silylene old]

I already said, as a polymer chemist, consider using a replacement for polyurethane. Also work on the foaming process, adhesion promoters, surface priming agents and the curing process.<br /><br />I would not be a little concerned with added chopped fibers to make a composite, this may make the foam too resistant to tearing, and this could result in the loss of big huge slabs and pieces, as opposed to lots of very small pieces.<br /><br />The fix is to improve adhesion. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[aaron38]

So in all this myopic attention to the foam, what else are they missing that's waiting to go wrong.<br /><br />I'm convinced that the shuttle will fly one more time and that's it. The next launch, they'll see something else wrong that they weren't even paying attention to, they'll freak out and that'll be it.<br /><br />I'm saying there is a 100% chance that the fleet will be grounded after the next launch as well. They are now so risk adverse as to be completely paralyzed.<br /><br />They'd better come up with another way to complete ISS real quick, or else scrap it. 20 more years to complete the ISS won't work.

 

[cosmictraveler]

Can't they just manufacture a giant thermos bottle so that there's a vacuum beteween the two tanks? <div class="Discussion_UserSignature"> <p>It does not require many words to speak the truth. Chief Joseph</p> </div>

 

[Leovinus]

Leave a couple of the big guys behind and paint it anyway. It looks better. <div class="Discussion_UserSignature"> </div>

 

[silylene old]

<font color="yellow">How is the bare ET prepped before the foam is applied? I'm sure it's cleaned but could the surface undergo some treatment to aid foam adhesion? Anodizing or etching for example. <br /><br />The documentary I remember watching seemed most concerned with void free application but there was little information about the state of the surface it was applied to. <br /><br />Could it be "roughened" with an etching treatment and would that help adhesion? <br /><br />Would a spray adhesive help? <br /><br />Could you "bag" the tank and treat it like one does when tent fumigating a house? <br /><br />Could you thermally bond a different foam formula to the bare tank surface much like baking enamel auto paint? And could a thermal treatment help bake-out voids? </font><br /><br /><i>Exactly</i><br /><br />I don't know the answers to your questions. I don't work at NASA. But these are all the right questions to ask. Surface preparation, priming agents, and proper curing environment are key to gaining excellent polymer adhesion to metal surfaces.<br /><br />Linear polyurethanes are made by the reaction of a di-isocyanate with a diol. The choice of the spacer group in the di-isocyonate and the diol greatly affects polymer properties such as rigidity, tear resistance, adhesion, Tg, foaming properties. In addition, triols can be used to creat branch points in the polymer network which can add much strength. Varying the di-isocyante/diol ratio has huge effects on polymer properties, since this affects the nature of the end group (which affects adhesion!) and the polymer chain lengths. So the materials ratio must be kept exactly right on both macroscopic and microscopic levels. Otherwise weak areas can be produced in the polymer.<br /><br />Finally, if the uncured di-isocyanate is exposed to water (humidity!!) during application or curing, a side reaction can occur with can produce and amine group and a molecule of CO2. If enough of this happens, this causes two <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[vogon13]

It is clear to me, if not many others, that all of the foam on the external tank is now suspect.<br /><br />And it will remain suspect till it is proven safe. <br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[vogon13]

IIRC, tank is cleaned and primed prior to application of foam. Most of the square footage of foam is machine applied. <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[silylene old]

<font color="yellow"> tank is cleaned and primed prior to application of foam</font>The question is how well and uniformly is it cleaned? How is the cleaning agent removed afterwards? How is the tank stored after it is cleaned? How long? Do the surface adhesion characteristics change between cleaning and priming? Between priming and foam application? Etc.<br /><br /><font color="yellow">Most of the square footage of foam is machine applied. </font>Is the 2 component mix exactly right from the beginning to end of application? Is the first foam out of the nozzle "good"? How good is the two-component mixing? Etc. Etc. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[silylene old]

Branched polymers are usually stronger, at least at limited levels, because of extra chain entanglement. Too much branching can cause brittleness and shrink-cracking. Not that much effect of permeability. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>