For the first flight (or two) of the shuttle, the tank was painted white over the foam. Paint was later dropped as it added significant weight to the vehicle, diminishing the payload capacity.

More than 20 years down the line, perhaps it makes sense to revisit the paint issue.

Surely a thin layer of some kind of rubberized or epoxy paint would add weight, but--applied after foaming was complete--it would provide aerodynamic smoothing to the foam, as well as making the exterior of the ET slicker, making ice less likely to stick.

In hindsight we can see, as some did in foresight, that the shuttle was not what it was sold to us as--reliable, inexpensive transport to LEO. However, for the moment, it's all we have. I say paint it, and if NASA would like to get sponsors to pay to have their names on the ET, all the better...

remember, low bids rule

If the adhesion of the foam to the tank is so problematic maybe it's time to really study the foam-tank interface. For example, should the tank surface be sandblasted or otherwise roughed up to improve foam adhesion? Is there a possible thermal regime needed during all phases of foam application? Maybe the tank needs to cycle through various heat (or cool) stages as the foam is applied. Possibly the wrong foam is being used. Instead of a conventional polyurethane maybe there is a need to go to an isocyanurate. This would likely result in highly uniform cell structure in the foam which would help the thermal shock between the tank and the surrounding air. And I agree that some kind of thin paint-like coating could act as a snug wrap. It's really interesting to think that all of the engineering brains at NASA have not come up with something better in all these years and by so not doing have consistently put every mission at risk.

Why don't they just stretch netting over the foam? I would image a medium strength fish netting would do the trick.

Good idea! They could also make a smaller double hulled tank as well with higher pressure capacity, or line the inside of the tank as opposed to the outside.

Do your research people. The use of freon free foam was mandated prior to the crash by your federal government. It doesn't stick as well and has not blown up its last shuttle. Google it.

Pressure is irrelevant , the fuel is liquid.

That is completely true , the "foam flaking problem" did not exist before NASA switched to "environmentally friendly" foam.

Danwill:

Pressure is irrelevant , the fuel is liquid.

This is to watcher49

Each of you are absolutely correct in your own way. I am unable to elaborate on the specifics details however. Those who have been told to hush are probably afraid to come forward. The solution has been locked away for quite some time. Beauracratic Red tape has tied the hands of brilliant engineers; most of whom have fled to work elsewhere or in the movie industry due to frustration. Please expand your minds and think outside of the box. The complexities associted with extremes of temperatures vs. instability of certain compounds is not easy. Material Solutions to this problem were solved some twenty years ago. The reverse of "M3" has held the material solution for years. It is very unfortunate that negotiations fell short on this. Just think as a sound engineer are you really resolved to the belief that our best and our brightest have only been able to utilize "form"?Also, would you be resolved to believe that the core computer components until recently were using 486 processors, and also would you be inclined to believe that the hull of the NASA space shuttle is the lightest and strongest material that we are able to build in 2007. If in your hearts of hearts as an engineer you believe any of the previous statement you would be wrong on all accounts. There are huge contractual agreements which on one hand keeps the space programs wheels spinning, but on the other hand stagnats growth and intellectual endeavor. It is very sad because so many are caught in the Web and who have worked hard to create the space shuttle because they belived in it. It might be hard to believe this but somewhere someone is reading this and completely freaking out. Hint: Outside of the box - Magnetic ? Plasma ? Can't wait for NASA's canned response. Ooops!!! Composites /Molecular Molding? Must have slipped out. Remember this statement, that everything has a solution. It's a matter of which rock to look under, but some engineers are resolved to the idea that the impossible will never be possible. Too bad. Is the world still flat?

LOGIK ; I am willing to hear any reply , If you have heard of a better one I am completely "ALL EARS".

I am serious.

The answer my friends, lays not in a material solution at all, although 3M would rather not elaborate on the material solution. It was important to test solves to the problem that perhaps did not involve any known material at all. Hum.” Think outside of the box". Engineering minds at the time of this proposal where baffled at first. I wish I could say that this was a mystery solved here or by NASA however it was not. It was stumbled on to a half a continent away – Russia, by accident. If I told you what their engineers were trying to do you would probably laugh – It had nothing to do with shielding.

Privet !!! - Hello

The constraints were:

1.) What could provide shielding at insurmountable extremes in pressure?

2.) What could provide shielding at insurmountable fluctuations in temperature?

Magnetic fields to repel and shield any particle contact - Atoms were repelled and never have a chance to find gaps or holes which is problematic in all material solutions, except the 3M solution.

This is not a Star Trek solution – not sure how that force field stuff would work anyway. Believe me the magnetic field solution is real and it works. – Probably I would imagine that this is pretty confidential – RED Blanketed info. I’m not much for the SCI-FI stuff anyway. I’m an Engineer – Physicist. So I’m pretty inclined to proofs of facts. So not sure how long the “GOV” will hold on to this as I am 100% sure of it’s testing here, but only for Military applications at this time. The bottom line - There just isn’t enough money to do things right in the space program. Plus there are solutions to many problems that are caught in bureaucratic RED Tape due to government mandated restrictions, matters of National Security or contractual obligations. But, it we continue going our current route, we’ll need to keep a close eye on China. Mark my words. LOGIK out!

Liquid can be stored under pressure as well and is. In any case you did not even comment on the point made on foam being attached inside as opposed to the outside and the feasibility of double hulled tanks. I think that there are better ways to escape the atmosphere by varied propulsion systems used in sequence. It is a known fact that NASA has fallen behind the curve of technological advances.

Well, I am inclined to agree with Watcher49. For conventional purposes the doubled hulled approach would be feasible and logical. On the outside I would recommend that NASA engineers look at some way of actually bonding the foam molecules to the tank as opposed to just spaying it on or just gluing it. The inner chamber of the engines already use Electroforming on the inside of the tank; I would imagine that it is possible to do unless it's a cost issue again; but I don't think that it would be true in this case. The process would be similiar to nickel plating. - No pockets of air, no gaps. As for my previous solution. I am reserved to the fact that it will sit in it's test laboratory until 2025 - RED Tape. - Thanks Watcher49 for good solution,