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Radical Yellow Duck
2009-Jul-02, 10:17 PM
Gentlemen and Ladies,

First off let me wish you all a happy and safe 4th of July.

Ever since the Columbia disaster there has been a lot of concern regarding the shuttle being hit with medium to largish chunks of foam insulation from the external fuel tank. Such chunks have been shown to be capable of producing large holes in the leading edges of the wing and underside of the shuttle.

I would like to propose several options that I have not seen discussed, and ask you for your thoughts regarding them and their practicality.

1 - A mesh. Originally I thought that something akin to chain link fencing material could be wrapped around the insulation. Any insulation that broke free from the external tank would be either held in place by the mesh or cut into sufficiently smaller peices to no longer represent a threat of catastophic failure. As I revised my thoughts, I realized that a mesh made of something akin to kevlar, which has a greater strength to weight ratio than the original idea of steel might be a better solution.

It is my understanding that something similar may have been considered by nasa, but that the turbulance effects of varying the surface of the External tank would cause more troubles than it would solve.

If this is the case wouldn't having the mesh imbedded just below the surface of the foam, or perhaps giving the mesh covered foam a "skim coat" take care of such turbulance?

2- a paint job. When the Columbia was first launched the external tank was coated with a white paint. As I recall this was discontinued because of the weight of the paint, about 200 lbs or so. If we could develop a paint that had fibers in it we could provide a kind of "skin" to the outside of the insulating foam. I am envisioning something similar to "felting".

3- Fiberglass. Coat the outside of the insulation with a thin coat of epoxy and fiberglass. If needed then you could substitute high strength materials such as carbon fiber or something similar. What you are looking to do is to retain the integrity of the foam insulation. It only has to last about seven minutes or so, until the ET is seperated.

4- The handy mans secret weapon. Duct tape. Why not just lay some duct tape the side of the ET facing the shuttle. OK, high strength fiber, super adhesive, Nasa grade duct tape. Spread the aerodynamic stress from one small section of foam over a larger area.

Comments?

DrRocket
2009-Jul-03, 01:49 AM
Gentlemen and Ladies,

First off let me wish you all a happy and safe 4th of July.

Ever since the Columbia disaster there has been a lot of concern regarding the shuttle being hit with medium to largish chunks of foam insulation from the external fuel tank. Such chunks have been shown to be capable of producing large holes in the leading edges of the wing and underside of the shuttle.

I would like to propose several options that I have not seen discussed, and ask you for your thoughts regarding them and their practicality.

1 - A mesh. Originally I thought that something akin to chain link fencing material could be wrapped around the insulation. Any insulation that broke free from the external tank would be either held in place by the mesh or cut into sufficiently smaller peices to no longer represent a threat of catastophic failure. As I revised my thoughts, I realized that a mesh made of something akin to kevlar, which has a greater strength to weight ratio than the original idea of steel might be a better solution.

It is my understanding that something similar may have been considered by nasa, but that the turbulance effects of varying the surface of the External tank would cause more troubles than it would solve.

If this is the case wouldn't having the mesh imbedded just below the surface of the foam, or perhaps giving the mesh covered foam a "skim coat" take care of such turbulance?

2- a paint job. When the Columbia was first launched the external tank was coated with a white paint. As I recall this was discontinued because of the weight of the paint, about 200 lbs or so. If we could develop a paint that had fibers in it we could provide a kind of "skin" to the outside of the insulating foam. I am envisioning something similar to "felting".

3- Fiberglass. Coat the outside of the insulation with a thin coat of epoxy and fiberglass. If needed then you could substitute high strength materials such as carbon fiber or something similar. What you are looking to do is to retain the integrity of the foam insulation. It only has to last about seven minutes or so, until the ET is seperated.

4- The handy mans secret weapon. Duct tape. Why not just lay some duct tape the side of the ET facing the shuttle. OK, high strength fiber, super adhesive, Nasa grade duct tape. Spread the aerodynamic stress from one small section of foam over a larger area.

Comments?

I would imagine that such things have been considered, but I don't know this for a fact. You would need to take a close look a the aerodynamic heating profile and determine if the material that you suggest, in the location that you suggest would survive and maintain enough strength to do some good. Assuming that it would then your idea might work.

But recognize that aramid fibers have been used in external protection materials for rockets before, for a different purpose, and aeroheating can cause degradation. Skin temperatures can get pretty hot at high mach numbers -- 900 F or so might be in the ball park. If you stagnate the gas flow anywhere it can get much higher.

That foam is supposed to be ablative. The best solution would be to make it stick properly to the tank.

mugaliens
2009-Jul-03, 02:15 AM
Mesh (that sounds familiar...)

Paint job with fibers (hey, that too...)

Fiberglass - That's a novel idea, but even carbon fiber would be prohibitively expensive

Duct tape - again, too heavy.

How about an ultra-lightweight Tyvek-like sheath made from spider web?

John Jaksich
2009-Jul-03, 02:45 AM
Welcome to BAUT, Radical Yellow Duck--

I would suppose that if the administration could spend billions bailing out the economy and the like---it could also listen to NASA engineers more intently on the next generation of space craft.

Metricyard
2009-Jul-03, 03:02 AM
Welcome aboard Radical.

The easiest solution, in my opinion, is to do what NASA is doing right now, and that's to remove the vehicle from the side and place the payload/human craft on top. No need to worry about falling insulation, far less aerodynamic problems, and much cheaper to operate.

Don't get me wrong, I loved the shuttle, but it just didn't live up to its expectations.
Until there is a radical change in propulsion, any future shuttle type craft will just have to wait.

alienhunt
2009-Jul-03, 07:39 AM
why not take a page out of new science and employ the large-scale manufacturing of carbon nanotubes as a lightweight, extremely strong alternative that can act as a mesh. I have no means to test it, and I know large-scale manufacturing is a few years away, but with funding NASA could help make it reality much sooner.

I agree with the previous posters idea to move the human-occupied area to be above the insulation foam!

loglo
2009-Jul-03, 07:51 AM
why not take a page out of new science and employ the large-scale manufacturing of carbon nanotubes as a lightweight, extremely strong alternative that can act as a mesh. I have no means to test it, and I know large-scale manufacturing is a few years away, but with funding NASA could help make it reality much sooner.

I agree with the previous posters idea to move the human-occupied area to be above the insulation foam!

NASA fund a major textiles revolution? I don't think their budget is that big!

alienhunt
2009-Jul-03, 02:30 PM
but if there are already many scientists working with carbon nanotubes for some other purpose, I'm sure they can be persuaded to work with/for NASA to get their name out there and thus gain more funding for the project and for their own future projects. The entire world (well, the educated people in the world) know that carbon nanotubes have so far proven to be adept at doing almost anything we want and need. They are definitely the wave of the future, so why not invest heavily in it? If we can get the EU involved, or some other large group of people/countries that can put money towards it...

It doesn't have to be NASA's undertaking. I'm sure NASA could take something they see works in other applications and adapt it.. they're good at it.

DrRocket
2009-Jul-03, 05:16 PM
Fiberglass - That's a novel idea, but even carbon fiber would be prohibitively expensive



Carbon fiber is used in the cases of almost all large solid rocket motors. Not just used -- the cases are a carbon fiber/ epoxy composite and about 60% carbon fiber. It is not prohibitively expensive, but rather enables the performance needed in most applications.

The shuttle is an exception. It uses very old technology, which includes steel cases (for the solids) and PBAN propellant.

If the ideas would work (doubtful) then the use of carbon fiber would probably be quite cost effective.

Dispersing fibers in elastomeric material to create a tenacious char is established technology, and is used in may internal insulators for solid rockets. Kevlar is the customary choice. However, this technology would not help the shuttle main tank problem where the issue is foam insulation that does not adhere properly to the metallic substrate. So the problem is retention of bulk material, and aeroheating of a "net" or something of that sort would be a major design issue.

DrRocket
2009-Jul-03, 05:18 PM
why not take a page out of new science and employ the large-scale manufacturing of carbon nanotubes as a lightweight, extremely strong alternative that can act as a mesh. I have no means to test it, and I know large-scale manufacturing is a few years away, but with funding NASA could help make it reality much sooner.

I agree with the previous posters idea to move the human-occupied area to be above the insulation foam!

Carbon burns.

JustAFriend
2009-Jul-07, 12:53 AM
The ORIGINAL designs of the Shuttle were safer: No SRBs. Manned booster craft that would be piloted back to the runway.

NASA bowed to the Congressional powers to slightly cheapen the design and went with Thiokol's SRBs and foamed external tank.

You can still see the design models in the Smithsonian Air & Space Museum in a glass case just under the Skylab mockup and at the Dulles Udvar-Hazy Center. (been there many times)

Pic: http://www.flickr.com/photos/tgaw/2160566600/

mugaliens
2009-Jul-07, 07:01 AM
Carbon fiber is used in the cases of almost all large solid rocket motors. Not just used -- the cases are a carbon fiber/ epoxy composite and about 60% carbon fiber. It is not prohibitively expensive, but rather enables the performance needed in most applications.

While that's true, the post to which I was responding was talking about using carbon fiber matrix as a means of keeping the foam in check, and that would be prohibitively expensive, both in terms of the carbon fiber matrix itself, as well as the weight penalty, as it's the wrong application for that material.


Dispersing fibers in elastomeric material to create a tenacious char is established technology, and is used in may internal insulators for solid rockets. Kevlar is the customary choice. However, this technology would not help the shuttle main tank problem where the issue is foam insulation that does not adhere properly to the metallic substrate. So the problem is retention of bulk material, and aeroheating of a "net" or something of that sort would be a major design issue.

Spidey-net. Seriously - a sprayed "hair net" of spider silk might work, provided the heating of that net could be solved.

Thus, since carbon fiber isn't susceptible to the heating, figure out a way to intermix a temperature-resistant adhesive with a sprayed carbon fiber (microfiber, I should say, as we're emulating spider silk).

aastrotech
2009-Jul-07, 07:25 AM
Two reasons to use the insulation is 1 to prevent fuel boil off and 2 to prevent ice buildup.

1 Apollo managed to survive fuel boil off without the external foam insulation. If reduction of boil off is an economy measure Columbia shows it is a foolish economy.

2 Condensation ice buildup and fall off during launch is a very dangerous possibly fatal hazard. It can do more damage than foam falling off.

A solution to ice buildup without foam could be to shroud the launch pad in a cover of some kind and reduce the water content of the air inside before fueling. Then there wouldn't be a frozen condensation problem. The shroud would be dropped, removed or folded like some kind of umbrella or clamshell just before launch.

DrRocket
2009-Jul-07, 08:02 PM
The ORIGINAL designs of the Shuttle were safer: No SRBs. Manned booster craft that would be piloted back to the runway.

NASA bowed to the Congressional powers to slightly cheapen the design and went with Thiokol's SRBs and foamed external tank.

You can still see the design models in the Smithsonian Air & Space Museum in a glass case just under the Skylab mockup and at the Dulles Udvar-Hazy Center. (been there many times)

Pic: http://www.flickr.com/photos/tgaw/2160566600/

What data do you have that the original design was safer ?

The overall reliability statistics for liquids and solids are about the same.

Challenger is no exception. Those solids were used well outside of the conditions for which they were designed and to which they were qualified.

mugaliens
2009-Jul-08, 07:29 AM
Two reasons to use the insulation is 1 to prevent fuel boil off and 2 to prevent ice buildup.

1 Apollo managed to survive fuel boil off without the external foam insulation. If reduction of boil off is an economy measure Columbia shows it is a foolish economy.

Not really an economy measure, as other rockets aren't foamed, either.


2 Condensation ice buildup and fall off during launch is a very dangerous possibly fatal hazard. It can do more damage than foam falling off.

Yes, and that's the reason behind the main tank's foam.


A solution to ice buildup without foam could be to shroud the launch pad in a cover of some kind and reduce the water content of the air inside before fueling. Then there wouldn't be a frozen condensation problem. The shroud would be dropped, removed or folded like some kind of umbrella or clamshell just before launch.

That's an excellent suggestion, and since minimizing humidity is the primary requirement, this could be accomplished with little more than a thin plastic sheet a few feet away from the assembly, into which dry, inert gas such as nitrogen is pumped.

Of course that would require special breathing apparatus...

So just air-condition the air. Again, we're not looking to A/C it as in cool it. Merely reduce the humidity to very low.

captain swoop
2009-Jul-08, 08:43 AM
move the launch site to somewhere more Arid.

DrRocket
2009-Jul-08, 04:56 PM
Not really an economy measure, as other rockets aren't foamed, either.



Yes, and that's the reason behind the main tank's foam.



That's an excellent suggestion, and since minimizing humidity is the primary requirement, this could be accomplished with little more than a thin plastic sheet a few feet away from the assembly, into which dry, inert gas such as nitrogen is pumped.

Of course that would require special breathing apparatus...

So just air-condition the air. Again, we're not looking to A/C it as in cool it. Merely reduce the humidity to very low.

A significant part of the reason for the insulation is aeroheating. The solids are insulated with cork, which is a common material for external insulation. The main tank used a sprayable formulation. But in any case, some sort of external insulation is necessary. A fairly typical number for aeroheating temperatures on the outside of rocket bodies is about 900 F. If structural members were to reach temperaturs like that there would be serious problems.

BTW sparayable insulation is used on other rockets, particularly on nose cones (e.g. Pegasus). But whether sprayed or not, most rockets have heavy external insulation. I can't think of any large space launch vehicles that don't.

man on the moon
2009-Jul-09, 06:25 AM
{snip}
A solution to ice buildup without foam could be to shroud the launch pad in a cover of some kind and reduce the water content of the air inside before fueling. Then there wouldn't be a frozen condensation problem. The shroud would be dropped, removed or folded like some kind of umbrella or clamshell just before launch.

In order to prevent ice build up, the air would have to be fairly(really) dry. Would such arid conditions cause issues with the various hoses and gaskets? And would any leaked fuel form vapor that could then condense into ice, even inside the shroud? What about the breath from various technicians? Not to mention the challenges of building and airtight shroud of that size...

None of these are make or break, just food for thought.

joema
2009-Jul-09, 11:55 PM
The ORIGINAL designs of the Shuttle were safer: No SRBs. Manned booster craft that would be piloted back to the runway.

NASA bowed to the Congressional powers to slightly cheapen the design and went with Thiokol's SRBs and foamed external tank...

It's not that clear whether liquid-fueled boosters would have been safer. Liquid-fueled engines have their own catastrophic failure modes. They can be shut down, but this doesn't always prevent disaster -- in fact it can introduce new problems. In 1985, STS-51-F (ironically Challenger) was nearly destroyed due to a spurious in-flight engine shutdown.

The manned piloted boosters would have been gigantic -- a 747-size hypersonic vehicle with multiple propulsion systems. Staging velocity would have been around 12,000 feet per second.

During the Columbia accident investigation hearings, former shuttle program manager Bob Thompson discussed that. He said even if they'd had the funding to build the manned flyback booster, the entire project would have failed from technical risk. He thought even if it could have been built, the resultant per-flight costs would be even higher than today's design.

SpaceNutNewmars
2009-Jul-26, 06:40 PM
Anything done to the tank to add material takes away from the payload capability of the shuttles delivery system to orbit.
Many of the worst cases for foam debri have occurred under the conditions of cold weather and of multiple tank refuelings due to delays in launch.
The tank also usually sees at minumum a month of outdoors weather which can not be good for it as well.

Drbuzz0
2009-Aug-08, 12:20 AM
Anything done to the tank to add material takes away from the payload capability of the shuttles delivery system to orbit.


That's not necessarily a deal breaker in and of itself. Sure, payload capacity is an important thing, but since the Columbia accident, the shuttle has been flying with the arm extension, additional optic sensors and some basic repair tools and supplies. These have to weigh at least a few hundred pounds in total.

Taking a hit on payload could turn out to be worth it if it improves safety to the point that another Columbia is something we wouldn't have to worry about anymore.

If you're looking to send something on a round trip to space and back then payload capacity is meaningless if it doesn't make it back in one piece.