Re: Shuttle ET foam shedding fix?
- From: Pat Flannery <flanner@xxxxxxxxxx>
- Date: Thu, 28 Jul 2005 13:58:23 -0500
Michael Gardner wrote:
The answer to pretty much all those questions is one word: Weight.ok, couple of stupid questions....
If air/evaporating liquid could escape without creating a bubble wouldnt it help eliminate large popoff areas? sure, it would mean putting in some path for gas to escape - some path not open to thermal transfer.....
Second, it seems a lot of the engineering stress is the result of insisting we have good insulation that can also fly at mach 4+. Understanding that it would add weight, if critical parts of the tank were covered in metal - the insulation choices and techniques become far simpler - and maybe lighter.
Sure you have to join the outer skin to the inner but there are ways to provide some thermal isolation, but still have a solid mounts.
All of this would of course require huge amounts to engineering, evaluation and testing so no quick fixes, but how long do we continue to try to "solve" what may very well be an unsolvable problem?
While I'm asking stupid questions - why is the leading wing edge RCC panel just one layer thick? Why not an air gap, then a second edge, perhaps even thicker that the first? It creates some backup for the first and if they do find damage and want to repair, it provides backfill for any patch.
No question we need to stop flying these things and have something better but I still think there are lessons to be learned other than "its time to stop flying".
To get the Shuttle to carry a useful payload they had to trim every pound off of the whole system that was possible, and that was one reason that the orbiter lost it's solid fuel escape rockets that could separate it from the ET while the SRBs were still burning, and its jet engines that could have greatly expanded its cross-range during descent, and might have allowed it to be flown back to the Cape under its own power if it had to land at Edwards due to weather (although that might have required some extra strap-on jets like Buran used during its runway tests).
The ET was a real problem in this regard, as it effectively is carried all the way to orbit by the Shuttle and is very large in size.
Put an extra thousand pounds of what-not on the ET, and kiss a thousand pounds of usable payload good-bye.
With added weight on the orbiter, you lost payload, increased reentry heating and G loads (same belly area hitting atmosphere, but higher weight), decreased cross-range (higher weight, but same wing area to support it in a glide) and increased landing speed, meaning it would need tougher landing gear with better brakes... which would add more weight.
There was also a major push to keep the overall cost as low as possible, although some of those very lightweight solutions probably added to the actual cost due to their cost of development over simpler technologies, while at the same time making the whole thing quite fragile due to its less-than-robust construction.
Pat .
- References:
- Shuttle ET foam shedding fix?
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- Re: Shuttle ET foam shedding fix?
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- Re: Shuttle ET foam shedding fix?
- From: paisley2
- Re: Shuttle ET foam shedding fix?
- From: Pat Flannery
- Shuttle ET foam shedding fix?
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