#21
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Li heat sink
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#22
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Li heat sink
In article ,
Derek Lyons wrote: (And a water touchdown would be *really fun*.) Doesn't seem to have been a problem for Al Shepard or Gus Grissom. ...A Be heatshields thermal properties are quite different than the Li/Be system proposed here, and the mechanical details of the two systems are very different as well. I'd be hesitant in claiming that safe operation of one system 'proves' the safe operation of another, very different system. However, saying it "would be" really fun implies that it is definitely unsafe, which is not the same thing as merely having doubts. I never said it was proven safe; I merely noted that the situation isn't *inherently* unsafe, because heat-sink heatshields have done water touchdowns without great problems in the past. It's challenging, but perhaps not unsolvable. -- MOST launched 30 June; science observations running | Henry Spencer since Oct; first surprises seen; papers pending. | |
#23
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Li heat sink
In article ,
Keith Harwood wrote: ...It sounded to me like he was talking merely about a heat-sink heatshield meeting water... which has been done. I was thinking about accidents. That's not what Derek said, however. -- MOST launched 30 June; science observations running | Henry Spencer since Oct; first surprises seen; papers pending. | |
#24
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Li heat sink
In article ,
Mike Miller wrote: They don't have to meet -- the lithium will be enclosed in some other metal anyway. Probably thin metal, right? Trying to contain a friendly metal like lithium in a thin, flight weight heat shield would be an...interesting...challenge... Understand, I'm not saying it's necessarily easy, or even that it can be done with acceptable reliability. I'm rebutting an assertion that the situation is (essentially) inherently and inevitably disastrous. No, it doesn't *have* to be. "Challenging" I will accept. :-) -- MOST launched 30 June; science observations running | Henry Spencer since Oct; first surprises seen; papers pending. | |
#25
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#26
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Li heat sink
Gordon D. Pusch wrote:
However, none of these phase-change thermal storage materials have anywhere near the specific heat capacity that you can get by simply boiling water and venting it. And you really =DON'T= want to be _storing_ all that heat in the spacecraft, where it will simply cause problems later; you want to be dumping that heat overboard !!! Actually, I did once sketch out a design which did keep it on board all the way through the reentry interface. The point is that you don't really want to have landing fuel *and* reentry coolant. It's actually easier if your landing fuel IS your reentry coolant. When you want to land you just open a valve through some nozzles and phoooomf you land in a big cloud of steam and get to live today. Yhe landing is 'sporty'; but atleast you don't have to light the engine, and you'd know well before hand whether enough pressure is in the system for you to survive- if not, a parachute is recommended as backup. A slightly less scary approach would be to use a Roton style rotor, and vent the steam through that. -- Gordon D. Pusch |
#27
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Li heat sink
Henry Spencer wrote:
The basic answer is exactly what you see with the shuttle (which has quite a bit of heat stored in its tiles at landing time): one of the first things that happens after touchdown is that an air-conditioning truck is hastily hooked up to the vehicle to keep the interior cool. How warm would it get if the air-conditioning truck is not available, e.g. after an unscheduled emergency landing at an unusual location? -- Keith F. Lynch - http://keithlynch.net/ Please see http://keithlynch.net/email.html before emailing me. |
#28
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Li heat sink
In article ,
Keith F. Lynch wrote: The basic answer is exactly what you see with the shuttle (which has quite a bit of heat stored in its tiles at landing time): one of the first things that happens after touchdown is that an air-conditioning truck is hastily hooked up... How warm would it get if the air-conditioning truck is not available, e.g. after an unscheduled emergency landing at an unusual location? My impression -- I have no specific data -- is that cabin and cargo bay would both get unpleasantly hot, but not disastrously so. Enough to perhaps ruin biological specimens, not enough to damage equipment, is my understanding. -- MOST launched 30 June; science observations running | Henry Spencer since Oct; first surprises seen; papers pending. | |
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