Li heat sink

Henry Spencer wrote:
Derek Lyons wrote:
The big problem is; How do you keep the heat in the shield from
penetrating to your crew/payload compartment after re-entry? That's a
lot of BTU's, and they have to go somewhere.

The whole point of a heatsink system, though, is that they don't have to
go anywhere in a hurry.

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. In the case
of John's vehicle, a plausible option is that the truck also starts
pumping cold deionized water through a set of built-in cooling passages at
the top of the vehicle heatshield, and venting the resulting steam.

Another alternative: dump the hot Lithium overboard and
let it burn up in the atmosphere, after re-entry is over.
Get rid of the heat and the weight, making landing easier.

Another, slightly less sane alternative: land using a
lithium / (insert-favorite-oxidizer) rocket system 8-)

"It's a heatshield! And a propellant! And great for those
unexpected mood swings on return to earth!"



-george william herbert

In article ,
Derek Lyons 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.

Works for a land touchdown at a prepared site. Questionable for an
unprepared site...

For an emergency landing at an unprepared site, you'd have to have some
other option -- dump the lithium overboard during descent, jettison the
whole heatshield, etc. -- but it's acceptable to sacrifice reusability a
little bit in that case.

(Note that the early Mercury capsules actually had this issue, in slightly
milder form, although it helped that they were not meant to be reusable.
The one potentially problematic case -- land touchdown -- typically would
write off the capsule immediately anyway, because the Mercury airbag
didn't handle even a small horizontal velocity at all gracefully. So it
was reasonable to just abandon ship once it stopped tumbling, and let the
heatshield warm things up if it felt like it.)

(And a water touchdown would be *really fun*.)

Doesn't seem to have been a problem for Al Shepard or Gus Grissom. The
outer face of the heatshield will be air-cooled fairly effectively once
you're down to low supersonic speed, and once down, you *may* have enough
water circulation to prevent actual boiling as the heat works its way out.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

(Henry Spencer) writes:

For an emergency landing at an unprepared site, you'd have to have some
other option -- dump the lithium overboard during descent, jettison the
whole heatshield, etc. -- but it's acceptable to sacrifice reusability a
little bit in that case.

Way back when they wanted to use a solar dynamic power system for the
space station, what were they going to use as a heat sink?

Weren't they going to use some sort of salt?

Would that possibly be more environmentally benign if it needed to
be dumped overboard from an emergency landing?

Phil

"Paul F. Dietz" wrote in message ...
...
Lithium hydride does even better.


According to this site:
http://www.mentallandscape.com/V_Lavochkin2.htm
the russians used lithium nitrate trihydrate as a heat sink on some of
the venera probes. Google reveals a number of similar applications.

Anyway you can use magetism or like to shunt the heat and such away?

What can you use glassified metal for? See April 2004 issue of
Discovery, got some
possible uses here!?

Mike


Henry Spencer wrote:

In article ,
Derek Lyons wrote:
The big problem is; How do you keep the heat in the shield from
penetrating to your crew/payload compartment after re-entry? That's a
lot of BTU's, and they have to go somewhere.

The whole point of a heatsink system, though, is that they don't have to
go anywhere in a hurry.

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. In the case
of John's vehicle, a plausible option is that the truck also starts
pumping cold deionized water through a set of built-in cooling passages at
the top of the vehicle heatshield, and venting the resulting steam.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

Abrigon Gusiq writes (after correcting his sin of
top-posting):

Henry Spencer wrote:

In article ,
Derek Lyons wrote:

The big problem is; How do you keep the heat in the shield from
penetrating to your crew/payload compartment after re-entry? That's a
lot of BTU's, and they have to go somewhere.

The whole point of a heatsink system, though, is that they don't have to
go anywhere in a hurry.

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. In the case
of John's vehicle, a plausible option is that the truck also starts
pumping cold deionized water through a set of built-in cooling passages at
the top of the vehicle heatshield, and venting the resulting steam.

Anyway you can use magetism or like to shunt the heat and such away?

No. Magnetic fields do not "shunt" or have any effect on heat per se;
they can only influence the motion of charged particles. Nor do magnetic
fields have any effect on the infrared radiation produced by the plasma sheath,
which represents the primary heat load on a re-entering spacecraft.
Finally, unless on is using superconducting coils, generating a strong
magnetic field would require an _ENORMOUS_ amount of power --- and a
re-entering spacecraft has very little power to spare, and very little
fuel and oxidizer left to generate said power with.


BTW, _PLEASE_ stop "top posting," and learn instead to use standard usenet
quotation style. Your quotation style makes your postings incomprehensible.
Example:

A: .backwards posting your read to readers your forces "posting Top"
Q: What do you mean by that ???
A: "Top posting" reverses the logical flow of the discussion.
Q: Why is "top posting" bad?


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

In article ,
Keith Harwood wrote:
(And a water touchdown would be *really fun*.)
Doesn't seem to have been a problem for Al Shepard or Gus Grissom.

I suspect that Derek was referring to the fun times to be had when the
hot lithium met the cold water.

They don't have to meet -- the lithium will be enclosed in some other
metal anyway. It sounded to me like he was talking merely about a
heat-sink heatshield meeting water... which has been done.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

In article ,
Abrigon Gusiq wrote:
Anyway you can use magetism or like to shunt the heat and such away?

No. People have played around with ideas like that for many years, but
nobody's ever managed to come up with something workable.

What can you use glassified metal for? See April 2004 issue of
Discovery, got some possible uses here!?

Maybe. Much depends on details.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

(Henry Spencer) wrote:

In article ,
Keith Harwood wrote:
(And a water touchdown would be *really fun*.)
Doesn't seem to have been a problem for Al Shepard or Gus Grissom.

I suspect that Derek was referring to the fun times to be had when the
hot lithium met the cold water.

They don't have to meet -- the lithium will be enclosed in some other
metal anyway. It sounded to me like he was talking merely about a
heat-sink heatshield meeting water... which has been done.

Well, yes and no. 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.

D.
--
Touch-twice life. Eat. Drink. Laugh.

Henry Spencer wrote:

In article ,
Keith Harwood wrote:
(And a water touchdown would be *really fun*.)
Doesn't seem to have been a problem for Al Shepard or Gus Grissom.

I suspect that Derek was referring to the fun times to be had when the
hot lithium met the cold water.

They don't have to meet -- the lithium will be enclosed in some other
metal anyway. 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.

Keith Harwood