ET Thermal Conductivity

Question:

Is it possible that the change in thermal conductivity between the
alloy used to build the Lightweight ET and the Super Lightweight ET is
the cause of the increased cryopumping that has led to foam loss on the
recent tanks? My understanding is that the new aluminum-lithium alloy
has a much lower thermal conducticity than the old material. I was
thinking that this would result in more thermal energy from ascent
heating being trapped at the foam level, vs before when some of that
energy was transmitted into the tank via the aluminum alloy skin.
Likewise, the decreased TC causes the liquid fuel in the tank to not be
able to keep the trapped liquid gases within the foam as cool as before
during ascent, thus resulting in increased cryopumping and resultant
foam liberation.

NASA hasn't really been able to understand the mechanism for foam
liberation despite three years of intensive work on the matter, so I
figured maybe it was time to get some amateur brain power wokring on
the issue.


-Craig

wrote:
Question:

Is it possible that the change in thermal conductivity between the
alloy used to build the Lightweight ET and the Super Lightweight ET is
the cause of the increased cryopumping that has led to foam loss on the
recent tanks? My understanding is that the new aluminum-lithium alloy
has a much lower thermal conducticity than the old material. I was
thinking that this would result in more thermal energy from ascent
heating being trapped at the foam level, vs before when some of that
energy was transmitted into the tank via the aluminum alloy skin.
Likewise, the decreased TC causes the liquid fuel in the tank to not be
able to keep the trapped liquid gases within the foam as cool as before
during ascent, thus resulting in increased cryopumping and resultant
foam liberation.

NASA hasn't really been able to understand the mechanism for foam
liberation despite three years of intensive work on the matter, so I
figured maybe it was time to get some amateur brain power wokring on
the issue.


-Craig

Its a good theory since the loss got worse with the lighter tank.
Perhaps the lighter tank also flexes more?

Smart once and then dead lined.

Do you think DOW chemical has some involvement on "foam research" there,
buddy?

The NASA engineers have all been switchgrassed to the Mars Mission.


This USA is so foolish and ****ed up.

Thanks,

Rick

The NASA engineers have all been switchgrassed to the Mars Mission.
This USA is so foolish and ****ed up.


Can we *please* keep this an on-topic engineering discussion?

Thanks,
Craig

wrote in news:1151082016.385112.8260
@u72g2000cwu.googlegroups.com:

Question:

Is it possible that the change in thermal conductivity between the
alloy used to build the Lightweight ET and the Super Lightweight ET is
the cause of the increased cryopumping that has led to foam loss on the
recent tanks? My understanding is that the new aluminum-lithium alloy
has a much lower thermal conducticity than the old material.

The old alloy (Al 2219-T87) has a thermal conductivity of 121 W/m-K. The
new alloy (Al-Li 2195), as close as I can tell[1], has a thermal
conductivity of 102 W/m-K. That's lower but I don't know if I'd call it
"much lower".

[1] - actually listed as 0.243 cal/cm-s-C; I hope I got the conversion
right. Who says the metric system doesn't have unit conversion issues?
--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
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Jorge R. Frank wrote:

The old alloy (Al 2219-T87) has a thermal conductivity of 121 W/m-K. The
new alloy (Al-Li 2195), as close as I can tell[1], has a thermal
conductivity of 102 W/m-K. That's lower but I don't know if I'd call it
"much lower".


That's actually pretty substantial. Let me see if I've got this right:

LO2 Temp: 89.81K
Ambient Temp Outside Tank: 293.15K
k Old Alloy: 121 W/m-K
k New Alloy: 102 W/m-K

delta Thermal Energy Transfer= (121 W/m-K - 102 W/m-K) *
(293.15K-89.81K) = 3863.46 Watts per square meter

JRS: In article , dated Sat, 24
Jun 2006 17:01:54 remote, seen in news:sci.space.shuttle, Jorge R. Frank
posted :

[1] - actually listed as 0.243 cal/cm-s-C; I hope I got the conversion
right. Who says the metric system doesn't have unit conversion issues?

The calorie is not a Systeme Internationale init.

If people use a hybrid or out of date system, they must accept the
consequences.

--
© John Stockton, Surrey, UK. / ©
Web URL:http://www.merlyn.demon.co.uk/ - FAQish topics, acronyms, & links.
Correct = 4-line sig. separator as above, a line precisely "-- " (SoRFC1036)
Do not Mail News to me. Before a reply, quote with "" or " " (SoRFC1036)

Dr John Stockton wrote in
:

JRS: In article , dated Sat, 24
Jun 2006 17:01:54 remote, seen in news:sci.space.shuttle, Jorge R. Frank
posted :

[1] - actually listed as 0.243 cal/cm-s-C; I hope I got the conversion
right. Who says the metric system doesn't have unit conversion issues?

The calorie is not a Systeme Internationale init.

Note my choice of words. SI is a subset of metric. The calorie is not SI
but it is metric.

--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

The calorie is not a Systeme Internationale init.

If people use a hybrid or out of date system, they must accept the
consequences.

Let's face it, the most common failure mode in unit conversions is that
some
engineer assumed a particular measurement was in a particular set of
units,
when it was not.

Unit conversions are easy, even if your inputs are in furlongs per
fortnight.
Actually verifying all your assumptions is hard, and SI units solve
only the
easiest problems you might encounter.

JRS: In article , dated Sun, 25
Jun 2006 13:22:08 remote, seen in news:sci.space.shuttle, Jorge R. Frank
posted :
Dr John Stockton wrote in
:

JRS: In article , dated Sat, 24
Jun 2006 17:01:54 remote, seen in news:sci.space.shuttle, Jorge R. Frank
posted :

[1] - actually listed as 0.243 cal/cm-s-C; I hope I got the conversion
right. Who says the metric system doesn't have unit conversion issues?

The calorie is not a Systeme Internationale init.

Note my choice of words. SI is a subset of metric. The calorie is not SI
but it is metric.

One can understand a conservative reluctance to abandon the venerable
system of units which the States acquired when a part of the British
Empire. But it seems unreasonable then to use another obsolete system,
when the rest of the world has moved on.

AIUI, Abba Eban (1915-2002) once said, emulating a more pointed remark
attributed to Sir Winston Churchill, "Men and nations behave wisely once
they have exhausted all the other alternatives." It's about time that
the USA recognised that, in this respect and for technical matters, it
is time to move to the final stage.

--
© John Stockton, Surrey, UK. / ©
Web URL:http://www.merlyn.demon.co.uk/ - FAQish topics, acronyms, & links.
Correct = 4-line sig. separator as above, a line precisely "-- " (SoRFC1036)
Do not Mail News to me. Before a reply, quote with "" or " " (SoRFC1036)