Shuttle fuel cycling?

[Ken S. Tucker]

It's reported the recent Shuttle was fueled and unfueled
6 times, I'm not sure about the accuracy of that, but I'll
assume that's true.

Cycling the LH2 in and out etc. places quite a bit of
fatigue stress on the orange tank and it's insulation
cuz of geometric thermally induced variations.
Things like micro cracks in the Al tank as well as the
adhesion of the foam to the Al.

I presume there is some cycling limit, at which time the
unit is considered to be excessively fatigued?

Personally I got a bit worried at 6 recycles, but I don't
know the spec, I figure one does exist.
Ken
PS:Lift-off ~~~~===>Yea for NASA!

[Damon Hill[_3_]]

"Ken S. Tucker" > wrote in news:fecbb09b-7818-4c3e-
:

> It's reported the recent Shuttle was fueled and unfueled
> 6 times, I'm not sure about the accuracy of that, but I'll
> assume that's true.
>
> Cycling the LH2 in and out etc. places quite a bit of
> fatigue stress on the orange tank and it's insulation
> cuz of geometric thermally induced variations.
> Things like micro cracks in the Al tank as well as the
> adhesion of the foam to the Al.
>
> I presume there is some cycling limit, at which time the
> unit is considered to be excessively fatigued?

>From this source, the tanks are rated to 13 cryo loading cycles:

http://www.nasaspaceflight.com/2009/08/understanding-et-131s-rogue-foam-et-
132-confidence/

That does seem like a lot of cycles. It may be that the current aluminum-
lithium alloy is more forgiving of such stresses.

--Damon

[Ken S. Tucker]

On Aug 2, 7:53 pm, Damon Hill > wrote:
> "Ken S. Tucker" > wrote in news:fecbb09b-7818-4c3e-
> :
>
> > It's reported the recent Shuttle was fueled and unfueled
> > 6 times, I'm not sure about the accuracy of that, but I'll
> > assume that's true.
>
> > Cycling the LH2 in and out etc. places quite a bit of
> > fatigue stress on the orange tank and it's insulation
> > cuz of geometric thermally induced variations.
> > Things like micro cracks in the Al tank as well as the
> > adhesion of the foam to the Al.
>
> > I presume there is some cycling limit, at which time the
> > unit is considered to be excessively fatigued?
> >From this source, the tanks are rated to 13 cryo loading cycles:
>
> http://www.nasaspaceflight.com/2009/08/understanding-et-131s-rogue-fo...
> 132-confidence/
>
> That does seem like a lot of cycles. It may be that the current aluminum-
> lithium alloy is more forgiving of such stresses.
> --Damon

I wonder if the 'embrittlement' of cycling very cold liquid fuels
into something we regarded to be many times useable may
have been the nail in the VentureStar coffin, since it was
reported that propellant tank problems was a serious roadblock
to the unit becoming operational.

http://en.wikipedia.org/wiki/Lockheed_Martin_X-33

http://en.wikipedia.org/wiki/VentureStar

So the question is whether we have materials that will withstand
cyrogenic cycling, otherwise we'll need to look for higher temperature
propellants, with a likely reduced Isp for useability.
Ken

[Pat Flannery]

Ken S. Tucker wrote:
> On Aug 2, 7:53 pm, Damon Hill > wrote:
>> "Ken S. Tucker" > wrote in news:fecbb09b-7818-4c3e-
>> :
>>
>>> It's reported the recent Shuttle was fueled and unfueled
>>> 6 times, I'm not sure about the accuracy of that, but I'll
>>> assume that's true.
>>> Cycling the LH2 in and out etc. places quite a bit of
>>> fatigue stress on the orange tank and it's insulation
>>> cuz of geometric thermally induced variations.
>>> Things like micro cracks in the Al tank as well as the
>>> adhesion of the foam to the Al.
>>> I presume there is some cycling limit, at which time the
>>> unit is considered to be excessively fatigued?
>> >From this source, the tanks are rated to 13 cryo loading cycles:
>>
>> http://www.nasaspaceflight.com/2009/08/understanding-et-131s-rogue-fo...
>> 132-confidence/
>>
>> That does seem like a lot of cycles. It may be that the current aluminum-
>> lithium alloy is more forgiving of such stresses.
>> --Damon
>
> I wonder if the 'embrittlement' of cycling very cold liquid fuels
> into something we regarded to be many times useable may
> have been the nail in the VentureStar coffin, since it was
> reported that propellant tank problems was a serious roadblock
> to the unit becoming operational.
>
> http://en.wikipedia.org/wiki/Lockheed_Martin_X-33
>
> http://en.wikipedia.org/wiki/VentureStar
>
> So the question is whether we have materials that will withstand
> cyrogenic cycling, otherwise we'll need to look for higher temperature
> propellants, with a likely reduced Isp for useability.

They didn't have to worry about cycling in the case of the X-33; its
composite LH2 tank started falling apart right after they emptied it on
the first fueling test.
Even if they had solved that problem, they probably would have been in
for a very rude awakening the first time the VentureStar did a reentry,
as examination of the Columbia debris showed that when heated in a
atomic oxygen flow, titanium started burning at a lower temperature than
even aluminum, and the VentureStar TPS was going to rely on titanium
shingles rather than silica tiles like the Shuttle.

Pat