Shuttle fuel cycling?

PS:Lift-off ~~~~===>Yea for NASA!

> 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:

> 968e-b670d1357...@o9g2000prg.googlegroups.com:
> > 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

>> 968e-b670d1357...@o9g2000prg.googlegroups.com:
>>> 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.