[AR] Re: [UK OFFICIAL] Moon Express - HTP/kero
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Mon, 17 Jul 2017 10:51:04 -0400 (EDT)
On Mon, 17 Jul 2017, John Dom wrote:
Only exotic 100 % H2O2 has a FP around 0C, like water. ...
Right, still not OK in cold winters or near polar bases without heated
storage hangars. Neither in flight tanks during lunar (or Martian) nights.
Should the ice crack the tank walls, Houston 'dhave a big problem.
Also an issue with most other propellants, although often in different
ways. In particular, while peroxide has an obvious problem in that (like
water) it expands as it freezes, that doesn't mean that liquids which
contract as they freeze, like hydrazine, are free of problems! If it
contracts as it freezes, that means it expands as it thaws, which can be
trouble if thawing doesn't happen in quite the same order as freezing --
for example, if the middle of a frozen feed line thaws before the ends.
Thawing of a frozen hydrazine system -- not uncommon when a spacecraft has
lost attitude control (and therefore thermal control) for an extended
period, e.g. SOHO -- is done very gingerly, preferably very slowly, with
much praying and crossing of fingers.
Henry
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