And the only way to cool something in space is radiation, meaning the hot
side of the multistage refrigeration system is system needs to be as hot as
possible to shed the heat.
On Sat, Jun 16, 2018 at 11:03 AM William Claybaugh <wclaybaugh2@xxxxxxxxx>
wrote:
As I recall cyrocoolers for (liquid) hydrogen are about 20% efficient: 80%
of power input is waste heat....
Bill
On Sat, Jun 16, 2018 at 9:47 AM John Stoffel <john@xxxxxxxxxxx> wrote:
"Craig" == Craig Fink <webegood@xxxxxxxxx> writes:
Craig> On Fri, Jun 15, 2018 at 2:55 PM John Dom <johndom@xxxxxxxxx>
wrote:
Craig> Never mind SF_every great or small realization stems from
fantasy
Craig> concept(s), what else?
Craig> Maybe I missed it in previous emails on tankless solid H2
(protected by a
Craig> sunscreen) but how is such massive naked chunk going to be
launched to
Craig> orbit
Craig> or to space?
Craig> Some sort of levitation? Gun launch?
Craig> John
Craig> -----Original Message-----
Craig> From: arocket-bounce@xxxxxxxxxxxxx [mailto:
arocket-bounce@xxxxxxxxxxxxx] On
Craig> Behalf Of John Stoffel
Craig> Sent: vrijdag 15 juni 2018 17:37
Craig> To: arocket@xxxxxxxxxxxxx
Craig> Subject: [AR] Re: Orion-13
"Craig" == Craig Fink <webegood@xxxxxxxxx> writes:
Craig> Or, does the rock smash through all the layer of the Sun Shield
Craig> and into the blob of oxygen stored tankless like frozen like
Craig> block of concrete reinforce with a web of carbon fiber to add
Craig> strength but not weight. The Astronaut discovers that they have
Craig> only lots 10% of their Oxygen Supply, well within their reserves
Craig> to complete the mission as planned. Nothing a little Duct Tape
won't
Craig> fix.
Craig> What makes you think that frozen oxygen won't react and start
sublimating
Craig> and expanding rapidly when the heat from the pucture enters
this brick?
Craig> I think it will do exactly what your saying here, the
Craig> sublimation will continue until the temperature drops back to a
Craig> reasonable low vapor pressure is reached. But the difference
Craig> between a solid and a liquid is that, if the solid is too big
Craig> to exit the hole it will do all this inside the tank.
And pretty soon the tank will NOT be big enough to hold the volume of
gas and you'll get an explosion. You need to read up on steam boiler
explosions.
Hmm... looking at this diagram, maybe it's NOT as bad as I think. But
I also haven't found the properties of how much oxygen expands from
solid to liquid to gaseous phases. Looking at this diagram:
https://www.jaea.go.jp/jaeri/english/press/980624/ref02.html
seems to confirm that it will pretty much goto liquid first, then
gas. But with low low pressure, it might goto gas right away. Hard
to say.
Craig> The bulk of the stored oxygen is still available for use after
Craig> repairing the tank. Whereas a liquid is mobile and the sudden
Craig> decompression leads to rapid boiling throughout the liquid. The
Craig> liquid is going to quickly leave the tank, then freeze, then
Craig> sublime down to a "shelf stable" temperature at a low vapor
Craig> pressure. The bulk of the stored oxygen just left is a
Craig> brilliant blizzard of oxygen snow, like the Apollo 13
Craig> Astronauts witnessed.
That blizzard was *outside* the tank and quickly sublimated into space
since the pressure was so low, i.e. vacuum. How are you proposing
that people go and recover this snow?
Craig> And how, pray tell, do you plan on keeping this brick COLD in
the first
Craig> place? You need to bring it down to *at least* 56.2 degrees
Kelvin. And
Craig> keep it there. How do you propose this to be done?
Craig> It's driven by the vapor pressure temperature curve. Definitely
Craig> going to have active cooling to freeze it to begin with, on a
Craig> long trip Astronauts are going to need a flow rate of oxygen,
Craig> so it's going to take a vacuum pump/compressor to get the
Craig> pressure up from near vacuum to atmospheric pressure to
Craig> breathing or burn in an engine. If the vacuum pump is pulling
Craig> a lower vacuum than the solid's current vapor pressure, it acts
Craig> as an air-conditioner keeping it cool through
Craig> sublimation. Heaters to liquefy and pressurize the tank just
Craig> before a big burn. But, for long term storage (months or years)
Craig> before it is needed, a solid is much more stable.
I don't believe you. Or maybe you're assuming people are all way away
from the sun and it's heating? Like interstellar space? But still,
the heat from the liviing quarters at 280-300 deg Kelvin will be a big
source of heat to be absorbed by this chunk of oxygen.
Craig> Now if you want to speculate on how to design a rocket with
current
Craig> technology for reliability and tolerance to damage (either
self inflicted
Craig> like Apollo 13 or external like you propose) then do so with
at least
Craig> *some*
Craig> BotE calculations and assumptions that pass the smell test.
Or the *buy at
Craig> the hardware store* test.
Craig> Currently, on the ISS, the oxygen isn't stored as a liquid or
bleeding edge
Craig> like a solid, but as a gas.
I wonder why they do that, if solid storage is so darn good?
Craig> https://www.nasa.gov/content/
Craig> air-supply-high-pressure-tanks-ready-for-space-station
Craig> A tank failure of one of these will look quite different than a
Craig> blizzard of oxygen snow out the window. A 6000 psi oxygen
Craig> rocket launch inside of the Space Station? I wonder what the
Craig> NASA study showed. The failure study, not one showing it
Craig> statistically improbable.
I'd rather depend on actual examples with blocks of solid oxygen
having bullets fired into them for my tests. While I'm quite a
distance away of course.
I think you're seriously under-estimating the cooling needs. Have you
gone up on the roof of your office building and seen the size of the
equipment just to cool things down to 65degrees? The size and weight
are NOT trivial. And that's just to 280 kelvin. Now go another 250
degrees cooler.... how?
John
