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The problem of liquefaction of air for spaceplane
Path: santra!tut!draken!kth!mcvax!uunet!husc6!ukma!tut.cis.ohio-state.edu!unmvax!polyslo!jmckerna
From: [email protected] (John McKernan)
Newsgroups: sci.space,sci.space.shuttle
Subject: Re: In-flight liquification of air
Keywords: How do you do it?
Message-ID: <[email protected]>
Date: 13 May 89 08:38:34 GMT
References: <[email protected]> <[email protected]>
Reply-To: [email protected] (John McKernan)
Organization: Cal Poly State University -- San Luis Obispo
Lines: 43
Xref: santra sci.space:9798 sci.space.shuttle:2562
In article <[email protected]> [email protected] (Lucius Chiaraviglio) writes:
> How is liquification of air to be done without the use of horrendously
>heavy equipment and huge energy expenditure? (It seems that both would be
>needed to liquify air, especially at the rate that would be needed.)
> Also, since air is only 21% oxygen, storage of liquified air would be
>quite wasteful of weight and space.
Air liquification is an approach the Japanese are taking in their aerospace
plane project. The whole point of such a plane is to drastically increase
performance over a rocket engine by using the oxygen in the air instead of
carrying all your oxydizer with you. So no, the plane would not carry
liquified air. The plane uses liquid hydrogen (its fuel) to liquify the air.
This is necessary because the engine operates at too high a pressure to
practically pump enough normal air into it.
The US aerospace plane project (NASP) is trying to build a scramjet
which uses carefully shaped scoops to bring air into the combustion chamber
without liquifying it. This requires speeds of around 2000 mph before the
engine will operate properly (fuel is liquid hydrogen), so another
engine/rocket must bring the plane up to that speed. The scramjet is
supposed to propel the plane all the way to orbital velocity (17,500 mph).
One major problem is that the hottest parts of the scramjet would be over
5000F (!), and the highest temperature jet engine parts currently built can
only withstand 2800F. I've read that this project is currently using over a
third of all the supercomputer time in the US. It comes as no surprise that
the military is interested in a jet with a top speed of 17500 mph, so the
project is funded by the military at 300 million a year.
The Germans have a somewhat different concept, though I don't know if it's
actually funded at this point. They use an airplane to carry a shuttle to
19 miles and 4500 mph, and then the shuttle separates and uses rockets for
the additional 13000 mph and 80 miles of altitude. This has the advantage
of requiring only current technology. Still, it doesn't seem very cost
effective to build a plane capable of carrying a shuttle to 19 miles and
4500 mph (not an easy plane to build) and then still have 80 miles and
13000 mph to go.
Note: This information is from an artical in the LA Times 5/8/89.
John L. McKernan. Student, Computer Science, Cal Poly S.L.O.
-------------------------------------------------------------------------------
The future is rude and pushy. It won't wait for us to solve today's problems
before it butts in with tomorrow's.
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