chiaravi@silver.bacs.indiana.edu (Lucius Chiaraviglio) (05/12/89)
In article <1989May11.050951.11130@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >Japan investigates Liquid Air Cycle Engines (which liquify atmospheric >oxygen on the way up rather than carrying it all with them) for both >aerospace planes and conventional boosters. [. . .] 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. Am I correct in assuming that none of the liquified air would be stored (all used right away), and that liquid oxygen for use after leaving the atmosphere would have been loaded before launch? Or has somebody developed some light equipment for rapid separation of nitrogen from oxygen as well as liquifying air? -- | Lucius Chiaraviglio | Internet: chiaravi@silver.bacs.indiana.edu BITNET: chiaravi@IUBACS.BITNET (IUBACS hoses From: fields; INCLUDE RET ADDR) Internet-gatewayed BITNET: chiaravi%IUBACS.BITNET@vm.cc.purdue.edu Alt Internet-gatewayed BITNET: chiaravi%IUBACS.BITNET@cunyvm.cuny.edu
henry@utzoo.uucp (Henry Spencer) (05/12/89)
In article <3961@silver.bacs.indiana.edu> chiaravi@silver.UUCP (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.) I don't understand all the details, but the heat exchangers Mitsubishi is testing simply use liquid hydrogen to cool the air. Liquid hydrogen is the fuel anyway, so it's around, and it is a *very* good heat sink. > Also, since air is only 21% oxygen, storage of liquified air would be >quite wasteful of weight and space. Am I correct in assuming that none of the >liquified air would be stored (all used right away), and that liquid oxygen >for use after leaving the atmosphere would have been loaded before launch? There has been talk of accumulating LOX on the way up, but I don't think the Japanese are thinking of that; they just want to run the engine on external air while they can. >has somebody developed some light equipment for rapid separation of nitrogen >from oxygen as well as liquifying air? Simply enriching the liquid in oxygen, as opposed to complete separation, should not be difficult, since liquid nitrogen boils at a lower temperature than LOX. In fact, with a well-adjusted heat exchanger the liquid will probably be oxygen-enriched to begin with, as the oxygen will condense first. -- Mars in 1980s: USSR, 2 tries, | Henry Spencer at U of Toronto Zoology 2 failures; USA, 0 tries. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
jmckerna@polyslo.CalPoly.EDU (John McKernan) (05/13/89)
In article <3961@silver.bacs.indiana.edu> chiaravi@silver.UUCP (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.