Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Fri, 30 Nov 1990 02:12:50 -0500 (EST) Message-ID: <8bJUND200VcJQ64E5J@andrew.cmu.edu> Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Fri, 30 Nov 1990 02:12:16 -0500 (EST) Subject: SPACE Digest V12 #593 SPACE Digest Volume 12 : Issue 593 Today's Topics: Re: Save our Shuttle data? NASA to use world's fastest supercomputer (Forwarded) Light bulbs, thorium, space applications Re: NASA Prediction Bulletin Distribution Re: Commercial Shuttle Proposals Re: NASA Prediction Bulletin Distribution Re: Photon engine Re: NASA Prediction Bulletin Distribution Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription notices, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: Sat, 24 Nov 90 00:19:38 EST From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. Subject: Re: Save our Shuttle data? >From: van-bc!rsoft!mindlink!a752@ucbvax.Berkeley.EDU (Bruce Dunn) >Subject: Re: Save our Shuttle data? >> sysmgr@KING.ENG.UMD.EDU (Doug Mohney) writes: >> [regarding the difficulties in reviving the F1 LOX/Hydrocarbon engine] >> Pretty bizarre to think we've come 20 years, with CAD/CAE and materials >> engineering and we can't build something which was put together in the '60s. >> Kinda scary. > However, there are other examples of the difficulties in replicating old >technology. Old does not mean non-sophisticated. We are still struggling to >reproduce the playing qualities of centuries-old violins. >...There is often a lot more art in engineering >than the textbooks would indicate. >Bruce Dunn Vancouver, Canada a752@mindlink.UUCP It has been implied recently that much of the credit for the quality of Mr. Stradivari's violins is due to the properties of the materials he had available to him. In particular, the logs that were to be made into the wood for the violins were floated in the harbor for delivery, altering their composition and causing them to be impregnated with various substances, and the varnishes used at the time often contained gem dust, which got into the grain of the wood and increased stiffness, thus altering the modes of vibration. Whether or not these particular features turn out in the long run to be relevant, the point is that many details of this type may not have been under the control of or within the knowledge of Mr. Stradivari, so that even if he had wished to reveal his violin-making formula to the world, in order to work it would have to specify particular products of particular dealers, and if any of these went out of business or changed fabrication techniques, it might not have been possible to find suitable substitutes. All of this is in addition to any peculiarities of fabrication Stradivari may have consciously or unconsciously employed. I think Bruce has found a very good analogy to the problem of reverse engineering launcher systems. That too is a materials problem, with emphasis both on the specific materials selected, and the exact nature of their treatment during fabrication, with loss of information at each interface between "contractor" and "subcontractor". As far as the SSME's are concerned, I think they show that with extraordinary care, design with very tight tolerances and margins is possible but not necessarily economical. I suspect, however, that much of their design will be applicable to future systems, particularly as the qualities of available materials continue to improve. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: 22 Nov 90 04:36:44 GMT From: trident.arc.nasa.gov!yee@ames.arc.nasa.gov (Peter E. Yee) Subject: NASA to use world's fastest supercomputer (Forwarded) Sarah Keegan November 14, 1990 Headquarters, Washington, D.C. (Phone: 202/453-2754) RELEASE: 90-151 NASA TO USE WORLD'S FASTEST SUPERCOMPUTER NASA researchers will have access to the world's fastest supercomputer as a member of the Concurrent Supercomputing Consortium, a newly-formed group of the nation's premier research organizations. Consortium members will be able to access Intel Corporation's Touchstone DELTA supercomputer system, slated for installation at the California Institute of Technology (Caltech), Pasadena, Calif., next spring. The DELTA system has a peak speed of 32 billion floating point operations per second, making it the world's fastest computer. The consortium will tackle some of today's most demanding computational and scientific challenges, such as global climate modeling, space science data analysis and pattern recognition of DNA sequences in the human genetic makeup. NASA will use the DELTA system as part of the agency's High- Performance Computing Initiative (HPCI), an ambitious program to accelerate the computing research capabilities required to maintain U.S. aeronautical and space science leadership in the 21st century. For example, DELTA will dramatically improve NASA's capability to simulate the performance of integrated aerospace vehicle systems throughout their flight regimes and mission profiles and will greatly enhance multidisciplinary research in global climate change and astrophysics. NASA will begin to use the DELTA system for research soon after it becomes available at Caltech. In addition, NASA researchers working on HPCI also will evaluate how much of an increase in computational performance DELTA offers over the agency's present systems. Lee B. Holcomb, Director of the Information Sciences and Human Factors Division in NASA's Office of Aeronautics, Exploration and Technology (OAET), is the agency's representative on the Concurrent Supercomputing Consortium's Policy Board. The board is headed by Caltech astronomer Thomas A. Prince. Paul Messina, also of Caltech, is Executive Director of the Consortium. Other members of the consortium are Argonne National Laboratory, Argonne, Ill.; California Institute of Technology; NASA's Jet Propulsion Laboratory, Pasadena, Calif.; Center for Research in Parallel Computation (lead center, Rice University, Houston); Defense Advanced Research Projects Agency, Arlington, Va.; Intel Corporation's Supercomputer Systems Division, Beaverton, Ore.; National Science Foundation, Washington, D.C.; Pacific Northwest Laboratory, Richland, Wash.; Lawrence Livermore National Laboratory, Berkeley, Calif.; Los Alamos National Laboratory, Los Alamos, N. Mex.; Oak Ridge National Laboratory, Oak Ridge, Tenn.; Purdue University, West Lafayette, Ind. and Sandia National Laboratories, Albuquerque, N. Mex. ------------------------------ Date: Fri, 23 Nov 90 17:19:13 EST From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. Subject: Light bulbs, thorium, space applications >From: solo!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!julius.cs.uiuc.edu!ux1.cso.uiuc.edu!aries!mcdonald@tut.cis.ohio-state.edu (Doug McDonald) >Subject: Re: The great light bulb debate >In article <9011212328.AA13640@cmr.ncsl.nist.gov> roberts@CMR.NCSL.NIST.GOV (John Roberts) writes: >>The mantles for gas lanterns are made with radioactive thorium oxide >>(presumably because of its mechanical properties at high temperatures). >>A reference book I have also states that it is included in trace quantities >>in the tungsten filaments of light bulbs (!). >Very very doubtful in light bulbs. It IS used in the filaments of >certain vacuum tubes: the thorium migrates to the surface and coats the >tungsten, producing a material with a lower work function, and hence >it emits electrons at lower temperatures. The treatment of the material >to get this to work is somewhat of a black art - I spent quite >a bit of my graduate career playing with various potions and >incantations over this stuff. Once you get it right, though, it works very >well. >Doug McDonald Since it looks as though thorium is potentially useful for space applications, I thought it would be worthwhile to post a few lines from the CRC Handbook of Chemistry and Physics (1990-91 edition, pp 4-33 to 4-44): "Thorium is now thought to be about three times as abundant as uranium and about as abundant as lead or molybdenum. The metal is a source of nuclear power. There is probably more energy available for use from thorium in the minerals of the earth's crust than from both uranium and fossil fuels [combined]. ...Thorium oxide has a melting point of 3300C, which is the highest of all oxides. Only a few elements, such as tungsten, and a few compounds, such as tantalum carbide, have higher melting points. ...The principal use of thorium has been in the preparation of the Welsbach mantle, used for portable gas lights. These mantles, consisting of thorium oxide with about 1% cerium oxide and other ingredients, glow with a dazzling light when heated in a gas flame. Thorium is an important alloying element in magnesium, imparting high strength and creep resistance at elevated temperatures. Because thorium has a low work-function and high electron emission, it is used to coat tungsten wire used in electronic equipment. The oxide is also used to control the grain size of tungsten used for electric ------------------------------------------------------------------------------ lamps; it is also used for high-temperature laboratory crucibles. ----- [Also used to make glass with high index of refraction for lenses, etc.] ...(232)Th occurs naturally and has a half-life of 1.4E10 years. It is an alpha emitter. (232)Th goes through six alpha and four beta decay steps before becoming the stable isotope (208)Pb. (232)Th is sufficiently radioactive to expose a photographic plate in a few hours. Thorium disintegrates with the production of thoron (radon(220)), which is an alpha emitter and presents a radiation hazard. Good ventilation of areas where thorium is stored or handled is therefore essential." Moral: on long camping trips, don't store your spare mantles along with your camera film. :-) Incidentally, upon further research, incandescent bulbs were filled with nitrogen rather than vacuum starting in 1913, and later various mixes of nitrogen and argon were employed. (Encyclopaedia Britannica, 1990) John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: 22 Nov 90 14:51:00 GMT From: rex!samsung!usc!sdd.hp.com!zaphod.mps.ohio-state.edu!rpi!uupsi!sunic!news.funet.fi!hydra!hylka!pvtmakela@ames.arc.nasa.gov Subject: Re: NASA Prediction Bulletin Distribution It would be very nice, if the NASA Prediction Bulletins will be available from some anonymous-ftp site. I have just asked in newsgroup sci.astro, if the predictions already are in some file archive, but I haven't got any positive answer yet. Veikko Makela -------------------------------------- pvtmakela@CC.Helsinki.FI Veikko.Makela@f861.n515.z2.FidoNet.ORG -------------------------------------- ------------------------------ Date: 23 Nov 90 17:19:25 GMT From: usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo!henry@apple.com (Henry Spencer) Subject: Re: Commercial Shuttle Proposals In article <1652.274BF768@ofa123.fidonet.org> Wales.Larrison@ofa123.fidonet.org (Wales Larrison) writes: >HS>Well, the obvious reason [why this can't be done] is "because >HS>NASA will never give it up"... > Which is the same thing that was said about the Delta and Atlas >programs. (And was said about Intelsat). It just takes a top-level >(Presidential level) policy decision, and support in Congress... I think NASA would fight much harder over the shuttle than they did over the expendables. Commercializing the expendables was done after NASA had largely lost interest in them. (And NASA still thinks that a NASA payload on an Atlas is a government launch, not a commercial one.) The shuttle is NASA's current flagship; they'll seriously fight to keep it. Given the reputation they've acquired in recent years, they may not succeed... but it's going to require real determination from the White House and Congress to make it happen. If the management doesn't seem determined to split it off completely, NASA will propose a "compromise" in which more of the detail work is farmed out to contractors but NASA stays in control. -- "I'm not sure it's possible | Henry Spencer at U of Toronto Zoology to explain how X works." | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 22 Nov 90 15:00:42 GMT From: agate!shelby!msi.umn.edu!cs.umn.edu!uc!nachos.SSESCO.com!elmquist@ucbvax.Berkeley.EDU (Chris Elmquist) Subject: Re: NASA Prediction Bulletin Distribution In article <4062.274be5d4@cc.helsinki.fi> pvtmakela@cc.helsinki.fi writes: > > > It would be very nice, if the NASA Prediction Bulletins > will be available from some anonymous-ftp site. I have > just asked in newsgroup sci.astro, if the predictions > already are in some file archive, but I haven't got any > positive answer yet. > I am working on this issue with Dr. Kelso and we've just about got it in place. Stand by for further details... -- Chris Elmquist, N0JCF Internet: elmquist@SSESCO.com AMPRN: N0JCF@WB0GDB.MN.USA.NA BellNet: (612) 785-3516 -- Chris Elmquist, N0JCF Internet: elmquist@SSESCO.com AMPRN: N0JCF@WB0GDB.MN.USA.NA BellNet: (612) 785-3516 ------------------------------ Date: 24 Nov 90 04:45:57 GMT From: mcgill-vision!thunder.mcrcim.mcgill.edu!clyde.concordia.ca!news-server.csri.toronto.edu!utgpu!utzoo!henry@bloom-beacon.mit.edu (Henry Spencer) Subject: Re: Photon engine In article <4948@bwdls58.UUCP> hwt@bwdlh490.BNR.CA (Henry Troup) writes: >|>only thing left behind with an expanding cloud of plasma. A 100 tonne >|>ship accelerating at 1 g requires a 3x10**11 watt powerplant. How >|>does that compare to the human species total power output these days? > >Well, it must be less than the power output of a shuttle at launch, right? Shuttle power output at launch is 15-20 gigawatts, I believe. However, the inequality you propose doesn't work. There is no unique answer to the question of power output for a given mass at a given acceleration. It depends on the exhaust velocity. A 100T ship at 1G (call it 10 m/s^2) requires a thrust of 1MN. Thrust is mass flow times exhaust velocity, by conservation of momentum. At an exhaust velocity of 3e8 m/s, naively (ignoring relativistic issues), we need 3.3e-3 kg/s of mass flow. Kinetic energy over time of that flow, with respect to the rocket, naively, is 0.5*mass_flow*ve^2, or about 15e13 W. Call it 150 terawatts. I'd have to hit the books to sort out the non-naive version of this, but it probably won't differ by more than a small integer, and it might even be the same. I don't have numbers handy for the whole species or total power, but the electrical power generating capacity of the US is circa 1 terawatt, I think. Handling 150TW would be, um, a challenge. For example, assume an efficiency of 50%. (That's awfully good for lasers, which are inherently pretty lossy devices.) That means our total power output actually has to be 300TW, and the missing 150TW comes out as heat. We have to get rid of that heat... somehow. The only long-term answer is radiators, but they're big and heavy. Ignoring practicalities, let us use evaporative cooling instead. We'll be generous and say our lasers can run at 2500K (2227C; if you want it in Fahrenheit, Rankine, or Reaumur, convert it yourself :-)). Assume our evaporative material is water, which has a high heat capacity, call its heat capacity a straight 4.2kJ/kgK, ignoring heats of melting and boiling, and assume we start with ice at roughly absolute zero. Then we are using a mere 15 kilotons of water per second to cool our 100T spacecraft. That won't work. :-) Another non-trivial consideration for photon rockets is how you power them. They are fiercely difficult to build. If you are burning up far more mass powering them than you are exhausting through them, better you should build a system with the same net mass flow and a lower exhaust velocity, by using all the mass as exhaust. Using fission or fusion to power a photon rocket is ridiculous, in particular. Fusion burns hydrogen to helium (ignoring lots of fine points), releasing quite a small fraction of the total mass as energy. Even with no losses, most of your fuel mass is going to run your fusion reactor, after which you are dumping the helium overboard at roughly zero velocity (compared to the exhaust velocity, any velocity you can get for that helium is zero). Building a fusion rocket would give similar performance with many fewer problems. Photon rockets make sense only if you can power them with total matter annihilation; even matter- antimatter reactions are better used as rockets than as a power source. (All the more so because we are not very far from being able to build antimatter rockets, while handling terawatts for a photon rocket is well beyond us.) -- "I'm not sure it's possible | Henry Spencer at U of Toronto Zoology to explain how X works." | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 22 Nov 90 15:00:42 GMT From: agate!shelby!msi.umn.edu!cs.umn.edu!uc!nachos.SSESCO.com!elmquist@ucbvax.Berkeley.EDU (Chris Elmquist) Subject: Re: NASA Prediction Bulletin Distribution In article <4062.274be5d4@cc.helsinki.fi> pvtmakela@cc.helsinki.fi writes: > > > It would be very nice, if the NASA Prediction Bulletins > will be available from some anonymous-ftp site. I have > just asked in newsgroup sci.astro, if the predictions > already are in some file archive, but I haven't got any > positive answer yet. > I am working on this issue with Dr. Kelso and we've just about got it in place. Stand by for further details... -- Chris Elmquist, N0JCF Internet: elmquist@SSESCO.com AMPRN: N0JCF@WB0GDB.MN.USA.NA BellNet: (612) 785-3516 -- Chris Elmquist, N0JCF Internet: elmquist@SSESCO.com AMPRN: N0JCF@WB0GDB.MN.USA.NA BellNet: (612) 785-3516 ------------------------------ End of SPACE Digest V12 #593 *******************