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 ; Thu, 22 Mar 90 02:18:44 -0500 (EST) Message-ID: <8a27kuC00VcJ4N304w@andrew.cmu.edu> Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Thu, 22 Mar 90 02:18:18 -0500 (EST) Subject: SPACE Digest V11 #174 SPACE Digest Volume 11 : Issue 174 Today's Topics: Re: Sandia Railgun Re: Coilgun on a 747 - supplies to orbit at $20/lb? Getting Drafted Space List Re: SR-71 and dates Re: More space station news... Austrailian Reduced Wobble telescope Re: SR-71 ( as a collectable ) Re: Strange flash of light Re: Coilgun on a 747 - supplies to orbit at $20/lb? ---------------------------------------------------------------------- Date: 17 Mar 90 23:34:25 GMT From: haven!uflorida!uakari.primate.wisc.edu!samsung!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo!henry@louie.udel.edu (Henry Spencer) Subject: Re: Sandia Railgun In article <45600004@uxa.cso.uiuc.edu> sfn20715@uxa.cso.uiuc.edu writes: >2) The article quotes 10,000G's of acceleration; mil-spec electronics >can withstand 10G's at most. (Allows bulk material only.) Not so. The military fires electronics from guns every day (e.g. the Copperhead laser-homing antitank shell) and has been doing so since World War II (proximity fuzes). The design has to pay attention to the problem, but drastic measures are not needed. The Copperhead electronics simply use fairly small boards that are very well built and well supported. Proximity- fuzed antiaircraft shells contained *vacuum tubes* until the late 50s. Admittedly, there is the question of whether you want to build all your space hardware to withstand gun launches. Probably you don't. But it can be done for most things. If gun launch is sufficiently cheaper than using rockets, it may be worthwhile. -- MSDOS, abbrev: Maybe SomeDay | Henry Spencer at U of Toronto Zoology an Operating System. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 18 Mar 90 04:49:22 GMT From: sam.cs.cmu.edu!vac@pt.cs.cmu.edu (Vincent Cate) Subject: Re: Coilgun on a 747 - supplies to orbit at $20/lb? Kevin Strietzel: >At 100% efficiency, 20,000 kw is about 27,000 horsepower. The biggest diesel >engines I know of only do 4200hp (about 3,100 kw). How about a gas turbine? >Maybe then it could burn jet fuel instead of having lots of extra tankage for >diesel oil; 747-100B could do something like 9 hours in the air with reserves. A gas turbine (or two) probably is the way to go. I recall these being one of the types of engines that are around 1 hp/lb. Running off the tanks in the wings would be great! Some of these big planes can carry a lot of fuel. I know they started flying some large plane from San Fransisco California to Sidney Australia this summer - 16 hours non-stop. A quick estimate puts the fuel consumption of a 20,000 kw generator at a little under that of the engines on a 747. Thus using the same tanks would about cut flying time in half. I like it!!!! > payload(kg/lb) comments > -------------- -------- >747-200F 113400/250000 cargo Looks like we might be able to use 200,000 lbs just for the electromagnetic gun. If we have not already made a gun this light that shoots 25 kg projectiles at orbital velocity, I'll bet we could. Actually, we can probably do 50 kg projectiles with such a heavy gun. This looks more and more like a good way to get supplies into space!!!!! Thanks for the info, -- Vince PS What is the hard part for this type of approach? Getting a gun that weighs less than 200,000 lbs? ------------------------------ Date: 21 Mar 90 17:06:40 GMT From: mcsun!ukc!edcastle!erci18@uunet.uu.net (A J Cunningham) Subject: Getting Drafted In-Reply-To: Mary Shafer (OFV's message of 20 Mar 90 18:45:30 GMT > The Air Force, Navy, and Marines did NOT draft people. Army troops > (who may have been drafted) rode in helicopters flown by pilots who > had volunteered. (Yes, this latter is hair-splitting.) Even in World > War II, all air crew were volunteers. > > The same is true, I understand, of the Royal Air Force, the Royal > Navy, and the Royal Marines--National Service was in the British Army. Well plenty of Army personnel were herded into gliders for Airborne assaults (e.g. Operation Overlord, Operation Market Garden). I doubt if that meny of them were volunteers. I accept your point that American Air crew in WWII were all volunteers although I don't know if the same was true for British pilots and air-crew and it probably wasn't the case for Russians. (You did say no-one in your original article) Tony -- Tony Cunningham, Edinburgh University Computing Service. erci18@castle.ed.ac.uk Yuppies think I'm a wino 'cos I seem to have no class, Girls think I'm perverted 'cos I watch them as they pass. ------------------------------ Date: Wed, 21 Mar 90 14:35:33 PST From: greer%utd201.dnet%utadnx@utspan.span.nasa.gov X-Vmsmail-To: UTADNX::UTSPAN::AMES::"space+@andrew.cmu.edu" Subject: Space List Much time, mental energy and net bandwidth is wasted because many of the people on this net don't have the knowledge or expertise to to make a simple reality check on some of the ideas presented here, or on ideas that they may come up with independently. There isn't really that much you need to know to be able to do this sort of check, and it seems to me that many of the creative minds out there could be much more fruitful if such knowledge were easily available. So I propose the compilation of a list, something like that of E. D. Hirsch's in his book _Cultural Literacy_, but much shorter and having numbers and equations relevant to space science and exploration. Once having been compiled, this list could be posted occasionally like the _Frequently Asked Questions_ list. I haven't the time to compile this list by myself, but if people will email their suggestions to me, or if they can't reach me, to the Space_Digest, I'll put them together and post the result. Here's a meager start. Numbers in parentheses are approximations that will serve for most blue-skying purposes. Numbers 7726 m/s (8000) -- Earth orbital velocity at 300 km altitude 3075 m/s (3000) -- Earth orbital velocity at 35786 km (geosync) 6378 km (6400) -- Mean radius of Earth 1738 km (1700) -- Mean radius of Moon 5.974e24 kg (6e24) -- Mass of Earth 7.348e22 kg (7e22) -- Mass of Moon 1.989e30 kg (2e30) -- Mass of Sun 3.986e14 m^3/s^2 (4e14) -- Gravitational constant times mass of Earth 4.903e12 m^3/s^2 (5e12) -- Gravitational constant times mass of Moon 1.327e20 m^3/s^2 (13e19) -- Gravitational constant times mass of Sun 384401 km ( 4e5) -- Mean Earth-Moon distance 1.496e11 m (15e10) -- Mean Earth-Sun distance (Astronomical Unit) Equations Where d is distance, v is velocity, a is acceleration, t is time. For constant acceleration d = d0 + vt + .5at^2 v = v0 + at v^2 = 2ad For circular Keplerian orbits, where u is gravitational constant, a is semimajor axis of orbit, P is period. v^2 = u/a P = 2pi/(Sqrt(u/a^3)) Miscellaneous f=ma -- Force is mass times acceleration w=fd -- Work (energy) is force times distance Atmospheric density varies as exp(-mgz/kT) where z is altitude, m is molecular weight in kg of air, g is acceleration of gravity, T is temperature, k is Bolztmann's constant. Up to 100 km, d = d0*exp(-z*1.42e-4) where d is density, d0 is density at 0km, is approximately true, so d@12km (40000 ft) = d0*.18 d@9 km (30000 ft) = d0*.27 d@6 km (20000 ft) = d0*.43 d@3 km (10000 ft) = d0*.65 Ok, so it's a short list, but I have to get back to work. What I'd like to see is stuff like basic rocketry numbers and equations, maybe some aerodynamical stuff, and just whatever you think might be helpful in making rudimentary space related engineering calculations, or stuff you think is essential for a rudimentary understanding of space exploration problems. It would also be nice to have some comparative items like how much energy it takes to get the shuttle into orbit, how much it would take to get something small like the shuttle up to X% of the speed of light, how much energy a typical American city with a million people uses, etc. ------------- Dale M. Greer, whose opinions are not to be confused with those of the Center for Space Sciences, U.T. at Dallas, UTSPAN::UTADNX::UTDSSA::GREER While the Bill of Rights burns, Congress fiddles. -- anonymous ------------------------------ Date: 9 Mar 90 16:21:59 GMT From: m2c!wpi!tmurphy@husc6.harvard.edu (Tom [Chris] Murphy) Subject: Re: SR-71 and dates In article <10554.5100.forumexp@mts.rpi.edu> Greg_d._Moore@mts.rpi.edu (Commander Krugannal) writes: > > > Someone mentioned attaching the Pegasus vehicle to the SR-71. > Someone (from Orbital Service I believe) replied that there > was no place to do it. Actually that is wrong. Soon after the > SR-71 was built, a drone was built based on the J-58. This was > called the D-21. It used the same engine (the J-58) and same I believe this project was halted for safty reasons after an accident that killed the rear-seat officer in an SR-71. So it might not be a great idea. Thomas C. Murphy | Internet: tmurphy@wpi.wpi.edu Worcester Polytechnic Institute CAD Lab | tmurphy@zaphod.wpi.edu 100 Institute Road | BITNET: TMURPHY@WPI.BITNET Worcester, MA 01609 | CompuServe: 73766,130 Phone (508) 831-5323 | Fax (508) 831-5680 | If the Universe is constantly expanding, why can't I ever find a parking space? ------------------------------ Date: 21 Mar 90 15:49:18 GMT From: news-server.csri.toronto.edu!utgpu!watserv1!watcgl!watnow!mark@rutgers.edu (Mark Earnshaw) Subject: Re: More space station news... In article <22519.2605f0aa@kuhub.cc.ukans.edu> honors@kuhub.cc.ukans.edu writes: >Thought my fellow netters would be interested in this report on the >Incredible Shrinking Violet Space Station, ExpensiveDom... These >stories came off the AP wire today (3/19/90): > >Report: NASA Investigators Conclude Space Station Plans Flawed [Description of how Freedom will "fall apart" before it is finished] I give up. Why don't we contract Freedom out to the Soviets? At least we know their design works. :-( -------------------------------------------------------------------------------- Mark Earnshaw, Systems Design Engineering {uunet,utai}!watmath!watnow!mark University of Waterloo, Ontario, Canada mark@watnow.waterloo.{edu,cdn} ------------------------------ Date: Wed, 21 Mar 90 13:25 EST From: Subject: Austrailian Reduced Wobble telescope Awhile back on the Discovery Channel, I saw a piece on these guys down under at one of the universities that had crafted an optical telescope that had the capability to adjust for the wobble of stars due to the air. It essentially consisted of two small telescopes a few meters apart that had their mirrors hooked up to some sort of computer controled, peizoelectric driven movement devices. Supposedly, the computer tracked the star's image and minutely adjusted the postion of the mirrors to keep up with it with a minimal delay time. They claimed that a future version to be built would have better resolving power than Palomar. Any Aussies on the net care to comment/correct on this? It sounds interesting to me. Korac MacArthur "Death before disclaimer!" ------------------------------ Date: 21 Mar 90 20:28:44 GMT From: zaphod.mps.ohio-state.edu!brutus.cs.uiuc.edu!ux1.cso.uiuc.edu!deimos.cis.ksu.edu!iowasp!parmentier@tut.cis.ohio-state.edu Subject: Re: SR-71 ( as a collectable ) >Now that the SR-71 is being decommissioned I'd like to know: are the >junked planes going to be for sale? Hell of an acquisition for a >vintage plane collector. I would say no mainly becuase the SR-71 is made mostly of titanium alloys and would be recycled before they were sold. ------------------------------ Date: 21 Mar 90 16:46:55 GMT From: cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu (Henry Spencer) Subject: Re: Strange flash of light In article <1769@lakesys.lakesys.com> jtk@lakesys.UUCP (Joseph T. Klein) writes: >This is an odd event. Why do the space/astro people shy away from talking >about these events? ... Probably because the space/astro people are waiting for detailed technical reports so they can argue from known facts, a constraint that has never bothered the UFO people... -- Never recompute what you | Henry Spencer at U of Toronto Zoology can precompute. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 21 Mar 90 16:55:59 GMT From: cs.utexas.edu!samsung!uakari.primate.wisc.edu!nic.MR.NET!timbuk!lfa@tut.cis.ohio-state.edu (Lou Adornato) Subject: Re: Coilgun on a 747 - supplies to orbit at $20/lb? Caveat: I don't think anyone has answered the question of whether a coil gun can be fit into the ~70m body of a 747, leaving enough room for a power supply ,recoil travel, shock absorbers, and a useful fuel load. The following assumes that the answer is at least "maybe". Instead of firing the projectile forward, why not fire it out the tail (aside from the scatalogical inferences that critics will undoubtedly use)? The stall speed of the 747 is such a small fraction of orbital velocity that it shouldn't make a difference, either way. You're still high enough to expend less of your muzzle velocity shouldering aside air molecules, you still get the improved launch angle, and now that the recoil is taken by the 747 in the direction direction of thrust, you don't need as much CG travel (since you can stop the gun faster). Other benefits: there won't be a 400kt wind blowing into the muzzle, and the 747 won't have to fly through a hypersonic shock wave. BTW, I think that the CG problem might have been overstated. As I understand it (from seemingly endless ground school lectures), the reason that eceeding the CG envelope is a Bad Thing is that it can cause the craft to become stable in a stall (or spin?). However, nothing says that the gun can't be moved after it recoils. If we're starting at 40,0000+ ft, even if we immediately start to fall like a rock, in the 30 seconds that it takes to winch the gun back into position, we've fallen less than 15,000 ft. Once the CG is returned to its envelope the stall condition is unstable, the plane falls back into controlled flight, the pilot wrests his/her fate from the jaws of death, and everyone gets to go home. Lou Adornato | Statements herein do not represent the opinions or Cray Research | attitudes of Cray Research, Inc. or its subsidiaries. lfa@cray.com | (...yet) ------------------------------ End of SPACE Digest V11 #174 *******************