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 Mar 90 02:39:31 -0500 (EST) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Fri, 30 Mar 90 02:38:53 -0500 (EST) Subject: SPACE Digest V11 #201 SPACE Digest Volume 11 : Issue 201 Today's Topics: Re: Coilgun on a 747 - supplies to orbit at $20/lb? Re: Discovery's Spin in 2010 (Was Re: Artificial gravity) Phobos, Deimos Comparative Costs to LEO Payload Status for 03/29/90 (Forwarded) Re: Will we lose another orbiter? Re: Discovery's Spin in 2010 (Was Re: Artificial gravity) Re: B-52/Pegasus launch scheduled for April 4 (Forwarded) ---------------------------------------------------------------------- Date: Thu, 29 Mar 90 10:10:36 PST From: greer%utd201.dnet%utadnx@utspan.span.nasa.gov X-Vmsmail-To: UTADNX::UTSPAN::AMES::"space+@andrew.cmu.edu" Subject: Re: Coilgun on a 747 - supplies to orbit at $20/lb? In SPACE digest V11 #194 mcsun!ukc!stc!root44!hrc63!mrcu!paj@uunet.uu.net (Paul Johnson) writes: >Here are some rough calculations. Say we need 3 miles per second to >get into orbit (I expect someone somewhere knows better, but stick >with that for now). Say 15600 feet per second. > >(some equations deleted) > >Say about 16000g. > >You guys don't want a coil gun, you want a conventional chemical gun. > >Paul. This is a prime example of what happens when you don't use SI units and you don't know a few basic space facts. Velocity for a 300 km orbit is about 7.7 km/s. If you must use those other units, their are 1.61 km in a mile so 7.7 km = 4.8 mi. A 747 is 75 m long, so the relation v^2=2ad gives us about 40000 g for the acceleration to orbital velocity, consuming about 3 MJ of energy per kg of projectile. But in the Scientific American article on the proposed Hawaiian gun, their stated intent is to acheive a 6 km/s muzzle velocity just to get the projectile above significant atmosphere and then use a rocket motor to boost to orbital velocity. The payload would be 100 kg and the motor + fuel would be 300 kg. Since their gun is 800 m long, the minimum acceleration would be about 2300 g, requiring about 1.8 MJ/kg. They didn't say how much speed the projectile would lose on its way through the atmosphere. Suppose you only need 4 km/s if you launch from a 747 at. In that case, the acceleration need only ;-) be about 11000 g, using about 0.8 MJ/kg. How much is a megajoule, anyway, in "real life" terms? ---- 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: 29 Mar 90 06:01:37 GMT From: unmvax!nmtsun!nraoaoc@ucbvax.Berkeley.EDU (NRAO Array Operations Center) Subject: Re: Discovery's Spin in 2010 (Was Re: Artificial gravity) In article <1990Mar28.191014.16290@helios.physics.utoronto.ca> neufeld@physics.utoronto.ca (Christopher Neufeld) writes: > Yes and no. You can't do what you said, but you don't have to do that >to achieve the effect seen in the movie. > Let's assume that the angular momentum vector of the Discovery is >aligned along the long axis of the ship during its normal operation. Say >that the Discovery is pointed directly at, say, the moon. Now, let the >bearings on the carousel seize up. The ship will start to spin about its >long axis. There is a lower energy mode of this angular momentum value, >though, which is a spinning around the pitch or yaw axes. The fact that >the ship is not a perfectly rigid body, along with possible >gravitational influences from nearby Jupiter and its moons, will cause >the ship to settle into this lower energy mode, even without an external >net torque. The difference is that the ship itself will have rotated >through ninety degrees in shifting from the one mode to the other. Now, >the ship is not pointing at the moon, but is rotating around an axis >which points at the moon. > The angular momentum of this final system is the same, while the >energy is lower. You're quite right about this effect. Didn't we see a good example of this with one or two of the early Explorer series satellites? (Energy was dissipated by flexing of the four whip antennas. It was initially rotating about its long axis, but eventually started tumbling end over end.) I must admit, I've never been completely clear on what happens to one of these systems when the object is rotating about axis with maximal moment of inertia. There's nothing to prevent it from radiating still more energy, (or is there?) How do we conserve momentum? There was a nice demo of this effect by one of the astronauts on Skylab, too. He used a half-filled Tang (?) container. The bottle was cylindrical, and energy was dissipated in the sloshing liquid. It took about 30 seconds to go from rotation about the minimal principal axis to rotation about a (degenerate) maximal axis. About 2010, though. If my none-too-perfect memory serves, wasn't the carousel spinning about the yaw axis? (I.e. about a vertical axis, given the usual cinematic conventions.) To first order, the Discovery probably has equal moments about the pitch and yaw axes. When the bearings seize, the entire ship should rotate about the yaw axis to conserve angular momentum. (Surely that _must_ be the solution for an idealized cylinder, no?) Wasn't it shown rotating about the pitch axis? The explanation that you posit wasn't what they had in mind, even allowing a higher MoI in pitch than in yaw, because when they restarted the carousel, the ship stopped spinning. Had energy dissipation been part of the mechanism, it wouldn't have returned to the original state. I think that some cinematic liberties were indeed taken with the laws of physics. On a related note, the producers weren't above making the earth spin backwards for the same reasons. The sunrise over the VLA that you see in the beginning of the movie is actually a sunset filmed in reverse. (Or do I have that backwards? Haven't seen the movie in a long time.) ----- This is a shared guest account, please send replies to dbriggs@nrao.edu (Internet) Dan Briggs / NRAO / P.O. Box O / Socorro, NM / 87801 (U.S. Snail) ------------------------------ Date: Thu, 29 Mar 90 21:00:36 EST From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. Subject: Phobos, Deimos >Date: 28 Mar 90 15:08:46 GMT >From: aramis.rutgers.edu!athos.rutgers.edu!masticol@rutgers.edu (Steve Masticola) >Subject: Re: Martian Stardard Time >Just out of curiosity, how large and bright would Deimos and Phobos >appear from the Martian surface? Would they have features observable >to the naked eye? Cast shadows? >- Steve (masticol@cs.rutgers.edu) The angular size of Phobos as seen from the surface should be about .153 degrees - ~1/3.3 of the size of our full moon, so you should be able to see some detail. Deimos would be ~.023 degrees across, or ~1/44 of the size of the moon. You should be able to see that it isn't a star. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: 29 Mar 90 20:52:02 GMT From: zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!zardoz.cpd.com!dhw68k!ofa123!Wales.Larrison@tut.cis.ohio-state.edu (Wales Larrison) Subject: Comparative Costs to LEO To all interested, here is a set of comparative cost/lb into Earth Orbit. Please, let's argue from a realistic set of data - I've listed sources and assumptions to show you this is the real world. EDITORIAL COMMENT: I'm tired of seeing people buy the propaganda that the Space Shuttle "is by far the most expensive means of space transportation". It isn't. SUMMARY: Delta II: $3603 - 3874 per pound into LEO Atlas Centaur: $3740 - 4471 per pound into LEO Titan III: $3333 per pound into LEO Titan IV: $3125 - 4250 per pound into LEO Shuttle: $3036 - 2764 per pound into LEO COST ASSUMPTIONS: All cargo cost estimates are based upon a single user with a payload delivered to 150 nautical miles and an orbital inclination of 28.5 degrees (due East from KSC). This user is assumed to be a commercial customer, looking for a single, simple, standardized launch. No block buys of vehicles were assumed, nor any new developments. No upper stage costs are included. Payload integration and the minimum necessary launch services costs have been included in each cost estimate. Wherever possible, costs have been based upon actual quotes from commercial offerings. Costs for the Shuttle were not based upon NASA numbers, and are based upon actual shuttle costs, not the price charged to commercial users (which may be lower). While every attempt has been made to keep the assumptions and comparison constant across the different launch vehicle, any of the cost numbers can be varied +/- 10% due to slight differences in accounting (ie, year of dollars, minor additional services, etc.) DELTA II: The Delta II costs are based upon various published sources for the price of a commercial Delta 7925 (Delta II) launch. Sources used include: McDonnell/Douglas company literature, Aviation Week, Defense Daily, DoD Budget requests, and Flight International). The single vehicle contract cost of between $40 and 43 million is a commercial contract cost which includes system and launch integration services, without an upper stage cost. Although the launch is for a single payload, it was assumed the launch vehicle order would follow the current Delta pricing policy that piggybacks additional production units onto the Air Force Delta II orders which allow for a continuous production line. The Delta II performance into LEO is 11.1 klb. Based upon the vehicle contract price range, the cargo cost to LEO is between $3603 and 3874 per pound. ATLAS-CENTAUR: Based upon published Atlas G + Centaur Data, the single vehicle commercial contract cost, including launch and integration sercies, but no upper stage, ranges from $46 to 55 million per launch. Sources of data used here include: General Dynamics company literature, Aviation Week, Aerospace Daily, Space International, and Space Business News. As with the Delta II, the launch vehicle is assumed to be a single, additional order that is part of an existing production run. (Current contract data indicates that if the vehicle were a part of a government block buy, the cost could be reduced to $450 million for an 11 vehicle production run with no contractual oversight and no performance penalties.) Using the LEO performance of 12.3 Klb, the price range yields a cost to LEO of $3740 to 4471 per pound into LEO. (continued ) -- Wales Larrison ...!{dhw68k,zardoz,lawnet,conexch}!ofa123!Wales.Larrison Wales.Larrison@ofa123.FIDONET.ORG 714 544-0934 2400/1200/300 ------------------------------ Date: 29 Mar 90 17:48:41 GMT From: trident.arc.nasa.gov!yee@ames.arc.nasa.gov (Peter E. Yee) Subject: Payload Status for 03/29/90 (Forwarded) Daily Status/KSC Payload Management and Operations 03-29-90. - STS-31R HST (at Pad-B) - Preps for HST transfer into the payload bay were completed yesterday. The actual transfer will occur today. - STS-35 ASTRO-1 (at OPF) - End to end testing was completed second shift yesterday. RAAB removal and replacement was completed on third shift today. RAAB retest is active and will continue through first shift today followed by igloo cover installation on second shift. STS-40 SLS-1 (at O&C) - Preps for rack and floor installation into the module were worked yesterday and will continue today. - STS-42 IML-1 (at O&C) - Racks 3, 4 and 7 staging operations were worked yesterday. Racks 3, 4 and 11 staging activities along with module clamp inspections are scheduled for today. - STS-45 (Atlas-1)- Pallet joint kit installation on frame 4 will be worked today. ------------------------------ Date: 29 Mar 90 16:10:00 GMT From: network.ucsd.edu!hp-sdd!apollo!rehrauer@ucsd.edu (Steve Rehrauer) Subject: Re: Will we lose another orbiter? [ I read sci.space infrequently, so forgive me if this is old hat. ] We've lost one shuttle, and I'm sure it's likely that we'll eventually lose another. My question is, after N years of operating these beasts, have we (meaning NASA, I guess) learned how to build a better shuttle? Has Challenger's replacement "evolved" in any way? More importantly, how much has the shuttle program taught us about building the true next generation of orbiter, be it NASP or whatever? (I.e.: a manned system that delivers some combination of lower payload-delivery cost, greater reliability, less-stringent maintenance, etc than do the shuttles.) -- >>"Aaiiyeeee! Death from above!"<< | Steve Rehrauer, rehrauer@apollo.hp.com "Flee, lest we be trod upon!" | The Apollo System Division of H.P. ------------------------------ Date: 30 Mar 90 00:49:11 GMT From: unmvax!nmtsun!nraoaoc@ucbvax.Berkeley.EDU (Daniel Briggs) Subject: Re: Discovery's Spin in 2010 (Was Re: Artificial gravity) In article <1990Mar29.181240.16138@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >In article <4028@nmtsun.nmt.edu> dbriggs@nrao.edu (Daniel Briggs) writes: ^^^^^^^^^^^^^^^^ Hey, you got the attribution right! Most people don't. >>You're quite right about this effect. Didn't we see a good example of >>this with one or two of the early Explorer series satellites? (Energy >>was dissipated by flexing of the four whip antennas. It was initially >>rotating about its long axis, but eventually started tumbling end over >>end.) ... > >That's right; it was Explorer 1, in fact, and the folks on the ground were >quite surprised by it. Actually, I thought that Explorer 1 was merely the one that was hit the worst by this problem. As I remember reading, later Explorers had rigid antennae. This helped a whole lot, but eventually a number of them tumbled for exactly the same reason. The antennae weren't *completely* rigid. No one was too concerned about the later ones, since I believe that this was after the operational lifetimes of the satellites in question. ----- This is a shared guest account, please send replies to dbriggs@nrao.edu (Internet) Dan Briggs / NRAO / P.O. Box O / Socorro, NM / 87801 (U.S. Snail) ------------------------------ Date: 29 Mar 90 20:12:03 GMT From: argosy!kevin@decwrl.dec.com (Kevin S. Van Horn) Subject: Re: B-52/Pegasus launch scheduled for April 4 (Forwarded) In article <46046@ames.arc.nasa.gov> yee@trident.arc.nasa.gov (Peter E. Yee) writes: > > The Pegasus program is sponsored by the Department of >Defense Advanced Research Projects Agency. Pegasus was developed >by Orbital Sciences Corp., Fairfax, Va., and Hercules Aerospace >Co., Wilmington, Del. Sponsored in what way? It was my understanding that OSC and Hercules paid for the entire development out of their own funds. Or do you consider purchasing launches to be a form of sponsorship? ------------------------------------------------------------------------------ Kevin S. Van Horn | The means determine the ends. kevin@argosy.maspar.com | ------------------------------ End of SPACE Digest V11 #201 *******************