Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from hogtown.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 ; Tue, 14 May 91 02:13:33 -0400 (EDT) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Tue, 14 May 91 02:13:28 -0400 (EDT) Subject: SPACE Digest V13 #545 SPACE Digest Volume 13 : Issue 545 Today's Topics: Re: Why the space station? Re: Energia (was Re: Saturn V blueprints) Re: Laser launchers Re: Saturn V and the ALS Re: Why the space station?y Re: Ethics of Terraforming (was Re: Terraforming Venus) Barbara Boxer Re: NASP 2001 and NASP Re: 2001 and NASP Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription requests, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: 11 May 91 22:30:32 GMT From: clark@gumby.wisc.edu (Clark Brooks) Subject: Re: Why the space station? gwh@tornado.Berkeley.EDU (George William Herbert) writes: >We're going to fly 17 shuttle missions to lift and assemble Freedom, and at >25 tons each this is about 425 tons-equivalent to orbit. If instead we >were to build it in a plug-cans-together manner (no truss, etc) we could >very likely get the same capability for a lot less weight to orbit. I.E. >5 to 10 Titan launches (100-200 tons). This is the approach that MIR was >built under. Oliver Harwood used to work for one of the aerospace companies around here. He combined this idea with a knowledge of Fuller's space frame and a love of modularity to produce a truss FROM cans-plugged-together. It's a marvel of design. It's only flaw is that it's so modular that Congress could cut its budget down to 2 (two) shuttle construction-flights without totally killing it. -- clark@csvax If we knew what we were doing, it wouldn't be science. ------------------------------ Date: 30 Apr 91 14:22:00 GMT From: unisoft!hoptoad!pacbell!pacbell.com!mips!zaphod.mps.ohio-state.edu!caen!ox.com!fmsrl7!wreck@ucbvax.Berkeley.EDU (Ron Carter) Subject: Re: Energia (was Re: Saturn V blueprints) In article <1991Apr23.202400.29843@en.ecn.purdue.edu> irvine@en.ecn.purdue.edu (/dev/null) writes: >In article <00947905.3FAEE140@KING.ENG.UMD.EDU>, sysmgr@KING.ENG.UMD.EDU (Doug Mohney) writes: >>They need the cash too badly...they'd provide decent services. There's nothing >>which NASA needs to lift into orbit on Energia which couldn't wait a couple of >>years in case of disruption of launch services from the Soviet Union .... >Yeah, but the couple of years disruption might turn into no more launchers >from the USSR, and then where would we be? Has anyone considered: a.) Buying the plans and tooling from the Soviets, and b.) Producing Energiya's (or Protons, or SL4s) here under license? If the USSR succumbs to political unrest, you can hold royalty payments in your bank account drawing interest (and maybe never have to pay ;-). ------------------------------ Date: 10 May 91 16:18:13 GMT From: cis.ohio-state.edu!sample.eng.ohio-state.edu!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!emory!ox.com!fmsrl7!wreck@tut.cis.ohio-state.edu (Ron Carter) Subject: Re: Laser launchers In article <2777@ke4zv.UUCP>, gary@ke4zv.UUCP (Gary Coffman) writes: >Sorry, but a laser launch system must carry "reaction mass" to be heated >by the laser beam. This *dead weight* produces no useful energy input. >It's mass and tankage mass must still be carried aloft by energy input ^^^^^^^^^^^^^^^^ >from the laser beam alone. Current concepts have eliminated the tankage by carrying the propellant as a solid (ice). This eliminates materials costs for the tankage and gives a huge savings in manufacturing costs; freezers are very very cheap to run and reproduce simple shapes (like slugs) quite well! Incidentally, the fuel cost of launching a rocket is a tiny part of the total cost. If LH2 costs $10/kg, the fuel for a Space Shuttle launch is only about a million bucks. Inflating the fuel cost by an order of magnitude while cutting the hardware cost by the same factor is a huge gain. >Granted that at very low altitudes the >atmosphere itself may be used as a working fluid, but above roughly >5 km the atmosphere is not dense enough to carry the energy load and >internal reaction mass must be carried. It makes little sense to carry >*dead weight* when that same mass could release useful chemical energy. Only in the naive case. There are two points to consider: 1.) Exhaust velocity. Laser propulsion can impart far more energy to a gram of propellant than can chemical reactions. This lowers the mass-ratio and the total energy required. 2.) Cost of carrying chemical fuels. They require tankage, nozzles, pumps for liquids, heavy walls for solids, and material and manufacturing for all of these. Laser propulsion has the potential to eliminate them entirely. Are you at all capable of thinking beyond the naive case? >Using a space based laser is even worse in some respects than using a >ground based laser. At least on the ground there is a large sink for >the waste heat produced in the process of generating the beam. At least >on the ground the massive tankage required for the laser reactants doesn't >have to be heaved into space. >... the mass required to be delivered to orbit to operate the >laser far exceeds the mass of fuel needed to deliver the payload directly >to orbit. Now you are assuming chemical lasers. Why would anyone carry a chemical laser, which needs reactants which are used once and exhausted, into space to launch things with? Why not excimer lasers, or free-electron lasers, or solar-UV-pumped gas lasers? When you were knocking efficiency, you were talking about electrically driven CO2 lasers on the ground (worst case, except perhaps He-Ne lasers). Now that you're bashing space-based lasers, you are talking about chemical reaction lasers (worst possible choice). You can't have it both ways! Take your straw-man engineering proposals and compost them, please. >The higher exhaust velocity for a given heat input that light molecules >like H2 give you is extremely valuable in increasing performance. You can't get any significant exhaust velocity out of H2 without supplying energy to it externally; you can't react H2 with H2. If you burn it with O2, you've got H2O. Laser-launch systems will probably use (surprise!) H2O! >The blooming problem is more than just a defocusing of the beam that >can be solved by adaptive optics. At the beam power levels required, >the atmosphere is turned to a superheated plasma.... Pray tell what those power levels are, and why we have to have these high power levels anywhere except in the immediate vicinity of the back end of the target. Tell me why we can't just plug in this power density limit as a design criterion for the optical system. >A one square inch kelvar tether to geosync orbit would weigh 45.2 million >pounds. I don't have the handbook here at the terminal, but kelvar doesn't >approach 45 million pounds per square inch tensile strength by orders of >magnitude. It couldn't support itself, much less a usable payload. More oversimplifying. This ignores reduced weight as altitude increases, tapering and improvement in materials. To quote one of the experts (lightly editted): -From: andrew.cmu.edu!hm02+ (Hans P. Moravec) -Newsgroups: sci.physics -Subject: Orbital elevators (was Ringworld) -Message-Id: -Date: 21 Nov 90 04:05:39 GMT - [material deleted] - For Earth the taper with Kevlar would be 10^11, and the cable could -hoist only about one trillionth of itys own mass -- which I admit makes -it impractical! But the required taper is exponential in the weight to -strength ratio of the material, and a material only five times better than ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Kevlar (within the measured strength/weights of single crystals of various ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -substances) would bring the taper ratio to 160 and the mass fraction to ^^^^^^^^^^^ -1/2000. So much for "physical impossibility". It is just something that materials science can't quite do today. It is quite possible. >Strength of materials ultimately depends on fundamental science. The bond >strength of elements and compounds *are* physical limits. Diamond rods >and certain graphite whiskers already approach physical limits quite >closely, and those limits are still orders of magnitude too low. "How wrong can someone be and still take himself seriously?", Ron asks himself rhetorically. >Now, now. I'm not anti-progress. I just don't see laser launchers or tethers >as the solution for sound technical reasons. So far, you have not demonstrated the soundness of your technical reasons. They sound more like closed-mindedness. I'd like to see you put numbers behind your "excessive power density" claims, a reference for your "factor of 1000 to 1000000" claim, et cetera; they would make me take you a great deal more seriously. ------------------------------ Date: 10 May 91 16:55:12 GMT From: aio!icarus.jsc.nasa.gov!dbm@eos.arc.nasa.gov (Brad Mears) Subject: Re: Saturn V and the ALS In article <1991May8.232039.532@iti.org>, aws@iti.org (Allen W. Sherzer) writes: |> First explain to me why it costs $10 billion and ten years to do what |> McDonnell and Martin say can be done for $500 million and four years. |> What's wrong with their approach? uh - less overhead? :) Seriously, I haven't seen their proposals and can't comment on them. My "seat-of-the-pants" comment is that their low-bid could be a low-ball.The quotes I saw from Rockwell to build Shuttle-C were a great deal more $500M. What will McDonnell and Martin do differently than Rockwell? |> Why is NASA the only agency who can build things? I don't want to imply that they are. I know the Navy is working on SeaLar, and I wish them luck. I restrict my comments to NASA because that is what I know about. |> What did NASA learn from the Shuttle? They learned a LOT about what goes into performing routine space operations. This is the knowledge that they hope to use in construction of the next vehicle. |> From what I see they think everything |> is fine (except that Congress should buy more orbiters). This is also not |> a flame but a serious question. I don't know how to address that. It seems to be more a matter of perception than a matter of fact. As far as asking for more orbiters, NASA asks for more because they think they need(?) a fleet with N orbiters. Until they get N, they keep asking. -- Brad Mears dbm@icarus.jsc.nasa.gov ---------------------------------------------------------------------------- Opinions are expressly forbidden. | "It is better to die on your feet I speak for myself and no other. | than live on your knees" | - Dolores Ibarruri ---------------------------------------------------------------------------- ------------------------------ Date: 9 May 91 17:15:16 GMT From: usc!rpi!crdgw1!gecrdvm1!gipp@ucsd.edu Subject: Re: Why the space station?y In article <1991May9.031802.15344@agate.berkeley.edu>, fcrary@headcrash.Berkeley.EDU (Frank Crary) says: > >In article <1991May8.132202.1@vf.jsc.nasa.gov> kent@vf.jsc.nasa.gov writes: > >I was talking about the difficulties of manuvering into close proximity to the >station (or any large, open structure). While the RMS will do fine for the >final docking, that arm is only 15 meters long. Alot of effort may be >needed to get within 15 meters of the dacking adaptor without hitting the >trussd, solar pannels or heat radiators. This is a particular problem is >there is a docking failure. For example, due to a damaged radar beacon >the Progress M7 resupply craft almost rammed the Mir space station. A >ground controlled noticed in time, and aborted the docking. As the >Progress passed the station (after failing to dock) it nearly hit a solar >pannel. I feel this sort of accident is a much greater risk for Freedom, >with so many things sticking out in so many directions. > > Frank Crary > UC Berkeley I thought I read something about this in a recent AW&S(forget the last letter). If I recall correctly, concern was greater now that Freedom has shrunk (as if adding a mountain of papers to something non-existant can make it shrink) due to the lack of manuevering space and the need to be that much more precise so as not to hit the closer modules. Henry will probably write about it in a couple of months when he does his summary of the issue :-). ------------------------------ Date: 10 May 91 04:37:04 GMT From: VAX1.CC.UAKRON.EDU!mcs.kent.edu!usenet.ins.cwru.edu!agate!lightning.Berkeley.EDU!fcrary@tut.cis.ohio-state.edu (Frank Crary) Subject: Re: Ethics of Terraforming (was Re: Terraforming Venus) In article <265@rins.ryukoku.ac.jp> will@rins.ryukoku.ac.jp (will) writes: > >...It is strange that humanity > thinks that in order for intelligent life to exist somewhere there must > be citys and space shuttles at least before it is considered intelligent > No, we think that there must be: 1) water, or at least SOME liquid to act as a solvent. 2) lower, e.g. less evolved, forms of life 3) ANY complex organic chemicals AT ALL on the surface. The viking life science experiments were tested in the most desolate places possible, including the dry valleys in antarctica. Even 100's of km from ANY life, they still gave positive results. On Mars they\ did not. Even the idea of life evolving on Mars before the climate went cold does not mean intelligent life. At most it means coral or such like. At worst, it means pond scum. > Also, if there was life before, and it was lost, it should be discovered > and studied. A lot must be done before we go and wipe out a planet just > for our own use. Seems very selfish to me. It may very well be selfish. However I am an avowed racist: I am strongly biased in favor of the human race. If the growth and welfare of the human race requires the loss of fosilized Martian pond scum, or even now living micro organisims, I say the Martians loose. Frank Crary UC Berkeley ------------------------------ Date: 9 May 91 17:45:32 GMT From: brody@eos.arc.nasa.gov (Adam R. Brody) Subject: Barbara Boxer Anybody know Barbara Boxer's views on space? I just got a solicitation for some campaign funds and was wondering if she was worthy of any. ------------------------------ Date: 30 Apr 91 17:47:31 GMT From: att!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!wuarchive!rex!rouge!dlbres10@ucbvax.Berkeley.EDU (Fraering Philip) Subject: Re: NASP In article <00947E5F.80DDF5C0@KING.ENG.UMD.EDU> sysmgr@KING.ENG.UMD.EDU (Doug Mohney) writes: >NASP is quite probably liberally building on "Aurora" and other black >hypersonic projects. What if it isn't? I get the strong feeling that a lot of duplication of effort is going on. -- Phil Fraering dlbres10@pc.usl.edu Joke going around: "How many country music singers does it take to change a light bulb? Four. One to change the bulb, and three to sing about the old one." ------------------------------ Date: 11 May 91 20:03:20 GMT From: cleveland.Freenet.Edu!ak104@ucbvax.Berkeley.EDU (Robert Clark) Subject: 2001 and NASP Has anyone noticed the remarkable resemblance between the proposed National Aerospace Plane and the space transport in 2001: A Space Odyssey? Chalk up another one for Kubrick and Clarke. ------------------------------ Date: 12 May 91 19:09:09 GMT From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!samsung!news.cs.indiana.edu!maytag!watmath!watdragon!watyew!jdnicoll@tut.cis.ohio-state.edu (James Davis Nicoll) Subject: Re: 2001 and NASP In article <9105112003.AA19893@cwns10.INS.CWRU.Edu> ak104@cleveland.Freenet.Edu writes: > > Has anyone noticed the remarkable resemblance between >the proposed National Aerospace Plane and the space transport >in 2001: A Space Odyssey? > Chalk up another one for Kubrick and Clarke. Wasn't the space plane in 2001 nuclear powered (NERVAesque, if I recall correctly)? James Nicoll ------------------------------ End of SPACE Digest V13 #545 *******************