Date: Fri, 24 Feb 1989 11:57-EST From: space-tech-request@cs.cmu.edu To: "~/st/lists/stdigest" Subject: Space-tech Digest #26 Contents: Larry Klaes The MIRROR MATTER Newsletter. Steve Hayhurst Cassini Simulation pkg (SD #197 Vol 9) Paul Dietz Railgun Launcher by 1995 Mike Van Pelt Railgun launcher as weapon Paul Dietz Re: Railgun Launcher by 1995 Matthew Francey Re: Railgun Launcher by 1995 Paul Dietz Re: Railgun Launcher by 1995 Jordin Kare Re: Railgun Launcher by 1995 Paul Dietz Re: Railgun Launcher by 1995 Jordin Kare Re: Railgun Launcher by 1995 Henry Spencer Re: Railgun Launcher by 1995 Tom Neff RV velocity & railgun ------------------------------------------------------------ Date: 8 Feb 89 09:50 From: klaes%mtwain.DEC@decwrl.dec.com (CUP/ML, MLO5-2/G1 8A, 223-3283) To: space-tech@cs.cmu.edu Subject: The MIRROR MATTER Newsletter. Robert Forward, author of such books as MIRROR MATTER: PIONEERING ANTIMATTER PHYSICS, FUTURE MAGIC, STARSAILING, and the "hard" science fiction novels DRAGON'S EGG, STARQUAKE, and FLIGHT OF THE DRAGONFLY, is also publishing the MIRROR MATTER NEWSLETTER, an informal, aperiodically issued newsletter on the scientific, medical, and technological applications of stored antimatter. The newsletter is sent free to those with a serious (or just plain curious) interest in the subject. If you wish to be placed on the mailing list to receive MIRROR MATTER, please write to: Robert L. Forward Editor, MIRROR MATTER NEWSLETTER P.O. Box 2783 Malibu, California 90265-7783 U.S.A. Telephone: (805) 983-7652 The above address is also used for changes of address, letters to the editor, and contributed items. Larry Klaes ------------------------------ Date: Thu, 23 Feb 89 16:35 EST From: To: SPACE-TECH@CS.CMU.EDU Subject: Cassini Simulation pkg (SD #197 Vol 9) Distribution-File: SPACE-TECH@CS.CMU.EDU I was wondering wether anything further on the Xlisp simulation (or any simulation) packages posted (SPACE DIGEST #197 Vol. 9) by Adrian Ho had been heard about? Also, I would like to find a source for the following: specifications for CRAF, TRDS, IUS, etc. Simulation software (either PC, Mac, or VMS [5.0] preferred) or a distribution list for a discussion group) Information regarding data accessibility/compatibility from the HST for amateur astronomers (through NASA?, through SSI?, free 8'D?) Is there more info available on the CMU Mars Rover (AMBLER) project? Is anyone interested in doing a think-tank paper project on planning a Mars manned mission (e.g. multi-national, of course!) which would require researching the spec's for a nation's space vehicle technology? Interfacing different systems together? Just curious & thanks in advance! - Steve Hayhurst HAYHURS@IUBACS ->BITNET HAYHURS@IUBACS.GOLD.BACS.INDIANA.EDU ->INTERNET ------------------------------ Date: Tue, 21 Feb 89 17:20:44 EST From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Railgun Launcher by 1995 The March 1989 issue of Discover has a two page article on railguns for launching payloads into space. Very interesting. Miles Palmer, who works for SAIC, is quoted as saying that a railgun capable of launching 1000 pound objects into orbit could be developed for $300 M and be in operation by 1995. The launch cost, including amortized development cost, could be as little as $10 to $40 per pound. The article quotes two objections: lack of commercial market, and tight budgets. Frankly, this is silly. The major market would initially, I think, be military. Consider: an object impacting at 10 km/s has a kinetic energy equal to the chemical energy in over ten times its mass in high explosives. A railgun launcher would let you launch objects that could be deorbited anywhere, anytime, without the need to risk US aircraft or soldiers. At $1-4/pound of TNT equivalent, it would a cheap way to carpet bomb any large fixed target, like (for example) a nerve gas factory, an oil terminal, or an air base. One could even warn the enemy well ahead of time that the target would be destroyed -- there is nothing he could do except evacuate. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Tue, 21 Feb 89 17:35:40 PST From: v7fs1!mvp@apple.com (Mike Van Pelt) To: space-tech@cs.cmu.edu Subject: Railgun launcher as weapon Paul F. Dietz (dietz@cs.rochester.edu) says: >... The major market would initially, I think, be military. Of course, "all the usual people" are going to completely freak out as soon as any such proposal is mentioned. This sounds a lot like the "Thor" system that Jerry Pournelle talks about from time to time. (A pretty good description of how devastating this can be is what happens to the Kansas National Guard in "Footfall".) With the railgun approach, you could avoid the provocative initial step of orbiting the weapon canisters; just launch them on a ballistic trajectory if and when needed. Note that it doesn't have to be a large fixed target, though that's certainly the easiest target. The Thor proposal was to de-orbit "smart flying crowbars", with enough smarts to locate and home in on tanks. -- Mike Van Pelt Video 7 ...ames!vsi1!v7fs1!mvp "... Local prohibitions cannot block advances in military and commercial technology.... Democratic movements for local restraint can only restrain the world's democracies, not the world as a whole." -- K. Eric Drexler ------------------------------ Date: Wed, 22 Feb 89 08:45:07 EST From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Re: Railgun Launcher by 1995 In case I didn't make it clear, the note about the railgun launcher did not advocate its use in a military context. A decision to build or use such a weapon would be political in nature; discussion of the merits of such decisions does not belong in this list. Rather, I was merely pointing out that at least one money-laden customer exists, and that it would make technical sense to use the launcher in this way. If the military were to build such a device, it would be natural to divert some of its time to launching non-military payloads. We should not forget that rocket boosters are also military spinoffs. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Wed, 22 Feb 89 12:26:10 EST From: mdf@ziebmef.uucp To: space-tech@cs.cmu.edu Subject: Re: Railgun Launcher by 1995 > Frankly, this is silly. The major market would > initially, I think, be military. [ then outlines some of the marvelous military applications of this rail launcher ] You have got to be joking. Do you really think that after the military has been given this wonderful weapon that they will surrender it for non-military use, once this supposed initial period is over? -- Name: Matthew Francey Address: N43o34'13.5" W79o34'33.3" 86m mdf@ziebmef.UUCP uunet!utgpu!{ontmoh!moore,ncrcan}!ziebmef!mdf ------------------------------ Date: Wed, 22 Feb 89 17:24:34 EST From: dietz@cs.rochester.edu To: mdf@ziebmef.uucp Cc: space-tech@cs.cmu.edu Subject: Railgun Launcher by 1995 > You have got to be joking. Do you really think that after > the military has been given this wonderful weapon that they will > surrender it for non-military use, once this supposed initial > period is over? You are laboring under the curious delusion that at most one of these things would be built. If the military does the development work and proves the concept, NASA and others would be more than willing to build copies, assuming the cost is as low as is claimed. After all, $300 M (caveat emptor) is about the cost of one shuttle launch, and that figure includes development costs, which the 2nd copy would not have to pay. There is ample precedent -- what are rocket boosters, if not descendents of ICBMs? Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Wed, 22 Feb 89 12:35:35 PST From: Jordan Kare To: space-tech@cs.cmu.edu Subject: Re: Railgun launcher Paul Dietz cites a claim that a railgun launch-to-orbit could be built by 1995. From all that I have heard about both rail gun and EM launchers (coil guns) for orbital velocities they are technologies whose time has passed. Chemical launchers, notably Abe Hertzberg's ram cannon, are substantially simpler and cheaper to build, and are at roughly the same level of development (i.e. lab tests with gram-sized projectiles). Of course, for $300 million (well, $500 million), I could build you a laser launch system that would do much the same job, and subject its payloads to only 5 gees instead of 50,000 :-) With regard to military uses, intercontinental direct bombardment tends to be of limited use because the launch rate is low -- except for rather specialized operations like destroying a single factory. Bear in mind that defense is not all that difficult; terminal velocity for a small reentering vehicle is much lower than orbital velocity, and concrete is cheap. Project Thor (massed attacks against relatively lightly armored targets, like tank topsides, using projectiles stored in orbit) requires fairly smart and very cheap projectiles, in which the military is reluctant to believe. Besides, the US military seems to have a fairly substantial bias against small, cheap, unmanned vehicles :-( Jordin Kare ------------------------------ Date: Wed, 22 Feb 89 17:48:50 EST From: dietz@cs.rochester.edu To: jtk@mordor.s1.gov Cc: space-tech@cs.cmu.edu > From all that I have heard about both rail gun and EM > launchers (coil guns) for orbital velocities they are technologies > whose time has passed. Chemical launchers, notably Abe Hertzberg's > ram cannon, are substantially simpler and cheaper to build... I think I agree; the ram accelerator does look impressively simple. Jordan claimed (with smiley) that for $500 M one could develop a laser launch system that would subject its payloads to only 5 gees. Since this is space-tech, would Jordan comment on the potential problems arising in propagation of intense pulsed laser beams through the atmosphere? I do not know the limits on the propagation of intense pulsed laser beams. At what point do thermal blooming, SRS, plasma formation, etc. become problems, and are there fixes? > With regard to military uses, intercontinental direct bombardment > tends to be of limited use because the launch rate is low -- Store RVs in orbit, as in Thor. > Bear in mind that defense is not all that > difficult; terminal velocity for a small reentering vehicle > is much lower than orbital velocity, and concrete is cheap. I was thinking of reentry vehicles with a mass on the order of 1000-2000 pounds. After all, if the RV can punch *up* through the atmosphere after launch, retaining most of its velocity, shouldn't it do the same on the way back down? Large RVs would also amortize the cost of the control and guidance systems over a larger mass. Naively, I'd expect a dense 1000 pound object traveling at near orbital velocity to make a large crater, concrete or not. If necessary, one could arrange the RV to fragment into unguided subunits before impact, so as to spread the damage. Again, this is for use against large fixed targets, not tanks. > Besides, the US military seems to have a fairly substantial bias > against small, cheap, unmanned vehicles :-( I would have thought that the US Army would love "intercontinental artillery". Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Wed, 22 Feb 89 17:06:41 PST From: Jordan Kare To: dietz@cs.rochester.edu, jtk@mordor.s1.gov Cc: space-tech@cs.cmu.edu > >Jordan claimed (with smiley) that for $500 M one could develop a laser >launch system that would subject its payloads to only 5 gees. The smiley referred to the fact that, as someone actively involved in developing laser propulsion, I am probably a bit biased. Nonetheless, I think the cost (and 5+ year time scale) are correct. By the way, despite what my message headers say, it's Jord_i_n. > Since >this is space-tech, would Jordan comment on the potential problems >arising in propagation of intense pulsed laser beams through the >atmosphere? I do not know the limits on the propagation of intense >pulsed laser beams. At what point do thermal blooming, SRS, plasma >formation, etc. become problems, and are there fixes? Rough numbers and explanations -- SRS (stimulated Raman scattering, aka Raman conversion or just Raman) involves air molecules frequency-shifting the laser beam. It is a gain phenomenon (i.e. the air acts like a lasing medium "pumped" by the original beam) and the gain is a function of beam flux. The gain varies with air pressure and density, but in opposite directions, so the gain is constant up to about 40 km altitude; then it falls off exponentially. Thus it doesn't hel p to put your laser on a mountain, but it helps a lot if you don't have to focus down on anything below 40 km. The thresholds are of order 10^7 watts/cm^2 to get thru the atmosphere at 1 micron; the threshold scales roughly with wavelength, so long wavelengths don't have raman problems. Peak flux is what counts, so one way to beat Raman is to stretch your laser pulses (same average energy, lower peaks.) There are other tricks as well, about which I know little. Raman is probably not a problem for laser propulsion -- not at all for 10 micron systems (my preference) and probably tolerable even at 1 micron provided the ground-based mirror is big enough (imagine a conical beam-- wide down where the atmosphere is, narrow 200 km up where the vehicle is). Plasma formation is not a problem in clear air; the thresholds are 10^9 w/cm^2 or so. Plasma formation on dust particles happens around 10^7 w/cm^2 and tends to limit the flux you can bounce around your launch site (say, to get the beam from the laser to the telescope); the flux at the telescope itself is again _usually_ too low to cause a problem, but may be a minor worry. I just recently helped a friend who is an SF author design a scene in which terrorists sabotage a laser launcher by exploding a "dust bomb" to fill the beam path with breakdown sites -- for about 10 ms, until the safety systems kill the beam, it's a really impressive flashbulb! The major problems are turbulence and thermal blooming and their interaction. Turbulence is what makes stars twinkle; it can be corrected by an adaptive optics system ("rubber mirror") fairly easily if a beacon signal is available (easy to do with a cooperative target). Thermal blooming happens when laser energy is absorbed by the air, which heats up and expands. You get a density profile which acts as a lens, diverging the beam. This depends heavily on the absorption coefficients of the air; 10 micron CO2 blooms relatively badly because both water vapor and atmospheric CO2 absorb the beam. Water vapor can be beaten by putting the laser on a mountaintop (say, above 10,000 feet) and not operating when conditions are bad. CO2 can be tolerated, or beaten by running the laser off the main CO2 lines, either by filling the laser with isotopic CO2 or by using an FEL instead. (one neat trick involves the dynamics of the CO2-nitrogen interaction; it is actually possible to cool the air -- extrac t translational energy from N2, and put the energy into CO2 vibrations -- under some circumstances. Kids, don't try this at home!) LArge-scale blooming can also be corrected with adaptive optics. The problem occurs when both blooming and turbulence are present. There are feedback processes that cause the beam to break up -- filament -- and be lost. Unfortunately, adding adaptive optics makes the process _worse_ -- consider a spot which is hot, and thus defocuses the beam. The beacon beam comes down, and is defocused. The adaptive optics responds by focussing the main beam to compensate -- but that puts _more_ energy into the hotspot, so it gets hotter. This way madness lies. You can beat this by controlling bothphase and amplitude in the adaptive system, which no one knows how to do in practice. Just how bad this really is, and how to beat it without major advances in technology, is a very hot topic these days. Fortunately for laser propulsion, the problem is much smaller at long wavelength (all the time scales and sizes get much bigger, and the interaction between blooming and turbulence can probably be decoupled) -- and if we have to work at short wavelength, it will be because people are building short wavelength lasers, which will mean the problem has already been solved... > >> Bear in mind that defense is not all that >> difficult; terminal velocity for a small reentering vehicle >> is much lower than orbital velocity, and concrete is cheap. > >I was thinking of reentry vehicles with a mass on the order of >1000-2000 pounds. After all, if the RV can punch *up* through the >atmosphere after launch, retaining most of its velocity, shouldn't it >do the same on the way back down? Proposed cannon-launch systems typically waste 25% -50% of their energy getting up through the atmosphere; launch is at 10 km/s to get out of the atmosphere at 8 km/s. The energy loss is similar coming down, and may be considerably worse because you may re-enter at a shallower angle than you launched at -- cannon launchers tend to launch into high ellipses and circularize the orbit with one big burn or two little one; if you store projectiles in orbit you either need to carry lots of "reentry burn" fuel or have long delays and/or high "absentee ratios" when you decide to reenter. You also ablate away a noticeable fraction of your inital mass on the way up. There are also subtleties which tend to make things worse; for instance, you can stand the Mach 25 thermal loads on launch because you spend so little time in the low atmophere; the loading is much worse if you try to reenter steeply and go into the low atmosphere at mach 10 - 15. And remember that most of the cannon launchers assume the launch point is on a mountain at 3-4 km altitude, whereas few targets are; that cuts out over a third of the atmosphere. >Large RVs would also amortize the >cost of the control and guidance systems over a larger mass. Naively, >I'd expect a dense 1000 pound object traveling at near orbital >velocity to make a large crater, concrete or not. Again, if you could hit the ground at 8 kms, this would be true, but I don't think you can. And at, say, 3 kms I suspect you are only doing the same sort of damage as a 1000-lb bomb or shell -- not negligable, but not impossible to protect against. Incidentally, you may have considerable trouble with your guidance even at 3 kms; a major problem with hypervelocity missiles (ones that kill, e.g., tanks, by sheer kinetic energy) is that it's very hard to build optical or radar-transparent noses for them... If necessary, one >could arrange the RV to fragment into unguided subunits before impact, >so as to spread the damage. Again, this is for use against large >fixed targets, not tanks. You almost certainly do better against all but unarmored targets (aka people) with single rounds. Exception: killing airport runways and exposed grounded aircraft. > >> Besides, the US military seems to have a fairly substantial bias >> against small, cheap, unmanned vehicles :-( > >I would have thought that the US Army would love "intercontinental artillery". > > Paul F. Dietz > dietz@cs.rochester.edu Only if they could hit tanks with it. The army pretty much turned the long range bombardment job over to the Air Force after WWII. Jordin (Don't fire until you see the whites of their icecaps) Kare ------------------------------ Date: Thu, 23 Feb 89 12:54:31 -0500 From: attcan!utzoo!henry@uunet.UU.NET To: dietz@cs.rochester.edu Cc: space-tech@cs.cmu.edu Subject: Re: Railgun Launcher by 1995 Just to play Devil's Advocate... > You are laboring under the curious delusion that at most one of these > things would be built. If the military does the development work and > proves the concept, NASA and others would be more than willing to > build copies, assuming the cost is as low as is claimed. After all, > $300 M (caveat emptor) is about the cost of one shuttle launch, and > that figure includes development costs, which the 2nd copy would not > have to pay... Unless, of course, NASA added some new specs to the deal... which they almost certainly would. They've got that disease just as badly as the USAF. Also, the above assumes rational decision-making on the part of NASA and Congress. It would clearly be rational, today, to mount one less shuttle launch per year and spend the money on the most promising-looking private launcher proposal -- many of those proposals could get by with less than that as seed money. After five years, the odds are good that at least one, possibly several, cheap launchers would be well advanced in development. That's assuming you want government-funded development; an even better alternative is to offer that money as payment for mass orbited successfully. That leaves startup funding to private sources but guarantees a return on a technically-successful development effort. However, don't hold your breath waiting for either of these to happen. The funding process is not rational, and it's a mistake to think that everyone involved even would *like* it to be rational. Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: Thu, 23 Feb 89 09:02:29 PST From: well!tneff@apple.com (Tom Neff) To: jtk@mordor.s1.gov, uunet!cs.rochester.edu!dietz@apple.com Subject: RV velocity & railgun Cc: space-tech@cs.cmu.edu Paul Dietz writes: >I was thinking of reentry vehicles with a mass on the order of >1000-2000 pounds. After all, if the RV can punch *up* through the >atmosphere after launch, retaining most of its velocity, shouldn't it >do the same on the way back down? I don't think the railgun depends on the payload "retaining most of its velocity" on the way up. In the absence of continuous thrust, atmospheric friction is going to take away a hefty chunk of the initial velocity, subject to whatever clever aerodynamics we're able to think up. The trick with the railgun is to start out so *fast* that what you have left after drag robs you blind is still enough to make orbit. >From that point on our hypothetical RV has to make do with garden variety orbital momentum as a starting point for its trip down. That second trip thru the air ocean will indeed bleed off more speed! Large RVs would also amortize the >cost of the control and guidance systems over a larger mass. If we assume that the objective of such a weapon is to neutralize targets, not to put mass in space for its own sake, then this looks like a false amortization. It is going to cost X dollars in electronics to take out a target whether the hardware is strapped to a boulder or a crowbar. Naively, >I'd expect a dense 1000 pound object traveling at near orbital >velocity to make a large crater, concrete or not. Yet consider the class of half-ton meteorites; there are several specimens mounted in the yard and halls of the American Museum of Natural History near my apartment. How does a half-ton rock go from solar orbit (higher energy than LEO) to the floor of the Negev in one piece? Of course many are fragments of larger bodies, and in all cases most of the mass vaporized in the atmosphere before impact. If you really START with a half-ton planetesimal, you end up with something much smaller after impact; specimens are not too uncommon. I would not care to be sitting underneath one of these babies, but we are not talking about the Winslow Crater either. REAL craters are formed when the meteoroid and upper Earth crust in the imact area both vaporize explosively. Naively I don't think we're in that league here. I would welcome someone running the numbers. If necessary, one >could arrange the RV to fragment into unguided subunits before impact, >so as to spread the damage. Again, this is for use against large >fixed targets, not tanks. Of course, that cuts your impact momentum down drastically. You could play hell with a refinery this way, but hardened silos would laugh at it. Let's face it, if you want to reenter something from orbit and do as much damage as possible per dollar, you want a real bomb -- a nuke. Railgun nukes into eccentric orbits and terrorize the world! That's basically why the treaty was signed 25 years ago, and why we still need it. The current Dietz proposal is a variant you might call "duds in space." It's fun to discuss since it would never, never, never pass. ------------------------------ End of Space-tech Digest #26 *******************