Date: Mon, 10 Feb 1992 11:10-EST From: space-tech-request@cs.cmu.edu To: "~/st/lists/stdigest" Subject: Space-tech Digest #100 Sender: mnr@DAISY.LEARNING.CS.CMU.EDU Contents: Solar sailing (13 msgs) Fiberglass Info Request (2 msgs) Metstable Helium Info Request (2 msgs) ------------------------------------------------------------ Date: Mon, 3 Feb 92 18:24:07 -0600 From: ewright@bach.convex.com (Edward V. Wright) To: gwh@lurnix.LURNIX.COM, zoo.toronto.edu!henry@tcsi.tcs.com Subject: solar sailing Cc: space-tech@cs.cmu.edu >[btw: Henry and I had a long conversation at Usenix on several random >aerospace topics, and up came an idea of his to build a model-airplane >(ok, more like 10kg he said after I asked for clarification) sized >solar said demonstrator and launch it like the amateur radio satellites >are launched, as ballast on comsats etc. >It would be an extremely interesting project, and not that demanding >due to small size. ] Would this be significantly smaller/cheaper than the solar sails being developed for the World Space Foundation's "Columbus 500" race? ------------------------------ Date: Tue, 4 Feb 92 12:23 PST From: trost@reed.edu (Bill Trost) To: space-tech@cs.cmu.edu Subject: solar sailing Edward V. Wright writes: >[btw: Henry and I had a long conversation at Usenix on several random >aerospace topics, and up came an idea of his to build a model-airplane >(ok, more like 10kg he said after I asked for clarification) sized >solar said demonstrator and launch it like the amateur radio satellites >are launched, as ballast on comsats etc. Would this be significantly smaller/cheaper than the solar sails being developed for the World Space Foundation's "Columbus 500" race? (A little) more detail, and some questions, on this. The Columbus 500 race is solar yacht race scheduled for sometime this year. They are supposed to race to Mars(!) and back. _Ad Astra_ described a few of the groups interesting, but (oddly enough :-) ) I don't keep that magazine at my fingertips. Now, for the questions: What shape of sail would you use for something like this? Apparently, the two popular sail shapes are square sails (stacked tall on three masts...no, wrong ships :-) ) and a kind of arrangement were the sails are held in place by centrifugal force (a NASA design). Essentially, you take two counterrotating rings, and hang rolls of aluminum foil off them. The spinning of the rings makes the aluminum foil roll out to full length and holds them there, providing your sail area. I have no idea how the shape of such a sail is controlled for manuevering -- I assume that the shape/orientation/position of the sail is changed to maneuver the ship, since trying to thrust a rotating structrure is a real pain. Also, how will such a ship steer itself? Presumably, you want to be able to tell it to orient itself in a certain way with respect to the Sun. Probably, you track shadows of little sticks on the front of the sail or ship to determine your orientation. Of course, you probably need something more clever to manuever in a planetary gravity well, but the essential principle might be the same. ------------------------------ Date: Tue, 4 Feb 92 15:57:25 -0600 From: ewright@bach.convex.com (Edward V. Wright) To: space-tech@cs.cmu.edu, trost@reed.edu Subject: Re: solar sailing >The Columbus 500 race is solar yacht race scheduled for sometime this >year. They are supposed to race to Mars(!) and back. _Ad Astra_ >described a few of the groups interesting, but (oddly enough :-) ) I >don't keep that magazine at my fingertips. The Columbus 500 race was scheduled for this year, but has been postponed (until 1994, I believe) because of financial difficulties. The race is actually to the Moon (or to the Moon's orbit, rather), although one of the three teams (the American one) does intend to go on to Mars. The solar-sail designs I've seen discussed most often are a square, supported by two masts in the shape of a letter "X"; a disk, supported by centifugal force; and what designers called a "heliogyro," shaped like a wagon wheel but without the rim and also supported by centrifugal force. The American team is using a square sail. The Japanese and European teams I'm not sure about. If I recall correctly, each of the vehicles will cost around a million dollars -- not much by NASA standards, but still a fair piece of pocket change. Is it possible to do better than this? One major problem, of course, is deploying the sail: satellites seem to have problems deploying much smaller solar panels, antennas, etc. all the time. I remember that ~10 years ago, Edmund Scientific had in its catalog a metal alloy with a very interested property: it could remember its shape. Bend it to the shape you wanted, heat it to a high temperature to "set" the shape, then, after it's cool, you can scrunch it up and when it's heated slightly it will revert to the original shape. I believe the alloy was called 99-Nitinol. Could something like this be used to deploy a solar sail without needing any mechanical device (which might jam) antennas, etc. all the time. I remember that ~10 years ago, Edmund Scientific had in its catalog a metal alloy with a very interested property: it could remember its shape. Bend it to the shape you wanted, heat it to a high temperature to "set" the shape, then, after it's cool, you can scrunch it up and when it's heated slightly it will revert to the original shape. I believe the alloy was called 99-Nitinol. Could something like this be used to deploy a solar sail without needing any mechanical device (which might jam)? ------------------------------ From: henry@zoo.toronto.edu Date: Tue, 4 Feb 92 17:46:05 EST Cc: Bill Trost To: space-tech@cs.cmu.edu Subject: Re: solar sailing >The Columbus 500 race is solar yacht race scheduled for sometime this >year. They are supposed to race to Mars(!) and back. Uh, no, not quite. The idea was to race to Mars, one way. And everyone involved is far behind schedule and the chances of a launch this year are roughly nil, last I heard. (The big problem is that the Columbus Cup organizers simply did not come through on the fundraising end.) >What shape of sail would you use for something like this? Apparently, >the two popular sail shapes are square sails (stacked tall on three >masts...no, wrong ships :-) ) and a kind of arrangement were the >sails are held in place by centrifugal force (a NASA design). The heliogyro. Actually there were several other shapes, like the British potato chip that maneuvered by warping its surface, and the Canadian one that was a giant set of Venetian blinds. Using centrifugal force to maintain the shape of your sail is a big win on structural mass and such. However, it's not a win if you are doing something requiring a lot of maneuvering, such as starting from Earth orbit (especially not-too-high Earth orbit), since maneuvering something with that much angular momentum is difficult. (The problem with starting from Earth orbit is that you have to raise your orbit gradually over many revolutions, and you want full thrust on the half of the orbit moving away from the Sun and none on the half moving toward the Sun. Unless you have some thrust-modulation technique, like the CSSP's Venetian-blind design, this means turning the sail 90 degrees twice per orbit.) >Also, how will such a ship steer itself? Presumably, you want to be >able to tell it to orient itself in a certain way with respect to the >Sun. Probably, you track shadows of little sticks ... Sun sensors are simple, cheap, and well understood. There is somewhat of a problem in that this only gives you two axes, and you want three. The third axis is a headache; star sensors are not so simple and cheap. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ From: henry@zoo.toronto.edu Date: Tue, 4 Feb 92 18:31:25 EST Subject: small sails To: space-tech@cs.cmu.edu >>... up came an idea of his to build a model-airplane >>(ok, more like 10kg he said after I asked for clarification) sized >>solar said demonstrator and launch it like the amateur radio satellites >>are launched, as ballast on comsats etc. > >Would this be significantly smaller/cheaper than the solar sails >being developed for the World Space Foundation's "Columbus 500" >race? A lot. The Columbus Cup sails were looking to be up in the hundreds of kg, although I no longer remember any very specific numbers. Those were to have significant scientific payload, little imaging systems, etc., including a 1kg plaque. I started thinking about smaller-scale projects, and decided that I couldn't think of any reason why you couldn't build a sail the mass of the larger model aircraft (radio-controlled models can get pretty hefty). The sail itself would have to be of substantial size, but in space that's no big deal; indeed, one big trick is deploying the thing slowly and gently so fragile sail material and structural members aren't damaged by over-fast deployment (no air resistance to slow them down, remember). Most of the subsystems seem to miniaturize well. The biggest unknown I could come up with was how much mass you'd need to budget for communications; it's not an area I'm up on. (It's also one of the big headaches for operating out near Mars, as per the original Columbus Cup competition. Operating near Earth is a lot easier.) I was envisioning something small, launched piggyback by some friendly primary payload rather than as a paying customer, with a relatively short intended lifetime and a specifically experimental status. The amount of effort and money involved scale up dramatically as you try to make the thing last a long time and work with 99.9999% assurance. Better would be to aim for a series of them, and expect to wear them out fast and lose a few. Comments would be welcome. I really haven't pursued this in enough depth yet to find potential show-stoppers. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Tue, 4 Feb 92 17:10:17 -0600 From: ewright@bach.convex.com (Edward V. Wright) To: henry@zoo.toronto.edu, space-tech@cs.cmu.edu Subject: Re: solar sailing Cc: , zoo.toronto.Bill@edu.convex.com, zoo.toronto.Trost@edu.convex.com >(The problem with starting from Earth orbit is that you have to raise >your orbit gradually over many revolutions, and you want full thrust >on the half of the orbit moving away from the Sun and none on the half >moving toward the Sun. Unless you have some thrust-modulation technique, Another problem is that if you start with an orbit too low, atmospheric drag will cause it to decay faster than your solar sail can compensate. So, there's a practical floor below which solar sails can't operate without some form of auxiliary propulsion. (I have a figure of 1400 in the back of my mind, but I'm not sure if that's miles or kilometers, if it's even accurate.) ------------------------------ Date: Tue, 4 Feb 92 16:43:32 PST From: David.Michelson@mtsg.ubc.ca To: space-tech@cs.cmu.edu Subject: Columbus 500 What altitude would the proposed solar sailing race start from? (I'd hate to start from a standard shuttle orbit unless we were racing to the ground!) Dave ------------------------------ Date: Tue, 4 Feb 92 16:58 PST From: trost@reed.edu (Bill Trost) Subject: Re: solar sailing to: space-tech@cs.cmu.edu (The problem with starting from Earth orbit is that you have to raise your orbit gradually over many revolutions, and you want full thrust on the half of the orbit moving away from the Sun and none on the half moving toward the Sun. Unless you have some thrust-modulation technique, like the CSSP's Venetian-blind design, this means turning the sail 90 degrees twice per orbit.) Uhm...I thought you could get useful thrust though most of the orbit. Solar sails direction of force isn't away from the Sun, it's in the direction of the sail facing away from the Sun. Admittedly, you get the *best* thrust when you're pointed directly away from the Sun, but it still seems like you should be able to use a fair amount of the orbital thrust to your advantage -- on the part of the orbit heading towards the Sun, you essentially try to use what little "outward" force you have available. Or maybe I'm not clear on the dynamics of this. ------------------------------ Date: Tue, 4 Feb 92 12:08:15 PST From: gwh@krupke.com (George W Herbert) To: space-tech@cs.cmu.edu, uunet!back.convex.com!ewright@uunet.UU.NET Subject: Re: small solar sails All the "race" solar sail sats were in the hundreds-of-kg range, as far as I know. The problem was finding launchers, which Henry gave a long and painful discussion of when I talked to him (he was very involved in the Canadian team). -george william herbert gwh@ocf.berkeley.edu gwh@lurnix.lurnix.com ------------------------------ From: henry@zoo.toronto.edu Date: Wed, 5 Feb 92 15:23:41 EST To: Bill Trost Subject: Re: solar sailing Cc: space-tech@cs.cmu.edu >Uhm...I thought you could get useful thrust though most of the orbit. >Solar sails direction of force isn't away from the Sun, it's in the >direction of the sail facing away from the Sun... >... seems like you should be able to use a fair amount of the >orbital thrust to your advantage -- on the part of the orbit heading >towards the Sun, you essentially try to use what little "outward" >force you have available. I haven't investigated it in detail myself, but my gut reaction is that the outward force basically isn't *doing* anything useful. Maneuvering in a gravity field whose strength is many times the sail thrust, gaining velocity is much more productive than opposing the field directly... and the price of that outward force is velocity loss due to the "backward" component. ------------------------------ From: henry@zoo.toronto.edu Date: Wed, 5 Feb 92 15:30:24 EST To: David.Michelson@mtsg.ubc.ca Cc: space-tech@cs.cmu.edu Subject: Re: Columbus 500 >What altitude would the proposed solar sailing race start from? ... This wasn't clear, last I heard (although I may be out of date). You would really like to start from something like Clarke (geostationary) orbit, away from air drag and outside the damned Van Allen belts, and there was talk of a shared launch to a suitable orbit. The rule of thumb we used for launcher screening was that anything below 1000km was useless. This is, unfortunately, just about where the Van Allen belts start to get serious, which is really bad for the lifetime of the electronics. Piggybacking unfortunately won't get you to Clarke orbit. About the best you can do is transfer orbit, with apogee at Clarke orbit and perigee quite low. This might be good enough. If the long axis of the orbit is more or less perpendicular to the Sun axis, you've got useful thrust over most of the orbit. The air drag at perigee is troubling, but repeated passages through the belts are worse. ------------------------------ Date: Wed, 5 Feb 1992 17:48 EST From: "GORDON D. PUSCH" Subject: Re: solar sailing To: space-tech@cs.cmu.edu >>Uhm...I thought you could get useful thrust though most of the orbit. >>Solar sails direction of force isn't away from the Sun, it's in the >>direction of the sail facing away from the Sun... (i.e., parallel to the *antisunward* normal to the sail's surface. note that this assumes a *flat* sail; while this is a reasonable first approx., in general there will be some tendency toward "parachuting" or "coning" of the sail, depending on how it is supported. I vaguely recall that the maximum "coning" angle in one heliogyro-type sail I saw discussed was several degrees ... ) >>... seems like you should be able to use a fair amount of the >>orbital thrust to your advantage -- on the part of the orbit heading >>towards the Sun, you essentially try to use what little "outward" >>force you have available. (pedantic question: outward with respect to *what*? the Earth? or the Sun?) >I haven't investigated it in detail myself, but my gut reaction is that >the outward force basically isn't *doing* anything useful. Maneuvering >in a gravity field whose strength is many times the sail thrust, gaining >velocity is much more productive than opposing the field directly... >and the price of that outward force is velocity loss due to the "backward" >component. I *think* I agree with Henry on this. My understanding is that the optimum strategy is to *maximize* the dot-product of the sail's thrust and velocity (w.r.t. the body it's orbiting) vectors at all times, so as to maximize its rate of energy-gain (i.e., *Power* = Thrust.Velocity). Sketch of (possibly falacious) "proof." Recall that the total energy of an orbiting body is inversely proportional to its semi-major axis; a bound orbit has *negative* total energy; and an escape orbit (*infinite* s.m. axis) has *zero* total energy. Therefore, to escape in minimum time, you need to *gain* energy at the maximum rate, i.e. maximize the mechanical power of the sail's thrust. Now, that isn't to say that the above strategy is *realizable*; it might lead to orbits that, say, become more and more eccentric until they intersect the Earth. That's what happens to an "Echo" balloon --- and presumably a sail if you *don't* "tack" --- the orbit "walks" with a fixed s.m. axis and increasing eccentricity in a direction perpendicular to both the light-pressure thrust and its angular momentum, until it hits the Earth (yes, orbital mechanics certainly *is* counterintuitive :-). I once derived (and then lost :-( the optimum sail angle, so I've never gotten around to running a simulation to see what *really* happens ... Gordon D. Pusch ! BITnet: TASCC A&D, Stn. 49a ! AECL, Chalk River Laboratories ! Phone: (613) 584-3311, X-4107 (off.) Chalk River, Ont. K0J 1J0 ! (613) 584-2368 (hm.) Canada ! ------------------------------ Date: Wed, 5 Feb 1992 18:05:49 EST From: KEVIN@A.CFR.CMU.EDU Subject: Solar sails To: space-tech@cs.cmu.edu In regards to the solar sailing: I heard a presentation by the Canadian team a few years ago (the one with a hexagonal set of venetian blinds for sails - very manuverable); the mass for most of the solar sails was in the hundreds of kilos, with the exception of the heliogyro (counterrotating blades, like the spokes of a wagon wheel) which was estimated at 80 kilos due to the low sail area. They would have to start from some medium orbit to keep air drag from overcoming solar thrust. I don't recall what that orbit perigee was, though. The canadian team had a really neat video of what they expected the sailships to look like in loose formation. There was a British one that unfolded in some origami fashion, from a spiral winding around a spindle out to a disk; one that used inflated booms for struts, several with paddles at the extrema of the sails for manuvering, the heliogyro beating along in the middle... great stuff. I hope the reality will occur. An idea I've had sitting in the back of my head for some time: the old magnetic propulsion idea. Use gravity gradiant stabilized wires extending up and down from the probe and pump a current through them to react against the Earths magnetic field. I know that there's a lot of argument over how well this would work, and it's limited in providing only one angle of thrust, but I wonder if this might not be an appropriate "first stage" for a solar sail probe? Use the magnetic pump as something to raise the orbit to where the sail becomes more effective, and you're off. Perhaps, if the magnetic pump is effective enough, use it to raise apogee until you reach escape velocity and only then deploy the sail. Possibly silly - but I thought this up while considering low mass piggyback probes of various kinds (no reaction mass on this one) and still think it might be an interesting possibility. kwr Internet: kr0u+@andrew.cmu.edu ------------------------------ Date: Wed, 5 Feb 92 08:58 PST From: jean@russia.dgi.com (Jean Kim) To: space-tech@cs.cmu.edu Subject: fiberglass hi. I am working for a small aerospace company and we are building a plane and part of its fuselage will be made of fiberglass. I was wondering if anyone out there know whether or not it is possible to get a pre-preg. fiber glass. If it exists, I would really appreciate it if you can Email me. My Email address is jean@dgi.com Thanx in advance! -jyk ------------------------------ From: will@rins.ryukoku.ac.jp Date: Thu, 6 Feb 92 11:57:51 JST To: space-tech@cs.cmu.edu Subject: Re: fiberglass >I was wondering if anyone out there know whether or not it is >possible to get a pre-preg. fiber glass. > I don't know, but I got some stuff from M.C. Gill Corp. and I bet they would know. There address is: 4056 Easy st. El Monte, Calif. 91731 Phone: (818) 443 - 4022 Fax: (818) 350 - 5880 Telx: 67 - 7467 Do me a favor, if you call them up, ask them if they have an email address. Will... ------------------------------ To: space-tech@cs.cmu.edu From: VOLDEN@caelab1.cae.wisc.edu (JEFFREY SCOTT VOLDEN) Date: 5 Feb 92 18:10:56 CST Subject: Metstable Helium Info Request I was recently assigned to give a twenty minute talk on the topic of Metastable Helium. Unfortunately, this topic appears to be so "cutting-edge", I can find little or no information on it. I would greatly appreciate any sources or insights on this topic. Thanks, volden@cae.wisc.edu ------------------------------ Date: Wed, 5 Feb 1992 20:19 EST From: "GORDON D. PUSCH" Subject: Re: Metstable Helium Info Request To: VOLDEN@caelab1.cae.wisc.edu, space-tech@cs.cmu.edu X-VMS-To: IN%"VOLDEN@caelab1.cae.wisc.edu" X-VMS-Cc: SPACE-TECH,PUSCHG There is a section (sec.5) on metastable helium in Bob Forward's Air Force Rocket Propulsion Laboratory Report: "Alternate Propulsion Energy Sources" (AFRPL-TR-83-067 (unclassified)) It clearly says on the cover that the report is to be "distributed to DoD and DoD contractors only," but he still sent me a copy gratis :-). His address *used* to be: Dr. R.L. Forward Forward Unlimited 34 Carriage Square Oxnard, CA 93030 but I think it might be obsolete; I believe he uses a P.O. Box nowadays, since he spends a lot of his time in his castle in Scotland ;-). I've got his business card somewhere at home, so I'll send a correction ASAP. Forward cites a number of references; the two most relevent to your question look (unfortunately) to be: J.S. Zmuidzinas: "Energy storage in solid helium" (JPL TM-33-653) (1973) and J.S. Zmuidzinas: "Electronically excited solid helium" in: D.D. Papaliou: "Frontiers in Propulsion Research" (JPL TM-33-722) (1975) both from JPL (Jet Propulsion Lab, Pasadena, CA 91109). I've never tried writing JPL for tech-reports myself, so I know nothing about procedures and/or costs involved. I suspect there's *somebody* in this NewsGroup who does, though ... ;-) Gordon D. Pusch ! BITnet: TASCC A&D, Stn. 49a ! AECL, Chalk River Laboratories ! Phone: (613) 584-3311, X-4107 (off.) Chalk River, Ont. K0J 1J0 ! (613) 584-2368 (hm.) Canada ! ------------------------------ End of Space-tech Digest #100 *******************