Date: Sat, 24 Sep 1988 18:21-EDT From: Marc.Ringuette@DAISY.LEARNING.CS.CMU.EDU To: mnr Subject: Space-tech Digest #8 [ Administrative note: My machine has been cut off from the net for a couple of days. The first four messages of this digest probably made it to the main space-tech list; the others almost certainly didn't. I'm therefore sending this to everybody. -- Marc ] Contents: Kevin Ryan Small Satellites Jim Meritt Re: Small Satellites Steve Jensen Re: Small Satellites Roger Arnold sad realities Ollie Eisman Results of Satellite Idea Survey Roger Arnold performance of small LVs ------------------------------------------------------------ Date: Wed, 21 Sep 88 17:55 EDT From: KEVIN@A.CFR.CMU.EDU Subject: Small Satellites To: space-tech@CS.CMU.EDU X-VMS-To: CMCCVB::IN%"space-tech@cs.cmu.edu" The discussion on space-tech concerning solar sails has convinced me that it will probably take too much in the way of resources for a small AMSAT/OSCAR type project. For one thing, you have to get to MEO (~8000 miles) just to get started! However: what about magnetic field drive? This is where you deploy two long wires from your satellite, allowing gravity gradient to align them pointing towards the earth. You are cutting the earth's magnetic field by orbiting through it. Run a current through the wires, and you are acting as the rotor of a motor, allowing you to add to or subract from your orbital velocity. Details in a David Brin story (_Lungfish_?), as well as several NASA articles, etc. Thus a small craft with a couple of long wires and some solar cells would be able to pump itself out of LEO. Magnetic field of Earth into page. <- Earth ^ orbital direction <<< induced current +--------------------O---------------------+ weight ^ ^ wire ^^^^^ Thrust Put a load on the wire and the craft slows, run power the other direction and the craft accelerates. Charge disappates to/from the ends of the wires. Cheap, wires are _easily_ deployed, store compactly, etc. Time your pumping properly, and you could easily kick out towards the Moon, Jupiter, Venus, etc. Thrust dependent only on the power you can throw through the wires, the local magnetic field strength, and how stiff your wires are. Probably a good idea to put some weights on the ends of the wires to aid the gravity gradient and keep the wires from wrapping around the satellite when thrusting. Note that this only allows thrust in +/- the direction of travel (unless I'm missing something), so it does have it's limitations. Some questions I have for the more knowledgeble: - What kind of power is required for this scheme? - What are the magnetic field strength distributions for the Earth? For the Moon (in case you want to go there)? - How does the earth's magnetic field drop off with distance? - Anyone know of any references for this sort of thing? Kevin Ryan ................................................................................ internet kr0u@andrew.cmu.edu / bitnet kevin%cmcfra@cmccvb.bitnet ____ _/ decnet {cu20b, nyu20, or vassar}::cmcfra::kevin / /| 0\ phonenet 412-268-3461 or 412-371-3681 /___/-^---[ US mail 7235 Penn #4B, Pgh, PA 15208 . . . . _/ | \_ ................................................................................ ------------------------------ Date: Wed, 21 Sep 88 21:56:09 EDT From: jwm@stdc.jhuapl.edu (Jim Meritt) To: KEVIN@a.cfr.cmu.edu, space-tech@cs.cmu.edu Subject: Re: Small Satellites Ref the EM drive - don't remember a whole lot, but do remember that this is used for stabilization / maneuvering for some satellites. So workability data is out there somewhere.... ------------------------------ Date: Thu, 22 Sep 88 10:36:38 -0400 (EDT) From: Steven Kent Jensen To: space-tech@cs.cmu.edu Subject: Re: Small Satellites In response to Kevin's message on magnetic drives for small satellites. > - What are the magnetic field strength distributions for the Earth? > For the Moon (in case you want to go there)? Sorry, but the moon has no magnetic field. It has cooled enough that it no longer has molten core necessary to produce a magnetic field. ------------------------------ From: telesoft!roger@ucsd.edu (Roger Arnold @prodigal) Date: Wed, 21 Sep 88 21:55:34 PDT To: space-tech@cs.cmu.edu Subject: sad realities I feel grouchy today, think I'll spread a little cold water around. Solar sails are nice, for high delta vee solar system missions. But forget about trying to deploy one from a GAS or other LEO piggyback launch. In LEO, drag exceeds thrust. And even if you got high enough for thrust to exceed drag, tidal forces trying to align the sail with the gravity gradient will swamp any counterforce derived from solar radiation pressure. It will be nigh impossible to control a sail of any useful size. The prospect is marginal even for a sail deployed in GEO. Earth based electromagnetic launchers are nice, too, but any hopes of building one are dependent on a government commitment to do something very major in space--SDI deployment, a permanently staffed lunar base. A manned Mars mission might or might not be enough to justify it. It certainly would not be if today's NASA were in charge. I just don't see much prospect for any these, given current political realities in this country. There is an enormous gap between what launch costs are currently, and what they could be with the right launch vehicles. That gap fuels a lot of interest in commercial launch vehicles, but the sad reality is that the commercial launch market is not big enough to justify what it would take to develop anything much better than what we have. I don't put much stock in the NASP, either, but there is one potential route to cheaper space transportation that looks credible. It's not the way I would like to see it go, but the military is developing an interest in intercontinental missiles with precision guided, non- nuclear warheads. The OSC/Hercules Pegasus launch vehicle may be intended for that market, but at $10 million per vehicle, it limits the scope of what the generals can afford to shoot at. To get the cost down to the point that we could consider a non-nuclear defense of Europe from bases in the US, what we'd need would be a totally new type of "bomber". An aircraft that could carry half a dozen Pegasus upper stages (or equivalent) for release at mach 7 and 200,000 feet. It would effectively replace the B-52 carrier and the Pegasus first stage. It would also be the reusable flyback booster that we've needed for more than twenty years. ------------------------------ Date: Fri, 23 Sep 88 10:59:51 MDT From: SPACE EXPLORATION To: space-tech@cs.cmu.edu Subject: Results of Satellite Idea Survey Here are the responses I received from the Satellite Idea Survey. Sorry about the Sept. 21 deadline... I should have allowed more time for everyone to get the mail and answer. [ and yes, there were two questions marked as "2)". I guess I should learn to count!] Scores: Solar sail: 4 For 0 Against (Many other suggestions) Orbit? : 2 LEO 1 Moon 2 Asteroids 3 Beyond Oscar? : 2 Yes 3 No 1 Not sure Launch Vehicle?: 2 Ariane 0 Shuttle 1 Balloon 5 Anything! ============================================================================ >From KEVIN@a.cfr.cmu.edu Tue Sep 20 12:10:24 1988 1) What experiments would you like to see on board? (be realistic!) - Solar sail! It's about time we had a real navigable probe out there! Take it for a tour, and get some practical experience with how to use a sail properly. I'll admit that this is the major thing I would love to see. - Multispectral CCD imager (multiple filters). Get some pictures! Doesn't have to be too expensive, either. - Particle and magnetic detectors akin to those on the Pioneers. If this thing lasts a while and gets flown around the solar system, I'm certain that people interested in the solar particle enviornment will be interested in these results. - If you fly it past an asteroid or do lunar surveying, a spectrometer would be almost indispensible. 2) What type of orbit would you like to see the satellite in? - Fly it around the earth-moon system for a while, then take it out to an asteroid! Beat NASA and the USSR at the same time! 2) Do you think the satellite should be an OSCAR (Orbiting Satellite Carrying Amateur Radio)? - Not if it has a solar sail. No point in the OSCAR idea unless you're putting it into a stable earth orbit. 3) How do you think we should get the satellite in orbit? (Ariane, Shuttle, high altitude balloon, etc) - Hercules/OSC should be operational in ~1 year; AMROC in ~2. They will be OK, but I suspect will not have much 'piggyback' space. I would suggest Ariane. The Shuttle is about as likely as winning the state lottery. - Perhaps the USSR would like some publicity? I can't see how this thing would be a problem with technology transfer... 4) Addtional comments/suggestions: - If carrying a solar sail (SS), there will be times when attenna aim is difficult, as the SS will block the path. If you want a general purpose probe, perhaps two SS's, with the probe between so that it can aim anywhere and still keep the sails oriented to the sun? - Check the Pioneer missions for low-cost experiments. Also check the Mars Mariner (sp?) probes, which used sunlight for attitude control. - Should check on long-life batteries. If this spends 3-4 years flying around the system, it will end up in shadow occasionally. It would be embarrassing to lose the mission because the Evereadys weren't. This sounds like FUN! ------------------------------------------------------------------------------- Kevin Ryan ................................................................................ internet kr0u@andrew.cmu.edu / bitnet kevin%cmcfra@cmccvb.bitnet ____ _/ decnet {cu20b, nyu20, or vassar}::cmcfra::kevin / /| 0\ phonenet 412-268-3461 or 412-371-3681 /___/-^---[ US mail 7235 Penn #4B, Pgh, PA 15208 . . . . _/ | \_ ................................................................................ ================================================================================ >From purtill@bourbaki.mit.edu Wed Sep 21 16:33:46 1988 I only got this today, Sept 21; You probably ought to allow more time for responses. As it is, this is rather off of the top of my head. > 1) What experiments would you like to see on board? (be realistic!) If this is going to be doable, I think we should probably have only one or two things. One of them should be some sort of inovative propultion system like a solar sail or an ion drive. What we with it (the mission profile, if you like) will probably suggest another, see below. > 2) What type of orbit would you like to see the satellite in? If we can manage either asteroid fly-by or impact, I think that would be best. (I'm thinking in terms of an asteroid that passes near earth, not going out to the asteroid belt, as communication would probably become rather difficult). Even if NASA or someone beats us to it, there are lots of asteroids. If it's fly-by, we should get at least one picture of some sort. If it's impact, we'd want to find out some piece of information about the asteroid, such as composition. I'd prefer fly-by. If we want to get really tricky, we could a one piece fly-by and one impact, or try and soft-land, but I think both of those would be awefully hard. Another possibility is to investigate the environment at the L4 or L5 points. We'd want to measure dust and look around for what largish objects (if any) are there. Another possibility is to just stay in earth orbit and demonstrate our propultion device. That would probably be quite hard as is. > 2[.5]) Do you think the satellite should be an OSCAR (Orbiting Satellite Carrying Amateur Radio)? I'm not sure exactly what that means, but I do have a question for those who know about OSCAR sats. Can we use them as an equivalent to NASA's TRDS network to keep in contact with our satellite? Another question: how much did it cost to build the OSCARs? Where did they get the money, etc. 3) How do you think we should get the satellite in orbit? (Ariane, Shuttle, high altitude balloon, etc) Find someone to do it for us free. I don't think there's any other real choice. This means we'll almost certainly start in LEO, which is why I think a propulsion demonstration is something we need. 4) Add[i]tional comments/suggestions: Even if we only get a paper design, I think designing such a satellite (or several such satellites) would be a good idea. ^.-.^ Mark Purtill purtill@math.mit.edu ((")) Dept. of Math, MIT 2-229, Cambridge, MA 02139 ======================================================================== >From klaes%mtwain.DEC@decwrl.dec.com Wed Sep 21 12:24:13 1988 1) What experiments would you like to see on board? (be realistic!) Ones involving the ability to explore another planet, moon, or planetoid, such as a small "spike" probe, which would serve as a simple monitor station on the celestial body's surface, or maybe even one on a balloon if a planet with an atmosphere is chosen. A comet might be difficult to explore with this type of vehicle, but I would not rule it out. Perhaps the probe could be made to orbit the body, or even "just" probe the lunar farside? A camera on these missions is a definite must. 2) What type of orbit would you like to see the satellite in? An interplanetary orbit, perhaps to one of the nearby planetoids as an earlier poster suggested, perhaps even one of the terrestrial planets and/or moons. Would a Jovian mission be too far out, literally? 2) Do you think the satellite should be an OSCAR (Orbiting Satellite Carrying Amateur Radio)? No, not because I have anything against such satellites, but that the plan should be more abitious and attempt to explore regions seldom touched before. 3) How do you think we should get the satellite in orbit? (Ariane, Shuttle, high altitude balloon, etc) I would normally say use an official space agency, but the price tag may be far too much. A smaller reliable "private" launch company may be in order, though I have seen little activity from them lately. If nothing else, perhaps China, Japan, India, or even the Soviets could be approached (and now it looks like Isreal is in the game as well). As for the Shuttle, it looks like you'd have to wait a LONG time before they get through all their backorder launches. 4) Additional comments/suggestions: I am emphasizing planetary missions for two major reasons: Because the U.S. has done so little in this area for so long now (discounting VOYAGER), and such an ambitious mission would attract the attention of those organizations which could further help fund and assist on such future space endeavours. I would be glad to help in any way that I can. =========================================================================== >From @%%cornellc.ccs.cornell.edu:GILL@QUCDNAST.BITNET Wed Sep 21 12:29:51 1988 1) What experiments would you like to see on board? (be realistic!) There are several types of things that I would like to see on these small sattelites. In fact, I feel that the project should consider sending up about 10 of these, with various experiments and targets, all on the same launcher (a MIRV idea). Here are a couple of ideas: a) Have one satellite pass repeatedly through the highest intensity regions of the Van Allen belts to test various radiation proof chips. Something like this could have useful commercial applications as well (maybe even support). Of course, this would require a different type of communication system to relay the results of any faults, as well as a chip-testing facility. b) A simple variable exposure camera, with downlink. Send this one on a trip into the asteroid belt, with a possible landing/encounters with several asteroids. If this is possible, then a simple comet encounter should also not be too difficult a maneuver. Harden the sattelite and keep it simple - maybe we can get some new pictures from somewhere where NASA has never gone before (like the surface of a comet). c) Play around with solar sails. This sattelite would be doing nothing but moving back and forth between Mars and Venus, and would be practise runs of more serious solar-propelled craft. Also a good exercise in orbital mechanics, and tacking. This may be a time-consuming project, but potentially useful. d) This may be a little bit silly and unrealistic, but how about having a cosmic, maneuverable garbage can? According to an August or September Science, there are over 6000 bits of orbitting junk over 10 cm in size. Try to see how realistic it would be to catch or deorbit some of this stuff, just to see how feasible it is. (I have the feeling aiming our trashcan for a 10cm object is in the SDI range of jobs, but what do I know. The idea is important, even if it is impossible.) 2) What type of orbit would you like to see the satellite in? A LEO, with maneuvering to higher orbits using new ideas - such as tossed around on spacetech or SPACE Diegst these last few weeks - just to find out if they can work. As you can see, I like the idea of actually going somewhere with these little sattelites. 3) Do you think the satellite should be an OSCAR (Orbiting Satellite Carrying Amateur Radio)? If it can be obtained and controlled cheaply. At least with this type of sattelite, the design stage is already passed, and useful science can be implemented much quicker. Of course, for those who whish to design sattelites, the design stage is half the fun. Just choose the system that will be the cheapest, and so that the controlling group will be the only one to send commands to it. 4) How do you think we should get the satellite in orbit? (Ariane, Shuttle, high altitude balloon, etc) Whatever is the cheapest and is availlable. If it is possible, maybe they can piggyback on other experiments for a nominal fee. 5) Addtional comments/suggestions: It would be useful if control of these sattelites, or at least downlink reception, could be accomodated at many locations around the globe, with equipment that a small university and some dedicated grads could build/run. This way, any information could end up public domain, because having it in the grubby hands of the government or corporations is pretty scummy. A little off topic, but.... I still think the best thing to do is to get Voyager III out of storage and launch it towards Pluto. Perhaps someone with the expertise can work out the best launch window for such an exercise, and push NASA with some adverse publicity, especially next summer when the Neptune photos start coming in. ------------------------------------------------------------------------------- If some of this stuff is not well thought out, I plead lack of time. I got the message this morning (the 21st), and decided to send it off right away so I could send in my two cents worth, even if that's all it is worth. :-) -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Arnold Gill | If you don't complain to those who | Queen's University at Kingston | implemented the problem, you have | gill @ qucdnast.bitnet | no right to complain at all ! | -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- ========================================================================= >From mcvax!nada.kth.se!d85-per@uunet.uu.net Wed Sep 21 14:16:23 1988 Hello Ollie, Nice seeing you in this group. Though I didn't really believe that you would miss it for the world. I'll answer the question a bit thin because I posted a letter to space-tech about the same subject. Read it. It was mostly comments on the control/computer system. 1) What experiments would you like to see on board? (be realistic!) Some video would be nice. A simple thing with a CCD, A processor and some 8Mbytes of ram can be useful. I need the ram to do image processing etc. Having a camera onboard, especially a cheap one like the ones we can build and afford, will affect the attitude control system, it will have to be better, remember that Voyager can take very good pictures by altering the attitude of the craft toward the motive. The exposure time is long. (Sorry about the English.) Radar is nice, especially if we opt for no orbit at all but for free flying. Navigation in asteroid belt. 2) What type of orbit would you like to see the satellite in? We limit ourself to an orbit!?! 2) Do you think the satellite should be an OSCAR (Orbiting Satellite Carrying Amateur Radio)? No! 3) How do you think we should get the satellite in orbit? (Ariane, Shuttle, high altitude balloon, etc) Lets construct a reasonable sized satellite and then piggy-back it on wathever launch facility that comes along. 4) Additional comments/suggestions: Read my posting. I don't think we should limit ourselves to what has already been done by NASA, or the Soviets for that matter. Even if the craft doesn't work very good I think it will be a lot of fun just "getting the bitch on the road". I suggest a freeflying, solarsail driven, craft. /Per Hammarlund ====================================================================== >From joe@csvax.caltech.edu Wed Sep 21 11:55:55 1988 >1) What experiments would you like to see on board? (be realistic!) Suggestions have been kicking around for a lunar-polar gamma-ray "prospector" to measure the amount of hydrogen available on Luna. This sounds like a really good idea, especially since several could be sent if things were cheap enough. Heck, if buying in bulk is a possibility, let's fly a fleet of prospectors in various bands of the EM spectrum to Luna and Earth-crossing asteroids. If you're talking solely about Earth-orbit satellites only [sigh], go with a satellite to test out ideas for solar sails; eg can it aid aerobraking without breaking, can it work at all, but we need numbers! Other possibilities include university network linking satellites, a satellite for use in precision measurement of gravitational variation in the Earth, and [once you can pump up enough] to visit L4 or L5 and see what sort of environment is waiting there. Or, to be really spectacular, get enough deltaV to send a satellite racing around in Earth's orbit RETROGRADE. In one month you see the Earth's trailing Trojan point, in three you test to see if Vulcan exists, five gets you the leading Trojan point, and six a spectacular meteor shower. :-) >2) What type of orbit would you like to see the satellite in? Damn near anything, as long as it fits the mission. An aerobrake experiment satellite might want to explore some of the highly eccentrics that Paul Dietz has been talking about with Marc Ringuette. [dietz@cs.rochester.edu, Marc.Ringuette@daisy.learning.CS.CMU.EDU] >3) How do you think we should get the satellite in orbit? (Ariane, Shuttle, > high altitude balloon, etc) Any way possible. Balloon is best, especially once we get the hang of it, since as you do more, you learn more. If we can bring the balloon back intact and with most of the gases still there, that can help keep costs down. >4) Addtional comments/suggestions: Um, yeah. Do you know any really good books on orbital mechanics and on computation thereof? I'm thinking of doing an orbital/interplanetary navigator simulation for some hypercubes [parallel-processing machines]. I'd love to get some hard figures on the near-optimal orbits leading to various interesting points in near space, such as L4, L5, Luna, some of the closer [and further] asteriods, good solar orbits for relay satellites, and so on. Live long and prosper, and all that jazz. Joe Beckenbach joe@cit-vax.caltech.edu Apprentice System Mangler for Unix and cubes ======================================================================== >From burdick%hpindl1@sde.hp.com Wed Sep 21 12:13:28 1988 > 1) What experiments would you like to see on board? (be realistic!) A small-scale solar sail project. By this I don't mean that we should try to maneuver it anywhere in particular, but just put up a small package that we can monitor. Put in controls for manipulating the sail and sensors to see if the sail did what we thought it should. > 2) What type of orbit would you like to see the satellite in? Whatever is easiest. Probably low Earth orbit. > 2) Do you think the satellite should be an OSCAR (Orbiting Satellite > Carrying Amateur Radio)? I think we should definitely use what amounts to an OSCAR with the solar sail changes. It will not need to carry the store-and-forward equipment, however. > 3) How do you think we should get the satellite in orbit? (Ariane, Shuttle, > high altitude balloon, etc) We should probably use the same path already proven for the OSCAR satellites. That is, use the Ariane launcher. > 4) Addtional comments/suggestions: If we try to duplicate all of the effort and thought that went into getting the OSCAR and other amateur satellites up there, our efforts would be misguided. It is best to get what we can up there and then worry about grandiose ideas, which is why I suggest not making too many deviations from what others have already put up. -matt -- Matt Burdick burdick%hpda@hplabs.hp.com ============================================================================= Thanks for the replies... I hope this discussion continues! Ollie SEDS-UNM Satellite Tracking Station -- _______________________ seds@ariel.unm.edu ____________________________ SEDS-UNM : Students for the Exploration and Development of Space Box 92 Student Union, University of New Mexico, Albuquerque, NM 87106 (505) 272-8258 ------------------------------ From: telesoft!roger@ucsd.edu (Roger Arnold @prodigal) Date: Fri, 23 Sep 88 17:29:18 PDT To: space-tech@cs.cmu.edu Subject: performance of small LVs Perhaps someone in this group can shed some light on an issue that I've been thinking about, in connection with small commercial launch vehicles. Most of the analysis I've done on scaling suggests that for launch vehicles, smaller should be better. The obvious exception is that if there are large fixed costs per launch that are relatively independent of launch vehicle size, and those are a major factor in overall launch costs, then you want a large vehicle, in order to get the most out of each launch. But in terms of vehicle cost and performance, smaller vehicles should be favored. One particular area that I'm puzzled about is turbopumps. It looks to me like there's a square-cube relationship working in favor of small turbopumps. Cut the linear dimensions in half, and rotational speed doubles in order to deliver the same pressure differential. Capacity, proportional to the cross sectional area of inlet and passages, is cut to one fourth, but the mass is cut to one eigth. The power per pound should be doubled. Yet this is not reflected in practice, where large pumps seem to be favored. One suggestion I've seen is that small pumps are inefficient, because of viscous drag in the pumped fluid. That argument doesn't seem to hold water (uh, pardon the expression). With the same flow velocity through passages of half the linear dimensions, the laminar sheer is, indeed, doubled. However, the length of the passage is only half as great, so the total pressure loss from viscous drag is the same. As to non-laminar flow, what I know of the theory of fluid dynamics and Reynolds numbers suggests that the smaller the scale, the easier it is to avoid turbulent flow. That leaves me with the old "minimum guage" mumbo jumbo--the assertion that "manufacturability considerations" make it infeasible to scale below a certain point. I.e., a small turbopump won't show the power to mass ratio that theoretical analysis would suggest, because other considerations will force its parts to be much heavier than they theoretically need to be. If minimum gauge considerations are what keep small turbopumps from meeting theoretical performance capabilities, then there should be ways to address the problem. A square/cube law is a pretty powerful thing to have working for you, and you could operate well below the theoretical limits and still better the performance of larger pumps. My idea is that a properly designed production line could turn out large numbers of cheap, high performance pumps for use in small, liquid fueled, expendable launch vehicles. Is there anyone in the group who really knows something about this? Anyone who sees a flaw in my analysis? Anyone who can suggest a good reference on minimum gauge considerations? Thanks. - Roger Arnold ------------------------------ End of space-tech Digest #8 *******************