Subject: Space-tech Digest #69 Contents: Nick Szabo Re: Jupiter-powered science Paul Dietz Re: Jupiter-powered science John Stevens-Schlick SSI Lunar Polar Explorer Project Craig Lindley Re: Mars Conveyor Tom Neff Re: Mars Conveyor David Cortesi Re: Mars Conveyor Henry Spencer Re: Mars Conveyor Dominic Herity Re: Mars Conveyor Henry Spencer Re: Mars Conveyor Joe Beckenbach Re: Mars Conveyor Hans Moravec Re: Mars Conveyor Nick Szabo Re: Mars Conveyor Hans Moravec Re: Mars Conveyor Craig Lindley Re: Rocket to the Moon Contest Henry Spencer Re: Rocket to the Moon Contest Phil Fraering Amateur Space Telescope ------------------------------------------------------------ Date: Tue, 3 Jul 90 18:11:41 -0700 From: "Nicholas J. Szabo" To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: Re: Jupiter-powered science dietz@cs.rochester.edu (Paul Dietz) writes: >You don't need to attach the spacecraft to a moon. The >conducting tether can be held more or less aligned with Jupiter >by tides. >Orbits closer to Jupiter are *much* better, especially for viewing >the Jovian cloud tops, because (a) the vehicle is moving faster w.r.t. >the magnetic field, (b) the field is stronger, and (c) the Jovian >atmosphere is much closer. Unfortuneately, our 2,000 kg spacecraft will lose 1/10 of its velocity and fall into Jupiter after drawing 200 kw for only 28 hours: 2,000 kg(3.15e3 m/s)^2 / 200e3 w = 99,000 seconds Stapling ourselves to Metis allows us to do science indefinetely. It also protects against uncertainties in the Jupiter environment. Almost once every equatorial orbit we pass through the 5 million amp, 400,000-volt flux tube between Jupiter and Io. I'm not sure what forces this will put on our cable. Whether on Metis or not we need circuitry to protect from and smooth out the amps. We will be passing through flux tubes in some regions of our orbit; there may be a paucity of electrons in other regions. Metis may be able to serve as an electron reservoir. >Your figures for Metis are faulty. [] >Combining these, you get a voltage of .68 volts/meter, which is >close enough to your number. Thanks for the corrections. That's what I get for jotting quick notes as the librarian is trying to kick me out at closing time. :-) BTW, what reference(s) would you recommend for planetary data such as magnetic moments, names and orbits of all the moons and major asteroids, etc.? Here's a stab at the power cable. It should be deployable both in orbit (for electrodynamic braking) and on the surface of Metis. We use Dupont's high-T(c) superconductor (105K) or something similar, assuming we know how to manufacture it in durable form by the time the spacecraft is built. I am told there should be no problem with getting 1,000 amps/cm^2. We cool with veins of liquid nitrogen (77K), and string loosely inside a tube that shades the wire from most radiation, plasma, small micrometeorites, etc. length = 1,000 meters superconducting cross-section: .50 cm^2 (.4 cm dia) potential = 1,000 meters * .68 volts/m = 680 volts current = .50 cm^2 * (1,000 amps/cm^2) = 500 amps This gives a maximum capacity of 340 kilowatts; anything higher must be protected against by the circuitry. Assuming the density of high-T(c) superconductors is 2.0 g/cm^3 (anybody know the real figure?) the superconductor masses 10^5 cm * .50 cm^2 * .002 kg/cm^3 = 100 kg This figure will double or triple by the time we add the liquid nitrogen veins and shading tube, but is still within my original guess of 800 kg (.4 kg/m) for the cable. Nick Szabo uunet!ibmsupt!szabonj ------------------------------ To: space-tech@CS.CMU.EDU Cc: dietz@cs.rochester.edu Subject: Re: Jupiter-powered science Date: Wed, 04 Jul 90 13:38:08 -0400 From: dietz@cs.rochester.edu Nick Szabo wrote: > Unfortuneately, our 2,000 kg spacecraft will lose 1/10 of its velocity and > fall into Jupiter after drawing 200 kw for only 28 hours: > 2,000 kg(3.15e3 m/s)^2 / 200e3 w = 99,000 seconds That calculation is faulty, Nick. For one thing, the energy dissipated in going from 31.5 km/s to 28.4 km/s is considerably greater than the energy required to go from 0 to 3.15 km/s. Let's calculate the difference in energy (kinetic & potential) betweem a body in circular orbit at Metis (r = 127,960 km, period .295 sidereal earth days) vs. low orbit (r = 72,000 km). The (negative) potential energy of a circular orbit equals the kinetic energy of the satellite (because escape velocity is sqrt(2) times circular velocity). This energy goes as 1/r. At Metis, the kinetic energy of a 2000 kg satellite is .5 * 2000 kg * (3.15e4 m/s)^2 = 9.9e11 joules. The difference in energies between the low orbit and Metis orbit is, therefore, (127,960/72,000 - 1) * 9.9e11 J = 7.7e11 J. At 200 kilowatts, it would take 44 days to dissipate this much energy. > Stapling ourselves to Metis allows us to do science indefinetely. > It also protects against uncertainties in the Jupiter environment. > Almost once every equatorial orbit we pass through the 5 million amp, > 400,000-volt flux tube between Jupiter and Io. I'm not sure what > forces this will put on our cable. But how do you *get* to Metis? If the spacecraft circularizes by firing a rocket at the periapsis of a parabolic orbit, it needs a delta V of 13 km/s. That's not feasible with chemical rockets. It might be feasible, if slow, with a tether deployed in free space. > BTW, what reference(s) would you recommend for planetary data such > as magnetic moments, names and orbits of all the moons and major asteroids, > etc.? I got the numbers I used from the appendix of Baugher's "The Space-Age Solar System" (Wiley, 1988). It is pre-Voyager-Neptune, obviously. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Tue, 3 Jul 90 12:03 PDT From: Games Wizard Subject: SSI Lunar Polar Explorer Project Ground Support System Stuff... To: space-tech@CS.CMU.EDU X-Envelope-to: space-tech@cs.cmu.edu X-VMS-To: IN%"space-tech@cs.cmu.edu" X-VMS-Cc: GAMES I have been working with some of the key people at SSI's Lunar Polar Explorer Ground Support Team for a couple of months now. I have basically volunteered my time and experience as a programmer to work on code that will be run (in Texas) to provide ground support for the probe. I have also come up with a VAX 11/780 and 2 RP06 disk drives as well as a TU77 tape drive for the project. Unfortunately the 11/780 has a bad IO control card ( I personally am not sure exactly which one ), and so it is no "working" at present. The other problem is that this system is in Seattle. So, I am working on getting a VAX 11/750 donated to them as well. I am also trying to locate someone who would be willing to donate a truck ride for this equipment to their computer room in Texas. (Considering that they are non-profit, any partially empty truck going that way could use the trip as a healthy write off for tax purposes.) The reason for posting this is to show that it is possible to make a dent in some of the exciting, low budget, home grown science that is going on in relation to space. The other reason for posting this is that these guys could use a lot more equipment. They really would like to run 2 identical systems in tandem, so that the thruster burn calculations are a little more guarenteed to get done. ( A system crash on a single system with critical calculations could cause a BIG problem.) So... If anyone out there has ANY VAX equipment that they are not using, or can't sell (due to low book value), please think seriously about donating it. 11/750's 11/780's or old microvax II could all provide CPU horsepower for this project... Disk drives, terminals, ethernet hardware, etc... anything that you have laying around that you don't need could be of use. Don't forget that you get to write off the donation at book value rather than market value. If anyone out there knows of trucking that could be made available, please dont hesitate to contact the project. Contact : Either myself ( the project does not have an internet address yet.) or Larry Spratlin or Diane Apoblo at (713) 333 - 2900 Remember : The help YOU give, will make a BIG difference in this project. ------------------------------------------------------------------------------- Trendy footer by: John Stevens-Schlick Internet: GAMES@maven.washington.edu 7720 35'th Ave S.W. Seattle, Wa. 98126 (206) 935 - 4384 ------------------------------------------------------------------------------- My boss dosn't know what I do. ------------------------------ Date: 03 Jul 90 13:18:20 +1000 (Tue) To: space-tech@CS.CMU.EDU Subject: Mars Conveyor From: -------------------------------------------------------------------- Donald.Lindsay@MATHOM.GANDALF.CS.CMU.EDU suggests: >There's an old idea, which I have always called the Mars Conveyor. >It's quite simple: we put a large structure into an orbit that >(approximately) visits both Earth and Mars. Once established, we >leave it that way, and use our delta-v in getting to it/from it. >I could have gone into this idea at greater length. However, before >spending the bandwidth, I'd like to ask: why haven't I heard of this >idea in years? Was there a fatal flaw? The fatal flaw is that intercepting the thing with a velocity low enough to avoid destroying both the interceptor and the conveyor requires going into same orbit as the conveyor. In this case the conveyor is superfluous. Its only real use could be for data store-and-forward for some sort of martian surface or orbital data gathering system. In this case it would be an expensive alternative to direct transmissions, but could be worthwhile for _huge_ quantities of data. - Craig Lindley ------------------------------ From: Tom Neff Date: Tue, 3 Jul 1990 09:51:21 EDT X-Mailer: Mail User's Shell (7.1.1 5/02/90) To: SPACE-TECH Mailing List Subject: Re: Mars Conveyor On Jul 3, 1:18pm, Craig Lindley (who put his name as fifty dashes in the From: line, thus annoying my mailer!) wrote: > Donald.Lindsay@MATHOM.GANDALF.CS.CMU.EDU suggests: > >There's an old idea, which I have always called the Mars Conveyor. ... > > The fatal flaw is that intercepting the thing with a velocity low enough > to avoid destroying both the interceptor and the conveyor requires going > into same orbit as the conveyor. In this case the conveyor is superfluous. As has been pointed out in other postings, the conveyor is NOT superfluous because it can hold the shielding, power supply, living space etc. for MULTIPLE extended missions to Mars. What you send to intercept it need only be a transfer craft sufficient to keep the crew alive for a short trip. Less mass, less duplication, less complication. ------------------------------ Date: Tue, 3 Jul 90 09:03:16 PDT From: David Cortesi To: infmx!pyramid!cs.cmu.edu!space-tech@decwrl.dec.com Subject: Mars conveyor Craig Lindley writes of the Mars Conveyor: >The fatal flaw is that intercepting the thing with a velocity low enough >to avoid destroying both the interceptor and the conveyor requires going >into same orbit as the conveyor. In this case the conveyor is superfluous. >Its only real use could be for data store-and-forward for some sort of >martian surface or orbital data gathering system. You are thinking too small. You are right enough when the only Mars traffic is data: pictures and stingy scrapings of soil. But if there were to be a regular traffic in _people_, the scale of the transit hardware would have to be much larger. To take people to and from Mars in any kind of comfort requires a vessel with the interior volume and amenities of a village (of a south-polar winter colony, for example, but with more room for vegetation). In that case the orbiting mass becomes quite significant, and it would be extremely uneconomical to de-orbit and re-orbit it twice for every round trip. It would be much cheaper to keep the habitat going around and around, and apply delta-V only to the passengers, their luggage, and the consumables they need. But it is rather spooky to try to picture the detailed logistics of boarding the round-trip habitat. As seen from either terminus, it's a case of "here she comes, there she goes." As Craig and others have rightly noted, a shuttle craft that matches speeds with the conveyor is ipso facto in a transfer orbit for the other planet. Because there is always the chance of missing the rendezvous, a man-rated transfer shuttle would have to be capable of matching speeds and then returning to its base without refueling -- otherwise any little failure of docking hardware or approach radar would doom the passengers to a rather nasty death. On the other hand, every second spent in the transfer orbit increases the cost of returning the shuttle -- so unloading might be a rather frantic scramble as embarking and debarking passengers rush to change places and cargo is flung back and forth. In fact a better arrangement would be for a shuttle to mate with the Conveyor craft and stay with it all the way to the other end. That allows plenty of time for loading and unloading -- at the cost of having an expensive shuttle craft spend most of its time idle, riding back and forth between planets. In fact, two of them, since an appropriate transfer shuttle for Mars might be quite a different vehicle from one used at the Earth end of the trip. Accordingly, the Conveyer needs to be supported by at least two Earth-end shuttles and at least two Mars-end shuttles, with one of each at all times attached to the Conveyor itself, dead-heading around the loop before being used for debarkation. These shuttles are not simple vehicles, either. As noted, they must have enough delta-V to match transfer orbit and return without refueling. And they must be as large as possible, since they are the bottleneck through which all Conveyor traffic passes -- the Conveyor's capacity is the capacity of its shuttles, period. And maintenance might be a problem. Consider the duty cycle I've suggested: lift off and match orbits; lock down and coast for many months; then fire up and de-orbit. And hope to goodness that you didn't have a fuel leak during the idle time! -- David Cortesi (cortesi@informix.com) ------------------------------ From: henry@zoo.toronto.edu Date: Tue, 3 Jul 90 14:04:56 EDT To: space-tech@CS.CMU.EDU Subject: missing the Mars conveyor > ... Because there > is always the chance of missing the rendezvous, a man-rated transfer > shuttle would have to be capable of matching speeds and then returning > to its base without refueling -- otherwise any little failure of docking > hardware or approach radar would doom the passengers to a rather > nasty death. Almost certainly it is much cheaper to build redundancy into the rendezvous and docking systems than to provide for an unrefuelled return. You can put an elaborate multiply-redundant radar system on the conveyor itself, which means the shuttle just needs redundant short-range communications (much easier). Docking systems are never life-critical if your passengers have spacesuits. In general, you can finesse around almost anything relatively cheaply if you can assume that the shuttle does end up in about the right orbit. That leaves just major propulsion failures as fatal problems, and it's very difficult to guard against those. The situation is not unprecedented: the Apollo rendezvous operations in lunar orbit amounted to almost exactly the same thing. There too, with a bit of advance planning and some backup equipment, the only real killer was major propulsion failure. > ...In fact a better arrangement would be for a shuttle to mate with the > Conveyor craft and stay with it all the way to the other end. That > allows plenty of time for loading and unloading ... Also significant is that it allows the planetward part of the shuttle's maneuvering to be done mostly by aerobraking. Particularly if aerobraking is available, going "out and back" with a single shuttle is very costly, because the economical "back" window precedes the economical "out" window and you can't hit both with one shuttle. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Tue, 03 Jul 90 17:29:57 BST From: dherity%cs.tcd.ie@VMA.CC.CMU.EDU Subject: Re: Mars Conveyor To: space-tech%cs.cmu.edu@VMA.CC.CMU.EDU I hope we've established that this is a sort of interplanetary ocean liner that doesn't stop for embarkation/debarkation. Now, I can see how you would put such a vehicle between the *orbits* of Earth and Mars, touching each *orbit*, but how could you synchronise it to the motions of both *planets* in their orbits, so that the vehicle is in the right place at the right time to intercept? Either I'm missing a vital point, or somebody else is. ------------------------------ From: henry@zoo.toronto.edu Date: Tue, 3 Jul 90 15:40:42 EDT To: space-tech@CS.CMU.EDU Subject: Re: Mars Conveyor > Now, I can see how you would put such a vehicle between the *orbits* of > Earth and Mars, touching each *orbit*, but how could you synchronise it > to the motions of both *planets* in their orbits... Difficult to do if you've just parked it in orbit, as the orbital periods don't combine very conveniently. But there are various tricks that can be played with gravity assists: you don't *have* to leave it in a single permanent orbit, given that its whole purpose is to make regular planetary encounters anyway. Optimizing this sort of gravitational pingpong gets very complex and I'm not up to date on just what can be done... but the folks who have looked into it think it's promising. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ To: space-tech@CS.CMU.EDU Subject: Re: Mars Conveyor Reply-To: jerbil@csvax.caltech.edu Date: Tue, 03 Jul 90 13:18:42 -0700 From: Joe Beckenbach > Now, I can see how you would put such a vehicle between the *orbits* of > Earth and Mars, touching each *orbit*, but how could you synchronise it > to the motions of both *planets* in their orbits, so that the vehicle is > in the right place at the right time to intercept? By not constraining the orbit to be Hohmann (sp?) between Terra and Mars. If I remember the (vague) details published in an ONMI magazine of a few years back, the revolution time of the orbit is greater than that of both Terra and Mars. Roughly 2/3 of the time in orbit is transit from one to the other, and the other 1/3 of the time is the return transit. I forget whether perihelion was less than 1AU, aphelion was greater than Martian aphelion, or both. Joe Beckenbach --- Joe Beckenbach jerbil@cs.caltech.edu (818) 356-6767 (also:) uunet!cit-vax!jerbil jerbil@csvax.caltech.edu ------------------------------ Date: Tue, 3 Jul 1990 15:21-EDT From: Hans.Moravec@ROVER.RI.CMU.EDU To: space-tech@CS.CMU.EDU Subject: Mars conveyer If it were equipped With a rotating tether the Mars conveyer could catch a shuttle in a circular solar orbit at earth (or even earth orbit). The shuttle could then climb the rotating tether to the hub center, where the passengers ride in comfort, then climb back out to a tip at Mars orbit, where, by correct choice of release instant, the tether tip velocity would drop them into circular orbit at Mars. This amount of delta V can be achieved with existing materials like Kevlar (or the newer Spectra (= high performance polyethelene) that has 30% higher strength/weight). Here's a little paper from 1978 that discusses a similar maneuver, with the same delta V requirement: _____________________________________________________________________ Free Space Skyhooks A non-planetary Kevlar skyhook with tip velocity wrt its center of 1/4 earth escape velocity, which is just enough to catch a Venus-Earth Hohmann and accelerate it to Earth-Mars Hohmann is able to support 1/425 of its mass at each end, building in a safety factor of two. If the skyhook masses 21x10^6 Kg., it can support 50,000 Kg (about the mass of Skylab), at each end. Considering different lengths (mass ratio is unaffected by geometry): Skyhook Rotational Acceleration Area of cable Area of cable radius period ends middle 100 Km 3.74 min 8 g 28 cm^2 1700 cm^2 1000 Km 37 min 0.8 g 2.8 cm^2 170 cm^2 2000 Km 1.25 hrs 0.4 g 1.4 cm^2 84 cm^2 5000 Km 3 hrs 0.16 g 0.56 cm^2 34 cm^2 10,000 Km 6.25 hrs 0.08 g 0.28 cm^2 17 cm^2 20,000 Km 12.5 hrs 0.04 g 0.14 cm^2 8.4 cm^2 The cable cross section as a function of radius is a perfect EXP(-r^2) normal curve. Macsyma was able to integrate it symbolically, to get an expression for the mass ratio. The integral naturally contains the error function. The taper ratio and the mass ratio go up exponentially as the square of the tip velocity (and simply exponentially with the weight/strength ratio). A Hohmann catch/Hohmann boost removes or adds orbital energy to the cable, but does not affect its rotation. The formula for cable cross section: M v^2 EXP(D/T v^2/2 (1-(r/r[e])^2)) Area(r) = ----------------------------------- T r[e] r is distance from cable center r[e] is cable radius (i.e. 1/2 its length) v is tip velocity wrt. center D density of cable material T design tensile strength of cable M mass to be supported at each end this, integrated and multiplied by two and by density, divided by M gives the mass ratio: let dtv2 = D/T v^2/2 Mass Ratio = 2 SQRT(P dtv2) EXP(dtv2) ERF(sqrt(dtv2)) Hans Moravec November, 1978 ------------------------------ Date: Tue, 3 Jul 90 17:25:43 -0700 From: "Nicholas J. Szabo" To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: Re: Mars conveyer uunet!ROVER.RI.CMU.EDU!Hans.Moravec writes: >If the skyhook >masses 21x10^6 Kg., it can support 50,000 Kg (about the mass of Skylab), at >each end. 21x10^6 kilograms in solar orbit requires about 7,000 shuttle/TOS launches, not counting the mass of the 13,998 connecting pieces and some robotic connecting machines. Even using NASA's underestimate of $300 million per shuttle launch, this tether costs $2,100 billion, or 420 times the size of the U.S. trade deficit, or 42,000 times the amount spent to develop the Pegasus launch vehicle. Nick Szabo uunet!ibmsupt!szabonj ------------------------------ Date: Wed, 4 Jul 1990 14:42-EDT From: Hans.Moravec@ROVER.RI.CMU.EDU To: space-tech@CS.CMU.EDU Subject: Re: Mars conveyer Regarding a rotating tether on a Mars conveyer to switch passengers between circular and transfer orbits, Nick Szabo writes: > 21x10^6 kilograms in solar orbit requires about 7,000 shuttle/TOS launches, > not counting the mass of the 13,998 connecting pieces and some robotic > connecting machines. Even using NASA's underestimate of $300 million per > shuttle launch, this tether costs $2,100 billion, or 420 times the size of > the U.S. trade deficit, or 42,000 times the amount spent to develop the > Pegasus launch vehicle. > > .Nick Szabo > uunet!ibmsupt!szabonj But these numbers are predicated on a very large (50,000 Kg - Skylab mass) transfer payload supported by a conservative (2x safety factor) Kevlar tether. If instead of Kevlar we use Spectra, and reduce the safety factor to the 30% edge that Spectra has over Kevlar, the design strength/weight ratio of the tether is doubled. This reduces the taper ratio, and approximately with it the mass ratio, to its square root. Instead of 425 the mass ratio drops to about 25. The transfer capsule could be a mere shell with short term life support delivered by a transfer vehicle (say the shuttle at the earth end). The transfer vehicle mauevers into an orbit whose apogee is tangent to the tether tip trajectory, but does not attach itself to the tip. Only the transfer capsule (with passengers) is attached and puts a (centrifugal) load on the cable. Perhaps the capsule masses 1000 Kg and carries a few passengers. After one capsule has worked its way from the tip to near the hub, the tether is able to receive another capsule. Many passengers could be thus ferried a few at a time in the month or so that the conveyer cable tips can be reached by a modest delta-v. With a mass ratio of 25 and a payload of 1000 Kg, the tether masses only 25,000 Kg. Even using your pessimistic estimates about the cost of future large scale space construction (i.e. everything ferried from earth at present-day shuttle costs, that keep 50,000 employed to launch once a month), the cost is only $2.5 billion. This for a highly reusable system that saves lots of delta v, especially at Mars where it is expensive. As stronger materials are invented, the cost could drop farther (chemical bond strengths allow at least another factor of 10 improvement in strength/weight, which would lower the mass ratio from 25 to about 1.5). -- Hans Moravec ------------------------------ Date: 04 Jul 90 12:41:04 +1000 (Wed) To: space-tech@CS.CMU.EDU Subject: Rocket to the Moon Contest From: lindley@ditsyda.syd.dit.csiro.au Lou Adornato suggests: >Regarding the idea of a race: I suggest that it be a race from LEO to the moon. >All contestants get boosted at the same time, in what and at whose expense we >leave as an exercise for the reader (for now). ... etc. A natural extension to this idea is for all 'contestants' to collaborate in the construction of a serious amateur lunar probe. With so much energy and enthusiasm available, it seems like a shame not to produce something more worthwhile than a bunch of little craters. AMSAT already recognise that it would be a small step from one of their existing designs piggybacked into GTO. They also have a global network of control stations. Why not a collaborative project with AMSAT to orbit an amateur probe with a simple camera system? This is assuming, of course, that there is some reason for doing this in addition to the Space Studies Institute's project. The simplistic 'hit the moon' contest seems analogous to painting "X was here" graffiti on a rock. Craig Lindley CSIRO DIT oz ------------------------------ From: henry@zoo.toronto.edu Date: Wed, 4 Jul 90 13:55:09 EDT To: space-tech@CS.CMU.EDU Cc: space-project@CS.CMU.EDU Subject: Re: Rocket to the Moon Contest (This is from space-tech, but is obviously relevant to space-project...) >The simplistic 'hit the moon' contest seems analogous to painting "X was here" >graffiti on a rock. I'm afraid I have to agree, to some extent. Spaceflight is not in such good shape that we can afford to invest major effort with no useful return. Optimistic IMAX titles notwithstanding, the Dream is not Alive -- it is in hospital in critical condition, with prognosis uncertain. My conclusion over the last couple of years has been that space enthusiasts really ought to be observing one basic principle: Don't Play With Toys -- Do Something Useful. As a case in point, I tried to convince the Canadian Space Society team in the solar-sail race to try an end run around the rules, forgetting the rather artificial goal of the race (race to Mars) and doing something ambitious and useful instead (photograph the unknown side of Mercury). Alas, they didn't go for it. > A natural extension to this idea is for all 'contestants' to collaborate > in the construction of a serious amateur lunar probe. ... Here is where Craig and I part company. :-) Satellite building is an interesting thing to do, but it's not likely to appeal to model rocketry people, and the collaborative aspect automatically removes a good bit of the energy and enthusiasm brought out by competition. What I would suggest is a slight variation. Instead of racing to the Moon, race to low Earth orbit, i.e. to put up the first all-amateur satellite -- amateur launch as well as amateur construction. It need not be large. I'd suggest a target of 1 kg. The significance of that is that Freeman Dyson has seriously suggested that payloads of that size would be scientifically useful. I.e., we are talking about a launch system that would have real applications, not just a toy. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Wed, 4 Jul 90 13:23:53 -0500 From: Fraering Philip To: space-tech@CS.CMU.EDU Subject: Amateur Space Telescope Was anyone on this list a participant in the Amateur Space Telescope project? Thanks in advance, Phil ------------------------------ End of Space-tech Digest #69 *******************