Date: Fri, 2 Mar 1990 10:56-EST From: space-tech-request@cs.cmu.edu To: "~/st/lists/stdigest" Subject: Space-tech Digest #51 Contents: DowJones Space Exploration Faces Astronomical Costs Jean Kim Re: Space Exploration Faces Astronomical Costs John Roberts changing the subject? [ keep space-tech technical ] Ollie Eisman Re: changing the subject? Henry Spencer Re: changing the subject? Brian McCarty CQ Moon Ollie Eisman Re: CQ Moon Edmund Hack Re: CQ Moon Edward Wright Re: CQ Moon John Roberts Re: CQ Moon Paul Bame Re: CQ Moon Paul Dietz Re: CQ Moon Rich Schroeppel Lunar-synchronous satellite Bill Davidsen reflector satellites (CQ moon) John Sahr Re: reflector satellites (CQ moon) Mike Wexler Re: CQ Moon Mike Wexler Re: CQ Moon Mike Wexler Dropping a cable on the moon Lou Adornato Re: Dropping a cable on the moon ------------------------------------------------------------ From: DowJones@ANDREW.CMU.EDU To: bb+dow-jones@ANDREW.CMU.EDU Subject: Space Exploration Faces Astronomical Costs Date: Tue, 27 Feb 90 09:37:20 -0500 (EST) Sender: David Anderson WASHINGTON -- The usually sober Office of Technology Assessment said the U.S. should investigate launching tiny spaceships that use ice for fuel. A laser would pulverize a chunk of ice at the ship's core, an OTA report said, providing enough thrust to push the spaceship into orbit. "We shouldn't assume business as usual in satellite design," said Ray Williamson, the OTA manager who oversaw the report. The just-released report by the OTA, a research arm of Congress, underscores how difficult it is to reduce the cost of space exploration. Military and scientific satellites cost hundreds of millions of dollars each, as do the rockets they ride into space. A single spy satellite can cost $750 million -- more than the Central Intelligence Agency spends on covert activities annually. A proposed National Aeronautics and Space Administration satellite to study Earth will cost $5 billion. The OTA looked at ways to cut costs. Making satellites simpler and heavier could help a little, the agency said, because satellite builders wouldn't need to use such expensive, sophisticated parts. But to realize any savings, the U.S. would also have to build bigger, simpler rockets -- so-called big dumb boosters -- and it isn't clear those rockets would cost less than current models. Making satellites smaller could also help. Single satellites now can weigh 10 tons or more. Slashing the size of a satellite to a few hundred pounds and launching a bunch of them could save money overall, Williamson said. The Pentagon now is exploring that approach. Next month, Orbital Sciences Corp., a privately held Fairfax, Va., rocket company, is scheduled to launch its first Pegasus rocket, which will fly from the wing of a B-52 airplane into space. The first Pegasus will launch a 160-pound military communications satellite. The second launch, now scheduled for June, will launch seven 50-pound communications satellites the size of car tires. Battlefield commanders will experiment with these satellites for tactical communications in war games during troop exercises. But the biggest potential gain, and certainly the biggest risk, comes in a new class of satellites the OTA calls microspacecraft. Micros would generally weigh less than 25 pounds and be launched by the dozens, maybe by the hundreds. The agency suggests using ground-based rail guns to fire them into orbit, artillery-style, or lasers dug into mountains to propel them by vaporizing ice. A lot of the work on this technology has been conducted by the Strategic Defense Initiative Office. Citing SDI estimates, the OTA said it would cost about $550 million, over six years, to build a laser powerful enough to launch 44-pound satellites into orbit. This laser could launch 100 micros into orbit a day, SDI estimated, at a cost of $200 per pound. That's about 5% the cost of current launchers, but SDI's cost estimates have sometimes seemed tipsy. ------------------------------ Date: Tue, 27 Feb 90 16:45:25 PST From: Jean Kim To: space-tech@CS.CMU.EDU Subject: Re: Space Exploration Faces Astronomical Costs >the U.S. should investigate launching tiny spaceships that use ice for >fuel. A laser would pulverize a chunk of ice at the ship's core, an OTA >report said, providing enough thrust to push the spaceship into orbit. Um . . . several nitpicking. 1) Pulverize?? If this is what they used to call LSD Propulsion, i think the word is more like "detonation." Laser Simulated (?) Detonated Propulsion. (I am not sure about the acronym) 2) at the ship's core?? I thought the SDI people were using this technology to control the attitudes of the satellites. The idea is that the laser will heat the ice "shields" placed on the outside of the spacecraft so fast that H2O will go from solid ice to plasma state in microseconds, thus producing impulse or "kick" in the right direction. Of course, the laser frequency will be in the mega Hertz so that all one would feel is just steady acceleration. I thought it was still in theory and research state... anyone have more information?? >any savings, the U.S. would also have to build bigger, simpler rockets >-- so-called big dumb boosters -- Whatever happened to Atlas? about a year ago, someone(a professor) told me that they were still being manufactured and that they were really cheap (like in the hundreds of thousands, not millions, for each) which didn't sound quite right but ... >but SDI's cost estimates have sometimes seemed tipsy. *heh heh* Too much use of LSD "propulsions", maybe? >;-> -jean ------------------------------ Date: Tue, 27 Feb 90 22:00:35 EST From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. To: space-tech@CS.CMU.EDU Subject: changing the subject? In the beginning, there was the net.space/SPACE Digest mailing list. It had a fair amount of technical content, but also a lot of other stuff. Then, Marc created space-tech, for those who wanted to concentrate on the purely technical aspects of space exploration/exploitation. In recent weeks, it seems to me that the subject area of space-tech has expanded considerably, to include economics, politics, and discussion of organizations and their policies, to the extent that technical issues now make up a fairly small percentage of the total. I would not wish to imply that this is inherently bad, however there is already another list in which these other issues are discussed in great detail, and I believe that anybody who can connect to space-tech can also connect to net.space/SPACE Digest. It seems to me that it would be preferable to try to stick to the original topic of this list, and those who wish to discuss the other topics can sign onto the other list. Any comments? John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Tue, 27 Feb 90 23:38:25 -0700 From: SEDS-UNM To: roberts@cmr.ncsl.nist.gov, space-tech@CS.CMU.EDU Subject: Re: changing the subject? Yes, let's keep it technical, folks. Ad LEO! Ollie N6LTJ ------------------------------ From: henry@zoo.TORONTO.EDU Date: Thu, 1 Mar 90 23:51:10 EST To: space-tech@CS.CMU.EDU Subject: Re: changing the subject? >... I believe that anybody who can connect to >space-tech can also connect to net.space/SPACE Digest. It seems to me that >it would be preferable to try to stick to the original topic of this list, >and those who wish to discuss the other topics can sign onto the other list. Even though I've been one of the prominent offenders :-), I am inclined to agree. Space-tech should be technical, preferably with numbers; there is no need to duplicate sci.space/SpaceDigest. Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: Wed, 28 Feb 90 08:04 CST From: "Brian P. McCarty (N9IWP)" Subject: CQ Moon To: space-tech%cs.cmu.edu@vma.CC.CMU.EDU X-Organization: University of Wisconsin--Platteville [Sorry everyone for the null message, a long set of wrong keys caused it] {I also figured out that nm means nautical miles. Which are noticably bigger than nanometers :)} As threatened, I have here a post of some ideas I have as well as an alterior(sp?) motive at the end. The premise is this: suppose somebody buts a base on the moon (Base A) and somebody (not nessisarily a different organization) puts another base on the moon. The bases are beyond line-of-sight radio communication. [this would be less than the los distance on Earth since the Moon "curves faster", but if you insist on a distance, 1000kM] How would these two bases communicate with each other? (which they might want to do even if one or both are not manned) Since I don't think the Moon has a usable ionosphere, here are some ideas: {I also assume that the Moon's permitivity/permiability/conductivity is such that radio signals cannot go through it. I base this on the fact that many radio amateurs bounce thier signals off the moon (called EME-Earth-Moon Earth)} #1:Landline (either copper or fiber-optic [preferred]). This might be used when the bases are established, but I can't imagine a line being fed right away. Would meteor damage be a threat? (a 1cm diameter cable would have an area of 10000m^2). How much bother to bury it? Don't forget about any repeaters needed. Which gives option 1.5, have some radio repeaters placed between the two bases. #2:LLO (Low Lunar Orbit) sat. If the bases were farther apart, they might not be able to see the sat. at the same time. I'm sure message storage and forwarding could be used for routine messages, but what if real time conversation was needed? The satelite might not be in either bases view. This might be solved with enough sats in orbit, assuring that at least one is usable by both bases. #3:Lunosynchronous Orbit. I'm not sure the dynamics or even the possibility of LSO, but if it could be parked anywhere above the "equator" of the moon, the two bases could always be in contact, even if on opposite sides of the moon (given arbitrarily high antennas, again, I don't know the dynamics of LSO). Can anyone enlighten me on the physics of LSO? [Side note: is there an "Equator" of the Moon? A North and South Pole? How about Greenwhich and the International Date line? In short, is there a coordinate system for the Moon?] #4:Earth Relay:An Earth station would simply relay the message. Assuming that the delay is acceptable and niether base is on the "dark side" (bad name, but we are stuck with it) this would work. #5:Bounce the signal off the Earth. Since people with thier own money and time can bounce signals off the Moon, I imagine it would not be hard for two organizations to do the reverse. After all, The Earth has an ionosphere and lots of salt water, which bounce signals nicely. The downcomings of this are the same as #4. What do you think? Is this a really dumb idea/line of questions? Alterior(sp?) motive: I'm sure everyone on this list has heard of N. Armstrongs "One small step for [a] man..." message, I am curious about the signal itself. That is, what were the frequencies, modes (AM,FM,SSB,...),power, antenna types, polarization, etc. of the message sent from the Moon? (and for that matter, from the suit to the LEM). Does anyone have any facts concerning this? Sorry for the long post Brian P. McCarty (N9IWP) bitnet:UCSBPM@UWPLATT internet:UCSBPM@UWPLATT.EDU The opinions here do not reflect those of UWP, DEC (The terminal/computer I'm using), or Casio (the calculator I used) ###Hi GKO### ------------------------------ Date: Tue, 27 Feb 90 23:47:37 -0700 From: SEDS-UNM To: UCSBPM@uwplatt.edu, space-tech@CS.CMU.EDU Subject: Re: CQ Moon ..--.. -. -.... .-.. - .--- ------------------------------ Date: Wed, 28 Feb 90 14:12:03 PST From: Edmund Hack X-Vmsmail-To: AMES::"space-tech@cs.cmu.edu" Subject: Re: CQ Moon To: space-tech@CS.CMU.EDU Given that one of the major justifications for builing a moon base is astronomy (and being a former astronomer), I hope that any lunar communications system is built with an eye to keeping emissions to a minimum. I would suggest the use of either fiber optic cable, line of sight lasers or laser comsats. (See this month's Scientific American for a discussion of astonomy on the lunar farside). I'd like to see a treaty set up to minimize radio use on the farside to protect the near term science uses (with a cut-off date for the treaty, etc.). Edmund Hack Lockheed ESC hack@lock.span.nasa.gov ------------------------------ Date: Wed, 28 Feb 90 17:05:59 CST From: "Edward V. Wright" To: UCSBPM@uwplatt.edu, space-tech@CS.CMU.EDU Subject: Re: CQ Moon > #2:LLO (Low Lunar Orbit) sat. Lunar orbits tend to be unstable due to the perturbations caused by the Earth. All of the lunar communications satellite proposals I have seen place the satellite in one of the Lagrangian Libration points. ------------------------------ Date: Wed, 28 Feb 90 20:18:58 EST From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. To: space-tech@CS.CMU.EDU Subject: lunar communications >Given that one of the major justifications for builing a moon base >is astronomy (and being a former astronomer), I hope that any lunar >communications system is built with an eye to keeping emissions to >a minimum. I would suggest the use of either fiber optic cable, >line of sight lasers or laser comsats. A problem with laying cable along the ground is that you create huge areas through which you can not drive without the risk of breaking the cable, unless you include "passes" along which the cable is buried or strung along elevated poles. I would prefer satellites, earth relay, or line-of-sight lasers or microwaves. It might be possible to minimize interference with radio astronomy by limiting communications to a few specific frequencies. John Roberts roberts@cmr.ncsl.nist.gov P.S. Did you get the SSX address from Todd? ------------------------------ Date: Wed, 28 Feb 90 18:08:07 mst From: Paul Bame To: space-tech@CS.CMU.EDU Subject: Re: CQ Moon To tackle both redundancy (really, reliability) and RFI pollution (how about optical pollution?) how about using passive orbital (synchronous?) reflectors - maybe metalized balloons (sound familiar?). Balloons can be constructed as broadband reflectors (not too efficient reflectors perhaps) and only contribute to RFI pollution when someone's emitting RF. There are no "polluting" transmitters on the reflectors - this also means we are free to choose/change uplink/downlink frequencies. Clever folks might even use balloons for optical communication. Spherical reflectors are handy since you don't have to orient them but are not too great gain-wise. Maybe some gain over a sphere could be realized with another shape and passive orientation used to "aim" it. Full lunar coverage would probably require a repeater. By eliminating the orbiting electronics, reliability is mostly a ground problem. Ground equipment can be replicated for redundancy and is also accessable for repair. Orbiting reflector satellites are potentially relatively cheap and of potentially low mass. Ground expenses are higher than some active satellite systems since higher-gain systems are required for passive bounce communication - but these systems might be carefully engineered to also be capable of Earth communication and/or bounce to do multiple duty. It is kinda too bad I couldn't use my 2meter 5Watt handheld directly but maybe with a little dish.... It might be interesting for someone less lazy than I to calculate the round-trip time to a lunar-sychronous satellite. I know I sure hate using geo-sync satellite phone circuits. -Paul Bame N0KCL ------------------------------ Date: Wed, 28 Feb 90 22:35:39 EST From: dietz@cs.rochester.edu To: space-tech@CS.CMU.EDU Subject: CQ Moon A suggestion I made to this list some time ago for lunar communication is very lightweight relays kept aloft by radiation pressure. These satellites would be much closer than Lagrange point satellites, reducing signal travel time. Consider a 1 gram satellite 1 lunar radius above the surface. A 120 kilowatt laser will levitate a nonreflective satellite; only 60 kw is necessary if the satellite is a perfectly reflective plane mirror perpendicular to the beam. The satellite would carry a miniaturized microwave repeater, powered by thin photovoltaic cells operating off the laser beam. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Wed, 28 Feb 90 21:27:58 PST From: Richard Schroeppel To: space-tech@CS.CMU.EDU Subject: Lunar-synchronous satellite Paul Bame writes > It might be interesting for someone less lazy than I to calculate the > round-trip time to a lunar-sychronous satellite. I know I sure hate using > geo-sync satellite phone circuits. The earth is in synchronous orbit around the moon. From a particular place on the moon, the earth oscillates about a constant position in the sky. (The oscillation is because the moon's orbit is an ellipse.) As another poster pointed out, the other constant sky position orbits (relative to the lunar surface) are the L4 and L5 points. These lead and lag the moon by 60 degrees, so they are as far from the moon as the earth is. Round trip light time from moon to earth & back is about 2.5 seconds. Rich Schroeppel rcs@la.tis.com ------------------------------ Reply-To: davidsen@crdos1.crd.ge.com Date: Thu, 1 Mar 90 08:36:24 EST From: davidsen@crdos1.crd.ge.com To: space-tech@CS.CMU.EDU Subject: reflector satellites (CQ moon) > Ground expenses are higher than some active satellite systems since > higher-gain systems are required for passive bounce communication - but > these systems might be carefully engineered to also be capable of Earth > communication and/or bounce to do multiple duty. I believe that in the 60's some hams on the east coast communicated with Hawaii via moon bounce. The propigation delay is pretty massive, though. Perhaps a reflector at L5, although that may be too valuable to use for communications. Of course "low orbit" of Luna means "miss the mountains" since drag is pretty minimal, and that might allow some new technowlogy, like slingshot launch from the moon, let the orbit perturb, launch a few a week as needed. A Mylar baloon with a few grams of gas to keep it in shape would be reasonable to ground launch, with just enough added control to kick the orbit roughly circular. -- bill davidsen (davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen) "Stupidity, like virtue, is its own reward" -me ------------------------------ Date: Thu, 1 Mar 90 10:08:29 EST From: John Sahr To: space-tech@CS.CMU.EDU Subject: reflector satellites (CQ moon) From: davidsen@crdos1.crd.ge.com (Bill Davidson) >> Ground expenses are higher than some active satellite systems since >> higher-gain systems are required for passive bounce communication - but >> these systems might be carefully engineered to also be capable of Earth >> communication and/or bounce to do multiple duty. > > I believe that in the 60's some hams on the east coast communicated >with Hawaii via moon bounce. The propigation delay is pretty massive, >though. "Moonbounce" or EME is still practiced by radio amateurs around the world. It has been accomplished at frequencies as low as 28 MHz (I think) and up to several GHz. The most common frequencies are near 144, 432, and 1296 MHz. The point of EME is to merely make contact via an unusual mode. EME is worthless for high, reliable data rates, unless you have regular access to much more powerful transmitters than are allowed radio amateurs (1 kW), or truly huge antennas. EME is possible within the constraints of the radio amateur license, but is beyond the reach of most. The moon, or any planet for that matter, is a reasonably poor reflector from a communication standpoint. The Earth, for example, has radius 6400 km, and a radio pulse will thus be stretched to nearly double that (12800 km) upon reflection. Folding in the speed of light, this amounts to delays of 40 milliseconds. The information in such delayed signals is enough to allow the mapping of Venus with the Arecibo radar (and other tricks were employed as well). While we're talking about detecting planets with radar, I'll throw out a few fun facts: 1) Several moons of Jupiter (and of Saturn) have been detected, but Jupiter itself has not; and 2) The Sun has been detected (at about 42 MHz, I believe). >Perhaps a reflector at L5, ... [] > A Mylar baloon ... The balloon approach has been accomplished at Earth, with the Echo satellite. However, active satellites can be quite small, cheap, effective, and reliable, as evidenced by the several Amateur Radio satellites. Such satellites permit much less expensive ground stations, as transmitter power on the order of 10 Watts and an antenna the size of a rooftop TV antenna will suffice. I have done this myself, pointing the antenna by hand, and hand adjusting for the Doppler shift; I have been able to hear my downlink from OSCAR 8 when I was transmitting only 1 Watt. Mentioning OSCAR 8 dates me, alas. There are newer, and perhaps more interesting amateur radio satellites since then, including especially the "Molniya" orbit satellites, which are relatively stationary over high (Earth) latitudes for hours at a time. ------------------------------ To: space-tech@CS.CMU.EDU, mikew@neptune.fx.com Subject: Re: CQ Moon Date: Thu, 01 Mar 90 08:26:04 -0800 From: mikew@neptune.fx.com One last point about dropping a cable from an orbiting space-ship, I'm fairly sure I've seen references to fiber-optic cables that have gone 1000 KM without repeaters. I will try to verify these references, but it was just a blurb in a magazine several years ago. ------------------------------ To: space-tech@CS.CMU.EDU Subject: Re: lunar communications Date: Thu, 01 Mar 90 08:22:21 -0800 From: mikew@neptune.fx.com Why can't a fiber-optic cable just be dropped by a space-ship flying over. It would drop one end of the cable over the site of the first base and the other end over the site of the second base. This could be just an interim system, but it seems to have a lot of benefits: 1. Cheap (just the cost of the fiber and dropping it) 2. Light (at least compared to a copper cable or even the equipment to bury a fiber-optic cable. 3. No radiation problems. 4. Can be replace quickly. 5. High band-width. Their are some drawbacks 1. It would be a target for meteors. Although it wouldn't need to have as large a cross section as a previous post suggested. 1mm diameter should be sufficient for a starter system which mean a 1km cross section. 2. Would be a hazard for drivers. 3. Might have trouble with the heat cycling. 2 Weeks of very hot, followed by 2 Weeks of cold. If the system were expanded by layer more instead of thicker cables, the reducancy would help alleviate problem 1. Other solutions would be necessary for problems 2 and 3. So what do you think? ------------------------------ To: space-tech@CS.CMU.EDU Subject: Dropping a cable on the moon Date: Thu, 01 Mar 90 13:22:26 -0800 From: mikew@neptune.fx.com I don't think snags are an insoluble problem. The idea is to drop the cable on the site, not drag it along. This would require unreeling the cable at orbital speed and some pretty precise aiming, but it still seems easier than burying a thousand kilometer cable. Or even bring along a vehicle cable of laying out the cable. ------------------------------ Date: Thu, 1 Mar 90 17:21:41 CST From: Lou Adornato To: mikew@neptune.fx.com, space-tech@CS.CMU.EDU Subject: Re: Dropping a cable on the moon >This would require unreeling the cable >at orbital speed and some pretty precise aiming, but it still seems easier >than burying a thousand kilometer cable. Or even bring along a vehicle cable >of laying out the cable. Why would the cable need to be payed out from an orbiting body? Just fire a sounding rocket from point A to point B with the fiber paying out behind. The DoD types have all sorts of wire guided missiles and torpedoes in development or in use. Given the low surface gravity on the moon, it wouldn't take that much of a rocket to send out a _LOT_ of cable. By the way, according to Tannenbaum, bandwidth must be traded for distance. Currently, the art can sustain 100 Mbps for a kilometer without repeaters, and it's possible to drive a 100km long fiber using a big enough laser, although at "much lower speeds". So, the question is, is 100km longer than line of sight on the moon? If not, why not just use line of sight laser communications, and forget the fiber. Lou Adornato | Statements herein do not represent the opinions or attitudes Cray Research | of Cray Research, Inc. or its subsidiaries. lfa@cray.com | (...yet) ------------------------------ End of Space-tech Digest #51 *******************