Subject: Space-tech Digest #54 Contents: Kevin Driscoll Re: LunaComm Requirements John Roberts Lunar mountains Doug Reeder Lunar communications Paul Dietz Those Darn Minicomets George Herbert Re: Those Darn Minicomets Bill Higgins AIAA solicits your Moon/Mars ideas [ from sci.space ] Marc Ringuette Re: AIAA solicits your Moon/Mars ideas ------------------------------------------------------------ Date: Thu, 8 Mar 90 17:20:34 CST From: Kevin Driscoll To: space-tech@CS.CMU.EDU Subject: Re: LunaComm Requirements Sender: mnr@DAISY.LEARNING.CS.CMU.EDU > . . . > What about teleoperated equipment? How much bandwOBidth > does that require? > . . . > 3) Very high bandwidth teleoperated robots (video+control channels) > . . . Latency is more important that bandwidth in these "control-loop" functions. It does no good to have jig-a-hurts bandwidth if the round trip delay is measured in seconds. How much can a fiber optic cable be protected from physical and radiation effects by just sweeping dust and rubble over it; as an alternative to true burying? A mesh or ladder layout of the fiber and repeaters (R), as shown below, is very damage tolerant. The cable itself is not fragile. Some military cable I have seen is amazingly tough and still small size. Driving over it with a moon buggy should not be a problem. Aging losses due to radiation and other effects can be compensated for by putting the repeaters closer together and/or over-sizing the light sources and adjusting them as needed. The sensing and adjusting can be done remotely as is done for trans-oceanic cables. -----R---------------------R---------------------R---------------------R---- | | | | | | | | -----R---------------------R---------------------R---------------------R---- ------------------------------ Date: Thu, 8 Mar 90 22:49:37 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 mountains >Has anyone looked at the topography >of the Moon? I believe the moon has higher mountains and deeper "valleys" than the earth. Unfortunately, it also has a much smaller radius of curvature. For instance, even if a crater has a very high rim, you will not be able to see one side from the other unless it's a relatively small crater (the middle "depression" will get in the way). I don't know what the overall result is. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ From: oresoft!reed!reeder@uunet.uu.net To: space-tech@CS.CMU.EDU Cc: reeder@uunet.uu.net Subject: Lunar communication Date: Mon, 12 Mar 90 21:20:11 PST IMHO, the best way to communicate between two moonbases is by way of earth stations. Any signifigant moonbase will need to communicate with Earth anyway, so you just make sure the bandwidth is big enough. Furthermore, all the equipment that's not at your bases is at a location that's easy to get repair techs to. Distance and atmosphere can be overcome by sensitive recievers and powerfull transmitters. Time lag is a problem for voice communication, but not for data. Time lag, Moon-Earth-Moon = 2*semimajor axis / speed of light = 2 * 3.84403E8 m / 3.00E8 m/s = 2.56 s Farside bases and expeditions will need repeaters of some kind. Low orbit satelites could relay to local bases and expeditions, but would have to chain to other low orbit satelites to reach nearside, or store messages until they were above the recipient. (This system sounds like it would have propagation delays worse than USENET, because messages would queue up waiting for storage space on satelites.) A repeater at L2 would require at least one other repeater. A second repeater on the nearside-farside boundary (which is a circle, don't forget, so we have a lot of sites to choose from) would be subject to libration, i.e. the Earth would appear to dip above and below the horizon. The _CRC Handbook of Chemistry and Physics_ doesn't list anything about libration (along with a lot of other things it should), so I can't calculate the height of the tower neccesary to keep both Earth and L2 in view at the same time, but I believe side-to-side libration is less than up-and-down libration, favoring sites near the equator. You can put this repeater on a mountain to shorten the tower, but then you have to land the repeater on a mountain, or haul it up there, neither one an easy task. You could put the repeater at L4 or L5, for a delay of 2.56 s for moon-L5-moon, slightly longer for moon-L2-L5-moon, 3.844 s for moon-L5-earth-moon, or 4.74 s for moon-L5-L4-moon. Remember, these times are one-way, so if you try to converse with someone, it will be from 5.12 s up to 9.5 s before you see your partner's response to your last statement. (Trying to talk with such time lags would be an interesting science fair experiment) With repeaters at L4 and L5, you can cover approximately 120+90+90 degrees of longitude directly, or 83% of the moon's surface. A repeater in L2 halo orbit can talk directly to earth if it can manage a halo with a 2000 km radius. This would eliminate the need for the second repeater. Another important consideration is that the problem is NOT that bases A and B need to talk to each other; actually, bases A,B,C,D,E,F and G want to talk with each of the others, with Earth, with spaceships and satelites in Earth and lunar orbit, and with expeditions in the field. Computerized switchboards are easily built, as are store-and-forward data networks. The question is: How well does your communication network deal with broken links, equipment down for repair, equipment of varying ages and national standards and a varying number of nodes and data flow rates? Would you like to manage your lunar setup through the internet? ___________________________________________________________________ LUNANET: mail not delivered to Edward@farside.astro: Incompatable data compression: Message follows: Subject: Re: Delays I'm afraid that oxygen shipment is going to be delayed further, as the launch technicians are on strike again. Be sure to sure to stop industrial use immediately. -Donna ____________________________________________________________________ Doug Reeder USENET: ...!tektronix!reed!reeder from ARPA: tektronix!reed!reeder@berkeley.EDU BITNET: reeder@reed.BITNET the Little Mermaid on materialism: I just don't see how a world that makes such wonderful things ... could be bad! ------------------------------ To: space-tech@CS.CMU.EDU Cc: dietz@cs.rochester.edu Subject: Those Darn Minicomets Date: Wed, 14 Mar 90 15:23:17 -0500 From: dietz@cs.rochester.edu A couple years back, there was a flurry of activity when a fellow named Frank at U. of Iowa claimed to have found evidence that the earth was being bombarded by very large numbers of minicomets, each maybe 5-10 meters across. He got lots of flack for this, since the comets would have to have remarkable properties to have escaped prior detection, especially if they are icy, as was claimed. The latest issue of Astronomy and Astrophysics, though, has some results from Yeates, Frank, and (I forget the name), searching for these objects using Gehrel's (U. of Arizona) Spacewatch Camera. They searched for the objects by pointing the camera at a target region, locking it in position, and doing time delay integration with the CCD as the earth's rotation moved the image. They recorded for 12 seconds, shuttered the camera for 36 seconds, then recorded another picture for 12 seconds. The comets would have produced, in each frame, a track of about ten pixels, with the signal in each pixel only about 1 sigma above background noise. However, by looking for pairs of tracks in the two pictures, separated by the correct distance, they got a number of good detections. The results are consistent with a large number of cometesimals in prograde, low inclination solar orbits, moving at about 10 km/s relative to Earth. The estimated density of the objects is about 3 x 10^-11 km^-3. Alternately, the tracks could be caused by maybe 10^5 previously unknown objects in high earth orbit (GEO and beyond) [ perhaps fragments blasted off the moon? ]. I think the implications are interesting for space activities. If the cometesimals exist at the indicated density, then a 10 km^2 powersat would be hit by a cometesimal roughly once every ten years. If the powersat was in GEO, much of the material knocked out of the powersat would go into GEO intersecting earth orbits, and would continue to bombard anything there. If there are 1000 powersats in GEO, we can expect about two collisions every week. Ouch. If only Gehrels would get a better (read: current technology) CCD for the Spacewatch Camera, they'd have this nailed down. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Wed, 14 Mar 90 22:08:26 PST From: gwh%ocf.Berkeley.EDU@lilac.berkeley.edu To: dietz@cs.rochester.edu, space-tech@CS.CMU.EDU Subject: Re: Those Darn Minicomets The Oort cloud Comet Search may find objects like that too, though it's looking further out as its primary target zine. -george [i can explain the comet search if people want; one of the principal investigators gave a talk about how it worked to the SPACE club here.] ------------------------------ [ forwarded from sci.space .... --Marc ] From: HIGGINS@FNAL.BITNET (Bill Higgins-- Beam Jockey) Subject: AIAA solicits your Moon/Mars ideas Date: 13 Mar 90 22:53:00 GMT Sender: usenet@ucbvax.BERKELEY.EDU Well, gang, here's something to provoke thought. Below is the text of an announcement on page 47 ot the March 1990 issue of *Aerospace America*, the magazine of the American Institute of Aeronautics and Astronautics. This group is the principal professional organization for aerospace engineers. ============================================ WE WANT **YOUR** IDEAS on Human Exploration of the Moon and Mars NASA has asked the AIAA to solicit and evaluate innovative *technical* features of the greatest venture in human history. If you or your organization have a technical concept that you think might be useful in exploring the Moon and/or Mars, send a summary *not exceeding one double-spaced page, plus a maximum of one illustration*, to: Ms. Joanne Padron Workshop Program Manager AIAA Headquarters [The ad does not mention the address, but it is 370 L'Enfant Promenade, SW, Washington, DC 20024.] CATEGORIES OF INTEREST ARE: 1) Overall mission architecture 2) Transportation technologies and systems 3) Life-support technologies and systems for space and lunar/Mars surfaces 4) Infrastructure technologies (communications, information sensing and processing, automation and/or robotics, electric power generation, space platforms, spacecraft servicing, lunar/Mars mining and material processing, etc.) The deadline for submission of your ideas is April 15 1990. You will be asked to submit additional material if your concept is selected for more detailed evaluation. Concepts not accepted will be returned. The AIAA will *not* reimburse any cost associated with the submittal, assessment, or implementation of your idea, and does not guarantee any NASA action on it. The AIAA will *not* be responsible for protecting proprietary or classified information-- do *not* send any such material. ============================================== Have fun. And let the Net know what you submitted, okay? O~~* /_) ' / / /_/ ' , , ' ,_ _ \|/ - ~ -~~~~~~~~~~~/_) / / / / / / (_) (_) / / / _\~~~~~~~~~~~zap! / \ (_) (_) / | \ | | Bill Higgins \ / Fermi National Accelerator Laboratory - - Bitnet: HIGGINS@FNALB.BITNET ~ Internet: HIGGINS@FNAL.FNAL.GOV SPAN/Hepnet/Physnet: 43011::HIGGINS ------------------------------ Date: Wed, 14 Mar 1990 16:23-EST From: Marc.Ringuette@DAISY.LEARNING.CS.CMU.EDU To: space-tech@cs.cmu.edu Subject: Re: AIAA solicits your Moon/Mars ideas I was just thinking of trying to sketch out an idea for them: a robotic, teleoperated "construction team" of about 50 little (say, 20-pound) robots designed and operated in completely distinct ways (for redundancy and flexibility), which would operate on the moon and be able to put together payloads shipped there in kit form. They would be teleoperated from an earth station, and use common communications equipment. I'll try to think this out some more - any ideas? /////////////////////////////////////////////////////////////////////// /// Marc Ringuette /// Carnegie Mellon University, Comp. Sci. Dept. /// /// mnr@cs.cmu.edu /// Pittsburgh, PA 15213. Phone 412-268-3728(w) /// /////////////////////////////////////////////////////////////////////// ------------------------------ End of Space-tech Digest #54 *******************