Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from holmes.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr1/ota/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr1/ota/space/space.dl) (->ota+space.digests) ID ; Wed, 12 Apr 89 00:18:49 -0400 (EDT) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Wed, 12 Apr 89 00:18:39 -0400 (EDT) Subject: SPACE Digest V9 #359 SPACE Digest Volume 9 : Issue 359 Today's Topics: Soviet Mir space station in trouble Gigantism of SPS Assaying likely asteroids from afar Re: Assaying likely asteroids from afar Re: Success with cold fusion reported Reminders for Old Farts Re: Hubble Space Telescope jim benz and kicking us off dis heah planet Re: more on Liberty Bell 7 (and other s'craft) Re: far side of the Moon photo mission (ussr's) constant-boost fusion spaceships, power requirements of ---------------------------------------------------------------------- Date: Tue, 11 Apr 89 23:57:37 EDT From: Glenn Chapman To: XB.N31@forsythe.stanford.edu, space-editors-new@andrew.cmu.edu, yaron@astro.as.utexas.edu Subject: Soviet Mir space station in trouble The Soviet Union has suffered a serious problem with its Mir space station. What exactly is wrong was not stated but on April 11 Radio Moscow announced that the current crew (Dr. Valrey Polyakov, Alexander Volkov and Sergei Krikalev) will be returning to earth on April 27th. They are currently preparing the station for operation in an unmanned automatic mode. Originally Soyuz TM-8 was scheduled for launch on April 19th to bring a two man crew of Alexander Viktorenko and Alexander Balandin. It is not likely that the problem is with the new crew (there is always a backup team) or the launcher/capsule. If that was the case they would probably just have ordered the current crew to stay up there another two months until the next launch window, in mid June. There Soyuz TM-7 is about 4 months old at this point, 6 is the maximum they keep capsules up there for. Also, they have in the past sent a Soyuz up on automatic to a space station to replace a capsule that was suspect (in June 1979 Soyuz 34 was sent up to Salyut 6 to replace the Soyuz 32 which had exceed the [then] 90 day limit because of the failure of Soyuz 33 to dock to the station). All of this suggests that there has been some failure on board the Mir station. There have been some rumors that there were problems with the gyroscopes in the Kvant section, but if these were true that should not be reason for leaving Mir unmanned (it was run without them for many months even with the Kvant module attached). However, it cannot be a life threatening problem; an emergency landing at this time would be relatively safe, and the normal Mir launch/landing window opens on April 19th. Thus this crew is coming down near its expected time of April 29th. There was no statement as to the cause of the problem, not in the keeping with the current Glasnost tendency. After the Phobos II loss and the sinking of the Mike class nuclear submarine it appears that one more failure was a bit more than the news service could take in a one month period. One can speculate that they are studying the situation and will send up a repair crew after the proper equipment has been manufactured. Thus it appears that there will be a hiatus in the permanent presence of humans in space. The Russians came close, but it looks like they will not pull it off. On the other hand they did get a 26 month run - mankind's best result so far. Glenn Chapman MIT Lincoln Lab ------------------------------ Date: 9 Apr 89 15:55:42 GMT From: rochester!dietz@bbn.com (Paul Dietz) Subject: Gigantism of SPS In article <3073@uvacs.cs.Virginia.EDU> rwl@uvacs.cs.Virginia.EDU (Ray Lubinsky) writes: >I hate to break the news to you, but SPS never had a chance anyway. For >starters, it requires a huge infrastructure, massive startup costs, and >potential biohazard (at least, I'll pass on living anywhere near the microwave >collectors, thank you). SPS gets more practical if you posit the existence of moderately efficient sun-pumped lasers. At constant beam power density, the power output of an SPS scales linearly with the wavelength of the beam. If a lambda = 1 cm system needs 10 GW, a 1 micron system could operate at 1 MW. The aperture of the transmitter and receiver shrink by a factor of 100. Probably it pays to make the beam a bit more intense to burn through clouds. Of course, you'd need some way of efficiently converting laser light to electricity. That should be easier than converting sunlight, since laser light is far brighter and is monochromatic. I believe 50% efficiency has already been attained with PV cells with the proper bandgap. The start-up costs of making the SPS factory are still exorbinant. > Personally, I imagine that after some substantial (on orbit) research > of 0 G materials processing, there will be hundreds of reasons for the > development and habitation of LEO and the Moon. This man is an optimist. I think zero-gee materials processing will have very limited market penetration, and will no more promote habitation of the Moon than did the comsat industry. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: 9 Apr 89 11:35:29 GMT From: amdahl!drivax!macleod@ames.arc.nasa.gov (MacLeod) Subject: Assaying likely asteroids from afar ;To supply the whole world at this (first world) rate requires 5e12 Kg total. ;Assuming 3% ore @ 3.5gm/cc, this is an equivalent sphere 4.5 Km in diameter, ;weighing 5e9 tons or 5e12 Kg. ;There exist at least 40,000 asteroids larger than 5 Km in diameter. ; ;2. Asteroid mining energy considerations ;---------------------------------------- ;The deltaV from the Belt to Earth is 7 Km/s. Moving 5e12 Kg of asteroid ;needs 1e20 joules (about 1% of world's annual (1978) energy use). ; ;Reproduced without permission from "A Step Farther Out" by Jerry Pournelle In a note to Mike Van Pelt I suggested that we take one of the one-shot SDI lasers, aim it at a likely asteroid, and light if off. This should give us enough reflected signal to spectrographically assay the rock (or metallic lump, we would hope). Mike replied that it sounded feasible except for the political constraints of the treaty which bans atomic explosions in space. I'm sure he's correct, but it would be nice, in the current thaw in the cold war, if we could convince them that we weren't up to something. After all, I'm sure they would rather see them pointed someplace else. Michael Sloan MacLeod (amdahl!drivax!macleod) ------------------------------ Date: 9 Apr 89 20:38:58 GMT From: pyramid!nsc!andrew@lll-lcc.llnl.gov (andrew) Subject: Re: Assaying likely asteroids from afar In article <4528@drivax.UUCP>, macleod@drivax.UUCP (MacLeod) writes: > In a note to Mike Van Pelt I suggested that we take one of the one-shot SDI > lasers, aim it at a likely asteroid, and light if off. This should give us > enough reflected signal to spectrographically assay the rock (or metallic > lump, we would hope). What immediately springs to mind here is the possibly of _in situ_ smelting. It's been suggested by others that a solar mirror melting arrangement might do it, but (without doing the calculation) this sounds impractical. Such a laser would come in very handy. I'm not sure whether it would be practical to leave it in earth orbit though; fine control at this range and relative velocity would make smelting haphazard and dangerous for the local-to-asteroid miners B^) Smelting before transportation can be extremely cost-effective, especially if the ore is not particularly rich. ------------------------------ Date: 7 Apr 89 03:48:12 GMT From: attcan!lsuc!ncrcan!moegate!soley@uunet.uu.net (Norman S. Soley) Subject: Re: Success with cold fusion reported In article <3634@sdsu.UUCP> frost@sdsu.UUCP (Richard Frost) writes: >In article <4182@ttidca.TTI.COM>, hollombe@ttidca.TTI.COM (The Polymath) writes: >> In article <1052@elmgate.UUCP> maa@elmgate.UUCP (Mark Armstrong SOFT) writes: >> [...] >> }Why do you think it would be more efficient to produce your own electricity >> }instead of buying it from utilities?? What would be the cost of such system, >> }$5,000 sounds realistic. ... >> >> That's about what I cost it out to. I'd cheerfully pay $5000 to be energy >> independent. > >Although utility companies are required to by any excess power you generate >YOU are responsible for purchasing a synchonous interface to the grid ( a >synchronous inverter if you're generating DC) plus a new meter and pay for >periodic calibration inspections by the utility company. > >So if there is any merit to the giant 'hill of salt' speculation that we >could all have fusion generators in our backyard, be prepared to add an >additional $1500 to your overhead costs plus $100 to your annual cost. OK let's take it as a given that the Pons & Flieshmann experiment, refined, optimised, and engineered for a few years results in practical generators small enough to bury in one's backyard (personally I think that, initially at least, P&F derived fusion will only be economically practical in power plant sizes). In order for the current power grid to work it is necessary to balance the input and output of the system, or at least attempt to. The amount of power generated by windmills and small hydro-electric plants is a drop in the bucket so the utilites don't worry about it. Most utilities have a centre where they do load balancing, turning on and off generating capacity as it's needed. It's a complex and delicate system, for example the infamous New York blackout of the 60's resulted from a single blown relay near Kingston, Ontario that took enough load off the grid suddenly to crash the whole shooting match, everyone turning their TV's off at the end of the Tiny Tim's wedding episode of the Tonight show came "this close" to putting the whole continent in darkness. A power grid consisting of large numbers of small generators, if possible at all, would require a massive automated control system, and think of the administrative headache of deciding who's generators to take off-line at any point in time. Of course one might ask: if small generators are that cheap and easy why tie them into a grid at all? -- Norman Soley - The Communications Guy - Ontario Ministry of the Environment Until the next maps go out: moegate!soley@ontenv.UUCP if you roll your own: uunet!{attcan!ncrcan|mnetor!ontmoh}!ontenv!moegate!soley I'd like to try golf, but I just can't bring myself to buy a pair of plaid pants ------------------------------ Date: Sun, 9 Apr 89 04:00:11 PDT From: Eugene Miya Subject: Reminders for Old Farts Hints for old users (subtle reminders) You'll know these. Minimize cross references, [Do you REALLY NEED to?] Edit "Subject:" lines especially if you are taking a tangent. Send mail instead, avoid posting follow ups. [100 mail messages mean more than 1 follow-up.] Read all available articles before posting a follow-up. [Check all references.] Cut down attributed articles. Summarize! Put a return address in the body (signature) of your message (mail or article), state institution, etc. don't assume mail works. ------------------------------ Date: 8 Apr 89 20:42:50 GMT From: !cmx!amax.npac.syr.edu!anand@cunyvm.cuny.edu (Anand Rangachari) Subject: Re: Hubble Space Telescope Did anybody read the interesting article in the journal Nature about the Hubble space telescope? It seems that 6 important bolts which hold a mirror assembly within the tube are not properly secured with epoxy and may come loose due to the vibration caused by the launch. Right now, a special platform is being constructed which will allow a worker to enter the telescope without touching the sides of the tube. The worker will then apply the six tiny blobs of epoxy. The whole thing will cost $350,000. R. Anand Internet: anand@amax.npac.syr.edu Bitnet: ranand@sunrise ------------------------------ Subject: jim benz and kicking us off dis heah planet From: IA80024%MAINE.BITNET@VMA.CC.CMU.EDU (Nicholas C. Hester) Date: Sun, 09 Apr 89 15:00:59 EDT jim- i'm sorry, but i refuse to leave this planet if i'm not allowed back on to live. i was borne here and no one has the right to move me off. =nick= ia80024@maine.bitnet ia80024@maine.maine.edu ------------------------------ Date: Sun, 9 Apr 89 12:47:53 PDT From: Peter Scott Subject: Re: more on Liberty Bell 7 (and other s'craft) m2c!wpi!tmurphy@husc6.harvard.edu (Tom [Chris] Murphy) writes: >In article <16680@cup.portal.com> mmm@cup.portal.com (Mark Robert Thorson) writes: >>A few years ago, someone mentioned some Apollo hardware was in the ocean >>(I think it was the LEM from Apollo-13). >There's no way a LEM could survive re-entry. The thing is EXTREMELY flimsy, >I once heard (in a book by Michael Collins I think) that a technician once >dropped a wrench through the hull. I believe that the LEM carried an RTG which was projected to survive re-entry intact. Peter Scott (pjs@grouch.jpl.nasa.gov) ------------------------------ Date: 9 Apr 89 21:51:32 GMT From: ames.arc.nasa.gov!mike@ames.arc.nasa.gov (Mike Smithwick) Subject: Re: far side of the Moon photo mission (ussr's) In article <1989Mar29.210418.4272@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >In article <1452@cfa.cfa.harvard.EDU> mink@cfa.harvard.EDU (Doug Mink) writes: >>*Surveyor 4 Apr. 17, 1967 Soft-landed on moon; returned photos and soil data > >Check your data, please, Surveyor 4 was a failure if I'm not mistaken. >Its transmitter went dead in mid-flight. It conceivably may have made a >successful landing, since landing was completely automatic, but it returned >no data of any kind. >-- The Surveyor 4's signal abruptly cut off about 40 seconds after the beginning of the main retromotor ignition, about 1 1/2 seconds before burnout. The spacecraft was at 49,000 feet above the lunar surface. JPL tried for the next day to re-establish contact, but was unable to. After a "thorough investigation", the review board could not determine the cause of the failure, but concluded that it was a fluke so no spacecraft resdesign was carried out. mike *** mike (cerbral GURU, insert M&Ms to restart) smithwick*** "Oh, I'm just a NOP in the instruction set of life, oh, ohhhh, hmmmmm" [disclaimer : nope, I don't work for NASA, I take full blame for my ideas] ------------------------------ Date: 10 Apr 89 02:34:50 GMT From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo!henry@husc6.harvard.edu (Henry Spencer) Subject: constant-boost fusion spaceships, power requirements of In article <4448@psuvax1.cs.psu.edu> sobleski@gondor.cs.psu.edu (Mark A. Sobolewski) writes: >><....the power requirements are not merely high, but staggering, if > > For the record... I get 1 gigawatt for a 20 kilo-ton (metric) mass >accelerating at 1g. (P=E/t, delta(v)=g*delta(t) (1 second),E=0.5mv^2, >20,000,000kg) (minimum power consumption of course). Ah, but that's for acceleration from 0 to (roughly) 10 m/s. Do the same computation for 1000 to 1010 m/s and you get about 10 terawatts. Yet obviously the same rocket hardware would do either job using the same amount of fuel and energy. Clearly you're not measuring what you think you are. What you are measuring is the amount of energy needed to do that bit of accelerating by pushing on a fixed object. That is, with a catapult rather than a rocket. The math is right, but you have to apply it to what you're actually pushing on, which for a rocket is its exhaust jet. > While not a very large ship.... It still has enough room... Actually it's pretty sizable, I'd say. That's the size of an Invincible- class aircraft carrier. For solar-system work we can build them a lot smaller. However, let's assume that mass for convenience. Now, the power requirement to expel a jet with a mass flow of (dm/dt) and an exhaust velocity of v_exh is 0.5 * (dm/dt) * v_exh^2. So we need to figure out the mass flow and exhaust velocity. Mass flow depends on how long a mission we want to fly and how much fuel we want to carry. Let's say we're going to the asteroid belt and back. In very round numbers, that's a round trip of 1e9 km. For continuous acceleration (i.e. one half of each leg of the trip), time = sqrt(2*distance/acceleration) = sqrt(2*250e9/10) = 224000. That's a quarter of the trip, so the whole thing is 900000 seconds, about 10 days. As for fuel, if we don't want the fuel tank to dominate the whole ship, a fuel fraction of maybe 10% is tops. So that's 2e6 kg of fuel, giving a fuel flow of about 2 kg/s. Clearly fuel pumps, at least, will not be a problem. Now, what about exhaust velocity? There are roundabout ways to compute that, but thrust = (dm/dt) * v_exh due to conservation of momentum, so we can do it fairly directly. Thrust to push 20e6 kg along at 1 gee will be about 200e6 newtons. (We assume a constant thrust; in practice one would throttle back a bit as the ship burned off fuel, to keep acceleration constant, but that complicates the arithmetic no end and does not affect the result much.) So v_exh = 200e6/2 or about 100e6 m/s. The numerate reader will have gone "gulp!" on seeing that number, since it is about 1/3 of the speed of light. Clearly spaceship Invincible's engines are going to be a pretty remarkable piece of engineering. But we press on... We now have the numbers we need. Assuming 100% efficiency and no losses whatever, spaceship Invincible's fusion generator output needs to be 0.5 * 2 * 100e6^2 = 10 petawatts. The numerate reader is having a terrible coughing fit at this point. For the innumerate: a petawatt is a million gigawatts, and the entire power output of Earth, right down to cooking fires, is a small fraction of *one* petawatt. Clearly, Invincible's generators are, um, impressive pieces of engineering in their own right. Clearly 100% efficiency is optimistic. Let's say it's only 99.99%. Then Invincible's cooling system has to dissipate a mere terawatt of heat. (The numerate reader's coughing fit returns. A terawatt roughly equals the electrical power generation of North America.) The easiest way of cooling something is with flowing fluid; radiating heat into space is much more hassle. Assume we use water; it's cheap and available in quantity, and it's a good coolant. Melting from ice and boiling to steam both introduce hassles, so let's say our input is water just above freezing and output is water just below boiling. That's a temperature rise of about 100 C. The heat capacity of water is roughly 4200 joules/kg/C, so each kilo absorbs 420e3 J. So to carry away 1e12 W, we need about 2400 tons per second. Oops. Spaceship Invincible has a *bad* cooling problem. What's more, the numerate reader, having recovered from his coughing, observes that since E=mc^2, boosting the fuel to 1/3 of the speed of light requires converting about 5% of its mass to energy (we speak sloppily here for clarity; physicist readers will please keep quiet). No wonder the power requirement was massive. The n.r. goes on to observe that fusion simply doesn't convert that big a fraction. Invincible's power requirement just cannot be met by fusion, period. Antimatter might do; Invincible would need to burn about 50 grams per second (remember that each gram annihilates its own mass in normal matter). Optimistic fans of antimatter propulsion think that straightforward application of current technology might perhaps get antimatter prices down to $1M/mg. Invincible's operating costs will then be fifty billion dollars per second. I don't think even DoD can afford to fly this spaceship. I could go on, computing things like radiation output from the power system, size of heat radiators, etc., but the numbers all come out to be preposterous. Not just difficult, but beyond current abilities by so many orders of magnitude that straightforward extrapolation of today's technology won't do -- breakthroughs will probably be needed. The moral of the story is, don't get intoxicated by the possibility of easy fusion. It may give us the solar system, but it will not give us 1G constant-boost spaceships. They are fundamentally hard to build; still better technology will be needed. -- Welcome to Mars! Your | Henry Spencer at U of Toronto Zoology passport and visa, comrade? | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ End of SPACE Digest V9 #359 *******************