Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Mon, 7 Jan 1991 01:40:38 -0500 (EST) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Mon, 7 Jan 1991 01:40:05 -0500 (EST) Subject: SPACE Digest V13 #015 SPACE Digest Volume 13 : Issue 15 Today's Topics: Re: Interstellar Light Sails Mir Lottery questions Re: orbiting Earth in the stratosphere by balloon. Re: space news from Nov 5 AW&ST Re: You can help clear cloud over MIR SWEERSTAKES. Re: Interstellar travel Re: Interstellar travel Re: Interstellar travel Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription requests, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 30 Dec 90 22:32:13 GMT From: usc!cs.utexas.edu!news-server.csri.toronto.edu!utzoo!henry@ucsd.edu (Henry Spencer) Organization: U of Toronto Zoology Subject: Re: Interstellar Light Sails References: <1990Dec29.212153.20748@cunixf.cc.columbia.edu>, <1990Dec30.004107.7363@zoo.toronto.edu>, <1990Dec30.100933.19952@prometheus.UUCP> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In article <1990Dec30.100933.19952@prometheus.UUCP> pmk@prometheus.UUCP (Paul M. Koloc) writes: >> .. . If you can build the laser system >>on the necessary colossal scale, laser sails are workable. > >Let's look into the future hazards of this approach: > >A fleet of Sophians were vaporized when they cut through the beam >(during a heated debate). Depends on the power density of the beam. Something a few times the density of sunlight is still very useful for propulsion -- because it is available to much greater distances -- without being terribly dangerous (although you probably wouldn't want to look into it). >After a few decades of flawless performance, the mirror was sabotaged >by the Helicons (a tribe of radical solar orbital environmentalists). Any scheme using "ground"-based power to run spaceships is vulnerable to disruptions at the power station. -- "The average pointer, statistically, |Henry Spencer at U of Toronto Zoology points somewhere in X." -Hugh Redelmeier| henry@zoo.toronto.edu utzoo!henry ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 30 Dec 90 06:36:01 GMT From: cs.utexas.edu!asuvax!mcdphx!xroads!quark@tut.cis.ohio-state.edu (Jerry Rightnour) Organization: Crossroads, Phoenix, AZ 85046 Subject: Mir Lottery questions Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu It would be a lot easier to believe in the Mir Lottery if someone would answer many of the unanswered questions surrounding it. How is it being financed? Apparently the revenue from phone calls can only be expected to pay a small portion of the expenses. Who is putting up the rest? Is this envisioned as an investment that will pay back a return in time, or just a philanthropic giveaway, possibly to stir up American interest in space travel or to embarrass NASA? What is Space Travel Services Corp? Is it intended to be an ongoing business? What do they expect to market? Additional Mir trips? This is an extremely expensive way to introduce a business with such a limited market. Why are the principals allowing these questions to go unanswered? If it is for real, I would think they would be anxious to dispel any questions concerning the legitimacy of the enterprise. Personal endorsements from netters who know the principals are reassuring, but they don't dispel skepticism when the overall proposal just don't make sense. If I am missing information I need to understand this, I would be most happy to be informed. I would like to believe in this, and will certainly enter if shown that it is for real, but for now I remain a skeptic. Jerry Rightnour quark@xroads.cts.com quark@xroads.uucp -- \ / C r o s s r o a d s C o m m u n i c a t i o n s /\ (602) 941-2005 300|1200|2400 Baud 24 hrs/day / \ hplabs!hp-sdd!crash!xroads!quark ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 30 Dec 90 23:29:35 GMT From: uvaarpa!murdoch!faraday.clas.Virginia.EDU!lhb6v@mcnc.org (Laura Hayes Burchard) Organization: University of Virginia Subject: Re: orbiting Earth in the stratosphere by balloon. References: <1990Dec27.113908.11149@pbs.org> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In article <1990Dec27.113908.11149@pbs.org> pstinson@pbs.org writes: >There was an item in an aerospace magazine last October about a planned nonstop >flight around the world in a high altitude balloon. The international crew in >the pressurized gondola was to have included a Soviet cosmonaut. Cruising >altitude was to be at 35,000 ft, or higher in the jet stream. The trip was >supposed to begin and end in Akron, Ohio. It was to have embarked some time in >November with a duration of perhaps 21 days expected. I have seen nothing >further on this and do not know whether they ever left Akron. Does anyone know >the latest status of this interesting project? I saw a documentary on this on ESPN a couple of days ago. Apparently they are behind schedule but on course for a flight in the new year. The most vital element - a test flight of their revolutionary and totally untried double balloon system - went off perfectly. This is one bizarre looking balloon, though. Laura Burchard -- Laura Burchard lhb6v@virginia.edu lhb6v@virginia.bitnet October 3: After 45 bitter years of separation, East and West Germany unite to form a single nation, chastened by the past, hopeful for the future. October 4: Germany invades Poland. --Dave Barry's Year in Review 1990 ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 31 Dec 90 02:26:33 GMT From: att!pacbell.com!mips!spool2.mu.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!rpi!uupsi!sunic!news.funet.fi!tukki.jyu.fi!jyu.fi!otto@ucbvax.Berkeley.EDU (Otto J. Makela) Organization: Turing Police, Criminal AI section Subject: Re: space news from Nov 5 AW&ST References: <1990Dec11.055832.24321@zoo.toronto.edu>, <20699@crg5.UUCP> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In article mcdaniel@adi.com (Tim McDaniel) writes: In article <20788@crg5.UUCP> szabo@crg5.UUCP (Nick Szabo) writes: >Pegasus development costs (to first launch): $50 million >Shuttle development costs (to first launch): $25 billion In article <1698@ke4zv.UUCP> gary@ke4zv.UUCP (Gary Coffman) writes: So your original article was wrong. Instead of 2% the development cost of the shuttle it's 0.02% the cost of the shuttle. Now that's a better deal. 50e6/25e9 is 0.002, or 0.2%. I can e-mail "ic", a good UNIX-based calculator, to anyone who wants it, like these two people. And here I was thinking of billion = 1e12 (T), as it is in other languages than english. I really should try to remember that Anglosaxons can't count :-) (1e9 (G) = "milliard" in most other languages) Say, I could use that ic also... -- /* * * Otto J. Makela * * * * * * * * * * * * * * * * * * */ /* Phone: +358 41 613 847, BBS: +358 41 211 562 (CCITT, Bell 24/12/300) */ /* Mail: Kauppakatu 1 B 18, SF-40100 Jyvaskyla, Finland, EUROPE */ /* * * Computers Rule 01001111 01001011 * * * * * * * * * * * * * * * * */ ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 31 Dec 90 03:28:04 GMT From: att!emory!ogicse!borasky@ucbvax.Berkeley.EDU (M. Edward Borasky) Organization: Oregon Graduate Institute (formerly OGC), Beaverton, OR Subject: Re: You can help clear cloud over MIR SWEERSTAKES. References: <8093.2779956e@jetson.uh.edu>, <15403@ogicse.ogi.edu>, <1747@ke4zv.UUCP> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In article <1747@ke4zv.UUCP> gary@ke4zv.UUCP (Gary Coffman) writes: > >Temper. Temper. If this lottery really results in an ordinary American >civilian actually going to Mir, the attendant publicity could result >in the biggest boost to the American space program since Sputnik. Oh, the END justifies the MEANS, eh? Look, I'm as big a believer in space exploration (I used to work at Goddard) as anybody. I'm just as sick at the budget cuts (that's why I LEFT Goddard) as anybody. But please don't justify a ripoff by say- ing the publicity will be good for the space program. Space exploration will have to sell itself and its own benefits, just as anything else has to, in this age of scarce resources. I happen also to believe that there should be a network of Cray-2-class and Intel Touchstone-class supercomputers so that EVERY UNDERGRADUATE at every state university in the USA can have access to a supercomputer, but if some jerk tells me that I can buy a $10 ticket along with lots of other people and that the winner can have 1000 hours of time on the machine and the other guys can't, then I'm going to yell just as loud about it. That's NOT the way we do science here in the USA! >Frankly I don't care if the organizers make a mint or lose their >shirts. I don't care if a lot of people waste $3 calling the number. Frankly, I DO care. And my point is that I think OTHERS should care as well. >I do care that this may be the last chance in a long time to wake up >the American public to the stretch out, phase out, give up, being planned >for the US space program while the Soviet program plods ahead with a >real permanent presence in space. I don't think you have to worry about the American public knowing about NASA's problems, either in budgets or in how they spend those budgets. NASA's budgets and the American space program are beleaguered precisely BECAUSE that is what the American public wants -- it's the message they have sent AGAIN and AGAIN through their elected representatives. We the people have decided that affordable health care, the environment, a STRONG MILITARY, etc., are more important to us than what is on the surface of the moons of Neptune. I don't like it, I don't agree with it, but that's just the way it is. I remember a time not too long ago when NASA was telling us that the Shuttle would make it possible for ordinary Americans -- poets, artists, even, presumably, bus drivers, to go into space. Well, there was Senator Jake Garn, who survived, and Christa McAuliffe, who didn't, and now there is a Japanese journalist on a Soviet spacecraft. I don't particularly even want to go into space myself any more; I did when I was 16, but I suppose everybody does at that age. So if YOU want to see NASA's budget increased, write to YOUR congress- man and senators -- or Dan "no rocket scientist" Quayle. And don't support ripoffs -- in the long run they do only damage. ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 30 Dec 90 10:07:36 GMT From: prometheus!pmk@mimsy.umd.edu (Paul M. Koloc) Organization: Prometheus II, Ltd. Subject: Re: Interstellar travel References: <1315@geovision.UUCP>, , <1990Dec30.003715.7265@zoo.toronto.edu> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In article <1990Dec30.003715.7265@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: >In article jmc@Gang-of-Four.stanford.edu (John McCarthy) writes: >>Here's a method of interstellar travel based entirely on present science >>and technology... >>The idea is to use an ordinary fission reactor to generate electricity, >>and use the electricity to expel a working fluid at an appropriate >>velocity... >I'm not sure I would call this entirely based on current technology, since >it puts very heavy demands on the reactor technology, given the weight >constraints. (Any electrical-propulsion system suffers badly on this, >in fact, since electricity is a very cumbersome way of handling large >amounts of power. A chemical rocket engine the size of a large man has >the same useful power output as the very biggest power plants.) This is true. However, perhaps tomorrow's technology will include an compact, extremely high efficiency inductive MHD generators. To use this technique the temperature of the energized plasma must GREATLY exceed the operating temperature of any of today's thermoelectric convertors. The power density of a PLASMAK(tm) aneutronic fusion burner will be able to heat the liquid dense fluid blanket to extraordinary temperatures (by today's standards). The fusion heated blanket could be then magnetically contained only long enough to do piping into the energy convertor, through an inductive MHD (IMHD) chamber. Since such a system will utilize initial blanket temperatures far in excess of today's chemical propulsion systems, its conversion efficiency will greatly exceed, and the overall conversion power density would about equal that of the today's big chemical rocket motors. The BIG saving is in weight (mass), since the energy density of fusion FUEL is several million times that of chemical systems. That makes for a huge fuel inventory (mass) difference. Any second order differences in the mass trade off would be overcome just getting the chemical engines to lift off thrust from a cold start. As pointed out above, fission systems (also worse: fusion tokamaks) are not power/mass efficient. Unfortunately, the more elegant fusion approach may get you to the stars, but you will arrive there in a frozen state. I'm hungry Ah! There is an old fusion burner ahead. Let's "Stop and Pop" a couple of Frozen ones into the microwave +---------------------------------------------------------+**********+ | +Commercial* | Paul M. Koloc, President (301) 445-1075 ***FUSION*** | Prometheus II, Ltd.; College Park, MD 20740-0222 ***in the*** | mimsy!prometheus!pmk; pmk@prometheus.UUCP **Nineties** +---------------------------------------------------------************ ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 31 Dec 90 00:28:20 GMT From: agate!shelby!neon!Neon!jmc@ucbvax.Berkeley.EDU (John McCarthy) Organization: /u/jmc/.organization Subject: Re: Interstellar travel References: <13.2770D2C9@egsgate.fidonet.org>, <3034@mentor.cc.purdue.edu> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu This is actually a reply to the following quotation from Henry Spencer, which somewhow I missed. >In article jmc@Gang-of-Four.stanford.edu (John McCarthy) writes: >>Here's a method of interstellar travel based entirely on present science >>and technology... >>The idea is to use an ordinary fission reactor to generate electricity, >>and use the electricity to expel a working fluid at an appropriate >>velocity... >I'm not sure I would call this entirely based on current technology, since >it puts very heavy demands on the reactor technology, given the weight >constraints. (Any electrical-propulsion system suffers badly on this, >in fact, since electricity is a very cumbersome way of handling large >amounts of power. A chemical rocket engine the size of a large man has >the same useful power output as the very biggest power plants.) The formula for the time taken for a journey of distance s is t = 2.1 p^(- 1/3) s^(2/3). Here p is the power handled per unit mass by the system, and it's what Henry Spencer is grumbling about. However, since it enters to the - 1/3 power, if it's too low by a factor of 1000 compared to a chemical rocket, this only means that the journey takes 10 times as long. Since the journeys are multi-generation anyway, the qualitative conclusion that interstellar colonization is feasible is still supported. Naturally, it would be nice to have fission (or fusion) power plants with the power density of chemical rockets. By the way, the main idea of the above proposal is to allow using a working fluid distinct from the debris of the power generation. ------------------------------ Date: 29 Dec 90 20:12:19 GMT From: kr0u+@andrew.cmu.edu (Kevin William Ryan) Subject: Re: Interstellar travel From: dietz@cs.rochester.edu (Paul Dietz) >In article <1990Dec29.070522.21334@zoo.toronto.edu> henry@zoo.toronto.edu (Henr >y Spencer) writes: >> >>Antimatter is probably easier than fusion, unless some seriously oddball >>approach to fusion gives us a practical way to use the high-order reactions >>with minimum neutron emission, or we find some way to reflect fast neutrons >>efficiently. Even the D-He3 reaction produces enough neutrons to be >>troublesome [...] > > [...] > >That aside, the very low efficiency of antimatter production (.1%, >maybe, if we're real good) is a real constraint. A low performance >inertial fusion rocket might have a power output in the gigawatts. >You'd need terawatts of input power (expensive power, in the form of >electricity) to make enough antimatter to achieve the same performance >for extended periods. For really low performance, why not just >use fission-thermal rockets? As I recall, reading Robert Forwards books, the extremely low production efficiency seen so far is a result of the generation process - where the antimatter is produced in research accelerators. There the emphasis is on exact quantitation, and the machinery is far from optimized for the generation process. Antimatter generators designed specifically for the job should be much more efficient. I don't have figures on hand, but I think that the compact energy available from antimatter argues strongly in its favor. kwr Internet: kr0u+@andrew.cmu.edu ------------------------------ End of SPACE Digest V13 #015 *******************