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 00:39:31 -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 00:38:59 -0500 (EST) Subject: SPACE Digest V13 #013 SPACE Digest Volume 13 : Issue 13 Today's Topics: Re: Interstellar travel Re: Interstellar travel Re: Interstellar travel Space News from Flight Int. for Dec90 pure oxygen and spacecraft fire safety 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: 29 Dec 90 00:18:41 GMT From: unixhub!shelby!neon!Neon!jmc@lll-winken.llnl.gov (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 Here's a method of interstellar travel based entirely on present science and technology. It could be developed in time to start an interstellar journey in the next 25 to 50 years. However, the time to get to nearby stars is in the low thousands of years, so mult-generation voyages would be required at the present level of bio-technology. It seems likely that waiting longer to start, even a few hundred years, would result in an earlier arrival time. The only reason why anyone would want to start sooner would be to escape political events. Thus either side in World War II, faced with the certainty of defeat, would probably have launched such an interstellar voyage. 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. The appropriate velocity is a compromise between wanting a high specific impulse to get a large delta-v and getting a high enough thrust to build up velocity in a reasonable time. It turns out that the exhaust velocity should be low at first and increase during the journey and should depend on the distance to the star to which the voyage is made. The time t required to go a distance s is given by a formula that looks like t = 2.1 p**(- 1/3) s**(2/3). The constant 2.1 is approximate. Here p is a figure of merit of the power generator and rocket system, namely the power handled per unit mass of equipment, e.g. watt/kg if mks units are used. The calculation is non-relativistic, and the formula is over-optimistic if relativistic velocities are to be obtained. It also is correct only when the optimal mass flow is much larger than the rate at which the reactor generates fission products. If this is not the case, then the correct strategy is to just use the fission products, somewhow separated, as reaction mass. The formula leads to the following conclusions. 1. It provides an existence theorem for the feasibility of human occupation of the galaxy in less than a million years. This conclusion requires no new science and not much new technology. 2. The factor p**(- 1/3) means that improving the technology is not going to avoid multi-generation voyages even to nearby stars. You need a factor of 1000 improvement to reduce the time by a factor of 10. 3. The factor s**(2/3) means that all the nearby stars are accessible in qualitatively similar times. If I remember correctly, the formula is approximately correct to distances of 600 light years. Here are two social opinions. 1. Multi-generation voyages are feasible socially. The existence theorem is provided by the existence of reasonably stable tribes of the population level that can be supported. 2. It is a mistake to suppose that whether to undertake the colonization of the galaxy is necessarily a decision to be taken by humanity as a whole. The corrrect question is whether any group with the necessary resources will undertake the journey, and whether the rest of humanity will refrain from suppressing the effort. I don't believe this is the most likely variant to be chosen. Probably, Robert Forward's ideas about using solar system based lasers to transmit power to spacecraft that it will use to expel working fluid will work and will have higher performance. This idea was advanced only to argue that interstellar colonization is feasible in times small compared to the normal life of a species. ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 29 Dec 90 11:14:29 GMT From: prometheus!pmk@mimsy.umd.edu (Paul M. Koloc) Organization: Prometheus II, Ltd. Subject: Re: Interstellar travel References: <13.2770D2C9@egsgate.fidonet.org>, <3034@mentor.cc.purdue.edu>, <1990Dec29.070522.21334@zoo.toronto.edu> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In article <1990Dec29.070522.21334@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: >In article <3034@mentor.cc.purdue.edu> f3w@mentor.cc.purdue.edu (Mark Gellis) writes: >>... [fusion drives] It may be that the technology is simply too far in >>the future, but people seem to drool over matter-antimatter, or >>solar sails, but never talk about the possibilities of fusion >>for interplanetary travel. Any comments? >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, and He3 is almost impossible to find or make in the quantities >needed for large-scale high-performance rocketry. (Terrestrial power needs >negligible amounts by comparison.) We may have just such a spheroidal approach to fusion. Initially, the moon has a sufficient supply of (3^)He to run trawlers to seine it from the exosphere of Jupiter. The likely neutron output from a refined D-3^He reactor would be about two percent. Further, the neutron energy per reaction is not nearly as ripping as that from the D-T reaction. For our aneutronic generator approach, this reaction is far more tolerable since it would be trapped in an extremely dense liquid density gas blanket. It is certainly, a better situation than the current solid vacuum wall mag approaches of the DoE ... ah, approach of .. Until we find out otherwise, "p-11^B" looks like the ideal aneutronic (neutronless) burning fuel. +---------------------------------------------------------+**********+ | +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: 29 Dec 90 15:34:12 GMT From: rochester!dietz@rutgers.edu (Paul Dietz) Organization: University of Rochester Computer Science Dept Subject: Re: Interstellar travel References: <13.2770D2C9@egsgate.fidonet.org>, <3034@mentor.cc.purdue.edu>, <1990Dec29.070522.21334@zoo.toronto.edu> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In article <1990Dec29.070522.21334@zoo.toronto.edu> henry@zoo.toronto.edu (Henry 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 [...] But antimatter reactions also produce considerable neutral radiation. Reaction of hydrogen and antihydrogen produces neutral pions (which decay immediately to very energetic photons). The electrons and positrons present also react to make gammas. More importantly, if the antiprotons are annihilated in higher nuclei, the reaction will produce energetic nuclear fragments, including neutrons. Finally, if the charged pions are used to directly heat ordinary matter, they will cause other nuclear reactions, including the production of nuclear fragments and the direct reaction with protons to make neutrons. 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? Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 30 Dec 90 01:13:46 GMT From: mcsun!ukc!axion!phoebe!sjeyasin@uunet.uu.net (swaraj jeyasingh) Organization: British Telecom Research Labs Subject: Space News from Flight Int. for Dec90 Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu Many thanks to those who replied to my posting and confirmed that they were receiving me loud and clear. Obviously I neednt have doubted. Anyway, here is a summary of space related news culled from Flight International during December. I am only posting news which I think would not have been covered by other reports (e.g Henry Spencer on AWST). ESA denies that it will quit the ISS effort, despite a delay of at least *5* years for the launch of its Columbus attached pressurised module. (Delay due to redesign of Fred). According to Roget Elaerts of ESA, they are "closely participating with NASA on the restructuring exercise". Should Fred be cancelled, Europe would stil be free to concentrate on a Columbus Free Flyer to be launched on Ariane 5 in late 1990s. An independant, man tended European space base may also be considered by ESA as a precursor to a space station.Such a move would boost the chances of the Hermes space shuttle winning the ESA's approval. Also mention of first flight of the Ariane 42P model in November, launching 2 US comms sats. 42P has two strap on solids. Next Ariane launch due in Jan. Report on RAE (Royal Aerospace Establishment, UK) plans to develop a Space technology Research Vehicle (STRV) to investigate the in orbit performance of several new space technologies. Weighing 50kg, it will carry eight experiments researching technologies aimed at improving the performance, life and cost-effectiveness of future spacecraft. The STRV mission will address three major hazards: radiation damage to solar cells and microelectronics, electronic anomalies and other damage to comms satellites caused by electrostatic charges and arcing at high altitudes; and surface corrosion of Earth observation spacecraft by atomic oxygen at low altitudes. STRV will be carried as an auxiliary payload on an Ariane 4 commercial comms launch. It will traverse the earths radiation belts at GTO 4 times a day, enabling accelerated radiation tests to be carried out. Soviet Ministry of Defence has undertaken its first commercial spacecraft launch. The Gorizont geostationary comms sat launched from Baikonur on Proton booster on Nov23 was undertaken for the Russian Federation (RSFSR). The RSFSR's Ministry of Communications and Information Technology will pay R100 million ($176) for what will eventually be a three sat system. Nasa doctors at JSC develop drug to cure space sickness. Am injection of promethezine administered after the onset of symptoms has shown a mrked decrease in the severity of the problem. It has been used 14 times on shuttle flights since Sep 1988. Previously they had oral doses of scopolamine (!) and dextroamphetamine but the absorption of these in weightless conditions is unpredictable. The Soviet Union is to resume Zenit booster launches early in 1991 after maintenance work on the second launch pad at Baikonur is complete. The Oct 4 Zenit launch failure destroyed Launch pad one. That explosion has been attributed to Zenits RD-170 first stage engine. It is regarded as random and not a sufficient reason to stop launches for a lengthy investigation. Indonesia is considering using China's Long March booster to launch its Palapa satellites. This was announced during the Indonesian presidents trip to China. Also raised the possibility of cooperation in developing rocket technology for use in Indonesia's own space program. The Long March launch is expected to be about $17m cheaper than a shuttle launch. AEA Technology, the commercial arm of the UK Atomic Energy Authority, plans to develop an upper stage for small low cost satellites to be propelled by an ion-thruster. Called Argos, the upper stage is being designed for launch on Hercules/Orbital Sciences Pegasus, to place 300kg spacecraft into a 400-2000km high orbits. Propulsion would be provided by the UK10 ion thruster system. Argos uses xenon propellent and offers exhaust velocities, 10 times higher than convetional chemical rockets (that is VELOCITY not THRUST). After delivery by Pegasus into iniial orbit, the thruster will manoeuvere the payload into its final orbit over several months.A UK10 thruster is scheduled to fly on the ESA's Artemis technolgy demonstrator satellite in 1993/94, to provide station keeping. Lockheed is bidding to supply heatshields to the Italian Space Agency's CARINA recoverable capsule. This 530kg spacecraft is being developed by Aeritalia to carry microgravity payloads into LEO. It will be launched into 300-400km high orbit by a version of the LTV Scout from the Italian run San Marco platform off the coast of Kenya. Lockheed is proposing to use the same insulatiom material used on some parts of the Shuttle. Israel Aircrfat Industries says that it will continue its efforts to enter the civil space launch market with versions of the Shavit booster. It has dropped out of NASA's commercial experimental transporter competition, aimed at selecting a medium class civil booster. Shavit is variant of the Israeli ballistic missile, Jericho. A Briton may yet make it into space in May 1991. The Mir-Juno project which was threatened with cancellation due to lack of finance, will now take place it seems - on a fly now pay later deal. (All other international guest cosomonauts have had to pay first.) The British astronaut chosen will be announced on Jan 15th. Two, a male and a female, are currently in tarining in Star City. Fianlly, here are the space questions from the annual Christmas Quiz: 1> Which Ferdinand went to Venus 2) Which Edwin needs some specs 3) Who are the two "Gennadis" 4) What suffered from unofficial leaks 5) Which Chinese booster flew for the first time in 1990 and which Soviet rocket did not reach its zenith. 6) Name the oldest man in space and the newest 7) What made an unexpected arrival at Kennedy 8) Which satellite operating organisations now operate their own satellites Answers next time Thats all folks for 1990. Have a Happy New Year ! Swaraj Jeyasingh sjeyasin@axion.bt.co.uk British Telecom Research Labs England. The above is in no way connected with my employer. I am not employed by Flight International either ------------------------------ Return-path: X-Andrew-Authenticated-as: 0;andrew.cmu.edu;Network-Mail Date: 29 Dec 90 07:48:20 GMT From: news-server.csri.toronto.edu!utzoo!henry@rutgers.edu (Henry Spencer) Organization: U of Toronto Zoology Subject: pure oxygen and spacecraft fire safety References: <788@npdiss1.StPaul.NCR.COM>, <1990Dec28.212625.10995@zoo.toronto.edu>, <1990Dec29.023849.7085@nuchat.sccsi.com> Sender: space-request@andrew.cmu.edu To: space@andrew.cmu.edu In article <1990Dec29.023849.7085@nuchat.sccsi.com> steve@nuchat.sccsi.com (Steve Nuchia) writes: >There was a deeper error behind the failure to recognize 1 atm of O2 >as a hazard. Prior to the fire the official fire prevention philosophy >was to have no ignition sources. Since it was official policy that >there be no ignition sources on board, there was not very much thought >given to what might happen if there was a fire. Actually, not true. Fire *in flight* was considered at great length (source: Frank Borman's testimony to Congress as a member of the fire investigation board), and avoidance of flammable and smoke-producing materials when practical was definitely policy. (There is a complaint on record just a few weeks before the fire that eliminating hazardous materials from the cabin was proving more difficult than it had been on Mercury and Gemini.) And the KSC safety people had given quite a bit of attention to pad fires and escape from same. However, Steve is correct that the basic approach was to avoid ignition sources, and containing a fire was second priority. (This is, after all, the normal and quite successful approach elsewhere.) There were still a lot of flammables in the cabin, since tradeoffs tended to weight other issues more heavily. And many things that would pass a 3psi oxygen test would flunk a 15psi oxygen test; in fact, NASA eventually abandoned making the cabin proof against a 15psi-oxygen fire -- it was virtually impossible -- and settled for a mixed-gas atmosphere until mid-ascent. In 3psi oxygen, the fire probably would not have been serious, and the limited precautions that had been taken might well have proved adequate. At the very least, it would probably have spread slowly enough to be coped with -- what took the KSC safety people by surprise was not the possibility of a spacecraft fire (always non-zero with experimental hardware) but the ferocious intensity and near-instantaneous spread. (JSC basically assumed that fires were impossible, but KSC did not.) As Steve describes, the revised approach assumes the presence of an ignition source -- probably overly paranoid if spaceflight ever becomes routine, but realistic for semi-experimental vehicles that are constantly changing -- and insists that a fire must go out by itself when started. -- "The average pointer, statistically, |Henry Spencer at U of Toronto Zoology points somewhere in X." -Hugh Redelmeier| henry@zoo.toronto.edu utzoo!henry ------------------------------ End of SPACE Digest V13 #013 *******************