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, 3 Dec 1990 02:22:07 -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, 3 Dec 1990 02:21:32 -0500 (EST) Subject: SPACE Digest V12 #615 SPACE Digest Volume 12 : Issue 615 Today's Topics: NASA Headline News for 11/28/90 (Forwarded) Radiation on LLNL (was: ELV Support...) Re: Astro-2 Re: Translunar/interplanetary shuttle? Re: $$/pound of Freedom vs LLNL (was: ELV Support...) Re: Photon engine Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription notices, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: 30 Nov 90 07:25:13 GMT From: trident.arc.nasa.gov!yee@ames.arc.nasa.gov (Peter E. Yee) Subject: NASA Headline News for 11/28/90 (Forwarded) Headline News Internal Communications Branch (P-2) NASA Headquarters Headquarters Wednesday, November 28, 1990 Audio Service: 202/755-1788 1788 This is NASA Headline News for Wednesday, November 28, 1990 NASA flight operations managers yesterday announced Dec. 2, 1990, as the launch date for the Columbia STS-35 Astro-1 mission. The launch window opens at 1:28 am on Dec. 2 and extends for two-and-a-half hours until 3:58 am EST. The launch date was selected following completion of the STS-35 Flight Readiness Review. Shuttle director Robert Crippen noted "the Shuttle team has worked very hard to get Columbia ready to fly. With the hydrogen leak resolved, we are ready to end the year with the Astro-1 mission." Aft doors are scheduled to be installed in their flight configuration on Columbia today. Final argon servicing of the Broad Band X-ray Telescope is scheduled to occur tomorrow, following which, Columbia's payload bay will be closed out and the bay doors closed. Turnaround processing of Discovery and Atlantis are continuing on schedule. * * * * * * * * * * * * * * * * * * * * * * * * * * A capacity crowd is expected tonight at the NACA-NASA 75th Anniversary celebration at the National Air and Space Museum. Featured speakers will include Adm. Truly, Gen. Thomas Stafford, Scott Crossfield and David Lewis. A special multi-media presentation will provide an overview of the past eight decades of flight. * * * * * * * * * * * * * * * * * * * * * * * * * * The Technology 2000 technology transfer conference continues through this evening at the Washington Hilton. Some 2,000 are participating in this two-day symposium. J. R. Thompson was the awards dinner speaker last night and presented awards of excellence to 15 organizations and a special Lifetime Achievement Award to John Samos of the Langley Research Center Technology Utilization office. * * * * * * * * * * * * * * * * * * * * * * * * * * Dr. Lew Allen, Chairman of the Hubble Space Telescope Investigation Board, reported to the press yesterday on the results of his team's analysis. The executive summary of the investigation report says "reliance on a single test method was a process which was clearly vulnerable to simple error. Such errors had been seen in other telescope programs, yet no independent tests were planned, although some simple tests to protect against major error were considered and rejected. During the critical time period, there was great concern about cost and schedule, which further inhibited consideration of independent tests." * * * * * * * * * * * * * * * * * * * * * * * * * * A Galileo press conference will be held at the Jet Propulsion Laboratory tomorrow, Nov. 29, at 1:00 pm EST, to discuss recently returned data acquired by the spacecraft during its flyby of Venus last February. The present spacecraft status and plans for the Earth gravity assist flyby on Dec. 8 will also be discussed. Participants include: William O'Neil, Galileo project manager; Dr. Torrance Johnson, Galileo project scientist; and key members of the science team. The press briefing will be carried on NASA Select TV. NASA helps celebrate American Indian Heritage Month tomorrow in the Headquarters auditorium with a ceremony featuring Wilma Mankiller, Principal Chief of the Cherokee nation of Oklahoma, and cultural entertainment as well as food tasting. An exhibition of Native American artifacts will also be on display. The celebration performances will be from 2:00 to 2:30 pm. Here's the broadcast schedule for Public Affairs events on NASA Select TV. All times are Eastern. **indicates a live program. Wednesday, 11/28/90 1:15 pm **Magellan-at-Venus report from Jet Propulsion Laboratory. 4:00 pm Augustine Committee on the Future of the U.S. Space Program hearing (replay from Nov. 19). Thursday, 11/29/90 11:30 am NASA Update will be transmitted. 1:00 pm **Galileo Venus flyby and Earth flyby press briefing from JPL. All events and times may change without notice. This report is filed daily, Monday through Friday, at 12:00 pm, EST. It is a service of Internal Communications Branch at NASA Headquarters. Contact: CREDMOND on NASAmail or at 202/453-8425. NASA Select TV: Satcom F2R, Transponder 13, C-Band, 72 degrees West Longitude, Audio 6.8, Frequency 3960 MHz. ------------------------------ Date: Fri, 30 Nov 90 09:33:38 -0500 From: "Allen W. Sherzer" Subject: Radiation on LLNL (was: ELV Support...) Newsgroups: sci.space Cc: In article <2812@polari.UUCP>: ++Crews do not *have* t+o be rotated>+ every 90 days, which reduces ++transport (and thus life-cycle) costs. +Wrong. Crews must be rotated every 90 days to limit exposure to ionizing +radiation. Shieliding is to be provided to permit a maximum safe stay of one +year based on allowable accumulated dose. We have already covered this Mr. Radley. The yearly radiation dose on a LLNL type station is LESS than the dose for 90 days on Freedom (one things DoE labs know a *LOT* about is radiation). +LLNL at a higher altitude will have a more severe radiation +environment than Freedom. Which is why they orbit at a lower altitude. Before you bring up the issue of fuel for boosting, I remind you (we already went through this as well) that it's already included in their budgets. +Also, the shielding capability of LLNL's non- +metallic structure is much less than Freedoms aluminum modules. Using non-metalic materials minimized secondary effects. To show how much they have thought about this issue, you should realize that they have, as part of the design, a 'storm shelter' built in. During periods of high solar activity, they can go to a module with water shielding to wait it out. In this sense, they are far safer than Freedom. Allen -- +---------------------------------------------------------------------------+ |Allen W. Sherzer| I had a guaranteed military sale with ED-209. Renovation | | aws@iti.org | programs, spare parts for 25 years. Who cares if it | | | works or not? - Dick Jones, VP OCP Security Concepts | ------------------------------ Date: 30 Nov 90 05:03:31 GMT From: dftsrv!heawk1!kaa@ames.arc.nasa.gov (Keith Arnaud) Subject: Re: Astro-2 In <1176@inews.intel.com> sstrazdu@hopi.intel.com (Stephen Strazdus) writes: >Is there an Astro-2 flight in the works for the Space Shuttle? I would >imagine the instruments used in Astro-1 are not going to be thrown away >after a 10 day mission. Are they? Are the second mission's plans >very dependent on the first mission? >-- >-------------------------------------------------------------------------------- >Steve Strazdus | sstrazdu@hopi.intel.com | Insert your favorite .sig here. The original plan (circa 1984, I think) was for Astro-1 to be followed by Astro-2 and Astro-3 however there is no followup flight currently on the Shuttle manifest. The instruments will certainly not be thrown away - we need them to check the calibration. Keith Arnaud Waiting for Astro kaa@ros2.gsfc.nasa.gov -- ------------------------------------------------------------------ | Keith Arnaud | internet : kaa@heasfs.gsfc.nasa.gov| | Code 666/Univ.Md. | span : lheavx::arnaud | | NASA/GSFC | bitnet : arnaud@rosatbit | ------------------------------ Date: 30 Nov 90 17:55:23 GMT From: att!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!ub!ubvmsd.cc.buffalo.edu!v071pzp4@ucbvax.Berkeley.EDU (Craig L Cole) Subject: Re: Translunar/interplanetary shuttle? In article <7633@eos.arc.nasa.gov>, millard@eos.arc.nasa.gov (Millard Edgerton) writes... >If the engines(mains) are not restartable, HOW DO THEY FIRE TO DE-ORBIT? > >THINK ABOUT IT! The main engines don't. The two medium-size engines on the back fire. They're called the Oribtal-Maneuvering-System (OMS) engines. Craig Cole V071PZP4@UBVMS.BITNET V071PZP4@UBVMS.CC.BUFFALO.EDU ------------------------------ Date: Fri, 30 Nov 90 20:55:07 -0500 From: "Allen W. Sherzer" Subject: Re: $$/pound of Freedom vs LLNL (was: ELV Support...) Newsgroups: sci.space Cc: In article <7534@hub.ucsb.edu>: >>>Once it [LLNL] is "fleshed out" its dollar per pound cost to >>>weight ratio will be about the same as Freedom. >>Would you mind justifying this a bit better? >Certainly. First of all, you haven't given much justification. Without stating the weight and cost of both structures I don't see how you can expect to consider your staement justified. >1) - without using numbers admittedly, but the lighter hull materials >of LLNL only account for a small portion of the overall vehicle. If memory serves, the entire LLNL station minus crew and consumables weighs *LESS* then just the truss of the current Freedom configureation. That off the bat gives it a big head start. LLNL can add all the rest (science module) for the same weight as Freedom and still come in way ahead. >Copper wire on LLNL will weight the same as it does on Freedom, for example. Yes it does. On the other hand, since LLNL is bought outside the FAR's (unlike Freedom) it costs a hell of a lot less. When computing cost/pound that counts. Not only is LLNL a lot lighter for the same capability, it costs less as well. >2) - the lightweight material of LLNL advantage is largely negated >by being much bigger in volume than the Freedom habitable areas, >because it spins. Spinning has nothing to do with it. As to the volume, why not? The marginal cost of additional volume is so cheap (unlike Freedom) there is little penalty. >A nonspinning smaller LLNL would be more competitive. Depends. If you want to reduce costs by stretching out rotation, the answer is a clear no. >Nobody has responded to my point about long term radiation doses, I assume you have seen my reply so I won't repeat it here. Allen -- +---------------------------------------------------------------------------+ |Allen W. Sherzer| I had a guaranteed military sale with ED-209. Renovation | | aws@iti.org | programs, spare parts for 25 years. Who cares if it | | | works or not? - Dick Jones, VP OCP Security Concepts | ------------------------------ Date: Fri, 30 Nov 90 21:01:36 EST From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. Subject: Re: Photon engine >From: mcgill-vision!thunder.mcrcim.mcgill.edu!clyde.concordia.ca!news-server.csri.toronto.edu!utgpu!utzoo!henry@bloom-beacon.mit.edu (Henry Spencer) >Subject: Re: Photon engine >In article <4948@bwdls58.UUCP> hwt@bwdlh490.BNR.CA (Henry Troup) writes: >...Shuttle power output at launch is 15-20 gigawatts, I believe. >However, the inequality you propose doesn't work. There is no unique >answer to the question of power output for a given mass at a given >acceleration. It depends on the exhaust velocity. >A 100T ship at 1G (call it 10 m/s^2) requires a thrust of 1MN. Thrust >is mass flow times exhaust velocity, by conservation of momentum. At >an exhaust velocity of 3e8 m/s, naively (ignoring relativistic issues), >we need 3.3e-3 kg/s of mass flow. Kinetic energy over time of that flow, >with respect to the rocket, naively, is 0.5*mass_flow*ve^2, or about >15e13 W. Call it 150 terawatts. I'd have to hit the books to sort out >the non-naive version of this, but it probably won't differ by more than >a small integer, and it might even be the same. >From various sources, the momentum of a photon is h / wavelength, where h is Planck's Constant, 6.625E-34 kg*m^2/s. From this it can be derived that the force of a directed beam of photons is equal to power / c. Your number of 3.3E-3 kg/s is the mass-equivalent of the power of the necessary photon beam, but using the non-naive formula E = m * c^2, the power would be ~3E14 W = 300 terawatts. Some other interesting general formulae to compare photon drives and matter reaction mass drives: Drive momentum xfer / energy ----- ---------------------- photon 1 / c matter 2 / v which illustrates that a matter drive will always give more than twice as much thrust per joule than a photon drive (since v < c). Also, a matter drive uses energy more efficiently when exhaust velocity is lower, which means that it is always in your best interest to use as much reaction mass as you have available. Pushing against a large celestial body (i.e. linear launcher) is particularly efficient. Note that the force of a photon drive depends only on the power radiated - wavelength is irrelevant. I can think of one exception to this rule. If you use a "pure" energy source such as antimatter, and if you have a certain mass budget for fuel plus reaction mass, then you get marginally more thrust by dedicating the whole mass to equal quantities of matter and antimatter, to be blasted out as photons, than by setting aside some additional normal matter as reaction mass. If I calculated correctly, setting aside one nth of the fuel mass as reaction mass results in sqrt((n^2 - 1) / n^2)) as much thrust. For instance, 5 kg of matter and 5 kg of antimatter for a pure photon drive should give about 3E9 Newton-seconds of thrust, while 5.5 kg of matter with 4.5 kg antimatter would only provide about 99.5% as much thrust, and 7.5 kg matter with 2.5 kg antimatter would only give about 87% as much. If you ever find a really good sale on antimatter, you should keep this in mind. :-) In the meantime, antimatter being many times as expensive as matter, most people would choose a mix with much more reaction mass than antimatter. >I don't have numbers handy for the whole species or total power, but the >electrical power generating capacity of the US is circa 1 terawatt, I think. >Handling 150TW would be, um, a challenge. For example, assume an efficiency >of 50%. (That's awfully good for lasers, which are inherently pretty lossy >devices.) That means our total power output actually has to be 300TW, and >the missing 150TW comes out as heat. We have to get rid of that heat... >somehow. The only long-term answer is radiators, but they're big and heavy. As Christopher Neufeld pointed out, if the heat can be preferentially radiated in a certain direction, for instance from a big flat disk with an insulated back, then it can act as part of the photon drive, providing about half as much thrust as a directed beam. This brings up the option I mentioned, which is using the radiator as the thruster, and eliminating the expense and maintenance of a laser. In the worst case, a 100% efficient laser will only give twice the thrust of a radiator per watt supplied. A 50% efficient laser would only provide a 50% increase, and so on. Since a driving radiator isn't really cooling anything, it can run hotter, which has important implications for the size of radiator needed. In the example given, the thrust can be supplied by a 600 TW radiator, or by a 200 TW laser and a 200 TW radiator. Assume the driving radiator can be run at 3500K (a little below the melting point of thorium oxide), that the laser can be run at 2500K, and that the radiators act approximately like black bodies. I believe radiated energy per unit time is described by the formula E = k * (T^4 - T0^4), where T0 is the ambient blackbody temperature (essentially zero), and k is the Stefan-Boltzmann constant, 5.6696E-8 W / meter^2 * Kelvin^4. The radiator-drive therefore requires a disk of only 9.5 km diameter, while the laser-radiator drive requires a 10.7 km diameter disk, showing that the radiator-drive system would be somewhat more practical on a 100000 kg , 1G photon ship. :-) If the laser can not operate at over 1000K, then its directional radiator must be about 67 km in diameter. Conclusion: for just about any conceivable application, a photon drive craft with a self-contained power source is a very very very bad choice, but if you just have to have one, a simple radiator drive is probably better than a laser. Again, this does not apply to systems in which the laser is just a way of getting power to the craft from a remote source (i.e. launcher systems), and to solar sails, in which the energy is obtained free from the sun, and from which you get up to double the kick from each photon if you use a reflective sail. >"I'm not sure it's possible | Henry Spencer at U of Toronto Zoology >to explain how X works." | henry@zoo.toronto.edu utzoo!henry John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ End of SPACE Digest V12 #615 *******************