Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from hogtown.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) ID ; Fri, 7 Jun 91 01:31:28 -0400 (EDT) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Fri, 7 Jun 91 01:31:18 -0400 (EDT) Subject: SPACE Digest V13 #610 SPACE Digest Volume 13 : Issue 610 Today's Topics: Re: Dimensions of Shuttle bay wanted. Re: lifeboats Re: SPACE station or NOTHING!!!!! Calculating delta-V Re: Budget Numbers Wanted Re: New Subject--Solar Collectors (Dual Use) Re: Rational next station design process Re: Laser launchers (really microwave launchers) 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 ---------------------------------------------------------------------- Date: 21 May 91 23:41:00 GMT From: swrinde!zaphod.mps.ohio-state.edu!think.com!spool.mu.edu!cs.umn.edu!kksys!wd0gol!newave!john@ucsd.edu (John A. Weeks III) Subject: Re: Dimensions of Shuttle bay wanted. In <5921@mindlink.bc.ca> Ralph_Busch@mindlink.bc.ca (Ralph Busch) writes: > I'm in need for the dimensions of the space shuttle bay. Actually, if anyone > has figures on the size of canisters that the Space Station Freedom was going > to be made of, that would be really handy! I do not have the exact numbers. Since I cannot visualize sizes based on dimensions very well, I use a couple of ball-park analogies. The orbitor is about the size of a 727. The cargo bay is about 45' long and about 15' in diameter. This is about the size of 2 semi truck trailers parked side by side. The payload weight is about the same as a fully loaded semi truck. > Also, if you have the figures for the soviet shuttle, that'd be nice, but not > necessary. If one were to say about the same as the NASA Shuttle, you would probably not be too far off. -john- -- ============================================================================= John A. Weeks III (612) 942-6969 john@newave.mn.org NeWave Communications, Ltd. ...uunet!tcnet!newave!john ------------------------------ Date: 22 May 91 15:41:08 GMT From: sdd.hp.com!caen!ox.com!fmsrl7!wreck@ucsd.edu (Ron Carter) Subject: Re: lifeboats In article <1991May20.184528.19548@agate.berkeley.edu> gwh@tornado.Berkeley.EDU (George William Herbert) writes: >You're forgetting something... all the orbital maneuvering (reaction control >system etc) was on the SM if I remember correctly. I'm not sure how happy the >astronauts would be about dropping hydrazine in their capsule for RCS >purposes. The CM had limited reaction control capabilities. I've seen the Apollo 9 CM a few times; there are most definitely RCS nozzles built flush into the skin down near the heat shield. The CM most definitely carried fuel for these thrusters; the hydrazine (or whatever) problem is old hat. However, these jets won't work for orbital maneuvering for several reasons. 1.) They are designed to maintain spacecraft attitude during re-entry. Thus, they can only roll, pitch and yaw the spacecraft. 2.) Thrusters to translate the spacecraft in the X, Y and (important for docking) Z axes are absent. 3.) The rotational thrusters aren't balanced. (They didn't need to be.) A little translational push from a rotation is of no consequence during re-entry, but it is a serious problem when docking. This means that the CM cannot be used as a crew vehicle or lifeboat without either modification or an SM-equivalent. It can't dock without assistance, nor push away from a space station either. These capabilities are required for either crew rotation or lifeboat operations. Considering our progress in ultra-low-power electronics (for avionics), high-strength materials (for oxygen tanks), powerful batteries, and other technologies, it should not be difficult to design a CM-equivalent which can be shipped up to a space station, dock with it, and then either work as a crew transport or lifeboat. It might be possible to build one into a CM-shell and omit the SM, but I believe that it will be necessary to get somewhat fancy with the thruster configuration to achieve the necessary capabilities. ------------------------------ Date: 23 May 91 18:46:56 GMT From: aio!vf.jsc.nasa.gov!kent@eos.arc.nasa.gov Subject: Re: SPACE station or NOTHING!!!!! > > Well, if we go ahead and build the station as currently conceived, > it'll just be that much harder for me to convince my professors who I guess they feel as if the the S.S. Freedom is competing for dollars with them. Do they remember all the data on the sun we got from skylab? > > With the astronomical pricetag for the shuttle, he doesn't believe > cheap spaceflight is possible. > For the first shot a reuseable vehicle, the shuttle does quite well. Its launch cost is less than the Saturn V. -- Mike Kent - Lockheed Engineering and Sciences Company at NASA JSC 2400 NASA Rd One, Houston, TX 77058 (713) 483-3791 KENT@vf.jsc.nasa.gov ------------------------------ Date: 23 May 91 23:06:32 GMT From: agate!spool.mu.edu!samsung!munnari.oz.au!yoyo.aarnet.edu.au!sirius.ucs.adelaide.edu.au!levels!etssp@ucbvax.Berkeley.EDU Subject: Calculating delta-V In calculating the delta-V (change in velocity) that a rocket stage imparts one needs to multiply the engines Specific Impulse (if it is given in seconds) by the acceleration of gravity at Earth's surface. My question is what is the standard (if there is one) that rocket scientists use for g? In the metric system, the approximation for g that we used in high school is 9.81 m/s^2. However, my little Casio calculator table gives the (Standard) g as 9.80665 m/s^2. If your engine has a 450 s SI and the propellant mass to empty mass is equal to 3, you obtain from the rocket equation a delta-V of 6120 m/s for g = 9.81 m/s^2, 6114 m/s for g = 9.80 m/s^2, or 6118 m/s for the Standard g. A rocket engine already has errors in what the actual the value of SI is and if one is uncertain as to what g to use this will add more errors into what the actual delta-V will be. As can be seen, errors of between +2 m/s and -4 m/s can occur simply because of the uncertainty of g. If there is a standard g that rocket scientists use, this would remove this uncertainty. A good solution is to give SI as the ratio of thrust (in Newtons) to propellant consumption (in kg/s). This will give SI in m/s and there is no need to multiply g in working out delta-V. In the imperial system thrust is measured in pounds-force, i.e., one pound-force is the force required to accelerate one pound by one g. We then get into the same problem of what g to use. The metric system defines one Newton as the force required to accelerate one kg by one one m/s^2. (Using g = 9.80665 m/s^2 and 1 lb = 0.453592 kg, 1 lbf = 4.44822 N). -- Steven Pietrobon, Australian Space Centre for Signal Processing School of Electronic Engineering, University of South Australia The Levels, SA 5095, Australia. steven@rex.sait.edu.au ------------------------------ Date: 22 May 91 18:17:36 GMT From: swrinde!zaphod.mps.ohio-state.edu!usc!nic.csu.net!csun.edu!corona!swalton@ucsd.edu (Stephen Walton) Subject: Re: Budget Numbers Wanted [This is exactly as I received it via e-mail. Some hard numbers are clearly needed in this discussion.] Statement of the Honorable Bob Traxler, Chairman, VA, HUD, and Independent Agencies Subcommittee, House Appropriations Committee -- May 15, 1991 "Today's action of the VA-HUD and Independent Agencies Appropriations Subcommittee, in accepting my recommendations to terminate funding for the development of NASA's Space Station Freedom, reflects the fact that our Federal Government's budgeting has hit a dead end. We simply can no longer afford huge new projects, with huge price tags, while trying to maintain services that the American people expect to be provided. The Fiscal Year 1993 scenario is also dismal. Under last year's budget agreement, the Subcommittee does not expect any increase beyond the percentages in this year's allocation: 5.4% in budget authority and 5.6% in outlays. Furthermore, prior-year appropriations will produce increased outlays that will adversely impact the Subcommittee's ability to fund the various agencies within its jurisdiction. In brief, if we cannot afford to fund the space station this year, there is no way that we would be able to fund it next year. The budget crunch this year requires us to terminate development of the space station; if we stay on the same budget course, we will soon be faced with the prospect -- even the necessity -- of making more awful decisions in the years ahead. The VA-HUD Subcommittee funds a range of important human needs programs: VA hospitals, housing for the poorest in our society, environmental clean-up programs on which the health of ourselves and our planet depend, education and basic research programs on which our future depends, and, yes, our civilian space program with which we address another basic human need -- the need to explore. In terminating funding for the space station, we have been able to provide nearly full funding for other space science research efforts and we have provided full funding for the research and education programs of the National Science Foundation. We have provided a much needed increase for the VA hospital system, which I wish could have been more, in order to help keep our Nation's medical services for veterans in operation. We have provided generous funding for our nation's environmental programs. Finally, we have maintained our nation's commitment to housing for the poor and homeless." Traxler budget WITHOUT / WITH SSF =============================================== RESEARCH & DEVELOPMENT Station -- Out Station -- In Space Station -1,928,900,000 Space Flight Capability Development New Launch Systems --- -175,000,000 General Reduction -10,000,000 -50,000,000 Space Science and Applications General Reduction --- 35,000,000 SETI --- -7,000,000 SIRTF & OSL's Phase B's --- -25,000,000 LIFESAT -10,000,000 -15,000,000 Life Science (Space Station) -25,000,000 -25,000,000 AXAF --- -50,000,000 EOS --- -75,000,000 CRAF --- -45,000,000 LANDSAT +5,000,000 --- Microgravity -11,500,000 --- Remotely Piloted Aircraft -5,000,000 -5,000,000 SAR +10,000,000 --- Classroom of the Future +1,500,000 --- Information Systems -5,000,000 -5,000,000 COMMERCIAL PROGRAMS COMMERCIAL APPL/ENHANCEMENTS -5,000,000 -5,000,000 COMMERCIAL TRANSPORTATION -5,000,000 -25,000,000 Aeronautics and Space Technology Aeronautics Res. Gen Reduction --- -10,000,000 NASP --- -25,000,000 Exploration Technology -10,000,000 -52,000,000 Space Automation and Robotics --- -50,000,000 Exploration Mission Studies -5,000,000 -15,000,000 General Reduction (Space Tech) --- -25,000,000 Academic Programs --- -9,000,000 General R&D Reduction --- -25,000,000 Total NASA R&D -2,003,900,000 -753,000,000 SPACE FLIGHT Space Tranp.Prod.&Operations General Reduction --- -200,000,000 Assured Shuttle Capability --- -75,000,000 Structral Spares --- -75,000,000 ASRM +175,000,000 +175,000,000 Tracking -25,000,000 -50,000,000 Expendable Launch Vehicles TDRSS LAUNCH VEHICLE -39,000,000 -39,000,000 Titan IV Craf/Cassini -35,000,000 -50,000,000 Mobile Satellite -24,000,000 -24,000,000 General Reduction -10,000,000 -10,000,000 Total NASA Spaceflight +42,000,000 -348,000,000 R&PM Gen.Reduct.Fund Source III -13,000,000 -75,000,000 Gen.Reduct.Fund Source I&II -12,000,000 -25,000,000 Total R&PM -25,000,000 -100,000,000 CONSTRUCTION ASRM (to Spaceflight Acct.) -50,000,000 -50,000,000 Space Station Proc. Facil. -35,000,000 --- CEISIN Facility +3,400,000 --- TOTAL NASA -2,068,500,000 -1,251,000,000 -- Stephen Walton, Dept. of Physics & Astronomy, Cal State Univ. Northridge "Lately it occurs to me/What a long, strange trip it's been" ------------------------------ Date: 22 May 91 19:18:06 GMT From: agate!spool.mu.edu!news.uu.net!igor!rutabaga!wab@ucbvax.Berkeley.EDU (Bill Baker) Subject: Re: New Subject--Solar Collectors (Dual Use) In article <384.2838ECB2@nss.FIDONET.ORG> Paul.Blase@nss.FIDONET.ORG (Paul Blase) writes: [...] >There is a limit, but in general photovoltaic cells operate most efficiently >at very high light levels. This is why many new solar-cell designs use >concentrators (mirrors) to increase the light flux at the cell. The closer >you are to the sun, obviously, the smaller a system you need for a given >amount of light on your cell. [...] >Don't forget that there is another way of producing electricity from >sunlight: dynamic power, aka a steam turbine. I think that it is a >toss up as to which would be cheaper right now. Pardon me if this is a dumb question, but isn't the obvious answer to combine the photovoltaic and thermal transfer methadologies? I've read that people using collectors with photovoltaic cells cool them with water to keep them below the critical temperature. Isn't this wasting heat? Can't you capture the thermally transmitted energy from a PV cell just like any other solar heating collector? I guess the limiting factor is the upper temperature limit of the photovoltaic cells vs. the most efficient operating temperature of a thermal transfer medium. I read that the newest solar thermal plants were heating an oil-based fluid to around 700 degrees F, which seems to be way over the limit for PV cells. Still, couldn't a combined system at least preheat a transfer medium before passing it on to a final heating stage (not necessarily thermal)? ------------------------------ Date: 23 May 91 04:57:00 GMT From: agate!tornado.Berkeley.EDU!gwh@ucbvax.Berkeley.EDU (George William Herbert) Subject: Re: Rational next station design process In article <5955@mindlink.bc.ca> Nick_Janow@mindlink.bc.ca (Nick Janow) writes: >> This isn't how space programs funding is done now... >That's your argument? We should decide to go ahead with a vague project, >_then_ decide the details, like who can/will use it and who might be willing to >pay for the services, just because "that's the way they do it now"? No. I'm doing a specific project with a specific set of missions. The life science/human biology people will use it, as well as a few others 'while we're there'. The government in its infinite (cough) wisdom already funds similar missions/needs, so presumably that's where it will come from. >> The President and VP seem to want Freedom, whatever the cost. >Political advertising is a really poor excuse for an otherwise unrelated >engineering project. >> ) we've already decided how much one is worth. >Really? I thought the project was still undefined, so how could there be a >firm cost to be accepted? The cost projections seem more like tools used for >the current round of budget fighting, with no real meaning beyond that. 'Worth' not 'Cost'. The Executive branch feels it's 'worth' whatever they think it will cost (presumably to some undefined limit above what NASA said it would). Congress has a 'cost' estimate that they think exceeds the 'worth' of the project. Trading off cost and worth is sort of iffy in many cases where the worth is scientific return or something less tangible. -george william herbert gwh@ocf.berkeley.edu ------------------------------ Date: 15 May 91 16:32:03 GMT From: elroy.jpl.nasa.gov!swrinde!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!pitt!nss!Paul.Blase@lll-winken.llnl.gov (Paul Blase) Subject: Re: Laser launchers (really microwave launchers) to: johnsson@cs.chalmers.se (Thomas Johnsson) TJ> I wonder if anyone has considered beaming the power to the TJ> launch vehicle using microwaves instead of a laser. Presumably TJ> power can be converted to microwaves with greater efficiency TJ> than laser light. In the vehicle end, the beamed power could TJ> either heat up a medium direcly, or be converted to electricity TJ> (a lot!) with a rectenna to drive a mass driver. The trouble is the size of the rectenna required. NASA has already built a microwave powered airplane, for long-duration upper atmospheric studies. The thing (unmanned, of course) looks like a cross between a U-2 and an AWACS, the big circular thing being the rectenna --- via Silver Xpress V2.26 [NR] -- Paul Blase - via FidoNet node 1:129/104 UUCP: ...!pitt!nss!Paul.Blase INTERNET: Paul.Blase@nss.FIDONET.ORG ------------------------------ End of SPACE Digest V13 #610 *******************