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) (->ota+space.digests) ID ; Fri, 14 Jun 91 03:15:03 -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, 14 Jun 91 03:14:59 -0400 (EDT) Subject: SPACE Digest V13 #640 SPACE Digest Volume 13 : Issue 640 Today's Topics: Re: The Un-Plan Re: lifeboats Re: lifeboats....ACRV Re: Self-sustaining infrastructures Re: Rational next station design process Re: SR-71 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: 25 May 91 21:20:41 GMT From: sequent!muncher.sequent.com!szabo@uunet.uu.net Subject: Re: The Un-Plan In article jim@pnet01.cts.com (Jim Bowery) writes: >....the actual numbers for >U.S. vs Japanese, public vs private technology R&D funding is: > > R&D Funding Sources > Public Private >Unite States 67% 33% >Japan 22% 78% > >Examples of successesful, low cost, R&D efforts that "meet international >challenges" with the financial risk taken by the private sector: > >Wright Bros., the automobile, the telephone, Spirit of St. Louis, lasers, >the transistor, Seymour Cray/supercomputer (1604 - Cray-3), railroads, >microcomputers, the light bulb, radio, television, electrical generators, >communications satellites, >... >The government has served technology advance best when it: > >... >2) Supported education and scientific (unpatentable) research. >... This is an important point: distinguishing between patentable research, which should be done primarily by private industry, and basic and applied (but unpatentable) scientific research for which the government should provide ample funding. The DoC should have more say in this research than DOE, DoD, or NASA during this era where international competitiveness is more important than defense or raw energy to the existence, growth and well-being of our society. You provide a good legal and scientific definition for distinguishing what should be done by government labs and what should be done by industry. >> * Our sample size of earth-crossing and Jupiter-crossing asteroids and >> comets is increased 1,000-fold, so that we find several small objects >> that can be captured into earth orbit for less than 500 m/s impulse >> delta-V. > > >1)... Even "small" objects that hit the earth from space are exceedingly destructive.... This is an important point that needs to be discussed. Specifically, we need to determine: * What is the maximum size and composition that can be safely fast-aerobraked in Earth's atmosphere. Currently, the Shuttle (c. 100 tons?) does this regularly, over Los Angeles to boot, with little safety concern. Skylab (c. 200 tons?) did this in an uncontrolled manner, and cause some furor but the danger was not overwhelming. Using nuclear power adds another dimension, but fortuneately nuclear power is not needed for capturing material. * What is the maximum size and composition that can be safely gravity-assisted by the Earth. Some major factors: -- What is the ability to correct errors on the incoming spacecraft full of materials -- What is the maximum worst-case destructiveness and its probability that can be tolerated. -- What are the effects of volatile (eg ice) and hard (eg nickel-iron) materials. * What is the maximum size and composition that can safely be slow aerobraked (< 1/100 g) in Earth's upper atmosphere. The rule of thumb I am working with is that up to 1,000 tons of easily crushed volatile materials can be safely fast-aerobraked, and that up to 10,000 tons of such material can be gravity-assisted or slow aerobraked. The figure for hard material such as steel, nickel-iron, or the typical earth-launched spacecraft would be 1,000 tons for well-controlled flyby and 100 tons for well-controlled aerobraking. These are just rules of thumb; the actual figures for reasonable safety should be worked out. Note that _not_ using Earth for gravity assist and/or aerobraking imposes a very large energy cost, typical one or two orders of magnitude, on the cost of returning asteroid materials to LEO. Not using Earth aerobraking also adds to the energy cost of returning lunar materials to LEO. Determining and agreeing to margins that both protect Earth and enhance our ability to develop space is a very important issue. If our ability to detect small and distant comets and asteroids greatly increases, we will be able to detect small Jupiter-crossing asteroids and comet fragments. Using Jupiter and the Moon for gravity assist is a very powerful and safe technique for capturing materials into high Earth orbit. >2) Delta-V isn't the overriding consideration -- round-trip mission >time is. As with airlines, costs are dominated by amortization rates >on the flight equipment. I disagree. "Money-time" is easily computed by the cash flow equation. This can be found in a good business calculator, or start up your nearest spreadsheet. Here is a cash flow analysis for a mission that takes 4 years of round-trip time. For this analysis the $numbers are made up and not important; the relationship between $$ and time is. Let's say it costs $1.5e9 to develop, launch, and set up the equipment. Since this is high-risk, time cost of money is 18%/year. Assume that we must replace $6e8 of machinery every year after the operation is going. Assuming $1.2e9 revenue per year, and an R&D period of 4 years (fairly short for the aerospace industry) the annual cash flow for the mining project will look something like this: -.1 ($1e8) -.2 -.4 -.8 (launch: total development costs $1.5e9) 0; 4 years (round-trip travel & setup time) .6; indefinitely ($12e8 revenue - $6e8 costs: 100% gross margins) Net present value (NPV) of this cash flow at 18% is >$0, which means that if the numbers I pulled out of the air were realistic, it would be a good investment. The annual market/development costs ratio is 12/15. In other words, due to the round-trip travel time and the time cost of money, we need an annual market equal to 80% of the development costs, sustainable at 100% gross margins. If the Fed dropped rates just 3%, we could get by with a market equal to 58% of development costs [n.b. for those who think big budget deficits are OK]. For a two year round trip time we only need a market equal to 46% of development costs to provide an 18% return. The Moon (0 years) needs a 34% market, giving us a money-time ratio of 2.35 between a four-year round trip to an asteroid vs. the Moon at the junk-bond rate of 18%. While the time advantage of the Moon is significant, it is not overwhelming. Using aerobraking, we can get material from asteroid 1982DB, and probably several thousand other as yet undiscovered asteroids, with 9,000 times less fuel than from the Lunar surface. With gravity assist, the ratio is about 100:1. Launch, fuel, tankage, and payload-design constraint costs related to energy constraints dominate for deep-space missions (about 60%). This gives 1982DB a cost advantage of between a factor of 60 and a factor of 5400. These both dwarf the time cost of money ratio of 2.35. Furthermore, asteroids contain a wide variety of materials (refined nickel-iron, water, nitrogen, carbon, etc.) which are much more difficult or impossible to obtain on the Moon. Mining equipment on the Moon will greatly "outweigh", in both mass and development cost, mining equipment on asteroids. There will be an even larger difference between the rock or metal asteroids and comet fragments, since ice mining is much easier than rock or metal mining. That is why the "Un-Plan" shows Encke earth-crossing comet fragments being mined first, although the existence vs. nonexistence of such earth-crossing ice is speculative due to the inadequate state of our exploration of these bodies. >Due to the probability of our achieving economical fusion in the near >future, I seriously doubt SPS will ever be important. We certainly should not _count_ on it, just as we should not count on any other single speculative space industry [microgravity and vacuum manufacturing, platinum-group metals, diamonds, He-3, pharmaceuticals, etc. etc.]. It is important that primary industries -- exports from space to Earth -- be developed, but we can't get ourselves stuck on preconceived notions of which ones will dominate. We need to be ready for another Amgen to come along and spoil our plans. Keep our options open, and keep looking for new options. That's why I called this the "Un-Plan". -- Nick Szabo szabo@sequent.com "If you understand something the first time you see it, you probably knew it already. The more bewildered you are, the more successful the mission was." -- Ed Stone, Voyager space explorer ------------------------------ Date: 25 May 91 14:39:03 GMT From: spool.mu.edu!rex!rouge!dlbres10@decwrl.dec.com (Fraering Philip) Subject: Re: lifeboats Please ignore article . Accident with the posting mechanism, I believe. - Phil ------------------------------ Date: 25 May 91 18:12:54 GMT From: agate!lightning.Berkeley.EDU!fcrary@ucbvax.Berkeley.EDU (Frank Crary) Subject: Re: lifeboats....ACRV In article <1991May23.175300.9590@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: >The other side of this, of course, is that either one is more reliable after >storage for years in orbit than a set of maneuvering engines. If David >can postulate a violently-out-of-control station, I can postulate undetected >equipment failure in the lifeboat. I personally like the solution used by the Soviets: Their "lifeboat" is one of their crew transports, which is keep docked to the station. This way, every time there is a crew rotation, the old "lifeboat" is replaced along with the old crew. As a result, they never have the lifeboat in storage on orbit for "years." Usually it is up there for only 6 months, though I seem to remember that one was up for as long as 9 months. Frank Crary PS: I do agree that a fail-safe emergency mode for undocking is also a very good idea. ------------------------------ Date: 26 May 91 01:13:22 GMT From: news-server.csri.toronto.edu!utzoo!henry@uunet.uu.net (Henry Spencer) Subject: Re: Self-sustaining infrastructures In article <1991May26.002647.22594@agate.berkeley.edu> fcrary@lightning.Berkeley.EDU (Frank Crary) writes: >On this note, I would like to mention that the lifetime of a satellite in >Low Earth orbit is limited by its fuel supply... Well, for those that *have* a fuel supply. A good many, e.g. Hubble, don't. A better way of putting it is that the life of a low-orbit satellite is usually limited by air drag. >... Geostationary satellites (if they can be used >to measure lifetimes NOT limited by fuel consumption) ... Kind of dubious, since their useful lifetime usually *is* limited by fuel. They need it for precision station-keeping. >... As such, being able to refuel a satellite in Low Earth orbit could >as much as triple its lifetime... Being able to reboost it would, in many cases, be just as good as refuelling, and less hassle. Unless it's using fuel for something else, like attitude control, there's little difference between giving it a push and refuelling it so it can give itself a push, except that the latter is more complicated and puts more constraints on the satellite design. Another issue here, by the way, is that satellites fuelled by hydrazine also suffer from slow degradation of the catalysts they use to break it down in their thrusters. So just refuelling them has limits. >... Can anyone comment on the viability of a >for-profit Low Earth orbit infrastructure for the purpose of re-fueling >satellites? Minimal. It's always in the wrong orbit, since no two low-orbit satellites are in exactly the same plane, barring the occasional deliberately-established constellation. Refuelling geostationary comsats would be much more promising. Getting from one side of Clarke orbit to the other is not quick, but it *is* relatively cheap, and there usually is plenty of advance warning that a bird is running low. Of course, you'd have to convince the comsat builders to start providing for refuelling. >Could a unfueled and deactivated satellite be claimed as >salvage, re-fueled, re-activated and sold as salvage? I'm unsure about the legal aspects, but it doesn't seem likely to be very profitable. The low-orbit birds are usually specialized, and often would be of little value to anyone other than their owners. You really want to get contracts for refuelling them *before* they run out. -- "We're thinking about upgrading from | Henry Spencer @ U of Toronto Zoology SunOS 4.1.1 to SunOS 3.5." | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 23 May 91 20:24:42 GMT From: van-bc!rsoft!mindlink!a684@ucbvax.Berkeley.EDU (Nick Janow) Subject: Re: Rational next station design process gwh@headcrash.Berkeley.EDU (George William Herbert) writes: > Again, looking at the needs of long-term human bio research, I can't see any > solution other than doing research on a manned station. I'm open to having my > mind changed, but all the research into bioscience needs that I've done says > 'Station!' all over it 8-) I don't think anyone is denying that some research can't be done without a long-term manned facility. However, there's also a question of time. The research is valuable, but does it have to be done this year? Next year? the year 2000? Could it possibly wait until space engineering can provide better facilities for less cost? Furthermore, are biologists properly prepared for that manned space research. Have they done all the preparatory work and have absolutely nothing more to do until the orbiting facility is ready? I'm not a biologist, but I assume that research into the effects of spin on humans, cell growth in zero-g, bone growth at 1-g, etc is not complete. That detailed research here can eliminate many side-issues and provide useful techniques and knowledge that can be applied to an orbiting facility. Why waste (expensive) days of research in space studying an effect that can be studied here or using unmanned experiments? At some point the cost of further research here will be greater than that of an orbiting facility, but until then, there's work to be done on Earth. ------------------------------ Date: 24 May 91 12:55:00 GMT From: dev8g.mdcbbs.com!rivero@uunet.uu.net Subject: Re: SR-71 In article <7P5622w163w@lobster.hou.tx.us!n5abi>, lobster.hou.tx.us!n5abi!gak (Gene A. Kennedy) writes: > The June issue of Popular Mechanics includes an article on the SR-71 and > mentions that NASA is putting three back in service for research. Does > anyone know where they will operate from? I would guess Edwards but the > article never says. > > ----------------------------------------------------------------------- > Gene Kennedy - Ham Radio Operator, N5ABI - lobster.hou.tx.us!n5abi!gak > ----------------------------------------------------------------------- > -- At least one is at Edwards, and was operational when I saw it, even though the plane had been officially "retired". A second SR-71 is supposedly going to be used to help monitor the ozone hole over antartica. In both cases, the aircrafts value lies in its extreme altitude. Guess you can't keep a good airframe down! ========================================================================== \\\\ Michael Rivero | "I drank WHAT!" |"Why bother with marriage?| (. rivero@dev8a.mdcbbs | Socrates -------------------Just find a | )> DISCLAIMER::: |-----------| "Life is CHEAP! |woman you hate == "Hey man, I wasn't |Looking4luv| But toilet paper|and buy her a | ---/ even here then!" |Settle4sex!| is EXPENSIVE!" | house!" | ++++++++++++++++++++++++++++++++++++++++-------------------+++++++++++++++ ------------------------------ End of SPACE Digest V13 #640 *******************