Date: Wed, 26 Aug 92 04:59:59 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #143 To: Space Digest Readers Precedence: bulk Space Digest Wed, 26 Aug 92 Volume 15 : Issue 143 Today's Topics: BuckyStalks (was Re: Beanstalks in Nevada Sky) Global positioning sys GOP space platform text Need GIF (JPG, whatever) of Shuttle Landing Opinions on NLS (2 msgs) Private space ventures (4 msgs) Saturn class (Was: SPS feasibility and other space (3 msgs) Spot Images Corp and EOSAT addresses TOPEX Update - 08/24/92 Venus orbiters With telepresence, who needs people in Earth orbit? (3 msgs) Welcome to the Space Digest!! Please send your messages to "space@isu.isunet.edu", and (un)subscription requests of the form "Subscribe Space " to one of these addresses: listserv@uga (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle (THENET), or space-REQUEST@isu.isunet.edu (Internet). ---------------------------------------------------------------------- Date: 24 Aug 92 16:34:54 GMT From: Dani Eder Subject: BuckyStalks (was Re: Beanstalks in Nevada Sky) Newsgroups: sci.space >Seriously, since I'm posting this anyway, does anyone know of any >cleverer (or at least easier) ways to get a beanstalk built than >the extrude-it-from-Geosynch approach? Specifically, anything that would >let us keep the factory on the ground? Sure. Two approaches to building a beanstalk: literal bootstrapping and gun-launch. In the first: You have a small vehicle (maybe 10 ton takeoff mass) that is designed to take a small payload (like 1 ton) to a high suborbital speed (like 5 km/s). This vehicle would use LOX/H2 rockets. At this speed you dump a 1 ton payload consisting of solid rocket motor plus spool of tether material. The rocket motor kicks you up to orbit and delivers maybe 200 kg tether stuff to orbit. As you collect these spools of tether and build down from LEO, you run an electrodynamic engine and raise the tether system, keeping the bottom end just above the atmosphere. As you build up the tether, the bottom end moves slower with respect to the ground. Eventually, you are moving slow enough that the vehicle can fly directly to the bottom of the tether, continuing to deliver cable sections (and also payloads for paying customers). As the tether grows, the vehicle can deliver larger and larger payloads since it is flyinbg to a slower velocity, theus the construction rate goes up (in terms of kg of tether delivered per flight). Given a strong enough material, you eventually get the bottom end to stop, and attach it to a tower you have built up from the ground to meet it. Method 2: Use a gas gun on the ground to fire cannisters of cable to Earth orbit. The cannisters may be as small as 20kg and still be effectively launched from the ground. This saves you from having to build the cryogenic vehicle until later. Meanwhile, you can get revenue from carrying customer spacecraft from LEO up to the top of the developing tether and releasing them, giving them a boost on their way. After that, you continue as in method 1. Once you have a large tether that has the span you want, you can increase it's payload by hauling up parallel strands, literally lifting by your own bootstraps. Dani Eder -- Dani Eder/Boeing/Advanced Civil Space/(205)464-2697(w)/232-7467(h)/ Rt.1, Box 188-2, Athens AL 35611/Member: Space Studies Institute Physical Location: 34deg 37' N 86deg 43' W +100m alt. ***THE ABOVE IS NOT THE OPINION OF THE BOEING COMPANY OR ITS MANAGEMENT.*** ------------------------------ Date: 18 Aug 92 19:22:47 GMT From: Keith Stein Subject: Global positioning sys Newsgroups: sci.space Jeff you'll need to contact the Air Forc for GPS information. ------------------------------ Date: Tue, 25 Aug 1992 13:05:52 GMT From: Stephen J Kenny Subject: GOP space platform text Newsgroups: sci.space In article tjn32113@uxa.cso.uiuc.edu (Tom Nugent ) writes: >Does anybody have the Democratic platform on space? > They're in favor of it.. ------------------------------------------------------------- "Away..we go...so fast...." | sjk@kepler.unh.edu - Autosexual | s_kenny@unhh.unh.edu Be Bop Deluxe | Stephen J. Kenny ------------------------------------------------------------- ------------------------------ Date: 25 Aug 92 21:17:56 GMT From: Dennis Bruggink Subject: Need GIF (JPG, whatever) of Shuttle Landing Newsgroups: sci.space Maybe someone can save me some hunting: I've checked a number of sites w/ GIFs for an image of the shuttle landing; I've found one in the Hubble series (hubble24.gif) which is exactly the view I'm after, but it's not very sharp. Basically the shuttle has just touched down, and is seen as from a side view. Going through various achives has taken a lot of time, and the directory listings are usually not at all specific (e.g., shuttle1, shuttle2, ...). So ... doesn't anyone have a pointer to this image, or recall coming across it anywhere?? thanks, -dennis bruggink ------------------------------ Date: 25 Aug 92 11:45:14 GMT From: Gary Coffman Subject: Opinions on NLS Newsgroups: sci.space In article <1992Aug24.142419.23121@iti.org> aws@iti.org (Allen W. Sherzer) writes: >the bottom line on NLS is that it will not reduce costs but will >actually raise costs if you factor in development costs. On the other >hand, we have proposals out there for Delta and Titan derived HLV's >which WILL reduce costs by a factor of two even if development costs >are included (assuming they work). NASA's primary mission is air and space flight R&D. It's secondary mission is operational support of pure science missions and waving the flag. The primary mission means that development costs are not an expense, they are an opportunity to perform the primary mission. The secondary mission means that spacecraft should have the lowest possible operational costs consistent with mission support, development cost of the vehicle isn't important if it is done in house as part of the primary mission. If it's an out of house commercial purchase, then R&D costs must be charged against operations, raising secondary mission costs. Failure to understand mission accounting rather than life cycle accounting leads to dependence on old technology when the primary mission is to push new technology. Gary ------------------------------ Date: 25 Aug 92 16:54:25 GMT From: "Allen W. Sherzer" Subject: Opinions on NLS Newsgroups: sci.space In article <1992Aug25.114514.29920@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: >NASA's primary mission is air and space flight R&D. Since NLS is not R&D but rather operations this is another excellent reason for dropping NLS. >primary mission means that development costs are not an expense, they are >an opportunity to perform the primary mission. For operational vehicles, like NLS, development costs ARE an expense. Since NLS is intended to be a simple operational vehicle it does not support NASA's mission. >Failure to understand mission accounting rather than life cycle accounting >leads to dependence on old technology when the primary mission is to push >new technology. Failure to understand the difference between research and operations leads to money going to operations when it would be better spent on research. The goal of NLS is not to conduct research; it is to replace existing launch vehicles with more expensive alternatives. People ask why there is no Bill Gates for space. The answer is right here: so long as we make a virtue out of wasting money and paying more then we need to we aren't going anywhere. Allen -- +---------------------------------------------------------------------------+ | Allen W. Sherzer | "If they can put a man on the Moon, why can't they | | aws@iti.org | put a man on the Moon?" | +----------------------241 DAYS TO FIRST FLIGHT OF DCX----------------------+ ------------------------------ Date: 25 Aug 92 13:51:14 GMT From: "Frederick A. Ringwald" Subject: Private space ventures Newsgroups: sci.space (attribution lost in the shuffle) > [It bugs me that there are people like H Ross Perot, who > themselves have enough cash to finance their own space > programs, but that none, so far, has underwritten one.] Don't worry about it, I'm sure something like it will happen, sooner than you think. For practical uses of space technology, private investors have for years been able to buy stock in aerospace companies such as Boeing and Lockheed. Howard Hughes had many millions worth of shares in, ahem, Hughes Aircraft. Since it's been brought up, if space technology is so useless for the Third World, then how come Mexico, India, and Indonesia are acquiring their own communications satellites? Meteorological satellites can see typhoons heading toward Bangladesh as well as they can hurricanes for Florida, and the list goes on. When space technology and services look like good investments to these countries, for the amount of capital they can afford, they do invest, just like everyone else. (Also, it bothers me to hear arguments about how "the Third World doesn't bother me at all, they're overpopulated anyway." This strikes most people as very callous. You wouldn't think this if you were in this situation: for an interesting perspective on the dubious notion of "surplus population", re-read "A Christmas Carol," by Charles Dickens. Space should be helpful, not hurtful, and it certainly can be helpful, as many other technologies can be.) For the more abstruse uses of space technology, promising no immediate payback, a modest level of effort still gets funded, sometimes, because people value it. People enjoy learning about the Universe; if people think a project is interesting enough to warrant the funding requested, the project gets funded. Sometimes there turn out to be paybacks, but I think it's dishonest to claim there certainly shall be immediate practical applications when they are still only speculative, and may appear really only in the long term (some of which turn out to be very important, but you can't know in advance which ones). The main objective of such projects is the science, to learn about nature. Of course this decision process can be involved. Physicists are having trouble funding the Superconducting Super Collider, at a cost of over $8 billion, in today's weak economy. It certainly does not help this project that most people find the science involved difficult to understand: how familiar are you with experimental tests of Standard Model 1-2-3 electroweak theory? (Beam jockeys excepted.;-)) The W.M. Keck foundation has donated over $70 million to build the 10-m Keck telescope in Hawaii. This is now the largest telescope in the world: its size will make it able to see unprecedentedly faint objects. The value of this to astronomical research is easy to understand. All the mirror segments are in, testing is underway, and so far it looks to be a first-class telescope. Astronomy has benefited from private funding since the time of Lord Rosse, continuing through the telescopes on Mount Wilson and Palomar, not to mention my favorite, the 1.3-m McGraw-Hill telescope on Kitt Peak. So, I think it's just a matter of time before some private individual or venture funds a similar project in space. A good candidate will be a replacement for the International Ultraviolet Explorer satellite, which has revolutionized nearly every field of astronomy (see Exploring the Universe with the IUE satellite, ed. by Y. Kondo). IUE is still at it, after 14 years, and even despite its much-larger successor, the Hubble Space Telescope (which is a nightmare to try to get telescope time on). Now, IUE originally cost about $25 million, about 1% of HST. With inflation and an advanced detector, a successor might cost about $100 million: not too unlike the Keck telescope. I am quite sure my friends in planetary science and space physics will have no trouble thinking up interesting projects in their own fields: we're looking at a price range of a-few-to-100 million dollars. Face it, $1 billion is a mighty big piece of pocket change, even for Ross Perot or Bill Gates! Fred ------------------------------ Date: 25 Aug 92 14:03:14 GMT From: nicho@VNET.IBM.COM Subject: Private space ventures Newsgroups: sci.space In <1992Aug25.035359.23129@dartvax.dartmouth.edu> Frederick A. Ringwald writes: >(Also, it bothers me to hear arguments about how "the Third World >doesn't bother me at all, they're overpopulated anyway." This strikes >most people as very callous. I'll pick this up, since it was my comment you are objecting to. Firstly, I was responding to the poster who whinged about spending money on a space program instead of feeding the starving millions. Most moderately sentient beings will recognise this as a piece of fin de siecle western angst. My response was designed deliberately to be excessively callous, in an attempt to highlight the stupidity of the original append. >You wouldnUt think this if you were in this situation: Perhaps not, however I would hope that were I in such an unfortunate situation, I would have sufficient vision to recognise that the best way out for all, was wealth creation (access to extra resource in space) rather than redistribution. >Space should be helpful, not hurtful, and it certainly can be helpful, >like many other technologies.) Space can indeed be helpful, however if we have too many fools screaming about it being a waste of resource, we will never have the chance to prove it. As an aside, I will point out that most of those starving in Africa are doing so because their family and countrymen think it more important to kill each other than feed each other. Against a climate such as this, it is difficult to see how diverting finance from space into Africa is going to be of any lasting benefit. ----------------------------------------------------------------- ** Of course I don't speak for IBM ** Greg Nicholls ... nicho@vnet.ibm.com or nicho@cix.compulink.co.uk voice/fax: 44-794-516038 ------------------------------ Date: 25 Aug 92 19:40:16 GMT From: "Frederick A. Ringwald" Subject: Private space ventures Newsgroups: sci.space In article <9208251422.AA08296@ucbvax.Berkeley.EDU> nicho@VNET.IBM.COM writes: > Space can indeed be helpful, however if we have too many fools > screaming about it being a waste of resource, we will never have the > chance to prove it. I wouldn't worry about it. During the Apollo project, everyone and his brother was complaining about it being just a stunt, a waste, "a boondoggle for scientists", while the money could have been used to feed the "whole of India." But no one says that about communications or weather satellites today, except the extreme fringe (and I know one of them: he's the only person I know who couldn't read after graduating from high school). Space benefits are obvious, in ways they weren't in 1972: how many people did you know back then who owned their own satellite dishes? If and when GPS receivers for cars are mass-marketed, the effect on people's attitudes will be interesting. Especially interesting may be the effect of space-manufactured goods, particularly ones that aren't microscopic (like microspheres) or indistinguishable from similar items made on the ground (a bottle of medicine looks like a bottle of medicine). (Two-way wrist TVs would be interesting, too, but they may not need satellites.) Also, in the past, I have heard disturbingly many space enthusiasts using words quite like your ironic statement, and sounding sincere! Not only is this mean, it's positively harmful to the space field. On the other hand, trickle-down economics doesn't really work: any benefits that accrue from space to the poor have to be in the hands of the poor in the first place. But many are, already. Your proof exists, and becomes more obvious all the time. P.S. It is still perfectly possible to waste money in space, as one can waste money at any activity, no matter how beneficial or appealing it may seem. Avoiding waste requires careful examination of just what one wants to do with that money... ------------------------------ Date: 25 Aug 92 20:30:55 GMT From: Henry Spencer Subject: Private space ventures Newsgroups: sci.space In article <1992Aug25.194016.3584@dartvax.dartmouth.edu> Frederick.A.Ringwald@dartmouth.edu (Frederick A. Ringwald) writes: >...If and when GPS receivers for cars are mass-marketed, the effect on >people's attitudes will be interesting... It won't help. The belittlers will just redefine the "space program" they are criticizing to exclude these obviously-useful things. -- There is nothing wrong with making | Henry Spencer @ U of Toronto Zoology mistakes, but... make *new* ones. -D.Sim| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 25 Aug 92 16:06:50 GMT From: "Edward V. Wright" Subject: Saturn class (Was: SPS feasibility and other space Newsgroups: sci.space In <1992Aug20.112421.8946@techbook.com> szabo@techbook.com (Nick Szabo) writes: >Heavy-lift vehicles from Saturn to Energiya to NLS have >not and do not have any sort of commercial market, despite $dozens of >billions spent in them. Even the Titan IV has only a dwindling military market. If the Saturn V can be built for the same cost as the Titan III/IV and has better reliability, the extra payload capacity won't stop customers from using it. If necessary, they'll add water tanks for ballast. ------------------------------ Date: 25 Aug 92 17:19:59 GMT From: Josh 'K' Hopkins Subject: Saturn class (Was: SPS feasibility and other space Newsgroups: sci.space ewright@convex.com (Edward V. Wright) writes: >In <1992Aug20.112421.8946@techbook.com> szabo@techbook.com (Nick Szabo) writes: >>Heavy-lift vehicles from Saturn to Energiya to NLS have >>not and do not have any sort of commercial market, despite $dozens of >>billions spent in them. Even the Titan IV has only a dwindling military market. >If the Saturn V can be built for the same cost as the Titan III/IV >and has better reliability, the extra payload capacity won't stop >customers from using it. If necessary, they'll add water tanks for >ballast. > Sure, _if_ you can build _and_ operate a Saturn class vehicle for the price of a Titan it might be competitive with a Titan. However, seeing as there are no non-government customers for Titans and considering that the first launches are going to have to pay for development costs, I think Nick is right in saying that HLVs have no commercial relevance in this decade. If we could launch Saturn size payloads for the price of a Titan III, that might get a government SEI program going. However, industry won't build this rocket, and government won't buy it without an SEI program (which it won't start until a big cheap rocket works). So we seem to be at an impasse until the equation changes. -- Josh Hopkins Friends don't let friends derive drunk j-hopkins@uiuc.edu ------------------------------ Date: 25 Aug 92 21:03:14 GMT From: "Allen W. Sherzer" Subject: Saturn class (Was: SPS feasibility and other space Newsgroups: sci.space In article jbh55289@uxa.cso.uiuc.edu (Josh 'K' Hopkins) writes: >I think Nick is right >in saying that HLVs have no commercial relevance in this decade. SS Freedom construction and supply IS a viable commercial market for HLVs this decade. Allen -- +---------------------------------------------------------------------------+ | Allen W. Sherzer | "If they can put a man on the Moon, why can't they | | aws@iti.org | put a man on the Moon?" | +----------------------241 DAYS TO FIRST FLIGHT OF DCX----------------------+ ------------------------------ Date: 25 Aug 92 18:01:13 GMT From: "Philippos A. Peleties" Subject: Spot Images Corp and EOSAT addresses Newsgroups: sci.space I would appreciate it if anyone out there could e-mail me the complete address (FAX+phone) of Spot Images Corporation (Reston, VA?) and EOSAT (the company who's marketing EOSAT satellite pictures.) Thanks in advance Philip Peleties -- I speak for myself, I think for myself, I work for myself ... but I don't want to play by myself ... so bring your toys and let's share ... ------------------------------ Date: 25 Aug 92 23:49:20 GMT From: Ron Baalke Subject: TOPEX Update - 08/24/92 Newsgroups: sci.space,sci.astro Forwarded from: PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. (818) 354-5011 TOPEX/POSEIDON STATUS REPORT August 24, 1992 The TOPEX/Poseidon satellite is healthy and performing nominally. The attitude control computer, batteries, telecommunications and on-board computer are all functioning properly. Tape recorder playback has occurred as planned since last Friday. The Centre National d'Etude Spatiales' Solid State Altimeter (SSALT) is in a four day check out period. CNES is processing the data in Toulouse and engineers there report all looks good. The NASA altimeter will be commanded to the track mode after the CNES altimeter is turned off. The TOPEX Microwave Radiometer is working well. An inclination maneuver is planned for Thursday to boost the satellite to its 66 degree inclination toward the Earth. ###### ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Optimists live longer /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | than pessimists. |_____|/ |_|/ |_____|/ | ------------------------------ Date: 25 Aug 92 21:40:41 GMT From: Jeff Bytof Subject: Venus orbiters Newsgroups: sci.space Is the Pioneer Venus orbiter still functioning? Besides Magellan, what other spacecraft (Russian?) may be still functional? Jeff Bytof rabjab@golem.ucsd.edu ------------------------------ Date: Tue, 25 Aug 1992 11:56:43 GMT From: Rui Sousa Subject: With telepresence, who needs people in Earth orbit? Newsgroups: sci.space In article <1992Aug24.043114.23137@ke4zv.uucp> gary@ke4zv.uucp (Gary Coffman) writes: Not the same thing at all. Except for the Viking landers, *none* of the spacecraft that ventured beyond the Moon have been able to manipulate their environment. They have been mere sensor platforms. The common usage of robot is more specialized than automation. It requires the ability to manipulate the environment. The term robot also ordinarily means autonomous to a large degree, capable of on the spot decisions. This is in contrast to teleoperated devices that require distant super- vision at the detail level in near real time. There have been no robots in space with the autonomy of a fruit fly or the manipulative ability of a mouse as yet. Nothing approaching the capability of a man has even been designed, let alone successfully tested, on Earth as yet. Earthlings have sent out glorified box brownies to snap pictures, but nothing designed to turn over a rock. Gary You are forgetting the Luna series and the Viking landers. Though not autonomous they certainly could turn rocks over... Rui Sousa -- *** Infinity is at hand! Rui Sousa *** If yours is big enough, grab it! ruca@saber-si.pt All opinions expressed here are strictly my own ------------------------------ Date: 25 Aug 92 13:05:42 GMT From: Gary Coffman Subject: With telepresence, who needs people in Earth orbit? Newsgroups: sci.space In article <1992Aug24.222651.12891@jpl-devvax.jpl.nasa.gov> jenkins@fritz (Steve Jenkins) writes: >In article <1992Aug24.043114.23137@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: >>Not the same thing at all. Except for the Viking landers, *none* of the >>spacecraft that ventured beyond the Moon have been able to manipulate >>their environment. > >Why except Viking? It *was* able to manipulate its environment. I'd >argue that Voyager has no environment to manipulate. What did you have >in mind? Why except Viking? Because the landers did have the limited ability to manipulate their environment by taking a soil sample and analysing it, and it travelled beyond the Moon, the other parameter of the statement. Voyager doesn't qualify as a robot because it is only a sensor platform with no way to modify it's environment. It's true that it's environment isn't very dense with matter, but irrelevant to whether it's a robot or an automated sensor platform. >>This is in contrast to teleoperated devices that require distant super- >>vision at the detail level in near real time. > >Current planetary spacecraft are not operated that way. The one-way >light time to Voyager 2 at Neptune encounter was on the order of four >hours. That's stretching my notion of "near real time" a bit. Even >nearby Magellan does its thing mostly on its own; the routine >commanding is mostly housekeeping stuff of a noncritical nature. >Sometimes we give 'em the whole weekend off. :-) It's true that these sensor platforms have some autonomous self safing capability, but mission critical actions are commanded from the ground. These commands are almost completely open loop in that they don't depend on any immediate environmental feedback resulting from their actions toward their objective to close the loop, only delayed reaction commands from ground stations. Note that I don't count starcals because they aren't the objective of the mission sensor systems. That may be arbitrary, but they are simple navigational servo systems rather than systems that react to mission objectives. Robots need servos, but servos aren't the robot if you get my meaning. >>There have been no robots in space with the autonomy of a fruit fly or >>the manipulative ability of a mouse as yet. Nothing approaching the >>capability of a man has even been designed, let alone successfully >>tested, on Earth as yet. Earthlings have sent out glorified box brownies >>to snap pictures, but nothing designed to turn over a rock. > >Except Surveyor 7, Luna 16, Luna 17, Luna 20, and Vikings 1 and 2, >depending on what counts as a rock. As noted in the first paragraph, I am referring only to non-lunar missions and listed Viking as the (limited) exception. Even Viking's action was an open loop pre-programmed action in a spot determined solely by the way the lander faced when it touched down. A real robot would say, "Gee that's an interesting pile of dirt, think I'll dig there." (Metaphorically of course.) That's why I said that robots in space don't yet have the autonomy of a fruit fly or the manipulative ability of a mouse. >No one claims that highly autonomous, highly intelligent robots have >been sent to explore space. That doesn't make all exaggerated >statements to the contrary true. Nick, the astronaut basher, seems to think so. He's the one to which I was replying. The sensor platforms sent to the outer solar system have been impressive achievements. I don't denigrate their importance even while calling them box brownies. Getting them there, getting them to snap pictures in the right direction, and getting the pictures back is a monumental achievement mainly because *competent AI doesn't exist* and everything had to be done open loop over long delay command links. Jupiter probes didn't notice the Red Spot and say, "hmmmm that's interesting" and zoom in for a closeup. Ground calculations had to be done to open loop aim the probe's camera to capture a known feature of Jupiter. I'd even accept a system that could be told, "find a big red spot and get me a picture of it", to be somewhat robotic, but Jupiter probes haven't been able to do this. Io's active volcano was an after the fact discovery from a picture taken that included it by chance. A competent AI system might have zoomed in and gotten pictures of that interesting feature in real time, assuming a zoom lens of course. But no such image recognition capability has been included on any sensor platform in deep space to date. Some kind of self direction based on the results of environmental sensing is a requirement of a competent robot, but not the only one. It must also be able to modify it's environment in a closed loop feedback. None have so far been launched into space. So I maintain that Nick's claim that all work beyond the Moon's orbit has been done by robots is false since no robots have been sent beyond Lunar orbit, except a pair of very primitive Vikings and a couple of Veneras. I don't consider them to be robots in any real sense, however, because they lacked mission oriented self direction modifiable by closed loop feedback from sensor discoveries. Gary ------------------------------ Date: 25 Aug 92 13:31:34 GMT From: Gary Coffman Subject: With telepresence, who needs people in Earth orbit? Newsgroups: sci.space In article <1992Aug24.175759.1@fnalf.fnal.gov> higgins@fnalf.fnal.gov (Bill Higgins-- Beam Jockey) writes: > >Henry Spencer, I expect, would agree fully with Matthew's statement, but >insist that to engineer all this stuff, you've got to fly it, try it, >take it home and fix mistakes, then fly again-- as he recently >advocated during the Tethered Satellite System discussion. Frequent >and simple access to orbit is the key. What NASA has now is "We're >only gonna get one chance this decade to fly our gadget, and if it >doesn't work our careers are shot, so it must be super-reliable and >gold-plated." One of the reasons that missions only fly once per decade is that they *are* super-reliable and gold plated. Launch costs are usually a small fraction of payload costs. They are still a significant cost, however. One way to shorten the build, fly, try, recover, fix, iterate cycle, however, is to plan to fix the problems on the spot. NASA didn't do that with the tether experiment, but they could have, and they have done so with other experiments on other flights. Manned flight does have significant advantages because competent robotics don't exist. It also has significant expenses of course. It seems to me that the arguments center on what is the right mix of cheap "try it" missions and more expensive "try it and fix it if necessary" missions. I tend to think the latter can be more productive right now. Dirt cheap and frequent launches could change that, but I don't see any indication that's about to happen, SSTO wishful thinking not withstanding. Gary ------------------------------ End of Space Digest Volume 15 : Issue 143 ------------------------------