Date: Sun, 13 Dec 92 05:07:15 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #541 To: Space Digest Readers Precedence: bulk Space Digest Sun, 13 Dec 92 Volume 15 : Issue 541 Today's Topics: Aurora Cassini Undergoes Intensive Design Review Hypergolic Hybrids? liquid fuels Re: Cassini Undergoes Intensive Design Review Saturn history (2 msgs) Scud Missile technology Space docking Space suit research? Space Tourism SSF Deputy Dir. Interview Terminal Velocity of DCX? (was Re: Shuttle ...) Titan IV what the little bird told Henry (2 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: 12 Dec 92 20:12:00 GMT From: David.Anderman@ofa123.fidonet.org Subject: Aurora Newsgroups: sci.space Some other reports on Aurora from southern California: On many Thursday mornings, this area is being shaken by earthquake-like tremors which are supposedly sonic booms from some secret plane. The Los Angeles Times reported during the late 1980's that airline pilots were seeing delta winged aircraft flying extremely high and fast over the Pacific Ocean. At the time, the LA Times speculated that the mystery aircraft was a prototype A-12, a project subsequently cancelled by the DoD, due to massive cost overruns.... ___ WinQwk 2.0b#0 --- Maximus 2.00 ------------------------------ Date: 11 Dec 92 18:28:29 GMT From: Frank Crary Subject: Cassini Undergoes Intensive Design Review Newsgroups: sci.space Sender: USENET News System Organization: University of Colorado, Boulder Lines: 32 Nntp-Posting-Host: ucsu.colorado.edu Source-Info: Sender is really news@CRABAPPLE.SRV.CS.CMU.EDU Source-Info: Sender is really isu@VACATION.VENARI.CS.CMU.EDU In article <1992Dec10.232527.643937@locus.com> hayim@locus.com (Hayim Hendeles) writes: >> After flybys of Venus (twice), Earth and Jupiter as it loops >>around the sun to pick up energy, Cassini will arrive at Saturn >>in November 2004, beginning a four-year orbital tour of the >>ringed planet and its 18 moons. The Huygens probe will descend to >>the surface of Titan in June 2005. >Pardon my asking an ignorant question, but I can't understand why it >should take 7 years to get to Saturn. When Voyager went to Jupiter and >Saturn, it took (if I recall correctly) 4 years and a Jupiter flyby to >make it to Saturn. Here, you are using 4 flybys, and it's taking you 7 >years! After the Challenger failure, NASA added a safety requirement that nothing launched in by a space shuttle may use liquid fuels. That means Cassini must use lower-energy solid rockets instead. As a result, a direct launch to Saturn (or a single Jupiter fly-by on the way) is not possible. A long VEEJGA series of fly-bys of the inner planets is required to gain suffiecient energy. >I would think that if you were to adjust the launch date so that >Jupiter and Saturn were in the same relative positions as they were in >1977 (when Voyager was launched), you could do the same trick again (in >the same 4 years). While the Earth/Jupiter/Saturn geometry is different, I don't think it it sufficiently worse (in terms of time and energy) than that of the Voyager fly-by. In any case, waiting for the optimum geometry isn't really possible: It would take many decades... Frank Crary CU Boulder ------------------------------ Date: Sat, 12 Dec 1992 20:08:55 -0500 From: Lawrence Curcio Subject: Hypergolic Hybrids? Newsgroups: sci.space I was wondering if anyone ever played with the idea of hypergolic hybrid rockets. It seems to me this would solve a lot of problems. I even have a family of propellant combinations in mind. Diphenyl amine, when reacted slowly with warm, dilute nitric acid yields a tarry sludge that breaks up into delightful free radicals when heated. This sludge can be mixed with monomers (e.g.; styren) to form materials with more desireable physical properties. In fact, the sludge takes the place of a curing agent (free radical initiator). Said materials would likely be hypergolic with N2O4 or RFNA. The system could then be programmed with paper tape... ------------------------------ Date: 13 Dec 92 01:39:07 GMT From: Henry Spencer Subject: liquid fuels Newsgroups: sci.space In article <1992Dec12.191157.22663@ee.ubc.ca> davem@ee.ubc.ca (Dave Michelson) writes: >>-After the Challenger failure, NASA added a safety requirement that >>-nothing launched in by a space shuttle may use liquid fuels... >>I think you mean *cryogenic* fuels. Magellan, Galileo, and Ulysses all >>use liquid fuels. > >The major problem with cryogenic fuels is that they boil off and the >gas must be vented. This becomes a real problem if the upper stage >is located inside the shuttle cargo bay. The modifications that must >be made to the shuttle are non-trivial. Sorry, wrong. Cryogenic fuels fly in the payload bay on every extended- duration shuttle flight. The shuttle's fuel cells use liquid hydrogen and liquid oxygen, and the extended-duration pallet for the cargo bay (first flown recently) is basically a set of LH2 and LOX tanks. Shuttle/Centaur, the launch system originally meant for Galileo (as well as the other two, but it was the massively-overweight Galileo mission that drove its specs), died partly because of an acute attack of timidity after Challenger, partly because people distrusted some aspects of Centaur's construction, and partly because Centaur+Galileo was so heavy that it led to problems like needing to jettison its fuel before an emergency landing. A somewhat smaller LOX/LH2 stage with more conservative construction could probably be certified for shuttle use even now, but nobody wants to try. -- "God willing... we shall return." | Henry Spencer @ U of Toronto Zoology -Gene Cernan, the Moon, Dec 1972 | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 13 Dec 92 01:42:27 GMT From: Henry Spencer Subject: Re: Cassini Undergoes Intensive Design Review Newsgroups: sci.space In article <7470027@hpfcso.FC.HP.COM> cunniff@hpfcso.FC.HP.COM (Ross Cunniff) writes: >You have to consider that Cassini (and Galileo) are *HUGE* interplanetary >probes. Voyager was a lightweight - a Titan II launch sent it on a direct >orbit to Jupiter, and then it used a gravity assist to Saturn and beyond. Small correction: Voyager flew on a Titan III-Centaur, the heaviest booster the US had at the time (having abandoned the Saturn V and not yet flown the shuttle). -- "God willing... we shall return." | Henry Spencer @ U of Toronto Zoology -Gene Cernan, the Moon, Dec 1972 | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 12 Dec 92 02:42:14 GMT From: Brian Stuart Thorn Subject: Saturn history Newsgroups: sci.space >In article prb@access.digex.com (Pat) writes: >>>The first Saturn I flew on 27 Oct 1961, actually. >> >>So if the Saturn I was ready in 61, why didn't they use it for >>Gemini? > >The test flights needed to make it ready (by von Braun's standards) covered >the next several years. For one thing, the first few flights had no upper >stage and were incapable of making orbit. >-- >"God willing... we shall return." | Henry Spencer @ U of Toronto Zoology > -Gene Cernan, the Moon, Dec 1972 | henry@zoo.toronto.edu utzoo!henry > Besides, wasn't the driving force in the Gemini delays of 1964 the spacecraft, not the booster? Titan II was more or less ready. -Brian ------------------------------ Date: 12 Dec 92 04:32:16 GMT From: Brian Stuart Thorn Subject: Saturn history Newsgroups: sci.space >This is very true and also what Von Braun wanted to do with the Saturn V. They >wanted to fly the Saturn first stage, the two stages, etc.... The success of >the Saturn IB flying the SIVB Saturn stage allowed them to do what they >called "full up" testing, where the launched the full stack on the first >SV flight. > >By the way the Saturn I had a perfect record, 28 launches and no failures. >Also a thing of note is that the Centaur was originally designed and flown >on the Saturn I as the upper stage. > >Dennis, University of Alabama in Huntsville. > Centaur on the Saturn? I think I remember that it was considered as a fourth stage for Saturn 5 (with early Voyager planning?) but I believe you're confusing the RL-10 and the Centaur. RL-10 powered the S-IV (predecessor to the J-2 powered S-IVB) but I don't think Centaur ever flew anything other than Atlas or Titan. -Brian ------------------------------ Date: 10 Dec 92 00:01:42 GMT From: Frank Dahncke Subject: Scud Missile technology Newsgroups: sci.space In David.Anderman@ofa123.fidonet.org writes: >I have yet to uncover exactly what a Scud missile is. >I know what it does. I know that its NATO derivation (SS-1A) is similar to the >earliest Soviet missile, the SS-1 - a V-2 derivative - but the Scud is in no >way a dervivative of the SS-1. >Is the Scud a liquid fuel missile? Is it a solid? If liquid, what fuels does >it use? What is its engine designation? What design bureau created its engine? >What is its specific impulse? All those and similar questions can and will be answered on sci.military. Hope this helps, Techno -- | techno@zelator.in-berlin.de ||| Please do not e-mail from outside Germany ! | | techno@lime.in-berlin.de / | \ Hardcore ST user ! ====================== | | Nothing that's real is ever for free, you just have to pay for it sometime. | | (Al Stewart) | ------------------------------ Date: 11 Dec 92 18:57:02 GMT From: Josh 'K' Hopkins Subject: Space docking Newsgroups: sci.space henry@zoo.toronto.edu (Henry Spencer) writes: >gary@ke4zv.UUCP (Gary Coffman) writes: >>That's an interesting question anyway. How is docking with Freedom >>supposed to be handled? >Unless it's changed since I saw it described, basically the shuttle gets >close, and then the station's arm reaches out, grabs it, and moves it >into position. For some of the early assembly, it'll be vice-versa with >the shuttle arm doing the work, but the shuttle arm isn't strong enough >to move the whole shuttle around routinely. >This makes considerable sense, in general. For routine use, you want a >docking method that tolerates considerable error. Getting within the >"capture volume" of an arm is a lot less fussy than making the docking >yourself. This is also consistant with what I've read about rendezvous procedure. Since SSF is both expensive and fragile ground control is planning to be very careful about slinging big vehicles around it. Rather than aiming for the docking port, you aim for a spot next to it, and set up your trajectory so that if the vehicle looses power at any point it will just glide on by. Once you get close, the arm guides you in. It's possible this could change if we decide to use the Russian APAS system. From what I've heard it's very rugged and well thought out. -- Josh Hopkins jbh55289@uxa.cso.uiuc.edu Ho^3 !=L ------------------------------ Date: Sat, 12 Dec 92 21:30:55 EST From: John Roberts Subject: Space suit research? -From: fcrary@ucsu.Colorado.EDU (Frank Crary) -Subject: Re: Space suit research? -Date: 25 Nov 92 04:45:43 GMT -Organization: University of Colorado, Boulder -In article <17722@mindlink.bc.ca> Bruce_Dunn@mindlink.bc.ca (Bruce Dunn) writes: -[JR]: ->> Apparently anything significantly below 3 psi partial pressure of oxygen ->> is a potential health risk, unless you have many generations of ancestors ->> who lived in the mountains. -I'm not sure what you mean by "significantly", but this certainly doesn't -apply to ~2 to 2.5 psi oxygen: The residents of Aspen, many (most?) of -whom have zero generations of ancestors who lived in mountains, live -and work at such oxygen pressures, with no visible problems. Further, -people with no hereditary _or_ personal adjustment to low pressures -routinely go they to ski (which, if anything, requires slightly above -normal consumption of oxygen.) I finally found the article. It's in the October, 1992 issue of Scientific American, pp. 58-66, and is "Mountain Sickness", by Charles S. Houston, a mountain-climbing physician who specializes in high-altitude research. I'll try to post a summary of the article: The only problems dealt with in the article are those associated with hypoxia - breathing air at low pressure, or breathing oxygen-depleted air at sea level pressure. Prolonged hypoxia leads to a set of physiological changes called acclimatization. These physiological changes can lead to serious health problems. (Note that full partial pressure of oxygen but lower total pressure is a separate issue.) Mountain sickness encompasses a wide range of symptoms, which vary widely from individual to individual. Among the observed phenomena: - The reduced supply of oxygen leads to "overbreathing", which in turn seriously depletes levels of carbon dioxide, causing the pH of the body fluids to change. The kidneys are then forced to excrete biocarbonate to try to restore the balance. The rate of breathing is controlled by centers in the midbrain that are responsive to CO2 levels and blood pH, and also by the carotid bodies (small collections of cells in the neck), which are responsive to oxygen levels. The condition of hypoxia often causes dominance to shift between these two control mechanisms, resulting in periodic, or Cheyne-Stokes breathing, in which a period of rapid deep breathing is followed by a shallow breathing, and a complete cessation of breathing for a period of eight to ten seconds before the cycle repeats. This effect is more pronounced during sleep, and results in a net reduction in oxygenation of the blood. It is common above 9000 feet, and universal at higher altitudes. - Hypoxia tends to lead to increased blood flow to the brain, which causes an accumulation of fluid in the brain. This in turn causes general and localized increases in pressure, which results in headaches, staggering, difficulty in performing fine-motor skills, mental confusion, hallucinations, and sometimes death. These effects can occur at altitudes as low as 9000 feet. Countering cerebral edema is hypocapnia (decreased carbon dioxide), which can lead to decreased blood flow to the brain (and oxygen deprivation). Whether the net blood flow to the brain is increased or decreased depends on the individual. - There are many hormonal changes. An increase in the hormone erethropoetin stimulates the production of red blood cells. This in turn, can actually impede oxygen flow to tissue, increases the viscosity of the blood, and can cause extensive clotting, and sometimes congestive heart failure (the volume output of the heart is greatly increased during acclimatization). - Normally, between 20 and 30 percent of the body's capillaries are inactive. With acclimatization, the number of capillaries in active use can be increased. Enzyme changes in the cells can enhance anaerobic metabolism. - Above 10000 feet, the supply of supply of oxygen to the eyes is decreased to the extent that vision in dim light is decreased by 50%. Above 14000-15000 feet, the veins and arteries in the retina can double in size, often causing small hemorrhages. These are usually unnoticed, and it is not known whether they represent a health hazard. There is some concern that bleeding takes place elsewhere in the body, for instance in the brain, which can lead to permanent damage after repeated or prolonged exposure. - Hypoxia tends to increase the contractility of the small arteries in the lungs, increasing pressure. This in turn stimulates the production of biologically active substances, which can have a whole range of side effects, and also causes the leakage of plasma and red blood cells. Most people going to even such moderate elevations as 8000 feet experience some buildup of fluid in the lungs. This fluid can enter the alveoli, and sometimes causes drowning. - The "sodium pump" mechanism of the cells, which normally uses as much as 20% of the body's intake of oxygen, can undergo partial failure under hypoxia. This causes the cells to build up excess sodium and leak excess potassium, upsetting the water balance, and leading to edema. In many cases, acclimatization can partially offset the symptoms of mountain sickness. But even so, every 1000 foot increase in elevation reduces maximum work capacity by 3 percent. Populations that have lived for many generations at high altitudes show adaptations such as larger lungs, greater amounts of hemoglobin, and more or larger or differently placed mitochondria. But no humans have adapted permanently to elevations above 17000 feet - sea-level dwellers who move to 17000 feet can stay there for only a few months before deterioration outstrips acclimatization. The author recommends that climbers ascend no more that 2000 feet a day above 7000 feet. There are several drugs that can be used to relieve some of the symptoms of mountain sickness - taking more salt than usual is *not* recommended. It is emphasized that if serious symptoms develop, the most important thing is to get to a lower elevation (especially at night). It appears to me that while mountain sickness affects some people much more than others, a low partial O2 pressure causes some harmful effects to just about everybody. In light of the many physiological changes that take place, I think that it would be unsafe to introduce a low-oxygen atmosphere to manned spacecraft without considerable further investigation. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: 11 Dec 92 18:43:47 -0600 From: Bill Higgins-- Beam Jockey Subject: Space Tourism Newsgroups: sci.space In article , jbh55289@uxa.cso.uiuc.edu (Josh 'K' Hopkins) writes: > So, if 350 people will pay > $52,000 for a vehicle that isn't flying and isn't all that heavily advertised > I think we can assume that this price will provide a big enough market for > space tourism. The next question is how much higher it can get before the > market dries up. Is there any other data out there? What's the maximum that > real people pay for really cool Earth-bound trips? Anyone ever priced a trip > to Antarctica? Ah, the time-honored game of trying to estimate the market for space tourism... makes me nostalgic for the early days of the Shuttle era... There's a book review in the 11 December *Chicago Tribune*, on page 3 of the "Tempo" section, of a new book by a guy who paid $30,000 for a tourist trip to the North Pole. He rode on a Soviet icebreaker. Sorry, don't recall the title or author. My parents circled Mt. Everest in a jetliner, on a round-the-world trip that probably cost them several kilobucks apiece. How much would it be worth to land there? Presumably people would pay more to visit the wreck of the *Titanic*, or maybe live on the ocean floor for a week or two. O~~* /_) ' / / /_/ ' , , ' ,_ _ \|/ - ~ -~~~~~~~~~~~/_) / / / / / / (_) (_) / / / _\~~~~~~~~~~~zap! / \ (_) (_) / | \ | | Bill Higgins Fermi National Accelerator Laboratory \ / Bitnet: HIGGINS@FNAL.BITNET - - Internet: HIGGINS@FNAL.FNAL.GOV ~ SPAN/Hepnet: 43011::HIGGINS ------------------------------ Date: 12 Dec 92 13:27:45 -0500 From: tffreeba@indyvax.iupui.edu Subject: SSF Deputy Dir. Interview Newsgroups: sci.space This is a short piece on an interview I had with Martin Kress of NASA. I am sorry if it is not very good but I whacked it out when I should have been studying for finals. Thomas Freebairn SPACE STATION SAVANT SAYS NASA'S SEMANTIC SIZZLE SUCKS (so o.k. I'm a sucker for sports headlines.) Recently Martin Kress, newly installed deputy director of Space Station Freedom, was in Indianapolis to participate as a panelist in the NASA town meeting. He gave an interview to the Indiana University - Purdue University newspaper before the meeting began. Kress sat in the university hotel lobby, his words competing with the early morning vacuuming of the staff and institutional Muzak. Although he was living out of a suit case, many miles from home, Kress was impeccably dressed and seemed perfectly relaxed. While just beginning at his new post, Kress is no stranger to Washington or Capitol Hill. Starting his career in Sen. Muskie's office, working on the Senate Budget Committee, he moved on to the Subcommittee on Science, Technology and Space. Arriving at NASA in 1990 he was Assistant Administrator for Legislative Affairs before assuming the challenge of Space Station Freedom. "My beat has always been technology, budgets and policy," Kress said. "Now my beat is technology, budgets, policy and running the damn thing." With all that time on the Hill, Kress knows all about the pitfalls the space station faces. The Congressional budget cuts and the growing perception among scientists that Freedom will accomplish little, have not gone unnoticed. He believes that Space Station Freedom faces a three headed dragon. First is Congress and the budget. "When the Hill looks at an issue and they say, 'We have got to reduce the budget,' big is bad, by definition," Kress said. "They go through and look for big things. They don't look for projects that may cost $5 or $10 million and are totally ludicrous. They go after the big ones." The second is a lack of clear vision in Congress on if they want to go with big science and technology initiatives or with smaller more focused applied programs. Kress feels this tension is a debate that has yet to be articulated in the halls of power. Third is the lack of a scientific constituency for the space station. "The science community that is going to benefit most from the space station is a new and emerging one," Kress said. "There are probably only 300 people in the life science and microgravity research fields right now in the United States. I'm competing with 10,000 planetary scientists and astrophysicists for NASA funds." Yet he feels when NASA starts to announce funding for research on Freedom the science community will start to produce defenders, and not just critics, of the station. "All of a sudden we will have a built in constituency," Kress predicted. While not shy about speaking about Space Station Freedom, Kress seemed equally eager to discuss the town meetings and what NASA wanted and needed to accomplish with them. He began by explaining a change in the format for the meeting that afternoon. The Indianapolis meeting was the first that the panelists did not open with a prepared presentation. "We went out and told people that we wanted to listen and interact with them but at six o clock when the meetings ended there was this long line of people that wanted to ask questions," Kress said. "The way the format was working, we were talking too much and not listening enough. "I used to teach and I can look out into the audience and see when the eyes start to drift." Indeed the need to keep the American public's eyes from drifting was a recurring theme as Kress spoke. This need is a relatively new phenomena for NASA, according to Kress. "Until the Challenger accident and some of the events of the mid 80s, we really didn't have to go out and market ourselves or our programs," Kress said. "We _were_ the standard. Now we must really go out and let the people know. Yet he feels that NASA is not where it should be when it comes to communicating with the public. "We talk to millions and millions of people a year but for some reason we've not done a good enough job of telling the people what the value and the benefits are of the investment," Kress said. Some of the benefits he listed that were direct descendants of the space program were: - Cat-scans - MRIs - Fibulators - Computer miniaturization Some of the problems he sees with NASA communications are the over use of technical jargon and acronyms. "If you don't speak in common, simple English, who knows what you're saying," Kress said. "You can't say, 'I have a ASRM going to fly on a STS to launch the SSF.' People look at you like, 'Huh?'" Even before he started his new job at the Space Station project, Kress had begun his own campaign to lower the jargon volume. Last year he spent time with the public affairs staff and asked them to come up with a handbook in _English_. "I know it sounds crazy, but you're dealing with engineers, scientists and technical people and you're starting to understand each other, but nobody else does.," Kress said. This is an uphill battle. Kress is working on NASA liaison with the Clinton/Gore transition team and has found himself rewriting 70 percent of the print material returned to him after he requested they be made less technical. Kress would like to see a little English brought to NASA's video feed, too. "When you watch a mission on NASA Select, I would really like to see a narrator who is not a scientist or an engineer to give a narrative in simple terms," Kress said. In conjunction with this, Kress wants there to be an educational component with every NASA mission. "Have a curriculum for one year based on the missions we are going to do and bring the science back home," Kress said. "Let the kids understand what we are doing and why we are doing it." He hopes that the town meetings are the first step in better communications between NASA and the public that ultimately holds its purse strings. "People have to know what it is you are doing before they are going to support what you are doing," Kress said. #30# Non-Journalistic Asides {NJAs}: All the people I met from NASA wore great suits. Is there a NASA tailor hidden away somewhere? Special style kudos to Tyrone Taylor, NASA project manager for the town meetings. As a grubby student journalist I found myself completely out-gunned on the sartorial flank. But, then again, that's been known to happen to me at the swine barn at the state fair. I liked Kress. There was no lean forward and stare you in the eye, "Listen to me I'm a big shot" b.s. He seemed very genuine. Not bad for a Notre Dame graduate.  ------------------------------ Date: 12 Dec 92 04:33:28 GMT From: Brian Stuart Thorn Subject: Terminal Velocity of DCX? (was Re: Shuttle ...) Newsgroups: sci.space >True, a passenger version of the DC-1 couldn't carry more than >about 20 people. Of course, the Shuttle can only carry 7-10. >What's your point? I missed what this discussion is about but the above needs a few qualifiers. DC-1 would only be able to carry 20 people if it used a special passenger module in the payload bay. If you built such a module for the Shuttle, you'd get alot more than 10 people in it. Maybe 50 or so. Of course, *I* don't want a ticket in the thing. -Brian ------------------------------ Date: 12 Dec 92 04:32:51 GMT From: Brian Stuart Thorn Subject: Titan IV Newsgroups: sci.space Looks like I blew it on the Titan IV in my last post (several days ago), as one was launched on November 29, per Aviation Week and Space News. That was Number 6. I never heard anything about it, and was mildly surprised to read about it in this weeks AVLeak and Space News. It got no attention from the media (to the USAF's delight, no doubt), not even with the last military shuttle mission launched a few days later. On the topic, does anyone know how much has been spent on Titan IV since first flight? AvLeak shows launch costs at between 186-207 million dollars, or about half what a Shuttle costs (being charitable and not counting the kitchen sink at the KSC cafeteria). I'm curious how much we have paid for Titan IV to launch six payloads versus how much we paid for four times that number of Shuttle missions in the same amount of time. -Brian ------------------------------ Date: 11 Dec 92 18:36:00 GMT From: Loren Carpenter Subject: what the little bird told Henry Newsgroups: sci.space In article henry@zoo.toronto.edu (Henry Spencer) writes: >In article pgf@srl03.cacs.usl.edu ("Phil G. Fraering") writes: >>Hmm... every report that seems to come out says that the reason it's possible >>now is because of the NASP materials research. > >>BUT: if the main place where NASP materials seem to be being used is >>the heat shielding, and its re-entry temperature is lower than the >>shuttle's, wouldn't shuttle re-entry materials be just as useful? > >They'd probably work as well, but there is a durability problem. Having >to inspect every last damned tile is the last thing you want to do for a >vehicle that's supposed to have rapid turnaround. >-- Indeed. I have an engineering sample of the white tile material. It has a color, density, hardness and stiffness similar to a fine grained foamed chalk. At first it seems like a smooth styrofoam, firm and warm, but little white dust particles flake off as you handle it. It would be easy to stick a pencil clear through a tile, though it would probably crack. A moderate hailstorm would require replacing all of them. Loren Carpenter loren@pixar.com ------------------------------ Date: 13 Dec 92 00:49:32 GMT From: Henry Spencer Subject: what the little bird told Henry Newsgroups: sci.space In article shafer@rigel.dfrf.nasa.gov (Mary Shafer) writes: >Being success oriented is a wonderful idea if you're not depending on >the developement of cutting-edge technology for your success. The >YF-22/YF-23 program was an outstanding example of how very well it >works to be success oriented. They were integrating elements that >were somewhere between off-the-shelf and state-of-the-art into those >aircraft. > >But suppose that they were depending on the timely development of >several new technologies? Maybe new engines _and_ new structural >materials _and_ passive sensors _and_ flight control computers? >Then every slip in every new technology would slip the program. The answer to this one, of course, is obvious... You need two separate streams of activity: the X stream, which pushes the edge of technology and sometimes cuts itself when the edge turns out to be sharp, and the YF stream, which builds production prototypes using technology whose sharp edges are already known. Trying to skip the X stage of the process is attractive but doesn't work all that well (it's not for lack of trying, either). However, I think you can make a good case that projects in both streams ought to be run on a "success-oriented" basis. For the YF stream, as Mary points out, it works extremely well. And the X stream's job is not to build things but to learn things, and ultimately you learn by making mistakes... so best make them as quickly and cheaply as possible. The more time and money you spend trying to ensure that an X-stream project won't fail, the more the project's cost/benefit ratio deteriorates. (Maybe I'm just cynical, but I suspect we'd know more about hypersonic flight if we'd flown the X-30 through X-35 as fast-track experimental hypersonic craft, instead of spending ten years on the ground "preparing" for an X-30 that will never fly.) The X stream *will* have failures; the stream as a whole needs to accommodate this, but the individual projects should aim to succeed or fail quickly. -- "God willing... we shall return." | Henry Spencer @ U of Toronto Zoology -Gene Cernan, the Moon, Dec 1972 | henry@zoo.toronto.edu utzoo!henry ------------------------------ End of Space Digest Volume 15 : Issue 541 ------------------------------