Date: Thu, 26 Nov 92 05:04:11 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #459 To: Space Digest Readers Precedence: bulk Space Digest Thu, 26 Nov 92 Volume 15 : Issue 459 Today's Topics: "Beyond 2000" Computer synchronisation by GPS GAS (2 msgs) HST and management (was Re: Hubble's mirror) Hubble's mirror Mars Observer Update - 11/25/92 Shuttle replacement (7 msgs) Space suit research? STS Earth pix: How to view 'em What comes after DC-1 (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: Wed, 25 Nov 1992 18:56:21 GMT From: kjenks@gothamcity.jsc.nasa.gov Subject: "Beyond 2000" Newsgroups: sci.space First, hugh@whio.cosc.canterbury.ac.nz (Hugh Emberson) wrote: >> >>My mother tells me that a TV show we get here (NZ) called "Beyond >>2000" ([it's] Austrailian, but I believe that lots of countries get it) >>had a segment on DC-{X,Y,1} a couple of weeks ago. [...] To which roberts@cmr.ncsl.nist.gov (John Roberts) replied: >"Beyond 2000" is shown in the US on the Discovery Channel. It's an >interesting show, but I usually forget to watch it. :-) In the US, "Beyond 2000" is delayed at least a year behind its debut in Australia. It may be a while before we Americans see that episode. -- Ken Jenks, NASA/JSC/GM2, Space Shuttle Program Office kjenks@gothamcity.jsc.nasa.gov (713) 483-4368 "Simple systems do not evolve from complex ones." -- Henry Spencer @ U of Toronto Zoology (henry@zoo.toronto.edu), in sci.space.shuttle ------------------------------ Date: 25 Nov 92 18:50:13 GMT From: Philip Jeuck Subject: Computer synchronisation by GPS Newsgroups: sci.space In article henry@zoo.toronto.edu (Henry Spencer) writes: >The satellites just basically broadcast extremely accurate time signals >("the time is now 12:45:23.6465346533") plus current orbital positions. >Of course, what you can observe is not absolute lag, but relative lag -- >how long the signal from one satellite took relative to another -- but >with an extra satellite or two, and accurate knowledge of the orbits, >you can solve for the satellites' idea of the time and for your position. Actually once you know your position it only takes one satelite to give accurate time. That assumes that you don't change position. This is the case for most GPS receivers that are really clocks (as opposed to navigation units). >The usual sorts of synchronization protocols go to great lengths to deal >with the problem of *not* having a common absolute time reference. With >GPS, you *have* a common absolute time reference. All GPS receivers, >anywhere in the world, agree on the exact instant when the GPS system >clock reads 1:45:67.8727634 (with several more decimal places if the >receiver is a spiffy one). If your computer has a GPS receiver, and you >tell it to start processing at 11:17:05.8368461 sharp, it will start >processing in exact synchronization with any other similarly-equipped >computer that got the same instructions. An interesting footnote to this is GPS time is exactly 8 seconds ahead (behind?) UTC time. I have never seen an explanation of why. Most GPS clocks correct for this and report UTC time but not all navigation units correct for it. So if you have a receiver that was meant for positioning you might not want to use it for timing without checking it against WWV or some other source of UTC. Phil Jeuck jeuck@unix.sri.com ------------------------------ Date: 25 Nov 92 20:08:22 GMT From: Jonathan McDowell Subject: GAS Newsgroups: sci.space To: aws@iti.org Subject: Re: GAS aws@iti.org (Allen W. Sherzer): [about GAS payloads] > I believe they where halted after Chalenger [sic]. I read in a recent issue > of (I think) Space News that NASA was thinking of starting them up > again. > > I believe the payloads you speak of where [sic] just normal payloads. > > Allen > No, you are quite wrong. The point is that the *signup list* was halted after 51-L because there was a big backlog. They have been flying lots of Getaway Special payloads since then, it's just that they were all ones which were on the books since Challenger. Now that that backlog has been cleared they are taking on new orders. The payloads since STS-26R which were formally GetAway Special payloads are listed below; in addition 25 other GAS cans were flown for projects such as STP-1 and SSBUV. GAS STS Name Owner 89 G-021 40 BR Solid State M ESA 90 G-052 40 BR GTE Labs 91 G-091 40 BR OBBEX CSUN Aerospace 92 G-105 40 BR ASRC/UAH 93 G-286 40 BR Omni Mag 94 G-405 40 BR Frontiers of Sci Fdn 95 G-408 40 BR MITRE/Worcester Poly 96 G-451 40 BR NISSHO IWAI 97 G-455 40 BR NISSHO IWAI 98 G-486 40 BR Edsyn Inc 99 G-507 40 BR GSFC 100 G-616 40 BR Thomas Hancock 104 G-086 42 BR BTWashingtonHS,HoustonTX 105 G-140 42 BR DARA 106 G-143 42 BR DARA 107 G-329 42 BR SSC 108 G-336 42 BR VIPER AF Phillips Lab 109 G-337 42 BR STAR USN PGS 110 G-457 42 BR SJAC 111 G-609 42 BR ENDEAVOUR Australian Space Office 112 G-610 42 BR ENDEAVOUR 113 G-614 42 BR Chinese Soc Astronautics 116 G-229 45 GTE Labs, reflt of G051 123 G-102 47 BR Boy Scouts/TRW 124 G-255 47 BR Kansas University Space Program 125 G-300 47 BR Matra/LdGE 126 G-330 47 BR SSC Sverige 127 G-482 47 BR Spar Aerospace 128 G-520 47 BR ITN/Ashford School, Kent 129 G-521 47 BR QUESTS CSA/Queens Univ 130 G-534 47 BR NASA LeRC 131 G-613 47 BR U Wash Seattle .-----------------------------------------------------------------------------. | Jonathan McDowell | phone : (617) 495-7176 | | Harvard-Smithsonian Center for | | | Astrophysics | | | 60 Garden St, MS4 | | | Cambridge MA 02138 | inter : mcdowell@urania.harvard.edu | | USA | inter : mcdowell@cfa.harvard.edu | '-----------------------------------------------------------------------------' ------------------------------ Date: Wed, 25 Nov 1992 22:32:51 GMT From: "Allen W. Sherzer" Subject: GAS Newsgroups: sci.space In article <1992Nov25.200822.3888@head-cfa.harvard.edu> mcdowell@head-cfa.harvard.edu (Jonathan McDowell) writes: >> I believe they where halted after Chalenger [sic]. I read in a recent issue >No, you are quite wrong. The point is that the *signup list* was halted >after 51-L because there was a big backlog. I stand corrected. Thanks. However, all these experiments could have been flown on smaller and cheaper vehicles. Ditto for LDEF. We simply don't have a need for a vehicle which can return Shuttle size payloads to Earth for Shuttle prices. Allen -- +---------------------------------------------------------------------------+ | Allen W. Sherzer | "A great man is one who does nothing but leaves | | aws@iti.org | nothing undone" | +----------------------150 DAYS TO FIRST FLIGHT OF DCX----------------------+ ------------------------------ Date: Wed, 25 Nov 1992 22:44:16 GMT From: Henry Spencer Subject: HST and management (was Re: Hubble's mirror) Newsgroups: sci.astro,sci.space In article <1992Nov25.121844.1@fnalo.fnal.gov> higgins@fnalo.fnal.gov (Bill Higgins-- Beam Jockey) writes: >People on the Net, and in the general press, often praise streamlined, >low-paperwork project management... the popularity of the phrase >"skunk-works" is one example. When it works, the results are >wonderful and great value for the money... >When it goes wrong, though, the risks of this approach become >apparent... The problem here is that the skunk-works approach is *not* just fewer managers. The approach itself is not that risky; the risk comes when ignorant people use that label as an excuse for cutting costs without reforming the organization to operate effectively at lower cost. This is a confusion of appearance with substance. The same things have been said about concurrency -- developing different parts of a big high-tech system in parallel, rather than developing one and then developing the next one to fit and interoperate with the first. Concurrency became very popular after it worked spectacularly well for the Atlas ICBM and related projects. Pretty soon it became "common knowledge" that it was a risky approach that only worked now and then. Except that if you did it *the way Atlas did it*, it would work nearly every time. The problem is not that the approach is risky, but that people don't really apply the approach. The Atlas people, for example, *never* assumed that parts A and B would fit together just because the contracts said they would... yet almost every concurrent project since makes exactly that assumption. The Atlas people always had alternatives on hand in case somebody couldn't deliver on his promises -- sometimes several alternatives. Choices between alternatives were made only when testable hardware was in hand. Military procurement regulations were applied only after development problems were definitely solved. And so on. The folks who tried to copy this approach copied the appearance but not the substance. After all, copying the substance was expensive and difficult, and surely copying the appearance was enough. HST was, throughout, a NASA-style high-budget project starved for money, and applying the term "skunk works" or "streamlined" to it is simply self-deception. Setting ambitious requirements for performance and then not checking whether they're met -- in a project with no money for tests and no opportunity for a second iteration -- is not streamlining; it's stupidity. -- MS-DOS is the OS/360 of the 1980s. | Henry Spencer @ U of Toronto Zoology -Hal W. Hardenbergh (1985)| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 25 Nov 1992 22:08:01 GMT From: "David M. Palmer" Subject: Hubble's mirror Newsgroups: sci.astro,sci.space henry@zoo.toronto.edu (Henry Spencer) writes: >The point of an end-to-end imaging test, in this context, is not that >it's an easy way to detect the problem, but that it's so hard to >argue with. How do you do an end-to-end imaging test? The depth of field of an instrument with Hubble's aperture is such that a point source must be thousands of kilometers away in order to be in focus. -- David Palmer palmer@alumni.caltech.edu ------------------------------ Date: Thu, 26 Nov 1992 05:56:52 GMT From: Ron Baalke Subject: Mars Observer Update - 11/25/92 Newsgroups: sci.space,sci.astro,alt.sci.planetary Forwarded from the Mars Observer Project MARS OBSERVER STATUS REPORT November 25, 1992 11:00 PST Launch +61 Days Sequence C4 remains active on the spacecraft and is continuing without anomaly. The spacecraft was commanded to Mission Mode at 250 bits per second downlink rate at 1700 hours UTC. This was a planned activity within the stored sequence and was necessary because of telecommunication link performance roll off due to increased earth-to-spacecraft range. A new star catalog file, sun pointing target and spacecraft ephemeris file were successfully loaded onto the spacecraft today and activated. No further command activity is planned over the Thanksgiving holiday period with the exception of the standard delta DOR (Differential One-way Ranging) scheduled for Saturday, November 28th. The Magnetometer and the GRS (Gamma Ray Spectrometer) remain powered ON and the Mars Observer Camera bakeout continues nominally. The Pressure Modulator I nfrared Radiometer has had its auxilliary electronics assembly heater turned ON for the remainder of the cruise phase for thermal balance considerations. The spacecraft will remain at the 250 bit per second downlink rate throughout the remainder of the inner cruise phase, which continues until early January, 1993. The Spacecraft and Science teams both report that all subsystems and payload instruments continue to perform as expected. ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Learn to recognize the /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | inconsequential, then |_____|/ |_|/ |_____|/ | ignore it. ------------------------------ Date: Wed, 25 Nov 1992 19:43:14 GMT From: "Allen W. Sherzer" Subject: Shuttle replacement Newsgroups: sci.space In article <1992Nov25.163246.13809@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: >>Would you consider a pickup truck which only worked one day a week and >>cost $200 per mile to operate 'working hardware'? I wouldn't which is >>why I don't consider Shuttle working hardware. >When the only other available alternative is to stay home, yes I'd >consider it working hardware. I myself would ask just what I wanted to do which was worth waiting for it to be available and to pay $200 per mile for. Fortunatlly, we don't need to stay home since we have available trucks which are available almost all the time and cost $0.30 per mile. >>A range safety officer can blow up a Shuttle, not so with Delta Clipper. >Goodbye Disney World. A flying bomb with no destruct sequence isn't >acceptable. A bit less zenophobia please! what the hell do you think an airliner is? Allen -- +---------------------------------------------------------------------------+ | Allen W. Sherzer | "A great man is one who does nothing but leaves | | aws@iti.org | nothing undone" | +----------------------150 DAYS TO FIRST FLIGHT OF DCX----------------------+ ------------------------------ Date: Wed, 25 Nov 92 21:41:42 GMT From: amon@elegabalus.cs.qub.ac.uk Subject: Shuttle replacement > I think (USSR?) Shuttle is only rocket to have killed crew during > the boost phase. We've got to replace it before it happens > again. Get rid of those damn SRBs. If they're no good on a titan > then they're no good on the shuttle. Everytime I watch a launch > I find myself holding my breath for the 2 minutes it takes to > expend the SRBs. > What planet were you on on Tuesday, January 28th, 1986 when the Challenger blew about 2 minutes into ascent, killing 7 American astronauts? Buran hadn't even flown yet. ------------------------------ Date: Wed, 25 Nov 1992 20:40:13 GMT From: Magnus Redin Subject: Shuttle replacement Newsgroups: sci.space gary@ke4zv.uucp (Gary Coffman) writes: >In article henry@zoo.toronto.edu (Henry Spencer) writes: >> >>No, gliders don't burn on impact; they just go "crunch". It's still >>just about as fatal. >Actually it's not. The safety record for gliders is quite good, and they >don't burn blocks of apartments on the ground when they do smack in >like the *powered* Navy jet did in Marietta last year, or the *powered* >C-130 that *burned* the hotel in Evansville did this year, or the Israeli >jet freighter in the Netherlands. >>Neither airliners nor rockets "pinwheel across the sky when a thrust >>diverter fails". A Titan launch a few years ago had one of the core >>engines lose gimbal control and lock in position (just about hard over >>to one side, I believe it was); the other engine compensated and only >>the technical crew noticed -- the launch was successful. >But you mentioned *Harriers*, and *they* have lost thrust on one side >and *have* pinwheeled, and *have* crashed and *burned*. Helicopters, >another VTOL, also have lost tail rotors and spun into the ground. I've >covered two such crashes in the last year. The pilots would probably >have survived, if they hadn't *burned* to death. Airliners aren't >VTOL aircraft, and rockets going *up* have room for a bobble in their >course without smartly contacting the ground. Rockets coming *down* >are an entirely different issue. An engine or control failure means >a crash of a vehicle containing *rocket* fuel, perhaps miles from >intended touchdown, like main street in Disney World for example. >I'd feel a lot better if they landed these suckers at sea, far out >at sea. And that's not a crazy idea. There have been proposals for >sea launched and sea landed space vehicles. Sea Dragon comes to mind. So what? A few hundd killed kids is nothing compared with the tousands killed in traffic accidents. More serious: There wouldent be any problems if DC-1 was 100 times as unsafe as regular big jets. There are _lots_ of flights and wery few accidents. And it ought to be able to ditch in a sparsely populated area in most of the accidents. You dont need to worry, only sigh when the media shows the latest accident as the big threat to mankind. Greetings -- -- Magnus Redin Lysator Academic Computer Society redin@lysator.liu.se Mail: Magnus redin, Rydsv{gen 240C26, 582 51 LINK|PING, SWEDEN Phone: Sweden (0)13 260046 (Answering machine) and (0)120 13706 ------------------------------ Date: 25 Nov 92 21:36:21 GMT From: Brad Whitehurst Subject: Shuttle replacement Newsgroups: sci.space Allen, Just out of curiosity, what part of the DC-X do you work on? Really, I was just curious. If you are versed in the mechanical/structural end of the DC series, I was wondering how you are addressing the issue of structural robustness of the landing gear and associated airframe. From how high up is this thing supposed to survive without damage if (for instance) a sudden loss of thrust is experienced? I recall that structural integrity and resistance to low cycle fatigue without excessive weight is an old bugaboo in aircraft landing gear. On a civil jet I guess it is not so bad, but weight is almost always a big factor with military jets' gear. Basically, I guess some of your comments seem like a toss-off: "Hey, this is easier than building a jet" whereas even civil jets sometimes take agonizing months or years to get certificated. I think there's a lot of good ol' mechanical gremlins lurking in the shadows when you try scaling this thing up, then operating it like a "space truck". -- Brad Whitehurst | Aerospace Research Lab rbw3q@Virginia.EDU | We like it hot...and fast. ------------------------------ Date: Wed, 25 Nov 1992 22:19:34 GMT From: Henry Spencer Subject: Shuttle replacement Newsgroups: sci.space In article <1992Nov25.161848.13706@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: >>No, gliders don't burn on impact; they just go "crunch". It's still >>just about as fatal. > >Actually it's not. The safety record for gliders is quite good, and they >don't burn blocks of apartments on the ground when they do smack in >like the *powered* Navy jet did in Marietta last year, or the *powered* >C-130 that *burned* the hotel in Evansville did this year, or the Israeli >jet freighter in the Netherlands. I was thinking of fatalities to those on board. I guarantee you that a 750,000lb glider would kill people if it hit an apartment block, although not quite as many as a 747 heavy with fuel. (Whether the 747's engines were running is quite irrelevant. In fact, that particular 747's *problem* was that it was half glider.) Certainly if that had been a returning shuttle orbiter, it would have killed a lot of people -- between fire and poisoning -- even though the orbiter itself was gliding. Please don't compare light sporting aircraft that fly only in good weather with operational commercial cargo/passenger aircraft that are two orders of magnitude larger. >>Neither airliners nor rockets "pinwheel across the sky when a thrust >>diverter fails"... > >But you mentioned *Harriers*, and *they* have lost thrust on one side >and *have* pinwheeled, and *have* crashed and *burned*. Helicopters, >another VTOL, also have lost tail rotors and spun into the ground... The problem of both systems is that crucial parts are not redundant. This is nothing new, and the problem is *not* restricted to VTOLs. The F-111 that lost a wing pivot, early in the program, pinwheeled too. The problem is inadequate redundancy in lift producers, not VTOLness. The DC designs are a great deal more redundant than either Harriers or helicopters. They can lose an engine -- or have to shut one down due to something like a gimballing malfunction -- and carry on. This is one of the virtues of really powerful engines. >... Airliners aren't VTOL aircraft... Some large commercial helicopters are certified as airliners. The FAA has no particular objection to certifying VTOL airliners, it's just that nobody has yet built one. Let's not forget the Chicago DC-10 crash, which a reasonably redundant VTOL would have survived -- they don't have asymmetric slat failures. Nor do they have icing problems. Microbursts don't bother them. Nor does wake turbulence. Underpowered vehicles that rely on wing lift are very sensitive to the slightest problem with their wings or the airflow over them. This causes many crashes. >...rockets going *up* have room for a bobble in their >course without smartly contacting the ground. Rockets coming *down* >are an entirely different issue. An engine or control failure means >a crash of a vehicle containing *rocket* fuel, perhaps miles from >intended touchdown, like main street in Disney World for example. Or like that apartment block in Amsterdam, where a non-VTOL airliner made a horrendous mess. We're *already* flying things loaded with many tons of fuel around urban areas, and they're things that are much trickier to land than a VTOL rocket. Note that a DC coming down will have not much more fuel in its tanks than a typical light aircraft. Almost all the fuel gets burned on the way *up*. -- MS-DOS is the OS/360 of the 1980s. | Henry Spencer @ U of Toronto Zoology -Hal W. Hardenbergh (1985)| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Wed, 25 Nov 1992 22:20:41 GMT From: Henry Spencer Subject: Shuttle replacement Newsgroups: sci.space In article <1992Nov25.163246.13809@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: >>A range safety officer can blow up a Shuttle, not so with Delta Clipper. > >Goodbye Disney World. A flying bomb with no destruct sequence isn't >acceptable. Have you told the FAA about this? They've certified many types of airliners for flight with very full tanks and no destruct systems. -- MS-DOS is the OS/360 of the 1980s. | Henry Spencer @ U of Toronto Zoology -Hal W. Hardenbergh (1985)| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Wed, 25 Nov 1992 23:47:22 GMT From: "Gregory N. Bond" Subject: Shuttle replacement Newsgroups: sci.space.shuttle,sci.space >>>>> On Tue, 17 Nov 1992 20:46:55 GMT, aws@iti.org (Allen W. Sherzer) said: aws> As I understand it you can scale up to some degree. What are the limits on scaling up something like DC-Y? My intuitive guess would be that scaling up should be _easier_: - The square-cube law should help reduce tank mass/propellant mass ratios and similarly for other sturctural members. - Avionics, crew, life support mass should be pretty much constant. - In a DC-type design, larger units would have more engines, which implies greater redundancy and perhaps mass savings by removing the need for some duplicated hardware and general fault-resistance. [i.e 1 engine might need elaborate and expensive backups, with 4 engines you could do away with the backups and wing it on 3 engines in the event of failure, so total mass/cost is less than 4x the single engine.] What am I missing? Greg. -- Gregory Bond Burdett Buckeridge & Young Ltd Melbourne Australia ``There is Faith, Hope and Charity. But greater than these is Banking.'' - 1492 ------------------------------ Date: 25 Nov 92 21:11:00 GMT From: Steve Willner Subject: Space suit research? Newsgroups: sci.space In article <17722@mindlink.bc.ca>, Bruce_Dunn@mindlink.bc.ca (Bruce Dunn) writes: > Another useful data point might be the experience at the Mauna Kea > observatories at ca. 15,000 feet altitude. I believe that one of the > telescopes has oxygen-enriched working areas because of problems suffered by > astronomers who have not acclimatized. The altitude is just below 14,000 feet (4250 m). Oxygen-enriched areas have been talked about but never implemented as far as I am aware. Acute physical symptoms are rare among full-time staff, common but seldom severe among visiting astronomers. Impaired judgement, however, is almost universal among both staff and visitors. Working at the mid-level facility (about 2700 m) or on other mountains of this altitude is vastly less difficult, though problems occasionally occur. -- Steve Willner Phone 617-495-7123 Bitnet: willner@cfa Cambridge, MA 02138 USA Internet: willner@cfa.harvard.edu member, League for Programming Freedom; contact league@prep.ai.mit.edu ------------------------------ Date: 25 Nov 1992 20:18:24 GMT From: Greg F Walz Chojnacki Subject: STS Earth pix: How to view 'em Newsgroups: sci.space,sci.astro I've gotten some of the photos of Earth taken from the Shuttle (the ones available on sseop.jsc.nasa.gov). The question is, how to view them? Has anyone had any success at this? Also, has anyone been able to move into other directories? There are allegedly more images in another directory, but the system is opaque to me. Thanks for any help. greg ------------------------------ Date: Wed, 25 Nov 1992 19:14:39 GMT From: Dean Reece Subject: What comes after DC-1 Newsgroups: sci.space I realize the DC-1 is still being spec'd, but I have a few questions about how versatile the system will be. Don't worry, I'm not trying to turn DC-1 into a Do-All for Everybody like the Shuttle (which became a do-little for a few). Specifically, I'm curious how this system will evolve if it provides everything it promises. If it works well, it's a safe bet that DC-1 derivatives will be built. How long can the DC-1 stay on orbit? Will the Cryo fuels boil off? How hard (how many mods) would need to be made to re-fuel a DC-1 on orbit? Assume the fuel is there for starters. What is the highest (circular) orbit that the DC-1 can attain if it doesn't need to worry about fuel for landing? GEO? Is there any technical reason that a DC-1 couldn't make it to the moon if it could be fully re-fueled at this (maximum) orbit? Hard radiation, Too much thermal stress...? Assuming fuel stores (or production) on the moon, could the DC-1 support its own weight fully fueled on luna, or would a launch cradle need to be constructed there? Would it be able to return to Earth on a single fillup, or would it need to attain Earth orbit and refuel again? Again, assuming high orbit refueling, could DC-1 make Mars? Could it return? (a 1 way trip might still be plenty useful if the DC-1 is in mass production and fairly cheap, compared to a custom Mars lander) Could we strap on SRB's to the DC-1 to increase payload (bad joke... forget I said it :-) I realise that its a bit early to answer these questions with any certainty, but any serious thoughts on these questions would be appreciated. -Dean Reece (deanr@sco.com) ------------------------------ Date: Wed, 25 Nov 1992 22:46:35 GMT From: "Allen W. Sherzer" Subject: What comes after DC-1 Newsgroups: sci.space In article deanr@sco.COM (Dean Reece) writes: >I realize the DC-1 is still being spec'd, but I have a few questions >about how versatile the system will be. Don't worry, I'm not trying to >turn DC-1 into a Do-All for Everybody like the Shuttle (which became a >do-little for a few). Actually, a working DC1 would be a very adaptable vehicle. Only minor mods would be needed to make it an OTV or a Lunar transit vehicle. >Specifically, I'm curious how this system will evolve if it provides >everything it promises. If it works well, it's a safe bet that DC-1 >derivatives will be built. Eventually. The market may not be quite big enough. One advantage of DC1 is that it can pay for its own final development and, unlike alternatives like Spacelift, small increases in market size will produce much lower costs. >How long can the DC-1 stay on orbit? Will the Cryo fuels boil off? As currently speced out, only a few days. I don't know about boil off. >How hard (how many mods) would need to be made to re-fuel a DC-1 on >orbit? Assume the fuel is there for starters. The Russians refuel on orbit so I assume not much. >What is the highest (circular) orbit that the DC-1 can attain if it >doesn't need to worry about fuel for landing? GEO? I wold guestimate 250 miles or so. That's little more than a WAG. >Is there any technical reason that a DC-1 couldn't make it to the moon >if it could be fully re-fueled at this (maximum) orbit? Hard radiation, >Too much thermal stress...? A DC1 fully fueled in LEO should be able to take and return 10K pounds to the moon. It may need a pad when it gets there although I assume one could add landing legs like the LM. This assumes no solar flares on the trip. DC1 wo't have near enough radiation protection. >Again, assuming high orbit refueling, could DC-1 make Mars? Not likely. There isn't enough shielding. Besides, the payload bay is too small to live in for years at a time. >Could we strap on SRB's to the DC-1 to increase payload (bad joke... >forget I said it :-) Well, people have proposed it (not SRB's but strap ons). It defeats most of the purpose and adds cost but it might be worth while if DC1 turns out to be more marginal than expected. >I realise that its a bit early to answer these questions with any >certainty, but any serious thoughts on these questions would be >appreciated. Remember that DC1 isnt' on the drawing boards yet. Nobody can say for sure what the requirements will be. Alen -- +---------------------------------------------------------------------------+ | Allen W. Sherzer | "A great man is one who does nothing but leaves | | aws@iti.org | nothing undone" | +----------------------150 DAYS TO FIRST FLIGHT OF DCX----------------------+ ------------------------------ End of Space Digest Volume 15 : Issue 459 ------------------------------