Date: Thu, 17 Dec 92 05:08:06 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #560 To: Space Digest Readers Precedence: bulk Space Digest Thu, 17 Dec 92 Volume 15 : Issue 560 Today's Topics: : Relay to Follow Galileo? absolutely, positively overnight DC vs Shuttle capabilities Does Sun have magnetic poles? fast-track failures (2 msgs) Greek jet engine (Was: Terminal Velocity of DCX?) Private Phisical Inst. seeks collaboration in different forms and directions Shuttle alternatives (was Re: Terminal Velocity of DCX?) SSTO vs. 2 stage Terminal Velocity of DCX? (was Re: Shuttle ...) (4 msgs) what the little bird told Henry 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: 16 Dec 92 21:41:58 GMT From: David Seal Subject: : Relay to Follow Galileo? Newsgroups: sci.space In sci.space it is written: >>But we're talking about a multi-Billion dollar program here. I just >>wouldn't want to take that risk. That is a lot of money the throw away >>because the "stupid" antanna won't open.. And this will further make the >>image of NASA tarnish even more. Yet another American blunder.. we don't >>need it. How are we going to argue that we need to go to this planet and >>that planet if we can't build the hardware to do the job??? >> >> >> -- Ryan Korniloff >> -- rkornilo@nyx.cs.du.edu >The folding, umbrella-type antennae have been used at least ten times >in space (that is, two each on TDRS-A, TDRS-C, TDRS-D, and TDRS-E, one >on ATS-6 (late-70s pathfinder comsat) and one on Galileo. > >Only the one on Galileo failed to open on command, and there is still >hope it will be coaxed open. (They haven't tried brute force yet.) >Lesson: OPEN THE DAMNED ANTENNA IMMEDIATELY AFTER LAUNCH!!! >-Brian Let me add a brief spout: It is always easy after a failure (with 20-20 hindsight) to say 'jeez, how stupid. why the heck couldn't you just have done X instead?' from my POV, there are a billion things that can go wrong that can royally screw up a mission, and you try to avoid the major ones, and the ones you can eliminate easily (i.e. w/o $$ or complexity or exhaustive analysis). I think the view of space mistakes can be somewhat overblown because a lot of people (not necessarily Ryan, just in general) don't really understand how difficult it is to do what we do. The HGA looked like a good choice. It had performed well in a space environment previously. And the test program was supportive. But it happened anyway. It may look easy to you with hindsight, but don't think for a second that the project staff of Galileo is kicking themselves because they picked a 'stupid' design. also: the next attempt is the dec. 28 ballscrew hammering. it is not what i would call 'coaxing.' from now on, it is brute force that will be used. I've heard they might even yield the pins or the antenna ribs during the hammering. (this, of course, would be fine. any portion of the fully deployed HGA bigger than a paper plate would probably provide better performance than the LGA). also: from what i know, opening the antenna immediately after launch would probably have had the same result. the problem was that the lubrication in the pin mountings had worn away during transport and/or launch. i think. regards, ds standard disclaimers and all that. -- ----------------------------------------------------------------------------- David Seal | Jet Propulsion Laboratory | sunset: 7:54pm seal@leonardo.Jpl.Nasa.Gov | Mission Design | temp: 82 degrees ------------------------------ Date: 16 Dec 1992 21:54:34 GMT From: Pat Subject: absolutely, positively overnight Newsgroups: sci.space In article ewright@convex.com (Edward V. Wright) writes: > >"Air Force One" is just a call sign for whatever plane the President >happens to be riding in. The Air Force has an entire squadron of planes >which, at one time or another, may be Air Force One. The big 707 (now >747) is the most famous, but not every trip requires something that >large. > Well, when he is being flown around in his Sikorsky to andrews and the white house, then he is in ?Marine One". I know the army has a small helicopter detachment to fly him around and i bet then it's "Army One". So if the Navy buys the first executive DC, then it will be Navy One that goes globe-trotting. ------------------------------ Date: 17 Dec 92 03:14:06 GMT From: Greg Moore Subject: DC vs Shuttle capabilities Newsgroups: sci.space In article <1992Dec14.175934.5993@iti.org> aws@iti.org (Allen W. Sherzer) writes: >In article strider@clotho.acm.rpi.edu (Greg Moore) writes: > >First of all, which crew? The flight crew rides in the cockpit which is >above the cargo bay. If more crew are needed, then the satellite can >ride in the part of the cargo bay not used by the extra crew. > Sorry, my mistake, I got confused on the crew accomodations of the proposed DC-1. Another question though: Am I correct in recalling that the goal is to use pilots, and not astronauts (at least in the NASA sense) to fly the proposed DC-1? Who will do satellite repair? Who pays for training? The customer, or will McD (or whoever operates it) have "on-call techs" that you can pay extra for. (I'm not calling for you to predict the future (thouh seem to believe at times you know it... :-) just an idea if SDIO has given this any thought? >If it turns out that this isn't roomy enough, then you use the technology >developed under DC to build a larger vehicle. After all, DC will be a usefull >piece of technology but it isn't the only spaceship which will ever be built. > But wait, DC-1 was going to solve all my problem, and slice my bread. Seriously though, I think this leads to a comment directed to you, Gary, Michael, and Edward and any others I've forgotten. We've all argued various merits, benefits and drawbacks of the DC program, but sometimes I think we forget what we are talking about. Are we talking about DC-X, the planned DC-Y, or the proposed DC-1. It seems to me that everyone here agrees that DC-X is a good idea, whether or not it works. As long as it is treated like an X program, it seems to get a lot of support. We will learn from it. Perhaps we will find everything will be as "easy" as they say, or perhaps they run into stumbling blocks. But we won't nkow until we try. DC-Y doesn't seem to be of much conflict per se. I think we differ big-time when it comes to DC-1. Allen seems to me to be saying, "Things will work out, and this is how it will be." I think that is the attitude that bothers me the most. That is the exact same thign that was said with the Shuttle. NOw granted, there are some major difference, major enough to make me believe that DC-1 has a better chance than the Shuttle did. However, we can't be sure until we start FLYING these things. A better way of thinking may be, "If things work out, this is how it will be." I don't mean to pick out you Allen, and I don't mean to pick on your belief in the DC-X program, but sometimes it seems to me you're trying to sell it before it's tested. Off the soapbox. >> I eliminated some stuff above, but wanted to add some stuff here. >>Actually, plummeting launch costs may contribute to lower payload costs >>since people will be willing to build a less fault tolerant system >>knowing that if it fails, they can launch another cheaply. > >Exactly. > Ah, we agree. That's nice to hear. :-) >>As for on-site repair, for now DC-? fails for the same reason that >>the Shuttle normally does, it can't get up to GEO, you need a OTV... > >Although a DC with a robot arm and some avionics changes may be the >OTV. Certainly the engines for a DC will be just what an OTV needs. > Is this inherent in the RL-10 design, or does work need to be done on the tanks to make sure the fuel is near the outlets? >>>> Also, as for retrieval, the Shuttle has shown that it ain't >>>>easy to do. Will a two day on-orbit time be enough? > >>>It may take modifications to the DC. At the very least you need to add >>>a robot arm and an airlock. > >> Granted, but that's not what I meant. Will you have enough time >>to rendevous and capture the satelite? It took what 3 days for the >>shuttle to capture Intelsat VI? That's aday more than DC-?. > >Load the pallet with some extra power sources, add some solar cells and >your all set. > So, your pallet now has attachments for consumables that DC-1 can draw on? (Hmm... let's just use a EDO... Oops, no, ITWIH Syndrome. :-) (Seriously, I know, it probably won't fit.) >>Also, what type of fuel margin would DC-1 have for IN-orbit >>manevours? > >DC-Y has a fair amount of fuel for on orbit delta V but I don't >remember the exact numbers. How much DC has will depend on the >design requirements and who pays the bills. > >But note that on a DC-Y you can power the fuel cells, main engines, and >RCS from the same source. This allows you some very powerful tradeoffs. > True, but I'd still like to have a separate fuel reserve or power supply. >>(I realize it has enough for landing, and of course >>you don't wnt to cut into that for safety reasons.) > >At least enough to get back to the orbital fuel dump. > Oh, gee, I didn't realize we had one. And what if it isn't in your orbital plane? Might was well re-enter... >> Use it yes, but use it for what it can be used for economically. >>Let's see, we've added an airlock, an arm, additional on-orbit capacity. >>Hmm, that adds up, and add complexity. Yes, let's ok at possibilities, >>but not claim t they are definites. > >Agreed. But they don't look all that hard given a working DC. > And they didn't look all that hard given a working shuttle. Hmm, RMS came from Canada, and even at that was a bargin. So I'm sure DC can use one. Airlock, that's simple enough. On-orbit capacity: That's a little tougher. Depends on how your DC is scarred, etc. BTW, what is the FAA say about adding fuel tanks. I know the 747-400 didn't have to be completely recertified... I'm sure DIC won't have to be either, but I'm sure there would have to be some testing. Sounds good. Prove to me it works with flying hardware, and I'm sold. >> Also, does it make sense for the DC1-EOT and OMV and LM the same. > >Not 100% the same. For an OMV I would strip off the thermal protection >system, add attach points outside for additional fuel and hardware (like >arms), I might look at lining it with solar cells for more power. For a LM >I think you would need to provide better insulation to reduce fuel boil off, >replace the landing gear to give it a larger footprint (like the Apollo LM), >and beef up the TPS for aerobreaking. > Beef up the TPS how much? Also, I believe that Henry pointed out that it ieasier to do a direct re-entry than a return to orbit. (I can't recall why, and wasn't celar at the time I read it, so I may be wrong.) If so, will you have enough fuel to do this. Remember, until you have your moonbase set up, you've got to leave LEO, land on the moon, take off, and either re-enter, or re-enter LEO. Now your changing your landing gear. How, what does this entail? >This will allow us to use the same core vehicle for multiple applications >which will allow development to be amortized over more vehicles and reduce >construction costs since we are building more core vehicles. > Ayup, and if we had built Shuttle-C, we could have amortized engine costs a tad more, and amortized facility costs more. > Allen > >-- >+---------------------------------------------------------------------------+ >| Allen W. Sherzer | "A great man is one who does nothing but leaves | >| aws@iti.org | nothing undone" | >+----------------------131 DAYS TO FIRST FLIGHT OF DCX----------------------+ ------------------------------ Date: 16 Dec 92 21:47:06 GMT From: Stephen Tell Subject: Does Sun have magnetic poles? Newsgroups: sci.physics,sci.electronics,sci.space In article sehari@iastate.edu (Babak Sehari) writes: >Recently, an attempt has been made to create electricity using a large >electric loop in the space using earth magnetic force. However, such thing >should not be a source of energy in the space since it takes energy to >change the flux that passes through wire loop and only a fraction of that >energy would be translated to electric energy. Further more, if the rotation >of satellite itself to be used for this task, the emf back force would change >the speed of the satellite. That results in altitude drop for satellite. If I may be allowed to suggest in a serious forum an idea I first saw in a piece of fiction, from David Brin's short story, "Tank Farm Dynamo" (found in the Brin anthology "The River of Time" and perhaps elsewhere): Generate your electricity using photovoltaics or somthing else, and use the large loop in the Earth's field as a motor, not a generator. This boosts your altitude. The satelite in the story was an orbiting tether with an elevator running up the cables. Payloads would be carried up and down, with more net mass going up than down, which over time would lower the altitude of the satelite by significant ammounts. Use of the magnetic effect countered this tendancy. > Babak Sehari. -- Steve Tell tell@cs.unc.edu H: 919 968 1792 | #5L Estes Park apts UNC Chapel Hill Computer Science W: 919 962 1845 | Carrboro NC 27510 Engineering is a _lot_ like art: Some circuits are like lyric poems, some are like army manuals, and some are like The Hitchhiker's Guide to the Galaxy.. ------------------------------ Date: Wed, 16 Dec 1992 18:48:07 GMT From: "Edward V. Wright" Subject: fast-track failures Newsgroups: sci.space In <1992Dec14.145351.14521@ke4zv.uucp> gary@ke4zv.uucp (Gary Coffman) writes: >Yeah, bad line of argument, most of the systems that made it as far >as being assigned a number weren't technical failures even if they >were market failures. Actually I was thinking of the P-39 when I >wrote that. That aircraft made it into production, but was a dismal >failure... This was an example of >fast tracking from a prototype to production without working out >all the bugs required to make it a practical fighter. And how long did it take before the P-39 was succeeded by a fast-track replacement? And how many generations of fighters did the US go through in the next 15 years (the time it takes to develop one fighter today)? There's a moral here. Do it fast, do it quick, do it cheap. Take risks and being willing to *accept* an occassional failure. If a project does fail, forget the finger pointing, the blame casting, and the Congressional investigations, just get on with the next one. Don't put all your eggs in one basket. And staff your projects with competent people motivated by *success*, not failure-oriented "engineers" who spend all their time generating cover-your-butt paperwork. ------------------------------ Date: 16 Dec 1992 22:33:51 GMT From: Pat Subject: fast-track failures Newsgroups: sci.space In article <1992Dec14.145351.14521@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: >In article henry@zoo.toronto.edu (Henry Spencer) writes: >> >>Just which aircraft were you thinking of, Gary? I can think of one >>aircraft that had a bad performance shortfall but was redesigned and >>continued into a successful program (the F-102). I can't think of >>*any* F-series "gap" in the last 40 years that fits your description. > >were market failures. Actually I was thinking of the P-39 when I (Stuff deleted) Actually another case was the YB-49 and YB-50? those were northrops flying wing prototypes, the turbo-prop and the jet versions. They actually flew but had trouble with range, and power. the prop job needed twin counter rotating props to really develope thrust. Plus there were enormous political problems witht he Air Force on the birds. Too bad, the effort broke jack northrop and he never got to see his vision carried off in the B-2. ------------------------------ Date: Wed, 16 Dec 1992 19:22:57 GMT From: GRASSO CHRISTOPHER A Subject: Greek jet engine (Was: Terminal Velocity of DCX?) Newsgroups: sci.space In article 26326, (Edward V. Wright) writes: >I think the ancient Greeks, who built a working jet engine, >lived a little more than 50 years ago. Interesting. Would you care to elaborate? -Chris Grasso CU Boulder ------------------------------ Date: Wed, 16 Dec 92 19:21:38 +0300 From: "Aleksandr V. Kats" Subject: Private Phisical Inst. seeks collaboration in different forms and directions Newsgroups: sci.space Dear Sir, Works of private little venture Eco-Energy Institute are directed in general for ecology clean possibility of energy production, conservation and utilisation. We are interested in collaboration, the orders of some criogenic devices and osonators, and joint investigations. Suppose, that it is reasonable to have the discussions and meetings with investigators, working in following directions: 1. NASA programs of metastable helium states (MHS) as a rocket propellant and of moon He3 utilisation, MHS manufacturing, conservation and utilisation. 2. Weakly bound species: helides, rare gas - hydrogen - and carbohydryde clusters, now wellknown foullerens,for example, - the manufacturing of its. 3. Ozone generation, conservation and utilization. All theese ones may be used as energy accumulated species, but not only, ofcourse . 4. The plasmoreactor methods of hydrogen from water and H2S production. 5. Scintilators for nuclear and cosmic radiation detecting - some unusual methods of manufacturing, examination and testing. 6. Mathematical modelling of dust ewolution and grouing in air on the base of Smoluhovsky equations. We are interested to take part in the experimental work on the base of US organisations in all this fields. In all this directions we have ideas, know-hows, skill, experience, patents. Now the negotiations, concerning 4 and 5 items, with some US Universities are in progress. We would like to have grants and other forms of collaboration for our researchers, working in this directions. S.Y. D. Myshkis, Director of Eco-Energy Institute Ph.D, Mb.of RAN Commitee for Energy Accumulating Species Using Ukraine, 310103, Kharkow, ul.Kosmonavtov,5A/77. tel.+7-(057)-2-727666 fax +7-(057)-2-324677 ------------------------------ Date: Wed, 16 Dec 1992 22:25:00 GMT From: "Michael V. Kent" Subject: Shuttle alternatives (was Re: Terminal Velocity of DCX?) Newsgroups: sci.space In article <1992Dec16.195416.8422@iti.org> aws@iti.org (Allen W. Sherzer) writes: >That is my point. Your point is a moving target, but I'll do my best to adress its major aspects. Point 1: In the beginning of this mini-thread, Allen stated that for the cost of one Shuttle flight, NASA could develop DC-X and launch whatever was to go up on the Shuttle on a Titan IV. This is not true primarily because Titan IV cannot carry most Shuttle pay- loads. 1) Titan IV cannot carry the payload of the Shuttle. Titan IV's payload is only 38,500 lbs to a 100 nmi orbit, while Discovery and Atlantis can loft 52,000 lbs to a 150 nmi orbit. Endeavour can launch a few thousand lbs more. While I don't have the equations on hand, raising Titan IV's standard orbit to 150 nmi would cause its payload to drop to about 30,000 lbs, barely half that of Endeavour. 2) Shuttle is the only manned spacecraft we have. An astronaut will not sur- vive long in a Titan IV payload fairing, as the fairing has no life support system. This is important for the middeck payloads, Spacelab, and Spacehab. It is also important for satellite servicing missions where astronaut pres- ence is required for primary (Intelsat, Hubble servicing) or contingency (Hubble, Compton deploy) purposes. 3) Titan IV has no return capability. This is important for all astronaut operations, and is required for satellite retrieval missions. It is also required for SPAS, USMP, and many GAS and middeck payloads where either samples need to be returned for study or the entire system needs to be re- turned for refurbishment. 4) Much Space Tranportation System hardware requires the Shuttle explicitly, or one of the above attributes. Spacelab and Spacehab, for example, require the Shuttle for life support, power, and heat rejection. Other hardware elements requiring the Shuttle are the Spacelab pallets, the RMS, and most middeck payloads. 5) The Titan IV's launch rate is very low. It has flown six times since its 1989 debut, while the Shuttle has flown over 20. All available Titan IVs for the near future will be used for launching Air Force payloads. None are available for NASA or commercial uses for quite some time. Conclusion: Whether or not the cost of a Titan IV launch plus the cost of DC-X is less than the cost of a Shuttle flight, the point is moot, since nearly all Shuttle payloads require some aspect of the Shuttle that is unique to the Shuttle. For these five reasons, a Titan IV flight can not substitute for a Shuttle flight. Point 2: STS-52 could have flown on a $10 million Pegasus. I have addressed this in another post, so I will just post the conclusion here. Conclusion: Point 2 is simply not true. Point 3: >For what we have spent on Shuttle we could have built two Freedom >space stations or about 20 or so Industrial Space Facilities. Utilization >of either of these would be hundreds of times greater than Spacelab providing >hundreds of times the chance to fly important experiments. This is a highly speculative point, since it involves analyzing the politics of the early and mid 70's, but it can on the surface be proven false for one simple reason: Space Station Freedom (or any reasonble space station) requires the Shuttle to launch. There are two things unique to the Shuttle that are required to build SSF. The first is heavy-lift capability (relatively speaking, of course), and the second is manned spaceflight. Neither would have been available without the Shuttle. The Saturn V, the Mercury and Gemini capsules, and the Apollo hardware were all already cancelled when the space shuttle came into being in 1972. They were NOT cancelled to fund the Shuttle. In fact, the cancell- ation had a large impact on the configuration of the Shuttle, as it had to assume the roles of much of the cancelled hardware. Without the Shuttle, there would be no heavy lift (even the Titan IV didn't come into being until 1989) and no manned spaceflight. Any space station would require either one or the other (or both) to launch and assemble in space. There could be no SSF without the Shuttle, and since ISF requires man-tended operations, there could be no ISF without the Shuttle either. Conclusion: Since the Shuttle is a pre-requisite for SSF and ISF, neither could be built at the expense of the Shuttle. Point 3 is false. There were (note past tense) alternatives. Other hardware could have been built to meet the needs of heavy-lift and manned spaceflight. This is where the speculation comes in. But whatever could have been built would have had to face the same Nixon administration, the same OMB, and the same Congress as the Shuttle did. To say that any system able to meet the needs of heavy lift and manned spaceflight would have had vastly different political accept- ance in the early 70's, in my opinion, is pure speculation. All speculation aside, we have TODAY a hardware mix that has useful capabil- ities. How we use those capabilites today and how we expand them tomorrow are far more important issues than speculation on what might have been. Mike -- Michael Kent kentm@rpi.edu Flight Test Engineer Tute-Screwed Aero '92 McDonnell Douglas Rensselaer Polytechnic Institute These views are solely those of the author. Apple II Forever !! ------------------------------ Date: Wed, 16 Dec 1992 19:25:16 GMT From: "Edward V. Wright" Subject: SSTO vs. 2 stage Newsgroups: sci.space In <18585@mindlink.bc.ca> Bruce_Dunn@mindlink.bc.ca (Bruce Dunn) writes: > If a DC-1 in SSTO mode can launch 10 tons to LEO and the two stage >vehicle using the DC-1 as an upper stage can launch 50 tons to LEO, then we >have the following costs for launching 50 tons: >DC-1 in SSTO mode: 5 flights needed, incurring 5 DC-1 stage turnaround costs >DC-1 in 2 stage mode: 1 flight needed, incurring 1 DC-1 stage turnaround and >1 lower stage turnaround cost. The 2-stager is a *much* larger vehicle, so your vehicle fabrication costs will be much larger. > I will assert that turnaround cost of the lower stage will not exceed >the turnaround cost of the upper stage (the lower stage is much less stressed >than the DC-1 upper stage, and uses cheap kerosene and LOX as propellants). Think again. The SSTO recovers back at the launch site. Your first stage will splash-down or land somewhere downrange. It needs to be retrieved, safed, and returned to the launch site before it can be used again. This is not only expensive, it's time consuming. You're going to need a lot of extra stages to make up for the down time. Mating the two stages will take time and manpower also. Using a different propellent in the first stage means you're going to have to invest in another set of propellent storage and loading facilites. Fueling will be more complex, requiring more time and manpower. >Therefore, as far as turnaround costs go, the two stage vehicle costs 2/5, or >40% as much as the SSTO. That doesn't follow from anything you've said up til now. Your second stage is a DC-1, so that's 100% right there. The first stage, being much larger, will be a lot more. > A final advantage to the two stage design comes from the time >necessary to perform turnaround. Since the lower stage can be inspected and >prepared for another flight while the upper stage is making an orbital >delivery, the frequency of flights will be governed by the turnaround time of >the upper stage after it gets back. Only if the first stage can teleport. >Say that turnaround time is 1 week. If you spend your money on two DC-1 >vehicles and operate them in the SSTO mode, then it will take 5 weeks to >put 100 tons in orbit (two flights delivering 10 tons each per week). Or 5 days, flying two flights per day. >If you spend your money on one DC-1 and 1 lower stage, then the same >100 tons can be put into orbit in two weeks (two flights, each >delivering 50 tons). Of course, you'll only have enough money to pay for half the first stage. ------------------------------ Date: Wed, 16 Dec 1992 19:39:29 GMT From: "Michael V. Kent" Subject: Terminal Velocity of DCX? (was Re: Shuttle ...) Newsgroups: sci.space In article <71780@cup.portal.com> BrianT@cup.portal.com (Brian Stuart Thorn) writes: I said this: >>What I don't believe is that you'd get any knowldgeable >>volunteers to fly a Spacelab mission on a Titan IV. >Ever hear of the "Manned Orbiting Laboratory"? A Gemini with a very >Spacelab-like module launched together by Titan III. Yeah, I've heard of it. I've also heard that it was cancelled about 25 years ago, and that none of them ever flew. Spacelab is very dependent on the Shuttle for life support, power, and heat rejection. You couldn't fly it on a Titan IV (which was my point). Mike -- Michael Kent kentm@rpi.edu Flight Test Engineer Tute-Screwed Aero '92 McDonnell Douglas Rensselaer Polytechnic Institute These views are solely those of the author. Apple II Forever !! ------------------------------ Date: Wed, 16 Dec 1992 18:41:12 GMT From: Paul Dietz Subject: Terminal Velocity of DCX? (was Re: Shuttle ...) Newsgroups: sci.space In article <1992Dec16.143834.533@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: > The load on a pump also increases linearly with the volume of material > it has to move. Naturally I was assuming larger combustion chambers for > the low pressure design so that the mass flow, and thrust, remained nearly > the same. The two designs lead to different stresses, though. A low volume, > high pressure pump has different failure modes than a low pressure, high > volume pump. One is not necessarily better than the other. But, Gary, while the volume of the combustion chamber is indeed larger in the low chamber pressure case, the volume rate of consumption of liquid propellant is very nearly the same, for a given thrust. The pumps are pumping liquid fuels -- whose density is independent of the chamber pressure -- and the low pressure engine needs to pump only slightly more than the high pressure engine for a given level of thrust (because of its slightly lower Isp). You do *not* have to pump twice as much fuel if the chamber pressure is reduced by half. Given that the volumes of fuel to be pumped are nearly the same, the low pressure engine will require less powerful pumps. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Wed, 16 Dec 1992 19:54:16 GMT From: "Allen W. Sherzer" Subject: Terminal Velocity of DCX? (was Re: Shuttle ...) Newsgroups: sci.space In article kentm@aix.rpi.edu (Michael V. Kent) writes: >Spacelab is very dependent on the Shuttle for life support, power, and heat >rejection. You couldn't fly it on a Titan IV (which was my point). For what we have spent on Shuttle we could have built two Freedom space stations or about 20 or so Industrial Space Facilities. Utilization of either of these would be hundreds of times greater than Spacelab providing hundreds of times the chance to fly important experiments. That is my point. Allen -- +---------------------------------------------------------------------------+ | Allen W. Sherzer | "A great man is one who does nothing but leaves | | aws@iti.org | nothing undone" | +----------------------129 DAYS TO FIRST FLIGHT OF DCX----------------------+ ------------------------------ Date: Wed, 16 Dec 1992 20:12:55 GMT From: "Michael V. Kent" Subject: Terminal Velocity of DCX? (was Re: Shuttle ...) Newsgroups: sci.space In article <1992Dec16.105749.28318@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: >Uh wait, didn't you post that SDIO's DCX program cost totalled $1.2 billion? The DC-X contract was for about $58 million. SDIO is accruing additional costs at its NPO, but since the entire NPO is one three-man team, I doubt that's very much. I think the DC-Y effort was for $1.2 billion (this sounds low to me, but I can't dispute it). Mike -- Michael Kent kentm@rpi.edu Flight Test Engineer Tute-Screwed Aero '92 McDonnell Douglas Rensselaer Polytechnic Institute These views are solely those of the author. Apple II Forever !! ------------------------------ Date: 16 Dec 92 23:18:09 GMT From: Steinn Sigurdsson Subject: what the little bird told Henry Newsgroups: sci.space In article ewright@convex.com (Edward V. Wright) writes: >Neither the Soviets nor the US had serious contingency plans in >place in the race to the Moon. Oh? Diverting an Earth-orbital mission (Apollo 8) into a circumlunar flight, because of a rumor that the Soviets were going do it first, sounds like a contingency plan to me. Unless you're rewriting history again. That's not a contingency plan. A contingency plan is "oh shit, the Saturn pogoed and blew, it will take two years to fix, we better switch to the Uranus VI, we just figured the problem with the variable nozzles on those..." Of course there were no Uranii in the real world... | Steinn Sigurdsson |I saw two shooting stars last night | | Lick Observatory |I wished on them but they were only satellites | | steinly@lick.ucsc.edu |Is it wrong to wish on space hardware? | | "standard disclaimer" |I wish, I wish, I wish you'd care - B.B. 1983 | ------------------------------ End of Space Digest Volume 15 : Issue 560 ------------------------------