Subject: Space-tech Digest #105 Contents: NASA press kits (1 msg) OMV update (1 msg) International Space University (1 msg) SSME reliability (3 msgs) Ground assist to SSTO? (4 msgs) Misc. SSTO (3 msgs) ------------------------------------------------------------ Date: Mon, 16 Mar 92 09:54:42 CST From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: NASA press kits If you'd like a press kit for the upcomming shuttle mission (STS-45?), call (713) 483-0123, and ask for public affairs. Once you get connected (after a nice "music on hold" interlude), ask for a press kit for the upcomming mission. Better yet, ask for a "personal package" (although I don't know if they'll give you one), which includes the official crew portrait, a ground track map, and the press kit. The press kit itself contains a diagram of the payload bay configuration, description of all of the major and most of the minor mission objectives, and bios on the primary crew. Mission objective descriptions include descriptions of the hardware used, the sponsoring agency, and the names and addresses of the principal investigator(s). The package also contains a description of the mission patch, which can be a pretty interesting snapshot of the flight crew's thinking. All of this for my favorite price -- FREE. You don't have to be a member of the press to get one of these - NASA is all too happy to send them out to individuals, since this is about the most the public affairs office is allowed by law in the area of active PR. Those of you living outside the US might get a different response, though, since NASA doesn't pay for domestic postage, and besides, you don't vote. (Sorry Henry). As a personal favor, I'd appreciate it if everyone who does this also tells a local science teacher about it. It'd also be nice if you could share your press kit with a youngster. Lou Adornato | Support for space exploration is a mile wide Supercomputer Systems, Inc | and a micron deep Eau Claire, WI | The secretary (and the rest of the company) uunet!ssi!lfa or lfa@ssi.com | have disavowed any knowledge of my actions. ------------------------------ Date: Mon, 16 Mar 92 10:08 PST From: trost@reed.edu (Bill Trost) To: space-tech@cs.cmu.edu Subject: OMV I believe I asked a question about the OMV in this mailing list some time back. Well, I finally found the answer on WAIS's wall-street-journal-sample source. An excerpt of the article, dated 8 June 1990, follows: Last fall, the space agency tried to save the project by cutting back the tug's capabilities. By choosing cheaper rockets and less sophisticated navigation, the agency reduced the tug's ability to maneuver in space and to boost satellites. It also gave up the ability to base the tug at the space station -- which had fallen well behind schedule too -- or have it orbit independently. But the reprogramming left the tug with too little to do, and NASA decided it was better off spending its money elsewhere. William Lenoir, NASA's associate administrator for space flight, said he figures the space agency will eventually need a tug-like capability but that NASA has at least two or three years to decide exactly what kind of craft will be necessary. ------------------------------ Date: Tue, 17 Mar 92 12:19:07 PST From: gwh@lurnix.lurnix.com (George W Herbert) To: tcsi!cs.cmu.edu!space-tech@uunet.UU.NET Subject: International Space University Pardon me for something not totally technical in nature, but I just got a letter of acceptance for the International Space University program in Japan this summer, in the Space Engineering department, and am somewhat excited 8-) Now all I need to do is learn Japanese in two months... -george william herbert gwh@lurnix.com gwh@ocf.berkeley.edu ------------------------------ Date: Mon, 16 Mar 92 12:17:57 PST From: gwh@lurnix.COM (George W Herbert) To: space-tech@cs.cmu.edu Subject: Re: Project ClusterShuttle Cc: gwh@lurnix.COM Thanks to Henry for clearing up other's confusion about the RL-10 8-) I didn't think I'd need to explain more. However, I take offense at this line: >(If you want to improve the shuttle, leave the SSMEs alone and build a >set of liquid-fuel boosters to replace the SRBs.) After what the various safety reports and panels have concluded about them, I think that _both_ the SSME's and SRB's need to be replaced. Only NASA would theoretically plan 99.99% reliability and then put 1% failure rate items in with special exceptions... neither the SSME nor the SRB pass real safety criteria. Remember that most of the engineers on the ground, on seeing the explosion of Challenger, were initially afraid that it was a SSME letting go. -george william herbert gwh@lurnix.com gwh@ocf.berkeley.edu ------------------------------ Date: Mon, 16 Mar 1992 20:39 EST From: "GORDON D. PUSCH" Subject: SSMEs, Reliability, and Vehicle Optimization To: space-tech@cs.cmu.edu Regarding the reliability of SSMEs: I remember reading a conference paper in (I think) _Acta Astronautica_ regarding "whole-system vehicle optimization." The thrust of it was that the "edge of the envelope" character of the SSMEs was an *endemic* problem in launch vehicles *because of how they are designed*: to wit, by optimizing *sub*-systems until one or more material/safety limits are hit, then "freezing" the design parameters of that subsystem in the successive subsystem optimizations. The result is an overall vehicle design with multiple subsystems on the hairy edge of some design-limit or other, greatly increasing the probability that the whole vehicle will suffer a single-point failure. I.e., you get the Shuttle ... The (misleading!) logic behind this is that all the subsystems of an optimal system must be (locally!) optimal. The *actual* motivation was that in the "old days" the computer simulation and optimization methods couldn't handle whole-vehicle problems (even now, it's pretty tough --- too many variables). The flaw in this logic is that there is NO reason the *local* minimum thus obtained should be near the *global* minimum of the *overall system* ... The authors pointed out that we now know that many whole-system problems can get "hung up" in local minima if optimized on a subsystem-basis --- the "cost-" or "fitness-landscape" is very "rough." They found that by optimizing the "whole-vehicle," instead of subsystems of it, they didn't wind up with multiple subsystems up against their "hard limits," therefore obtaining a much larger *overall* safety margin for the launch vehicle. Speculation: mayhap the SSTO problem gets easier from a "whole system" viewpoint? Also, I remember that Max Hunter's SSX paper argues that most SSTO studies minimize the *WRONG FIGURE OF MERIT*: the "launch-to-payload" mass-ratio, rather than the "empty-to-payload" mass-ratio. He argues that the latter, not the former, is a better measure of operating cost. Roughly speaking, the vehicle's *energy density* should be maximized, rather than its *exhaust velocity*; a useful first-cut is to compare "propellent_density * Isp^2," rather than Isp. (An interesting sidebar is that LOX/Methane and LOX/Propane have 1.56 and 1.71 times the energy- density of LOX/LH2, respectively; Hunter claims that from a NASA-Langley study, LH2 has a *negligable* advantage over hydrocarbons vis-a-vis payload-to-empty ratio *IF* one can achieve a "20--40% weight reduction" [sic] over Shuttle technology (I'm not sure what he means by this) ... ) Any comments? Gordon Pusch ------------------------------ Date: Wed, 18 Mar 92 09:19:40 CST From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: Re: Project ClusterShuttle > However, I take offense at this line: > >(If you want to improve the shuttle, leave the SSMEs alone and build a > >set of liquid-fuel boosters to replace the SRBs.) > > After what the various safety reports and panels have > concluded about them, I think that _both_ the SSME's > and SRB's need to be replaced. Just replacing the SRB's with something that could be shut down would increase the odds on surviving a return to launch site (RTLS) abort by quite a bit. This is a maneuver that's so risky NASA's never even tested it outside the simulators. The first time it's performed in real life will be in a crippled vehicle by a crew in trouble. The cost of such a replacement would be limited to development, testing, and retraining. On the other hand, the cost of retrofitting a replacement SSME will easily exceed the original production cost of the Orbiter, unless your replacement engine is plug and mouning compatable with the existing one, has nearly the same weight, and produces similar thrust at similar flow rates. It's simply too late to do that kind of screwing around with the orbiter itself. It's a vehicle that _should_ be nearing the end of it's operational life, although there seem to be too many careers attached to it to let it die gracefully. > Only NASA (Apparently you've never heard of an outfit called the U.S. Navy...) > would theoretically plan 99.99% reliability > and then put 1% failure rate items in with special > exceptions... neither the SSME nor the SRB pass > real safety criteria. You'll _never_ ride in a vehicle that has a 99.99% reliability. I'd be willing to bet that the chair you're sitting in has a lower reliability than that. I've never heard anyone claim that the Shuttle (or any orbital launch system) has or ever will have that kind of reliability. What was promised to Congress was a 98% operational reliability, and even that level is strangling the program. Not all reliabilities are created equal. If a failure effects analysis uncovers a failure mechanism that results in the loss of crew or vehicle, proper failure management may include instrumentation, controls, and ground or flight crew procedures that interrupt the failure mechanism _without_ changing the root failure. You therefore have an operational reliability that exceeds the theoretical system reliability. Example: That one case of premature engine shutdown that I mentioned resulted in an abort to orbit. It was accompanied by sensor drift in another engine, which, according to the limits built into the software, would have forced the second engine to shut down. An alert flight controller spotted this and called to take the engine limits to manual, which saved the mission from having to perform a TAL or AOA abort. The root failure here was the instrumentation drift, and, depending on the operating environment at the time of the failure, could have resulted in an RTLS (which has a questionable probability of survival), or a contingency abort (which is guaranteed to splash the orbiter, and has a questionable probability of crew survival). However, the flight rules that the controller (wish I could remember her name) was operating under provided a means of interrupting the failure mechanism. The reliability of the hardware remains unchanged, but the operational effects of the failure are negligable. > Remember that most of the > engineers on the ground, on seeing the explosion > of Challenger, were initially afraid that it was > a SSME letting go. > I've seen this before, and my response is SO WHAT? Initial fears/suspicions/beleifs minus data plus one quarter is worth one cup of coffee. That's why you do a failure analysis. The main engines would have been the prime suspect in any case - when your choice is between a device that converts a highly explosive gas mixture from cryogenic to plasma forms, versus an Estes rocket with a thyroid condition, which way would _you_ guess? Lou Adornato | The secretary (and the rest of the company) Supercomputer Systems, Inc | have disavowed any knowledge of my actions. Eau Claire, WI | "Sure, the cow may have jumped over the moon, uunet!ssi!lfa/lfa@ssi.com | but I bet she burned up on reentry." ------------------------------ Date: Mon, 16 Mar 92 15:23:12 CST From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) To: uunet!bach.convex.com!ewright@uunet.UU.NET Subject: Ground launch systems (was Re: SDIO's SSTO (eieio) and NASP) Cc: uunet!cs.cmu.edu!space-tech@uunet.UU.NET > >1) A continuous injection launch tube would be a lot more effective. > > Probably more expensive as well. > Remember my assumptions. I was talking about an interim system > that might be built if the first Delta Clippers off the assembly > line were a bit too heavy to make it into orbit on their own. > If the rocket-sled-up-the-side-of-a-mountain isn't going to be > needed later on, when the weight-reduction program has produced > results, you're not going to want to sink any more money into it > than absolutely necessary. If you're going to sink _any_ money into it you might as well build a system that you can continue to use - even if your weight scrub produces the desired results (not a given), you'll still want to have a launch site that can toss heavier payloads into orbit. I won't delve too much into the politics involved, (this _is_ the tech list), except to say that gov't funding for a permanent, useable installation will be a lot less painful than for a "temporary" one. A reasonable compromise might be a distributed injection catapult, like the steam powered ones on carriers. > > >2) There's _no_ worthwhile mountain anyplace useful for launching in > >the U.S. At least not for an equatorial launch from the contiguous 48. > > You get directly into an equatorial orbit from anywhere unless your > launch site is on the equator. A dog-leg manuever is always necessary. > An out of plane maneuver is incredibly wasteful of fuel. In addition, low inclination launch sites give the best mission flexibility - you can always launch to an orbit with a higher inclination than the launch site, but to get to a lower inclination than launch site you need to do an out of plane burn once you've acheived orbit. The real issue is that the farther south you go, the better your throw weight for the same fuel mass. On the other hand, I'm not all that certain that a few thousand feet at the terminal end makes all that much difference - the drop in air density isn't all that big, (at least not as far your terminal velocity is concerned), and you're talking about a pretty small percentage of the total altitude - launching from Denver as opposed to the Cape would get you about 1/150th closer to your target altitude, a gain that would be more than offset by the loss in launch site velocity at the higher inclination. I guess the big question is whether the vehicle is designed for a vertical or horizontal liftoff - a vertical liftoff means you build your launcher up the side of a mountain, while a horizontal one means you have a launch rail sticking out of the side of the VAB. Either way, you're still going to be traveling pretty fast in pretty dense air when you leave the launcher. > The debris footprint to any commercial jet would cover significant > population centers. So what? In order for Delta Clipper to be > successful, each vehicle has to fly the same number of missions > as a commercial jet, which means it can't afford to crash any > more often. Nor is there any reason why it should. Your prejudices > are based on the converted artillery rockets we've been flying for > 30+ years, not functional spaceships like Delta Clipper. (The planned > launch site for Delta Clipper is Edwards AFB.) > You may be right, although I'd be willing to bet that there's a range safety officer who would explode if he/she heard that. You're talking about the first few flights of an experimental system, and therefore you won't have any operational data to backup your reliability estimates. Keep in mind that a lot of the operational claims of the Delta Clipper are identical to those of the Shuttle as late as 1981 (which is not to malign either program). Again, there would be political considerations, especially in a nation full of mathematical illiterates who want a completely safe world (I remember people *driving* from the deep south to Canada to escape the ground track of Skylab), but that's for another forum. Lou ------------------------------ From: "Allen W. Sherzer" Subject: Re: SDIO's SSTO (eieio) and NASP To: space-tech@cs.cmu.edu Date: Mon, 16 Mar 92 17:24:40 EST > (The planned launch site for Delta Clipper is Edwards AFB.) DC-X will be going up at White Sands. Allen + They're just jealous because they don't have three + | wise men and a virgin in the whole organization | | --Vincent Cianci on the ACLU suit to remove a nativity scene | +----------------------419 DAYS TO FIRST FLIGHT OF DCX----------------------+ ------------------------------ Date: Mon, 16 Mar 92 16:17:40 -0600 From: ewright@bach.convex.com (Edward V. Wright) To: ssi!lfa@uunet.uu.net, bach.convex.com!ewright@uunet.uu.net Subject: Re: Ground launch systems (was Re: SDIO's SSTO (eieio) and NASP) Cc: cs.cmu.edu!space-tech@uunet.uu.net >I won't delve too much into the politics >involved, (this _is_ the tech list), except to say that gov't funding for >a permanent, useable installation will be a lot less painful than for a >"temporary" one. I didn't mean that the installation wouldn't be useful. Simply that it would be phased out after a few years when better vehicles were available. Also, I'm not necessarily thinking that this would be a government project. One possible scenario: the DC-Y (Delta Clipper prototype) can't quite make it into orbit. Congress kills this "boondoggle," but McDonnell Douglas still gets plenty of orders from Northwest Airlines and Federal Express, who are really more interested in suborbital markets anyway. Then Space Transport, Inc. comes along with a plan to build a railroad up the side of Pike's Peak... Steam catapults might work, but I know very little about them. Can they launch a vehicle the size of the Delta Clipper vertically instead of horizontally? Can you keep the acceleration low enough that a noncombat aircraft and noncombat air crew can tolerate it? >The real issue is that the farther south you go, the better your throw weight >for the same fuel mass. True. If this is significant enough, we can consider launching the prototype from American Samoa or from an aircraft carrier near the equator. But for operational vehicles, the advantages of basing within the continental US are probably overwhelming. >On the other hand, I'm not all that certain that a few thousand feet at the >terminal end makes all that much difference - the drop in air density >isn't all that big The delta-v is probably more significant than the delta-h. The rocket sled would carry the propellent for the SSTO engines during the climb up the mountain, so you're getting a headstart of one mile plus 500 mph. >I guess the big question is whether the vehicle is designed for a >vertical or horizontal liftoff - a vertical liftoff means you build >your launcher up the side of a mountain, while a horizontal one means >you have a launch rail sticking out of the side of the VAB. Either way, >you're still going to be traveling pretty fast in pretty dense air when >you leave the launcher. Not all that fast -- you want to keep the seperation subsonic. And the SSTO/sled combination would probably pull the same number of gees the SSTO would on a free flight, so unless you have a long horizontal runup, the SSTO at separation would be travelling no faster than it normally would at that altitude anyway. >You may be right, although I'd be willing to bet that there's a range safety >officer who would explode if he/she heard that. SSTO/sled combination would probably pull the same number of gees the SSTO would on a free flight, so unless you have a long horizontal runup, the SSTO at separation would be travelling no faster than it normally would at that altitude anyway. >You may be right, although I'd be willing to bet that there's a range safety >officer who would explode if he/she heard that. "Range safety": You're still thinking missiles. McDonnell Douglas is talking about certifying the Delta Clipper as an aircraft. Aircraft don't have range-safety officers; they have air-traffic control. We need to change our thinking about launch vehicles, as G. Harry Stine (a former range-safety officer) keeps pointing out. ------------------------------ Date: Mon, 16 Mar 92 20:50:05 -0600 From: pgf@nasa11.usl.edu (Phil G. Fraering) To: ewright@bach.convex.com, space-tech@cs.cmu.edu Subject: Ground launch systems (was Re: SDIO's SSTO (eieio) and NASP) Again, there would be political considerations, especially in a nation full of mathematical illiterates who want a completely safe world (I remember people *driving* from the deep south to Canada to escape the ground track of Skylab), but that's for another forum. I'm still living in the deep south, just as when Skylab fell down; I remember no widespread panic or anything like that, although I do remember some funny jokes about it in _Travels with Farley_. ------------------------------ From: henry@zoo.toronto.edu Date: Tue, 17 Mar 92 14:26:47 EST To: space-tech@cs.cmu.edu Subject: Re: SDIO's SSTO (eieio) and NASP >> ... DC-Y will >> be a roaring success if it gets into orbit with a payload of one kilogram, >> and a dreadful disaster if it can't. > >If you have something that's _real close_ to SSTO, you just strap on some >small expendable boosters... 90% of SSTO is actually worth a lot. Agreed in general, although I might have said 95%. My original comment was motivated by political aspects: if DC-Y gets funded, it's going to be quite a lump of money, and if it can't reach orbit *somehow* -- adding strap-ons not excluded -- the political fallout may be bad. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Wed, 18 Mar 92 08:50:48 CST From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: Re: Delta Clipper performance claims > Lou comments that: > >You may be right, although I'd be willing to bet that there's a range safety > >officer who would explode if he/she heard that. You're talking about the > >first few flights of an experimental system, and therefore you won't have > >any operational data to backup your reliability estimates. Keep in mind > >that a lot of the operational claims of the Delta Clipper are identical to > >those of the Shuttle as late as 1981 (which is not to malign either program). > > Think airplanes. The MD-11 didn't > carry destruct charges on it's > maiden flight... it's a change > of paradigm, both in system performance > and in reliability. > The MD-11 didn't overfly population centers until it had a lot of hours on both the airframe and the control system. If there'd been a possibility of a loss of control putting a city at risk, you can bet your tail that it would have carried a destruct package. You're talking about a launch system to give extra boost capability to a prototype vehicle; that's an awful lot of unknowns. My original objection stands. The first few hundred flights should have _no_ capability of fragging civilians. Lou Adornato | "When in trouble/ When in doubt Supercomputer Systems, Inc | Run in circles/ Scream and shout" Eau Claire, WI | The secretary (and the rest of the company) uunet!ssi!lfa or lfa@ssi.com | have disavowed any knowledge of my actions. ------------------------------ Date: Wed, 18 Mar 1992 10:23:09 EST From: KEVIN@A.CFR.CMU.EDU Subject: Destruct charges To: space-tech@cs.cmu.edu X-Vmsmail-To: IPROUTE"space-tech@cs.cmu.edu" Thought I should interject this: destruct charges on rockets are intended for thrust termination, so that the rocket doesn't leave it's planned trajectory. They are not designed to blow the thing to tinfoil so that none of the itsy-bitsy pieces are big enough to harm what they land on. That is taken care of by making the flight path such that it doesn't overfly anything important. The risk is if the craft lands in Tampa rather than in the ocean, not whether or not it lands. In fact, putting enough explosives into a craft to ensure complete fragmentation would probably eliminate your payload. The DC-X (unmanned) and any unmanned production variants should have some kind of thrust termination so they don't leave the flight path. I am not so certain on manned ships - I would think the flight crew or passengers would appreciate some chance to land the thing safely... What you will not see is a "Mr. Nuke" on each ship designed to turn an errant craft into harmless vapor. kwr Internet: kr0u+@andrew.cmu.edu or kryan@oroboros.biods.com ------------------------------ From: henry@zoo.toronto.edu Date: Wed, 18 Mar 92 11:27:10 EST To: space-tech@cs.cmu.edu Subject: Re: Delta Clipper performance claims >...that's an awful lot of unknowns. My original >objection stands. The first few hundred flights should have _no_ >capability of fragging civilians. Certainly, but what has this to do with operational use? If DC is to be certified to airliner standards, it will probably stack up that many flights during development, testing, and certification. Only in the missile business is something "fully operational" after four flights. Note, by the way, that all test flights of expendable launchers from the Cape have *some* "capability of fragging civilians". The destruct systems (which, as others have noted, don't shred the vehicle into confetti) are useful only in the early phase of flight, when the debris footprint is in the Atlantic. Later on it crosses populated areas in Europe or Africa. The shuttle mission that lost an SSME midway up almost had to drop its ET on southeast Europe. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ End of Space-tech Digest #105 *******************