Subject: Space-tech Digest #109 Contents: Delta Clipper onorbit power (9 msgs) STS-43 missed ascent targets (3 msgs) space-tech intro (1 msg) solar sailing (1 msg) Mir orbital elements needed (2 msgs) ------------------------------------------------------------ Date: Thu, 26 Mar 92 08:08:59 CST From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: Delta Clipper onorbit power Anyone know how the DC-Y's going to get electrical power while on orbit? The "classical" approach has been to use hydrogen/oxygen fuel cells. I beleive the oxygen is usually in liquid form, but I don't know if the hydrogen is carried as liquid or just high pressure gas. The fuel cells generate potable water as a byproduct; more water than the crew can consume, so they need to periodically dump waste water from the holding tanks. The cells themselves also need to be periodically purged of excess water. Back in the days when this had to be done by hand, it was a major pain. These days the sequence is controlled by the flight computers, and it's still a pain (one mission last year nearly got cut short because of an ice plug in a dump line). I've been wondering if MacDac's going to try to find a different approach. Lou Adornato uunet!ssi!lfa | The secretary (and the rest of the company) Supercomputer Systems, Inc | have disavowed any knowledge of my actions. Eau Claire, WI | ** Space IS our future! ** ------------------------------ From: henry@zoo.toronto.edu Date: Thu, 26 Mar 92 10:50:45 EST To: space-tech@cs.cmu.edu Subject: Re: Delta Clipper onorbit power >Anyone know how the DC-Y's going to get electrical power... The obvious source would be fuel cells, since they already have LOX and LH2 aboard. (Even on orbit; the attitude-control system uses them, and of course DC-Y needs main-engine fuel for landing.) >don't know if the hydrogen is carried as liquid or just high pressure gas. Liquid. High-pressure gas containers are very heavy for their capacity. >I've been wondering if MacDac's going to try to find a different approach. It's hard. (Bear in mind, too, that the DC program is trying to avoid unnecessary innovation.) There are only so many ways energy can be stored, and they all have annoying problems. Chemical energy -- batteries or fuel cells, the only difference being that a battery's fuel is all stored in the battery itself -- is still the best of a bad lot. I'd be tempted to just design for minimal on-orbit power use and rely on lithium batteries, at least for the DC-Y prototype. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Thu, 26 Mar 92 11:36:39 -0600 From: ewright@bach.convex.com (Edward V. Wright) To: henry@zoo.toronto.edu, space-tech@cs.cmu.edu Subject: Re: Delta Clipper onorbit power >I'd be tempted to just design for minimal on-orbit power use and rely on >lithium batteries, at least for the DC-Y prototype. Of course, power requirements are reduced if you don't have to design the vehicle for a baseline mission of 7+ days like the Space Shuttle. I would expect the DC-Y's standard endurance to be faily short compared to the Shuttle. (Has anybody heard about this?) ------------------------------ Date: Thu, 26 Mar 92 13:21:48 -0500 From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Re: Delta Clipper on orbit power I would be surprised if they used anything other than fuel cells. After all, the hydrogen is going to be constantly boiling off anyway, so *why not* use it for power at the same time? BTW: how fast does the hydrogen boil off? I suspect this would limit the utility of a DC-? for interplanetary use, if not for going to the moon. As for DC not being baselined for 7 day missions: couldn't one just reduce the payload and carry a bit more fuel into space, to run the fuel cells for a longer time? Paul ------------------------------ Date: Thu, 26 Mar 92 13:55:38 -0600 From: ewright@bach.convex.com (Edward V. Wright) To: dietz@cs.rochester.edu, space-tech@cs.cmu.edu Subject: Re: Delta Clipper on orbit power >BTW: how fast does the hydrogen boil off? I suspect this >would limit the utility of a DC-? for interplanetary use, >if not for going to the moon. Yes, you would have to use an external fuel pod with much better insulation. Storing liquid hydrogen for months or years is a problem that requires additional R&D. >As for DC not being baselined for 7 day missions: couldn't >one just reduce the payload and carry a bit more fuel into >space, to run the fuel cells for a longer time? Yes, that's what baselined means: to get additional time on orbit, you'd have to trade off some of the design payload. That said, I'm still not sure what the baseline endurance of Delta Clipper is expected to be. (I'd expect at least 24 hours to allow for rendezvous and landing opportunities.) ------------------------------ From: henry@zoo.toronto.edu Date: Thu, 26 Mar 92 15:03:59 EST To: space-tech@cs.cmu.edu Subject: Re: Delta Clipper on orbit power >BTW: how fast does the hydrogen boil off? I suspect this >would limit the utility of a DC-? for interplanetary use, >if not for going to the moon. Shouldn't be prohibitive for lunar work. The 30-day extended-duration orbiter uses fuel cells plus a LOX/LH2 pallet, and of course the Apollo CM did too (the LM used batteries). For interplanetary work, you would probably want to use a solar array. >As for DC not being baselined for 7 day missions: couldn't >one just reduce the payload and carry a bit more fuel into >space, to run the fuel cells for a longer time? Should be feasible, if common tankage is being used. (I'm not sure about that.) Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Thu, 26 Mar 92 16:32:16 CST From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: Re: Delta Clipper onorbit power > From uunet!zoo.toronto.edu!henry Thu Mar 26 15:19:01 1992 > >Also, I thought they where planning on using JP for propellant, not LH2? > > They seem to be gung-ho on hydrogen, at least for DC-X and probably for > DC-Y as well. An optimized production version might use hydrocarbons, > perhaps propane rather than JP. > But it'll still need to retain LH2 tanks for power generation. On the other hand, I beleive JP is hypergolic with pure oxygen (I read somewhere that you can't use petroleum products as lubricants in a pure oxygen environment because they spontaneously combust). That would mean that you'd still have an interconnected main/rcs fuel tree. > They've got four maneuvering flaps that swing outward from the aft > portion of the body, like airbrakes in a fighter only they're controlled > individually. I don't know how they plan to drive them. The reentry > itself isn't powered; they start engines for landing only at the last > minute. Not sure whether deorbit is done with RCS or main engines. I'd suspect that they'd need the mains, as it sounds like they're planning on a fairly high initial entry angle (to place the majority of the aerobraking at high altitude), and that translates to a pretty lage kick. The Shuttle uses the OMS engines for the reentry burn, even though it has a relatively shallow initial entry, but that may just be to save wear and tear on the RCS thrusters. > I don't know what response rate they need from the flaps. If it's not > high, they may just plan on electrical actuators. > That's a lot of electical power for any kind of control authority at high speeds. The high response rate the Shuttle needs is because of reentry - the only aerosurface movements during ascent are to reduce structural loading. Of course, it's probably dangerous to make comparisons, since it sounds like a completely different reentry profile. > Agreed that a hydrazine APU seems like a mistake in this context. Especially when you include the storage and handling problems, and the weight and complexity of cooling systems (the water spray boilers ice up on a regular basis). Not to mention the fact that APU exhaust is corrosive and highly toxic. Considering the fact that they only put out something like 35 horses each, it might be better to take the weight penalty and use a propane burning internal combustion engine (like something out of a forklift), with it's own oxygen line and the cooling system connected to the thermal protection system (after handling a reentry, what's a few hundred more BTU's?). They won't even need an inverted oil system, since they'll already be decellerating by the time they need to fire up the hydraulics. Next question: Onorbit heat rejection - is the DC going to unfurl a radiator once it hits vacuum (like Skylab, the Apollo CSM, and the Shuttle), or is it going to have a radiator embedded in the outer skin (like the LM). I'd guess the former, since the LM was low powered and strictly exoatmospheric. Lou Adornato uunet!ssi!lfa | The secretary (and the rest of the company) Supercomputer Systems, Inc | have disavowed any knowledge of my actions. Eau Claire, WI | ** Space IS our future! ** ------------------------------ Date: Fri, 27 Mar 92 00:24:27 EST From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. To: space-tech@cs.cmu.edu Subject: Re: Delta Clipper onorbit power >I'd be tempted to just design for minimal on-orbit power use and rely on >lithium batteries, at least for the DC-Y prototype. > Henry Spencer at U of Toronto Zoology Didn't Buran use lithium batteries instead of fuel cells? Of course, for a fully operational system, they probably planned to switch over to fuel cells. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ From: henry@zoo.toronto.edu Date: Fri, 27 Mar 92 11:40:39 EST To: space-tech@cs.cmu.edu Subject: Re: Delta Clipper onorbit power >... I beleive JP is hypergolic with pure oxygen (I read somewhere >that you can't use petroleum products as lubricants in a pure oxygen >environment because they spontaneously combust)... Unfortunately, not so. It would be convenient, but in fact JP/LOX rockets need ignition systems. Petroleum lubricants are indeed taboo in oxygen systems, not because they ignite but because they can explode. It isn't reliable enough to have any practical use, however. >... The Shuttle uses the OMS engines for the reentry burn, even >though it has a relatively shallow initial entry, but that may just be >to save wear and tear on the RCS thrusters. I believe they can do a de-orbit with the RCS thrusters, as a backup for a major OMS failure. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Thu, 26 Mar 92 07:44:01 CST From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: STS-43 missed ascent targets My wife heard something on the news regarding the current shuttle mission; I'm getting this through an imperfect filter from a source with questionable resolution (the same people who don't know the difference between an APU and a fuel cell), but apparently the ascent targets where missed and an OMS-1 burn was needed. Anyone have better information on this? Any idea how this will impact the mission objectives? How close are they to the planned orbital elements? We don't have a newsfeed for sci.space, so I don't know if it was in the NASA headline news. Lou Adornato | The secretary (and the rest of the company) Supercomputer Systems, Inc | have disavowed any knowledge of my actions. Eau Claire, WI | "In God we trust - everyone else, show your data" uunet!ssi!lfa/lfa@ssi.com | - Mission Evaluation Room, JSC, Houston, TX ------------------------------ From: henry@zoo.toronto.edu Date: Thu, 26 Mar 92 10:44:09 EST To: space-tech@cs.cmu.edu Subject: Re: STS-43 missed ascent targets >... apparently the ascent >targets where missed and an OMS-1 burn was needed. Anyone have better >information on this? Any idea how this will impact the mission >objectives? How close are they to the planned orbital elements? They were short 13 ft/s, apparently due to slightly substandard SSME performance and possibly some disturbance from the residual-propellant dump. They did a small burn at about T+3hr to fix it. I would expect no mission impact. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Thu, 26 Mar 92 11:57:39 -0500 From: dietz@cs.rochester.edu To: henry@zoo.toronto.edu, space-tech@cs.cmu.edu Subject: Re: STS-43 missed ascent targets I heard 6 fps, but that may have been garbled. Paul ------------------------------ Date: Thu, 26 Mar 1992 17:22-EST From: Marc.Ringuette@DAISY.LEARNING.CS.CMU.EDU To: space-tech@cs.cmu.edu Subject: space-tech intro Here's a rehash of the space-tech intro, in case some of you have forgotten the details on how to subscribe, unsubscribe, or retrieve something from the archive. --M. ===== This is a "hello" message to test your mail address and let you know what's up. The list has about 150 participants. Traffic on a busy month averages a message per day, but in some recent months there has been almost no traffic. I send out a digest every 10-15 messages. Unless you asked to be on the digest, I've added you to the raw list. If you would prefer the digest format, send mail and I'll switch you. We're pretty relaxed, but we hope that you'll put a bit of extra effort into posts to space-tech: look up a reference or two, do a few calculations, and try to think things out a bit. Feel free to bring up your favorite topics, though...that's the whole point! Addresses ========= To send mail to everybody on the list, use space-tech@cs.cmu.edu To send mail to the maintainer, use space-tech-request@cs.cmu.edu Old Stuff ========= I have edited together the messages I found most interesting into "space-tech excerpts" which I've posted more broadly: EM Launchers Tether Propulsion CMU Mars Rover High Velocity Guns Mars Mission Ship Design Orbital Debris Launch Loops Robots on the moon If you'd like these, let me know. I think they're the most worthwhile of the space-tech discussions so far (about 150k bytes). However, I have archived all the old material, if you'd rather see the original messages (1.3 meg and growing). You can send me mail asking for any of the excerpts or old digests; but if you'd rather talk to a machine, the archives are available for anonymous FTP from daisy.learning.cs.cmu.edu (128.2.218.26) in directory /usr/anon/public. Enjoy. ---------------- | Marc Ringuette |------------------------ | mnr@cs.cmu.edu | Cucumber Science Dept. |---------------------------------- | 412-268-3728 | Cranberry Melon Univ. | 'Tis not her coldness, father, | ----------------| Pittsburgh, PA, 15213 | That chills my labouring breast: | ------------------------| It's that confounded cucumber | | I've ate and can't digest. | ---------------------------------- ------------------------------ Date: Fri, 27 Mar 92 15:04 PST From: trost@reed.edu (Bill Trost) To: "GORDON D. PUSCH" Subject: Re: solar sailing cc: space-tech@cs.cmu.edu [Old mail; pardon the leap of context] In message <01GG62W6Z5QS9PM3FO@crl.aecl.ca>, "GORDON D. PUSCH" writes: note that this assumes a *flat* sail; while this is a reasonable first approx., in general there will be some tendency toward "parachuting" or "coning" of the sail, depending on how it is supported. I vaguely recall that the maximum "coning" angle in one heliogyro-type sail I saw discussed was several degrees ... Woah, time out! Doesn't this imply that a helogyro will naturally try to move itself so that its sail is parallel to the incoming sunlight? Consider: sunlight | | \ / \/ / / / / _\| wimpy (and poorly drawn) ---------- O force here || \/ lotsa force here Since the leeward sail is getting more of the light, it'll be pushed harder, and will start to turn around the center of the gyro more than the windward sail will. Of course, the whole structure is rotating, which adds an entirely new twist ( :-) ) to the issue...could someone who understands rotational dynamics go over how this works? ------------------------------ Date: Tue, 31 Mar 92 08:20:25 CST From: ssi!lfa@uunet.UU.NET (Louis F. Adornato) To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: Mir orbital elements needed Anyone happen to have the orbital elements of the Mir space station? Also, has anyone heard anything about a proposal to use Energias to boost space station components? Would that be from Kazahkstan, Cape Hope, or KSC? Has NASA formally responded yet? Lou ------------------------------ Date: Tue, 31 Mar 92 09:59:51 -0600 From: ewright@bach.convex.com (Edward V. Wright) To: ssi!lfa@uunet.uu.net, cs.cmu.edu!space-tech@uunet.uu.net Subject: Re: Mir orbital elements needed >Also, has anyone heard anything about a proposal to use Energias to >boost space station components? Would that be from Kazahkstan, Cape >Hope, or KSC? Has NASA formally responded yet? Probably academic. The Russians have announced the shutdown of the Energia and Buryn programs. ------------------------------ End of Space-tech Digest #109 *******************