Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Mon, 12 Mar 90 01:42:05 -0500 (EST) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Mon, 12 Mar 90 01:41:37 -0500 (EST) Subject: SPACE Digest V11 #139 SPACE Digest Volume 11 : Issue 139 Today's Topics: space news from Feb 5 AW&ST Re: Artificial Gravity rephrased Solar System Questions from a Novice Re: Artificial Gravity Re: Spacecraft drives and fuel efficiency Saturn's Rings Keplarian Elements Wanted ! ---------------------------------------------------------------------- Date: 12 Mar 90 05:11:02 GMT From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu (Henry Spencer) Subject: space news from Feb 5 AW&ST Arianespace starts testing on an "external inflatable mattress" to shield the base of Ariane 4's payload fairing against engine noise somewhat. Substantial Moon/Mars funding request in NASA's new budget request may help Congress take the project seriously; the lack of any funding for it to date has not helped its credibility. FY91 budget request from NASA is $15.1G, a 23% increase. First major funding in 25 years for an unmanned lunar mission, to wit the Lunar Observer remote-sensing orbiter. Predictable big lumps of money to get space station hardware started, various Mission-To-Earth projects underway, and Moon/Mars technology work rolling. Long-lead funding for an unmanned life-sciences series of Earth-orbit missions, carrying animals etc. for studies into effects of free fall. [This may be partly in response to unhappiness over the decision that there will be no animal facilities on the space station.] Major expansion for commercial-space-related work. $229M for buying commercial launch services. Funding for long-duration- orbiter hardware. And $119M for NASP. New shuttle manifest, the result of the Hubble launch delay and the need to protect the launch window for Ulysses this fall. Gamma-Ray Observatory slips from June to November. Infrared Backscatter Signature Survey (USAF and SDI) slips from November this year to Jan 1992. The Astro-1 mission (UV telescope package attached to the shuttle) remains set for May, but the Astro-2 and Astro-3 missions in 1992 and 1993 have been shelved. NASA offers to move ESA and JSA modules up in the station assembly schedule, although available power will be very limited early on. ESA is cautiously in favor; US users will see their hardware delayed and are expected to be opposed. This offer came a few days before representatives of ESA, JSA, and ESA's major national agencies testified before a House committee. It seems to have mollified them only slightly; they were openly pissed off about not being consulted over last fall's schedule and design revisions. "Partners do not make decisions unilaterally that will damage the investment of the other partners... Neither do they simply shift their own difficulties onto their partners' shoulders..." "ESA still does not know the full extent of NASA's new proposals." "...could raise great difficulties in continuing to secure political and financial support." Canada was not represented at the hearings because Canadian law bans government officials from activities that might be construed as lobbying foreign legislators. Picture of LDEF in Columbia's cargo bay after arrival at KSC. General Samuel C. Phillips, head of Project Apollo from 1964 through Apollo 11, dies Jan 31. Short slip in Atlantis's secret launch as suspect fuel pump is replaced. First images from Spot 2; it seems to be working. Arianespace sets commercial prices for use of the ASAP auxiliary-payload platform on Ariane. (ASAP carried the amateur-radio satellites on the Spot 2 launch.) $600k for the whole thing, which can carry up to six small satellites. Launch opportunities will be relatively few, since ASAP will not fit in a two-primary-payload configuration, and most Ariane launches carry two comsats. Arianespace is also looking into heavier secondary payloads. -- MSDOS, abbrev: Maybe SomeDay | Henry Spencer at U of Toronto Zoology an Operating System. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 12 Mar 90 04:30:02 GMT From: cs.utexas.edu!jarvis.csri.toronto.edu!helios.physics.utoronto.ca!physics.utoronto.ca!neufeld@tut.cis.ohio-state.edu (Christopher Neufeld) Subject: Re: Artificial Gravity rephrased In article <90070.191112MXP122@psuvm.psu.edu> MXP122@psuvm.psu.edu (Zaphod Beeblebrox) writes: >Before I get majorly flamed here I would like to rephrase my question >about artificial gravity on a ship. . .sure a spinning 'donut' at part >of the ship and the astronauts can jog around or whateven on the inside >circumference experiencing a normal force from the floor. . . and a person >who falls out of an airplane feels 'weightless' (no air resistance) because >there is no normal force exerted on him by the floor, the earth, etc. >but concerning circular motion to induce artificial gravity. . is this same >exact effect as gravity? > Almost exactly the same. There are two important differences. - Tidal effects are different in the two systems. The centrifugal "force" goes linearly with distance from the centre of the cylinder, while the gravitational force goes as the inverse square of the distance from the centre of mass, assuming higher order multipole effects to be unimportant. Your head would weigh less than your feet in a cylinder with a small radius. You'd probably get very, very sick if your head projected into or beyond the axis of rotation. - The coriolis "force" is inextricably linked to the rotating cylinder, while it can be completely absent on a planetary body. The coriolis pseudo-force results in apparent deflections in the paths of bodies falling through the field. The first effect would be noticeable to human senses for cylinders of radius less than about ten metres. The second effect may or may not annoy your balance centres (anybody know of any studies done into this?). >Sure the floor is pushing the guy up and he >feels 'heavy' but there is no force say on his arm pulling it down. . .??? >Sure his arm is attached to his body and his feet are being pushed 'up' and his >arm comes along for the ride but is this the same exact effect as gravity >pulling equally over his whole mass?? > Yes it is. The arm has to turn in a circle as well, so if it weren't attached to the body it would fall toward the floor of the cylinder. It would actually fall in a spiral, hitting the ground to anti-spinward of where you expect it to hit. Ugh, enough of these falling body parts analogies. >. . .maybe a better question is what scale would this >have to be attempted say on a trip to Mars. . and how much energy would be >needed to make up for friction on the bearings etc. > As much energy would be needed as is dissipated in the bearings. What this is obviously depends on many things, such as the composition of the bearings, the size of the carousel, the angular velocity of the carousel, the uniformity of the mass distribution around the carousel, and the rate at which masses (such as people) shift around the carousel. >and would the angular >momentum of such a spinning section make turning the ship more difficult >during the flight etc.. . .hey I only saw the movie. . > Well, this isn't Star Wars. The ship would know weeks ahead of time when it had to turn, and because the ship would probably spend the time before then in free-flight, you have weeks to turn the ship around. If you are planning several course changes in quick succession at the rendezvous point you'd almost certainly spin down the carousel. Quick turnings with the carousel rotating would place torque stresses on the bearings and would require heavier construction of the ship than would be required by the other mission criteria. Turning the ship is anything but intuitive. If the ship has the carousel spinning counter-clockwise around its long axis, and you want to turn the long axis to the right in some set of coordinates, you have to fire the thrusters which push down on the ship from above. In other words, the thrusters which point your ship down when the carousel is stationary point your ship to the right when the carousel is spinning. >Mark. . MXP122 at psuvm.psu.edu -- Christopher Neufeld....Just a graduate student | "I always think there's neufeld@helios.physics.utoronto.ca | a band." cneufeld@pro-generic.cts.com Ad astra! | Prof. Harold Hill "Don't edit reality for the sake of simplicity" | (The Music Man) ------------------------------ Date: 9 Mar 90 23:28:07 GMT From: ladcgw!hacgate!lori@uunet.uu.net (Lori + 8/9) Subject: Solar System Questions from a Novice Forgive the novice questions....I've never posted to sci.space before, so I'm not sure if they will be inappropriate or not. I just bought an old poster of our solar system from a swap meet last weekend, and some of the facts on it are really intriguing. Can someone answer a few questions about Mercury? Its temperature is hundreds of degrees F on the sunny side, and (fewer) hundreds of degrees F below zero on the dark side. The poster also says that it 88 days to rotate. What would Mercury's climate be like if it rotated as fast as the earth? How fast would it have to rotate to produce a moderate or life-supporting climate, at least at certain latitudes (longitudes?)? Also, the earth's atmosphere is very different from all the other planets. (In fact, they all seem unique.) Could someone explain why? Are there dual-sun solar systems? This poster didn't seem to think so (but hey, it's pretty old). If there are, how do the suns revolve around each other? Would the bigger sun tend to draw the smaller one toward it? Here's a pretty dum question, I'm sure....Does our sun rotate? Which way? Does the whole solar system rotate with it? ...lori ------------------------------ Date: 12 Mar 90 03:40:23 GMT From: cs.utexas.edu!jarvis.csri.toronto.edu!qucdn!gilla@tut.cis.ohio-state.edu (Arnold G. Gill) Subject: Re: Artificial Gravity In article <90070.152634MXP122@psuvm.psu.edu>, MXP122@psuvm.psu.edu (Zaphod Beeblebrox) says: > >How realistic is the idea that if a spaceship had a section revolving that >the astronauts could just hang around in there and experience 'gravity' >i.e. like in the movie 2001. . .wouldn't the spinning section have to keep >accelerating to have the this effect??? It does keep on accelerating, but that is actually not the important facet of this question. I beleive you are asking whether the spinning section must have a motor attached to keep it spinning. In general, the answer is yes, but only enough to overcome the friction of the bearings and supports that hold it in place. Think of the rotating cylinder in terms of energy rather than forces. A spinning cylinder can only lose energy through some type of frictional forces, whether they be direct contact (like ball bearings) or at a distant (like magnetic braking, etc). If the cylinder cannot lose energy, it will not slow down! ------- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- | Arnold Gill | | | Queen's University at Kingston | If I hadn't wanted it heard, | | BITNET : gilla@qucdn | I wouldn't have said it. | | X-400 : Arnold.Gill@QueensU.CA | | | INTERNET : gilla@qucdn.queensu.ca | | -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- ------------------------------ Date: 11 Mar 90 16:39:05 GMT From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!watserv1!watdragon!watyew!jdnicoll@tut.cis.ohio-state.edu (Brian or James) Subject: Re: Spacecraft drives and fuel efficiency I think perhaps Mr. Ryan is incorrect in his statements about energy contents of high exhaust velocity boosters. It's true that mass ratios go down as Ve increases, but the energy tied up in getting the reaction mass to Ve goes up exponentially (E~V*e2). A pure 'photon-drive' style booster would be one hell of good light show before your eyes ran down your face, and would be a good way to drive a mohole at the same time (My texts are inaccessable right now. Could someone post the power output of a hundred ton launch vehicle boosting at 4ish gs propelled by a pure annihilation booster?). Not that anyone advocatedusing these extreme approach, of course. Whem I said that the detonation of an annhilation energised booster would be survivable at short ranges, I meant on the order of 1000 meters or so, and I assumed a launch mass of only a few hundred tonnes using a couple of mg of antimatter. Mr. Maroney advocates only producing this stuff in space (Lunar Farside, anyone?). The problem with that is the current lack of well developed power generating systems in space (OK, there's one *big* fusion generator, but it's currently hard to get a direct feed cheaply). If you put the am source on Earth, you can use the powergeneration systems in place now. If prudence dictates a remote location like Farside, then I suspect that antimatter is unlikely to contribute anything useful for a long time. JDN ------------------------------ Date: 11 Mar 90 15:52:15 GMT From: eru!luth!sunic!mcsun!ukc!harrier.ukc.ac.uk!spt1@bloom-beacon.mit.edu (Stephen Thomas) Subject: Saturn's Rings Hello. I have a couple of queries about Saturn's ring system that I hope some of the readers out there will be able to assist me with. I apologise if they are questions that have been asked before - I have not been reading this group for very long. The first query is this: What is the composition of the rings? I have read that they are composed of ice and rock, but I would like to know a little more about the makeup of the rings. The second query: Last I heard, the ring system was maintained by a shepherd (sp?) moons arrangement. How delicate is this system? In other words, if some of the moons were removed (somehow), what would happen to the rings? Would it settle into a new ring system, or would it tend to disintegrate? If it did disintegrate, how long would this process take? I realise that the answers to these questions depend on how many and which moons were removed, but I would be interested in knowing what others might think. I ask out of curiosity, one of those thoughts which strike you when you are trying to think about something else, and then won't let go. :-) Stephen -- Never give | Stephen Thomas fate an | JANET: spt1@ukc.ac.uk even chance | Telephone: +44 (0)227 764000 ext 3824 | Snail: Computing Lab, University of Kent at Canterbury, UK. ------------------------------ Date: 12 Mar 90 06:09:32 GMT From: milton!swanie@beaver.cs.washington.edu (Eric Swansen) Subject: Keplarian Elements Wanted ! Is there anyone (or anyplace) that can provide we with recent Keplarian Elements for satellites ? I've recently found this neat program that tracks satellites, but I need to add in the data for the "birds" that I'd like to monitor... In particular Salyut 7, MIR, Space Shuttle (updated 2x daily+/-) and perhaps other birds more visible from Earth.... Ideally I'd like to TELNET or FTP to a site, but that is probably asking too much...... Any Suggestions ? ------------------------- Eric C. Swansen University of Washington DC-13 Seattle swanie@milton.acs.washington.edu ------ ------------------------------ End of SPACE Digest V11 #139 *******************