Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from hogtown.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 ; Thu, 6 Jun 91 01:28:39 -0400 (EDT) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Thu, 6 Jun 91 01:28:28 -0400 (EDT) Subject: SPACE Digest V13 #603 SPACE Digest Volume 13 : Issue 603 Today's Topics: Re: SPACE Digest V13 #565 Re: SPACE STATION FREEDOM WOUNDED Re: SPACE STATION FREEDOM WOUNDED Re: Fred vs. Exploration: head-to-head competition Re: Should Galileo be rerouted? Re: Gravity! What Gravity!?! Try This! Re: Laser launchers Re: 14 Astronauts have died for space exploration? Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription requests, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: 19 May 91 18:31:11 GMT From: swrinde!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!emory!wa4mei!ke4zv!gary@ucsd.edu (Gary Coffman) Subject: Re: SPACE Digest V13 #565 In article <9105171915.AA02292@ucbvax.Berkeley.EDU> space+%ANDREW.CMU.EDU@msu.edu writes: > >>Mining the asteroids for materials to_be_used_in_space makes sense over >>the long term. There is no hurry in the next twenty to fifty years, >>however. Meanwhile we need to keep our pet scientists happy with >>pretty pictures from the big gravity sinks. > >I think your 'ten-to-twenty years' comment shows that you grew up in an >age when space was not that important because it was a place for >scientific experiments and national prestige stunts, both of which cost >losts of money. Actually the time frame stated was "twenty to fifty" years, and I think that is highly optimistic. I grew up in a time when only Jules Verne thought travel to outer space was even possible. Nevertheless, with Congress swinging the meataxe at space related items and pouring the money into their S&L buddies' pockets through HUD, the prospect of space industries, and their need for cheap materials, seems to be receding rather than getting closer. I predict that space related spending will continue to decline as a percentage of Federal revenues until America wakes up *again* as it did in 1957, and by then it may well be too late to catch up. >Thoses time-scales will change when it appears that money can be made. >Drastically. I'm betting my life on it. If it DOESN"T happen in my >lifetime, my carrer will suck, and my wife will hate me, and I'll be a >miserable fucker and die bitter and angry at the whole world. :-) >(I'm joking, but it's proabably true) I don't see anyone doing the development needed who isn't counting on the government to pay the bill in one way or another. Private investors putting hundreds of billions of their own money at risk for a highly speculative payoff twenty to fifty years down the road just doesn't seem in the cards. Once the government spends that money, and the infrastructure is in place, and the speculation turns to relative certainty, then private industry will be willing to risk it's own capital in a big way. >The resources I'm thinking of may be salable (even at VERY low prices) in the >very short-term. I.E. before real operations get started. >Take nickel. It's current price is around $1/lb. With a typical Nickel >Asteroid, you could sell it for $.05/lb, and still make a klilling. (Do you >know how much nickel would be in an asteroid 1km wide?). Could any mining >company compete? More importantly, could we get them to invest? More importantly, what does it cost to get that asteroid into LEO so that mining and return missions could be done? What does it cost to do the mining and return missions? Now what does the nickel cost per pound? Something the size of our little Jupiter probe isn't going to go fetch that monster chunk of nickel. We don't have an HLV to launch anything bigger. We have just lost funding for a possible in space assembly point. We don't have anything to fetch the asteroid with, nor is there public or private funding to develop such a thing. Even if we were fortunate enough to discover an Earth orbit crossing pure nickel asteroid that only required 1000 m/s delta vee tommorrow, it would be five to ten years before we could even build up a probe to go take a look at it. With our lack of heavy lift, even a simple probe would probably take a roundabout trajectory that would take years to achieve rendezvous. Then the huge recovery mechanism must be put in place. Even 1000 m/s isn't easy to achieve with a mass of 4*10^12 pounds. The time cost of money would make such an investment prohibitive for the private sector. Let's look at some numbers: Annual worldwide consumption of nickel: 475,000 tons (950,000,000 pounds) Total global expenditure for nickel at $1 per pound: $950 million/year Total global expenditure for nickel at $.05 per pound: $47.5 million/year Total mass of 1 km nickel asteroid: 4*10^12 pounds Years at current global consumption rates to deplete asteroid: 4210 years Now a venture capitalist is going to want to see better than a 10% annual return on his money for a risky startup venture. With a total *gross* revenue of $47.5 million per year from the asteroid, the venture capitalist is going to be willing to put up less than $470 million dollars. A lot less considering that payback doesn't start the first year. I'm not a good enough wiz with a financial calculator to give a precise answer, maybe someone else is. Anyway, considering that there will be substantial operating costs to mine the asteroid as well as horrendous initial costs to move it to LEO, can you do it all for $470 million? If not, your project won't find private funds. If you *do* manage to recover one asteroid though, you won't have to go get another for over 4,000 years. So after you prove the concept by returning *one*, getting investors for the second should be easy in 4000 years when you need a second one. >It's interesting to note that the most abundant source >of nickel in the world has been determined to be the site of an ancient >meteor impact (See Doomsday_Has_Been_Canceled for more of these neat things). >Think of the savings if we caught the next on BEFORE it fell. Think of the savings of simply using the one we got delivered for free. Diverting an asteroid to LEO will cause one positive effect, the Christic Institute will go into orbit. :-) With all the publicity received by the Dinosaur Killer, advocating deliberately moving an asteroid near Earth will generate mass protests that will make the anti-nukes look positively pro-technology. Gary ------------------------------ Date: 20 May 91 19:26:26 GMT From: agate!tornado.Berkeley.EDU!gwh@ucbvax.Berkeley.EDU (George William Herbert) Subject: Re: SPACE STATION FREEDOM WOUNDED In article <2852@ke4zv.UUCP> gary@ke4zv.UUCP (Gary Coffman) writes: >[...] >ESA and NASDA sign long term agreements with a reliable partner, the >Soviet Union, and proceed to develop space, garnering all the benefits >while the US continues to slide into third world status. Did I just hear the Soviet Union described as a 'reliable partner' ??? Are these the same Soviets whose next station was cancelled for _total_ lack of budget, not relative priority disagreements? The ones whose Mars '94 probe is now lacking 80% of its funding, and who are starting to come to ESA and the French with hat in hand so it will fly at all? The ones who built an honest-to-god HLV and may have the program zeroed because a large percentage of their population wants to eat instead??? Talk to a space scientist who knows someone in the Soviet union in a similar job. They're not happy right now. [flames to me, not the newsgroup... i think i'm far enough off topic as is] -george . ------------------------------ Date: 20 May 91 22:48:07 GMT From: agate!spool.mu.edu!mips!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!jpl-devvax!ddc@ucbvax.Berkeley.EDU (Douglas Creel) Subject: Re: SPACE STATION FREEDOM WOUNDED >The something wrong is people who devote their attention to shallow >heroes instead of the real heroes of space like James Van Allen, >Ed Danielson, Eleanor Helin, Steve Ostro, and the many others who Please clear something up for me Mr. Szabo. Just who exactly is it that you consider "shallow" heroes. Is it perhaps the three astronauts who died on the pad during the Apollo program, or is it the seven men and women who died on board Challenger? I'd really like to know how you can compare the likes of James Van Allen to these people who made the ultimate sacrifice in the service of their country. I'm waiting to hear what you have to say. Douglas D. Creel Navigation Systems Section (Mars Observer Project) Jet Propulsion Laboratory ------------------------------ Date: 21 May 91 00:14:28 GMT From: swrinde!elroy.jpl.nasa.gov!jarthur!nntp-server.caltech.edu!juliet.caltech.edu!irwin@ucsd.edu (Horowitz, Irwin Kenneth) Subject: Re: Fred vs. Exploration: head-to-head competition In article <1991May20.224010.4410@jpl-devvax.jpl.nasa.gov>, ddc@jpl-devvax.jpl.nasa.gov (Douglas Creel) writes... >I find it humorous how people cite the "wisdom" of Congres when it suits their >own personal beliefs, and then attack Congress when its decisions don't support >their views. How someone can trust the judgement of a Congressional >subcommittee, which is nothing but a bunch of lawyers whose knowledge of science >and engineering is woefully pitiful, over that of NASAs' leadership is beyond >my comprehension. And by the way, NASA's leadership is compromised of more >than just astronauts. I don't recall William Lenoir ever riding on a shuttle, >and last time I checked he was in favor of the station. > Just want to point out a correction here...Bill Lenoir did ride on the shuttle in its early days (STS-5 or STS-6 I believe). ------------------------------------------------------------------------------- Irwin Horowitz |"Suppose they went nowhere?"-McCoy Astronomy Department |"Then this will be your big chance California Institute of Technology | to get away from it all!"-Kirk irwin@romeo.caltech.edu | from STII:TWOK ih@deimos.caltech.edu | ------------------------------------------------------------------------------- ------------------------------ Date: 18 May 91 08:58:36 GMT From: ogicse!sequent!muncher.sequent.com!szabo@decwrl.dec.com Subject: Re: Should Galileo be rerouted? In article <29302@hydra.gatech.EDU> ccoprmd@prism.gatech.EDU (Matthew DeLuca) writes: >>>If the first two are useless rocks, what makes you think >>>the next dozen are going to be any better? > >I think of it in this manner: say rock #1 is a dud, and rock #2 is a >dud. Knowing that these are two samples of the asteroids out there, >do you (a) go on to rock #3, hoping that rocks #1 and #2 were flukes, >or (b) go on to where you *know* you will learn something? If this were >a game show, it would definitely be option (b) for me. These arguments suffer from their abstractness. There are a wide variety of asteroids and comets, and things classed as asteroids that are probably dead comets, and things living in the outer asteroid belt that are classified as asteroids but are chemically closer to comets that have never been active. There are metallic asteroids which are core fragments of a once larger condensed object. There are asteroids made primarily of basalt, asteroids made primarily of olivine, asteroids with carbon and clay, asteroids that have undergone substantial collision and asteroids that have not, and a large number of asteroids that are mixtures of these types. There are old comets with mostly water and dust and new comets with large amounts of CO2 and CH4. There are comet fragments ranging in from dust to Tungaska-sized (100,000 tons) to the comets themselves, and it is unknown how many intermediate sized fragments exist or how much water they contain. And that is the tip of the iceberg of the detail we know, and know we don't know, from the feeble studies done to date. With a reasonably funded, greatly expanded program, the amount of detail and variety will be even more substantial. So we won't be saying "rocks #1, #2, ..., #n were dull, therefore all rocks are dull." We will be saying things like "this kind of rock is more promising than that kind", and "feature A1 and B2 are more important than features A2 and B1, and rocks 9, 13, and 41 are most likely to exhibit these features, so let's go take a look at those with these particular kinds of instruments." -- Nick Szabo szabo@sequent.com "If you understand something the first time you see it, you probably knew it already. The more bewildered you are, the more successful the mission was." -- Ed Stone, Voyager space explorer ------------------------------ Date: 18 May 91 20:35:05 GMT From: vax5.cit.cornell.edu!usf@cu-arpa.cs.cornell.edu Subject: Re: Gravity! What Gravity!?! Try This! THIS POSTING WAS A TEST TO SEE WHAT RESPONCE WOULD BE LIKE! ALTHOUGH IT WAS BASED ON AN IDEA I ONCE HAD IN THIS REGARDS. THANKS FOR THE RESPONCES! THESE COMMENTS ARE MY OWN RICK ------------------------------ Date: 18 May 91 23:18:51 GMT From: valid!caber!lou@uunet.uu.net (Louis K. Scheffer) Subject: Re: Laser launchers gary@ke4zv.UUCP (Gary Coffman) writes: [.......] >We know several things about the beam power levels. >1. The power level will have to be at least as high as the power level > produced by a chemical rocket lifting the same mass. Gigawatts. Let's make a rough guess. We can afford to orbit smaller payloads with a laser launcher. We stick with known technology, and assume a metal nozzle, and water working fluid. We can heat the water to 4000 degrees C before we melt the nozzle. This gives an exhaust velocity of 4 Km/sec. To reach the 7 Km/sec vehicle velocity to orbit, we need a mass ratio at least e^(7/4) or about 7. Let's assume 10 (what current single stage rockets have). We then have a 10,000 Kg launch mass. If we start at 2.5 gees, when we have used half the fluid we are at 5 gees acceleration. Our speed at that point is about 2 Km/sec. Thus the power required is: 2000 m/sec * 50 M/sec^2 * 5000 kg = 500 Mw. If the back end of the rocket has area 10 m^2, this is a power density of 50 Mw/m^2. (The Saturn 5 delivered 35 Gw through an diameter of about 10 m, or about 350 Mw/m^2, for comparison.) >2. The power level must be high enough to turn enough ice to explosive > plasma to give the same thrust level as a chemical rocket. Gigawatts. No, you just need to heat it up to about 4000 degrees. Plasma is not a requirement. >3. A beam power level high enough to turn ice to plasma will also be > high enough to turn air to plasma. This seems wrong on several counts. First, you do not need to turn the ice to plasma. Second, surely you pick a wavelength that water absorbs better than nitrogen and oxygen. You still get absorption by the water waper in the air, but water vapor is only a small percentage of air. If you use visible light, for example, only a tiny percentage is absorbed by the air at these levels, but we can arrange the nozzle to absorb close to 100%. >4. For a highly dispersed beam source (multiple lasers in a widely > spaced ground array) the geometry of the situation shows that > somewhere below the apex of the converging beams the power density > reaches the plasma point of air. This also seems unduly pessimistic. First, we don't have plasma. Second, the power density is only high right behind the nozzle. At this point we can afford a fair amount of spread since the nozzle represents a target with a large subtended angle. Third, since the rocket is moving at a good clip, we only need the air behind the nozzle to maintain good conditions for a few milliseconds at most. Each of these arguments alone imply that is is possible to deposit almost all the energy in the nozzle. >5. As air pressure decreases, the power needed to ionize what air remains > decreases. True, but once again, we are not ionizing anything. We also can use less thrust once we are above most of the atmosphere. > [...] During the early phases of launch, the beams will >be converging at nearly right angles to the vehicle. This seems to preclude >precise steering of your ice vehicles. This is not at all clear. Assume the vehicle has a 1 second time constant for off center thrust producing pitching moment. We can change the aim of lasers with about 1 KHz bandwidth. Thus we should be able to maintain control of the vehicle until the geometry becomes unfavorable by about a factor of 1000. This happens at 89.6 degrees to the line of flight. [...] >Ok, I concede this one. I hadn't considered a tapered cable. Still, growing >a single crystaline strand, WITH A TAPER, that would reach to geosync, sounds >rather unlikely for the simple reason that crystals like to determine their >own shape. I still think this is a fundamental rather than developmental >problem. Note that we are talking about beanstalks here and not dynamic >tethers. They have another set of practical problems as launcher replacements. This is clearly not a fundamental problem. Conceptually, just grow a big enough crystal, of whatever shape it wants, then machine the tapered strand out of it. The more practical approach is to get it to grow in that shape in the first place. -Lou Scheffer ------------------------------ Date: 17 May 91 13:43:28 GMT From: dev8b.mdcbbs.com!rivero@uunet.uu.net Subject: Re: 14 Astronauts have died for space exploration? In article , A20RFR1@MVS.CSO.NIU.EDU (Bob Rehak Ext. 3-9437, AIS Central Services - Swen Parson 146) writes: > > 14 astronauts? Last time I counted there were only 10. > > Apollo I: Grissom, White, and Chaffee. > STS-61L Challenger: Scobee, Smith, Resnik, Onizuka, McNair, > Jarvis, and McAuliffe. > > A couple have died flight testing aircraft that was not related to > space exploration and a couple have did in car accidents...I think. If Grissom, White, and Chaffee (who died on the ground) are considered as "Lost in the line of duty", the same should apply to the astronauts who died in training flights. Just because they didn't make the evening news doesn't mean that their contributions or sacrifices should go unheeded. ========================================================================== \\\\ Michael Rivero | "I drank WHAT!" | "THIS PORTION OF SIG | \ (. rivero@dev8a.mdcbbs | Socrates ------------------- UNDER | )> DISCLAIMER::: |-----------| | CONSTRUCTION | == "Hey man, I wasn't | | | (pardon our | ---/ even here then!" | | | white-out) | ++++++++++++++++++++++++++++++++++++++++-------------------+++++++++++++++ ------------------------------ End of SPACE Digest V13 #603 *******************