Subject: Space-tech Digest #71 Contents: Keith Henson Re: Asteroid relocation/mining Nick Szabo Re: Asteroid relocation/mining Keith Henson Re: Asteroid relocation/mining James Smith Re: Asteroid relocation/mining Henry Spencer Re: Asteroid relocation/mining Keith Henson Re: Asteroid relocation/mining Rich Schroeppel Are there stable L5 orbits? Keith Henson Re: Are there stable L5 orbits? Tom Neff Re: Are there stable L5 orbits? Keith Henson Re: Are there stable L5 orbits? Phil Fraering Moving around the solar system [ ideas, references ] George Herbert Re: Moving around the solar system Ted Anderson Re: Moving around the solar system George Herbert Re: Moving around the solar system Paul Dietz Re: Moving around the solar system ------------------------------------------------------------ From: ames!ames!claris!portal!cup.portal.com!hkhenson@uunet.UU.NET To: space-tech%uunet.uu.net@CS.CMU.EDU Subject: Re: Asteroid relocation/mining Date: Wed, 25 Jul 90 23:53:10 PDT X-Possible-Reply-Path: hkhenson@cup.portal.com X-Possible-Reply-Path: sun!portal!cup.portal.com!hkhenson Nick Szabo mentions that nickel/iron alloy "melts too low to cut through rock." Sorry, I don't get it. I have been in a lot of mines, and have yet to see anyone "melting through rock." If you are dealing with more or less silicates, i.e., brittle, you blast, run it through several stages of crushers, and grind it up in a ball mill. I think this would do the trick for anything up to stony types. Now, dealing with big chunks of metal, very hot O2 will cut holes even in stainless steel. Once you have holes, warm CO will disolve the metal. None of these takes particularly high temperatures. Incidentally, a vibratory ball mill, with a gentle stream of gas to move the dust would work just fine in zero g. Roughly shaped lumps of native iron would work ok for balls and liners (metor steel is as good or better than what is used on earth.) One other thing, why bring whole asteroids back to earth? Sort out what you want, or make product. Keith ------------------------------ Date: Thu, 26 Jul 90 11:31:14 -0700 From: "Nicholas J. Szabo" To: uunet!cs.cmu.edu!space-tech@uunet.UU.NET Subject: Re: Asteroid relocation/mining hkhenson@cup.portal.com writes: >Nick Szabo mentions that nickel/iron alloy "melts too low to cut through >rock." Sorry, I don't get it. >[] I am referring to using Ni/Fe as drill bit. Doesn't work. We need special alloys or diamond bits; these will wear out and must be replaced periodically. Blasting must be done deep inside the asteroid to avoid dispersion. (James Smith raises a good concern. Flying rocks will damage power generation, cooling, and communications equipment, among other things). A significant amount of rock-drilling will still be needed to place the charges and cut through the surface to get at the fractured material. We also need machinery to separate, remove, and transport the pieces to our mill. Another possibility is using intense heating/cooling cycles to fracture material; perhaps in combination with blasting. >Now, dealing with big >chunks of metal, very hot O2 will cut holes even in stainless steel [] >None of these takes particularly high temperatures. >[] "very hot" = X < "high"? What temperature of O2 do we need? >Incidentally, a vibratory >ball mill, with a gentle stream of gas to move the dust would work >just fine in zero g. Roughly shaped lumps of native iron would work >ok for balls and liners (metor steel is as good or better than what >is used on earth.) This sounds possible, but the concept needs work. What filter do we use to keep gravel and rocks out of the output, and how often must it be replaced? I assume we are feeding the gas with a pump, since there is no gravity. How do we separate the dust from the gas? How do we manufacture pipes that won't leak the gas? (This requires precise milling and precise fitting of o-rings; or perhaps good powerful welding.) How do we feed rocks into the system without leaking gas? How fast does the Ni/Fe wear vs. the rock? What do we use to enclose the mill (I have an idea from Cole -- melt a small asteroid and inflate it with hot gas inserted via tungsten needle). >One other thing, why bring whole asteroids >back to earth? Sort out what you want, or make product. It would not be wise to bring it too close. However, it will be easier to mine the asteroid at L5 than in solar orbit, because (a) the time cost of money (the mining equipment and products aren't sitting out in Hohmanns for several years), (b) round-trip light time 3 seconds instead of 30 minutes, (c) reduced energy needed to get the mining equipment on site, and (d) we can gather several different types of objects (comets, carbons, metallics) in one industrial park that has all raw materials at hand. Clearly there is no win if we need mining equipment just to move the asteroid. My previous article proposed a method whereby we might be able to move asteroids and comets to L5 without mining equipment, and at current launch costs. Nick Szabo uunet!ibmsupt!szabonj "Faith can move mountains only if it gets a bit of help from engineers." unknown These opinions do not reflect those of any organization I am affiliated with. ------------------------------ From: ames!ames!claris!portal!cup.portal.com!hkhenson@uunet.UU.NET To: space-tech%uunet.uu.net@CS.CMU.EDU Subject: mining asteroids Date: Thu, 26 Jul 90 18:01:08 PDT X-Possible-Reply-Path: hkhenson@cup.portal.com X-Possible-Reply-Path: sun!portal!cup.portal.com!hkhenson Responding to Nick's last one, as I understand it, the carbonicious types have bulk strengths ranging from loose dirt up to about brick. You don't need anything very hard to dig into these. I.e., local metals are good enough. Ball mills I have seen use a very heavy grate on the outflow end. Depending on what you were doing, sorting fines from course would be done in zero g versions of cyclones (same as is used one earth). Rotating locks like a revolving door will get solids into the gas stream, and there are other well known industrial methods. Vapor deposited pipes and simple ebeam welding would make gas tight connections. Far a wear on the pipes, keep the particle velocities below about 10 m/sec and wear goes to near zero. *Lots* is known about these topics, refineries move 50 tons of very expensive sand (artificial zoalites) a minute, and the cat crackers run for several years between rebuilds. O2 cutting of asteroid steel-- might need plasma temp to get it started, but the reaction is exothermic after that. There is another way to break up a metal asteroid, build an open ended induction furnace and pump out the liquid metal. Takes a big power plant, but nothing compared to the solar power satellite proposals. Inflating an melted asteroid I consider to be in the pipe dream catagory, but off hand I can't prove it wouldn't work. Keith Henson ------------------------------ Date: Thu, 26 Jul 90 13:48:53 GMT From: 6079 Smith J To: space-tech@DAISY.LEARNING.CS.CMU.EDU Subject: Re: asteroid reloc/mining Keith made me think of something: Once we've got an asteroid in LEO, we're going to produce a lot of rubble while processing it. One thing we do not want to do is clutter the vicinity of L5 with chunks of rock. Thus if we do processing near Earth, we're going to need some junk-restricting system. If someone knows how to figure out time/cross-section/altitude parametrics for chunks of asteroidal rock or metal to fall out of orbit, which I don't, I'd be curious to know how big a problem this is. I.e., how long do chunks stay up, and how firmly is little stuff held in L5? It would appear that we'd just have to be careful about blasting and digging, keeping a cover over the site. I don't see any good ways to catch the chunks once they fly off. Does anyone else see this as a big problem? You get enough rocks floating around near your processing point, and the orbital transfer vehicles are going to look like Swiss cheese soon.... | James W. Smith, University of Arkansas | jws3@uafhcx.uark.edu | | There's a long, hard road and a full, hard drive | | And a sector there where I feel alive | | Neither NASA nor the U of Ark. is responsible for what I say. Mea culpa. | ------------------------------ From: henry@zoo.toronto.edu Date: Thu, 26 Jul 90 13:59:44 EDT To: space-tech@CS.CMU.EDU Subject: Re: asteroid reloc/mining > If someone knows how to figure out time/cross-section/altitude parametrics > for chunks of asteroidal rock or metal to fall out of orbit, which I don't, > I'd be curious to know how big a problem this is. I.e., how long do chunks > stay up, and how firmly is little stuff held in L5? At L5 altitudes, air drag is zero for all practical purposes. The Moon has been up there for several billion years, after all. There is a shallow gravity well at L5, but I don't have numbers for how shallow offhand. It probably is a good idea to try to keep debris under control, if only (as JWS points out) to avoid polluting your immediate neighborhood badly enough to interfere with transport. I think that is a more serious issue than more "global" pollution. My gut feeling is that an object in a near-but-not-in-L5 orbit won't stay there for very long, given lunar perturbations. Once you get out of a narrow range of orbits, you have to generate an awful lot of debris to compete with the volume of natural junk that wanders around already. The obvious containment technique, if you are using processes that throw out debris (and it is probably simpler to try to avoid such processes if you can), is to just put a Kevlar bag around the whole operation. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ From: portal!cup.portal.com!hkhenson@Sun.COM To: space-tech@CS.CMU.EDU Subject: Re: asteroid reloc/mining/polution/L5 well depth Date: Thu, 26 Jul 90 13:12:08 PDT X-Origin: The Portal System (TM) X-Possible-Reply-Path: hkhenson@cup.portal.com X-Possible-Reply-Path: sun!portal!cup.portal.com!hkhenson Henry was wondering about the velocity to leave the shallow L5 area. It has been many years since I read it, but the number I remember is in the range of 50 m/sec. I tend to agree with Henry, you most likely want to bag any operation in space. It is less trouble than chasing after lost tools, and tool holders :) Keith Henson ------------------------------ Date: Thu, 26 Jul 90 12:45:06 PDT From: Richard Schroeppel To: space-tech@CS.CMU.EDU Subject: Are there stable L5 orbits? Many years ago, I read a tech report describing orbit simulations of objects in the L4 and L5 positions of the Earth-Moon system. The author was unable to find any stable orbits; all his objects either wandered off, crashed into the Moon, or were grossly perturbed (ejected?) after a close Moon encounter. His paper used only the Earth, Moon, and Sun, and treated them as point masses (ignoring lunar mascons, ellipsoidal figure, Earth's bulge, etc.). The wander times were small, less than ten years. The theoretical L5 orbit exists when a secondary orbits a primary in a circle (and the mass ratio is >25). The E/M mass ratio is 80, but the Moon's orbit is significantly elliptical. Solar perturbations are also important, constantly torquing the orbital plane. Has anyone looked at this problem? Will an L5 facility require significant stationkeeping fuel? This is also relevant to the debris question: Perhaps the Moon indirectly collects debris by preventing stable orbits nearby. I've heard that the mascons prevent stable lunar orbits, and that all the various lunar orbiters have decayed, in spite of no atmosphere. Keith? Henry? Rich Schroeppel rcs@la.tis.com There are Lies, Damned Lies, and Unix Documentation. ------------------------------ From: ames!ames!claris!portal!cup.portal.com!hkhenson@uunet.UU.NET MMDF-Warning: Parse error in original version of preceding line at CS.CMU.EDU To: space-tech%uunet.uu.net@CS.CMU.EDU Subject: Re: Are there stable L5 orbits? Date: Thu, 26 Jul 90 18:16:18 PDT X-Origin: The Portal System (TM) X-Possible-Reply-Path: hkhenson@cup.portal.com X-Possible-Reply-Path: sun!portal!cup.portal.com!hkhenson This is only off the top of my head, been a long time since I looked at the papers, and I am not an orbits guru. As I remember it, the presents of the sun makes the L5 point unstable, but there are odd shaped orbits about the point which are either stable or require very small station keeping efforts Now I could care less. Given the unlikelyhood of getting out there in significant numbers before nanotech hits, I no longer am interested in close in space colonies, or even the asteroid belt. Nanotech stuff will make it as easy to go interstellar as to stick around the solar system, and we won't need the support of a government to do it. Keith Henson ------------------------------ From: Tom Neff Date: Fri, 27 Jul 1990 06:22:03 EDT X-Mailer: Mail User's Shell (7.1.1 5/02/90) To: SPACE-TECH Mailing List Subject: Re: Are there stable L5 orbits? On Jul 26, 6:16pm, Keith Henson (Mr. L5!) wrote: > Now I could care less. Given the unlikelyhood of getting out there in > significant numbers before nanotech hits, I no longer am interested in ^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^ > close in space colonies, or even the asteroid belt. Nanotech stuff > will make it as easy to go interstellar as to stick around the solar > system, and we won't need the support of a government to do it. Whew! Well, now we know at least one thing nanotechnology is good for. Space activist removal. ------------------------------ From: portal!cup.portal.com!hkhenson@Sun.COM To: space-tech@CS.CMU.EDU Subject: Re: nanotech/space activist removal Date: Fri, 27 Jul 90 13:39:22 PDT X-Origin: The Portal System (TM) X-Possible-Reply-Path: hkhenson@cup.portal.com X-Possible-Reply-Path: sun!portal!cup.portal.com!hkhenson Tom Neff writes: >Whew! Well, now we know at least one thing nanotechnology is good for. >Space activist removal. Not really. Space colonies at L5 was never what I really wanted, it was just the best I thought I might get in my lifetime. I am now 48. Do you want to tell me that what NASA is doing is going to lead to living at L5 in the remainder of my (unaugmented by nanotech) lifetime? I don't know about *you*, but I find it hard to get fired up about something that only my great grandchildren can take advantage off. I don't think that swaping my goal from space colonies to interstellar exploration should be considered removal from the ranks of the space activist, I just am a little more ambitious than most. Incidentally, in the last few months I thought up using a large aircraft and a long rope to sling payloads into space, and collected enough signature to run for NSS board next year. My relatively low interest in what NASA is doing is mostly due to the rapid progress I see leading to nanotechnology. Keith Henson ------------------------------ Date: Tue, 31 Jul 90 12:55:16 -0500 From: Fraering Philip To: space-tech@CS.CMU.EDU Subject: Moving around the solar system With all of the discussion going around about mining asteroids and comets, and vaporizing comets in order to move an asteroid(!?!?!?!?!), and a discussion going on about whether or not it is more feasible to move the asteroid back to earth orbit or to refine the material on-site, I was reminded of a paper I once read a while back. Since it details another propulsion method, I thought it would be relevant to the discussion. The paper is: _Tethers and Asteroids for Artificial Gravity Assist in the Solar System,_ by P.A. Penzo and H.L. Mayer. It can be found in the Jan.-Feb. 1986 issue of the _Journal of Spacecraft and Rockets_. And no, I don't have the ISBN catalog number handy. I do not believe that it would be legal for me to post the article here. It does detail how a spacecraft with a kevlar tether of the same mass can change its velocity by up to slightly less than 1 km/sec. if it is travelling under that velocity wrt a suitable asteroid. Also of relevance to the discussion is the possible propulsive method of magnetic sailing. Does anyone have any references? Phil Fraering dlbres10@pc.usl.edu ------------------------------ Date: Tue, 31 Jul 90 23:39:03 PDT From: gwh%ocf.Berkeley.EDU@lilac.berkeley.edu To: dlbres10@pc.usl.edu, space-tech@CS.CMU.EDU Subject: Re: Moving around the solar system Cc: gwh%ocf.Berkeley.EDU@lilac.berkeley.edu The references on Magnetic propulsion (magsails using the solar wind) are from Bob Zubren of Martin Marietta Astronautics. He's done two AIAA conference papers and one international conference paper, plus has an article he's winding thru the review process. Basically, you use a superconducting ring to set up a magentic field and push off the solar wind. If you want more detail on the references, I can get it in a couple of days. -george william herbert gwh@ocf.berkeley.edu The OCF Gang: Making Tomorrows mistakes Today! ------------------------------ Date: Wed, 1 Aug 1990 09:15:32 -0400 (EDT) From: Ted_Anderson@transarc.com To: dlbres10@pc.usl.edu, space-tech@CS.CMU.EDU, gwh%ocf.Berkeley.EDU@lilac.berkeley.edu Subject: Re: Moving around the solar system A paper on the magnetic wind sailing also appears in the June issue of the Journal of the British Interplanetary Society, on "Interstellar Studies" I mentioned earlier. I don't have it handy but I believe it was by the same Zubren of Martin Marietta. Ted Anderson ------------------------------ Date: Wed, 1 Aug 90 12:08:38 PDT From: gwh%ocf.Berkeley.EDU@lilac.berkeley.edu To: Ted_Anderson@transarc.com, dlbres10@pc.usl.edu, gwh%ocf.Berkeley.EDU@lilac.berkeley.edu, space-tech@CS.CMU.EDU Subject: Re: Moving around the solar system Quite possible. The preprint I saw for the bigger article he's wrangling through reviewers had a section on using one as a brake for interstellar spacecraft. Aparently, for terminal decelleration, it's the most effecient idea ever proposed. -george william herbert gwh@ocf.berkeley.edu The OCF Gang: Making Tomorrows mistakes Today! ------------------------------ To: gwh%ocf.Berkeley.EDU@lilac.berkeley.edu Cc: Ted_Anderson@transarc.com, dlbres10@pc.usl.edu, space-tech@CS.CMU.EDU, dietz@cs.rochester.edu Subject: Re: Moving around the solar system Date: Wed, 01 Aug 90 17:08:20 -0400 From: dietz@cs.rochester.edu Freeman Dyson also discussed braking by plasma drag in his article in the collection "Extraterrestrials: Where Are They?" (Hart and Zuckerman, ed., Pergamon Press, 1982). Dyson suggested that astronomers interested in finding ETs should look for long, linear radio features -- the "skid marks" of plasma brakes. Since that article was published, remarkable linear threads of radio emission have been detected near the galactic center; however, these appear to be natural, although I don't know if they've settled on a theory yet. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ End of Space-tech Digest #71 *******************