Subject: Space-tech Digest #58 Contents: Jordin Kare Re: Holographic Lenses S Schaper Re: Holographic Lenses John Stevens-Schlick Robots on the moon and their uses... Philip Fraering Robots on the Moon Don Willits Self Replicating Lunar Factory Philip Fraering Orbital Debris Chris Neufeld Re: Orbital Debris Joe Claffey Off-the-shelf launcher hardware ------------------------------------------------------------ Date: Wed, 28 Mar 90 12:57:42 PST From: Jordan Kare To: UCSBPM@uwplatt.edu, space-tech@CS.CMU.EDU Subject: Re: Holographic lenses > I just came up with an interesting idea (I doubt it's original, > but who knows). > I attended a holography presentation yesterday and the presenter made a > quick comment about a holograph of a lens is a lens. > What I am wondering is is it possible to enlarge a holgram? > Could one make a holgram of a lens, enlarge it, and then have > a huge telescope lens? seems to me the main problem with > big lenses is the thickeness needed. But a hologram could > be put on a mylar sheet. > There's probably a zillion practical reasons why this might not work, > but right now I'm in the "it's neat enough that it doesn't > need to work" stage. > > Brian P. McCarty, N9IWP Holographic lenses are quite common -- many supermarket scanners use holographic lenses and gratings as part of the scanning optics. A hologram of a simple (i.e. spherical) lens is a very simple pattern of concentric rings, very closely related to a ''zone plate'' (a circular diffraction grating with spacing that decreases with increasing radius) Zone plates are commonly used as X-ray lenses, at wavelengths where thick transmitting lenses don't work. The problem with using a hologram as a telescope lens is primarily chromatic aberration -- the focal length varies rapidly (basically inversely) with wavelength. There would also be problems maintaining tolerances -- mylar stretches far too much. A plausible use for a holographic lens is as a narrow-band ``light bucket'' for measuring, e.g., total hydrogen-line emission from a region. Fresnel lenses are another way to make a lightweight lens, but cannot easily be made to high enough quality for astronomy. Overall, big mirrors are much easier and have no chromatic aberration. ------------------------------ Date: Fri, 30 Mar 90 16:34:43 CST From: S Schaper To: space-tech@CS.CMU.EDU Subject: Re: Holographic lenses Yes, I've thought of that tooo. I don't think that you can enlarge the image without a degradation in the resolution, I also don't know about the optical bypass of mylar. How about a reflection hologram. Anyway, it is worth looking into. What if you could do a hologram of an existing large mirror? kept it the same size? And if that isn't good enough for professional use, how about amateur use, say do a hologram of a one meter mirror or else that Yerkes refractor that you were boasting of. Ahh, what a great amateur instrument. You'd only have to get 1/10 wave equivalent optics to be a nice toy. UUCP: {amdahl!bungia, uunet!rosevax, chinet, killer}!orbit!pnet51!schaper ARPA: crash!orbit!pnet51!schaper@nosc.mil INET: schaper@pnet51.cts.com ------------------------------ Date: Mon, 9 Apr 90 10:40 PDT From: Games Wizard Subject: Robots on the moon and their uses... To: space-tech@CS.CMU.EDU I have just joined the space-tech group, so if this is not timely, please forgive me. I am very interested in the concept of robots on the moon doing real work, and I read the excerpted post on sci.space with great interest. I found many of the more technical posts (how to get them to work) were very interesting. However, I thought that the posts about the configuration of a SYSTEM of robots were premature. In order to determine what is needed to solve a problem, you must first better define the problem. I would like to see discussion on the META-topic of what the GOALS for these robots are. Specifically. Once these goals are clearly defined the solution (or set of solutions) to the problem will become more apparrent, and we can with greater force determine whether 4 arms or 1 per vehicle are better suited to the job etc... Let us take the reverse statememt as the definition of the project: You have a fairly small community of robots that you are going to use to solve a problem on the moon. What exactly are the problems that can be solved. What exactly is the highest priority problem to be solved on the moon. Several possibilities come to mind. Excavation of tunnels to be used for later human habitation. Building of structures to be used later for human habitation. Mining and refining of raw materials + construction of (where appropriate) storage facilities. Building a mass driver. Building more robots so that THEY can do some of the other items. Building Solar cells. Needless to say some of these require some of the others if you take the premise that your community is limited in resources, and not constantly getting supplies from earth (a premise which I would encourage as it seems realistic ) Of these, I feel that the first 3 are the best goals, and probably the third is the best short term goal. With mining and refining capability in place, other projects later can use these resources to complete thier missions. So, for me, the question is : Just what exactly is involved in a mining and refining operation, what materials are actually to be processed, should it be two phase with a set of mobile exploration core sampling robots first so that it gets placed in a good area, with the refinery to be constructed later, if any type of volatiles are to be constructed, where are they to be stored? just exactly HOW MUCH stuff do we need to send to get this all started? Sorry, I wish that I could answer all of these questions, but I just don't know enough about the art of materials processing. Can someone point me in the direction of literature on contents of lunar matrerials, and what CAN be done? Ok, Disclaimer time: I apologize if this asks more questions than it answers, but TO ME building a robot is easy, making it do something useful is the hard part. If anybody actually wants someone to write code or help design actual hardware (NUTS-N-BOLTS) instead of just talking about it, count me IN. ------------------------------------------------------------------------------- Trendy footer by: John Stevens-Schlick Internet?: JOHN@tranya.cpac.washington.edu 7720 35'th Ave S.W. Seattle, Wa. 98126 (206) 935 - 4384 ------------------------------------------------------------------------------- My boss dosn't know what I do. ------------------------------ Date: Wed, 25 Apr 90 10:20:35 -0500 From: Fraering Philip To: space-tech@CS.CMU.EDU Subject: Robots on the Moon Yes, I know this is late but: A comment concerning the debate on robots on the moon: I doubt that the robots could be made self-reproducing, but they may still be able to produce the structural components for more robots. For more information on this subject, I believe that the Space Studies Institute was doing some work on this. Philip Fraering dlbres10@pc.usl.edu ------------------------------ Date: Sun, 29 Apr 90 17:18:00 PDT From: willitd@umbra.CS.ORST.EDU To: space-tech@CS.CMU.EDU Subject: Self Replicating Lunar Factory I pulled the article below out of the sci.nanotech newsgroup. It discusses a 1980 NASA study on advanced auotmation, and the author focuses on chapter 5 of the study: a design for a self replicating lunar factory. Chapter 4 of the document (not discussed below) also described a neat orbital Space Manufacturing Facility. I'll dig out the report and summarize shortly. -Don Willits willitd@cs.orst.edu * In 1980 NASA conducted a workshop on "Advanced Automation * for Space Missions." A substantial portion of the resulting * report discussed a self-replicating lunar manufacturing * facility. Chapter 5, "Replicating systems concepts: * self-replicating lunar factory and demonstration" is about * 150 pages long (the entire report is about 400 pages). * The chapter reviews self-replicating systems in general, * Von Neumann's work on self-replicating systems in particular, * discusses various strategies for self-replication, and goes * into considerable detail in the design of a lunar self-replicating * system based on conventional technology. The "seed" system * would be 100 tons -- about 4 Apollo missions to the moon. * In the "Conclusions and Recommendations" they say: * ----------------------------------- * The Replicating Systems Concept Team reached the following * technical conclusions: * o The theoretical concept of machine duplication is * well developed. There are several alternative * strategies by which machine self-replication can be * carried out in a practical engineering setting. * o There is also available a body of theoretical automation * concepts in the realm of machine construction by machine, * in machine inspection of machines, and machine repair * of machines, which can be drawn upon to engineer practical * systems capable of replication. * o An engineering demonstration project can be initiated * immediately, to begin with simple replication of robot * assembler by robot assembler [the macroscopic variety] * from supplied parts, and proceeding in phased steps * to full reproduction of a complete machine processing * or factory system by another machine processing system, * supplied, ultimately, only with raw materials. * ----------------------------------- * Interestingly, almost all of the complexity in the self-replicating * lunar manufacturing system involved making the parts. Assembly * of the parts, once manufactured, was simple by comparison. Of * course, nanotechnology should make the manufacture of parts * relatively easy.... * The report also discusses the implications of self-replicating * systems. One consequence: "From the human standpoint, perhaps * the most exciting consequence of self-replicating systems is that * they provide a means for organizing potentially infinite quantities * of matter. This mass could be so organized as to produce an ever- * widening habitat for man throughout the Solar System. Self-replicating * homes, O'Neill-style space colonies, or great domed cities on * the surfaces of other worlds would allow a niche diversification * of such grand proportions as never before experienced by the * human species." * In the introduction, they say: "The 10-week study was conducted * during the summer of 1980 by 18 educators from universities * throughout the United States who worked with 15 NASA program * engineers." * Copies are available from NTIS. Mail order: * NTIS * U.S. Department of Commerce * National Technical Information Service * Springfield, VA. 22161 * Telephone orders with payment via major credit cards are accepted. * Call: 703-487-4650 and request "N83-15348. Advanced Automation * for Space Missions." (To repeat in case of garbles: 703-487-4650, * NTIS order number: N83-15348). * Cost is about $40.00, various shipping options are available. * You can also get a price quote by telephone. [ WELL WORTH THE COST! -Don ] ------------------------------ Date: Mon, 30 Apr 90 15:52:15 -0500 From: Fraering Philip To: space-tech@CS.CMU.EDU Subject: Orbital Debris Has anyone considered using the fact that a piece of space-grit is moving at high-speed through a magnetic field (the earth's) when it is in orbit? And that the debris is slightly charged due to the UV of sunlight? In short, the force law for this stuff deviates infintesmally from gravity; perhaps a strong magnetic field, of a way of charging the dust to a higher e/m ratio, would improve the force law in our favor. Thank you! Philip Fraering dlbres10@pc.usl.edu Disclaimer: The State board of higher education has determined that USL can't have opinions, and couldn't fund them if they could! So, this must be mine alone... ------------------------------ Date: Wed, 2 May 90 13:42:03 EDT From: Christopher Neufeld To: space-tech@CS.CMU.EDU Subject: Re: Orbital Debris Philip Fraering (dlbres10@pc.usl.edu) writes: > > Has anyone considered using the fact that a piece of space-grit is moving at > high-speed through a magnetic field (the earth's) when it is in orbit? > > And that the debris is slightly charged due to the UV of sunlight? > > In short, the force law for this stuff deviates infintesmally from > gravity; perhaps a strong magnetic field, of a way of charging the dust > to a higher e/m ratio, would improve the force law in our favor. > Well, it wouldn't help to first order, because the Lorenz force always works at right angles to the direction of motion, so for most orbits it would look like stronger or weaker gravity, but no non-radial forces. One thing which would be interesting to explore is the following. A piece of debris in Earth orbit will pick up speed when it's moving away from the Sun, and lose speed when it's heading toward the Sun, purely because of photon pressure. Now, the effect of this is to lower the perigee on successive orbits, and to raise the apogee on succesive orbits. This should make things hit atmosphere eventually. Now, this effect is moderated by the fact that the orbit precesses with respect to the direction to the Sun with a period of one year due to the motion of the Earth around the Sun and to the multipole moments of the Earth's field, with further contributions from the perturbative effects of the Sun and the Moon on the orbit. Question: what is a typical rate of precession for an object in LEO, and how quickly does the orbit precess with respect to the Sun's position? Anyway, this precession means that some time later, that part of the orbit which was being slowed is now being boosted and vice versa. The orbit is therefore stabilized against this decay by the apparent motion of the Sun. Here's the question for the computer modellers out there: what is the maximum surface to mass ratio for which the orbit (say LEO) is stable? If the particle is too light it will decay in much less than a year, so the precession effect won't help. For a particle large enough to survive beyond a certain time, the precession effect will save it from hitting atmosphere. Is anybody ambitious enough to get some feel for the sizes involved? -- Christopher Neufeld....Just a graduate student | "Spock, comment?" neufeld@helios.physics.utoronto.ca | "Very bad poetry cneufeld@pro-generic.cts.com Ad astra! | captain." "Don't edit reality for the sake of simplicity" | ------------------------------ Date: Sun, 6 May 90 16:59 EDT From: CLAFFEY_%CTSTATEU.BITNET@vma.CC.CMU.EDU Subject: Off-the-shelf launcher hardware To: space-tech%cs.cmu.edu@vma.CC.CMU.EDU A similar message to this one was posted to Space Digest (aka sci.space), so you may not want to read it again. To the rest of you: The recent discussion of the RL-10 rocket motor on the net has started me wondering about how much other hardware was availible. In particular: 1) What, if any, rocket-related hardware is availible? 2) Who makes it? I'm interested in seeing if a new launcher can be developed without developing new hardware. Joe Disclaimer: Any opinions expressed above are entirely mine, and anyone else taking credit for them is in big trouble! ------------------------------ End of Space-tech Digest #58 *******************