Date: Mon, 6 Feb 1989 18:41-EST From: space-tech-request@CS.CMU.EDU To: "~/st/lists/stdigest" Subject: Space-tech Digest #25 Contents: Paul Dietz Asteroid searching Steve Abrams Magnetic Induction Propulsion? Marc Ringuette Re: Magnetic Induction Propulsion? Steve Abrams Re: Magnetic Induction Propulsion? Paul Dietz Re: Magnetic Induction Propulsion? Larry Klaes Articles from CANOPUS which may interest/help us ------------------------------------------------------------ Date: Tue, 31 Jan 89 15:19:05 EST From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: asteroid searching I quoted the following figures from a paper about Tom Gehrel's Spacewatch telescope project: >Scope: f/5 91 cm newtonian scope, modified to f/3.85 by a relay lens >CCD: 512x320 pixel RCA SID 53612 (30 micron pixels), cooled > to -60 C in a vacuum housing > pixel size: 1.73 arcsec > readout noise +-200 electron/hole pairs (rms, I think) > dark current 50 ehp/pixel/s > Exposure time: 60 sec. Now, I don't know if they've gone to a better chip, but more modern CCDs have much better performance. I called Astro Link, a company that advertises in Sky & Telescope, and got the specs on their camera, the HAL 21-PC65 Cost: $12,800 (including power supply and PC interface card) CCD: 572x485 pixels. Distributor is Sanyo (manufacturer is secret) Temperature: -75 to -80 C (thermoelectric cooler) Dark current: .01 ehp/pixel/s Readout noise: 20 ehp/pixel Quantum efficiency: 90% in red, about half that in blue. Compared to the original chip (from RCA) this new chip would have internal noise over 12 times lower for a sixty second exposure, which means one could use a smaller scope with the smaller chip (so as to have the same field of view) and still get an adequate SNR. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Sun, 29 Jan 89 23:14:24 CST From: sedspace@doc.cc.utexas.edu (405986289 abrams) Posted-Date: Sun, 29 Jan 89 23:14:24 CST To: space-tech@cs.cmu.edu Subject: Magnetic Induction Propulsion? Last semester, when I found out about the Lunar Polar Probe conference (to be held in Houston in April), I began trying to develop a simulation model for a solar sail to deliver the probe to lunar polar orbit using thermoreflection modulation as a "switching" scheme to perturb the orbit in a controlled and desirable manner. This involved creating an aluminum film on a nitinol (55-NiTi since I have more hard physical data on it) frame. By running a current through the NiTi, the film would be heated and the reflectance would change by a few percent. Judicious selection of reflectance would result in a net energy gain during each orbit. This was all based on several papers published in the 60s and 70s. Then I realized that I had a large current loop (giving a dipole magnetic moment mu) in a non-uniform magnetic field (B). I tried to consider the effects of both solar radiation pressure *and* magnetic induction to affect the probe's orbit. However, (and I never thought I'd hear myself say this) the danged sail films kept getting in the way...so, I trashed them. I realized that the current loop could be expanded into several, solenoidal loops oriented along the orbit's radius vector, parallel to the orbit's angular momentum vector, and along the cross product of the two - in the direction of the probe's velocity vector - to yield a net magnetic moment in any desired direction. By running currents through the various solenoids, the craft would be torqued into various attitudes for, say, Earth observation, and the solenoids would be resistively-heated (resistivity of 55-NiTi is around 80 micro-ohms/cm) into maintaining their shape (since they wouldn't be cycling between deformed and non-deformed states, the fatigue problems that plague other shape- memory-alloy products are minimized). Even so, the magnitude would remain constant and, effectively, aligned with the Earth's magnetic field whatever the orientation of the probe. I was hoping to use this magnetic interaction to alter the orbital parameters. I looked up what NASA info I could (STAR reference N69-40269, NASA-SP-8017: NASA Space Vehicle Design Criteria-Environment. Magnetic Fields: Earth and Terrestrial, M. Harris, et al. Mar 1969) -- that only gave criteria for minimizing magnetic torques on spacecraft. I couldn't believe that no one had ever suggested this (using controlled magnetic torques) as a feasible, low-thrust option for Earth-launched probes, etc. I was hoping to get some feedback on this from this discussion group on feasibility. To recap, the first thing to be considered was, obviously, torquing...you know, tau = mu cross B. This torque seeks to minimize the magnetic interaction energy by minimizing the angle between mu and B (aligning them, in other words). Next, in a non-uniform magnetic field, "there can be a non-zero translational force on the dipole" (quote from Jackson) equal to F sub D = grad(mu dot B) where the derivatives in grad are relative to the coordinates of the dipole's position vector. Now, the quantity in parentheses is the component of mu along B. Since the torque aligns the two, this is easy. Then, of course, the gradient of this quantity will be normal to B. So far, this doesn't look like it's going to be much help in changing the orbit's inclination, but it looks like the perturbative forces can be used to alter the orbit's semi-major axis and the orbit's semi-latus rectum. However, the Earth's magnetic dipole axis isn't aligned with the Earth's spin axis (by some 11 degrees), so it ought to produce some component of force in the direction of increasing orbital inclination (i.e., increasing latitude). The other components can, then, be directed radially outward and in the direction of increasing velocity (or inward/decreasing, for that matter), since the current magnitude and direction are controllable. The primary problem is, as usual, the amount of power available to sustain current flow. Until I refine my model, assuming no stupid errors on my part, I won't have any ideas of the magnitude necessary. One interesting idea I came up with was to run a current through the solenoids only when the probe was close to Earth, that is in the region of perigee. During the rest of the time, a major part of each orbit, the lowered magnetic field (both terrestrial, up to about 6 Earth radii, and solar further away) might be used to induce current flow in the loops that could be used to generate some power anyway. The biggest problem would be that terrestrial/cis-lunar solar magnetic fields are always fluctuating. Solar wind fluctuations would also create problems. Rather than try to maximize the input, it might just be better to use what comes through. Another problem, briefly mentioned in the last paragraph, is the variety of magnetic field strength and direction over a given orbit and the non-constancy from orbit to orbit. I was thinking that a magnetometer might precede the probe by a distance sufficient to allow the probe's circuitry time enough to react to changes in field strength and direction. By comparing the upcoming field with an internal gyroscope and the desired effects, I don't see any reason why the current through the loops can't be adjusted quickly enough to provide some measure of stability in orbital modification. Regular communication of radar ranging data can correct error build-up before it becomes too problematical. Now, extending a boom that far in the direction of the probe's velocity will require extending another one "down" (i.e., anti-parallel to probe's position vector) with a mass and length sufficient to stabilize the probe's orientation, gravity gradient style. One benefit of this design suggestion is that, unlike solar sails, atmospheric drag is not likely to be much of a problem...most of the loops are empty space...so that short position vectors are the problem as they are with solar sails. I've reviewed other NASA publications pertaining to the above ideas. Most of them are 15-20 years old so, if anyone knows of any suitable publications that are more current, please let me know. The ones I've used are: N72-30468 NASA-SP-5110 1972 The Alloy with a Memory, 55-Nitinol: Its Physical Metallurgy, Properties, and Applications N69-30339 NASA-SP-8018 Mar 1969 Spacecraft Magnetic Torques: NASA Space Vehicle Design Criteria N69-40269 NASA-SP-8017 Mar 1969 NASA Space Vehicle Design Criteria- Environemnt. Magnetic Fields: Earth and Terrestrial N70-23418 NASA-SP-8024 May 1969 Spacecraft Gravitational Torques: NASA Space Vehicle Design Criteria N71-24312 NASA-SP-8027 Oct 1969 Spacecraft Radiation Torques: NASA Space Vehicle Design Criteria I've also developed an Excel (MicroSoft; MacIntosh) spreadsheet to yield numerical values - and am developing a Mathematica (Wolfram) notebook to yield symbolic results - for calculations of Earth's magnetic field for various position vectors. I am currently trying to figure out a macro to do partial differentiation in the spreadsheet. Once that's done, a magnetic moment switching routine can be included and a Monte Carlo simulation can be run over all latitudes and longitudes to get an idea of the average force components. Fortunately, I can justify this at work. From that, an idea/guess of the time to reach lunar polar orbit can be determined. I realize that most of the planners of the LPP and the conference are considering rockets for orbital insertion, but I'd still like to provide an alternative. Any suggestions? Steve Abrams sedspace@doc.cc.utexas.edu ------------------------------ Date: Mon, 30 Jan 1989 18:18-EST From: Marc.Ringuette@DAISY.LEARNING.CS.CMU.EDU To: sedspace@doc.cc.utexas.edu Subject: Re: Magnetic Induction Propulsion? From: sedspace@doc.cc.utexas.edu (Steve Abrams) > I realized that the current loop could be expanded into several, solenoidal > loops ... By running currents through the various solenoids, the craft would > be torqued into various attitudes ... I was hoping to use this magnetic > interaction to alter the orbital parameters. What you suggest looks to be a means of turning electricity into thrust. But that's what ion propulsion is about, and it seems much more direct. Is there any reason to believe this is more effective than ion propulsion for some set of mission parameters? Seems to me that if you're going to need electrical power anyway, there isn't much reason to bother with big strings of nitinol wire. It's only if you have a low-mass way to use sunlight without generating electrical power - such as a solar sail - that such large structures gain appeal. Perhaps it's time to think about other ways of "rigging" solar sails, since the electricity required to heat Nitinol wires seem to be such a problem. ----------------------------------------------------------------------------- | Marc Ringuette | mnr@cs.cmu.edu | Holy cow, Batman! | | CMU Computer Science | 412-268-3728(w) | -- watch this space for other | | Pittsburgh, PA 15213 | 412-681-5408(h) | quotes from great literature | ----------------------------------------------------------------------------- ------------------------------ Date: Thu, 2 Feb 89 23:58:36 CST From: sedspace@doc.cc.utexas.edu (405986289 abrams) To: space-tech@cs.cmu.edu Subject: Re: Magnetic Induction Propulsion? >From : >What you suggest looks to be a means of turning >electricity into thrust... No, Marc, this isn't the same as ion propulsion where a propellant is carried on-board and thrown away and eventually depleted and I thought I was clear in expressing the fact that this doesn't involve solar sails ("the danged sail films kept getting in the way...so, I trashed them"). What I'm talking about is a fundamental interaction between electromagnetic fields...no mess, no bother. As I mentioned, I planned this for a lunar polar mission, but it could be adapted to any cis-lunar misison where time isn't essential. As usual, I don't intend this to replace anything, but I can think of situations where it might complement a mission. It would only be appropriate where there are significant magnetic fields, such as in near- and middle- Earth orbit. One advantage I see is that part of the interaction energy comes from the convection currents in Earth's interior that drive Earth's magnetic field. Like solar energy, it is energy that is just lying around waiting to be used. This relates to my ongoing desire to develop/promote spacecraft that "live off the land," as it were, and don't require re-fueling constantly to maintain effectiveness. I think this can be important because we know know how to manipulate currents and spacecraft materials more than we know how to manipulate large solar sails. The nitinol loops aren't there primarily for power generation, but for propulsion. I mentioned the idea of power regeneration only as a possibility for extending the effectiveness of any on-board power supply. The power I'm talking about *can* be minimal -- I haven't yet been able to derive an appropriate expansion to describe the minimum power necessary to overcome atmospheric drag, etc. at a given orbital radius. Everytime I mention nitinol usage, Marc, you jump on it. I continue to consider its usage because it is something that is manufactured TODAY and doesn't require more development (refinement, perhaps) and the problems that plague nitinol applications down here on Earth (fatigue stress due to large numbers of heat/cool duty cycles) aren't a problem since, in the applications I see, a minimal current is continually maintaining the structure through dissipative losses. Since the resistivity of the gauge nitinol wire is about 80 micro-ohms/cm and I'm only talking about, say, current loops with a radius of 100 m, we're talking about resistances considerably less than an ohm per loop. Multiple loops (i.e., a solenoid) increase the effective area significantly with little overhead; increased areas increase the magnetic moment; increased magnetic moments yield increased displacement forces. Currents of only 1 amp in loops of this size generate significant magnetic moments -- in the NASA study I cited, residual spacecraft magnetic moments (which they wanted to minimize) were of this same order and effected significant alteration of orbital parameters. Conventional power supplies can provide this level of power. Increasing the current or the number/size of the loops (which, since the diameter of the wires is only 5 one-thousands of an inch, adds little extra mass) greatly enhances the effectiveness since the displacement force is proportional to the magnetic moment. I agree that this is a large structure, but it is self-rigidizing and is mostly empty space. Again, you deny the entire idea because "the electricity required to heat Nitinol wires seem to be such a problem." Obviously, you still have this confused with the thermoreflectance modulation of solar sails. I'm sorry that I wasn't more clear about this. Well, the power necessary to heat some wire a couple of hundred degrees C is obviously not of the same order of magnitude as that required to heat a large aluminum film 7-800 degrees C (especially since there isn't such a large surface radiating it away). I don't mean to flame, but I thought that this was supposed to be the type of discussion group where people would take some time to investigate the theory and the numbers pertaining to an idea before trying to shoot it down. Obviously, from the speed of your response, you didn't. While I didn't give numbers, I did provide the necessary formulae and references. I would've hoped that some thought would've been given to any reply. [While looking back over my message, I did notice one error: "that short position vectors are the problem ^^^ |--> "aren't" as they are with solar sails." My apologies for this.] Perhaps, Marc, you can answer a question more specifically oriented to your major field. In radiation-hardened microprocessors, what's the current maximum number of FLOPs per second? If the ouput of a magnetometer can be compared to that of a gyroscope and current magnitude/direction in six loops be adjusted in under a tenth of a second, then the probe can "sniff ahead" and determine the appropriate response to the upcoming magnetic field in order to produce the desired displacement force magnitude/direction. Steve Abrams sedspace@doc.cc.utexas.edu ------------------------------ Date: Fri, 3 Feb 89 14:07:31 EST From: dietz@cs.rochester.edu To: sedspace@doc.cc.utexas.edu Cc: space-tech@cs.cmu.edu Subject: Magnetic Induction Propulsion? How much power is needed to heat a 100 m diameter loop of .005 inch wire? It has a surface area of about .125 square meters. If it is heated to 500 K it radiates 444 watts, assuming it is a black body. I don't know the emmissivity of nitinol; let's assume it radiates 200 watts. Perhaps this can be reduced more with (for example) a gold coating. How much thrust could you generate by interacting the earth's magnetic field gradient? The force is pi I r^2 dB/dx, where I is the current, r the loop radius and dB/dx the rate of change of the field perpendicular to the loop. Assuming the earth's field is about 10^-4 T and drops to zero in 1000 km (wrong, but roughly correct) and letting r = 50 m, I = 14 amp, we can estimate that the force is about pi 14 amp 50^2 m^2 10^-10 T/m or 10^-5 newtons. In contrast, an ion engine expelling matter at 30 km/s and using 200 watts at 50% efficiency would generate a thrust of 6.7e-3 newtons, over 600 times larger. The ion engine would be much more massive than the wire, but the total mass including the power supplies would be roughly comparable. One problem with the magnetic loop scheme is that the loop's magnetic field will interact with the ambient plasma, causing drag. The field drops to one gauss at a distance of about 11 inches from the wire, in this example. This suggests we use a scheme in which electromagnetic fields push on the ambient plasma. Perhaps power could be supplied with transmitters on the ground exciting currents in large, thin arrays of conductors? Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: 3 Feb 89 15:39 From: klaes%mtwain.DEC@decwrl.dec.com (CUP/ML, MLO5-2/G1 8A, 223-3283) To: space-tech@cs.cmu.edu, LARRY%mtwain.DEC@decwrl.dec.com Subject: Articles from CANOPUS which may interest/help our group's work. PLANETARY RESEARCH ANNOUNCEMENTS RELEASED - can890104.txt - 12/29/88 NASA has issued three Research Announcments for the planetary science community this month. Planetary astronomy program. NRA-88-OSSA-14 Issue date: Dec. 19, 1988 Deadline: March 31, 1989 (March 31, 1990) Selection date: June 1989 (June 1990) Level of effort: $8 million; 100 investigations. Topic: Ground-based observations of all solar system bodies (except the sun), with limited funds for development of new instrumentation, to support basic research in support of planetary program objectives and for direct support of specific flight missions. Submit proposals to: Lunar and Planetary Science Institute Attn: Planetary Astronomy Review Panel NRA 88-OSSA-14 3303 NASA Road 1 Houston, TX 77058 For copies of the NRA contact: Jurgen Rahe, Discipline Scientist Planetary Astronomy Program NASAQELC Washington, DC 20546 (202-453-1597; FTS 453-1597) ----- Planetary instrument definition and development program. NRA-88-OSSA-15 Issue date: Dec. 19, 1988 Deadline: March 31, 1989 Selection date: June 1989 Level of effort: $1.4 million; 10 to 20 new investigations. Topic: Advancement of spacecraft-based instrument technololgy which shows promise for use in scientific investigation in future planetary missions, both remote sensing and in situ. In general the areas of interest are outlined in the reports of the Solar System Exploration Committee, "Planetary Exploration Through Year 2000: A Core Program" and "-----: An Augmented Program." Missions of current interest are the Saturn orbiter/Titan probe (Cassini mission) and the Lunar Geosciences Observer. Mars and comet sample return missions are covered in this NRA with less emphasis. Submit proposals to: Planetary Instrument Definition and Development Program Attn.: NRA 88-OSSA-15 NASAQEL Washington, DC 20546 For copies of the NRA contact: Paul Mahaffy, Discipline Scientist Planetary Instrument Definition and Development Program NASAQEL Washington, DC 20546 (202-453-1597; FTS 453-1597) ----- Planetary geology, geophysics, cartography, and geologic mapping. NRA-88-OSSA-16 Issue date: Dec. 23, 1988 Deadline: July 31, 1989 Selection date: September/October 1989 Level of effort: $10 million for FY 90; 150 investigators. Topic: Investigation of planets and small bodies in research areas including generation of new data, analysis and synthesis of existing data, or a combination. This may be accomplished by laboratory experimentation, photointerpretation, theoretical, field and comparative studies, and cartographic research compilation. The 1:500,000 Mars geologic mapping program is included. Submit cartography proposals to: Joseph Boyce, Discipline Scientist Planetary Geosciences Programs NASAQEL Washington, DC 20546 (202-453-1597; FTS 453-1597) Submit all other proposals to: Lunar and Planetary Science Institute Attn: Lunar and Planetary Geoscience Review Panel NRA 88-OSSA-16 3303 NASA Road 1 Houston, TX 77058 NASA SEEKS NEW STARTS FOR TWO PLANETARY MISSIONS - can890110.txt - 1/9/89 "New starts" are sought for the Comet Rendezvous/Asteroid Flyby and Cassini Saturn/Titan missions in the fiscal 1989 budget proposed today for the National Aeronautics and Space Administration. The $13.3 billion budget plan is almost $2.4 billion higher than the current $10.9 billion budget NASA has for fiscal 1989. The largest increase is a $1.1 billion jump for the Space Station program. Small gains are made in physics and astronomy and other science budgets, and the NASA payroll is to increase by 700 permanent positions. In releasing the budget proposal, NASA Administrator James Fletcher said that "the space program is back on track. Our challenge now is to keep it on track and in forward motion toward our long-range goals." He noted that the FY90 budget "is almost exactly the amount forecast a year ago when we presented the FY l989 budget to Congress." He later commented that, "The budget provides $2 billion to move ahead with development of the Space Station. The development plan and basic configuration are firm, and the development contractors are making substantial progress. We are moving toward a first element launch in early l995 with a capability for man-tended research activity by the end of that year and a permanently manned capability by the end of l996. Our international partners are at work consistent with this plan and with the agreements approved last fall." The CRAF and Cassini missions are proposed as a dual new start to save money (compared to two separate programs) by using a common Mariner Mark II bus design and spares. Funds for several programs - Hubble Space Telescope, Gamma Ray Observatory, Galileo, and Magellan - drop as these projects approach flight in 1989. Others - Advanced X-ray Astrophysics Facility, Global Geospace Science - rise sharply compared to FY89 funds. In all the Office of Space Science and Applications has a budget request of almost $2 billion, up from $1.8 billion at present. The $341 million construction of facilities category includes $12 million for a data operations facility at Goddard Space Flight Center and little else of interest to the space science community. NASA FY 1990 BUDGET SUMMARY (Millions of Dollars) NATIONAL AERONAUTICS AND SPACE ADMINISTRATION FY1989 FY 1990 RESEARCH AND DEVELOPMENT 4266.6 5751.6 SPACE FLIGHT, CONTROL & DATA COMM. 4464.2 5139.6 CONSTRUCTION OF FACILITIES 275.1 341.8 RESEARCH & PROGRAM MANAGEMENT 1891.6 2032.2 INSPECTOR GENERAL (8.6) 8.8 TOTAL BUDGET AUTHORITY 10897.5 13274.0 =========================== ======= ======= OUTLAYS 10678.0 12706.8 FULL-TIME EQUIVALENTS 23,150 23,846 ================================================================== DETAILED BREAKDOWN FY 1989 FY 1990 [ I chopped this; it's pretty long. Ask for it if you want it. -- Marc ] CANOPUS is published by the American Institute of Aeronautics and Astronautics. Send correspondence about its contents to the executive editor, William W. L. Taylor (taylor%trwatd.span@star.stanford.edu; e-mail to canopus@cfa.uucp will probably be forwarded). Send correspondence about business matters to Mr. John Newbauer, AIAA, 1633 Broadway, NY, NY 10019. Although AIAA has copyrighted CANOPUS and registered its name, you are encouraged to distribute CANOPUS widely, either electronically or as printout copies. If you do, however, please send a brief message to Taylor estimating how many others receive copies. CANOPUS is partially supported by the National Space Science Data Center. ------------------------------ End of Space-tech Digest #25 *******************