Date: Tue, 20 Sep 1988 17:58-EDT From: space-tech-request@CS.CMU.EDU To: "~/st/lists/stdigest" Subject: Space-tech Digest #6 Contents: Paul Dietz The Utility of HEEO vs. LEO Steve Abrams Catching Up Is Hard To Do... Steve Jensen Re: Catching Up Is Hard To Do... Per Hammarlund Re: Catching Up Is Hard To Do... Matt Burdick Re: AMSAT Paul Flaherty Re: AMSAT Bob Summersgill design of a satellite Ollie Eisman Re: design of a satellite Joe Beckenbach Re: design of a satellite ------------------------------ Date: Mon, 19 Sep 88 13:50:41 EDT From: dietz@cs.rochester.edu To: Marc.Ringuette@CS.CMU.EDU Cc: space-tech@cs.cmu.edu, dietz@cs.rochester.edu Subject: The Utility of HEEO vs. LEO Marc asked what do we do with an EML that can launch to HEEO. I think a major use would be as a component in a system to explore the inner solar system. The major cost (in delta-v) of getting to Mars or the near-earth asteroids is the cost of escaping the earth's gravity well. A spacecraft in HEEO can fire its rockets at perigee (where they give the craft the most energy) and enter useful interplanetary transfer orbits with surprisingly small delta-v. In an ideal case, entering a Hohmann orbit to Mars from HEEO requires a delta-v of less than 1 km/sec. In a sense, HEEO is already 3/4 of the way to Mars. For visiting NEAs, delta-v could be equally small. For example, it costs 4.4 km/sec to get to 1982 DB from LEO. Leaving from HEEO, the cost would be about 1.2 km/sec (4.4 - 11 km/sec + 7.8 km/sec). Return from 1982 DB costs .1 km/sec using aerobraking. There is every reason to believe that more accessible asteroids exist. I'm not proposing using spacecraft launched by EML to visit asteroids. Rather, the EML will launch bulk materials to an operations center in HEEO. Things that could be launched include: rocket fuel, shielding material, food, air, water. I imagine launching (perhaps in sections) a stripped-down manned asteroid exploration vehicle to LEO. In LEO, sufficient fuel (brought down from HEEO by aerobraking) is added to boost the vehicle to HEEO. Once in HEEO, a full stock of consumables is added, and the fuel tanks refilled. When the vehicle returns from a journey, it stays in HEEO and is refueled there, using primarily materials launched by EML. A problem with escaping from HEEO is that one has to be in the right HEEO, or one ends up going in the wrong direction. So, we'll need some scheme for sending interplanetary spacecraft from one HEEO to another. Probably the best scheme is to boost the outgoing spacecraft into an extremely elliptical orbit, then maneuver it (perhaps with the help of lunar and solar gravity) to pass the Earth in the right trajectory. Some other points... Getting down from HEEO to LEO doesn't necessarily mean aerobraking in one pass. If one can brake over many passes, one can dissipate less heat on each pass, and the aerobrake can cool by radiation rather than by ablation. Also, one pass of aerobraking takes minutes rather than seconds, and passes through the upper atmosphere, so the heating is not nearly as bad as blasting through the troposphere at 12 km/sec. It makes more sense to use high thrust low efficiency engines, like chemical rockets, with EMLs rather than ion engines or solar sails. The reason is that one can fire a rocket at perigee, where it is more effective; solar sails or ion engines do most of their work far from perigee, where the vehicle is travelling more slowly so less energy (thrust x distance) is added/removed from the vehicle. Also, launching from HEEO reduces the delta-v, so there's less need, for many missions, to get high Isp. Rockets are not that expensive if they don't have to provide maximum performance. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Sun, 18 Sep 88 02:15:39 CDT From: sedspace@doc.cc.utexas.edu (Steve Abrams) To: space-tech@cs.cmu.edu Subject: Catching Up Is Hard To Do... ...but I've finally done it (with respect to this group anyway). Things are looking GREAT, Marc!!! There are several things I want to respond to/inquire further about. To Per Hammarlund One of the first questions that I would like to put is: Is it possible >for a distributed group, like this mail-list, to construct, on paper, >a small satellite? Does the group contain the skills necessary? I hope so. At the SEDS International Conference in Houston three weeks ago, interested members formed a Space Technology SIG (Hiya' Ollie!!!) and one of the ideas strongly discussed was the design, launch, deployment, and control of a satellite. The discussion was sparked by Ollie Eisman who is trying to develop a satellite-tracking facility (monitoring telemetry and other transmissions) at the University of New Mexico as a project for his SEDS chapter. I chimed in with my desire to do *optical* tracking via blink comparator here at UT-Austin and the probable interest of the University of Kentucky SEDS chapter (who have built a radiotelescope and need something to evolve towards). Additionally, there is an unused radiotelescope facility suitable for refurbishment at the Bee Caves facility for our Astronomy dept. Other people started getting real interested and the discussion led to our desire to launch our own satellite (reps from private launch companies allege that they will provide "piggy-back" opportunities on a space-available basis) and monitor/control it ourselves. (Note: We don't care about the politics and legalities of this, only the technology) I'm thinking along the lines of a coffee-can-sized satellite with very few sensors and conventional shortwave for the up/downlink. I'm trying to talk to people at Tracor, Inc. to see what miscellaneous junk they have laying around (they do a lot of satellite design and testing) and if there is anyone interested in advising us. Of course, people who know me know that I rarely think of anything without some connection to solar sails. What I, personally, would like to investigate is the feasibility of launching a small sat into a HEEO, monitoring and controlling it from the ground, deploying a small sail, and pumping its orbit until it impacts the Moon. Rough (very rough) estimates indicate that the entire project could be accomplished on a timescale of 3-4 years. The sail could be thin-film aluminum or doped trans-polyacetylene (conducting polymer) on a nitinol frame. The former has a high reflectance, but lower variance due to thermal heating while the latter is vice-versa. As I describe in my solar sail posting, running a current through the frame heats the frame keeping the film taut and, additionally, heats the film. As the film heats, the reflectance varies. Varying the reflectance to pump the orbit eliminates the need for extensive facilities for "tilting" the sail (although this is quite feasible with a 100 m^2 sail). The control functions could be handled on the ground by academic mainframes, thereby minimizing the processing mass "on-board", if reliable communications can be had. For this, I think that low-power lasers should be adequate (what kind of attenuation do you get in traversing the atmosphere?) for the uplink. Another nitinol frame backing the sail could re-shape the sail to focus/reflect the laser signals onto a charge-coupled device for interpretation. Would a shortwave be more feasible? How about for the downlink? The power would probably have to be provided by radioisotope thermal generators since a sail this size doesn't intercept enough solar radiation to provide enough. Does anyone have any data on the mass of RTGs? What would be the technical problems involved? Physically, these ideas are sound...engineering is another matter. Is there any interest in this group for discussion? ***************** To Paul Dietz : >You asked if 6000 gravities is too high for boosters or electronics. >The answer for electronics is "no". Proximity fuses in artillery shells >tolerate accelerations of this magnitude or higher -- even with WWII >technology. Some SDI schemes have proposed smart projectiles launched >at 500,000 gravities in orbiting railguns. ^^^^^^^ ||||||| Do you have any information on how such high accelerations affect the electromagnetic properties of the "buckets/shells" carrying the payload? As I understand your EML discussion, the payloads are magnetically levitated by current induction. Although I share Gordon Pusch's distaste for Condensed Matter physics, I do know that the optical properties of metals vary with pressure (this is used to investigate the electronic structure of the metal). Presumably, if the electronic structure of the shell is being changed via barymodulation, so are its "current induction" properties. The effect would be slight for aluminum shells, but I should think they would be greater for other materials. Is this considered in calculations for these types of railguns? Is it trivial? Steve Abrams ------------------------------ Date: Sun, 18 Sep 88 23:22:50 -0400 (EDT) From: Steven Kent Jensen To: space-tech@cs.cmu.edu Subject: Re: Catching Up Is Hard To Do... *> Excerpts from mail: 18-Sep-88 Catching Up Is Hard To Do...* > *405986289 abrams@doc.cc. (5616)* > To Per Hammarlund >One of the first questions that I would like to put is: Is it possible > >for a distributed group, like this mail-list, to construct, on paper, > >a small satellite? Does the group contain the skills necessary? > I hope so. At the SEDS International Conference in Houston three > weeks ago, interested members formed a Space Technology SIG (Hiya' > Ollie!!!) and one of the ideas strongly discussed was the design, launch, > deployment, and control of a satellite. Ham radio operators have had their own satellites for years. I believe that there are 11 in the Oscar series now. The earliest Oscars were transmitters crammed into coffee cans. Since then the Oscars' standard equipment has included beacons and radio relay equipment. This allows hams to get short contacts with very distant hams by using the satellite to relay their signal. The satellites were built by AMSAT members. Therefore we have an example that it is possible for a distributed group such as ours to put up a satellite. They have been getting orbits of ~4000 kms and Oscar 10 was 'kicked' into a 35495 - 4000 orbit. As for power I could not find many details in the library, but they do use solar cells and battery backup, the batteries being recharged occasionally giving a lifetime of several years (some have continued to work when in sunlight after the batteries died). Steven Jensen ------------------------------ Date: Mon, 19 Sep 88 14:41:58 +0200 From: mcvax!nada.kth.se!d85-per@uunet.UU.NET (Per Hammarlund) To: space-tech@cs.cmu.edu Various comments on Steve Abrams letter: > I'm thinking along the lines of a coffee-can-sized satellite >with very few sensors and conventional shortwave for the up/downlink. >I'm trying to talk to people at Tracor, Inc. to see what miscellaneous >junk they have laying around (they do a lot of satellite design and >testing) and if there is anyone interested in advising us. Is it possible to get an estimate of the size that could become free, ie how large is the piggy-back-space? I think we should go for the largest space/weight that is likely to become free. > Of course, people who know me know that I rarely think of >anything without some connection to solar sails. What I, personally, >would like to investigate is the feasibility of launching a small sat >into a HEEO, monitoring and controlling it from the ground, deploying >a small sail, and pumping its orbit until it impacts the Moon. Rough >(very rough) estimates indicate that the entire project could be >accomplished on a timescale of 3-4 years. I see no reason to dump it on the Moon. It would be much more fun having it flying around out there while we work on incrementally vbetter algorithms for attitude control and navigation etc. If we should dump it, then why not chose some place that has not been taken already, like a asteroid. I haven't the letter on solarsails you mention. But a 100 m^2 a bit small, isn't it? How much space would a usable solarsail take, in m^3. And what would it weigh? Do you have some m^2 to m^3 conversion table? > What would be the technical problems involved? Physically, >these ideas are sound...engineering is another matter. Is there any >interest in this group for discussion? I, at least, am interested in a project like this. Could we try to decide on what to do and then try to work out a solution. Why not go for a "small" craft with solarsail and some navigational abilities and large processing capabilities? Some simple sensors like CCD's etc. Preferably cheap technologies in parallel than really expensive ones. These are some of the technological fields that needs to be covered, there are certainly quite a few more. Please make suggestions in the fields that you are interested in. **** Radio & Communication: **** Solarsail: **** Navigation: **** Attitude (Might fall under the solarsail, should that be the only "engine" aboard.): **** Power (Includes batteries, solarcells, etc.): **** Mechanical (Thermodynamic- and stress analyze of the frame.) **** Computer (Should there be a computer? If so should it be fast and versatile or specialized?): Being a computer scientist this is the field where I will and dare have a say. I would like to have a large processing capacity onboard. This would, with good software, ensure the survival of the craft while communication is down or bad, with good errordetection and correction. The exact power of the computer can only be decided when the number of sensors and other tasks have been decided on. Then we take that number and multiply by 3.14. to have the real, useful number. To handle failing and bad chips - and other parts - I suggest that there should be a large number of fast and versatile processors onboard the craft. Each processor should be able to do each task that might be nessecary to perform, there might be practical limits to this. The tasks that have to performed should be rated according to how important they are for the survival of the craft. Risky tasks should be performed by several PE (Processor Elements) with a majority decision at the end and low risk tasks should only occupy a single PE. An example of their work: Assume there are 8 PE of which 5 is engaged in computational tasks like: Datacompressing, Errorcorrection, radiocommunication etc. If a navigational task is coming up then all the free should try to perform it. **** Sensors: If anybody have suggestions on what should be incorporated then state them, estimate the weight, size (Shape, density etc) and power requirements (Can the power be shut of from time to time?) of each part you suggest. When we have enough good suggestions we decide on which to incorporate. Questions relating to Steven Jensen's letter: > Ham radio operators have had their own satellites for years. I >believe that there are 11 in the Oscar series now. The earliest >Oscars were transmitters crammed into coffee cans. Since then the >Oscars' standard equipment has included beacons and radio relay >equipment. This allows hams to get short contacts with very distant >hams by using the satellite to relay their signal. The satellites >were built by AMSAT members. Therefore we have an example that it is >possible for a distributed group such as ours to put up a satellite. Is it possible to have shematics, descriptions? I think I have read that these Oscars didn't use radiation hardened chips in their computers!?! Or was that some kind of data packet transfer vehicle, that had to use large amounts of RAM? Please enlighten me! /Per Hammarlund ------------------------------ Date: Mon, 19 Sep 88 19:51:28 PDT From: Matt Burdick To: space-tech@cs.cmu.edu Subject: design of a satellite A number of people have been talking about a cooperative venture to design a satellite, and the Oscar satellites put up by AMSAT have also been mentioned. Since I have a blurb about them sitting in front of me, I thought I'd post what I have. You can reach AMSAT at: AMSAT PO Box 27 Washington, DC 20044 I don't know how they've been doing lately, but the blurb I have says that they were planning on putting up a low-altitude store-and-forward packet radio satellite in June of this year (obviously a little out-of-date). They were also planning on geostationary repeater satellites at some time. Apparently, you can get AMSAT news in the rec.ham-radio group. Matt Burdick burdick%hpda@hplabs.hp.com ------------------------------ Date: Tue, 20 Sep 88 11:01:56 PDT From: Paul Flaherty Subject: Re: design of a satellite To: burdick%hpindl1@sde.hp.com, space-tech@cs.cmu.edu AMSAT has the following in the works: 1. Four "microsats", which are going up on Ariane next year. Two of these will be store and forward pacsats, two will be instrumentation sats. 2. AMSTAR, aka Phase IV, a geosynch due out in 1993 or so. The definitive net.person for AMSAT is Phil Karn, karn@thumper.bellcore.com; I'm working on a chunk of the AMSTAR Digital Community Access System. -=paulf ------------------------------ Date: Mon, 19 Sep 1988 18:42 EDT From: Bob Summersgill Subject: design of a satellite To: Space-tech Steve- In response to your suggestion of this group designing (on paper at least) a satellite; I am currently involved in trying to bring about the development of a lunar polar probe (orbiter and prospector are names for it). I have had some contact with launch companies and at this point I don't consider launch to LEO a problem. Obviously you are the local guru on solar sails, but what are other (cheap and/or available) upperstage systems available for LEO to Lunar Polar Orbit (LPO)? I assume that you are familiar with the World Space Foundation and their solar sail project. Is this a currently feasible and realistic option? The initial estimates for an LPP range from $2 to $20 million. Momentarilly ignoring this point; can this group muster the technical ability to design (on paper - on screen?) a design for a space ratable craft with a real purpose? Now for a bit of background: If any significant expansion into space is going to occur, there will be a definate need to eventually go to the moon. The moon is a wealth of materials that are available to those who go and get it. By mass the moon is 42% Oxygen, 21% Silicon, 12(?)% Alluminum, 8% Calcium, 6% Iron, with various trace materials. Research conducted by SSI has demonstrat- ed our ability to separate these elements. All that is missing are the life sustaning: Nitrogen, Carbon, and Hydrogen. There is some theoretical evidence that water ice may exist in the permanently dark craters in the polar areas. The key word being 'may.' All of the missions to carry gamma-ray spectrometers to the moon have been in equitorial orbits or simple fly-bys. No complete map has ever been constructed of the lunar surface in the gamma-ray end of the spectrum. Such a map would be needed to locate and utilize lunar hydrogen. The existence or non-existence of lunar hydrogen will have a profound effect on the design of a lunar base. The difference is so significant that the 2 million low-end price would not be blinked at, and the $200 million upper-end is a bargain. That is assuming that you have the goal of getting of the planet. A conference on this subject will be held May 11th & 12 in Houston. It would be highly advantagous to have a preliminary design at that time. So agin my question is: can this group muster the technical ability to design a cheap satellite on paper that would be capable of real use? -rjs ------------------------------ Date: Mon, 19 Sep 88 22:03:14 MDT From: SPACE EXPLORATION To: burdick%hpindl1@sde.hp.com, space-tech@cs.cmu.edu Subject: Re: design of a satellite Hello everyone! It's great to see all of this interest in building a satellite. Here are my thoughts: o Satellite control system: I think it would be best to use fairly high (VHF or higher) frequencies to send commands to our satellite. Shortwave was mentioned, and should not be ruled out....much easier to both send and receive signals from the satellite when its exact location is not known. However, HF is noisy and cannot support the data rates necessary when dealing with a LEO satellite. A 2400 baud link, or even 1200 baud link with the satellite would be nice. I like the idea of a SEDS "Tracking and Data Relay Network." There could be several control stations around the world to use the satellite on different orbits. Communications between control stations would be a priority...both for the satellite's safety and for the experiments on board. The University of Surrey's UoSAT Spacecraft Control Centre should be examined closely. They have successfully designed, constructed, launched (via NASA), and operated two UoSATs (OSCARs 9 and 11) to date. Both are still in orbit and functioning well. o Ok, just what do we want this bird to do? I lean towards the solar sail idea. There is no need to compete with AMSAT and their (what should be) excellent packet radio satellites. Why not try something new and challenging! A 3-4 year mission (minimum) would require a great deal of coordination and stick-to-it-tiveness, but good things come to those... I'll use the Voyager program as an example. It took a while, but the results appear to be well worth it. How about this. I would like to conduct a survey among all space-tech subscribers. Answer the following questions and e-mail to seds@ariel.unm.edu I will combine all responses and post the results to the group. ----------------------------------cut----------------------------------------- -=-=-=-=-=-=-=-=-=-=- Satellite Idea Survey........please complete and mail to seds@ariel.unm.edu -=-=-=-=-=-=-=-=-=-=- by Wednesday, September 21. 1) What experiments would you like to see on board? (be realistic!) 2) What type of orbit would you like to see the satellite in? 2) Do you think the satellite should be an OSCAR (Orbiting Satellite Carrying Amateur Radio)? 3) How do you think we should get the satellite in orbit? (Ariane, Shuttle, high altitude balloon, etc) 4) Addtional comments/suggestions: ------------------------------------------------------------------------------- Ollie SEDS-UNM Satellite Tracking Station (SSTS) ------------------------------ To: mcvax!nada.kth.se!d85-per@uunet.UU.NET Cc: space-tech@cs.cmu.edu, joe@vlsi.caltech.edu Date: Tue, 20 Sep 88 10:09:32 -0700 From: Joe Beckenbach (mangler-in-training) >Why not go for a "small" craft with solarsail and some navigational >abilities and large processing capabilities? Some simple sensors like >CCD's etc. Preferably cheap technologies in parallel than really >expensive ones. Well, the Mars Observer Camera Porject here at Caltech is pushing the limits of NASA space-rating. I don't have costs for the arrays of CCDs that will be on the Camera, but each array is a line array. I think the narrow angle camera was aiming for a footprint of over 3 km with around 2500 CCD elements [raw pixel ~1.5m, single pass resolution 4-5m]. The two wide angle cameras [one red, one blue] have optimized 140 degree fisheyes and similar CCD arrays, with a raw pixel at 500m(?). Several ICs have been radiation tested, and there are commercially available untreated RAMs and ROMs which perform very outstandingly, even better than some "rad-hard" parts of smaller capability and higher power draw. I'm trying to get pointers to papers and parts from Scott Brylow, who is the MOC Ground Support Engineer [now essentially the Ground Support Staff as well]. The MOC of course needs a rad-hard microprocessor, I'm trying to get information on that as well. >**** Power (Includes batteries, solarcells, etc.): Make sure, DAMN SURE, that you know what the peak loads, normal loads, and power replenishment rates are. One JPL Mars Observer power plant proposal cut the batteries in half to reduce weight, ignoring the result which meant that of the hour that the MO stays in Mars shadow, it could run for only forty minutes WITH EVERYTHING TURNED OFF. This proposal actually cleared to outside the initial group before the inconsistancy was noted, and it sunk without a trace. >**** Mechanical (Thermodynamic- and stress analyze of the frame.) Shake tests and thermal-vacuum chamber tests can help characterize for launch vibration and structural/functional variation due to changes in temperature and pressure. The temperature flux is important especially for any orbit which nceessarily comes in and out of shadow with precision instrumentation sensing craft conditions or making remote measurements. >**** Computer (Should there be a computer? If so should it be fast and >versatile or specialized?): There are the tradeoffs between ability to do fast calculating and the ability to survive or ignore radiation "single event upsets". In low earth orbit this is not necessarily a concern, but once the computer is out beyond the inner regions of the inner Van Allen Belt, this is vital. How much of a tradeoff is it to go back to vacuum tubes? No smiley, because all you need for immense numbers of vacuum tube circuits is access to clean shadowed vacuum, easy for a nonspun craft, or a light-baffled box. The vacuum tube solution [or rather, unpackaged vacuum components solution] is accorded a very favorable resistance to radiation. Hmm, perhaps an experiment to try on the crafts which will be diving above the Van Allen Belts? >I would like to have a large processing capacity onboard. This would, >with good software, ensure the survival of the craft while >communication is down or bad, with good errordetection and correction. >The exact power of the computer can only be decided when the number of >sensors and other tasks have been decided on. Then we take that number >and multiply by 3.14. to have the real, useful number. Question: why pi? Irrationally large safety factor? :-) :-) >To handle failing and bad chips - and other parts - I suggest that >there should be a large number of fast and versatile processors >onboard the craft. Each processor should be able to do each task that >might be nessecary to perform, there might be practical limits to >this. If one can keep the expected failure rate low, this need not be. In fact, MOC is trying to put on a large [by space flight standards] gate array to handle several different minor tasks. >The tasks that have to performed should be rated according to how >important they are for the survival of the craft. Risky tasks should >be performed by several PE (Processor Elements) with a majority >decision at the end and low risk tasks should only occupy a single PE. Might it be better to place some of the functionality in hardware? I mean, if the choice between a single proton upsetting an imaging processor and a single micrometeorite upsetting an imaging processor has to be made, all things being equal, I'd take the second. It's much less likely to happen. Hardwired silicon paths on printed boards are harder to take out than random bits in a ROM, though the processed time is two or three orders of magnitude slower, I would guess. >An example of their work: Assume there are 8 PE of which 5 is engaged >in computational tasks like: Datacompressing, Errorcorrection, >radiocommunication etc. If a navigational task is coming up then all >the free should try to perform it. The current Mars Observer setup places the responsibility of the data compression and error-correction on the instruments for instrument data, and handles the navigational with [I guess] one processor. If you go multi-processor for navigation, you'll definitely be breaking new ground. It might pay off, but the weight expense might be prohibitive. >**** Sensors: Rough estimate for the Mars Observer Camera with all electronics: 6.5 kg, 10 watts peak, 90cm long by 35 cm wide by 45 cm high [long axis to Mars] for instrument envelope, plus additional box for electronics about 15 cm by 20 cm by 30 cm. 12M RAM, 1 rad-hard shielded microprocessor, custom fabricated circuit boards to implement the imaging compression methods, and special error-correction-coded ROM for flight software. Power minimum around 0.5 watts or less for on-board heaters to keep the alignments correct for shadowed section of orbit [~30 minutes at that altitude of 140km, I think]. Can be powered down at any time given ten minutes warning to clear out imaging buffers by transmission (? rough). Joe Beckenbach ------------------------------ [ end of space-tech digest #6 ]