Subject: Space-tech Digest #65 Contents: Don Lindsay Re: Minicomets John Roberts Re: Minicomets Marc Ringuette Aim For The Moon - model rocket contest Vince Cate Re: Aim For The Moon - model rocket contest Vince Cate Re: Aim For The Moon - model rocket contest Vince Cate Re: Aim For The Moon - model rocket contest Marc Ringuette Re: Aim For The Moon - model rocket contest Paul Dietz Re: Aim For The Moon - model rocket contest Tom Neff Communicating with a 1oz Payload Paul Dietz Re: Communicating with a 1oz Payload Lou Adornato Re: Aim For The Moon - model rocket contest Marc Ringuette Re: Aim For The Moon - model rocket contest ------------------------------------------------------------ Date: Wed, 20 Jun 1990 18:22-EDT From: Donald.Lindsay@MATHOM.GANDALF.CS.CMU.EDU To: space-tech@CS.CMU.EDU Subject: Re: Minicomets John Sahr writes: >It is a very interesting >theory; even if it is wrong it has been posed and debated in a fashion >that is much more satisfying than "cold fusion." Well, almost. The June 1990 Scientific American, p.24 ("Death Watch", in "Science and the Citizen") has succumbed to snideness. They use words like "hallucinations" and try to leave the impression that Frank believes in UFOs. Maybe he does (they don't actually say). In either case, I'm not pleased at it being dragged in. Truth exists: if he is leading us to it, this was wrong: if he is leading is away from it, then the truth is a strong thing, and not in need of personal attacks to keep it safe. **Obligatory Space stuff** I phoned RAND's 800 number (as advertised on sci.space ) to ask for my SEI Outreach response packet. The operator didn't know how to type, or spell, but was Real Cheerful. So, be warned, don't phone just before an important appointment. Don ------------------------------ Date: Thu, 21 Jun 90 14:54:10 EDT From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. To: space-tech@CS.CMU.EDU Subject: Re: Minicomets I did read something very recently on the subject - probably in the weekly Science News. Somebody else looking at the upper atmosphere found evidence to support the comet theory. I may come across it again, or somebody else could post a summary. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Thu, 21 Jun 1990 15:42-EDT From: Marc.Ringuette@DAISY.LEARNING.CS.CMU.EDU To: space-tech@cs.cmu.edu Subject: Aim For The Moon - model rocket contest A recent thread on sci.space was started up by Vince Cate, who suggested a contest to send model rockets to the vicinity of the moon. Early discussion dealt with whether model rocket engines are good enough, and have enough specific impulse. I think there are some interesting questions we might want to look at: -> How can we signal Earth from a very light payload (say, 1oz.) ? -> How can we guide a multi-stage large model rocket to the moon? I'll attach the most informative messages from Vince, to get us started. I'd encourage y'all not to worry about the rocket motors for now, but to concentrate instead on the communications, guidance, and construction of the rocket. -- Marc ------------------------------ From: vac@sam.cs.cmu.edu (Vincent Cate) Subject: Aim For The Moon - model rocket contest Keywords: moon model rocket contest Date: 17 Jun 90 21:55:15 GMT 1992 marks the 500 year anniversary of Columbus' trip to America. It would be fun to commemorate this with an "Aim for the moon" model rocket contest. The goal of the contest could be to get a small transmitter near the moon as cheaply as possible (cost could be measured as total newton-seconds of thrust for all stages). The only restrictions would be that only off the shelf "model rocket motors" could be used and that the standard transmitter must be in the payload. I think this limits people to using "N" or smaller rockets. It seems that using a small rocket to send a small transmitter to the moon would be very possible. It would take a rocket with a number of stages starting with the larger size motors; however, I think you could do it without going so far as making a 10 stage rocket that starts with multiple "N"s. To save you some arithmetic, let me point out that an "N" has about 8,000 times the newton-seconds of an "A" motor. The Isp on larger "model" rocket motors is about the same as that used on "real" rockets. This means that, for each stage, the delta-Vs should be comparable to that of large rockets with a comparable fraction of total weight as fuel - except for air resistance. :-) If you only want to lift a very small payload it should be possible to do it with a reasonably small rocket. ... The rockets would be on the expensive side for model rockets (not for space in general) so whole clubs would probably work together on one entry to the contest. My guess is that a rocket could be built for under $5,000 in parts. Once there is a formal contest, kids could get sponsors and donations. Many clubs would be able to raise that kind of money for such a fun project. The radio could be made to transmit the names of the sponsors, designers, and builders. If lots of us recommend the idea to clubs and rocket manufacturers this might happen. Please pass the idea on. Such a contest would dramatically demonstrate the contrast between 1492 and 1992. Back then many people thought the world was flat, today kids all around the world can send rockets to the moon!!!!!!!! -- Vince PS I think the solar sail race to Mars is so neat that it would be fun to other things kind of like it. Since entering this contest is relatively cheap, it could let many people get involved. ------------------------------ [ There was more discussion on sci.space ... mostly centering on adequacy of standard model rocket engines ... mostly made moot by the following. --Marc ] ------------------------------ From: vac@sam.cs.cmu.edu (Vincent Cate) Subject: Re: Aim For The Moon - model rocket contest Summary: Pay a little extra and get light cases on your rockets. Keywords: moon model rocket contest Date: 20 Jun 90 22:00:21 GMT I just talked with someone at Vulcan Systems Inc. He told me that their K500 weighs about 3.5 pounds with the fuel being 2.5 pounds of that. He said that the Isp was about 225. I asked if by paying more I could get lighter cases and he said, "Sure if it is large order". He could replace the 16 oz case with a 4.5 oz case. The 4.5 oz case was about $100. A 2.75 lb rocket with a 0.25 lb case would be far better than a 3.5 lb rocket with the same thrust, especially when used as an upper stage. The extra cost would be well worth it. I told him about wanting to send something into space and he said they were building a 60 inch rocket motor for somebody who was sending something into orbit. I was surprised and he said that they made stuff for the military and could make any size. I said, "So I could just order a "Q" and you would make it?" He said, "Sure." With very light cases we should be able to get about a 3,000 MPH delta-V from each stage (using an engine of half the size in each higher stage). Thus a total of 8 stages or so should do it. I AM SURE WE CAN SEND LITTLE ROCKETS INTO SPACE!!!!!!!!!!!!!!!!!!!! -- Vince ------------------------------ From: vac@sam.cs.cmu.edu (Vincent Cate) Subject: Re: Aim For The Moon - model rocket contest Summary: We can not watch them all the way to the moon, we track them. Date: 21 Jun 90 06:09:14 GMT ... >Problem is, why send up only one ounce? How will you know it >got anywhere? The 1 oz payload is a radio transmitter that sends out a burst every now and then (say 1/100th of a second every 100 seconds). The burst can be very high power while the average power usage is very low. Using something like this I think we can get by without having a directional antenna on the rocket and using only a lithium battery (solar cells would be fun too). One thing the contest organizers would have to provide would be a number of large ground dishes. For low altitudes we should be able to get by with a small portable dish. After it has gone up 100 miles we could follow it with one or more of the very large SETI dishes (like 90+ foot diameter). We do, of course, need to talk some SETI people into this but I think that could be done. Anyone interested in helping to organize an "Aim For The Moon" contest? -- Vince ------------------------------ From: Marc.Ringuette@DAISY.LEARNING.CS.CMU.EDU I suggest recruiting Ham Radio guys. They do Earth-Moon-Earth bounces all the time, and may be able to handle this kind of job. Can you transmit on Ham Radio wavelengths from a small package? What are the tradeoffs that would lead us to pick a particular part of the EM spectrum to broadcast in? Size, power, efficiency in receiving, interference from the atmosphere ... Would someone care to give us a short tutorial, or could you refer me to a decent text? ---------------- | Marc Ringuette |------------------------ | mnr@cs.cmu.edu | Cucumber Science Dept. |---------------------------------- | 412-268-3728 | Cranberry Melon Univ. | 'Tis not her coldness, father, | ----------------| Pittsburgh, PA, 15213 | That chills my labouring breast: | ------------------------| It's that confounded cucumber | | I've ate and can't digest. | ---------------------------------- ------------------------------ To: Marc.Ringuette@DAISY.LEARNING.CS.CMU.EDU Cc: space-tech@CS.CMU.EDU, dietz@cs.rochester.edu, cate@CS.CMU.EDU Subject: Re: Aim For The Moon - model rocket contest Date: Thu, 21 Jun 90 16:43:54 -0400 From: dietz@cs.rochester.edu Vince Cate said (in the note from sci.space) that the Isp for Vulkan K500 engines is about 225 seconds. This seems slightly low. Sutton (Rocket Propulsion Elements, 5th ed.) gives the following numbers for an aluminized perchlorate-based solid rocket motor (assumption: shifting equilibrium, nozzle exit pressure 14.7 psia): Chamber pressure (psia) Isp (vacuum) Isp (sea level) 1500 287.4 265.5 1000 280.1 256.0 750 274.6 248.6 500 265.7 237.3 200 242.4 208.4 I wonder if the 225 sec figure the Vulcan salesman gave was *sea-level* Isp. Many of Vince's stages would be burning at higher altitude. One may be able to get even better performance by using larger nozzles on the upper stages, to increase the expansion ratio. Perhaps Vulcan sells special nozzles for exoatmospheric use; if not, one might be able to retrofit a nozzle extension onto their smaller engines (test in a small vacuum tank). It would be interesting to know: (1) the composition of the Vulcan propellant, (2) the chamber pressures of their engines, (3) the expansion ratio of the nozzles. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ From: Tom Neff Date: Thu, 21 Jun 1990 18:52:52 EDT X-Mailer: Mail User's Shell (7.1.1 5/02/90) To: SPACE-TECH Mailing List Subject: Communicating with a 1oz Payload My idea for communicating with a tiny payload near the Moon: outfit it with an omnidirectional laser reflector (like the ones Apollo left) behind an LCD shutter. Then train a laser on it from Earth and read the pulses as the LCD shutter opens and closes. ------------------------------ Date: Thu, 21 Jun 90 21:22:08 -0400 From: dietz@cs.rochester.edu To: space-tech@CS.CMU.EDU Subject: Laser retroreflectors Tom Neff suggested that a 1 oz. payload near the moon could be tracked using a laser retroreflector. No good, I'm afraid. The Apollo laser retroreflector(s?) was an array of corner reflectors perhaps a foot square. It weighed much more than an ounce. Moreover, it requires some fairly heroic measures to use it. The pulsed beam is transmitted through a telescope, and the beam is fairly small when it gets to the moon (since they know where the reflector is, this is ok). Then, an extremely sensitive detector looks for returning photons. I understand they get maybe one return photon per pulse. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: Thu, 21 Jun 1990 19:20-EDT From: Lou Adornato To: space-tech@CS.CMU.EDU Subject: Re: Aim For The Moon - model rocket contest Sender: mnr@DAISY.LEARNING.CS.CMU.EDU Marc.Ringuette writes: >I'd encourage y'all not to worry about the rocket motors for now, but to >concentrate instead on the communications, guidance, and construction of >the rocket Funny you should ask... I've been thinking about the problem of guidance, and I think I have a partial solution. To my (limited) knowledge, there are three elements to a spacecraft guidance system: 1) A reference platform (usu. some kind of gyro assy). 2) Control laws, implemented either in: a) analog hardware, or b) a digital processor and software 3) Effectors consisting of one or more of: a) Engine gimbal and throttle b) Aerodynamic surfaces and controls c) Reaction control systems (positioning jets) d) Inertial control systems (flywheels) All three of these are usually on board to some extent, but it's been pretty common since Apollo to have a lot of the navigation computations done on the ground, and the Orbiter takes regular positioning updates from the ground. The types of effectors used is pretty much dependent on your mission, but for something that's going to go into orbit, I would think that aerosurfaces and an inertial control system would be the absolute minimum. The ICS is going to run into money, but it's probably easier than trying to do the miniature plumbing needed for an RCS. Problems are that it's going to be heavy and consume power, and it produces small angular rates; you're not going to be making any violent maneuvers with it. I'd suggest a laser guided system. By placing one steerable laser transmitter/detector pair a few km to the side of the launch pad, and another a few km uprange, and tying them to a computer, you could develop a pretty accurate state vector. By triangulating the two beams you could get altitude and range, taking the derivative of the position gives velocity. By placing a polarized reflector on the body, you'd be able to measure the roll rate by the spacing between returns, and pitch would come from the attenuation of the side laser, while yaw would come from attenuation of the front laser. Rates could be extrapolated in software. The control laws could be implemented in the ground computer, and the commands to the effectors could be sent by modulating the lasers (although this would complicate the data gathering operation). Of course, this approach would require that the rocket launch directly to orbit, since the lasers would be too far downrange to be used to control the circularizing burn. It might be possible to place a second set of (really powerful) lasers downrange and acquire the rocket by defocusing the beam and painting a large region of sky, and then targeting the refocused beam on the brightest object in the proper frequency. A third set could be installed at the point in the ground track corresponding to the trans-lunar insertion burn. You might even be able to do mid-course corrections, but only at the expense of some on-board processing cabability. By the way, I recently read that the laser reflector from the Apollo 11 ALSEP is still being used to measure the Earth-Moon distance to an accuracy of a few inches, so I'm pretty sure that you'd be able to get fairly accurate data off this system, provided the weather cooperated and the laser fequency was chosen correctly. The military has developed some really sophisticated laser guidance technology, although it works more or less backwards from what I've described (the operator paints the target with the laser, and the missile homes in on the brightest object it sees at the beam frequency). Lou Adornato | Statements herein do not represent the opinions or Cray Research | attitudes of Cray Research, Inc. or its subsidiaries. lfa@cray.com | (...yet) ------------------------------ Date: Thu, 21 Jun 1990 19:27-EDT From: Marc.Ringuette@DAISY.LEARNING.CS.CMU.EDU To: space-tech@CS.CMU.EDU Subject: Re: Aim For The Moon - model rocket contest Good ideas, Lou, but I think a laser guiding system would be too much for us. I've latched onto the idea of using a small gyro, so you can tell your exact orientation, plus some sort of active control. There are two distinct phases of the trip: in-atmosphere, with speed limited by air friction, and out-of-atmosphere acceleration to maximum speed. For the in-atmosphere part, I guess adjustable fins might be the ticket. For the out-of-atmosphere part, how about moving around a counterweight in the nose of the rocket? Assuming that the engine thrust is very precisely oriented along the centerline, it wouldn't take much of a counterweight to do active control of orientation. Here's my scenario: -> 1st stage: accelerate to cruising speed (a few seconds) -> 2nd stage: cruise through atmosphere (a couple of minutes) -> 3rd stage: accelerate outside atmosphere (10-15 seconds?) -> 4th stage: accelerate outside atmosphere (10-15 seconds?) Stages 1 and 2 are fin-stabilized. Then the fins drop off with the 2nd stage, and the remaining stages are counterweight-stabilized. I have only two stages in the final acceleration phase because Vince's phone call indicated that the ratio of fuel mass to casing mass can be about 8 to 1. It then makes sense to have each stage in the acceleration phase be about 8 times smaller than the preceding one, instead of Vince's two-to-one ratio. The relative sizes of the stages might look like this: (1) (2) (3) (4) ==== ==== ======== ======================================-------o ==== ======== ==== I guess you'd want to drop the nosecone and entire aeroshell when you leave the atmosphere. There are still some major reality checks to be done here: 1. How fast do you figure the rocket should cruise through the atmosphere? 800 km/h? 2000 km/h? Presumably it accelerates as the air gets thinner; if you apply constant thrust throughout the atmospheric phase, do you end up going the appropriate speed, or do you speed up too much in the upper atmosphere and heat up? 2. My impression is that for solid rocket motors like these, the length determines how long they burn, and the diameter determines how much thrust they put out. Is that right? 3. I'd like figures like "3 inches per second" and "1 inch diameter = 200N" for the Vulcan rocket motors, so I can sketch out approximate sizes. Hopefully Vince asked for some literature. 4. We need a small, practical, 1-axis gyro, plus some control circuitry. Can we buy a gyro like that? Should be easy to design the circuits. 5. I'm assuming no communications until the coast phase. Will that work? Can we aim the rocket well enough by pointing it in the right direction at the launch, then following the gyro? My goal in aiming is to swing around the moon and head back toward earth if possible. Am I being too optimistic? \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ \\\ Marc Ringuette \\\ Carnegie Mellon University, Comp. Sci. Dept. \\\___ /// mnr@cs.cmu.edu /// Pittsburgh, PA 15213. Phone 412-268-3728(w) /// /////////////////////////////////////////////////////////////////////// ------------------------------ End of Space-tech Digest #65 *******************