Subject: Space-tech Digest #66 Contents: Paul Dietz Re: Laser retroreflectors Henry Spencer Re: Laser retroreflectors Tom Neff Re: Laser retroreflectors Paul Dietz Re: Laser retroreflectors Henry Spencer Re: Laser retroreflectors John Roberts Re: Laser retroreflectors Bob Munck Re: Laser retroreflectors Vince Cate Vulcan rocket motors John Sahr sounding rocket info Kevin Ryan Sprint missile guidance John Roberts Re: Sprint missile guidance John Stevens-Schlick Boeing inertial guidance system John Stevens-Schlick Insurance co. for prizes / OCST paperwork Vince Cate Re: Insurance co. for prizes / OCST paperwork Lou Adornato Re: Aim For The Moon - model rocket contest Jon Leech Re: Aim For The Moon - model rocket contest Marc Ringuette Re: Aim For The Moon - model rocket contest ------------------------------------------------------------ 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 ------------------------------ From: henry@zoo.toronto.edu Date: Thu, 21 Jun 90 23:24:42 EDT To: space-tech@CS.CMU.EDU Subject: Re: 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. Unfortunately, using the Apollo retroreflectors -- a couple of feet square, ultra-high-quality optics -- and the best current ground equipment, you get back only the barest dribble of photons, to the point where Earth-Moon distance measurements take hours of work by specialists. Practical laser communication requires a laser on each end. Also, although retroreflectors are not too sensitive to direction, they are not "omnidirectional" -- their field of view is finite, and their efficiency falls off as you get farther off the optical axis. The Apollo crews took some care to get theirs pointed at the Earth as accurately as possible. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu uunet!attcan!utzoo!henry ------------------------------ From: Tom Neff Date: Fri, 22 Jun 1990 07:01:00 EDT X-Mailer: Mail User's Shell (7.1.1 5/02/90) To: SPACE-TECH Mailing List Subject: Re: Laser retroreflectors On Jun 21, 9:22pm, Paul Dietz wrote: > 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. I would just point out that in 1969, the following were unheard of: huge "lightbucket" backyard Dobsonian amateur scopes, cheap CCD's for same, sophisticated PC tracking software running on the kitchen table. I'm not saying Paul's not right, but I hope someone makes sure it wouldn't work with TODAY'S technology. ------------------------------ To: Tom Neff Cc: SPACE-TECH Mailing List , dietz@cs.rochester.edu Subject: Re: Laser retroreflectors Date: Fri, 22 Jun 90 10:37:11 -0400 From: dietz@cs.rochester.edu > I would just point out that in 1969, the following were unheard of: > huge "lightbucket" backyard Dobsonian amateur scopes, cheap CCD's for > same, sophisticated PC tracking software running on the kitchen table. > I'm not saying Paul's not right, but I hope someone makes sure it > wouldn't work with TODAY'S technology. CCD's won't help. Remember, we're doing *ranging* here. Laser retroreflection won't work at all unless you already have a very good idea of where the target is in the sky, since the outgoing beam is very narrow (it's only a few miles across at the moon). To do ranging, you need a sensor with rapid response. CCDs are integrating imaging detectors. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ From: henry@zoo.toronto.edu Date: Fri, 22 Jun 90 12:28:23 EDT To: space-tech@CS.CMU.EDU Subject: Re: Laser retroreflectors > I would just point out that in 1969, the following were unheard of: > huge "lightbucket" backyard Dobsonian amateur scopes, cheap CCD's for > same, sophisticated PC tracking software running on the kitchen table. > I'm not saying Paul's not right, but I hope someone makes sure it > wouldn't work with TODAY'S technology. The retroreflectors are still in use, and the astronomers working with them would happily sacrifice goats (or graduate students) if it would get them more photons. They've been using big scopes -- professional ones -- from the start, and you can bet they've got fairly modern detectors too. We're talking about marginal results using the best professional equipment run by experts. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu uunet!attcan!utzoo!henry ------------------------------ Date: Fri, 22 Jun 90 18:40:43 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: Corner reflector > ... Then, an extremely sensitive detector looks >for returning photons. I understand they get maybe one return >photon per pulse. It seems to me that there are fundamental problems with communication by light at great distances. There is a lot of "background noise" at optical wavelengths, and the detectors are not too good. Perhaps one could say that light has too much energy per photon, so a tremendous amount of transmission energy is required to assure reception of a reasonable number of photons, as compared to radio wavelengths. While you might use lasers at both ends for communication between a fairly low earth orbit and the moon, it's hard to picture a scenario in which lasers are useful for interplanetary communications. How about this: the tiny spacecraft brings along a gram (or less) of antimatter. At a prearranged time, this is allowed to react with normal matter. That ought to produce a detectable signal! :-) :-) John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Fri, 22 Jun 90 09:44:34 EDT From: munck@Stars.Reston.Unisys.COM To: space-tech@CS.CMU.EDU Subject: Re: Laser retroreflectors Now, if you had a BIG laser available, say from the SDI going-out-of-business sale, you could use it to transmit to, receive from, power, and push the probe. Just give it some very light wings (gossamer, of course; this IS a trip to the moon) that it can move and deform. Normal travel mode would be a dish shape that focuses some incoming laser light on a solar cell that recharges the battery and also detects modulation carrying messages. The beam would also be accelerating the probe. Other configurations of the wings could change course (Humm. Does reflecting the light to the left push the probe to the right? I seem to recall that that doesn't work for the solar wind, because it sticks to the surface rather than bouncing.) or direct the beam back to earth with vibrations to modulate it. Of course, when the laser isn't available, it could use sunlight to tool around the Solar System on its own, maybe even flashing messages back to Earth (or pumping a little laser to do so). Bob Munck, Unisys STARS ------------------------------ Date: Fri, 22 Jun 1990 00:46-EDT From: Vincent.Cate@SAM.CS.CMU.EDU To: space-tech@CS.CMU.EDU Subject: Vulcan rocket motors Marc.Ringuette > ... > 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. All I have from Vulcan is one page and it does not have the numbers you ask for, but I can estimate them. The reason I can only estimate is that I do not know case thickness or how much of the length of the case is really propellant. It seems they can make a wide range of burn rates. That said, for now use: Thrust 160 newt/in^2 Burn rate 4 in/sec They go as low as 2 in/s and as high as 10 in/s. In my Van Nostrands they list a bunch of solid fuels all around 1/2 inch per second with Isps of about 260. As Paul points out the 225 Isp is kind of low. I am sure that it is for sea level use. However, I also think that small rockets are not as efficient as larger ones. The "K" with the Isp of 225 is still not all that large (22 inches long and 2 1/16 inch diameter). I will give Mark a copy of the info I have from Vulcan. I should be getting info from a couple other places soon. Paul: >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. I am sorry to say I can not answer any of these. My guess is that they are using something with Ammonium Perchlorate because another model rocket company uses this and many of the propellants in my Van Nostrand use AP. The info I have from Vulcan gives is total impulse, outside dimensions, initial thrust, average thrust, maximum thrust, burn time, and price. -- Vince ------------------------------ Date: Fri, 22 Jun 90 01:21:52 EDT From: John Sahr To: space-tech@CS.CMU.EDU Subject: sounding rocket info I have a specification document for a couple of NASA sounding rockets which contain some information that may be of use in guiding design. These two rockets had ~1000 pound payloads destined for the E region, apogees of 124 and 170 km. I'll concentrate on the higher altitude rocket: a Black Brant (VC) engine burns for 32.4 sec. The 4 fins were canted 29.2 minutes (0.0084 rad); The rocket body diameter was 17.26 inches (21.92cm radius); with no slip the rocket moves forward 81.6 meters per revolution. However, there is plenty of slip, as the max spin rate is 4 rev/sec, while the max velocity is Mach 5.6 when the engine burns out at 25.1 km. (These rockets are launched nearly vertically, by the way.) These were very heavy rockets, so the max acceleration was only about 5g, while higher altitude sounding rockets get up to 20 g, as I recall. These rockets are despun down to 0.5 Hz with a variety of tricks: they start deploying booms and shedding doors and panels above 70 km, losing the nose cone at 70 km, and separating the motor a few km after that. As I understand it, NASA relies on some very simple gear for the rocket operation: they use glorified _mechanical_ egg-timers for sequencing of events, like shedding the nose cone. These timers are started at launch by bungie cords that yank pins out of the side of the rocket. Also, in order to "tune" the rocket for the altitude, NASA attaches ballast to the rockets. The low altitude rocket had several hundred pounds of lead on board, as I recall. ps: how do you spell "bungie" ? John Sahr, | Electrical Engineering - Space Plasma Physics johns@alfven.spp.cornell.edu | Cornell University, Ithaca, NY 14853 ------------------------------ Date: Fri, 22 Jun 90 10:26 EDT From: KEVIN@A.CFR.CMU.EDU Subject: Rockets to the moon... To: space-tech@CS.CMU.EDU X-Envelope-to: space-tech@CS.CMU.EDU X-VMS-To: IPROUTE"space-tech@cs.cmu.edu",KEVIN In terms of guidance, I thought I might mention the system used on the old Sprint missiles. These were solid fuel rockets intented for short range defense against nuclear attack. They had an acceleration of 100G's and about a 20km range, and were the inner layer behind the Spartan missiles. Steering was provided by injecting freon into the exhaust through small ports in the sides of the nozzle. (Sprint was a two stage missile, one engine per stage.) The expanding freon produced a shock wave deflecting the exhaust in the opposite direction. This seems like a nice lightweight system. Minimal plumbing would be required, except for the vents in the nozzle. Given small valves a pressure-fed tank would work just fine. No motors, no levers, just some small electric valves. Of course, since freon is an evil thing these days, something else might have to be used, but I'm certain there are suitable materials. Comments? kwr ------------------------------ Internet: kr0u@andrew.cmu.edu Date: Fri, 22 Jun 90 18:54:54 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: Sprint >Of course, since freon is an evil thing these >days, something else might have to be used, but I'm certain there are >suitable materials. Don't worry - the only significant hazard from the freon is the eventual release of chlorine. Since the solid rocket booster will presumably be billowing out huge clouds of chlorine compounds, the freon will cause no noticeable additional trouble. :-) John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Fri, 22 Jun 90 10:57 PDT From: Games Wizard Subject: Rocket to the moon. To: space-tech@CS.CMU.EDU I have a friend at BOEING in black box areas that was telling me about a new inertial position detecting system that uses no moving parts, and is the size of a matchbox. I expect that the real workings are VERY secret, and would be enormousllllly expensive. But knowing that something CAN be done is half the battle. BTW has anybodt contacted NAR to see if they are willing to get involved with this project? John. ------------------------------ Date: Fri, 22 Jun 90 11:12 PDT From: Games Wizard Subject: rockets to the moon To: space-tech@CS.CMU.EDU In other news... There has been some talk in the usenet of using insurance policies to fund space research, etc... Some lotteries are funded this way. The philosophy is that you buy an insurance policy stating that something will NOT happen, and when it does the insurance co pays off. You offer the payoff ammount as a prize. The rocket to the moon contest might be a good trial run. I am planning on calling Loyyds of London later today to get info on what it will cost me to offer a prize for the first MODEL rocket class rocket usine a solid propellant motor in the year 1992 (columbus aniversary...) to come within 10,000 miles of the lunar surface. It would be nice to offer $50,000 or $100,000, but I need to find out what it will cost. At the very least it is an interesting concept. John. p.s. For those that get real interested in this project, there is OCST paperwork. I for one have ordered a set so I know what is involved. If you want one, the DOT OCST number is 202 366 - 2929 ------------------------------ Date: Fri, 22 Jun 1990 17:49-EDT From: Vincent.Cate@SAM.CS.CMU.EDU To: space-tech@CS.CMU.EDU Subject: Re: rockets to the moon John: >I have a friend at BEOING in black box areas that was telling me about >a new inertial position system that uses no moving parts, and is the size >of a matchbox. This sounds fantastic!!! Also thanks for the OCST number. I called them and they will send me the stuff. It will be interesting to see how intimidating it is. John. >[...] using insurance policies to fund space research, [...] >[...] >It would be nice to offer $50,000 or $100,000, but I need to find out >what it will cost. At the very least it is an interesting concept. If the prize is winable then the insurance company is going to charge you more than the amount of the prize. Why have them involved at all? For the prize money I do not see the usefulness of an insurance company. For liability insurance the contest would need to deal with some large insurance company. While the odds of hitting a satellite are very small, it would be a very good idea to have insurance coverage. Since the odds are small the insurance cost will be small compared to the cost of a satellite (still a hefty chunk of change I am sure). We would also need liability insurance in case the rocket went wild and did damage on the ground. Such insurance should make people with satellites and government agencies much happier. -- Vince ------------------------------ Date: Fri, 22 Jun 90 16:45:45 CDT From: Lou Adornato To: space-tech@CS.CMU.EDU Subject: Re: Aim For The Moon - model rocket contest Marc.Ringuette@daisy.learning.cs.cmu.edu writes: >Good ideas, Lou, but I think a laser guiding system would be too much for us. The big advantage of the system I proposed is that it greatly reduces the mass and expense of onboard systems. The whole race has to pay for ONE guidance system, and the onboard (and expendable) equipment for each rocket is limited to enough logic to decode incomming command sequences and the actuator systems >I've latched onto the idea of using a small gyro, so you can tell your exact >orientation, plus some sort of active control. I can't give you an exact number (without going to jail), but the gyro assemblies I've seen in military hardware are awfully bulky for a model rocket, and that only has to be accurate enough to cover battlefield distances. As I mentioned, the shuttle takes regular state vector updates from the ground. If NASA can't find an accurate enough gyro system for LEO, given the mass, volume, and cost allowances of the shuttle (positively liberal in comparison to what we're talking about), then it's time to look at alternatives. BTW, the _best_ we could do would be a ring laser gyro. These buggers use some kind of doppler shift algorithm measured over a ludicusly long internal path (somehow the laser travels several miles inside a package the size of a pacemaker) to provide pretty awesome accuracies. A few years back the Honeywell corporate jet flew from Minneapolis to Buenos Aires and back with a cumulative RLG error measured in inches. And that was one of the early models. Unfortunately RLGs are expensive, and I think they use a lot of power. >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. The biggest problem with this is that it will only work while the engines are running, and you're going to need to do a pretty precise allignment _before_ initiating the TLI burn. Also, this arrangement gives no control of roll attitude, and with any attitude control system locked to the vehicle this will make any kind of accurate allignment impossible. On the other hand, it would be fairly easy to test - just prop it up on the end of a broom and see if it can keep the broom standing. > 1. How fast do you figure the rocket should cruise through the atmosphere? I would reccomend a vertical launch to try to get exoatmospheric as soon as possible, then a turn to horizontal and a monster of a burn to get to orbital speed before you fall back. This is ridiculously wasteful of delta-v but I'd guss you'd make it back in the mass of the structural support needed to go supersonic. KEVIN@a.cfr.cmu.edu writes: > In terms of guidance, I thought I might mention the system used on >the old Sprint missiles. > [stuff deleted] >Steering was provided by injecting freon into the >exhaust through small ports in the sides of the nozzle. Again, this requires that the engines are actively burning. This isn't a problem for an interceptor (they never go ballistic), but it won't be possible to maintain constant thrust from launch to TLI burn (the timing requirements of the launch would be outrageous). >Given small valves a >pressure-fed tank would work just fine. This brings up a question I've been dying to ask -- just how do you move liquids in microgravity? A pressure fed tank won't work because the vapor is as likely to be at the bottom of the container as the top. I'd think that a gas bubble in an oxidizer or fuel line would be considered a Bad Thing (if you think detonation is bad in your car engine...) The only thing I can think of is that there's a flexible barrier between the pressure agent and the liquid, so that the whole thing acts like a piston. Thanks. 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: Sat, 23 Jun 90 12:55:26 -0400 From: Jonathan Leech Message-Id: <9006231655.AA05872@rudolph.cs.unc.edu> To: space-tech@CS.CMU.EDU Subject: Re: Aim For The Moon - model rocket contest > This brings up a question I've been dying to ask -- just how do you move > liquids in microgravity? ... The only > thing I can think of is that there's a flexible barrier between the pressure > agent and the liquid, so that the whole thing acts like a piston. Correct, at least for Voyager. The attitude thruster tanks are pressurized with a flexible membrane between the gas and the propellant. Jon (leech@cs.unc.edu) ------------------------------ Date: Fri, 22 Jun 1990 18:31-EDT From: Marc.Ringuette@DAISY.LEARNING.CS.CMU.EDU To: space-tech@cs.cmu.edu Subject: Re: Aim For The Moon - model rocket contest Lou Adornato writes: > Again, this requires that the engines are actively burning. This isn't a > problem for an interceptor (they never go ballistic), but ... But I think our rocket actually IS an interceptor. Much like the EM launchers we discussed last year, we don't want to go into any sort of low Earth orbit; I think we want to have a continuous burn into an almost straight trajectory heading towards where the moon will be, say, two days after launch. Vince has almost convinced me that spinning the rocket is good enough to maintain direction. He tells me that the Scout rockets use spin to maintain direction (I think he said "in the last two stages"), and I halfway believe that misalignment of the engines is mostly cancelled out by the spin. But I won't quite be comfortable about it until one of us does the math... It is pleasingly simple, though: a tube full of fuel with a radio on the nose. 8 feet long, 2 inches in diameter, with a pointed nose and no markings at all. You put it on a stick, aim it about 30 degrees ahead of the moon, spin it at 300 rpm, and light it up. --Marc ------------------------------ End of Space-tech Digest #66 *******************