gcb1@ukc.UUCP (G.C.Blair) (11/15/85)
I consider myself fairly well up-to-date with the current advances in the so-called "Star Wars" technology & research, but I realised something today which had never occurred to me before: We all know how you can make a parabolic mirror by stretching a thin film of aluminised plastic over a ring of metal or some other such material, then using a vacuum pump to suck the film into the shape of a parabola, but has this actually been achieved in space (ie en vacuo)? Surely the principle demands that the pressure on the front surface is greater than the pressure from the back? So in a vacuum, the pressure would be equal from both sides, even with the vacuum pump, thus the sheet of plastic would not deform into the required shape. Does this then mean that the telescope would require a closed volume of gas in front of the mirror, supplying a pressure, but also re-introducing an absorbing medium for the light? This latter argument is certainly one that I have never heard propounded. Does anyone know of any experiments that have been carried out in a vacuum on this topic? Grant C. Blair [Is anyone out there willing to sponsor me to do Stars Wars research? Please?]
pmk@prometheus.UUCP (Paul M Koloc) (11/17/85)
> I consider myself fairly well up-to-date with the current advances in > the so-called "Star Wars" technology & research, but I realised something > today which had never occurred to me before: > > We all know how you can make a parabolic mirror by stretching a thin > film of aluminised plastic over a ring of metal or some other such > material, then using a vacuum pump to suck the film into the shape of > a parabola, but has this actually been achieved in space (ie en vacuo)? > Surely the principle demands that the pressure on the front surface is > greater than the pressure from the back? So in a vacuum, the pressure > would be equal from both sides, even with the vacuum pump, thus the > sheet of plastic would not deform into the required shape. Does this > then mean that the telescope would require a closed volume of gas in > front of the mirror, supplying a pressure, but also re-introducing > an absorbing medium for the light? This latter argument is certainly > one that I have never heard propounded. Does anyone know of any > experiments that have been carried out in a vacuum on this topic? > > Grant C. Blair > For ground based lasers blasting straight up out of the atmosphere the attenuation is approximately equivalent to the photon attenuation of one mile of air at sea level. This will change drastically once a few dozen thermonuclear hits kick up some glowing dust clouds. In any event a high speed of sound gases such as helium might work and their attenuation would be quite negligible when compared to the ground - space trip. Perhaps a better way would be to use an array of medium voltage small electron guns that would spray electrons like an ink jet printer except that the electrons would "coat" the plastic mirror with a variable density coating of charge. A rigid screen grid could act as an attractive ground. Leakage could be controlled with a very low pressure helium neon gas, for example. The reaction time might be fast enough for such a system. > [Is anyone out there willing to sponsor me to do Stars Wars research? Please?] The congress to date has been too gutless to pass the Senate version of the budget bill. Consequently the government is under a ECR which really screws the lid down on SDI. Also there is a need to "grand stand" with spectacular "demos" to keep the democrats in congress happy that something positive is happening in defensive defense development. That means the "IST" part of the program, (Innovative Science and Technology) which is where the later development of a truly effective program will come from, has taken some pretty debilitating cuts. Jim Ionson heads up IST and has to spend more time responding to twinkies than supporting the research of some really high risk but super high payoff concepts. What's really interesting is that some of this research promises to have a much greater and more positive impact on the later commercial development of space and other useful technologies. Consequently, the best source for Stars Wars research support is Eugene Velikov, (no relation to Velikovsky) of the Academy of Science, Moscow, a head of Kurchatov, and a mastermind of their own advanced Star Wars effort at Krasnaya Pachra and other Russian military labs, (so secure that even scientists from the "Eastern Allies" can not visit them). Incidentally, Velikov has lobbied Senator Pell and others against our new fledgling program and has served on disarmament committees. My own personal information is that the Russian program was in progress at least as far back as 1976. I suspect the Russians have made a monumental discovery and are not willing to share it with us, and if I am correct as to what is is, I don't blame them because in a few more years it will give them a massive military edge. I also think the concept of their program is considerably more aggressive (offensive) than ours. +---------------------------------------------------------+--------+ | Paul M. Koloc, President: (301) 445-1075 | FUSION | | Prometheus II, Ltd.; College Park, MD 20740-0222 | this | | {umcp-cs | seismo}!prometheus!pmk; pmk@prometheus.UUCP | decade | +---------------------------------------------------------+--------+
gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (11/18/85)
> Consequently, the best source for Stars Wars research support is > Eugene Velikov, (no relation to Velikovsky) of the Academy of > Science, Moscow, a head of Kurchatov, and a mastermind of their > own advanced Star Wars effort at Krasnaya Pachra and other Russian > military labs, (so secure that even scientists from the "Eastern > Allies" can not visit them). Incidentally, Velikov has lobbied > Senator Pell and others against our new fledgling program and > has served on disarmament committees. My own personal information > is that the Russian program was in progress at least as far back > as 1976. I suspect the Russians have made a monumental discovery > and are not willing to share it with us, and if I am correct as > to what is is, I don't blame them because in a few more years it > will give them a massive military edge. I also think the concept > of their program is considerably more aggressive (offensive) than > ours. It is, I thought, well known that the Soviets test-fired a neutral particle beam "weapon" several years ago. One assumes that they are farther along by now. If it weren't so dangerous, it would be almost amusing how readily a lot of Americans (apparently including the President himself) jump at the chance to bargain away strategic defense at the negotiating table. The only logic for a strategic defense would preclude failing to deploy it. If you read the memoirs of high-level Soviet defectors (not ballet performers, but those involved in the military, intelligence, or diplomatic service), you will find that it is quite common for the Soviets to encourage nuclear-freeze, unilateral disarmament, and anti- defense movements in the U.S. Often this is not as overt as Velikov lobbying in the Senate. But if you're the least bit suspicious of the Soviet government having our best interests at heart, you might be able to conclude what their perception of the real worth of America's military development is. Of course, your values may not be quite the same as theirs.. This subject should probably move off net.physics, but I don't know where it belongs. Sorry.
tedrick@ernie.BERKELEY.EDU (Tom Tedrick) (11/21/85)
>Consequently, the best source for Stars Wars research support is >Eugene Velikov, (no relation to Velikovsky) of the Academy of >Science, Moscow, a head of Kurchatov, and a mastermind of their >own advanced Star Wars effort at Krasnaya Pachra and other Russian >military labs, (so secure that even scientists from the "Eastern >Allies" can not visit them). Incidentally, Velikov has lobbied >Senator Pell and others against our new fledgling program and >has served on disarmament committees. My own personal information >is that the Russian program was in progress at least as far back >as 1976. I suspect the Russians have made a monumental discovery >and are not willing to share it with us, and if I am correct as >to what is is, I don't blame them because in a few more years it >will give them a massive military edge. I also think the concept >of their program is considerably more aggressive (offensive) than >ours. One thing that has bothered me about the debate on Star Wars research is the idea that one can afford to stop work in some area of weapons research. The classical theory of war includes the application of new weapons and tactics on a massive scale as a fundamental principle. The easiest way to win a war is to develop some new weapon that is unknown to the other side and use it on a massive scale in a lightning surprise attack, thereby destroying the enemy before he has a chance to develop countermeasures. One can never predict for certain that some new weapon cannot be created which will upset the balance of power, therefore as long as we have hostile nations, abandoning research is potentially suicidal. The eternal arms race isn't appealing, but giving up the struggle may lead to destruction.
dls@mtgzz.UUCP (d.l.skran) (11/22/85)
I would love to hear your guess as to what that massive Russian breakthrough might be. Dale
carroll@uiucdcsb.CS.UIUC.EDU (11/23/85)
/* Written 8:47 am Nov 21, 1985 by pmk@prometheus.UUCP in uiucdcsb:net.space * What must be done is to rid the solar system of fission devices; even a commercial reactor could conceivably wipe out the concept of humanity as we know it in a few short centuries. * Could you expain how that works? Even the worst possible fission power accident would be not nearly as bad as a nuclear weapon explosion. If you worried about mutations and the like, you should really read the reports on the Hiroshima and Nagasaki survivors, who have a not even detectablly above the norm mutation rate.
debray@sbcs.UUCP (Saumya Debray) (11/24/85)
> We all know how you can make a parabolic mirror by stretching a thin > film of aluminised plastic over a ring of metal or some other such > material, then using a vacuum pump to suck the film into the shape of > a parabola ... Seems to me that since air pressure is the same in all directions, this would give a spherical rather than a parabolic mirror. -- Saumya Debray SUNY at Stony Brook uucp: {allegra, hocsd, philabs, ogcvax} !sbcs!debray arpa: debray%suny-sb.csnet@csnet-relay.arpa CSNet: debray@sbcs.csnet
cmpbsdb@gitpyr.UUCP (Don Barry) (12/02/85)
In article <26@sbcs.UUCP>, debray@sbcs.UUCP (Saumya Debray) writes: > Seems to me that since air pressure is the same in all directions, this > would give a spherical rather than a parabolic mirror. By the same argument, a suspended string would form a spherical arc - instead, the form is a catenary, described by the hyperbolic functions. I am unaware of the figure of equipressure deformation of an elastic disc, but one technique that is used to generate true parabolas in a uniform gravity field is that of spin-molding. It is an easy matter to calculate the equipotential surface of a spinning liquid, and imposing the condition of stability, the figure is a paraboloid. -- Don Barry (Chemistry Dept) CSnet: cmpbsdb%gitpyr.GTNET@gatech.CSNET Georgia Institute of Technology BITNET: CMPBSDB @ GITVM1 Atlanta, GA 30332 ARPA: cmpbsdb%gitpyr.GTNET%gatech.CSNET@csnet-relay.ARPA UUCP: ...!{akgua,allegra,amd,hplabs,ihnp4,seismo,ut-ngp}!gatech!gitpyr!cmpbsdb
rimey@ernie.BERKELEY.EDU (Ken &) (12/03/85)
>> Seems to me that since air pressure is the same in all directions, this >> would give a spherical rather than a parabolic mirror. >By the same argument, a suspended string would form a spherical arc - >instead, the form is a catenary, described by the hyperbolic functions. > ... >Don Barry (Chemistry Dept) CSnet: cmpbsdb%gitpyr.GTNET@gatech.CSNET No, Saumya is certainly right. Soap bubbles are certainly spherical, even when they sit on circular wire frames. The force on each piece of the surface is equal to the pressure (times the area of the piece) and oriented perpendicular to that piece. If on each piece of a string you put a force (proportional to the length of the piece) perpendicular to that piece of string, the string would form a circle. THAT is the correct analogy. Ken Rimey rimey@dali.berkeley.edu
stuart@rochester.UUCP (12/04/85)
From: Stuart Friedberg <stuart>
References: <384@ukc.UUCP> <26@sbcs.UUCP> <1124@gitpyr.UUCP>, <11128@ucbvax.BERKELEY.EDU>
There seem to be at least two differing interpretations of the
original article. My interpretation is that a disk of film is attached
to a fixed, rigid ring, and then more pressure is applied on one side
than the other. This yields a caternary, not a spherical section. The
critical difference between this and the soap bubble interpretation
(which leads to spherical sections) is that the edge of the disk is
FIXED and can not move.
If you take a soap bubble, draw a circle on its surface and change
the internal pressure, the circle will shrink or grow. Moreover,
every circle you can draw on the surface of the sphere will change by
the same proportion.
If you take the anchored disk and change the pressure on one side,
the rim is FIXED, and circles drawn at different distances from the
rim will change by different proportions.
By referring to the original article, it should be clear what the
proposed situation was. In any case, unless additional forces
(rotations) are placed on the disk, the surface will be neither
spherical, nor parabolic as originally conjectured, but hyperbolic
(a 3-D caternary surface).
Stu Friedberg {seismo, allegra}!rochester!stuart stuart@rochestercmpbsdb@gitpyr.UUCP (Don Barry) (12/04/85)
In article <11128@ucbvax.BERKELEY.EDU>, rimey@ernie.BERKELEY.EDU (Ken &) writes: > No, Saumya is certainly right. Soap bubbles are certainly spherical, > even when they sit on circular wire frames. The force on each piece > of the surface is equal to the pressure (times the area of the piece) > and oriented perpendicular to that piece. An important fact to remember, however, is that a soap bubble has uniform tension at every point. A deformed disk, however, obviously doesn't. My point is that all the variables aren't being looked at, and when they are the figure is probably not going to be anything so nice as a conic section. -- Don Barry (Chemistry Dept) CSnet: cmpbsdb%gitpyr.GTNET@gatech.CSNET Georgia Institute of Technology BITNET: CMPBSDB @ GITVM1 Atlanta, GA 30332 ARPA: cmpbsdb%gitpyr.GTNET%gatech.CSNET@csnet-relay.ARPA UUCP: ...!{akgua,allegra,amd,hplabs,ihnp4,seismo,ut-ngp}!gatech!gitpyr!cmpbsdb
al@ames.UUCP (Al Globus) (12/06/85)
> My own personal information > is that the Russian program was in progress at least as far back > as 1976. I suspect the Russians have made a monumental discovery > and are not willing to share it with us, and if I am correct as > to what is is, I don't blame them because in a few more years it > will give them a massive military edge. I lost count of the number of secret Soviet military programs making monumental distcoveries that would give the Soviet military a massive military edge in a few years that I've heard about in the last 20 years. Maybe its true, but its beginning to sound like crying wolf to me. I also think the concept > of their program is considerably more aggressive (offensive) than > ours. According to Aviation Week and Space Technology last spring the Soviet military budget is approximately 70% for home defense. The U.S. budget for defense of the U.S. is approximately 3% of our military funding. There are good reasons for this. We haven't been invaded since the war of 1812. The Soviets have suffer two major and several smaller invasions this century. We have no hostile boarders. They have thousands of miles of hostile boarders. Let's move to this net.politics.
tan@ihlpg.UUCP (Bill Tanenbaum) (12/06/85)
> > (Saumya Debray) > > Seems to me that since air pressure is the same in all directions, this > > would give a spherical rather than a parabolic mirror. ------------ > [Don Barry] > By the same argument, a suspended string would form a spherical arc - > instead, the form is a catenary, described by the hyperbolic functions. > I am unaware of the figure of equipressure deformation of an elastic disc, > but one technique that is used to generate true parabolas in a uniform gravity > field is that of spin-molding. It is an easy matter to calculate the > equipotential surface of a spinning liquid, and imposing the condition of > stability, the figure is a paraboloid. ----------- Don Barry is confusing two very different cases. The suspended string and spin molding are cases where the force is due to gravity, and thus has a UNIQUE DIRECTION, and is proportional to the mass of the object. In the case of the mirror, the force is ISOTROPIC and independent of the mass of the mirror (assuming the mirror is thin enough so gravity is negligible compared to vacuum pressure). In such a case, Saumya Debray must be right. -- Bill Tanenbaum - AT&T Bell Labs - Naperville IL ihnp4!ihlpg!tan
gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (12/06/85)
> They have thousands of miles of hostile boarders.
Maybe they should put an end to all those ugly roomers.timothym@tekigm2.UUCP (Timothy D Margeson) (12/09/85)
Hi, To add my pennies worth to this discussion: Some years back, in 1967 I believe, I read an article in one of the science rags about a weapon the ruskies had built. It was described as a small, light weight ultra low frequency sound wave generator. It was tested on living some small living creatures, dogs?. The outcome of the tests were several puddles of a jelly-like substance, wiht a few bones showing. I don't remember if the article mentioned range or power requirements, but if they discovered and had tested the item back then, I would suspect they have worked out some of the problems, if not all. Another thing the Russians have been working on, more of a concern to me is the efforts to utilize or tap the power of the human brain (no flames please). If they do develop, or have developed a method of communication, or control via telepathy or other thought processes, what good will any space based weapon system be. It is my opinion that neither the US or USSR will push the first button, that some small insignificant country (or passion group) will detonate a device delivered by hand, in a location prime to cause suspicion between us and the ENEMY (read others like us who really don't care about dieing by radiation poisoning). The resulting escalation will be the downfall of us all, and any weapons, or anti-weapons in space will just make for a faster or prolonged death or US, the humans of planet EARTH, depneding on their nature, be it offensive or defensive. And, with that I'll close with a question. Given one terrorist, and one nuclear device, and one city unnamed...... You don't deal with insanity. -- Tim Margeson (206)253-5240 tektronix!tekigm2!timothym @@ 'Who said that?' PO Box 3500 d/s C1-465 Vancouver, WA. 98665
al@ames.UUCP (Al Globus) (12/20/85)
> > One thing that has bothered me about the debate on Star Wars > research is the idea that one can afford to stop work in > some area of weapons research. The classical theory of war > includes the application of new weapons and tactics on a > massive scale as a fundamental principle. The easiest way > to win a war is to develop some new weapon that is unknown > to the other side and use it on a massive scale in a lightning > surprise attack, thereby destroying the enemy before he has > a chance to develop countermeasures. One can never predict > for certain that some new weapon cannot be created which > will upset the balance of power ... The development of weapon systems that can destroy all of society, of which the present nuclear weapons is only the first, has made this concept and other war making concepts obsolete if we are to survive. The effect of weapons research is to reduce the time it takes to destroy organized society from days in the fifties, to hours now, to seconds for third or fourth generation star wars systems with planet killing capabilities. If we continue to have enemies and fight wars, sooner or later we will be utterly destroyed. We (both sides) must realize that Russia and America are completed dependent on each other and act accordingly; or our fate is sealed.