View 751 Tuesday, November 20, 2012
The reactionless drive appears again.
Propellentless Space Propulsion Research Continues
Aviation Week & Space Technology Nov05, 2012
Chinese academics say they have perfected the EmDrive thruster
Chinese scientists appear to have validated a propellentless space propulsion technology previously branded as impossible. Based on earlier British research, it is averred that the EmDrive concept provides sustained thrust at low cost and weight, but this has yet to be accepted even as a workable theory by the wider propulsion community.
. . .
Shawyer’s EmDrive does not have any exhaust, according to its inventor.
Credit: Roger Shawyer
This appears to be a violation the law of conservation of momentum. However, Shawyer says net thrust occurs because the microwaves have a group velocity (the velocity of a collection of electromagnetic waves) greater in one direction than the other and relativistic effects to modify the Newtonian mechanics. Shawyer compares the EmDrive to a laser gyroscope, which also looks like a closed system but is actually open and works thanks to relativistic effects.
Shawyer’s analysis was challenged after the EmDrive was featured in a science magazine in 2006. John Costella, a researcher in relativistic electrodynamics, described the EmDrive as a fraud and argued that even with relativity there can be no net thrust.
Shawyer built demonstration EmDrives to back his claims, including a 7-lb.
version he said produced a thrust of 85 millinewtons (mN) with a 300-watt input. Skeptics, convinced of its impossibility, have not even tested the EmDrive.
A Chinese research professor, Yang Juan, professor of propulsion theory and engineering of aeronautics and astronautics at the Northwestern Polytechnic University in Xian, claims in a peer reviewed journal to have built a model that produces 720 mN from 2.5 kw of input power.
If that holds up, it is revolutionary. Professor Yang is at this time unable to answer questions about the device, and it is not available for inspection by Aviation Week or anyone else so far as Aviation Week can determine.
The Shawyer Drive was featured on the cover of New Scientist a few years ago. Its principles are available on line. The Wiki story is here.
A working reactionless drive – Yang’s paper is entitled "Net Thrust Measurement of Propellentless Microwave Thruster," and is in the June edition of the journal Acta Physica Sinica published by the Chinese Academy of Sciences – would be an astounding development. It would undoubtedly earn Shawyer a Nobel Prize as well as a great deal of money.
Nothing I have seen describes just how the thrust was measured, or what experimental precautions were taken to be sure that this is not some kind of reaction with the outside world. If it works we should all cheer. It is the key to the solar system, and possibly to the stars.
I have a considerable history of looking for reactionless drives. It began when I was at Boeing in the 1950’s, when Harry Stine saw the Dean Drive in action, and Editor John W. Campbell, Jr. featured it in Analog Science Fiction. The Dean Drive was said to be a system of mechanical counter-rotating systems out of phase with each other; the phase differential “converted rotary acceleration into linear acceleration.” The result was a device which, placed on an ordinary bathroom scale, apparently lost weight. The entire story of my experience with the Dean Drive (which happened in the fifties) is told in a previous View From Chaos Manor and need not be told again.
I have told my story of the Dean Drive for many years, including at least once in my BYTE column back in the glory days, and I have been approached by many with stories of a reactionless drive in the hopes that I will endorse it and help raise money for development of a working model. I have always replied that I have no ability to evaluate theories, but I would be glad to inspect a working model. I have several times been told that a working model is in development, and I should stand by. This got as far as a planned trip to Edinburgh to inspect a device, but as I was arranging some lectures to pay for the trip I was told there was a delay, then another, and then the entire conversation disappeared. Similar things have happened regarding groups in Mississippi, Bogota, and other places. I have even seen photographs of an object hanging off vertical when turned on, but I have never actually seen such a device.
It would be easy enough to use magnetic fields to build a gizmo that looks as if it has a reactionless thrust. All you need it a strong enough magnetic field on the device, and a large enough magnet somewhere behind it. (Obviously I exaggerate when I say ‘easy enough.’ Better perhaps would be ‘not impossible.’) Yang’s device uses a large magnetron. Since I don’t know how the 720 mN thrust was measured, nor anything about the chamber in which it is tested, and apparently neither do the Aviation Week reporters, we can only say, Wow! I hope she’s right!
I understand that Shawyer, having exhausted various grants and fundings, is raising money for continued experimentation. Boeing’s Phantom Works says it is not studying the Shawyer Drive.
I sure hope it works, but I’m not inclined to invest.
I have been a bit under the weather. I am working on the subject of survival in an era of Makers and Takers, with due regard to the dimensions of the question. Do note that on the subject of “Takers” there are a number of questions: as for example, who provides what is taken? It is one thing to hand out a negative income tax as a form of distributism. Milton Friedman was in favor of this method (note that he wasn’t a big advocate of redistribution of wealth, but if you’re going to do it, this would be the method that least influences the economy. It preserves freedom of choice.)
It is worth noting that any organization set up to relieve poverty will be a bureaucracy, and will be subject to the Iron Law of Bureaucracy. Fannie Mae and Freddie Mac and the FHA come to mind, among others.
Anyway, I am a bit delayed on the work.
Another example, as a clarification: suppose we concede an entitlement to education. That can be provided by a state bureaucracy, or in out case, 50 state bureaucracies overlaid with the federal Department of Education. You can have the government determine who is allowed to teach and set qualifications, and establish departments of education. You can give the state a monopoly on accreditation and credentials. Nearly all of his is paid for through taxes, and run by unions and bureaucracies.
Alternatively, you can give every person entitled to education a voucher, and say “Here’s your money. Go get your education. Good luck.” This is how some of the original GI Bill benefits worked. The Korean Veteran’s Bill was even more so.
Or of course you can combine those approaches.
The bureaucratic approach worked back when there was general agreement on what ought to be taught, and schools pretty well offered the national saga and encouraged patriotism. That system brome down in the latter half of the Twentieth Century, and produced a number of bureaucratic schools perpetuating ideologies sometimes antithetical to the beliefs of those paying the bills. For some reason this is considered proper: to require ideological compliance in order to get a teaching credential, but to insist that the ideology one must comply comply with is one rejected by a majority of the population. Over time, of course, that ideology will become the majority view. Or perhaps not: there are those who argue that some ideologies so distort reality that they are doomed to fail, but they may last long enough to end the civilization that created them.
Enough: I wasn’t intending to write an essay on the subject, just to give an example of different ways to provide entitled people with what they are entitled to. The way preferred by bureaucracies is the creation of a bureaucracy. An alternative is simple distributism, giving out largesse to and adjusting inequalities, but not interfering with freedom – other than of course the confiscation of wealth that allows the redistribution in the first place.
© 2012, jerrypournelle. All rights reserved.