This is the first in two-part series from exotic weapons guru David Hambling.Theres a simple technology that could transform civil aviation, slashing fuel consumption, reducing greenhouse emissions and cutting noise. The problem is, nobody knows about it yet. It's a military secret. The way technology migrates from classified weapons programs to everyday life is the theme of my book, Weapons Grade. (Did I mention it was out in paperback this week?) We wouldnt have jet aircraft, computers or satellite communications without such programs. But when they stay secret, the public benefit is lost. What would have happened to the electronics industry if the transistor had not been declassified in 1949?Plasma aerodynamics offers tantalizing promises of improving aircraft performance. By producing a thin layer of charged particles around an aircraft you can change the behavior of the boundary layer, significantly reducing friction. The charged layer also absorbs radar, improving stealth.When my colleague Justin Mullins wrote about the subject for New Scientist magazine back in 2000, it seemed to be an obscure Russian technology dating from the late 70s which the US was just beginning to examine. But it offered real benefits, with a potential drag reduction of up to 30%.
A cut in drag of 1 per cent means you can increase an airliner's payload by about 10 per cent, or it could simply fly farther or faster, Mullins pointed out, Just imagine the effect this could have on cash-strapped airlines.The Russians seemed to be years ahead, even marketing a plasma stealth add-on device said to reduce radar returns by a factor of a hundred.He concludes by wondering if the technology can actually work in practice.
Either the new labs are a huge waste of time and money, or the American military knows something we don't.As it turns out, they certainly do.A lot of information on stealth disappeared from the public domain decades ago when the whole subject turned black. Which was why I was surprised to find the original patent for plasma stealth still intact.Patent 3,127,608 is called "Object Camouflage Method And Apparatus," and "relates to a method of making aircraft or other objects invisible to radar." The inventor, one Arnold L. Eldredge, describes the theoretical basis of plasma stealth accurately.The most surprising thing is the date. The patent was filed on August 6th, 1956. The technology has been around for fifty years.But the big problem is with his apparatus Eldredge uses an electron gun, which would be way too big to carry on an aircraft. In fact, thats a problem with this whole plasma idea. Apparatus to generate the millions of volts needed is big, bulky and impractical; even these days the Russians are talking 100 Kg and tens of kilowatts.But there is a way - check out Patent 4,030,098 (1962) Method and means for reducing reflections of electromagnetic waves assigned to the Secretary of the Army and the rather similar Patent 3,713,157 (1964) belonging to North American Aviation, later absorbed by Boeing Energy Absorption by a Radioisotope Produced PlasmaBoth of these use the same basic concept: a coating of radioactive material producing a flux of either Alpha of Beta particles ionize the air, producing the desired layer of plasma. Its a clever solution. Radioactive paint weighs virtually nothing, does not require any power input and can be dirt cheap. One of the suggested emitters is Strontium-90, which is produced in abundance as a waste product by nuclear reactors.Its also quite safe. With a thin protective coating to prevent it from flaking off, the soft radiation (unlike dangerous Gamma radiation) is not a hazard to pilot or maintenance personnel. This type of material is only dangerous if inhaled or ingested.I checked out the idea with some people who know about these things - Martin Streetly, Editor of Jane's Radar & Electronic Warfare Systems and Professor Igor Alexeff, former President of the IEEE Nuclear and Plasma Sciences Society and an authority on plasma technology.Both confirmed that the idea, though exotic, was sound enough in theory. Interestingly, neither had come across the idea before. And both observed one obvious disadvantage from the point of view of stealth. The radiation levels involved 10 Curies per square centimeter would give the plane a visible glow at night, making it a beacon to enemy air defenses.Did this problem mean that the whole idea was shelved - or were radioactive stealth coatings taken further?Well be looking at some surprising answers in part two...-- David Hambling