So this engine needs air in order to work? Damn, was hoping we'd just solved the problem of fuel weight on spacecraft.
A new mini-reactor revives the dream of a nuclear-powered aircraft.
After more than six decades of research, the first atom-powered airplane is cleared for takeoff. Although details of the project remain classified, a description of this remarkable aircraft has begun to emerge from technical conferences and declassified engineering studies. The plane will be both familiar and unique. Familiar in that it will resemble a Northrop Grumman Global Hawk, the bulbous-nosed unmanned aerial vehicle (UAV) that the U.S. Air Force has used to track enemy movements in Afghanistan and Iraq. Unique because its nuclear reactor is unlike any other. Rather than split heavy elements or fuse light atoms--as in fission and fusion reactors--it will use what is known as a triggered isomer reaction. If this new powerplant, called a quantum nucleonic reactor, performs as scientists expect, its effect on the aircraft industry may prove as revolutionary as the introduction of the jet engine.
To the trained eye, the ungainly Global Hawk is a thing of beauty. A triumph of function over form, its whale-snout nose presents a tiny radar cross section. The thickly shrouded rear-mounted engine, located high in the tail, presents a minimal heat signature. Even the paint, which appears faded, serves a purpose: It helps dissipate heat from the plane's electronic bay. Together, these design features make the Global Hawk virtually invisible as it loiters at 45,000 ft., directing its powerful radar and high-resolution cameras on trouble spots.
One improvement would make the Global Hawk the perfect surveillance platform: eliminating the need to top off its fuel tanks. For UAVs operating deep within hostile airspace, refueling requires dashing hundreds, sometimes thousands, of miles to a friendly landing field. It is chiefly for that reason that the Global Hawk has been selected as a testbed for one of the boldest experiments in aviation history. Project managers for Northrop Grumman and the U.S. Air Force Research Laboratory tell POPULAR MECHANICS they have begun discussions that could lead to the conversion of a Global Hawk to a nuclear-powered aircraft.
If the plan takes shape, a Global Hawk will be pulled off the production line and undergo extensive airframe and powerplant modifications. Chief among these will be the addition of some 2700 pounds of radiation shielding. Installed between the tail section and the main electronics bay, the shielding will create a "hot cell." In this area, which will be designed to minimize leakage of radiation, engineers will install the world's first airborne quantum nucleonic reactor.
Discussions are under way to build a military atomic aircraft, like this PM concept plane based on the Global Hawk UAV. A civilian model would follow a similar design.
Click to Enlarge
A solar cell or engine-mounted generator sends electricity to run a small X-ray machine. The X-rays strike a block of hafnium-178, triggering a drop in the energy levels within the nucleus of the hafnium atoms. This change in energy levels is accompanied by the release of a burst of gamma radiation. The gamma rays heat the core of a heat exchanger. Superheated air from the exchanger floods into the jet engine, performing the same function as the expanding gases created by burning jet fuel. For safety reasons, conventional jet fuel will power the engine when it is below cruising altitude.
The quantum nucleonic reactor neither splits nor fuses atoms. PHOTO BY NORTHROP GRUMMAN
Flying Nukes A jet engine is the essence of mechanical simplicity. Fuel and air are mixed, compressed and ignited. As the gas burns, it moves rapidly rearward, propelling the aircraft forward. Normally, this is done by burning jet fuel, which is exactly what the new nuclear plane will do when it takes off, climbs and lands. When it reaches cruising altitude--in the vicinity of 45,000 ft. and above trans-Atlantic airline traffic--the engine will switch over to running on hot air created by the reactor. Using this power source, an unmanned version could remain on station for months on end. A manned version, the logical next step, could operate as long as the crew had food.
Building a nuclear aircraft poses daunting engineering challenges. The underlying operating principle, however, is straightforward. In a fission reactor, atoms of a very heavy element, such as uranium, are persuaded to split apart, casting off neutrons that split other atoms and produce heat. In a fusion reactor, atoms of a very light element, such as hydrogen, are cajoled to join. Here, too, the conversion of mass into energy obeys the tenets of Einstein's famous E=mc2 equation. The immense heat release keeps the reaction going.
Fusion reactors are in their infancy. But as early as 1940, scientists were thinking about ways of using the heat from nuclear fission to power airplanes. From the late 1950s through the 1980s, the Air Force and the Navy drew up blueprints and got as far as testing components for nuclear craft. At one point, a converted Convair B-36 Peacemaker flew with an operating reactor. However, none of these components were ever connected in the same airplane and a nuclear-powered aircraft never flew. The snag was the shielding needed to protect air crews from radiation--principally neutrons--streaming from the reactor. Planes with enough shielding to protect humans were too heavy to carry weapons. The quantum nucleonic reactor neither splits nor fuses atoms. Rather, it creates its power by triggering a massive release of gamma radiation. This is dangerous to humans, but requires less shielding to control.
Radical Reactor The fuel for the quantum nucleonic reactor is a form--or isomer--of hafnium. Paradoxically, hafnium is the same element used to slow chain reactions in some fission reactors. A nuclear chain reaction occurs when neutrons emitted by a splitting atom strike an adjacent atom, causing it to split as well. Hafnium has a considerable capacity to absorb neutrons without splitting, hence its use as a brake or control rod in fission-type reactors.
In the late 1990s, researchers at the University of Texas in Dallas made a remarkable and unexpected discovery about the hafnium isomer known as hafnium-178. When they bombarded the metal with "soft" X-rays like those your dentist uses to examine your teeth, the metal released a burst of gamma rays 60 times more powerful than the X-rays. While this may seem impossible, it is permitted by the laws of physics. On the subatomic level, bombarding hafnium-178 with X-rays has an effect similar to triggering a small avalanche by tossing a snowball onto a snow-covered roof.
One of the most useful aspects of this newly discovered type of nuclear reaction is that the gamma ray output drops precipitously the moment power to the X-ray machine is turned off, explains Capt. Christopher Hamilton. He conducted research on a hafnium reactor at Wright-Patterson Air Force Base in Ohio, and was the first to propose using that device to power a Global Hawk.
A hafnium-fueled reactor has two other attractive features, Hamilton says. Since it produces only gamma radiation, less shielding is required. And should an accident occur, there is less of an environmental concern than with fission. Hafnium-178 has a half-life of only 31 years compared to thousands of years for other reactor fuels. In addition, unlike uranium or plutonium, hafnium-178 cannot support a chain reaction, which means it cannot be used to make rogue nuclear weapons.
In his report on the potential for the new reactor, Hamilton calculated that a small X-ray machine could be used to generate gamma radiation and create sufficient heat to run a conventional military jet engine. The Los Alamos and Sandia nuclear weapons laboratories in New Mexico have since taken up research for the project, supported by funding from the Department of Energy. Researchers involved with these projects have been instructed to discourage public discussion of the new type of reactor. Los Alamos scientists have expressed suspicion that the triggered isomer reaction process may not release useful amounts of heat. The Department of Defense, on the other hand, has put the reactor on its Militarily Critical Technologies List, which means it is on the fast track for future funding.
Executives for Northrop Grumman tell POPULAR MECHANICS that while they have not yet signed a contract to convert a Global Hawk to nuclear power, they are aware of discussions taking place within the Air Force. Conventional aircraft can take a decade to move from concept to the runway. The civilian atomic airplane has, in one form or another, been under discussion for more than 60 years. With the emergence of a new type of power-plant, that decades-old dream may at long last take wing.
So this engine needs air in order to work? Damn, was hoping we'd just solved the problem of fuel weight on spacecraft.
I was pretty interested in that article when it first came out.
Its an interesting concept and really holds promise for UAVs or UCAVs. The Air Force was planning on sticking a full blown nuclear reactor in a B-36, but that didn't happen.
There are a number of problems with this article. The type of reaction involved produces large amounts of Gamma radiation, which contrary to what the article says, is actually the most difficult to stop since it has very high energy. The aircraft would still need heavy shelding (possibly too much to be practical). Being that it's a UAV, it would not need nearly as much as in a manned aircraft, but you won't be getting manned versions of the Global Hawk any time soon as the pictures in the article seem to indicate.
In addition, I don't the the public (especially the media) would understand the difference between 'normal' fission and this reaction. The first hint of the word nuclear would have everyone flipping out--so I don't think it would be very acceptable to the public.
Like I said, it is a pretty cool concept and could really do a lot to help UAVs or UCAVs.
is this nuclear powered planes a bit un-realistic with all the natural air crashes and with the unnatural air crashes?
I was just about to ask, what happens if one crashes or is downed? Does this other form of fission not emit such harmful radiation? Otherwise, talk about probable collateral damage to civilian lives.
Next faulty idea ....baloons are much better...
according to the article it's kosher. you stop zapping it with x-ray's (ie aircraft hits the the ground) and it stops producing gamma radiation. halfnium on its own isn't that bad, wouldn't want to eat it with your weaties everyday but the risk is managable. wonder how big of a "chunk" of halfnium we're talking about? i suppose that also defines how long the bird can stay up there?
Originally Posted by Tane Angle
A nuclear engine that does not splits nor fuses atoms? Sounds very
revolutionary to me. But for safety reasons I would rather keep the
aircraft unmanned, since the Globalhawk can fly autonomously with no
human assistance(man in the loop factor) and with nuclear engine it
can stay in the air for months.
This is actually not so new, obviously Jim Wilson had problems finding a new topic to write about, so he just reformulated an older article that had appeared on the "New Scientist" in february 2003. But he added some nice pictures.
Nuclear-powered drone aircraft on drawing board
19:00 19 February 03
The US Air Force is examining the feasibility of a nuclear-powered version of an unmanned aircraft. The USAF hopes that such a vehicle will be able to "loiter" in the air for months without refuelling, striking at will when a target comes into its sights.
With a nuclear drive a Global Hawk could fly for months without landing (Image: ***** NEWSERVICE)
But the idea is bound to raise serious concerns about the wisdom of flying radioactive material in a combat aircraft. If shot down, for instance, would an anti-aircraft gunner in effect be detonating a dirty bomb?
It raises political questions, too. Having Unmanned Aerial Vehicles (UAVs) almost constantly flying over a region would amount to a new form of military intimidation, especially if they were armed, says Ian Bellamy, an arms control expert at Lancaster University in Britain.
But right now, there seems no stopping the proliferation of UAVs, fuelled by their runaway success in the Kosovo and Afghanistan conflicts. The big attraction of UAVs is that they do not put pilots' lives at risk, and they are now the norm for many reconnaissance and even attack missions.
The endurance of a future nuclear-powered UAV would offer military planners an option they might find hard to turn down. Last week, the Pentagon allocated $1 billion of its 2004 budget for further development of both armed and unarmed UAVs.
The US Air Force Research Laboratory (AFRL) has funded at least two feasibility studies on nuclear-powered versions of the Northrop-Grumman Global Hawk UAV (pictured). The latest study, revealed earlier in February at an aerospace technology conference in Albuquerque, New Mexico, concluded that a nuclear engine could extend the UAV's flight time from hours to months.
But nuclear-powered planes are not a new idea. In the 1950s, both the US and the USSR tried to develop nuclear propulsion systems for piloted aircraft. The plans were eventually scrapped because it would have cost too much to protect the crew from the on-board nuclear reactor, as well as making the aircraft too heavy.
The AFRL now has other ideas, though. Instead of a conventional fission reactor, it is focusing on a type of power generator called a quantum nucleonic reactor. This obtains energy by using X-rays to encourage particles in the nuclei of radioactive hafnium-178 to jump down several energy levels, liberating energy in the form of gamma rays. A nuclear UAV would generate thrust by using the energy of these gamma rays to produce a jet of heated air.
The military interest was triggered by research published in 1999 by Carl Collins and colleagues at the University of Texas at Dallas. They found that by shining X-rays onto certain types of hafnium they could get it to release 60 times as much energy as they put in (New Scientist print edition, 3 July 1999).
Tightly controlled reaction
The reaction works because a proportion of the hafnium nuclei are "isomers" in which some neutrons and protons sit in higher energy levels than normal. X-ray bombardment makes them release this energy and drop down to a more stable energy level.
So the AFRL has since been looking at ways in which quantum nucleonics could be used for propulsion. "Our directorate is being cautious about it. Right now they want to understand the physics," says Christopher Hamilton at the Wright Patterson Air Force Base in Ohio, who conducted the latest nuclear UAV study.
The AFRL says the quantum nucleonic reactor is considered safer than a fission one because the reaction is very tightly controlled. "It's radioactive, but as soon as you take away the X-ray power source its gamma ray production is reduced dramatically, so it's not as dangerous [as when it's active]," says Hamilton.
Paul Stares, an analyst with the US Institute of Peace in Washington DC, wonders what would happen if a nuclear UAV crashed. But Hamilton insists that although hafnium has a half-life of 31 years, which according to Britain's National Radiological Protection Board is equivalent to the highly radioactive caesium-137, the structural composition of hafnium hinders the release of this radiation.
"It's probably something you would want to stay away from but it's not going to kill you," claims Hamilton.
Actually, there is some debate, wether this "quantum nucleonic reactor" does actually work.
THE ISOMER BOMB: HOW A DENTIST'S X-RAY MACHINE WENT TO WAR.
Well, maybe not quite. A news story in this week's issue of New Scientist magazine reports that the Department of Defense is currently pursuing an isomer bomb, which would supposedly release its energy in the form of gamma rays from the decay of a nuclear isomer of Hf-178. Indeed, such nuclear isomers are on the Militarily Critical Technologies List. The claim is that decay can be accelerated by irradiation with low-energy x-rays. We're told that the scientist who did the research used an x-ray machine borrowed from a dentist friend. A JASON panel determined that the idea is theoretically implausible and the evidence shaky at best. A group that attempted to reproduce the effect in a carefully controlled study at the Advanced Photon Source found nothing.
Or another comment like this
HAFNIUM-178: JUST WHEN YOU THINK LIFE CAN'T GET ANY SILLIER.
The cover of Popular Mechanics for May proclaims the dawn of the age of atomic airplanes powered by miniature nuclear reactors. These are not old-fashioned fission reactors. These are the new "quantum nucleonic reactors," a.k.a. hafnium-178 isomer reactors. The problem with fission reactors was that they required too much shielding. The problem with the hafnium-178 reactor is that it doesn't exist. Carl Collins at U. of Texas, Dallas, claimed to be able to trigger decay of the hafnium-178 nuclear isomer with x-rays. That would be a miracle, but several other groups found it just doesn't happen. That detail was left out of the Popular Mechanics story, which contains nothing beyond the New Scientist story a year ago (WN 15 Aug 03). The hafnium-178 isomer avalanche now seems destined to join hydrinos, zero-point energy, gravity shields, cold fusion and all the other free-energy fantasies that only work for believers. In the paranormal world this is known as "the investigator effect."
So....at least wait with buying shares or something like it, until this is decided.
I saw a program the other week on the History Channel about Nuclear-powered airplanes, was pretty interesting . Nice to see things have come on a little.