From another list.
Udhay
Umm. Wow. Self-contained, non-Newtonian (or
semi-Newtonian?) force. If this is confirmed and
analyzed it will be very interesting.
If true, it's a matter of physics and material
research to optimize, pretty straightforward it seems.
It seems that with a microwave oven, welder,
some metal, and a scale you could duplicate the prototype.
Magnetrons produce photons? Microwave energy is photon based? Reporter error?
http://www.newscientisttech.com/article/mg19125681.400;jsessionid=NMGHKBGMCGMM
* 08 September 2006
* Exclusive from New Scientist Print Edition. Subscribe and get 4 free issues
* Justin Mullins
Web Links
* Shawyer's theory paper (pdf)
http://www.newscientist.com/data/images/ns/av/shawyertheory.pdf
The electromagnetic drive
Enlarge image
The electromagnetic drive
Look, no wings!
Enlarge image
Look, no wings!
The trip from London to Havant on the south
coast of England is like travelling through
time. I sit in an air-conditioned train, on
tracks first laid 150 years ago, passing roads
that were known to the Romans. At one point, I
pick out a canal boat, queues of cars and the
trail from a high-flying jet - the evolution of
mechanised travel in a single glance.
But evolution has a habit of springing
surprises. Waiting at my destination is a man
who would put an end to mechanised travel. Roger
Shawyer has developed an engine with no moving
parts that he believes can replace rockets and
make trains, planes and automobiles obsolete.
"The end of wings and wheels" is how he puts it.
It's a bold claim. Read Shawyers theory paper here (pdf format).
Of course, any crackpot can rough out plans for
a warp drive. What they never show you is
evidence that it works. Shawyer is different. He
has built a working prototype to test his ideas,
and as a respected spacecraft engineer he has
persuaded the British government to fund his
work. Now organisations from other parts of the
world, including the US air force and the
Chinese government, are beating a path to his tiny company.
The device that has sparked their interest is an
engine that generates thrust purely from
electromagnetic radiation - microwaves to be
precise - by exploiting the strange properties
of relativity. It has no moving parts, and
releases no exhaust or noxious emissions.
Potentially, it could pack the punch of a rocket
in a box the size of a suitcase. It could one
day replace the engines on almost any
spacecraft. More advanced versions might allow
cars to lift from the ground and hover. It could
even lead to aircraft that will not need wings
at all. I can't help thinking that it sounds too good to be true.
When I meet Shawyer, he turns out to be
reassuringly normal. His credentials are
certainly impressive. He worked his way up
through the aerospace industry, designing and
building navigation and communications equipment
for military and commercial satellites, before
becoming a senior aerospace engineer at Matra
Marconi Space (later part of EADS Astrium) in
Portsmouth, near where he now lives. He was also
a consultant to the Galileo project, Europe's
satellite navigation system, which engineers are
now testing in orbit and for which he negotiated
the use of the radio frequencies it needed.
Dangerous idea
With that pedigree, you'd imagine Shawyer would
be someone the space industry would have
listened to. Far from it. While at Astrium,
Shawyer proposed that the company develop his
idea. "I was told in no uncertain terms to drop
it," he says. "This came from the very top."
What Shawyer had in mind was a replacement for
the small thrusters conventional satellites use
to stay in orbit. The fuel they need makes up
about half their launch weight, and also limits
a satellite's life: once it runs out, the
vehicle drifts out of position and must be
replaced. Shawyer's engine, by contrast, would
be propelled by microwaves generated from solar
energy. The photovoltaic cells would eliminate
the fuel, and with the launch weight halved,
satellite manufacturers could send up two craft
for the price of one, so you would only need half as many launches.
So why the problem? Shawyer argues that for
companies investing billions in rockets and
launch sites, a new technology that leads to
fewer launches and longer-lasting satellites has
little commercial appeal. By the same token, a
company that offers more for less usually wins
in the end, so Shawyer's idea may have been seen
as too speculative. Whatever the reason, in 2000, he resigned to go it alone.
Surprisingly, Shawyer's disruptive technology
rests on an idea that goes back more than a
century. In 1871 the physicist James Clerk
Maxwell worked out that light should exert a
force on any surface it hits, like the wind on a
sail. This so-called radiation pressure is
extremely weak, though. Last year, a group
called The Planetary Society attempted to launch
a solar sail called Cosmos 1 into orbit. The
sail had a surface area of about 600 square
metres. Despite this large area, about the size
of two tennis courts, its developers calculated
that sunlight striking it would produce a force
of 3 millinewtons, barely enough to lift a
feather on the surface of the Earth. Still, it
would be enough to accelerate a craft in the
weightlessness of space, though unfortunately
the sail was lost after launch. NASA is also
interested in solar sails, but has never
launched one. Perhaps that shouldn't be a
surprise, as a few millinewtons isn't enough for serious work in space.
But what if you could amplify the effect? That's
exactly the idea that Shawyer stumbled on in the
1970s while working for a British military
technology company called Sperry Gyroscope.
Shawyer's expertise is in microwaves, and when
he was asked to come up with a gyroscopic device
for a guidance system he instead came up with
the idea for an electromagnetic engine. He even
unearthed a 1950s paper by Alex Cullen, an
electrical engineer at University College
London, describing how electromagnetic energy
might create a force. "It came to nothing at the
time, but the idea stuck in my head," he says.
In his workshop, Shawyer explains how this led
him to a way of producing thrust. For years he
has explored ways to confine microwaves inside
waveguides, hollow tubes that trap radiation and
direct it along their length. Take a standard
copper waveguide and close off both ends. Now
create microwaves using a magnetron, a device
found in every microwave oven. If you inject
these microwaves into the cavity, the microwaves
will bounce from one end of the cavity to the
other. According to the principles outlined by
Maxwell, this will produce a tiny force on the
end walls. Now carefully match the size of the
cavity to the wavelength of the microwaves and
you create a chamber in which the microwaves
resonate, allowing it to store large amounts of energy.
What's crucial here is the Q-value of the cavity
- a measure of how well a vibrating system
prevents its energy dissipating into heat, or
how slowly the oscillations are damped down. For
example, a pendulum swinging in air would have a
high Q, while a pendulum immersed in oil would
have a low one. If microwaves leak out of the
cavity, the Q will be low. A cavity with a high
Q-value can store large amounts of microwave
energy with few losses, and this means the
radiation will exert relatively large forces on
the ends of the cavity. You might think the
forces on the end walls will cancel each other
out, but Shawyer worked out that with a suitably
shaped resonant cavity, wider at one end than
the other, the radiation pressure exerted by the
microwaves at the wide end would be higher than at the narrow one.
Key is the fact that the diameter of a tubular
cavity alters the path - and hence the effective
velocity - of the microwaves travelling through
it. Microwaves moving along a relatively wide
tube follow a more or less uninterrupted path
from end to end, while microwaves in a narrow
tube move along it by reflecting off the walls.
The narrower the tube gets, the more the
microwaves get reflected and the slower their
effective velocity along the tube becomes.
Shawyer calculates the microwaves striking the
end wall at the narrow end of his cavity will
transfer less momentum to the cavity than those
striking the wider end (see Diagram). The result
is a net force that pushes the cavity in one
direction. And that's it, Shawyer says.
Hang on a minute, though. If the cavity is to
move, it must be pushed by something. A rocket
engine, for example, is propelled by hot exhaust
gases pushing on the rear of the rocket. How can
photons confined inside a cavity make the cavity
move? This is where relativity and the strange
nature of light come in. Since the microwave
photons in the waveguide are travelling close to
the speed of light, any attempt to resolve the
forces they generate must take account of
Einstein's special theory of relativity. This
says that the microwaves move in their own frame
of reference. In other words they move
independently of the cavity - as if they are
outside it. As a result, the microwaves themselves exert a push on the cavity.
"How can photons confined inside a cavity make
the cavity move? This is where relativity and
the strange nature of light come in"
Each photon that a magnetron fires into the
cavity creates an equal and opposite reaction -
like the recoil force on a gun as it fires a
bullet. With Shawyer's design, however, this
force is minuscule compared with the forces
generated in the resonant cavity, because the
photons reflect back and forth up to 50,000
times. With each reflection, a reaction occurs
between the cavity and the photon, each
operating in its own frame of reference. This
generates a tiny force, which for a powerful
microwave beam confined in the cavity adds up to
produce a perceptible thrust on the cavity itself.
Shawyer's calculations have not convinced
everyone. Depending on who you talk to Shawyer
is either a genius or a purveyor of snake oil.
David Jefferies, a microwave engineer at the
University of Surrey in the UK, is adamant that
there is an error in Shawyer's thinking. "It's a
load of bloody rubbish," he says. At the other
end of the scale is Stepan Lucyszyn, a microwave
engineer at Imperial College London. "I think
it's outstanding science," he says. Marc Millis,
the engineer behind NASA's programme to assess
revolutionary propulsion technology accepts that
the net forces inside the cavity will be
unequal, but as for the thrust it generates, he
wants to see the hard evidence before making a judgement.
Thrust from a box
Shawyer's electromagnetic drive - emdrive for
short - consists in essence of a microwave
generator attached to what looks like a large
copper cake tin. It needs a power supply for the
magnetron, but there are no moving parts and no
fuel - just a cord to plug it into the mains.
Various pipes add complexity, but they are just
there to keep the chamber cool. And the device
seems to work: by mounting it on a sensitive
balance, he has shown that it generates about 16
millinewtons of thrust, using 1 kilowatt of
electrical power. Shawyer calculated that his
first prototype had a Q of 5900. With his second
thruster, he managed to raise the Q to 50,000
allowing it to generate a force of about 300
millinewtons - 100 times what Cosmos 1 could
achieve. It's not enough for Earth-based use,
but it's revolutionary for spacecraft.
One of the conditions of Shawyer's £250,000
funding from the UK's Department of Trade and
Industry is that his research be independently
reviewed, and he has been meticulous in
cataloguing his work and in measuring the forces
involved. "It's not easy because the forces are
tiny compared to the weight of the equipment," he says.
Optimising the cavity is crucial, and it's as
much art as science. Energy leaks out in all
kinds of ways: microwaves heat the cavity, for
example, changing its electrical characteristics
so that it no longer resonates. At very high
powers, microwaves can rip electrons out of the
metal, causing sparks and a dramatic loss of
power. "It can be a very fine balancing act," says Shawyer.
To review the project, the UK government hired
John Spiller, an independent space engineer. He
was impressed. He says the thruster's design is
practical and could be adapted fairly easily to
operate in space. He points out, though, that
the drive needs to be developed further and
tested by an independent group with its own
equipment. "It certainly needs to be flown experimentally," he says.
Armed with his prototypes, the test measurements
and Spiller's review, Shawyer is now presenting
his design to the space industry. The reaction
in China and the US has been markedly more
enthusiastic than that in Europe. "The European
Space Agency knows about it but has not shown
any interest," he says. The US air force has
already paid him a visit, and a Chinese company
has attempted to buy the intellectual property
associated with the thruster. This month, he
will be travelling to both countries to visit
interested parties, including NASA.
"A Chinese company has tried to buy rights to the microwave thruster"
To space and beyond
His plan is to license the technology to a major
player in the space industry who can adapt the
design and send up a test satellite to prove
that it works. If all goes to plan, Shawyer
believes he could see the engine tested in space
within two years. He estimates that his thruster
could save the space industry $15 billion over
the next 10 years. Spiller is more cautious.
While the engine could certainly reduce the
launch weight of a satellite, he doubts it will
significantly increase its lifetime since other
parts will still wear out. The space industry
might not need to worry after all.
Meanwhile Shawyer is looking ahead to the next
stage of his project. He wants to make the
thrusters so powerful that they could make
combustion engines obsolete, and that means
addressing the big problem with conventional
microwave cavities - the amount of energy they
leak. The biggest losses come from currents
induced in the metal walls by the microwaves,
which generate heat when they encounter
electrical resistance. This uses up energy
stored in the cavity, reduces the Q, and the
thrust generated by the engine drops.
Fortunately particle accelerators use microwave
cavities too, so physicists have done a lot of
work on reducing Q losses inside them. The key,
says Shawyer, is to make the cavity
superconducting. Without electrical resistance,
currents in the cavity walls will not generate
heat. Engineers in Germany working on the next
generation of particle accelerators have
achieved a Q of several billion using
superconducting cavities. If Shawyer can match
that performance, he calculates that the thrust
from a microwave engine could be as high as
30,000 newtons per kilowatt - enough to lift a large car.
This raises another question. Why haven't
physicists stumbled across the effect before?
They have, says Shawyer, and they design their
cavities to counter it. The forces inside the
latest accelerator cavities are so large that
they stretch the chambers like plasticine. To
counteract this, engineers use piezoelectric
actuators to squeeze the cavities back into
shape. "I doubt they've ever thought of turning
the force to other uses," he says.
No doubt his superconducting cavities will be
hard to build, and Shawyer is realistic about
the problems he is likely to meet. Particle
accelerators made out of niobium become
superconducting at the temperature of liquid
helium - only a few degrees above absolute zero.
That would be impractical for a motor, Shawyer
believes, so he wants to find a material that
superconducts at a slightly higher temperature,
and use liquid hydrogen, which boils at 20
kelvin, as the coolant. Hydrogen could also
power a fuel cell or turbine to generate electricity for the emdrive.
In the meantime, he wants to test the device
with liquid nitrogen, which is easier to handle.
It boils at 77 kelvin, a temperature that will
require the latest generation of
high-temperature ceramic superconductors.
Shawyer hasn't yet settled on the exact
material, but he admits that any ceramic will be
tricky to incorporate into the design because of
its fragility. It will have to be reliably
bonded to the inside of a cavity and mustn't
crack or flake when cooled. There are other
problems too. The inside of the cavity will
still be heated by the microwaves, and this will
possibly quench the superconducting effect.
"Nobody has done this kind of work," Shawyer
says. "I'm not expecting it to be easy."
Then there is the issue of acceleration. Shawyer
has calculated that as soon as the thruster
starts to move, it will use up energy stored in
the cavity, draining energy faster than it can
be replaced. So while the thrust of a motionless
emdrive is high, the faster the engine moves,
the more the thrust falls. Shawyer now reckons
the emdrive will be better suited to powering
vehicles that hover rather than accelerate
rapidly. A fan or turbine attached to the back
of the vehicle could then be used to move it
forward without friction. He hopes to
demonstrate his first superconducting thruster within two years.
What of the impact of such a device? On my
journey home I have plenty of time to speculate.
No need for wheels, no friction. Shawyer
suggested to me before I left that a hover car
with an emdrive thruster cooled and powered by
hydrogen could be a major factor in converting
our society from a petrol-based one to one based
on hydrogen. "You need something different to
persuade people to make the switch. Perhaps
being able to move in three dimensions rather than two would do the trick."
What about aircraft without wings? I'm aware
that my feeling of scepticism is being replaced
by a more dangerous one of unbounded optimism.
In five minutes of blue-sky thinking you can
dream up a dozen ways in which the emdrive could
change the world. I have an hour ahead of me.
The end of wings and wheels. Now there's a thought.
From issue 2568 of New Scientist magazine, 08 September 2006, page 30-34
--
((Udhay Shankar N)) ((udhay @ pobox.com)) ((www.digeratus.com))
