Ever since aircraft first took to the skies, designers have
striven to make them fly more efficiently by reducing their drag or
air resistance. Today, even a minor drag reduction of a few per cent
is considered advantageous, yielding gains in speed and economy
of operation.

The problem for designers today is how to find even those few
percentage points. The power of computers and intense
competition among aircraft manufacturers ensure that such
increments, when they do occur, are more likely to be of the order of
fractions of percentage points, rather than whole ones. Until now.

Russian scientists have stunned a select group of Western
physicists by claiming they have stumbled on a breakthrough in
plasma technology with the potential to reduce aircraft drag not
merely by a few per cent but by as much as 30% - maybe more.

A plasma is an ionised gas. Run an electric current through a neon
light tube, for example, and the end result is a plasma. Another
common plasma is found in lightning.

The claims are being publicised not by the Russians, but by British
Aerospace (BAe). Representatives from BAe have visited many
previously uncharted former Soviet science establishments over the
past five years in the search for innovative science and technology.
Having "found" the plasma research, BAe is seeking to validate the
claims in laboratory experiments of its own.

The experiments involve the introduction of a plasma or ionised gas
into the airstream in front of an aircraft. If BAe can substantiate
Russia's claims - and there is considerable scepticism that there is
anything measurably real about the Russian work - it could lead to
one of the biggest leaps in aircraft design since the coming of the
jet age.

According to the Russians, the potential advantages of "plasma
aerodynamics" are not even limited to drag reduction. Other
spin-offs include: sonic boom attenuation - delaying the onset of an
aircraft's supersonic shockwave; aerodynamic control through
selective drag reduction - allowing an aircraft or missile to
manoeuvre by applying the plasma effect to different parts of the
airframe; and thermal protection through reduced air friction.

It could also herald a breakthrough in stealth, since plasma
generation is claimed vastly to reduce radar cross-section. The
absorption of radio waves by plasmas has been well-known since
the early days of manned space flight. The communications
black-out that a space vehicle encounters on re-entry is caused by
the shielding effects of plasma. This builds naturally in front of the
spacecraft as it hits the Earth's atmosphere and shocks the air to
high temperature.

The same principle applies to the absorption of radar energy.
Although the aircraft would appear to glow like a lightbulb, with
enough plasma generators to cover the entire airframe, it could be
rendered totally invisible to radar.

The story of how Russia's plasma research came to reside at BAe
began in the early 1990s. For some years, the UK Ministry of
Defence (MoD) and elements of the UK aerospace industry had
been aware of the potentially beneficial effects of plasmas on
airframe design; low-key experiments, indeed, had been conducted
in the UK in the
early 1980s.

Following the collapse of the Soviet Union in 1991, BAe struck an
agreement with a Russian government agency charged with
realising commercial benefit from the sale or licensing of technology
and products developed under former Soviet space, aerospace and
defence programmes. The accord was supposed to lead to
synergies that would benefit both parties.

The deal broke down as the Russians tried to sell everything "from
night sights to jet engines", according to one UK official, and the
Russian market was soon found to be almost worthless due to the
economy's dire state. However, the premise was deemed sound. All
it needed, BAe officials concluded, was some focus.

In 1993, BAe headquarters asked its Bristol-based Sowerby
Research Centre to lead the company's research-gathering project in
Russia and other countries of the CIS. The SRC chose Prof Ron
McEwen, executive scientist at the Bristol centre, to head the
programme. He was familiar with aspects of Soviet fundamental
science after visits to several recently opened `science cities' in the
Moscow area and contacts with Russian scientists at a
high-technology exchange forum in Finland. The new, refocused
BAe charter was now clear. One of its twofold aims was "to enable
the acquisition of former Soviet technologies, materials, processes,
products or facilities relevant to any aspect of BAe operations
when this would be more cost-effective than by other means
available to us".

Among other potentially beneficial technologies, BAe has been
looking at former Soviet techniques for welding aircraft primary
structures, a technique scoffed at by the rest of the world, but for
which the Russians are claiming weight savings of up to 40%. With
its partners, BAe is also evaluating new Russian-developed
aluminium alloys. Russia developed the world's first
aluminium-lithium alloys, a material that has contributed much to the
aerospace industry.

It was, however, the second aspect of the BAe charter that proved
instrumental in the plasma discovery. This objective was "to
investigate claims of hitherto unknown former Soviet capabilities
where these appear to offer the possibility of technical advantage".

Prof McEwen began trawling Russia in 1994. He initially enquired
about possible scientific breakthroughs at intermediate levels -
university directors - descending deeper as his investigation went
on into individual departments. "I became well-known within the
Moscow region, so much so that people started coming to me," he
said.

He began to pick up rumours that the Russians had been
conducting exotic experiments with plasmas in the aerospace field.
"They're complicated, a bit difficult to control and understand,
though a lot is understood, especially about relatively
low-temperature plasmas," said Prof McEwen.

Intriguingly, the Russians maintained they had developed "special
plasmas" that behaved differently at high pressures, when they are
normally difficult to sustain. To garner Prof McEwen's interest, a
director of one particular institute demonstrated the effect with a
portable, box-like device from which a jet of plasma would shoot out
and punch a hole through a razor-blade.

The Russians maintained that the technology was semi-secret and
that it had potential applications in the anti-ballistic missile field and
within supersonic combustion ramjets (scramjets) for hypersonic
aircraft. Prof McEwen, however, was unimpressed. Besides the
sideshow atmosphere, BAe had no interest in either application.

The effect was sufficiently interesting, however, for him to
commission a Russian scientist to write a review of all unclassified
Soviet work in the plasma field. When complete, the company
realised it possessed what was probably the first truly authoritative
account of Russian work on plasmas. It documented papers that
promised massive drag reductions by applying plasmas to flying
vehicles.

"Normally, aerodynamicists can design the shape of a flying vehicle
to suit the range of atmospheric conditions, speeds and so on that
it will experience," Prof McEwen said. "They assume there is
nothing they can do about the atmosphere itself. The Russian
approach, on the other hand, seeks to alter the atmosphere through
which the vehicle is flying."

An important parameter is the speed of sound, which depends on
the temperature and the specific heats of the gas. Specific heats are
in turn related to the complexity of the molecules comprising the
gas. The gas laws themselves depend on the forces between the
molecules. If some of the molecules are not just N2 and O2 - the
usual constituents of air - but more complex ones, or if there are
unusual forces between them, the result is an atmosphere modified
from the norm and this will alter the aerodynamics of a body flying
through it. The question, according to Prof McEwen, is: "What are
the details and how can it be made to work to our advantage?" He
returned to Russia in 1996 with academic and company aerodynamic
experts. Mainly sceptical, they were keen to take a more in-depth
look at the Russians' so-called "special" plasmas.

Previous experiments conducted at TsAGI - the Central
Aerodynamics and Hydrodynamics Institute outside Moscow - had
shown drag reductions, but these had explored conditions not of
immediate interest to BAe. A further set of experiments was set up
under the auspices of BAe Military Aircraft, Sowerby Research
Centre, the UK MoD and the UK Defence Evaluation and Research
Agency (DERA).

While BAe was mainly interested in plasma application to aircraft
for high-subsonic/low-supersonic, medium-altitude flight - the
regime in which most of its military and civil products fly - DERA
was keen to evaluate its wider implications, and for hypersonic
flight in particular. The Russians themselves were stressing the
potential application of plasmas at high altitudes and speeds at, or
in excess of, Mach 5.

In the series of UK-sponsored tests run at TsAGI at the end of
1996, drag reductions were again noted. About this time, BAe and
DERA became aware of a growing interest in this topic in the USA
and were invited to participate in an expert meeting in Colorado last
June. Although many US delegates attended, little focused research
had apparently been conducted in the USA until then. The work by
BAe and DERA in collaboration with the Russians made the US
community take notice.

That the USA is interested in the potential of plasma aerodynamics
is beyond doubt. US officials said that a "major meeting" on the
subject has since been held at Princeton University, New Jersey,
and more recently at Norfolk, Virginia. Furthermore, US plasma
experiments have been carried out, some of them replicating the
Russian tests. However, the conclusions drawn from their work so
far are by no means clear.At NASA's Langley Research Center, the
focus of renewed US hypersonic activity, scepticism about the
value of plasma aerodynamics abounds. "There is no smoking
gun," said Dennis Bushnell, senior scientist at the facility. "There is
no phenomenon here. What we have are experimental observations
only. If there's anything in it, then there's no defensible theory."

Bushnell conceded that US experiments have recorded an effect - a
drop in drag - and that the Russian work is "worth investigating and
running to ground". He is dismissive, however, of the measurement
techniques that the Russians have used to analyse this "plasma
magic", as he calls it. "Besides, even if there is an effect, what do
you do with it?" he asked. "Is there any new physics here? Even if
there is, there's the whole issue of how you make use of it."

One concern is that the energy needed to generate a sufficiently
workable plasma may outweigh the energy savings that may accrue
from a few percentage points in drag reduction. US experiments into
plasma aerodynamics are likely to continue for at least another 18
months, according to US officials, under the aegis of the USAF's
Wright Laboratory at Wright-Patterson AFB, Ohio, at NASA and
within the Air Force Office of Scientific Research.

Part of the rationale for BAe's decision to go public on its plasma
co-operation with the Russians is borne of the desire to do more
work with the USA. The nightmare scenario for any sophisticated
aerospace nation, the UK included, is that a breakthrough in this
field by another country could render its current technology
obsolete. A number of plasma experiments, heavily based on
Russian work, are continuing at BAe's Warton facility in
Lancashire.

BAe's Prof McEwen is philosophical about all that he has observed
to date. "Are the Russians achieving anything other than dumping
heat into the airstream?" he asked. "There certainly are effects we
just can't explain at the moment and we have to continue our
investigations until things become clearer. No-one, not even the
Russians, has successfully exploited the technology. Yet it does
seem to have the potential to yield aerodynamic advantage."