And:
Military jet engines
A jet engine is an engine that discharges a fast moving jet of
fluid to generate thrust in accordance with Newton's third law of motion.
This broad definition of jet engines includes turbojets, turbofans, rockets
and ramjets and water jets, but in common usage, the term generally refers
to a gas turbine used to produce a jet of high speed exhaust gases for
special propulsive purposes.
History
In the 1930s, the piston engine in its many different forms (rotary and
static radial, aircooled and liquid-cooled inline) was the only type of
powerplant available to aircraft designers. However, engineers were
beginning to realize conceptually that the piston engine was self-limiting
in terms of the maximum performance which could be attained; the limit was
essentially one of propeller efficiency. This seemed to peak as blade tips
approached the speed of sound. If engine, and thus aircraft, performance
were ever to increase beyond such a barrier, a way would have to be found to
radically improve the design of the piston engine, or a wholly new type of
powerplant would have to be developed. This was the motivation behind the
development of the gas turbine engine, commonly called a "jet" engine, which
would become almost as revolutionary to aviation as the Wright brothers'
first flight.
The key to a practical jet engine was the gas turbine, used to extract
energy to drive the compressor from the engine itself. In 1929, Aircraft
apprentice Frank Whittle formally submitted his ideas for a turbo-jet to his
superiors. On 16 January 1930 in England, Whittle submitted his first patent
(granted in 1932). The patent showed a two-stage axial compressor feeding a
single-sided centrifugal compressor. Whittle would later concentrate on the
simpler centrifugal compressor only, for a variety of practical reasons. In
1935 Hans von Ohain started work on a similar design in Germany, seemingly
unaware of Whittle's work. Whittle had his first engine running in April
1937. It was liquid-fuelled, and included a self-contained fuel pump. Von
Ohain's engine, as well as being 5 months behind Whittle's, relied on gas
supplied under external pressure, so was not self-contained. Whittle
unfortunately failed to secure proper backing for his project, and so fell
behind Von Ohain in the race to get a jet engine into the air.
One problem with both of these early designs, which are called
centrifugal-flow engines, was that the compressor worked by "throwing"
(accelerating) air outward from the central intake to the outer periphery of
the engine, where the air was then compressed by a divergent duct setup,
converting its velocity into pressure. An advantage of this design was that
it was already well understood, having been implemented in centrifugal
superchargers. However, given the early technological limitations on the
shaft speed of the engine, the compressor needed to have a very large
diameter to produce the power required. A further disadvantage was that the
air flow had to be "bent" to flow rearwards through the combustion section
and to the turbine and tailpipe.
Austrian Anselm Franz of Junkers' engine division (Junkers Motoren or Jumo)
addressed these problems with the introduction of the axial-flow compressor.
Essentially, this is a turbine in reverse. Air coming in the front of the
engine is blown towards the rear of the engine by a fan stage (convergent
ducts), where it is crushed against a set of non-rotating blades called
stators (divergent ducts). The process is nowhere near as powerful as the
centrifugal compressor, so a number of these pairs of fans and stators are
placed in series to get the needed compression. Even with all the added
complexity, the resulting engine is much smaller in diameter. Jumo was
assigned the next engine number, 4, and the result was the Jumo 004 engine.
After many lesser technical difficulties were solved, mass production of
this engine started in 1944 as a powerplant for the world's first
jet-fighter aircraft, the Messerschmitt
Me 262. After the
end of the war the German Me 262 aircraft were extensively studied by the
victorious allies and contributed to work on early Soviet and US jet
fighters.
Centrifugal-flow engines have improved since their introduction. With
improvements in bearing technology, the shaft speed of the engine was
increased, greatly reducing the diameter of the centrifugal compressor. The
short engine length remains an advantage of this design. Also, its engine
components are robust; axial-flow compressors are more liable to foreign
object damage.
British engines also were licensed widely in the US. Their most famous
design, the Nene would also power the USSR's jet aircraft after a technology
exchange. American designs would not come fully into their own until the
1960s.
Types
There are many different types of jet engines, all of which get propulsion
from a high speed exhaust jet. Some of the most important types are listed
below.
| Type |
Description |
Advantages |
Disadvantages |
|
Turbojet |
Generic term for simple turbine engine |
Simplicity of design |
Basic design, misses many improvements in efficiency and power |
|
Turbofan |
First stage compressor greatly enlarged to provide bypass
airflow around engine core |
Quieter due to greater mass flow and lower total exhaust speed,
more efficient for a useful range of subsonic airspeeds for same
reason, cooler exhaust temperature |
Greater complexity (additional ducting, usually multiple
shafts), large diameter engine, need to contain heavy blades. More
subject to FOD and ice damage. Top speed is limited due to the
potential for shockwaves to damage engine |
| Ramjet |
Intake air is compressed entirely by speed of oncoming air and
duct shape (divergent) |
Very few moving parts, Mach 0.8 to Mach 5+, efficient at high
speed (> Mach 2.0 or so), lightest of all airbreathing jets
(thrust/weight ratio up to 30 at optimum speed) |
Must have a high initial speed to function, inefficient at slow
speeds due to poor compression ratio, difficult to arrange shaft
power for accessories, usually limited to a small range of speeds,
intake flow must be slowed to subsonic speeds, noisy, fairly
difficult to test, finicky to kept lit. |
| Scramjet |
Similar to a ramjet without a diffuser; airflow through the
entire engine remains supersonic |
Few mechanical parts, can operate at very high
Mach numbers
(Mach 8 to 15) with good efficiencies.
|
Still in development stages, must have a very high initial speed
to function (Mach >6), cooling difficulties, very poor thrust/weight
ratio (~2), extreme aerodynamic complexity, airframe difficulties,
testing difficulties/expense |
| Pulsejet |
Air is compressed and combusted intermittently instead of
continuously. Some designs use valves. |
Very simple design, commonly used on model aircraft |
Noisy, inefficient (low compression ratio), works poorly on a
large scale, valves on valved designs wear out quickly |
| Pulse detonation engine |
Similar to a pulsejet, but combustion occurs as a detonation
instead of a deflagration, may or may not need valves |
Maximum theoretical engine efficiency |
Extremely noisy, parts subject to extreme mechanical fatigue,
hard to start detonation, not practical for current use |
| Rocket |
Carries all propellants onboard, emits jet for propulsion |
Very few moving parts, Mach 0 to Mach 25+, efficient at very
high speed (> Mach 10.0 or so), thrust/weight ratio over 100, no
complex air inlet, high compression ratio, very high speed
(hypersonic) exhaust, good cost/thrust ratio, fairly easy to test,
works in a vacuum-indeed works best exoatmospheric which is kinder
on vehicle structure at high speed. |
Needs lots of propellant- very low specific impulse typically
100-450 seconds. Extreme thermal stresses of combustion chamber can
make reuse harder. Typically requires carrying oxidiser onboard
which increases risks. Extraordinarily noisy. |
|
A turbojet engine is a type of internal combustion engine often
used to propel aircraft. Air is drawn into the rotating compressor
via the intake and is compressed, through successive stages, to a
higher pressure before entering the combustion chamber. Fuel is
mixed with the compressed air and ignited by flame in the eddy of a
flame holder. This combustion process significantly raises the
temperature of the gas. Hot combustion products leaving the
combustor expand through the turbine, where power is extracted to
drive the compressor. Although this expansion process reduces both
the gas temperature and pressure at exit from the turbine, both
parameters are usually still well above ambient conditions. The gas
stream exiting the turbine expands to ambient pressure via the
propelling nozzle, producing a high velocity jet in the exhaust
plume. If the jet velocity exceeds the aircraft flight velocity,
there is a net forward thrust upon the airframe.
Under normal circumstances, the pumping action of the compressor
prevents any backflow, thus facilitating the continuous-flow process
of the engine. Indeed, the entire process is similar to a
four-stroke cycle, but with induction, compression, ignition,
expansion and exhaust taking place simultaneously, but in different
sections of the engine. The efficiency of a jet engine is strongly
dependent upon the overall pressure ratio (combustor entry
pressure/intake delivery pressure) and the turbine inlet temperature
of the cycle.
It is also perhaps instructive to compare turbojet engines with
propeller engines. Turbojet engines take a relatively small mass of
air and accelerate it by a large amount, whereas a propeller takes a
large mass of air and accelerates it by a small amount. The
high-speed exhaust of a jet engine makes it efficient at high speeds
(especially supersonic speeds) and high altitudes. On slower
aircraft and those required to fly short stages, a gas
turbine-powered propeller engine, commonly known as a turboprop, is
more common and much more efficient. Very small aircraft generally
use conventional piston engines to drive a propeller but small
turboprops are getting smaller as engineering technology improves.
The turbojet described above is a single-spool design, in which a
single shaft connects the turbine to the compressor. Higher overall
pressure ratio designs often have two concentric shafts, to improve
compressor stability during engine throttle movements. The outer
high pressure (HP) shaft connects the HP compressor to the HP
turbine. This HP Spool, with the combustor, forms the core or gas
generator of the engine. The inner shaft connects the low pressure
(LP) compressor to the LP Turbine to create the LP Spool. Both
spools are free to operate at their optimum shaft speed.
Most modern jet engines are actually turbofans, where the low
pressure compressor acts as a fan, supplying supercharged air to not
only the engine core, but to a bypass duct. The bypass airflow
either passes to a separate 'cold nozzle' or mixes with low pressure
turbine exhaust gases, before expanding through a 'mixed flow
nozzle'.
Forty years ago there was little difference between civil and
military jet engines, apart from the use of afterburning in some
(supersonic) applications.
Civil turbofans today have a low specific thrust (net thrust
divided by airflow) to keep jet noise to a minimum and to improve
fuel efficiency. Consequently the bypass ratio (bypass flow divided
by core flow) is relatively high (ratios from 4:1 up to 8:1 are
common). Only a single fan stage is required, because a low specific
thrust implies a low fan pressure ratio.
Today's military turbofans, however, have a relatively high
specific thrust, to maximize the thrust for a given frontal area,
jet noise being of little consequence. Multi-stage fans are normally
required to achieve the relatively high fan pressure ratio needed
for a high specific thrust. Although high turbine inlet temperatures
are frequently employed, the bypass ratio tends to be low (usually
significantly less than 2.0). |
Comparative suitability for (left to right)
turboshaft, low bypass and turbojet to fly at 10 km attitude in
various speeds. Horizontal axis - speed, m/s. Vertical axis carries
only logical meaning.
Efficiency
as a function of speed of different Jet types. Although efficiency
plummets with speed, greater distances are covered, it turns out
that efficiency per unit distance (per km or mile) is roughly
independent of speed for Jet engines as a group. |
Manufactures
The main manufactures of military jet engines today are :
- Pratt & Whitney (US; F-16, F-22)
- General Electric (US; B-1, B-2)
- Rolls-Royce (UK; Harrier)
- Tumansky (Soviet Union; Mig-25, Mig-29)
- Lyulka/Saturn (Soviet Union; SU-27, SU-37)
- Klimov (Soviet Union; Mig-17)
- Turbo-Union (UK, Germany, Italy; Tornado)
- EuroJet (UK, Germany, Italy, Spain; Eurofighter Typhoon)
- SNECMA (France; Mirage-2000, Rafale)
Note: Part of the text is from Wikipedia.
Military aircraft jet-engines in more detail
History
"After World War Two, piston engines continued to power civil airliners
for many years, but in the field of military aircraft they were rapidly
displaced by the gas turbine. Fighters and bombers switched to the turbojet,
transports and maritime-patrol aircraft used turboprops, and helicopters
benefited greatly from changing to turboshaft engines. The change meant more
power for less weight, far greater reliability, no cooling problems and
safer kerosene-type fuels.
With extraordinary reluctance, designers eventually recognized that the
turbofan, offering a wide choice of bypass ratio (BPR - the mass flow of air
in the bypass duct divided by that through the core), could with advantage
replace the turbojet. In supersonic aircraft the need to minimize frontal
area means that BPR is seldom as high as 1, and even then the installation
must be done with great care. When the J79 turbojet of 79.63 kN thrust
installed in the McDonnell Douglas
F-4 Phantom was
replaced in the British versions by the Rolls-Royce Spey turbofan of 91.25
kN the change made the aircraft slower in level flight, while giving
improvements in take-off and climb performance!
Today the turbojet is almost extinct, except for some countries like
China, where different criteria apply. Elsewhere, the trend has been towards
achieving greater power with engines that are not only lighter but also
smaller and dramatically simpler. For example, the Spey Mk 202, the engine
of the RAF Phantoms, had a total of 17 stages of blading in the compressors
(5+12 flow pressure+high pressure) and four stages of blading in the
turbines (2+2). The next-generation RB. 199, engine of the
Tornado, has 12
stages of compression (3+3+6) and again four stages of expansion through the
turbines (1+1+2), whereas today's Eurojet EJ200, engine of the
Eurofighter, has only eight compressor stages (3+5) and two turbine
stages (1+ 1).
In general, the more stages of blading an axial-flow compressor has, the
greater the overall pressure ratio (OPR) and the better the fuel economy
(and thus, for a given aircraft tankage, the greater the range and
endurance). One might therefore think that the simpler compressors have been
achieved at the expense of more rapid fuel burn, but in fact the reverse is
true. The OPR of the Phantom's Spey was 20, the figure for the Tornado
engine is 23, and for the Eurofighter it has gone up to 26. Indeed, the
next-generation fighter engine could have an OPR of 35, with only six or
seven stages of blading.
Benefits of Simplicity
Simpler engines mean greater reliability, better resistance to battle
damage, easier maintenance, and several other advantages including lower
cost, though cost is not as dominant as it is in the civil sector. In the
immediate postwar era, up to 1970, it was normal practice not to introduce
an engine to the airlines until hundreds or even thousands had gained
experience in fighters and bombers. The two families then diverged.
Airliners needed engines offering the lowest possible fuel consumption and
lowest possible noise at airports, and these (surprisingly slowly)
eventually led to today's engines with a BPR of from 5 to 9, with enormous
fans. Combat aircraft need slim engines, as already noted, so military
experience is seldom much help to civil engines (though the best-selling
CFM56 has the core of a long-established military engine, the F101 used in
the Rockwell B-1B
Lancer).
Today, the military trend towards greater simplicity is being echoed by
civil engines. Nearly 30 years ago, special turbojets and turbofans were
being produced purely to lift VTOL (vertical take-off and landing) aircraft.
They were used only at take-off and landing, so were made as simple as
possible. Like other engines, they sometimes had two spools (low-pressure
and high-pressure compressors, each driven by its own turbine), and the
aerodynamicists found that by making the spools rotate in opposite daemons,
it was possible to do away with at least some of the stator (fixed) blades
ahead of the turbine rotors.
Afterburner
Apart from Concorde, which has a low-augmentation form of reheat
(afterburning), civil aircraft do not burn fuel in the jetpipe downstream of
the turbines. Supersonic aircraft have afterburning engines in order to
increase the energy in the jet so that, properly expanded in a special
nozzle, it can be ejected at highly supersonic speed, in order to achieve
the highest flight Mach number possible. Such aircraft as the
MiG-25 Foxbat
and Lockheed SR-71
Blackbird can fly at Mach 3 (three times the speed of sound).
Today's fighters have augmentation, the name given to burning extra fuel
downstream of the turbines of a turbofan engine. With a turbofan there is
abundant oxygen in the mixed flow in the jetpipe, much of which has not
passed through the core and thus has had no fuel already burned in it. In
any case, the latest engines are so powerful that augmentation is needed
only on rare occasions (for example, in close combat) when maximum thrust is
needed, because it burns fuel rapidly and also shortens engine life.
Thus, many modem fighters are capable of making a cold (unaugmented)
take-off. The first to do this were the Grumman
F-14B and F-14D
re-engined versions of the Tomcat naval fighter. Fitting the General
Electric F110-400 engine not only transformed reliability but also increased
dry thrust to 71.6 kN (16,080 lb), not far short of the thrust of the
original TF30 engine in full afterburner. As a result, the F-14 can be
catapulted off a carrier without using afterburner, giving an increase in
mission range of no less than 62%. Moreover, the greater dry thrust results
in a reduction in time to climb to patrol altitude of 61%!
Supercruise and stealth
Going on from there, military engines are now so powerful that the latest
fighters can supercruise, the term for flying at sustained supersonic speed
without the use of the afterburner. Earlier supersonic aircraft could exceed
Mach I on the level only in maximum afterburner, when the rate at which fuel
was burned was so high that supersonic speed could not be sustained for
longer than about a minute. Today such aircraft as the Lockheed Martin
F-22 Raptor or
Eurofighter
Eurofighter Typhoon can accelerate to supersonic speed (with or without
using augmentation) and then sustain such a speed indefinitely in dry
thrust.
Apart from dramatically reducing the rate of fuel consumption, the
ability to supercruise also reduces the IR (infrared) signature by some 75%.
Clearly there is little point in making a 'stealth' aircraft, almost
invisible to hostile radars, if its IR emissions proclaim its presence like
a lighthouse. Many (indeed, most) of today's air-to-air guided missiles
(AAMs) home in on a source of IR radiation, and a fighter in afterburner
finds it much more difficult to throw a heat-homing AAM off the scent than a
stealthy one in dry thrust, even in supercruise.
Hypersonics
Of course, there is a relationship between the speed of an aircraft and
that of its propulsive jet. For over 40 years, visionaries - and even a few
professional aircraft designers - have considered military aircraft that are
capable of hypersonic speed. This term is usually taken to mean Mach numbers
several times greater than 1, such as Mach 5, which at high altitude equates
to 2868 kts (5310 km/h). In my opinion there is no way a Mach 5 aircraft
could supercruise, if by that it meant using a turbofan in dry thrust.
A Mach 5 aircraft will have to have an engine running continuously in
full augmentation or, preferably, a ramjet. The trouble with a ramjet is
that such engines cannot start from rest. Back in 1951, the Republic
Aviation began beavering away at the XF-103, a fighter to cruise at Mach 3.7
(3,930km/h). This would have had a Wright J67, an afterburning turbojet
based on the Bristol Siddeley Olympus, installed in a vast duct with a valve
which, at high airspeed, could be switched over to bypass the J67 and
convert the propulsion system into a ramjet. In August 1957 program was
cancelled.
The SR-71 Blackbird had Pratt & Whitney J58 engines, which at Mach 3
behaved like ramjets, the J58s merely getting in the way of the hurricane
passing through the nacelles. Whatever kind of engine might be invented, it
is sure to have a nozzle whose profile and area can be varied. This by
itself is quite a challenge, but beautiful examples can be seen on the
latest fighters. Dr Viktor Chepkin is sad that his ALAI engines in the
MiG 1.42/1.44
have so far stayed on the ground, because in his opinion, this augmented
turbofan is a world-beater. Anyone who has watched the
Su-27 Flanker
perform, will know that his engines are pretty impressive, and he says "The
AL-41 is a totally new generation engine".
Vectored thrust
Dr Chepkin is one of the Russians who have taken the bull by the horns
and boldly combined a fully variable nozzle with the ability to vector
(point in different direction). Vectored thrust was pioneered 50 years ago,
initially by simply having a switch-in deflector to direct the jet either to
go out the back or else through a separate nozzle pointing downwards. This
was flown in Meteor RA490 in 1954, but it was a brutishly crude arrangement,
and I would have hated to be the pilot if one engine had diverted while the
other did not.
Since then, vectored thrust has taken many forms. Some aircraft, such as
the Bell Model 65 of 1954 and the supersonic German VJ 101C of 1963, adopted
the seemingly obvious method of mounting complete engines on pivots, so that
they could point downwards or backwards. Bristol Siddeley designers adopted
the more subtle method of fitting a turbofan with two pairs of nozzles, two
for fan air and two more at the back for the hot jet. All four were
mechanically linked (by motorcycle chain!) to swivel in unison, and the
result was the
Harrier. Despite the scorn of the USAF, which apparently thought there
would always be a handy 10,000ft (3km) runway in any future war, some
Harriers actually got into service, and proved so crucial in the Falklands
that vectored-thrust versions of the
Joint Strike Fighter
have equal priority with those needing long runways.
Of course, another form of vectored thrust is to fit a thrust reverser,
to slow the aircraft rapidly after a conventional high-speed landing.
Reversers are universal on big jetliners (even on small ones, except the BAe
I46/RJ and Fokker F28), but are rare on combat aircraft. Offhand, I can
think of only the
Viggen and
Tornado. So far nobody has been clever enough to make an engine that can
vector its thrust in all three modes: for combat agility, for VTOL or STOVL
(short take-off and vertical landing) and to slow a conventional landing.
Today's supersonic fighters use vectoring purely to enhance in-flight
agility. indeed, Eurofighter GmbH (it is a German company) is even at the
Millennium still desperate to try to avoid putting vectoring nozzles on
their otherwise superb aircraft. Despite presumably having watched Comrade
Pugachev and his colleagues demonstrate the superb maneuverability of the
MiG-29
Fulcrum and Su-27 Flanker, their position in late 1999 purported to be
"We think, in the fullness of time there may well be a naval Eurofighter,
and if so, that version might be improved by fitting vectored nozzles".
Fortunately ITP in Spain has developed an excellent vectoring nozzle for the
EJ200 engine, so it will be available when the penny finally drops. Indeed
some Eurofighter folk have told me such nozzles might come "at the first
mid-life update".
Size / unmanned aircraft
The technology of gas-turbine engines has never shown the slightest sign
of approaching a plateau, far less a barrier. Since the dawn of gas-turbine
aviation in 1940, the power available from a given bulk of engine has
doubled roughly every 30 years, while specific fuel consumption (rate of
fuel consumption for a given power output) has consistently fallen below the
most sanguine expectations. If you look at a
Gloster Meteor
you see nacelles that housed engines of 15.6kN (3,500 lb) thrust. Today,
nacelles of the same overall size could house engines with a dry thrust of
156 kN (35,000 lb).
Such power has led to modern fighters becoming impressively large. The
McDonnell Douglas F-15
Eagle seemed big, with a wing area of over 55.7m2, but today the F-22
has a wing with an area of 78 m2, precisely the same as that of the World
War Two Vickers
Wellington heavy bomber. The wing of the MiG 1.44 has an area of 90.5m2.
My own feeling is that future fighters ought to be smaller, and Saab (now in
partnership with British Aerospace) has shown the way to go with the
Gripen. This has
the same engine as the Boeing
F/A-18 Hornet, but
half as many (just as its predecessor the
Saab Draken had the
same engine as the
English Electric Lightning but half as many).
The easiest way to make fighters even smaller is to leave out the pilot.
This has a considerable effect, because replacing the cockpit by 'black
boxes' not only saves space and weight, and eliminates the environmental
system, but also gives the designer greater flexibility in the overall
layout. For example, he can put the engine inlet where the windscreen used
to be, which most designers consider is a route to enhanced stealth
characteristics, without significantly harming pressure recovery in the
inlet during fight maneuvers.
Equally important, leaving out a human crew enables the whole aircraft to
be approximately half as big, whilst at the same time allowing the designers
to go for a maximum acceleration in the vertical plane of at least 20g. Such
an aircraft could literally 'fly rings round' a fighter limited to today's
9g. Just how such aircraft would fly their missions depends on the task, and
is outside the scope of this article. Suffice it to say, the future UAV
(unmanned air vehicle) would almost certainly be single-engined, and could
have an engine with a maximum thrust anywhere from 35,000lb (156kN) down to
350lb (1.56kN). Indeed, aircraft used solely as sensor platforms or decoys
might have engines of a mere 35 lb (0.156kN) st, replacing today's much
slower UAVs powered by tiny piston engines.
Stealth
Eliminating the pilot, as well as any fins, will do much to enhance
stealth qualities. This will focus increased pressure on the need to devise
truly stealthy propulsion system For many years, designers have made it
impossible for hostile, to 'see' the face of the engine, by suitably kinking
the inlet duct (or, as noted, putting it above the fuselage). The propulsive
nozzle is harder, and here there is a need to minimize thermal, visual and
even acoustic signatures. The Lockheed Martin
F-117
Nighthawk nozzles are flattened slits in the trailing edge of the wing,
while those of the B-2
are tucked inside deep channels above the rear part of the wing, upstream of
movable trailing edges.
I have numerous documents, all published openly in the United States,
which purport to explain how the B-2 is even stranger - far stranger - than
it appears. Most are articles published in commercial magazines, some are
openly published US Patents, while a few are open USAF publications by
Wright Aeronautical Laboratory and Air Force Systems Command's Astronautics
Laboratory. They deal with such topics as electric-field propulsion, and
electrogravitics (or anti-gravity), the transient alteration of not only
thrust but also a body's weight. Sci-Fi has nothing on this stuff.
The literature goes back to Faraday, but the idea of electrogravitics
really took off in the 1920s when an American physicist, Townsend T. Brown,
carried out extensive experiments. He may have been the first to recognize
that a capacitor (a dielectric material sandwiched between positive and
negative plates) experiences a force tending to move it in the direction of
the positive face. He found that the electrostatic charge induced a gravity
field between the two plates. Soon he was making capacitors rotate on
whirling arms, and measuring the loss in weight of capacitors with the
positive face turned uppermost.
In 1953, Brown demonstrated to the USAF a whirling rig of 50ft (15.2m)
diameter, which at 150,000 volts (150kV) became a mere blur. The subject was
immediately classified, and for the next 40 years, while 'black' research in
this field made astonishing progress, it was not reported. Though private
individuals continued to experiment, and to take out unclassified patents,
not much surfaced. Exceptions were Electrogravitics Systems (February 1956)
and The Gravitics Situation (December 1956), published for subscribers only
by Aviation Studies (International). This was a London-based 'think tank'
run by two very bright young men: R G 'Dicky' Worcester and John Longhurst.
Unlike the established journals, they published reports and informed comment
without the slightest regard for questions of 'security'. The only time they
were taken to court, they won their case and collected heavy damages.
I was fascinated to read those reports, but had no wish to reside in The
Tower, so I refrained from discussing clever airplanes with leading edges
charged to millions of volts positive and trailing edges at millions of
volts negative. In any case, it all seemed a bit farfetched, especially as
it appeared that the gravity field could not only propel aircraft to
supersonic speed with propulsive efficiency greater than / but could also
lift them independently of the atmosphere.
Wondrous things
Various snippets appeared suggesting that electrostatic fields could not
only do wondrous things in the field of propulsion but could also reduce
aerodynamic turbulence (at any Mach number), reduce radar cross-section and
even virtually eliminate the sonic boom Indeed, back in 1952, Dr M Rose had
noted in unclassified literature: "The positive field.. travelling in
front... acts as a buffer which starts moving the air out of the way. This
field acts as an entering wedge which softens the supersonic barrier..."
From 1985, the name P A LaViolette emerges as author of a shoal of
interesting electrogravitics articles in professional literature.
The first Northrop Grumman B-2 Spirit stealth bomber was rolled out on
November 22,1988, and anyone with the slightest interest in aircraft could
not fail to have noticed the unbelievable leading edge, with a deep profile
coming to a knife-edge almost in line with the upper surface. In 1990, a
NASA 'boffin' retired and perhaps foolishly talked to The Arkansas Democrat
who did not understand his story and ran it under the headline "Ex-NASA
expert says Stealth uses parts from UFO".
What really put the cat among the proverbial pigeons was a feature
published in a March 1992 issue of Aviation Week & Space Technology,
entitled "Black world engineers, scientists, encourage using highly
classified technology for civil applications". For the first time in open
literature, this article explained how the B-2's sharp leading edge is
charged to "many millions of volts", while the corresponding negative charge
is blown out in the jets from the four engines. There is more: though the
General Electric F118 engines can operate as ordinary turbofans, in flight
they act as flame-jet generators, pumping out gas greatly diluted by fresh
air, all at millions of volts negative. The word 'flame' gives a rather
false picture, because in fact the jet comes out not very much hotter than
the surrounding atmosphere.
Unclassified articles have described in some detail how the leading edge
is divided into eight sections, each individually ionized. The section on
each wing immediately upstream of the engines cannot be thus ionized,
because the air would then enter the engines and cancel out the negative
charge in the jets. Accordingly, this is where the Hughes covert strike
radars are installed. They would not be able to 'see' forwards if they were
anywhere else.
Take-off thrust of the F118-100 at sea level is given as '19,000 lb (84.5
kN) class' by Northrop Grumman and as '17,300 lb (77.0 kN)' by the USAF.
These are startlingly low figures for an aircraft whose take-off weight is
said to be 336,500 lb (152,635 kg) and which was until recently said to
weigh 376,000 lb (170,550 kg). Aircraft usually get heavier over the years,
not 20 tones lighter. Even at the supposed reduced weight, the ratio of
thrust to weight is a mere 0.2, an extraordinarily low value for a combat
aircraft.
The USAF has never said anything about B2 speed. It has been tacitly
assumed to be in the Mach 0.8 class, but according to the extensive open
literature, the four FI 18 engines equate to about 25 MW (megawatts) of
electrical power at take-off, but under the influence of the electrogravitic
field the speed could soon become supersonic, the output of the air-diluted
exhaust then rising to at least 100 MW.
Everyone who has heard a B-2 take off has been astonished at the
quietness. Obviously the noise would not be in the same class as the F101
engines of the B-1B in full afterburner, but writers have used the words
'shocking', 'uncanny' and 'incredible' in describing B-2 departures. As for
elimination of contrails (condensation trails) (normally a giveaway even for
a stealth aircraft), the USAF said chlorofluorosulphonic acid was injected
into the jets to eliminate contrails. Later it said this was done by
'regulating exhaust temperatures'. Such an explanation is nonsense;
contrails are ice crystals from water vapor left when hydrocarbon fuel is
burned, and can never be eliminated by 'regulating exhaust temperatures'.
Another point to note is that the channels downstream of the jetpipes appear
to be carbon-fiber composite, which is incompatible with normal jet
temperatures (not because of the fiber but because of the adhesive sticking
them together).
Other writers have commented on the size of the B-2 wing and noted that
its stealth depends on the huge black skin being made of RAM
(radar-absorbent material). This, say the physicists, is 'a high-k,
high-density dielectric ceramic, capable of generating an enormous
electrogravitic lift force when charged'. I could go on and on. We have come
some way from the Lancaster and
B-17, and I seem to
have strayed some way from traditional jet engines."
Text is a rewrite of an article first published by Bill Gunston in
Air International, January 2000
1996-2007 Fighter Planes and Military Aircraft