The Lockheed U-2, nicknamed "Dragon Lady", is a
single-engine, very high-altitude reconnaissance aircraft operated by the
United States Air Force (USAF) and previously flown by the Central Intelligence
Agency (CIA). It provides day and night, very high-altitude (70,000 feet /
21,000 meters), all-weather intelligence gathering. The aircraft is also used
for electronic sensor research and development, satellite calibration, and
satellite data validation.
Development
In the early 1950s, with Cold War tensions on the rise, the
U.S. military desired better strategic reconnaissance to help determine Soviet
capabilities and intentions. The existing reconnaissance aircraft, primarily
bombers converted for reconnaissance duty, were vulnerable to anti-aircraft
artillery, missiles, and fighters. It was thought an aircraft that could fly at
70,000 feet (21,000 m) would be beyond the reach of Soviet fighters, missiles,
and even radar. This would allow overflights to take aerial photographs.
Under the code name "Bald Eagle", the Air Force
gave contracts to Bell Aircraft, Martin Aircraft, and Fairchild Engine and
Airplane to develop proposals for the new reconnaissance aircraft. Officials at
Lockheed Aircraft Corporation heard about the project and asked aeronautical engineer
Clarence "Kelly" Johnson to come up with a design. Johnson was a
brilliant designer, responsible for the P-38, and the P-80. He was also known
for completing projects ahead of schedule, working in a separate division of
the company jokingly called the Skunk Works.
Johnson's design, called the CL-282, married long
glider-like wings to the fuselage of another of his designs, the Lockheed F-104
Starfighter. To save weight, his initial design did not have conventional
landing gear, taking off from a dolly and landing on skids. The design was
rejected by the Air Force, but caught the attention of several civilians on the
review panel, notably Edwin Land, the father of instant photography. Land
proposed to CIA director Allen Dulles that his agency should fund and operate
this aircraft. After a meeting with President Eisenhower, Lockheed received a
$22.5 million contract for the first 20 aircraft. It was renamed the U-2, with
the "U" referring to the deliberately vague designation
"utility". The CIA assigned the cryptonym "Aquatone" to the
project, with the Air Force using the name "Oilstone" for their
support to the CIA. The first flight occurred at the Groom Lake test site (Area
51) on August 1, 1955, during what was only intended to be a high-speed taxi
run. The sailplane-like wings were so efficient that the aircraft jumped into
the air at 70 knots (81 mph; 130 km/h).
James Baker developed the optics for a large-format camera
to be used in the U-2 while working for Perkin-Elmer. These new cameras had a
resolution of 2.5 feet (76 cm) from an altitude of 60,000 feet (18,000 m). Balancing is so critical on the U-2 that the camera had to use a split film,
with reels on one side feeding forward while those on the other side feed
backward, thus maintaining a balanced weight distribution through the whole
flight.
When the first overflights of the Soviet Union were tracked
by radar, the CIA initiated Project Rainbow to reduce the U-2's radar cross
section. This effort ultimately proved unsuccessful, and work began on a
follow-on aircraft, which resulted in the Lockheed A-12 Oxcart. Manufacturing
was restarted in the 1980s to produce TR-1, an updated and modernized design of
the U-2.
Design
The unique design that gives the U-2 its remarkable
performance also makes it a difficult aircraft to fly. It was designed and manufactured for minimum
airframe weight, which results in an aircraft with little margin for error. Most aircraft were single-seat versions, with only five two-seat trainer
versions known to exist. Early U-2 variants were powered by Pratt & Whitney
J57 turbojet engines. The U-2C and TR-1A variants used the more powerful Pratt
& Whitney J75 turbojet. The U-2S and TU-2S variants incorporated the even
more powerful General Electric F118 turbofan engine. High-aspect-ratio wings
give the U-2 some glider-like characteristics, with a lift-to-drag ratio
estimated in the high 20s. To maintain their operational ceiling of 70,000 feet
(21,000 m), the U-2A and U-2C models (no longer in service) must fly very near
their maximum speed. The aircraft's stall speed at that altitude is only 10
knots (12 mph; 19 km/h) below its maximum speed. This narrow window was
referred to by the pilots as the "coffin corner". For 90% of the time
on a typical mission the U-2 was flying within only five knots above stall,
which might cause a decrease in altitude likely to lead to detection, and
additionally might overstress the lightly built airframe.
The U-2's flight controls are designed around the normal
flight envelope and altitude at which the aircraft was intended to fly. The
controls provide feather-light control response at operational altitude.
However, at lower altitudes, the higher air density and lack of a
power-assisted control system makes the aircraft very difficult to fly. Control
inputs must be extreme to achieve the desired response in flight attitude, and
a great deal of physical strength is needed to operate the controls in this
manner.
The U-2 is very sensitive to crosswinds which, together with
its tendency to float over the runway, makes the U-2 notoriously difficult to
land. As the aircraft approaches the runway, the cushion of air provided by the
high-lift wings in ground effect is so pronounced that the U-2 will not land
unless the wing is fully stalled. To assist the pilot, the landing U-2 is paced
by a chase car (usually a "souped-up" performance model including a
Ford Mustang SSP, Chevrolet Camaro B4C, Pontiac GTO, and the Pontiac G8 GT)
with an assistant (another U-2 pilot) who "talks" the pilot down by
calling off the declining height of the aircraft in feet as it decreases in
airspeed.
Instead of the typical tricycle landing gear, the U-2 uses a
bicycle configuration with a forward set of main wheels located just behind the
cockpit, and a rear set of main wheels located behind the engine. The rear
wheels are coupled to the rudder to provide steering during taxiing. To
maintain balance while taxiing, two auxiliary wheels, called "pogos"
are added for takeoff. These fit into sockets underneath each wing at about
mid-span, and fall off during takeoff. To protect the wings during landing,
each wingtip has a titanium skid. After the U-2 comes to a halt, the ground
crew re-installs the pogos one wing at a time, then the aircraft taxis to
parking. Because of the high operating altitude, the pilot must wear the
equivalent of a space suit. The suit delivers the pilot's oxygen supply and
emergency protection in case cabin pressure is lost at altitude (the cabin
provides pressure equivalent to about 29,000 feet / 8,800 meters). To prevent
hypoxia and decrease the chance of decompression sickness, pilots don a full
pressure suit and begin breathing 100% oxygen one hour prior to launch to
remove nitrogen from the body; while moving from the building to the aircraft
they breathe from a portable oxygen supply.
The aircraft carries a variety of sensors in the nose, Q-bay
(behind the cockpit, also known as the camera bay), and wing pods. The U-2 is
capable of simultaneously collecting signals, imagery intelligence and air
samples. Imagery intelligence sensors include either wet film photo,
electro-optic or radar imagery – the latter from the Raytheon ASARS-2 system.
It can use both line-of-sight and beyond-line-of-sight data links. One of the
most unusual instruments in the newest version of the U-2 is the off-the-shelf
Sony video camera that functions as a digital replacement for the purely
optical viewsight (an upside down periscope-like viewing device) that was used
in older variants to get a precise view of the terrain directly below the
aircraft, especially during landing.
DISCLAIMER: The
material content provided on this page is generated by another sources and
consequently features user-generated content. While we do our best to stop
offensive material appearing, ekotriyanggono.com cannot be held responsible for
all of the material that may be displayed on this page. If you object to any
article or picture, please leave us a comment in this page.
