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Subject: Douglas D-558-2 Skyrocket
Date: 18 Jun 2018 06:25:40 -0700
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https://en.wikipedia.org/wiki/Douglas_D-558-2_Skyrocket
The Douglas D-558-2 Skyrocket (or D-558-II) was a rocket and jet-powered
supersonic research aircraft built by the Douglas Aircraft Company for the
United States Navy. On 20 November 1953, shortly before the 50th anniversary of
powered flight, Scott Crossfield piloted the Skyrocket to Mach 2, or more than
1,290 mph (2076 km/h), the first time an aircraft had exceeded twice the speed
of sound.
The "-2" in the aircraft's designation referred to the fact that the Skyrocket
was the phase-two version of what had originally been conceived as a three-phase
program. The phase-one aircraft, the D-558-1, was jet powered and had straight
wings. The third phase, which never came to fruition, would have involved
constructing a mock-up of a combat type aircraft embodying the results from the
testing of the phase one and two aircraft. The eventual D-558-3 design, which
was never built, was for a hypersonic aircraft similar to the North American
X-15.
When it became obvious that the D558-1 fuselage could not be modified to
accommodate both rocket and jet power, the D558-2 was conceived as an entirely
different aircraft. A contract change order was issued on 27 January 1947 to
formally drop the final three D558-1 aircraft and substitute three new D558-2
aircraft instead.
The Skyrocket featured wings with a 35-degree sweep and horizontal stabilizers
with 40-degree sweep. The wings and empennage were fabricated from aluminum and
the large fuselage was of primarily magnesium construction. The Skyrocket was
powered by a Westinghouse J34-40 turbojet engine fed through side intakes in the
forward fuselage. This engine was intended for takeoff, climb and landing. For
high speed flight, a four-chamber Reaction Motors LR8-RM-6 engine (the Navy
designation for the Air Force's XLR11 used in the Bell X-1), was fitted. This
engine was rated at 6,000 lbf (27 kN) static thrust at sea level. A total of 250
US gallons (950 L) of aviation fuel, 195 US gallons (740 L) of alcohol, and 180
US gallons (680 L) of liquid oxygen were carried in fuselage tanks.
The Skyrocket was configured with a flush cockpit canopy, but visibility from
the cockpit was poor, so it was re-configured with a raised cockpit with
conventional angled windows. This resulted in a greater profile area at the
front of the aircraft, which was balanced by an additional 14 inches (36 cm) of
height added to the vertical stabilizer. Like its predecessor, the D558-1, the
D558-2 was designed so that the forward fuselage, including cockpit, could be
separated from the rest of the aircraft in an emergency. Once the forward
fuselage had decelerated sufficiently, the pilot would then be able to escape
from the cockpit by parachute.
Role
Experimental high-speed research aircraft
Manufacturer
Douglas Aircraft Company
First flight
4 February 1948
Primary user
United States Navy
Number built
3
Developed from
Douglas D-558-1 Skystreak
Douglas pilot John F. Martin made the first flight at Muroc Army Airfield (later
renamed Edwards Air Force Base) in California on 4 February 1948 in an aircraft
equipped only with the jet engine. The goals of the program were to investigate
the characteristics of swept-wing aircraft at transonic and supersonic speeds
with particular attention to pitch-up (un-commanded rotation of the nose of the
aircraft upwards), a problem prevalent in high-speed service aircraft of that
era, particularly at low speeds during takeoff and landing, and in tight turns.
The three aircraft gathered a great deal of data about pitch-up and the coupling
of lateral (yaw) and longitudinal (pitch) motions; wing and tail loads, lift,
drag and buffeting characteristics of swept-wing aircraft at transonic and
supersonic speeds; and the effects of the rocket exhaust plume on lateral
dynamic stability throughout the speed range. (Plume effects were a new
experience for aircraft.) The number three aircraft also gathered information
about the effects of external stores (bomb shapes, drop tanks) upon the
aircraft's behavior in the transonic region (roughly 0.7 to 1.3 times the speed
of sound). In correlation with data from other early transonic research aircraft
such as the XF-92A, this information contributed to solutions to the pitch-up
problem in swept-wing aircraft.
Besides setting several records, the Skyrocket pilots had gathered important
data and understanding about what would and would not work to provide stable,
controlled flight of a swept-wing aircraft in the transonic and supersonic
flight regimes. The data they gathered also helped to enable a better
correlation of wind-tunnel test results with actual flight values, enhancing the
abilities of designers to produce more capable aircraft for the armed services,
especially those with swept wings. Moreover, data on such matters as stability
and control from this and other early research aircraft aided in the design of
the Century Series of fighter aircraft, all of which featured the movable
horizontal stabilizers first employed on the X-1 and D-558 series.
Specifications (D-558-2 Skyrocket)
General characteristics
Crew: one pilot
Length: 42 ft 0 in (12.8 m)
Wingspan: 25 ft 0 in (7.6 m)
Height: 22 ft 8 in (3.8 m)
Empty weight: 9,421 lb (4,273 kg)
Max. takeoff weight: 15,266 lb (6,923 kg)
Performance
Maximum speed: 720 mph, 1,250 mph when air-launched (1,160 km/h, 2,010 km/h when
air-launched)
Stall speed: 160.1 mph (257.7 km/h)
Service ceiling: 16,500 ft (5,030 m)
Rate of climb: 22,400 ft/min, 11,100 ft/min under rocket power only (6,830
m/min., 3,380 m/min under rocket power only)
Thrust/weight (jet): 0.39
*
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