The Martin XB-68 was a supersonic medium
tactical bomber
Tactical bombing is aerial bombing aimed at targets of immediate military value, such as combatants, military installations, or military equipment. This is in contrast to strategic bombing, or attacking enemy cities and factories to cripple fut ...
with a crew of two that was proposed in 1954 to the
United States Air Force
The United States Air Force (USAF) is the Aerial warfare, air military branch, service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part ...
. The project, however, was canceled before any aircraft were built.
Design and development
The
Glenn L. Martin Company submitted design studies in response to the Weapon System 302A requirement in
1952
Events January–February
* January 26 – Black Saturday in Egypt: Rioters burn Cairo's central business district, targeting British and upper-class Egyptian businesses.
* February 6
** Princess Elizabeth, Duchess of Edinburgh, becomes m ...
in competition with proposals from
Douglas Aircraft Company and
North American Aviation, Inc. Revised designs were presented again in
1954. The
Boeing Airplane Company
The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and product ...
also submitted a design after the competition date had passed and was automatically rejected. The Martin 316 was declared the winner in
1956
Events
January
* January 1 – The Anglo-Egyptian Condominium ends in Sudan.
* January 8 – Operation Auca: Five U.S. evangelical Christian missionaries, Nate Saint, Roger Youderian, Ed McCully, Jim Elliot and Pete Fleming, ar ...
and received the designation XB-68. Deployment was projected for the
1962
Events January
* January 1 – Western Samoa becomes independent from New Zealand.
* January 3 – Pope John XXIII excommunicates Fidel Castro for preaching communism.
* January 8 – Harmelen train disaster: 93 die in the wor ...
-
1965 period.
With a conventional layout that somewhat resembled a scaled-up
Lockheed F-104
The Lockheed F-104 Starfighter is an American single-engine, supersonic air superiority fighter which was extensively deployed as a fighter-bomber during the Cold War. Created as a day fighter by Lockheed as one of the "Century Series" of fig ...
, the XB-68 was to have been primarily of
steel construction, with the crew of a pilot-radio operator and navigator-bombardier defense systems operator in a pressurized compartment, to be cooled by filtered bleed-air from the engines, and a refrigeration unit for evaporative cooling at high
Mach numbers. The B-68 would have had stubby diamond-shaped wings and a raked T-tail
empennage
The empennage ( or ), also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow.Crane, Dale: ''Dictionary of Aeronautical Terms, third e ...
. It was intended to be operated at
supersonic speeds at medium and high altitudes.
The design immediately ran into serious difficulties over the
inertial guidance
An inertial navigation system (INS) is a navigation device that uses motion sensors ( accelerometers), rotation sensors ( gyroscopes) and a computer to continuously calculate by dead reckoning the position, the orientation, and the velocity ...
bombing and navigation system, which, had the bomber been approved for production, would have pushed deployment back to at least
1963
Events January
* January 1 – Bogle–Chandler case: Commonwealth Scientific and Industrial Research Organisation scientist Dr. Gilbert Bogle and Mrs. Margaret Chandler are found dead (presumed poisoned), in bushland near the Lane Co ...
. The problems were rendered moot when Air Force headquarters cancelled the project in 1957, citing stringent budget limitations and higher priorities for other weapon systems. Recognizing that the medium tactical bomber design was still years away, plans were carried forward instead to continue using an Air Force version of the Navy's
Douglas A3D, which was designated
B-66 Destroyer
The Douglas B-66 Destroyer is a light bomber that was designed and produced by the American aviation manufacturer Douglas Aircraft Company.
The B-66 was developed for the United States Air Force (USAF) and is heavily based upon the United S ...
. Two planned XB-68 prototypes and one static test model were cancelled, and none were built.
The chosen power plant was two
Pratt & Whitney J75
The Pratt & Whitney J75 (civilian designation: JT4A) is an axial-flow turbojet engine first flown in 1955. A two-spool design in the 17,000 lbf (76 kN) thrust class, the J75 was essentially the bigger brother of the Pratt & Whitney J57 ...
(JT4B-21) axial-flow turbojets of static sea level thrust each with afterburner, providing a maximum speed of at altitude at maximum power and a combat speed of at altitude at maximum power. Combat range was planned for with payload at average speed in 4.15 hours.
Specifications (as designed)
See also
References
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External links
Aerospace Review: ''Martin XB-68''Defense Talk: ''XB-68''The Unwanted Blog: ''Martin XB-68, Martin Model 316, Model 302 drawings''
{{USAF system codes
Martin aircraft
Twinjets
Cancelled military aircraft projects of the United States