The Martin XB-68 was a supersonic medium
tactical bomber with a crew of two that was proposed in 1954 to the
United States Air Force. The project, however, was canceled before any aircraft were built.
Design and development
The
Glenn L. Martin Company
The Glenn L. Martin Company—also known as The Martin Company from 1957-1961—was an American aircraft and aerospace manufacturing company founded by aviation pioneer Glenn L. Martin, and operated between 1917-1961. The Martin Company produc ...
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
The Douglas Aircraft Company was an American aerospace manufacturer based in Southern California. It was founded in 1921 by Donald Wills Douglas Sr. and later merged with McDonnell Aircraft in 1967 to form McDonnell Douglas; it then operated as ...
and
North American Aviation, Inc.
North American Aviation (NAA) was a major American aerospace manufacturer that designed and built several notable aircraft and spacecraft. Its products included: the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the ...
Revised designs were presented again in
1954
Events
January
* January 1 – The Soviet Union ceases to demand war reparations from West Germany.
* January 3 – The Italian broadcaster RAI officially begins transmitting.
* January 7 – Georgetown-IBM experiment: The fir ...
. 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 Sudan, Anglo-Egyptian Condominium ends in Sudan.
* January 8 – Operation Auca: Five U.S. evangelical Christian Missionary, missionaries, Nate Saint, Roger Youderian, Ed McCully, Jim ...
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 wors ...
-
1965
Events January–February
* January 14 – The Prime Minister of Northern Ireland and the Taoiseach of the Republic of Ireland meet for the first time in 43 years.
* January 20
** Lyndon B. Johnson is Second inauguration of Lyndo ...
period.
With a conventional layout that somewhat resembled a scaled-up
Lockheed F-104, the XB-68 was to have been primarily of
steel
Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
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 number
Mach number (M or Ma) (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound.
It is named after the Moravian physicist and philosopher Ernst Mach.
: \mathrm = \frac ...
s. The B-68 would have had stubby diamond-shaped wings and a raked T-tail
empennage. It was intended to be operated at
supersonic
Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
speeds at medium and high altitudes.
The design immediately ran into serious difficulties over the
inertial guidance 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 Cov ...
. 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
The Douglas A-3 Skywarrior is a jet-powered strategic bomber that was developed and produced by the Douglas Aircraft Company. It was designed by Douglas on behalf of the United States Navy, which sought a carrier-capable strategic bomber. Dur ...
, which was designated
B-66 Destroyer. 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 (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