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HOTOL
HOTOL -

Credit: Mark Lindroos. 18,609 bytes. 307 x 190 pixels.



Family: Winged. Country: UK. Status: Development 1985.

Single-stage-to-orbit winged launch vehicle (horizontal takeoff/horizontal landing) using a unique engine design. The RB545 air / liquid hydrogen / liquid oxygen rocket engine was to be developed by Rolls-Royce. HOTOL development was begun in 1982 by a Rolls-Royce / British Aerospace team led by John Scott and Dr Bob Parkinson. The project was reasonably well advanced (engine detailed design and mockup) by the time the British government withdrew further funding in the mid-1980's. HOTOL would have taken off horizontally from a runway, from a purpose made, rocket propelled trolley. It would transition to pure rocket propulsion at Mach 5.0 - Mach 6.0. and ascend to orbit. A moderate re-entry profile would decrease the thermal loading constraints. HOTOL would return via a glide landing, to a landing on gear on a conventional runway.

The HOTOL airframe was derived from conventional vertical takeoff rockets with the engines mounted at the rear of a blunt based fuselage. Since such a vehicle’s empty centre of gravity is dominated by the engine location, the wings and the tank for the dense liquid oxygen also had to be at the rear. The payload bay and hydrogen tankage were placed in a projecting forebody. The resulting configuration suffered from a severe centre of pressure / centre of gravity mismatch during the air breathing ascent. The centre of pressure shifted 10 m forward, due to the wide Mach range, the large fuselage cross section to wing area ratio, and the long overhang of the forward fuselage. Various alterations were made to the design to handle these problems, all of which eroded the payload. Conventional landing gear were replaced by a specially designed takeoff trolley in order to improve the marginal payload fraction. The final design had serious operational disadvantages and a small payload. The only way the designers could continue to claim to put a reasonable payload into orbit was by specifying untried and speculative structural materials.


Specifications

Liftoff Thrust: 321,430 kgf. Total Mass: 250,000 kg. Core Diameter: 7.0 m. Total Length: 75.0 m. Flyaway Unit Cost $: 10.00 million. in 1985 unit dollars.


HOTOL Chronology


- 1982 -

Bibliography:



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Last update 12 March 2001.
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