Encyclopedia Astronautica
HOTOL



hotolpt3.jpg
HOTOL
Credit: Mark Lindroos
This single-stage-to-orbit winged horizontal takeoff/horizontal landing launch vehicle concept was powered by the unique Rolls-Royce RB545 air / liquid hydrogen / liquid oxygen rocket engine. HOTOL development was conducted from 1982 to 1986 before the British government withdrew funding. It was superseded by the Interim HOTOL design which sought to reduce development cost through use of existing Lox/LH2 engines.

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 original HOTOL airframe design 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 was 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.

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Associated Launch Vehicles
  • HOTOL This single-stage-to-orbit winged horizontal takeoff/horizontal landing launch vehicle concept was powered by the unique Rolls-Royce RB545 air / liquid hydrogen / liquid oxygen rocket engine. HOTOL development was conducted from 1982 to 1986 before the British government withdrew funding. It was superseded by the Interim HOTOL design which sought to reduce development cost through use of existing Lox/LH2 engines. More...
  • Interim HOTOL Initiated by a British Aerospace team led by Dr Bob Parkinson in 1991, this was a less ambitious, scaled-back version of the original HOTOL. The single-stage to orbit winged launch vehicle using four Russian rocket engines. It was to have been air-launched from a Ukrainian An-225 Mriya (Dream) aircraft. Interim HOTOL would separate from the carrier aircraft at subsonic speeds, and would then pull up for the ascent to orbit. It would return via a gliding re-entry and landing on gear on a conventional runway. Interim HOTOL suffered from the same aerodynamic design challenges as HOTOL and went through many, many design iterations in the quest for a practical design. More...

HOTOL Chronology


1982 - . LV Family: HOTOL. Launch Vehicle: HOTOL.
  • HOTOL development begun by a Rolls-Royce / British Aerospace team - . Nation: UK. 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, 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.

1991 - . LV Family: HOTOL. Launch Vehicle: Interim HOTOL.
  • Interim HOTOL designed by British Aerospace - . Nation: UK. Summary: This was a less ambitious, scaled-back version of the original HOTOL. The single-stage to orbit winged launch vehicle using four Russian rocket engines. It was to have been air-launched from a Ukrainian An-225 aircraft..

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