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.

Launch Price $: 110.000 million in 1985 dollars.

Stage Data - Interim HOTOL

• Stage 0. 1 x An-225. Gross Mass: 600,000 kg (1,320,000 lb). Empty Mass: 216,000 kg (476,000 lb). Thrust (vac): 1,387.072 kN (311,826 lbf). Isp: 9,000 sec. Burn time: 3,375 sec. Isp(sl): 8,000 sec. Diameter: 18.07 m (59.28 ft). Span: 88.40 m (290.00 ft). Length: 84.00 m (275.00 ft). Propellants: Air/Kerosene. No Engines: 6. Engine: D-18T. Status: Out of Production. Comments: Antonov cargo aircraft swept wing. Release conditions: Piggy-back, 275,000 kg, 38.0 m length x 24.0 m wingspan, 900 kph at 9,500 m altitude. Effective velocity gain compared to vertical launch 270 m/s.

• Stage 1. 1 x Interim HOTOL. Gross Mass: 250,000 kg (550,000 lb). Empty Mass: 33,100 kg (72,900 lb). Thrust (vac): 7,840.000 kN (1,762,500 lbf). Isp: 455 sec. Burn time: 122 sec. Isp(sl): 352 sec. Diameter: 10.00 m (32.00 ft). Span: 21.60 m (70.80 ft). Length: 36.45 m (119.58 ft). Propellants: Lox/LH2. No Engines: 4. Engine: RD-0120. Other designations: Interim HOTOL. Status: Study 1990.