Engine Model: MB-35. Manufacturer Name: RS-73. Designer: Rocketdyne. Developed in: 1999. Propellants: Lox/LH2. Thrust(vac): 156.000 kN (35,070 lbf). Isp: 467 sec. Mass Engine: 345 kg (760 lb). Length: 2.21 m (7.25 ft). Chambers: 1. Country: Japan. Status: Design 2004. MHI (Mitsubishi Japan)/Boeing joint project for an engine for Delta IV cryogenic upper stages. Expander bleed, pump-fed. Boeing’s Rocketdyne Division (USA) and Mitsubishi Heavy Industries (Japan) had announced on 14 February 2000 their agreement to jointly design and develop the MB-XX family of high-power cryogenic upper-stage engines for Boeing’s Delta-4 and Japan’s H-2A launch vehicles.