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MARC-60
Country of origin	Japan, United States of America
Date	1999
Designer	Aerojet Rocketdyne, MHI
Application	Upper stage engine
Associated LV	Atlas V, Delta IV, H-IIA, SLS EUS
Status	Development halted
Liquid-fuel engine
Propellant	LOX/LH2
Mixture ratio	5.40 ± 2%
Cycle	Open expander cycle
Performance
Thrust, vacuum	266.7 kN (60,000 lbf)
Throttle range	75–100% ± 3%
Specific impulse, vacuum	462 s (4.53 km/s)
Burn time	800 s
Restarts	5 (7 after delivery)
Gimbal range	5°
Dimensions
Length	3.3 m (10.8 ft)
Dry mass	591 kg (1,302 lb)

The MARC-60 (Mitsubishi Aerojet Rocketdyne Collaboration), also known as MB-60, MB-XX, and RS-73, is a liquid-fuel cryogenic rocket engine designed as a collaborative effort by Japan's Mitsubishi Heavy Industries and US' Aerojet Rocketdyne.^[1]^[2] The engine burns cryogenic liquid oxygen and liquid hydrogen in an open expander cycle, driving the turbopumps with waste heat from the main combustion process.^[1]

Description

The MB-XX program shared the development duties of the engines between Boeing's Rocketdyne division (now Aerojet Rocketdyne) and the Japanese Mitsubishi Heavy Industries. Under the agreement, Boeing develops the LOX and LH₂ turbopumps and the nozzle, while MHI develops the thrust chamber assembly (TCA), control systems, gimbal bearing, heat exchanger, and ducts. The TCA of the engine consists of the main combustion chamber, the regeneratively cooled portion of the nozzle, the injector, and the ignition system.^[2]

Under the MB-XX program two engines were developed: the MARC-60 (MB-60) and the MB-35. Please note that the below table uses specifications as listed in 2003, and the MARC-60 engine has since then evolved.

Comparison between the MB-60 and MB-35 in 2003^[2]
	MB-35	MB-60 (outdated)
Engine cycle	Open expander (bleed)	Open expander (bleed)
Propellants	LOX/LH₂	LOX/LH₂
Vacuum thrust	156 kN (35,000 lbf)	267 kN (60,000 lbf)
Vacuum specific impulse	468 s (4.59 km/s)	467 s (4.58 km/s)
Chamber pressure	103 bar (1500 psia)	134 bar (1950 psia)
Mixture ratio (O/F)	5.8	5.8
Weight	345 kg (760 lb)	590 kg (1300 lb)
Area ratio	313	300
Length stowed/extended^[a]	2.21 m/3.05 m (87 in/120 in)	3.3 m (130 in)
Restarts	Multiple	Multiple

^ The MB-35 features a stowed nozzle extension that is extended during flight, similar to the one found on the RL10^[2]

History

The MARC-60's (then MB-60) development program was announced on 14 February 2000 by Boeing's Rocketdyne division and Japan's Mitsubishi Heavy Industries, as a part of the MB-XX family of cryogenic upper stage rocket engines.^[1] The aim of the MB-XX program was to develop an engine with "robust operating margins, high reliability, increased thrust, and high specific impulse at an affordable cost".^[2] The MB-XX family of engines was intended to be used on new or upgraded upper stages of Boeing's Delta IV and MHI's H-IIA families of launch vehicles. Potential applications also included Lockheed Martin's Atlas V.^[2] Both Delta IV and Atlas V are now operated by United Launch Alliance.

Development of the MB-XX family of engines was started in early 1999.^[2] From 2000 to 2001, market forces drove the focus of the MB-XX program from the 267 kN (60,000 lbf) MB-60 to the 156 kN (35,000 lbf) MB-35. The MB-35 was not a new design, instead the existing MB-60 design was tuned to operate at the lower thrust level.^[3] The MB-35 was designed to be a modern, drop-in replacement for the Aerojet Rocketdyne RL10.^[2]

Component-level testing of the MB-XX demonstrator was completed in 2004, and a system-level demonstrator engine was successfully hot-fired in September 2005.^[4]

In 2013, NASA was evaluating MARC-60 as the engine of choice for the Space Launch System's Exploration Upper Stage (EUS). The study explored the possibility of utilizing two MARC-60 engines in place of four RL10 engines, as well as the possibility of the stage using a single J-2X engine.^[5] Under the plan, the engine's control unit would have been provided by NASA.^[6] The proposal also resulted in the engine being renamed to MARC-60, as Rocketdyne had changed hands multiple times after the MB-60's (Mitsubishi Boeing-Rocketdyne) inception in 1999.^[7] In 2016 NASA announced that the EUS would be powered by four RL10C-3 engines, dropping both MARC-60 and J-2X.^[8]

References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j "MB-60". www.astronautix.com. Archived from the original on August 20, 2016. Retrieved 2021-03-29.
^ ^a ^b ^c ^d ^e ^f ^g ^h Sack, William; Watanabe, Julie; Atsumi, Masahiro; Nakanishi, Hidemasa (2003-07-20). "Development Progress of MB-XX Cryogenic Upper Stage Rocket Engine". 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit. Joint Propulsion Conferences. Huntsville, Alabama: American Institute of Aeronautics and Astronautics. doi:10.2514/6.2003-4486. ISBN 978-1-62410-098-7.
^ Sack, William F. et al. “The MB-60 Cryogenic Upper Stage Engine - A World Class Propulsion System.” (2009).
^ "Mitsubishi Heavy Industries, Ltd. Global Website | MB-XX". Mitsubishi Heavy Industries, Ltd. Archived from the original on 25 January 2021. Retrieved 2021-03-30.
^ Gebhardt, Chris (2013-11-14). "SLS upper stage proposals reveal increasing payload-to-destination options". NASASpaceFlight.com. Retrieved 2021-03-29.
^ "MB-60 JAXA 60,000 lbf thrust in-space engine for NASA SLS". forum.nasaspaceflight.com. Retrieved 2021-03-29.
^ Greene, William D.; Devine, M. K. (8 August 2013). "NASA Technical Reports Server (NTRS)". ntrs.nasa.gov. Retrieved 2021-03-29.
^ Mohon, Lee (2016-10-21). "Proven Engine Packs Big, In-Space Punch for NASA's SLS Rocket". NASA. Retrieved 2021-03-29.