A-7 (rocket engine)

Mercury-Redstone Launch Vehicle

Mercury-Redstone 2 launch carrying Ham (chimpanzee), Jan 31, 1961
Function	Human-rated sub-orbital launch vehicle
Manufacturer	Chrysler Corporation
Country of origin	United States
Size
Height	25.41 m (83.38 ft)
Diameter	1.78 m (5.83 ft)
Mass	30,000 kg (66,000 lb)
Stages	1
Capacity
Payload to sub-orbital trajectory	1,800 kg (4,000 lb)
Launch history
Status	Retired
Launch sites	Launch Complex 5, Cape Canaveral, Florida
Total launches	6
Successes	5
Failures	1
First flight	November 21, 1960
Last flight	July 21, 1961
Notable payloads	Mercury spacecraft
Single stage
Engines	1 Rocketdyne A-7
Thrust	350 kN (78,000 lbf)
Specific impulse	215 sec
Burn time	143.5 seconds
Fuel	LOX/ethyl alcohol

The Mercury-Redstone Launch Vehicle, designed for NASA's Project Mercury, was the first American manned space booster. It was used for six sub-orbital Mercury flights from 1960–61; culminating with the launch of the first, and 11 weeks later, the second American (and the second and third humans) in space.

A member of the Redstone rocket family, it was derived from the U.S. Army's Redstone ballistic missile and the first stage of the related Jupiter-C launch vehicle; but to human-rate it, the structure and systems were modified to improve safety and reliability.

The four subsequent Mercury human spaceflights used the more powerful Atlas booster to enter low Earth orbit.

NASA chose the U.S. Army's Redstone liquid-fueled ballistic missile for its suborbital flights as it was the oldest one in the US fleet, having been active since 1953 and had many successful test flights.

The standard military Redstone lacked sufficient thrust to lift a Mercury capsule into the ballistic suborbital trajectory needed for the project; however, the first stage of the Jupiter-C, which was a modified Redstone with lengthened tanks, could carry enough propellant to reach the desired trajectory. Therefore, this Jupiter-C first stage was used as the starting point for the Mercury-Redstone design. The Jupiter-C's engine, however, was being phased out by the Army, so to avoid potential complications such as parts shortages or design revisions, the Mercury-Redstone designers chose the Rocketdyne A-7 engine used on the latest military Redstones. Hans Paul and William Davidson, propulsion engineers at ABMA, were assigned the task of modifying the A-7 to be safe and reliable for manned flights.