By Lee Goldberg
What’s at Stake:
NASA investigated multiple launch systems to put a man into Space and ultimately decided to put the Mercury capsule atop derivatives of ballistic missiles. 40 years later, economics and technology evolution allowed the engineers and scientists working on SpaceShipOne, to make a different decision.
The first two crewed Mercury flights were carried on their suborbital trajectories by human-rated derivatives of the Redstone ballistic missile. These rockets were highly-evolved versions of the V2 ballistic weapons originally developed by Wernher von Braun that Germany used to bombard Britain during WWII.
Among the direct similarities between the two rockets was the use of a 75 percent alcohol/25 percent water fuel mixture and liquid oxygen (LOX) as its oxidizer, and a steering mechanism which used a set of carbon vanes placed just below the rocket exhaust. Although the Redstone’s Rocketdyne A-7 motor, and the turbopumps, that fed it were significant improvements on those used by the original V2, their basic concepts and functions were remarkably similar.
To achieve the velocities needed for orbital flights, subsequent missions were flown aboard an Atlas-D rocket, originally created to serve as an intercontinental ballistic delivery vehicle for nuclear weapons. Powered by a pair of Rocketdyne XLR-85 engines burning kerosene and liquid oxygen that produced up to 360,000 pounds of thrust, and an LR-101 sustainer engine, the Atlas used super-thin fuel tanks and other lightweight construction techniques to maximize its payload capacity.