A single shuttle solid rocket booster would be mated with an upper stage in the 100 tonne class. Astronaut Scott Horowitz specifically proposed using the Apollo-era J-2 100 tonne thrust engine for the upper stage (12 remained in storage or museums). ATK Thiokol proposed using several new generation AJ-60/MB-60 27 tonne thrust engines. Advantages of the scheme were said to be use of existing shuttle production lines and facilities; and the man-rated status of the shuttle solid rocket booster.
By 2005 the new NASA Administrator, Griffin, had declared his preference for the ATK Thiokol design as a CEV launch vehicle. ATK Thiokol had settled on use of the J-2S engine in the second stage. The launch system proposed by ATK Thiokol was an in-line, two-stage, inertially guided solid rocket booster (SRB) with a new LOX/LH2 liquid propellant second stage powered by a legacy J-2S engine. A crew module and crew escape module would be utilized for crewed missions; an unmanned version of the launch system was also proposed.
The recoverable solid rocket booster was identical to that used in the Shuttle Space Transportation System. This was the largest solid rocket booster (SRB) to fly and the only one that was human rated. The SRB structure in use for the space shuttle would remain essentially unchanged for this proposed launch system.
The Stage 1 to Stage 2 interstage would be a new development. The aluminum skin and stringer construction interstage extended from the forward skirt of the Stage 1 motor to the aft end of the Stage 2, tapering from a 144 inch to a 231 inch diameter. This interstage was fabricated in two sections: the lower interstage, which remained with Stage 1, and the upper interstage, which would fly with Stage 2. A field joint between the upper and lower sections of the interstage allowed the upper stage stack to be mated to the lower stage, while a linear shaped charge separation system severed the interstage sections prior to Stage 2 ignition. The SRB recovery parachutes would be packaged in the interstage volume.
The second stage design would use a single J-2S engine. The stage would include the associated tankage and feed systems consistent with the requirements for air start and the human-rating requirements imposed upon other human-rated propulsion elements. The J-2S (J-2 Simplified) Engine was originally developed as a replacement for the J-2 Saturn vehicle upper stages, stages 2 and 3 on the Saturn V, and Stage 2 on the Saturn IB. The intent of the design changes was not only to provide performance upgrades to the engine but to greatly simplify the production and operation of the engine. The J-2S engine and components were developed between 1965 and 1972 and the effort was based on experimental engines tested between 1964 and 1968 (the J-2X engine series). The J-2S program consisted of six flight configuration engines tested at both sea level and vacuum conditions in 273 tests for a total operational experience of 30,858 seconds. At the completion of the program the engine was fully developed. The engine was selected based on its maturity, heritage, and performance.
LEO Payload: 18,000 kg (39,000 lb) to a 500 km orbit at 51.60 degrees.
Status: Design 2004.
Gross mass: 700,000 kg (1,540,000 lb).
Payload: 18,000 kg (39,000 lb).
Height: 85.00 m (278.00 ft).
Diameter: 3.77 m (12.36 ft).
Span: 5.00 m (16.40 ft).
Thrust: 10,140.00 kN (2,279,560 lbf).
Apogee: 500 km (310 mi).