The studies indicated :

• The Saturn S-IC flyback booster would use expendable engines, considered a drawback.
• The new-design pressure fed liquid propellant booster would cost $4.2 billion to develop, plus a recurring cost of $275/kg to orbit.
• Solid boosters would stage at 5800 kph. A solid booster shuttle would have a 2,221,000 gross lift-off weight equipped with 2 x 156 inch diameter solid rocket motors, loaded with 1.25 million kg of propellant and having a 130 second burn time. Lift-off thrust would be 1,332,000 kgf. Development cost would be $ 3.7 billion, and recurring shuttle cost to orbit would be $ 500/kg.