While NASA would likely have chosen liquid boosters had it complete control over the design, the Office of Management and Budget insisted on less expensive solid boosters due to their lower projected development costs.[3]:416–423[7] While a liquid-fueled booster design provided better performance, lower per-flight costs, less environmental impact and less developmental risk, solid boosters were seen as requiring less funding to develop at a time when the Shuttle program had many different elements competing for limited development funds. The final design which was selected was a winged orbiter with three liquid-fueled engines, a large expendable external tank which held liquid propellant for these engines, and two reusable solid rocket boosters.