Although the contract does not give SpaceX a set number of launches, the launch provider expects to use its planned Falcon 9 rocket more often than its smaller Falcon 1 booster. Falcon 9 can deliver 11,300kg (24,800lb) to a 200km (124 miles) low-Earth orbit compared with the 1,000kg to 185km range of the Falcon 1.
SpaceX chief executive Elon Musk told Flight that if a payload was far smaller than Falcon 9's capability he would still use that launcher as "it is like the trucks on the road. They are not completely full and it is more cost efficient to have only a few sizes of truck."
He says that a $1 billion launch services contract could include NASA's ongoing commercial International Space Station resupply procurement, on which SpaceX is bidding. The contractor selection is on 28 November. Musk envisages NASA buying his company's cargo-variant Dragon capsules as payload and sourcing its Falcon 9 booster through the contract.
Falcon 1 and Falcon 9 use the Merlin 1C engine for the first stage. SpaceX will simultaneously fire a cluster of five Merlin 1Cs in May and then in July or August the final Falcon 9 configuration of nine. The next Falcon 1 launch, and its first use of the Merlin 1C, is in June, delayed from April after the US Air Force payload did not arrive in time.