Presidential directive issued on January 14, 2004—called the new Vision for Space Exploration (VSE)—set out goals for future exploration of the solar system using manned spacecraft. Those goals included returning to the moon no later than 2020. Although sufficient capabilities exist to meet the projected needs of both the U.S. commercial sector and the government for launching unmanned payloads into space through 2020, that is not the case for manned space flight.
The proposed return to the moon called for under the VSE and now planned by the National Aeronautics and Space Administration (NASA) could require the development of the capacity to launch payloads weighing more than 100 metric tons (mt). No launch vehicles currently exist that can handle payloads weighing more than about 25 mt. Thus, NASA's plans for manned space flight beyond low earth orbit (LEO) could require a significant increase in launch capability. How that capability could be provided and at what cost is the primary focus of this study.
In considering manned lunar missions, the Congressional Budget Office (CBO) explored alternatives that would use existing launch vehicles; those that would require minor modifications to the designs of existing launchers (termed "close derivatives"); as well as those that would call for major modifications to existing vehicle designs to develop essentially new and much more capable launchers.
All of the alternatives would require multiple launches to assemble in LEO the fuel and hardware needed to fly to the moon. Under the alternatives, CBO estimates, the costs to develop and procure launch vehicles that could support a manned lunar mission in 2018 (under a more ambitious schedule) would range from $26 billion to $38 billion. NASA's projection of funding is $30 billion. The use of less capable existing or closederivative launchers could be less costly but would require up to eight launches to assemble a single lunar mission.
Using the new and more capable launchers considered by CBO would be more costly but could reduce to two the number of launches needed per lunar mission. The greater the number of launches needed to assemble a mission, the greater the complexity of the mission— including both the need to perform on-orbit assembly of the mission's components and the risk that at least one launch would fail, putting the success of the mission at risk. Thus, there is a trade-off between the overall costs of launch vehicles and the risk of mission failure.