Parametric Cost Analysis of Refueling Options in Cislunar Space

Over the next several years NASA intends to develop and maintain a sustained human
presence in cislunar space and on the surface of the Moon. The sustained lunar presence will
then serve as a steppingstone for human missions to Mars. To propel the spacecraft taking
humans and cargo to and from the lunar surface and to and from Mars will require on the
order of hundreds of tons of propellant. Single-use refueling elements (expendable tankers)
may be more cost-effective for smaller campaigns, but as the propellant demand grows, so does
the potential for a cost benefit from reusable tankers. The cost of two different architectures for
delivering propellant to cislunar space was estimated and compared. The first architecture relies
on expendable tankers for propellant delivery while the second architecture reuses every element,
including launch vehicle stages. The study determined that if the cost of reusing refueling
tankers is consistent with the current state of the art, the expendable refueling architecture is
more cost effective. However, refinements of the methods used to estimate launch and tanker
reuse costs are needed to provide more precise estimates of the breakeven point.