The United States has set an ambitious goal of sending a manned mission to Mars during the first half of this century. This will likely mean several more trips to the moon, something we haven’t done in nearly 50 years. Combine that with other potential space missions, and logistics will be a big issue. Koki Ho, an assistant professor of aerospace engineering at the University of Illinois at Urbana-Champaign, and his team have been exploring how these missions can be completed efficiently.