Mars Direct: Combining Near-Term Technologies to Achieve a Two-Launch Manned Mars Mission

Abstract

This paper introduces a mission architecture called 'Mars Direct' which brings together several technologies and existing hardware into a novel mission strategy to achieve a highly capable and affordable approach to the Mars and Lunar exploratory objective of the Space Exploration Initiative (SEI). Three innovations working in concept cut the initial mass by a factor of three, greatly expand out ability to explore Mars, and eliminate the need to assemble vehicles in Earth orbit. The first innovation, a hybrid Earth/Mars propellant production process works as follows. An Earth Return Vehicle (ERV), tanks loaded with liquid hydrogen, is sent to Mars. After landing, a 100 kWe nuclear reactor is deployed which powers a propellant processor that combines onboard hydrogen with Mars' atmospheric CO2 to produce methane and water. The water is then electrolized to create oxygen and, in the process, liberates the hydrogen for further processing. Additional oxygen is gained directly by decomposition of Mars' CO2 atmosphere. This second innovation, a hybrid crew transport/habitation method, uses the same habitat for transfer to Mars as well as for the 18 month stay on the surface. The crew return via the previously launched ERV in a modest, lightweight return capsule. This reduces mission mass for two reasons. One, it eliminates the unnecessary mass of two large habitats, one in orbit and one on the surface. And two, it eliminates the need for a trans-Earth injection stage. The third innovation is a launch vehicle optimized for Earth escape. The launch vehicle is a Shuttle Derived Vehicle (SDV) consisting of two solid rocket boosters, a modified external tank, four space shuttle main engines and a large cryogenic upper stage mounted atop the external tank. This vehicle can throw 40 tonnes (40,000 kg) onto a trans-Mars trajectory, which is about the same capability as Saturn-5. Using two such launches, a four person mission can be carried out every twenty-six months with minimal impact on shared Shuttle launch facilities at Kennedy Space Center (KSC). The same launch vehicle, habitat, and upper stage of the ERV can also be used to perform Lunar missions. It is concluded that the Mars Direct architecture offers a cost effective approach to accomplishing the Lunar and Mars goals of the Space Exploration Initiative.