Mars ascent vehicle sizing, habitability, and commonality in NASA's Evolvable Mars Campaign

The Mars Ascent Vehicle (MAV) is the largest indivisible payload and has the largest “gear ratio” in NASA's Evolvable Mars Campaign (EMC) architecture. For this reason, the mass and related volume of the MAV cabin drives requirements for Mars Surface In-Situ Resource Utilization generators to manufacture propellants, which: drives the surface power needs, sets the Lander payload size, drives the in-space transportation architecture, and drives the number of launches and time required to land humans on Mars' surface. Some of the architectures currently under consideration in the EMC use a chemical/solar electric propulsion hybrid that inserts into a 5 sol orbit and may require that the crew spend several days in the MAV before a rendezvous with the Mars transit vehicle. There have been no human-in-the-loop (HITL) evaluations to generate the data necessary to inform decisions on the required size of the MAV. These data are critical to begin to close the various EMC architectures. The common cabin concept consists of a core cabin with ECLSS, power, thermal and GNC systems that can be coupled to various mobility systems resulting in use of the core cabin design within a lander cabin, MAV - an in-space taxi between locations in the Mars system, as a Mars moons exploration vehicle, and a Mars surface rover. The common cabin approach could be facilitated through a standard interface design that allows for attachment of the different mobility systems. The interior of the cabin would also be outfitted differently based on the mission of the particular vehicle. The focus of the project summarized here is to determine the size of the smallest viable MAV from a sizing and habitability perspective. Multiple options were considered, two of which were studied in greater depth; one that provides maximum commonality with other cabins needed across the EMC and the other being a unique minimalist cabin. To enable the sizing and habitability assessments, the project completed analysis tasks including generation of functional requirements, development of mission timelines for all phases of MAV operations (from launch to berthing with a transit habitat), definition of required subsystems, computer aided design modeling of potential cabin layouts, and development of preliminary mass equipment lists. A maximum commonality cabin was evaluated with a 4-person crew executing all phases of the mission timeline. Additionally a minimalist cabin design was subjectively evaluated using computer generated models of vehicle layout and design. The results of the test findings and analysis are described in this paper. The results suggested that the volume and mass of the common cabin and the minimalist cabins were nearly identical. The benefits of the common cabin also include the potential use as a habitable airlock/node as part of a Cislunar habitat system, buying down risk and gaining flight experience with this Mars-forward habitation element.