A dual thrust axis lander for Mars exploration

With NASA's direction set to further explore Mars with both robotic and human exploration, an Entry, Descent and Landing (EDL) vehicle with the ability to place large payloads on the Martian surface is essential. The scheme utilized by Curiosity has limitations. Work being done by Masten along with several NASA centers and other commercial firms on a dual thrust axis lander, known as XEUS, provides the basis for an economical Martian EDL vehicle. The XEUS program was conceived as a result of the Augustine Commission's observation that a lander is not affordable in an effort to produce an affordable lander. The general approach is to add a mission specific kit to an upper stage that includes additional landing thrusters and landing gear to conduct a rocket powered vertical landing while the vehicle is in a horizontal attitude. The addition of aerodynamic structures and thermal protection systems to the mission kit allow aerocapture, entry, descent, and landing on worlds with a significant atmosphere such as Mars. Using the current Centaur used on Atlas V, the planned Advanced Common Evolved Stage (ACES) which is to be used on both Atlas and Delta launch vehicles, or NASA's Cryogenic Propulsion Stage (CPS) for SLS, we found that payloads ranging in size from 1.5mT to 60mT can be landed on Mars and returned to orbit. The use of shared propulsion stages that would be used for launch vehicles, including Centaur, ACES, and SLS CPS allow high mass fraction landers with large payload capability without designing and manufacturing new large vehicles. The large mass fraction reduces the number of launches required and reduces or eliminates the need for additional in-space stages. The large mass fraction also reduces the number of propulsive stages needing to be designed by handling both descent and ascent with a single vehicle. For long term sustainability, the use of a single descent/ascent stage eliminates the clutter of descent stages left on the surface. The large cryogenic propellant tanks ease the aerodynamics and thermal conditions of aerocapture and entry. Landing with the primary vehicle axis in a horizontal attitude, astronaut and equipment access to the Martian surface is made far easier and safer.