Mission Design of a Two-Person Mars Flyby by 2018 International Student Design Competition Team Mars18 - www.mars18.de Margret Barkmeyer Nils Hoffrogge Ferdinand Leinbach Mirjam Schmidt Winfried Burger Heiko Joos Victor Mosmann Rolf Stierle Felix D¨uver Peter J¨ustel Fabian M¨uller Lukas Teichmann Eduardo Finkenwerder Jochen Keppler Paul Nizenkov Tobias Torgau Dan Fries* Ronja Keuper Duncan Ohno Daniel Wischert Stefan Fuggmann Alexander Kunze Adrian Pfeifle S¨orenHeizmann Jonas Lay Minas Salib Christina Herr Hong Anh Le Marcel Scherrmann University of Stuttgart Table of Contents Page 1 Introduction1 2 Executive Summary2 3 Mission Architecture3 3.1 Trajectory.....................................3 3.2 Launcher Selection & Manifest..........................4 3.3 Reentry......................................7 4 Human Factors 11 4.1 Astronaut Selection................................ 11 4.2 Crew Health.................................... 12 5 Spacecraft Design 15 5.1 Configuration & Structure............................ 15 5.2 Subsystems Design................................ 17 5.3 Scientific Payload................................. 35 5.4 Systems Engineering & Budgets......................... 36 6 Programmatic Issues 38 6.1 Cost........................................ 38 6.2 Roadmap & Schedule............................... 41 6.3 Risk Management................................. 43 7 Conclusion 46 Bibliography 46 *Point of Contact: Dan Fries, [email protected] 1 Introduction To increase the pace in manned Mars exploration, the Mars Society in collaboration with Dennis Tito's Inspiration Mars Initiative called for students around the world to develop a complete mission concept for a manned Mars flyby in 2018. The ultimate goal is not only to complete this very ambitious mission but to spark more interest in comparable missions around the world and further a technological competition to put a human being on Mars on a peaceful level for the greater benefit of mankind. Previous efforts are limited to robotic missions and so far not even a sample return mission has been accomplished. While robotic missions are certainly sufficient to gather simple, pre-determined scientific data, they are not fit to actually expand humanity's sphere of influence. In-situ research and human settlements, however, enable access to resources and hold future potential on a completely different scale. Future problems, like the overpopulation of Earth and lack of essential resources like water, could be tackled right now. Even in the present day, solar system exploration efforts would immediately result in a myriad of scientific and technological developments, employment opportunities and eventually direct financial gain. Furthermore, private space companies and NASA are already working towards heavy-lift launch vehicles, but so far without a clear application. All of the factors mentioned above contribute to the overall result that manned space exploration is not only desirable but also achievable. Mars18 is the student-led team at the University of Stuttgart, Germany, that has taken on the challenge proposed by the Mars Society and Inspiration Mars. The team's goals are the meaningful contribution to the worldwide efforts in space exploration, education of high- potential students in a hands-on project, engagement of public interest in space exploration through cooperation with local media and achieving a high ranking in an internationally acclaimed competition. As a mission like this has never been attempted before, the design presents a special challenge that also sparks creativity in every person involved. The team consists of about 29 students, most of whom are aerospace engineers. But it is obvious that such a project cannot be successful solely through aerospace technology. From the beginning, the team attempted to achieve a multi-disciplinary composition of motivated participants. Mars18 is comprised of students from medical sciences, social sciences, electrical engineering and economics. Moreover, the team managed to gain professional support from the Institute for Space Systems (University of Stuttgart), Astos Solutions, Constellation (distributed platform for aerospace research) and Airbus Defense & Space. The presented work attempts to show how a manned mission to Mars could be executed realistically by 2018. In general, conservative assumptions were preferred over optimistic ones, in both technological and cost issues. Key technologies that would further access to space in general and for this specific mission were identified and a time schedule developed that would allow for their implementation. Although a certain amount of technologies is employed that have to be qualified, this is only done in absolutely necessary cases or because it presents a considerable advantage. Human factors were evaluated and accounted for. Finally a complete cost estimate was conducted. 1 2 Executive Summary During the entire development, the Mars18 team followed four principles: simplicity, safety, low cost and feasibility. To evaluate the amount of development still required an estimated Technology Readiness Level (TRL) is used. Through rigorous optimization and evaluation of available systems it is possible to lower the total mass below 15 t and the low Earth orbit (LEO) mass amounts to ∼ 63 t. A concept is devised that allows to launch the entire mass with only two starts of currently or soon to be available carrier rockets. Trans-Mars injection (TMI) is accomplished via staged propulsion of two modified Delta IV 4-m Second-Stages. The system consists of modified versions of the Enhanced Cygnus (referred to as Cygnus) and the DragonRider (referred to as Dragon). Both modules have already been tested in their basic configuration and are currently under fur- ther development. An important mission like this requires absolute priority among the deep space communication systems on Earth (i.e. Deep Space Network (DSN), ESTRACK). To reduce mass several of the AOCS' thrusters are resisto- jets, using waste products from the life support system. Additionally, a fuel saving model predic- tive control (MPC) algorithm is employed for attitude control. To account for the dangers of radiation exposure outside of the Earth's magnetosphere, a protection scheme is devised that works highly synergetic with the equipment of other subsystems and provides a storm shelter for solar particle events (SPE). The life support system is designed from scratch and follows a virtually close-loop approach. It also introduces two devices that have not been used on previous missions but are able to reduce the required initial mass considerably and increase the synergies with other systems. As the flight trajectory, a free-return option is chosen that requires ∼ 4:8 km/s from a 350 km LEO. At return to Earth's atmosphere, the reentry capsule will have a relative velocity of ∼ 13:8 km/s. The resulting kinetic energy is dissipated during two passes through the atmosphere before descending to the ground. The total mission duration from TMI is ∼ 501 days. The presented concept to deal with human factors handles physical as well as psychological issues in a very isolated and confined space. The well-being is of great importance, since they should perform experiments and document as many things as possible during their journey. Thus, the endeavor will result in the maximum scientific benefit for future missions and possible spin-offs. The total cost of such a mission is estimated using current prices, heritage data and cost models. Thus providing an amount of 4:3 B$ that should be around an upper limit for the presented design. In a simple risk analysis not only the dangers stemming from technological aspects but also programmatic issues are presented and how they might be mitigated. 2 3 Mission Architecture The approach of choosing the most favorable trajectory is presented in this chapter. Further- more, available launcher systems are compared in detail and finally reentry is discussed. 3.1 Trajectory The objective of the trajectory optimization is to find a feasible flyby trajectory to Mars. By solving the Lambert problem, options for such a trajectory are investigated. Therefore, astrodynamics and interplanetary spaceflight have to be considered. 3.1.1 Tools & Boundary Conditions POINT is a Lambert-solver by Astos Solutions. Ephemerides provided by Jet Propulsion Laboratory (JPL) are used to solve the Lambert problem, providing an accurate initial estimation. POINT determines and optimizes trajectories based on constraints and boundary conditions. Possible optimization constraints are minimum flight time as well as low departure and arrival C3 energies. In the following, different trajectories are compared according to mission requirements. GMAT (General Mission Analysis Tool) is an open-source space mission analysis tool provided by NASA. It enables the simulation of gravitational forces of all celestial bodies in the solar system. GMAT is used for verification of the final trajectory. The following boundary conditions constrain the trajectory design. Launchers starting from Cape Canaveral will lift the spacecraft into a circular LEO. The assembly orbit is at an altitude of 400 km and likely to decrease due to atmospheric drag. Therefore, the interplanetary trajectory is set to start at a 350 km altitude with an inclination of 28:5° in the equatorial plane. Additional mission requirements are a flyby altitude of 100 km at Mars to prevent aerodynamic drag and to start the mission in 2018. 3.1.2 Trajectory Trade-Off Multiple