Mars Surface Mobility Proposal Jeremy Chavez Ryan Green William Mullins Rachel Rodriguez ME 4370 Design I October 29, 2001
Background and Problem Statement In the 1960s, the United States was consumed with the desire to be the first country to put a man on the moon. The Russians had started the space race when they launched the first man-made satellite, Sputnik, into Earth orbit. So, in 1969, Neil Armstrong was the first human to walk on the moon. In 1976, the two Viking landers reached the surface of Mars, beginning a detailed exploration of the planet s surface that will be continued for decades to come. While automated rovers will begin the task, the exploration of Mars is the next major endeavor of human space exploration. Human missions will be essential in investigating the possibility of permanent colonization in space. For this reason, the conceptual feasibility of human exploration needs to be evaluated. The economic impact of such an exploration is dependent on the ability to explore vast amounts of terrain and geology without relying on multiple landing craft or multiple missions. For any decent exploration, a human transport rover will have to be developed. This rover must have both short and long-range capabilities and be able to function in a wide variety of missions. A long-range rover must be able to meet the needs of a crew of two for days or even weeks at a time. It must employ a power system that can provide adequate, variable speed for a significant range. The rover must be able to ascend and descend sloped terrain while clearing the often rocky surface. A multipurpose Mars rover will have to overcome many challenges that the Martian environment will impose. With temperatures ranging between -100?C to 10?C, an atmospheric pressure of 6-10 millibars, and dust storms engulfing the planet that can last for weeks at a time, careful attention to details such as material selection, radiation protection, pressurized life support, and suspension stability must be made in the preliminary design. The crew must also be able to return to the base camp in the event of a breakdown. In addition, the rover must be compact and lightweight in order to be launched from Earth.
Objective The objective of this project is to conceptually develop a human transport rover capable of supporting two people during an extensive Mars exploration mission. This project will target four areas of rover development: power system selection, basic structural design, internal habitat layout, and suspension system design. Technical Approach The Mars rover will be designed with a push/pull capability. On short-range missions, each rover can be used independently, while on long-range missions, two rovers can be attached together. Thus, if one rover breaks down, the other rover can bring it back, and using two rovers doubles the crew and load capacity. To facilitate the design process, further research will be conducted into the Mars environment. This will include the radiation level at the surface, soil composition, terrain features, solar flares, and other information as required. The first step in the design process will be choosing the power source for the vehicle. In order for people to explore the surface of Mars, some type of self-renewing power source must be available. Thus, the rover can be recharged at the home base. However, the rover must be able to operate for weeks without returning to the home base. For this reason, nuclear, fuel cell, and electrical systems will all be investigated, and the most suitable system will be chosen. The system must be light in weight and compact but capable of producing the needed power. The vehicle must be able to sustain variable speeds up to 16 km/hr and a range of 120 km, in addition to the other systems on the rover that will require DC power. Once the power system has been chosen, a general structural design will be created. This includes the outer shell, the push/pull connection, and a modular region where different equipment can be attached. Special attention will be given to the material selection process. The over-all weight of the rover is critical in delivering the rover to Mars and in the range, speed, and load capacity when on the surface. Basic structural
analysis will be performed to ensure that the vehicle can support its own weight on earth and have the needed strength on Mars. Once the basic structural design has been determined, the inner habitat can be developed. The rover must be very functional, since it will be employed on a wide range of missions. It must be pressurized so that the crew can remove their spacesuits on longterm expeditions. The inner habitat must meet their human needs, including the necessary food, water, and waste disposal. The habitat must also provide shelter during solar flares. The final stage will be developing the suspension system. This is the most difficult part of the design. The vehicle must be able to traverse very rocky, dusty terrain. This also includes mountains and hills. For this reason, the rover will be designed with a low center of gravity but with the capability to raise itself hydraulically when driving through rocky places. Each wheel and connection should be interchangeable with the others so that they are easy to replace in the event of damage. Some simulation must be done in order to prove that the system is viable. This will be accomplished by modeling the system on computer and performing a dynamic analysis. Organization, People, Capabilities The personnel chosen for this project are four Senior Mechanical Engineering students from Texas Tech University. William Mullins will be leading the selection of the power system. Mr. Mullins has experience in the computer field, which includes maintenance, networking, and trouble-shooting. His areas of interest are in structural design, aerodynamics, thermodynamics, and robotics. Ryan Green will be overseeing the basic structural design. Jeremy Chavez will be responsible for the internal habitat design. Mr. Chavez s experience envolves working with fiber optics and telecommunication equipment. His areas of interest include aerodynamics/aerospace, and analysis through failure/material science. Rachel Rodriguez will be responsible for the suspension system design. Ms. Rodriguez has interned in the design departments of Lockheed Martin Tactical Aircraft
Systems in Ft. Worth, Texas and Raytheon Aircraft Integration Systems in Waco, Texas. She has been involved in nine different research projects with the High Energy Physics Lab, the Wind Engineering Research Center, and the Mechanical Engineering Department at Texas Tech University. This included extensive experience with deploying mobile hurricane towers, driving heavy trailers, and organizing the needed special equipment and personnel for week-long trips into disaster areas. Her interests include dynamics, material science, and wind research. Computer support for this project is available through the Texas Tech University Mechanical Engineering Department Student Computer Lab, which provides access to CAD packages such as IDEAS and Pro-E and the analysis program MatLab. Ms. Rodriguez s personal computer will also provide access to MatLab, AutoCAD, and Pro- E. The use of applicable free-ware software will be investigated during the analysis process. List of Deliverables Since this project is purely conceptual, the result of the design process will be detailed 2D and 3D CAD drawings of the rover, information about the Mars environment, and basic feasibility analysis of the power system, structural design, and suspension system. These will be summarized in a final report and presented at the Mechanical Engineering Department and at NASA. Schedule The project will begin on November 1, 2001 and conclude in April of 2002. The work schedule is shown in Table 1.
Table 1: Project Schedule Month Budget Tasks November Select power system Diagram it with CAD system Approximate calculations of power requirements January Design structural system Perform structural analysis Begin detailed 2-D and 3-D CAD drawings February Design internal habitat Continue detailed CAD drawings March Design Suspension system Model with CAD Test stability with CAD April Final Tasks Compile preliminary reports into final reports Finish all CAD drawings for the report Final presentations Since this project involves only a conceptual design, the budget will be comprised of personnel expenses including salary, fringe benefits, and travel to NASA to present the final design. Table 2 presents the expenses of the project. Table 2: Project Budget (note that these numbers are fictitious, used for class purposes) Salaries and Wages four people @ $25/hr for 10 hours/week for 5 months $21,500 Fringe Benefits 25% of Salaries and Wages $5,375 Travel Expenses van rental $100 2 hotel rooms for 1 night $150 per diem for meals for 1.5 days $45 Total travel $295 Total Direct Costs $27,170 Overhead 100% of direct costs $27,170 Total Project Costs $54,340
References www.nasa.gov http://www.seds.org/nineplanets/nineplanets/mars.html