1. Going Up: Modes of Space Travel Objective: Determine and describe which mode of space travel NASA should invest in, based on the cost efficiency, safety and frequency of flight for leaving and returning to the surface of the earth. Background In 1895, a Russian scientist named Konstantine Tsiolkovsky formulated an idea of a tower that reached into space to an altitude of about 35,800 km. He proposed that a sort of a celestial castle would be extended into this orbit by the tower and from this celestial castle, objects could be launched into deep space without the need for a rocket that consumes much fuel. Today, we take his idea a step further by extending not a tower, but a tether from a counterweight to an anchor on the surface. Sponsors: National Aeronautics and Space Administration (NASA) NASA Goddard Space Flight Center (GSFC) NASA Goddard Institute for Space Studies (GISS) NASA New York City Research Initiative (NYCRI) Stevens Institute of Technology (SIT) Contributors: Dr. Siva Thangam, PI Prof. Joseph Miles, PI William Carroll, HST Younus Ahmed, UG Vanshil Shah, HSS Abstract With President Obama’s initiative for space travel, research for new technologies can be pursued. The mode of space travel that will be chosen has to be configured to make space travel more frequent, less costly, and more efficient by implementing reusable resources. Modes of travel thus far have incurred payments of billions of dollars, with the Apollo Program costing $145 billion and the Space shuttle program costing $173 billion. New innovations in space travel will allow NASA to reach its full potential in the near future with programs that are recyclable, incurring less cost, and rendering greater efficiency. In addition, theses programs will foster deep space explorations to the moon, Mars and beyond, reinvigorating the amazing space age. Space Travel Alternate Design Matrix Space ElevatorSpace ShuttleRocketConstellation CriteriaWeightScore Weighted ScoreScore Weighted ScoreScore Weighted ScoreScore Weighted Score R&D Cost151 5755 115 Operational Cost2041003752502 Frequency of travel155100240120360 Duration of travel101155755 460 Mass204802402 2 Fuel/Energy2051003603 3 Total Percentage100 410 365 320 285 Elevator Tether Alternate Design Matrix Multi-walled carbon nanotubes MWNTM5 Fiber Single Wall carbon nanotubesSWNTSpectra-2000KevlarCarbon Fiber CriteriaWeightScore Weighted ScoreScore Weighted ScoreScore Weighted ScoreScore Weighted ScoreScore Weighted ScoreScore Weighted Score R&D Cost151 4601154605755 Tensile Strength/Density25515039041202602 390 Radiation15240510024051005 120 Mass15510048051005 5 5 Diameter15575345575345230115 Conductivity15575460575460230575 Total Percentage100 455 435 425 395 375 Climber Payload for first trip would be around 15 tons, and increase slowly to carry more materials for future trips to various destinations such as the moon, asteroids and Mars. Length of trip to the counterweight is 186 hours or about 7.8 days at 120miles per hour climbing velocity. Human capacity is 3 to 4 personnel. Life support systems as in the counterweight depending upon the type of cargo. Propelled by magnetic levitation and electric motors. - Magnetic Levitation prevents contact between the climber and the tether minimizing friction. - Utilize direction of current to elicit magnetic force upward. - Electric motors for initial acceleration. Powered by lasers from the base and the counterweight that is received by solar panels on the climber. Counterweight Orbit distance of the counterweight is 35,786 km or 22,236 miles, also known as the geosynchronous orbit region. Design similar to the International Space Station, having separate wings for different countries containing labs and stations for research as well as sustenance. Proposed mass above 300 tons, dependent on the cross sectional area of the carbon nanotubes of the tether. Human capacity of 4-5 people. Powered by wings of solar panels. Can be used as a launch site for future extraterrestrial missions, or deep space missions. Life support systems using current technology to remove carbon dioxide, produce oxygen and water, and introduce aeroponics to grow food. Laser beams from the counterweight, provide power to the climber above the stratosphere where there is little or no atmospheric interference. Safety Possible Problems: Tether tears, minor or major Power outage Terrorism Space debris, micrometeoroids Harmful Radiation Tether tears can be minimized through maintenance, but a backup system of parachutes at lower altitudes will allow a capsule to be released from the climber so the payload and the passengers can return to the surface safely. Power outages can be handled by backup batteries that can be on the counterweight, base and the climber. The probability of a micrometeoroid hitting a space station at GEO is 1/1230 or 0.08%, and since CNT’s are much smaller, the percentage is smaller by at least a factor of 1000. Radiation can be shielded as on the International Space Station, using polyethylene shields. How It Works Tether(cable) attached from a counterweight in geosynchronous (GEO) orbit at a distance of 35,786 km to an anchor(base) on the surface of the Earth. Centrifugal force on the counterweight caused by the Earth’s angular velocity maintains a tension in the tether. Rigidity resulting from tension in the tether allows for robotic climbers to ascend to the counterweight. The counterweight’s location in geosynchronous orbit relieves additional tension from the tether since the tether will not have to pull on the counterweight to keep it at its constant position in orbit above the base. Base Located off the coast of an uninhabited US territory named Baker Island because of its constant wind and sunshine with very little rainfall. The base will be fortified with thick layers of reinforced steel to prevent any breakage from large amounts of stress created by the tension from the tether. A control station will monitor the environment of the space elevator for any danger and take any necessary action. The tether will be wrapped around a wheel at the base to distribute tension throughout the system. A laser will be located on the top of the base with the intention of shining approximately 1000 kW of power to the robotic climber. Inside the base will be a generator that produces electricity to the highly conductive carbon nanotubes of the tether. Utilizes Solar and Tidal energy to power itself as well as the climber. Conclusion Through thorough analysis of the different modes of space travel, the one chosen as the most cost efficient and energy saving is the space elevator. The space elevator will first need the counterweight launched and then the tether, composed of multi-walled carbon nanotubes lowered from the counterweight to the base, where it will be attached. The counterweight will be launched similarly to the International Space Station, being built part by part in space, and the tether will be descended once construction of the counterweight is complete. In addition, the counterweight can serve as a launch site for rockets to the moon, asteroids or Mars. The tangential velocity at the counterweight is 1.91 miles per second, which is enough to give the launch vehicle a sufficient starting velocity to reach its destinations using less fuel. Tether Materials Materials Compared: Spectra 2000, M5 Fibers,Carbon Fibers, Kevlar, and Carbon Nanotubes Spectra 2000: A high strength high molecular weight polyethylene fiber. M5 fiber: The strongest fiber with a high tensile strength. Carbon Fiber: A strong light fiber that is 80% carbon. Kevlar: A strong fiber used for purposes of armor and sports equipment. Multi Walled Carbon Nanotubes (MWNT) High Tensile Strength to Density Ratio. Stronger than SWNT. Single Walled Carbon Nanotubes(SWNT) High Tensile Strength to Density ratio. Theoretical Limit is 30,000kg/mm 2. Low density and high conductivity.