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ppt on space elevators by akansha vohra


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ppt on space elevators by akansha vohra

  1. 1. SPACE ELEVATORS Space transportation system Made by: Akansha vohra Mechanical engineering 3rd year
  2. 2. Contents • • • • • • • • Introduction History Importance Working Components Challenges and solution Application Future
  3. 3. ABOUT THE CONCEPT • Space elevators are incredibly tall theoretical structures that stretch beyond the earth’s atmosphere to transport satellites and shuttles into outer space without the cost and environmental impact of rocket fueled launches
  4. 4. PAST OF SPACE ELEVATORS 1960: Artsutanov, a Russian scientist first suggests the concept in a journal 1966-1975: In 1966, Isaacs, Vine, Bradner and Bachus,reinvented the concept, naming it a "Sky-Hook," and published their analysis in the journal Science calculating specifics of what would be required 1979: Authur Clarke, in Fountains of Paradise describes the concept 1999: NASA holds first workshop on space elevators after the discovery of carbon nanotubes. 2001: Bradley Edwards receives NAIC funding for Phase I space elevator mock-up 2005: LiftPort Group announced that it will be building a carbon nanotube manufacturing plant in Millville, New Jersey, 2011: Google was revealed to be working on plans for a space elevator at its secretive Google X Lab. 2006 LiftPort Group announced that they had tested a mile of "space-elevator tether" made of carbon-fiber composite strings and fiberglass tape measuring 5 cm (2 in) wide and 1 mm (approx. 13 sheets of paper) thick, lifted with balloons 2012: Obayashi Corporation announced that by 2050 it could build a space elevator using carbon nanotube technology
  5. 5. The Space Elevator in Science Fiction
  6. 6. Why build it ? CURRENT Cost of a launch $10,000 per pound ($22,000 per kg) Huge vibrations produced and rocket fuel and hardware required which can’t be reused . Riding on a continuous and giant explosion is extraordinarily dangerous, as is re-entry (Challenger, Columbia) ELEVATOR Cost of launch $250 per pound ($660 per kg). Less vibrations produced and less hardware required and can be used almost every day for space travel. Safe access to space - no explosive propellants or dangerous launch or re-entry forces.
  7. 7. How could it be done? • A space elevator made of ribbon anchored to an offshore sea platform • Ribbon would stretch to a small counterweight approximately 62,000 miles (100,000 km) into space due to rotation of earth about its own axis • Mechanical lifters attached to the ribbon would then climb the ribbon, carrying cargo and humans into space using different mechanisms.
  8. 8. Main Components The Ribbon The Anchors The Climbers The Power
  9. 9. Ribbon (tether) • • • • • • It is a light, flexible, ultra strong metal that robots can grip with their climbing treads. It act as a guide rail for the climber It is a long ribbon of carbon nanotubes that would be wound into a spool that would be launched into the orbit. When the spacecraft carrying the spool reaches a certain altitude, perhaps Low Earth Orbit, it would begin unspooling, lowering the ribbon back to Earth. At the same time, the spool would continue moving to a higher altitude. When the ribbon is lowered into Earth's atmosphere, it would be caught and then lowered and anchored to a mobile platform in the ocean. The cable must be made of a material with a large tensile strength/density ratio
  10. 10. Why Carbon nanotubes? • Carbon nanotubes are extremely tiny rolled-up, three dimensional carbon tubes, made of a hexagonal graphite lattice . • They are at least 1000 times stronger than steel rods of the same size and are one-sixth the weight of steel • They are as flexible as steel. • The Young’s modulus has been computed to be on the order of 1.2 Terra Pascal which is 6.25 times that of steel • It can be thought as a sheet of graphite rolled into cylinder. • They are categorized as single and multi walled tubes
  11. 11. Growing CNTs
  12. 12. Making Ribbon
  13. 13. Ribbon
  14. 14. Anchor  Anchor station is a mobile, ocean-going platform identical to ones used in oil drilling  Anchor is located in eastern equatorial pacific  Weather and mobility are primary factors
  15. 15. Climbers  Climbers built with current satellite technology  Drive system built with DC electric motors  Photovoltaic array (GaAs or Si) receives power from Earth  7-ton climbers carry 13-ton payloads  Climbers ascend at 200 km/hr  8 day trip from Earth to geosynchronous altitude  Initial 200 climbers
  16. 16. Power Beaming Propulsion • Various methods proposed to get the energy to the climber are: 1. Transfer the energy to the climber through wireless energy transfer while it is climbing. 2. Transfer the energy to the climber through some material structure 3. Store the energy in the climber before it starts – requires an extremely high specific energy such as nuclear energy. 4. Solar power – power compared to the weight of panels limits the speed of climb. WIRELESS ENERGY SYSTEM INVOLVES: • The lifter will be powered by a free-electron laser system located on or near the anchor station • It requires physical installations at the transmitting and receiving points, and nothing in between. • The receiver can be moved to a different location, closer or further away, without changing the cost of the system
  17. 17. Continued… • The laser will beam 2.4 megawatts of energy to photovoltaic cells, perhaps made of Gallium Arsenide (GaAs) attached to the lifter, • It will then convert that energy to electricity to be used by conventional, niobium-magnet DC electric motors • In 2009, NASA awarded $900,000 to Laser Motive for their successful demonstration of "wireless power transmission" for space elevator
  18. 18. Challenges and solutions  Induced Currents: milliwatts and not a problem  Induced oscillations: 7 hour natural frequency couples poorly with moon and sun, active damping with anchor  Radiation: carbon fiber composites good for 1000 years in Earth orbit (LDEF)  Atomic oxygen: <25 micron Nickel coating between 60 and 800 km (LDEF)  Environmental Impact: Ionosphere discharging not an issue  Malfunctioning climbers: up to 3000 km reel in the cable, above 2600 km send up an empty climber to retrieve the first  Lightning, wind, clouds: avoid through proper anchor location selection  Meteors: ribbon design allows for 200 year probabilitybased life  LEOs: active avoidance requires movement every 14 hours on average to avoid debris down to 1 cm  Health hazards: under investigation but initial tests indicate minimal problem  Damaged or severed ribbons: collatoral damage is minimal due to mass and distribution
  19. 19. Technical Budget Component Launch costs to GEO Ribbon production Spacecraft Climbers Power beaming stations Anchor station Tracking facility Other Contingency (30%) TOTAL Cost Estimate (US$) 1.0B 400M 500M 370M 1.5B 600M 500M 430M 1.6B ~6.9B Costs are based on operational systems or detailed engineering studies. Additional expenses will be incurred on legal and regulatory issues. Total construction should be around US$10B. Recommend construction of a second system for redundancy: US$3B
  20. 20. Applications  Solar power satellites - economical, clean power for use on Earth  Solar System Exploration colonization and full development of the moon, Mars and Earth orbit  Telecommunications - enables extremely high performance systems
  21. 21. Next Steps • Material development efforts are underway by private industry • Space elevator climber competition will demonstrate basic concept • Engineering development centers in the U.S., Spain and Netherlands are under development • Technical conferences continuing • Greater public awareness • Increased financial support being sought • Use superconducting property of nanotube ribbon • Maglev type ascension
  22. 22. Bibliography • • • • • • • • Various science blogs Online newsletters and journals
  23. 23. QUERIES??
  24. 24. THANK YOU!!