SPACE ELEVATOR

SPACE ELEVATOR: A NEW WAY TO REACH THE STARS The Space Elevator is a cable-like tool which could connect the Earth with a fixed structure in outer space. It would provide a permanent link between Earth and outer space. http://www.enterprisemission.com/

The Space Elevator in Science Fiction

Properties Of Carbon Nanotubes Strong – 200 times stronger than steel. – the first synthetic material to have greater strength than spider silk. Light – 1 square kilometre = 30kg Flexible – Compared to most materials. Heat resistant – resists burning like a metal. Nanotube image from http://en.wikipedia.org/wiki/Image:Eight_Allotropes_of_Carbon.png, GNU free documentation license, courtesy of Michael Strock http://en.wikipedia.org/wiki/User:Mstroeck Reference for weight info: K. Banerjee and N. Srivastava, "Are Carbon Nanotubes the future of VLSI Interconnections?", ACM Design Automation Conference, 2006, pp. 809-814.

Ribbon Design The final ribbon is one-meter wide and composed of parallel high-strength fibers Interconnects maintain structure and allow the ribbon to survive small impacts Initial, low-strength ribbon segments have been built and tested

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

Power Beaming Power is sent to deployment spacecraft and climbers by laser Solid-state disk laser produces kWs of power and being developed for MWatts Mirror is the same design as conventional astronomical telescopes (Hobby-Eberly, Keck)

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

Challenges 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 probability-based 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

Advantages Low operations costs - US$250/kg to LEO, GEO, Moon, Mars, Venus or the asteroid belts No payload envelope restrictions No launch vibrations Safe access to space - no explosive propellants or dangerous launch or re-entry forces Easily expandable to large systems or multiple systems Easily implemented at many solar system locations

Summary The space elevator is a revolutionary Earth- to-space transportation system that will enable space exploration Design, deployment and operational scenarios for the first space elevator have been put together. Potential challenges have been laid out and solutions developed. Development of the space elevator requires an investment in materials and engineering but is achievable in the near future with a reasonable investment and development plan.

Bonsor, K. (2000). How space elevators will work. Retrieved from Bochnicek, Z. (2013). A carbon nanotube cable for a space elevator. Physics teacher. Nove2013, Vol. 51 Issue 8, p462- 464. Bonsor, K. (2000). How space elevators will work. Retrieved from http://www.howstuffworks.com/space-elevator.htm Clarke, A. C. (1979). The Space Elevator: “Thought Experiment” or Key to the Universe? Advances in Earth Oriented Applied Science Technology Georgia, F. (2006). The 62,000 mile elevator ride. Business 2.0. Mar2006 Vol. 7 Issue 2, p78-80. Jorgensen, A.M. (2007). Passive radiation shielding considerations for the proposed space elevator. Acta Astronautica. Feb2007, Vol.60 Issure 3, p198-209. Markos, P.A. (2013). A heuristic approach for the positioning of elevator hoistways based on the utilization intensity index. Architectural Engineering & Design Management Nov2013,Vol.9 Issue 4. Nasa. (n.d.). Kennedy space center. Frequently asked questions. Retrieved from. http://www.nasa.gov/centers/kennedy/about/information/shuttle_faq.html#1 Powell, J. (2006). Startram: an ultra-low cost launch system. AIP conference proceedings. 2006, Vol. 813 issue 1, p1071- 1082. 12p. Pugno, N. M. (2006). On the strength of the carbon nanotube-based space elevator cable: from nanomechanics to megamechanics. Journal of Physics: Condensed Matter, 18(33), S1971 Pugno, N.M.(2013). Towards the artsutanov’s dream of the space elevator. the ultimate design of a 35 GPa strong tether thanks to graphene. Acta Astronautica. Feb2013, Vol. 82 Issue 2, p221-224. Takeichi, N. (2012). Geostationary station keeping control of a space elevator during initial cable deployment. Acta Astronautica. Jan2012, Vol. 70, p85-94. Williams, P. (2009). Dynamic multi body modeling for tethered space elevators. Acta Astronautica. Aug2009, Vol. 65 Issue ¾.