THE SPACE ELEVATOR

JISHI P P14AE60R01

CONTENTS

• History

• What is a Space Elevator ?

• The Components

• Deployment

• Major Hurdles

• Advantages & Disadvantages

• Conclusion

HISTORY

Konstantin Tsiolkovsky

The key concept of the space elevator appeared in 1895 when Russian scientist Konstantin Tsiolkovsky was inspired by the Eiffel Tower in Paris.

WHAT IS A SPACE ELEVATOR?

• Cable attached to the Earth near the equator which extends directly into space and is attached to a small counterweight revolving in orbit.

• Stays in position because the gravitational force is equal to the centripetal force.

SPACE ELEVATOR IN ORBIT

THE COMPONENTS

Cable / Ribbon / Tether

Anchors / Platform

Climbers / Elevator car

Power

Counterweight

THE CABLE

WHY CARBON NANOTUBES?

Property Single WalledNanotubes

Metal wires

Tensile Strength 200 billion Pascal High strength steel alloys break at about 2 billon Pascal

Resilience Can be bent at large anglesand re-straightened without damage

Metal fractures at grain boundaries

Temperature stability Stable upto 2800 degrees in vacuum, 750 degrees Celsius in air

Metal wire melt at 600 to 1000 degrees C

Density 1300 kg/m^3 7900 kg/m^3

CABLE : CONSTRUCTION

• Initial production takes place on earth.

• The cable is a carbon nanotube/epoxy composite.

• Aligned nanotubes are epoxied into sheets, which are then combined (reinforced).

• Climbers have a similar system on-board to build tether.

Problems: Solutions:

CABLES CONSTRUCTION

• Nanotubes must be defect free and straight

• The length of the finished cable is 91,000km, and nanotubes are cm in length

• Large scale behavior of nanotubes unknown

• Nanotubes are grown aligned, and defects can be controlled in current production methods .

• The ribbon can be produced in small length bundles and then connected

CARBON NANOTUBES (CNTS) till now

Carbon nanotubes: measured at 200 GPa (54xKevlar)

– Sufficient to build the elevator

Mitsui(Japan): 120 ton/year CNT production, US$100/kg

– Sufficient to build the first elevator

THE ANCHORS

• 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.

THE CLIMBERS:

• Initial ~200 climbers used to build cable.

• Later used as launch vehicles for payloads from 20,000- 1,000,000 kg, at velocities up to 200 km/hour.

• Climbers powered by electron laser & photovoltaic cells, with power requirements of 1.4-120MW.

THE POWER

• Electron lasers can be used to deliver power

• Adaptive Optics on Hobby-Eberly telescope used to focus Earth-based beams, (25cm spot @ 1,000km altitude)

• Reduced power delivered at high altitudes compensated by reduced gravitational force on climber, (~0.1g)

DEPLOYMENT

MAJOR HURDLES

• Ribbon Construction

• Atmospheric:oLightning

oHigh Winds

oAtomic Oxygen

• Orbital: oMeteors

oLow orbit object

Threat:

ATMOSPHERIC OXYGEN @ 0-100KM

• Extremely corrosive, will etch ribbon epoxy and possibly nanotubes.

Solution:

• Coat ribbon with Aluminum or Gold which have resistance to etching in these atmospheric conditions.

LOW ORBIT OBJECTS @ 500-1700KM

Threat:

• Objects (>1cm) with enough velocity to sever or critically damage tether.

• Strikes could occur ~every 14 hours

Solution:

• Tracking systems for objects already in place, sea platform will move tether to avoid collision.

LIGHTNING

Threat:

• Ribbon has lower resistivity than surrounding air, lighting will prefer this path.

Solutions:

• Platform lies in a region of very low lightning activity

• Platform is mobile, and can move tether out of the way of incoming storms

High Winds

Threat:

32m/s wind velocity will induce enough drag to destroy tether

Solution:

Winds at platform location consistently below critical velocity

Width of tether will be adjusted to minimize wind loading

ADVANTAGES

• Low operations costs - US$250/kg to LEO, GEO, Moon, Mars, or the asteroid belts.

• No payload envelope restrictions

• No launch vibrations

• Safe access to space.

• Easily expandable to large systems or multiple systems.

• Unknown behavior.

• Will be costly to build.

DISADVANTAGES

• 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, and it will revolutionize Earth-to-space transportation.

CONCLUSION

• Japanese construction firm, Obayashi Corp., announced on Sep 26, 2014 that they’ll have a space elevator operational in the next 35 years .

• By the year 2050, you may not need a rocket to reach the Moon, just an elevator.

RECENT NEWS

REFERENCES

• 1.“DESIGN AND DEPLOYMENT OF A SPACE ELEVATOR” Bradley c. Edwards

• 2. “What is a Space Elevator.” ISEC. 2012 http://www.isec.org/index.php/what-is-a-space-elevator.

• 3. B. Laubscher. (2005). “The Space Elevator.” American Institute of Physics http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=APCPCS000786000001000602000001&idtype=cvips&doi=10.1063/1.2103939&prog=normal.

• 4. P. Aravind. (2006). “The Physics of the Space Elevator” Worcester Polytechnic Institute http://scitation.aip.org/journals/doc/AJPIASft/vol_75/iss_2/125_1.html

• 5. J. Pearson. (1975). “The orbital tower: a spacecraft launcher using the Earth’s rotational energy.” ActaAstronautica. http://www.star-tech-inc.com/papers/tower/tower.pdf.

• 6. B. Edwards. “The Space Elevator.” http://www.niac.usra.edu/files/studies/final_report/472Edwards.pdf

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