Module A-3 Carbon Nanotubes

Space Elevators

First elevator: 20 ton capacity (13 ton payload)

Constructed with existing or near-term technology

Space Elevators

Space Elevators

Challenges

• Induced Currents: milliwatts and not a problem• Induced oscillations: 7 hour natural frequency

couples poorly with moon and sun, active damp- ing with anchor

• Radiation: carbon fiber composites good for 1000(?) years in Earth orbit (LDEF)

• 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

• Damaged or severed ribbons: collatoral damage is minimal due to mass and distribution

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

Processing Techniques

Discharges

• Cheap

• Yield ~30%

• Short (<50 microns)

• Random deposits

CVD Growth Mechanisms

MWNTs by CVD Methods

Single Walled NTs

Heterostructure Carbon nanotubes

Catalytic CVD Growth

Hongjie Dai, Stanford

Catalytic Methods

• High potential for scale-up production• Long lengths• Multiwall CNTs• Many defects in the materials

CNT for Electronics

• Carrier transport is 1-D.• All chemical bonds are

satisfied CNT Electronics not bound to use SiO2 as an insulator.

• High mechanical and thermal stability and resistance to electromigration Current densities up to 109 A/cm2 can be sustained.

• Diameter controlled by chemistry, not fabrication.• Both active devices and interconnects can be made

from semiconducting and metallic nanotubes.

Transport on a single CNT

Transport on a single CNT