Indian Institute of TechnologyHyderabad

THE SPACE ELEVATOR

Aaditya Sapkal(ES12B1016)

The Components

The Ribbon

The Anchors

The Climbers

The Power

The Ribbon: Design

The Ribbon: ConstructionInitial production takes

place on earthAligned nanotubes are

epoxyed into sheets, which are then combined (reinforced)

Climbers have a similar system on-board to build tether

Why Carbon Nanotubes?Property Single Walled

NanotubesMetal wires

Tensile Strength 45 billion pascals High strength steel alloys break at about 2 billon pascal

Resilience Can be bent at large angles and restraightened without damage

Metals and carbon fibers fracture at grain boundaries

Temperature stability

Stable upto 2800 degrees in vacuum, 750 degrees in air

Metal wire in microchips melt at 600 to 1000 degrees C

The Anchors

• The space anchor will consist of the spent launch vehicle

• The Earth anchor will consist of a mobile sea platform 1500 miles from the Galapagos islands

The Climbers

Initial ~200 climbers used to build nano-ribbonLater used as launch vehicles for payloads from

20,000- 1,000,000 kg, at velocities up to 200km/hrClimbers powered by electron laser & photovoltaic

cells, with power requirements of 1.4-120MW

The Power Free-electron lasers

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 ConstructionAtmospheric:

oLightningoHigh WindsoAtomic Oxygen

Orbital: oMeteors oLow orbit object

Ribbon Breakage

Problems: Solutions:

Sufficient Ribbons

Nanotubes must be defect free and straight

The epoxy must be strong yet flexible, burn up at a several hundred Kelvin, and cure relatively quickly

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, (spark gap)

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

Threat: Solution:

Atmospheric Oxygen 60-100km

Extremely corrosive, will etch ribbon epoxy and possibly nanotubes

Coat ribbon with Gold or Aluminum which have resisted etching in these atmospheric conditions,(NASA’s Long Duration Exposure Facility

Low Orbit Objects 500-1700kmThreat: 108,000 (>1cm)

objects with enough velocity to sever or critically damage tether. Strikes could occur ~every 14 hours

Solution: Tracking systems for

objects >10cm already in place, sea platform will move tether to avoid

Tracking systems for 1-10cm objects coming on-line

LightningThreat: 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 WindsThreat: 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