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THE SPACE ELEVATOR
Noyal SharookM7B37
Guided ByPadmakumar PMechanical Department
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Contents
• Concept• Why built it• Component study• Major hurdles• Bibliography
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ABOUT THE CONCEPTSpace elevators are incredibly tall theoretical structures that connects the earths surface and outer space, beyond the geosynchronous orbit (35,800 km). The structure acts as a continuous and viable channel by which payload can be send in to space.
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Why build it ?
CURRENT
Cost of a launch $22,000 per kg
Huge vibration, more hardware and non reusability
Riding on a continuous and giant explosion is extraordinarily
dangerous, as is re-entry (Challenger, Columbia)
ELEVATOR
Cost of launch $660 per kg.
Less vibrations , less hardware required and continuous use
Safe access to space - no explosive propellants or
dangerous launch or re-entry forces.
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The Components
The Cable
The Anchors
The Climbers
The Power
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Cable• The cable acts as a guide rail for
climbers and should be strong, flexible and light
• Considering all these factors along with meteor impact effect, a ribbon-type epoxy/nanotube composite design is optimal
• The ribbon is made such that its thickness is more near the geosynchronous orbit (5cm) thanat its ends (11.5cm)( tapered construction)
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Why Carbon Nanotubes?Property Single Walled
NanotubesMetal wires
Tensile Strength 130 GPa Steel < 5GPaKevlar 3.6 GPa
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
Density 1300 kg/m^3 Steel 7900 kg/m^3Kevlar 1440 kg/m^3
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Cable Deployment
• Initially a small, stable cable (1 lakh km) is spooled up in a space craft and send in to the geosynchronous orbit.
• The cable is connected to spindle on either side, which will be deployed to opposite sides on reaching orbit.
• One end will fall on to earth due to gravity while the other will be pulled outward due to centripetal acceleration
• Once the cable is anchored on earth, it is built on and made larger using climbers.
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AnchorAnchor 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
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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 Initial climbers are used to build ribbon
and are sent up at every 0.1g (13,000km) altitude
1 week to reach geosynchronous orbit , utilizing 80w/kg
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Power Beaming Propulsion• Various methods proposed to get the
energy to the climber are:1. Wireless energy transfer 2. Transfer the energy to the climber
through some material structure3. 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.
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WIRELESS ENERGY SYSTEM • 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• 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
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Major Hurdles
• Ribbon Construction• Atmospheric:
o LightningoHigh WindsoAtomic Oxygen
• Orbital: oMeteors o Low orbit objectoRadiation damage
• Ribbon Breakage
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Sufficient RibbonsProblems:
• 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
• Large scale behavior of nanotubes unknown
Solutions:
• 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
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Atmospheric Oxygen 60-100km
Threat:• Extremely corrosive, will
etch ribbon epoxy and possibly nanotubes
Solution:• Coat ribbon with Gold or Aluminum
which have resisted etching in these atmospheric conditions,(NASA’s Long Duration Exposure Facility
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Low Orbit Objects and MicrometeorsThreat:• 108,000 (>1cm) objects
with enough velocity to sever or critically damage tether. Strikes could occur ~every 14 hours
• Micrometeors <1cm and > 2cm involved.
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
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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
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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
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Bibliography• DESIGN AND DEPLOYMENT OF A SPACE ELEVATOR Bradley C.
Edwards Los Alamos National Laboratory, Mail Stop D436, Los Alamos, NM 87544, USA
• The space elevator: a new tool for space studies Edwards BC Eureka Scientific, Seattle, WA, USA. [email protected]
• Getting to Space on a Thread .. Space Elevator as Alternative Access to SpaceJason R. Kent, Major, USAF, PE
• https://en.wikipedia.org/wiki/Space_elevator• http://spaceref.com/space-elevator/
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QUERIES??
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THANK YOU!!
