Solar fling

NASA is investigating the use of a huge sling shot that could propel robotic spacecraft into deep space from Earth’s orbit.

Researchers claim that a rotating tether tens of kilometres long could provide a sling shot effect, generating 90 per cent of the velocity needed to send a 1,000kg spacecraft to the furthest reaches of the solar system.

The system, known as the Momentum Exchange Electrodynamic Reboost Tether, could operate up to 10 times before needing replacement as a result of the harsh environmental conditions of space. It could be operating by 2020, according to NASA.

The US space agency will spend around $500,000 (£300,000) over the next three years to study the project’s feasibility, as part of its search for energy-efficient launch systems.

Paul Wercinski, head of the In Space Propulsion programme at NASA’s office of space science, said: ‘We are investigating candidate tether materials and one is derived from fishing line. It would have to cope with cosmic radiation and the oxygen atoms in the Earth’s orbit, which damage surfaces they collide and oxidise with.’

A grappling mechanism at one end of the tether would capture probes. A counter mass would be placed at the other end, with an engine in the middle. The tether would be rotating, but its slow pace and vast length would enable it to catch probes without difficulty, while still imparting huge energies to the spacecraft to allow it to reach deep space, Wercinski said.

The system would lose energy when flinging out the spacecraft, but an ion engine would boost its orbit after each fling.

The long tether could also generate electricity from the Earth’s magnetic field, further aiding its orbital reboost.

NASA has already carried out in-orbit demonstrations of this power-generating technology. The electricity generated would be used to accelerate xenon fuel atoms through the ion engine to give the launch system sufficient thrust to renew its orbit.

Also involved in the feasibility study is Washington-based firm Tethers Unlimited, Denver’s Lockheed Martin, the Smithsonian Astrophysical Observatory in Massachusetts and Tennessee’s Technological University.

The tether is one of 22 non-nuclear propulsion technologies, including ion thrusters and solar sails, being investigated by NASA.

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