Spaceline design would ferry astronauts from Earth’s orbit to the moon

Scientists draw up plans for a bizarre ‘space elevator’ which could ferry astronauts from Earth’s orbit to the lunar surface — but it would take several DAYS to get there

  • The traditional space elevator concept would link the ground with Earth’s orbit
  • However we currently cannot build such a cable capable of supporting its weight
  • A ‘spaceline’ would avoid most of Earth’s gravity by going from orbit to the Moon 
  • Using solar powered elevator cars would cut fuel costs to the moon by a third

A proposal for an unusual type of space elevator would see a cable link the moon with a docking station in Earth’s orbit.

Astronauts and cargo flown up to the orbital dock could then be ferried to the lunar surface in a solar-powered elevator car.

Using this so-called ‘spaceline’ would cut down on the rocket fuel needed for a trip between the Earth and Moon by a third.

However, the journey in the elevator could take several days or even weeks, meaning that the elevator cars would need to able to support humans during the long trip.

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An unusual type of space elevator would see a cable link the moon with a docking station in Earth’s orbit. Astronauts and cargo flown up to the orbital dock could then be ferried to the lunar surface in a solar-powered elevator car

The traditional concept for a space elevator imagines a cable linking the Earth to a point directly above, stretching out beyond Earth’s geostationary orbit.

However, at present, we are unable to create a cable strong enough to support its own weight.  

Instead, astrophysicists Zephyr Penoyre and Emily Sandford of the Columbia University in New York propose to build the elevator in the opposite direction, reaching out from orbit to the surface of the moon.

This would avoid the challenging gravitational forces found close to the Earth. 

‘A cable which only hangs into Earth’s gravitational well need not be thick or massive,’ Mr Penoyre and Ms Sandford write in their draft paper.

‘It is optimal to make it as thin as possible as it extends closer to Earth. This means that the gravitational forces the cable feels, and thus the tension, is much reduced.’

At the closer end of such an elevator — which the researchers dub the ‘spaceline’ — a docking station would allow rockets from the Earth the shuttle up astronauts, cargo and scientific equipment.

This would then be transported along the enormous cable to the Moon’s surface, at a fraction of the energy costs of sending a rocket along the same journey.

The only drawback of the spaceline concept, however, is that the elevator ride would take considerably longer than riding in a normal space elevator up into orbit.

The journey in the elevator car would likely take several days to the traverse the distance. 

Using the spaceline would cut down on the rocket fuel needed for a trip between the Earth and Moon by a third. Pictured, an artist’s impression of the Earth seen from the lunar surface

The traditional concept for a space elevator, like in this artist’s impression, imagines a cable linking the Earth to point directly above, stretching out beyond Earth’s geostationary orbit

‘Building a spaceline would be a huge engineering challenge, stretching the limits of current human capacity — but not exceeding them,’ the researchers wrote.

‘Even in its most economical form, a cable with a width only a little more than a pencil lead, it could cost billions of dollars for material and transport — and it is hard to quantify what extra cost such a project could incur.’

‘But a billion dollar price tag is not unattainable — and the possibilities of what could be done with such a structure may quickly pay dividends.’

One issue involved in maintaining the spaceline, however, would be in dealing with the damage created by micro-sized meteoroid impacts — which would even break the cable on impact.

The researchers suggest that the cable could be made of multiple strands, allowing for one to break with compromising the strength of the whole. 

The full findings of the research are being prepared for submission to the journal  Acta Astronautica. 

A pre-print of the article, which has not yet been peer-reviewed, can be read on the arXiv repository.

WHY BUILD A SPACELINE?

Reduced transport costs 

It costs slightly less, in fuel, to reach the spaceline than to move into a geostationary orbit.

Transport along the cable would be free, the the elevator cars were designed to be with solar powered.

This would reduce the fuel needed to reach the surface of the moon to a third of its current value.

Simple and safer journeys  

Motion between points on the spaceline is simpler and safer than moving, docking and navigating through empty space.

Haulage to and from the surface of the moon

Small loads can be sent to and from the moon.

The ability to transport material to and from deep space from the moon without needing rockets changes the economics of the scientific and industrial projects that could be undertaken on the lunar surface. 

The technological endeavour

A project such as this will inevitably present engineering challenges.

Overcoming them will push forward our technological capacities. 

A difficult but achievable task requires us to make and master new techniques, and rewards us for doing so.

Establishing a ‘base camp’ at the Lagrange point

The Earth–Moon Lagrange is a gravitational still point where the tug-of-war between the Earth and the Moon’s gravity is balanced out.

Passing through it, the spaceline makes the Earth–Moon Lagrange point effectively stable. 

In this gravity free environment we can construct habitats and equipment of arbitrary mass.

Previous space stations have been constrained by cramped conditions and dangerous environments. 

In contrast the Lagrange point is a haven for expansion and cultivation. 

Such a base camp would allow the construction and maintenance of a new generation of space based experiments.

These could include telescopes, particle accelerators, gravitational wave detectors, vivariums, power generators and launch points for missions to the rest of the solar system. 

 

Source: Penoyre & Sandford, The Spaceline: a practical space elevator alternative achievable with current technology

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