Sailing into space

6 05 2010

No, not a comment about today’s election. Although I think we all have a sense that we are about to enter uncharted territory once the votes have been counted. This is a much more uplifting story from Japan about their latest spacecraft, to be launched within the next few weeks.  What could be more elegant than a spacecraft with sails, driven by the sun’s particles, flying at 500,000 miles per hour across the solar system. And note, this idea was first dreamed up by Arthur C Clarke in a science fiction story. At this crucial time in human history we need more people with big dreams, and more people prepared to turn them into reality. I am reproducing the whole story from the Times below.

Leo Lewis in Tokyo

The Japanese space agency, flushed with the success of its origami space orbiter and zero-gravity sushi experiments, is poised for another spectacular leap into the cosmos: the launch of the first “space yacht”.

In three weeks’ time, in a trial run that is expected to captivate space researchers and science-fiction writers alike, a Mitsubishi H-IIA rocket will be sent into orbit from the island of Tanegashima and release its small satellite into the void.

Soon afterwards, having spent a few weeks first settling into a slow rotation, Ikaros will reveal its secret, unfurling the microscopically fine 20m sail that some believe to be the future of interplanetary travel.

Over the following six months — and if the theory of “solar yacht” propulsion holds up — Ikaros will begin its silent journey towards Venus, driven by only the tiny but relentless force of solar particles buffeting the sail.

If it works, it will be a triumph. Other space agencies have succeeded in unfurling experimental sails in space, but have yet to produce the expected propulsion. With every passing second Ikaros should gather a tiny amount of speed.

The craft derives its name from Icarus, the character from Greek mythology whose ill-planned flight took him too close to the Sun and ended in disaster.

Keen to avoid this association, the Japan Aerospace Exploration Agency (Jaxa) is keen to point out that Ikaros stands for Interplanetary Kite-craft Accelerated by Radiation of the Sun. A larger version of the vessel could eventually travel at tens of thousands of miles per hour without any fuel.

The sail is designed to exploit the behaviour of photons, the particles that leave the Sun carrying energy in the form of heat, light and — critically for the space yacht — momentum.

It is the weak but unremitting beams of photons that give comets tails as their solar cores propel the dust behind them.

The Ikaros sail is coated with tiny mirrors that the photons bounce off, pushing the satellite through the resistance-free environment of space.

The Japanese experiment will test how quickly and effectively the photons can drive the satellite along, and how well the device can be controlled.

In theory, larger sails should deliver greater propulsion given enough time. Scientists in the United States believe that a sail a mile across could gradually achieve a pace to carry a craft across the solar system in five years.

If the sail were “shot” with the more targeted light of a laser, a solar yacht could theoretically achieve speeds of 500,000 mph.

In his final novel, The Last Theorem, the late Arthur C. Clarke imagined solar yacht races with astronauts competing to reach the Moon and back by photon power.

The sail, which cost about £10 million to create, is about the thickness of a Cellophane sandwich wrapper (32.5 micrometers) and covered with a second experimental material — so-called “thin film” solar panels, which also have potential applications on Earth.

The panels coat the sail so that Ikaros has a source of electrical power. It can then use it to ionise gas and fire it from small jets — a method of propulsion already used in conventional satellites. Japan is not the only country pursuing space sail technology. Russia is close to producing a version of the space yacht and much of the material science behind the sails has been developed in the United States.

Even if the prospect of sending sail-powered craft through the galaxy remains distant, the technology could make an immediate difference to conventional satellites. Without the need for fuel and cumbersome propulsion mechanisms, sails would allow satellites to be built smaller and lighter, requiring less energy to launch them into space.

The maiden Ikaros mission will last six months but the Japanese agency has further ambitions for the technology if it proves successful. It is hoping to send a device with larger sails towards Jupiter early in the next decade.

Flying high

Arthur C. Clarke, the English science-fiction writer, is best known for The Sentinel, which was made into the film 2001: A Space Odyssey. Clarke had a knack for producing visions of the future. He foresaw the creation of communication satellites, proposing they should orbit the equator.



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