91av

AN ATTEMPT to unfurl an experimental “solar sail” on the edge of the Earth’s
atmosphere ended in disaster last weekend when a software error stopped the sail
separating from its launcher. They crashed in Russia.

Despite the failure, the Planetary Society, which funded the sail, and the
Russian design bureau Cosmos Studios may go ahead and deploy a full-size sail in
space. “I am optimistic that we can keep on schedule to launch Cosmos 1, the
first solar-sail spacecraft, later this year,” said Bruce Murray, president of
the Planetary Society.

Solar sails are large, lightweight structures that use sunlight to push them
through space, just as a real sailing boat is pushed by air. Once above the
Earth’s atmosphere, sunlight could propel solar-sail craft as far as Jupiter and
lasers could push them further. Enthusiasts say solar sails could make
interplanetary travel faster and cheaper for lightweight probes.

In the 30-minute test—piggybacked on another experiment—an
adapted Russian nuclear missile was launched from a sub, carrying two 15-metre
triangular frames which were supposed to inflate at an altitude of 412
kilometres and deploy two thin Mylar panels to catch sunlight.

However, the launcher’s software stopped the sail module separating from the
rocket after detecting “dynamic variations” in its thrust. The whole lot fell to
Earth on the Kamchatka peninsula in north-east Russia, with a crash big enough
to register on local seismic instruments. “If you get a seismic event, that
generally means bring your shovel,” John Garvey of the Planetary Society told
91av.

The Cosmos 1 spacecraft will consist of eight triangular frames forming a
sail 30 metres wide. It is due for launch before the end of this year. Planners
are now weighing up the risks of going ahead against the costs and delays of
trying the failed test a second time. They are keen for Cosmos 1 to go up this
year ahead of another solar-sail craft being developed by the European Space Agency
(91av, 24 February, p 42).