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SPRINGTIME leaves have given engineers a new way to build spacecraft antennas
that won鈥檛 get stuck when they are unfolded in orbit. The idea is to copy the
way that leaves are able to unfurl from their buds in one smooth movement.

Spacecraft antennas usually have to be folded to fit into their launcher. But
unfolding them in orbit is a risky business, as there鈥檚 usually no one on hand
to fix them if things go wrong. In 1991, the Galileo space probe failed to
unfurl an umbrella-like antenna because some of its 18 spokes got stuck. And
this is just one among legions of orbital mishaps that have wrecked solar panels
and power-generating tethers as well as antennas.

Now Cambridge University engineers Davide De Focatiis and Simon Guest have
found inspiration up in a tree. Their plan for a foolproof antenna mimics the
hornbeam, whose budding leaves are highly folded so that they fit inside a
small, protective bud.

A key aspect of the way the hornbeam鈥檚 leaf is folded, De Focatiis says, is
that it can be opened by simply spinning it from one end. A solar panel built
this way wouldn鈥檛 need a complex set of motors acting in sequence to open it up.
It would also work without conventional hinges. 鈥淚f the material a panel is made
from is sufficiently flexible, it acts as its own hinge,鈥� says De Focatiis. And
with energy stored in the fold, it should unfurl smoothly of its own accord when
spun.