杏吧原创

EIGHT parachutists are to attempt a unique, low-altitude descent in
September. They will leap from an altitude of just 75 metres鈥攍ower than
Big Ben but higher than Nelson鈥檚 Column.

The jump, by the parachute test team at Britain鈥檚 Defence Evaluation Research
Agency (DERA) in Boscombe Down, Wiltshire, will cap a decade of work trying to
create a parachute that allows paratroopers to descend safely from aircraft
flying below the gaze of enemy radar.

Although special stunt parachutes exist for the sport of 鈥渂ase jumping鈥�, in
which daredevils leap from tall buildings, these are aerodynamically unsuitable
for military parachute drops.

The new parachutes are made from the same heavy-duty nylon as conventional
military chutes. But instead of the usual 鈥渄ome鈥� shape, they look more like
jellyfish, with tucked-in rims, and they capture air more effectively.

So far, paratroopers have made more than 15 000 test jumps with the new
parachutes, but none from altitudes lower than 250 metres. September鈥檚 drop will
be the acid test for the design. 鈥淔rom exit to full inflation takes around 4
seconds,鈥� says Mark Smith, squadron leader of DERA鈥檚 parachute test team. That
will leave around 30 metres of descent with a full canopy in the 75-metre
drop.

The entire descent is expected to take 10 seconds. To avoid the possibility
of serious injury, Smith and his colleagues will make the drop over a lake in
the south of France.

Smith says the project is being watched closely by the world鈥檚 armed forces.
鈥淭here鈥檚 considerable international interest in this trial,鈥� he says. The
previous lowest jump using military parachutes was from around 130 metres, when
US troops invaded the Caribbean island of Grenada in 1983.