CAN a bizarre spacecraft that is powered by a rotating rocket engine and that
lands like a helicopter transform space travel? In March, an American company
will be a step closer to finding out, when a prototype of the Roton craft starts
putting these concepts to the test.
Known as the atmospheric test vehicle (ATV), the prototype will be used to
test the craft鈥檚 unique landing system鈥攆our helicopter blades, each 7
metres long, intended to slow the Roton鈥檚 descent. If the tests are successful,
the first Roton could blast into orbit as early as next year. It should slash
the cost of getting satellites into space, says Gary Hudson of the Rotary Rocket
Company in Redwood City, California.
The secret lies in its outlandish design
(see 鈥淩ocket revolutionary鈥�, 快猫短视频, 1 August 1998, p 24).
Its conical body is built from lightweight
graphite composites instead of aluminium. Hudson has also eliminated the need
for the heavy turbopumps that feed fuel to conventional rocket engines by making
the whole engine spin. Ninety-six combustion chambers are mounted around the
edge of a disc 7 metres wide. Spinning at 720 revolutions per minute, the disc
throws fuel and oxygen outwards into the chambers from storage tanks in the
craft鈥檚 body. And to make the craft truly reusable, the Roton is supposed to
land gently beneath whirling rotor blades鈥攚hich is where the ATV comes
in.
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Over the next year the ATV will make about 10 manned flights at Mojave in
California to test the rotors and landing systems. Although it lacks the
spinning rocket engine needed to get it into orbit, the ATV will still be able
take off under its own power, thanks to the small rocket thrusters on the tips
of its rotors (see Diagram).
In real missions, the thrusters will be used just
before the Roton reaches the ground. The extra lift they generate should allow
the spacecraft to land without being damaged.
In the upcoming tests, however, the thrusters will also lift the ATV off the
ground. With each rocket producing 350 pounds of thrust, the rotors will spin
fast enough for the Roton to climb off the launch pad like a helicopter. 鈥淭he
rockets will provide about 5 to 10 minutes of power,鈥� says Hudson. 鈥淚n fact,
it鈥檚 the largest tip-powered helicopter ever built.鈥�
After its ability to hover has been tested, the ATV will be flown to an
altitude of about 2000 metres. Then the thrusters will be switched off, but as
the craft descends, the airflow will keep the rotors spinning, providing enough
lift to slow its descent. Just before it reaches the ground, the pilot will
adjust the angle of the rotor blades to maximise lift and slow the craft鈥檚
descent to about 1 metre per second. The tip thrusters will be fired at this
stage too, says Hudson, allowing the Roton to hover for a few seconds before
touching down gently.
Over the next 18 months, the Rotary Rocket Company plans to build three more
Rotons: an unpowered version for training, and two complete craft for orbital
missions in 2000.