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Waverider Should you wish to contact the
society or require general information please contact ASTRA
using the following Email address: Should you encounter any problems
with this Web
Page please
email: ASTRA is an ultra-light, dirigible,
emergency reentry vehicle. The concept is based on the
marriage of two very different aircraft types. The vehicle
is a Waverider. In other words it derives all its lift force
from hypersonic shockwaves, contained by the craft's lower
surfaces, during reentry. This vehicle is not completely
solid, however, and does not require any conventional
control surfaces. This is because the whole airframe can
change its shape in flight, and may be steered by
reconfigurating its lifting surfaces into many sophisticated
permutations. The ASTRA owes its flexibility to
hang-glider design theory, in which a flexible lifting
surface allows billow to shift from one lifting panel to
another. This flexible kite-like configuration is derived
from the Rogallo wing, devised in the fifties for the US
space programme, which subsequently became the basis for
modern hang-glider designs. The ASTRA's 'sail' forms its primary
heat shield, and is made from a triple laminated fabric of
reinforced carbon. This flexible material, as well as
forming the vehicle's thermal shield, also provides the lift
for gliding. The fabric is constructed from triangular and
flat cross sections of carbon fibre, which in turn provide a
material which has a larger surface area on its inner
surface than on the outer. This property allows the sail to
radiate heat faster from one side than the other. The sail
is supported by eight leading edge and cavity struts, also
made of carbon/carbon. These form the characteristic spoke
of the umbrella-like aeroshell: within this protective
parasol, the crew capsule is also protected from any
bleed-through of heat, by a thermal curtain made from a
ceramic cloth. The crew capsules of the craft is
built to accommodate one person, injured or uninjured. The
capsule is cylindrical, with a hemispherical hatch which is
stored in the Space Station airlock until needed. The crew
compartment is about 2 metres long and approximately 800mm
in diameter. The hatch is shielded by a carbon/carbon cap,
and mounted on an external annular structure is a ring of
solid fuel retro motors. Projecting from the hatch cover is
a CCD camera, on a telescopic mount. This enables the
occupant to have a view of the immediate area around the
craft during separation, and just prior to the parachute
retarded recovery on Earth. The entire aircraft is just over 5m
in length and has an extended wingspan of nearly 3m. With an
all-up weight of just over 300kg, the ASTRA has a light
wing-loading of about 16 kg/m2. With this very low loading,
very rapid decelerations are possible, using atmospheric
braking. Conversely, the craft's ability to fold up allows
very gentle decelerations, should an injured crew member
need less rigorous recovery. deorbiting is achieved by
firing the retro-pack, then using an inertial gyro system to
manoeuvre the ASTRA into the correct position for entry. The
autopilot can separate the ASTRA from the Alpha Station
automatically, and pilot the complete vehicle to a safe
landfall, should the occupant be so severely injured that he
or she cannot operate the on board systems. The crew member is held firmly, but
gently, in a vacuum bag immobiliser similar to the
pressurised trousers worn by fighter pilots. This device
envelopes the wearer's lower body from the chest down, and
prevents blood pooling in the legs and feet under extreme G
forces. The arms and head, although supported by sculpted
cushioning, are free to move and operate the controls and
CCD camera, allowing a degree of control to the occupant,
and a certain amount of choice, within the preprogrammed
flight from orbit. This preprogrammed flight is
determined by the entry point of the escape vehicle, and is
determined by a gyro reaction system working in conjunction
with a ground-based beacon network. The flight computer
ascertains the nearest recovery point on Earth, with the
required medical facilities, then computes the course for
the vehicle to follow. When over the landing site, the ASTRA
deploys a drouge chute to stabilise the descent, then a
larger recovery chute. This is a ram-air type canopy, and
can be steered to the landing point, even in quite high
wind-speeds. In a ground impact, the ASTRA
cushions its occupant's fall by means of a large gas piston,
mounted ahead of the capsule, just behind the nose cap. The
craft will then come to rest on its side, so that the
recovery team may help the crew person out. In the event of
an ocean landing the aeroshell would act as a sea anchor,
keeping the capsule upright until recovered.
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