|
NB - Green numbers within brackets
refer to references.
AERODYNAMIC
CONTROL AND MASS SHIFT.
The principle of Subtractive Control
mentioned above entailed removing parts of the airframe or
wing from the airflow, downwind of the shockwave, to alter
the dynamic trim of the vehicle. Since removing part or all
of a control "surface" reduces or removes completely its
intrinsic drag, the system of "subtractive" control should
reduce drag overall rather than increasing it, when the
controls are operated.
For the Terrestrial Flexwing, a
sliding payload palette may also be used to adjust pitch
trim during flight. Slight pitch-down trim would be an
advantage during the final subsonic phase of a reentry and
the sliding palette would also permit de-stabilisation, by
moving the mass centre rear wards, should more radical
aerobatics be necessary in an emergency.
Rear-mounted body flaps (similar to
the surfaces proposed by McDonnell Douglas for their Evader
test vehicle) could be used to effect major pitch and roll
changes, however a gentler roll control could be provided by
billow-shift techniques. This would reduce drag greatly and
increase the glide range appreciably.
When the vehicle is required to
produce lift to counteract gravity, as in level flight,
mass-shift control would be a relatively efficient method of
trimming or auto-piloting an unmanned vehicle. In conditions
where negative flight loads or periods of micro-gravity are
likely, an offset centre of mass could have a major effect
on the behaviour of the Waverider- in which case, a back-up
system of flaps would be a prudent precaution.
The Interplanetary Megasonic Flexwing
could not rely on mass-shift alone for control, since
gravity and centrifugal forces would be acting in the same
plane during only part of the encounter. The variable
geometry leading edges would permit lift vector changes,
making the "conical roll" manoeuvre described in the
previous paper 4 unnecessary. Transition of the vehicle from
one part of the shock-cone to another, may be achieved by
retracting struts from the shock-cone and by deploying one
or more of the other struts so that the shockwave is
reattached to the "new" leading edges.
As a result, a different combination
of lifting surfaces is brought into operation. The payload
is shown mounted in a cradle, suspended from a cantilever
spar. The spar is articulated from the nose cone, permitting
a limited degree of radial movement within the aeroshell.
The cantilever spar is also telescopic and the payload mass
may be moved forward or rearward as required. The
compression struts, which brace and extend the leading
edges, are attached to the cantilever spar and may be used
to immobilise the payload mass in any forward, rearward,
offset or centred position. This allows a very wide range of
configurations for many different flight
conditions.
|
 Page
Five
|
Page
Seven
|
|
