More about Bloodhound Homing

Pete Murray gave an expansion as to how the homing methed was achieved.

A very rough outline (from memory):
  • A gyro mounted on the dish allows its stabilisation via the dish servo (decoupling it from missile motion).
  • A spinning antenna offset from the spin axis creates a conical scan pattern. The phase and amplitude of the received signal reveal the dish pointing error (direction and magnitude of target misalignment from boresight). The dish servo steers the dish, via precession of the gyro, to null the dish pointing error.
  • The output of the dish servo represents the sight line rate in pitch and yaw. Zero sight line rate implies that the missile will intercept the target. Thus, to achieve an interception, the missile flight path must be controlled to null the sight line rates.
  • The pitch and yaw sight line rates are resolved into pitch and roll errors for the wing control servo.
    The roll channel moves the wings differentially to control to the missile roll rate and null the roll error, which brings all the error into the pitch plane. The Pitch channel moves the wings together to control missile flight path, such that an acceleration (around a curved path) proportional to the error is achieved. How hard the missile manoeuvres for a given error is controlled by a navigational constant
Other Notes (again, from memory):
  • The missile was monostable in the pitch plane (it would only pitch only one direction).
  • The missile had a weathercocking motion in flight; hence, two accelerometers displaced as far apart as possible were used in the pitch feedback loop.
  • A gyro provided roll rate feedback.
  • The navigational constant was halved for engagements against receding targets.
  • Gravity created a one G bias on the accelerometer output, which had to be compensated for to prevent the missile coming to earth during low altitude engagements.
  • The missile had characteristic body twisting and bending moments, which had to be filtered from the roll and pitch control channels.
  • Sightline rates were heavily filtered until switched out via the command link.
  • Navigation was in bearing only until climb cruise was switched out via the command link.
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