An inertial measurement system comprising: a first, roll gyro with an axis oriented substantially parallel to the spin axis of the projectile; a second gyro and a third gyro with axes arranged with respect to the roll gyro; a controller, arranged to: compute a current projectile attitude from the outputs of the first, second and third gyros; operate a Kalman filter that receives a plurality of measurement inputs including at least roll angle, pitch angle and yaw angle and that outputs at least a roll angle error; initialise the Kalman filter with a roll angle error uncertainty representative of a substantially unknown roll angle; generate at least one pseudo-measurement from stored expected flight data; provide said pseudo-measurement(s) to the corresponding measurement input of the Kalman filter; and apply the roll angle error from the Kalman filter as a correction to the roll angle.

An inertial measurement system for a spinning projectile comprising: first (roll), second and third gyros with axes arranged such that they define a three dimensional coordinate system; at least a first linear accelerometer; a controller, arranged to: compute a current projectile attitude comprising a roll angle, a pitch angle and a yaw angle; compute a current velocity vector from the accelerometer; combine a magnitude of said velocity vector with an expected direction for said vector to form a pseudo-velocity vector; provide the velocity vector and the pseudo-velocity vector to a Kalman filter that outputs a roll gyro scale factor error calculated as a function of the difference between the velocity vector and the pseudo-velocity vector; and apply the roll gyro scale factor error from the Kalman filter as a correction to the output of the roll gyro.

An inertial measurement system (200) for a longitudinal projectile, comprising a first, roll gyro to be oriented substantially parallel to the longitudinal axis of the projectile; a second gyro and a third gyro with axes arranged with respect to the roll gyro such that they define a three dimensional coordinate system. The system further comprises a controller (225, 250), arranged: to compute a current projectile attitude from the outputs of the first, second and third gyros, the computed attitude comprising a roll angle, a pitch angle and a yaw angle; for at least two time points, to compare the computed pitch and yaw angles with expected values for the pitch and yaw angles; for each of said at least two time points, to calculate a roll angle error based on the difference between the computed pitch and yaw angles and the expected pitch and yaw angles; to calculate a roll angle error difference between said at least two time points; to calculate the total roll angle subtended between said at least two time points; to calculate a roll angle scale factor error based on said computed roll angle error difference and said total subtended roll angle and apply the calculated roll angle scale factor error to the output of the roll gyro.

An inertial measurement system (200) for a longitudinal projectile, comprising a first, roll gyro to be oriented substantially parallel to the longitudinal axis of the projectile; a second gyro and a third gyro with axes arranged with respect to the roll gyro such that they define a three dimensional coordinate system. The system further comprises a controller (225, 250), arranged: to compute a current projectile attitude from the outputs of the first, second and third gyros, the computed attitude comprising a roll angle, a pitch angle and a yaw angle; for at least two time points, to compare the computed pitch and yaw angles with expected values for the pitch and yaw angles; for each of said at least two time points, to calculate a roll angle error based on the difference between the computed pitch and yaw angles and the expected pitch and yaw angles; to calculate a roll angle error difference between said at least two time points; to calculate the total roll angle subtended between said at least two time points; to calculate a roll angle scale factor error based on said computed roll angle error difference and said total subtended roll angle and apply the calculated roll angle scale factor error to the output of the roll gyro.

A projectile-launched aircraft system includes a projectile launcher including a triggering mechanism, a rotary-wing, hover-capable aircraft including a rotor assembly that includes at least one rotor blade, wherein the rotor blade includes a stowed configuration and a deployed configuration that is circumferentially spaced from the stowed configuration about a pivot axis, wherein, upon actuation of the triggering mechanism, the projectile launcher is configured to launch the aircraft along a flightpath.

A method and system for constraining navigational drift in a munition caused by Inertial Measurement Unit (IMU) bias error during flight of the munition in a constellation of a plurality of munitions in a Global Positioning System (GPS) denied attack. Each munition is provided with a datalink communication system to communicate with other munitions in the constellation and a navigation system having an IMU for guiding the munition in flight. An estimated position and covariance of the estimated position is determined for each munition via each munitions' navigation system. A range of each munition relative to at least one other munition in the munition constellation is determined via each munitions' datalink communication system. The estimated position and range to at least one other munition in the munition constellation is shared by each munition via each munitions' datalink communication system. Navigational drift for each munition is determined utilizing the estimated position of at least one other munition and the range to that at least one other munition in the munition constellation. And navigational drift in each munition is constrained by compensating for IMU bias error in each munition utilizing the determined navigational drift for each respective munition in the munition constellation.

A method and system for constraining navigational drift in a munition caused by Inertial Measurement Unit (IMU) bias error during flight of the munition in a constellation of a plurality of munitions in a Global Positioning System (GPS) denied attack. Each munition is provided with a datalink communication system to communicate with other munitions in the constellation and a navigation system having an IMU for guiding the munition in flight. An estimated position and covariance of the estimated position is determined for each munition via each munitions' navigation system. A range of each munition relative to at least one other munition in the munition constellation is determined via each munitions' datalink communication system. The estimated position and range to at least one other munition in the munition constellation is shared by each munition via each munitions' datalink communication system. Navigational drift for each munition is determined utilizing the estimated position of at least one other munition and the range to that at least one other munition in the munition constellation. And navigational drift in each munition is constrained by compensating for IMU bias error in each munition utilizing the determined navigational drift for each respective munition in the munition constellation.

The presently disclosed subject matter includes a system and a method for launching a projectile towards a target, wherein the system comprises a control circuitry, a booster engine, and one or more thrusters adapted to be connected to the projectile and capable of being spun during launch around a longitudinal axis of the projectile, the control circuitry being operatively connected to the one or more thrusters; wherein responsive to ignition of propellant stowed in a combustion chamber of the booster engine, the booster engine causes the projectile to launch from its cell; following launch of the projectile, cause the projectile to turn at a certain rate and a certain azimuth.

The presently disclosed subject matter includes a system and a method for launching a projectile towards a target, wherein the system comprises a control circuitry, a booster engine, and one or more thrusters adapted to be connected to the projectile and capable of being spun during launch around a longitudinal axis of the projectile, the control circuitry being operatively connected to the one or more thrusters; wherein responsive to ignition of propellant stowed in a combustion chamber of the booster engine, the booster engine causes the projectile to launch from its cell; following launch of the projectile, cause the projectile to turn at a certain rate and a certain azimuth.

A device, system, and method for shaping the trajectory of a projectile employing a Gravity bias, Gbias. The system includes a seeker, a guidance filter, a pitch rate filter, an actuator, pitch/yaw/roll coupled aerodynamics, and lateral rate sensors. It receives roll orientation input to a guidance and control autopilot; it applies Additional Gbias to that produced by the null rate command to the lateral control loops of the guidance and control autopilot device. The lateral rate command is equal to the desired Additional Gbias divided by an estimate of the projectile velocity. The Additional Gbias is translated to a rate command and incorporated into guidance loop commands to boost an Inherent Gbias to shape the trajectory of the projectile to the target.