Dispersion reduction of a direct fire rocket using lateral pulse jets

Abstract

The impact point dispersion of a direct-fire rocket can be drastically reduced with a ring of appropriately sized lateral pulse jets coupled to a trajectory tracking flight control system. The system is shown to work well against uncertainty in the form of initial off-axis angular velocity perturbations as well as atmospheric winds. In an example case, dispersion was reduced by a factor of 100. Dispersion reduction is a strong function of the number of individual pulse jets, the pulse jet impulse, and the trajectory tracking window size. Properly selecting these parameters for a particular rocket and launcher combination is required to achieve optimum dispersion reduction. For relatively low pulse jet impulse, dispersion steadily decreases as the number of pulse jets is increased or as the pulse jet impulse is increased. For a fixed total pulse jet ring impulse, a single pulse is the optimum pulse jet configuration when the pulse jet ring impulse is small due to the fact that the effect of a pulse on the trajectory of a rocket decreases as the round flies down range.

Microadaptive Flow Control Applied to a Spinning Projectile

“…The projectiles were programmed to divert both left and right, and the impacts measured on the target at 200 m. These results can be seen in figure 39. Also plotted in the figure are simulations of the divert simulated data using the BOOM code (19). The code is a full 6 degree-of-freedom trajectory simulation including an imbedded model of the guidance navigation and control sensors.…”

On the Swerve Response of Projectiles to Control Input

“…There is currently a flurry of activity to create innovative physical control mechanisms. Concepts include pulse jets, squibs, synthetic jets (1,2,3), drag brakes (4,5), deployable pins (6, 7), movable nose (8), movable canards (9), dual-spin projectiles (10,11), ram air deflection (12), and internal translating mass (13), to name a few.…”

A comparison of different guidance schemes for a direct fire rocket with a pulse jet control mechanism

“…Forces and moments acting on the body include weight, air loads, main rocket motor thrust, and lateral pulse jet thrust. Details on the dynamic model of the rocket are available elsewhere and are omitted here for brevity [2,4]. Sensor feedback used by the flight control law is obtained with a conventional IMU.…”

“…For the example configuration considered, impact point dispersion was reduced by a factor of 4. Jitpraphai and Costello [2] studied the same problem using a trajectory tracking flight control law which required an inertial measurement unit (IMU). Rocket dispersion was reduced by as much.as a factor of 100, depending on the lateral pulse jet configuration.…”