Operational feasibility study of stagnation pressure reaction control for a mid-caliber non-spinning projectile

Controlled,guided munitions can reduce dispersion in the shot,while providing the capability of engaging both stationary and maneuvering targets.The Netherlands Organisation for Applied Scientific Research has developed a fin-less control technology called Stagnation Pressure Reaction Control(SPRC)that takes stagnation pressure air and directs it sideways to control non-spinning projectiles.In a previous study,this technology was demonstrated at Mach 2 wind-tunnel conditions to achieve up to 1.5°controllable angle of incidence for a non-spinning,aerodynamically unstable projectile-like test object.In an operational scenario,the decelerating projectile will experience a decline in control force while the simultaneous forward shift of the center of pressure increases the need for control force.Furthermore,angles of incidence exceeding 1.5°will be experienced under realistic flight conditions,especially against maneuvering targets.This work addresses these challenges and presents an operational feasibility study for a practical application of SPRC in a non-spinning mid-caliber gun-launched projectile,using experiment data on control latency and force of the earlier study.It illustrates the combined effect of the control-and stability dynamics and underlines the potential of an SPRC projectile as a precisionoperation ammunition.This research revealed that SPRC technology can stabilize and control the hypothesized projectile in a direct fire scenario against stationary and maneuvering targets.

Nonlinear L_(1) adaptive control of stagnation pressure in a cryogenic wind tunnel

Cryogenic wind tunnel is a sophisticated aerodynamics ground test faility,which operates in cryogenic temperature with injection of liquid nitrogen.The multi-variable,nonlinear and coupled dynamics existing between the temperature,pressure and Mach number in the tunnel,poses great challenges for the effective control of the tunnel.L_(1) adaptive control is a new control methodology developed in recent years with good robustness properties,which has good potentials to address these challenges.But this control method does not provide full adaptive feedforward control in its generic structure.In the paper,adaptive feedforward control action is introduced into the standard L_(1) adaptive control architecture for nonlinear systems in the presence of matched un-modeled dynamics.This new control structure is applied to the stagnation pressure control in a cryogenic wind tunnel,which could also be used for the control of temperature and Mach number in the tunnel.This new method could effectively compensate known disturbances with linear gain uncertainty,which occur in the nonlinear systems,while retaining the closed-loop control performance of L_(1) adaptive control.After the proof and discussions on the stability of this method,simulations of the stagnation pressure control in the wind tunnel are presented.The results and analysis demonstrate the effectiveness of the proposed control architecture.

Mechanism and numerical simulation of pressure stagnation during water jetting perforation

When perforating with an abrasive water jet, it is possible that the pressure in the hole （perforation） will be higher than that in the annulus because of water jet blasting against the hole wall, which also is the theoretical basis for the technology of hydro-jet fracturing. This paper analyzes the mechanism of generating pressure stagnation in water jet hole, and puts forward a new concept of hydroseal. Then, the distribution of pressure in the hole was simulated with the finite element method. The simulation results showed that the pressure in the hole was higher than that in the annulus. Also, the lower the annular pressure （confining pressure） and the higher the blasting pressure, the greater the pressure difference. An experiment indicated that the cement sample was lifted up under the pressure stagnation in the hole, which proved the finite element simulation results obviously.