Cold Gas Thruster Triad – Model 50-820’s design evolved from years of Moog miniature solenoid valve experience. Moog supported high profile SDI programs such as SCIT, THAAD, ASAT and GBI/EKV by designing very small, lightweight and fast acting pilot actuated thruster valves. Moog transferred technology from these programs to develop a family of commercial cold gas thruster valves. Specifically, Model 50-820 was qualified for the Pegasus XL launch vehicle’s attitude control system. The triad configuration is a perfect solution for packaging three thrusters into a very small envelope.
Model 50-820 packages three individual pilot valve actuated, normally closed, cold gas thrusters into a single housing. At 2,000 psi inlet pressure, the two outboard thrusters produce 11.75 lbf thrust each and the center thruster produces 23.5 lbf. Each thruster has the capability of being fired independently, simultaneously or in combinations with the other two thrusters to achieve the desired thrust vectoring.
The main seat is closed when the pilot valve is not energized. In this mode a solenoid spring and supply pressure position the pilot poppet against the vent seat. This allows supply pressure to build in a cavity behind the main stage poppet forcing it closed.
When the pilot valve is energized, the pilot poppet moves to the supply pressure seat, uncovering the vent seat and allowing pressure behind the main poppet to vent. At this point the supply pressure acting on the front of the main poppet overcomes the decaying force behind the main poppet causing it to open.
De-energizing the pilot valve allows the solenoid spring and supply pressure to move the pilot poppet back to the vent seat allowing pressure to re-build behind the main poppet overcoming the forces on the front of poppet, closing the main seat.