PMD Types
Interesting Facts

The first PMD to fly was on the Agena upper stage in the late 1960s. It provided propellant for engine ignition - eliminating the need for solid rocket settling motors. The PMD employed a sponge and a ventable trap.

PMD Technology’s first PMD design was for the HS-601 geosynchronous satellite bus. A trap, sponge and vane PMD met all mission requirements repeatedly. Over 200 HS-601 PMDs have flown - with no failures.

PMD functionality is qualified by analysis only. Ground testing is nearly impossible. Robust design philosophy, heritage, and adequate safety factors ensure success.

The first on orbit propellant transfer between PMD tanks occurred in 2007 on the Orbital Express program. Propellant and pressurant gas were transferred between tanks on separate spacecraft. PMD Technology designed a sponge to meet this challenging mission.

Some PMDs are designed to be installed into the tank after the tank is built. Like a ship in a bottle, the PMDs are designed to furl or be assembled within the tank via a small opening. Designed by PMD Technology, the ICM, Chandra, and Orbcomm PMDs are examples of this construction technique.

Propellant Management Devices, or PMDs, are static all metal structures inside spacecraft propellant tanks that use surface tension to ensure gas free liquid delivery to the tank outlet. They can be made entirely from titanium allowing their use in the most corrosive propellants. With no moving or deforming parts, they are inherently reliable.

Communication Devices

Communication PMDs provide a flow path from the propellant pool to the outlet. They can provide unlimited demand in any direction and, therefore, are the most flexible of PMDs. Unfortunately, if the acceleration level precludes vanes, galleries are required. Galleries are the heaviest, the most costly, and, importantly, the least reliable of PMD components (but also the most capable).



Control Devices

Control PMDs retain some or all of the tank’s propellant over the outlet. They provide for limited duration demand or control the propellant CG. They may retain propellant for repetitious maneuvers - refilling between maneuvers. Alternatively, they can provide propellant for once in a lifetime maneuvers such as spin recovery or a station change maneuver. Sponges, Traps and Troughs are control devices.