Propellant management device

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A propellant management device (PMD) provides a way to expel propellant in a low-gravity environment. Devices can use surface tension as the primary expulsion device with a combination of baffles, fins, and vanes. The main goal of the PMD is to provide gas-free propellant to the rocket engine. [1]

Contents

Concept

In the absence of gravity, buoyancy forces do not determine liquid and gas position in a vessel. The positions are primarily driven by surface tension. [2] : 1  The liquids tend to adhere to the walls and leave a gaseous bubble in the center of the vessel. [3] : 2  Propellant management devices (PMDs) are required to provide gas-free operation of the engine. [4] : 1 

PMDs are typically unique and specially designed for each mission. [2] : 1 

Types

There are two groups of PMDs, total communication and control-type. A total communication PMD can acquire propellant from anywhere in the tank. [5] : 3 

Total communication PMD

There are three types of total communication PMDs: vane, gallery, and pleated-liner. [6] : 3 

Vane

Vanes are used when the spacecraft experiences low acceleration and requires low propellant flow rates. Due to their simple mechanical design, they are low cost and highly reliable. [5] : 3  They are typically used in small monopropellant thrusters or to refill another type of PMD: sponges. [5] : 5  Vane length (whether it extends partially up the vessel or to the top) is partially determined by the shape of the tank. Cylindrical tanks require full-length vanes since a portion of the propellant could adhere to the forward tank head. Spherical tanks need full-length vanes in a case by case basis. If the acceleration is lateral, partial-length vanes can work. [5] : 5 

A center post can be added to the tank in addition to the side vanes. This provides a direct path for the propellant to the tank outlet. [4] : 4 

Control-type PMD

There are three types of control-type PMDs: sponge, trough, and trap. [6] : 4 

Sponge PMDs are primarily used to provide the engine with propellant needed for ignition, providing the engine with propellant during a specific maneuver, and propellant control in microgravity environments. [2] : 3 

References

  1. ↑ "DESIGN AND MANUFACTURE OF A LIGHTWEIGHT FUEL TANK ASSEMBLY" (PDF).
  2. 1 2 3 "Propellant Management Device Conceptual Design and Analysis: Sponges" (PDF).
  3. ↑ "Inverted Outflow Ground Testing of Cryogenic Propellant Liquid Acquisition Devices" (PDF).
  4. 1 2 "Design and Development of a Communications Satellite Propellant Tank" (PDF).
  5. 1 2 3 4 "Propellant Management Device Conceptual Design and Analysis: Vanes" (PDF).
  6. 1 2 "Cryogenic Propellant Management Device, Conceptual Design Study" (PDF).
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