Engineering:Propellant management device
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]
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
- ↑ "DESIGN AND MANUFACTURE OF A LIGHTWEIGHT FUEL TANK ASSEMBLY". http://www.northropgrumman.com/Capabilities/PropellantTanks/Documents/technicalPapers/AIAA2003-4606Star2fuel.pdf.
- ↑ 2.0 2.1 2.2 "Propellant Management Device Conceptual Design and Analysis: Sponges". http://www.northropgrumman.com/Capabilities/PropellantTanks/Documents/technicalPapers/AIAA93-1970.pdf.
- ↑ "Inverted Outflow Ground Testing of Cryogenic Propellant Liquid Acquisition Devices". https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140016830.pdf.
- ↑ 4.0 4.1 "Design and Development of a Communications Satellite Propellant Tank". http://www.northropgrumman.com/Capabilities/PropellantTanks/Documents/technicalPapers/AIAA95-2529.pdf.
- ↑ 5.0 5.1 5.2 5.3 "Propellant Management Device Conceptual Design and Analysis: Vanes". http://www.pmdtechnology.com/pdfs/AIAA91-2172.pdf.
- ↑ 6.0 6.1 "Cryogenic Propellant Management Device, Conceptual Design Study". https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110000503.pdf.
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