3-way Isolation Valve (3IV)

Status date

This project will encompass the development of a Three-way Isolation Valve (3IV) for satellite propulsion systems.

The valve will connect the propellant tanks, the thruster branches and the fill and drain valve (FDV). However it will be possible to totally isolate each branch from the two others.

For example during AIT, the 3IV would open a path between FDV and thruster branches, thus allowing testing of the thrusters, while the tank would not be contaminated.

During fuelling operations the tank and FDV shall be connected for trivial reasons. The thrusters however would be isolated in order to avoid accidental firing, which is a great hazard not only for hydrazine systems. During flight operations of course, the tank shall be directly connected to the thrusters.

Finally we will try to have a total isolation position for a secure launch and to hinder leakages on each connected branch.


The main technological issue for this project is the selection of the right actuation principle, which will give the lowest leakage possible together with the longest cycle life. The second aspect is the selection of the most reliable, light and proven DC motor for the actuation. A slow actuation should also be achieved in order to avoid water hammer on liquid propulsion systems.

  • A single valve to isolate propellant tanks from thruster branches and to use the standard fill and drain valve as a test port for the thruster branches.
  • An isolation valve with a high open/close cycle life.

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  • Connection of any combination of 2 attached branches,
  • Use of space qualified DC motor,
  • Avoidance of water hammer,
  • Primarily for liquid propulsion, but with cold gas propulsion as option (significant difference in pressure ranges and sealing materials),
  • Use of proven technology for a development with minimal risk

The first tasks will be the establishment of a requirement specification and the trade-off of several actuation principles to achieve the best possible functionality. These projects stages will be followed by the generation of a first design and a breadboard. Testing this breadboard will permit to refine and prove the design. Lastly an Engineering Model of the valve will be constructed to optimise further the design until everything is ready for a future qualification of the valve.

Current status

The development of the 3IV started in October 2007. Our first aim is to establish a requirement specification. Also, a catalogue of possible technological concepts describing existing off the shelf components will be assembled.