The OST-2 tank (surface tension tank) is designed to transfer vapor-free propellant to the thrusters of geostationary satellites.

  • Cassini top and bottom part
  • Propellant aquisition device
  • Propellant Management Device (PMD)
  • Propellant port

The PMD consists of a refillable reservoir and four interacting tubes; each provided with an adapter screen component and connected with a lower sump adapter element. This assembly prevents gas bubble penetration in the outlet pipe.

Four guide vanes in this area serve as a pumping and retaining device. Further PMD elements are those guide vanes attached to the housing to affect damping and capillary pumping. As a consequence of refilling during ballistic (non-driven) flight phases infiltrated gas effuses out of the reservoir.


During compensated gravity the liquid will be positioned stable above the outlet in a reservoir in this PMD - the PRR. The reservoir is as large as the maximum amount of propellant needed for one manoeuvre.


The filling of the PRR and allocation of the liquid has been analyzed in the drop tower in Bremen.

To demonstrate the overall function of the PMD a further experiment was carried out on a sounding rocket with a 3.7 min. period of microgravity. The experiment demonstrates that even at low fill levels of the tank the reservoir will be filled. The displaced gas escapes via a funnel - shaped outlet at the top of the PMD.

Refilling of the PRR – side view ClickToPlay
Refilling of the PRR – top view ClickToPlay