European Space Agency

Mechanically Pumped Fluid Loop Flight eXperiment


A Mechanically Pumped Fluid Loop loop Flight Experiment (MPFL-FX) is proposed to be flown as Technology Demonstrator Program (TDP) on the Alphasat mission.

Under ARTES8 PP17.2 pre-development Bradford Engineering is developing and qualifying the single-phase cooling technology for the Alphabus platform.

As the TDP possibilities did not allow to fly a full-sized MPFL with deployable radiator (DPR), it is proposed to fly the most critical components of the MPFL technology (e.g. the pump, the by-pass assembly, the reservoir, the control electronics and the cooling fluid) in a scaled-down version of the originally foreseen full size loop on-board Alphasat (without the large deployable radiator).

The main MPFL-FX objective is to carry-out the on-orbit life testing of the MPFL components in order to increase its acceptance with respect to future customers. The foreseen on-ground accelerated life tests on the mechanical components and on the fluid are still subject to numerous discussions. Furthermore, the MPFL-FX will provide in-orbit verification of microgravity and radiation effects.

The TDP is designed as a experiment box and E-box with very simple mechanical and electrical interfaces and minimised interaction with the satellite. This “piggy-back” approach will enable in-orbit life test of the components of the MPFL without any impact on the other Alphasat payload in case of MPFL failure.

MPFL-FX design

click for larger image


The main issue in the project is the pump, which is the “heart” of the MPFL. As the @Bus reliability and lifetime requirements (i.e. 15 years) are extremely severe, this puts highly challenging requirements on the pump design (bearings, motor).

The baseline selected MPFL pump is a design with a demonstrated accelerated life test for over 11 years and successful flights on multiple space missions. Furthermore, the selected coolant is a fairly new engineering fluid that finds its first space application in the MPFL.


The MPFL provides a modular single-phase cooling loop design, which can be used for a variety of applications within a 3 to 6 kW payload range. As a result of this approach, the qualified equipment will be suitable for multiple applications, using the latest state-of-the-art technology. This comprises not only telecom spacecraft, but also e.g. planetary missions.

The Alphasat Flight Experiment will provide essential on-orbit demonstration of the most critical technologies.


With reference to the depicted diagram, the MPFL-FX (scaled-down MPFL flight experiment on-board Alphasat) consists of the following components:

  • Pump and Motor (without redundancy)
  • Accumulator
  • 3-way Valve with position sensor (without redundancy)
  • 2 Pressure transducers
  • Integrated Electronics (instead of separate Pump Package and By-Pass Assembly E-boxes)
  • Connecting tubing
  • Coolant
  • 2 Fill and Drain Valves
  • Several temperature sensors
  • Loop Cold Sink

Scaled-down single-phase MPFL (no redundancy) without PHX (no heaters on MPFL tubing) with fixed radiator (no deployable radiator) as RHX

click for larger image


The MPFL-FX design is established in order to define the feasibility of the experiment in terms of accommodation on the @SAT. Analyses have been made to justify the design and compatibility with the @SAT requirements.

Current status

The Phase A and Phase B0 study were successfully closed in July 2009. Unfortunately, this Technology Demonstrator Program has not been selected to be flown on-board Alphasat. Other opportunities on-board other satellites are currently being investigated.

Status date

Wednesday, October 28, 2009 - 13:55