European Space Agency

Alphasat TDP#7: 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 the 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.

PCB?s Pressure Transducer Fluid side Fill/Vent Valve 3-way valve Pump Loop Cold Sink DC/DC converter Accumulator 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.

Preliminary 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 to 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 in-orbit demonstrations 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 preliminary MPFL-FX design will be established in order to define the feasibility of the experiment in terms of accommodation on the @SAT.  Furthermore a set of preliminary requirements will be established at the MPFL-FX phase A study.

For the MPFL-FX Phase A study the following plan is applicable:

Task 4 reviewT0+1.5m
Task 6 reviewT0 + 3m
Preliminary requirements reviewT0 + 6m

Current status

A preliminary design has been established, providing a mass budget < 10kg. From the accommodation review, it has been decided to propose a number of variants, which increase the feasibility of the MPFL-FX accommodation. These variants are briefly described in the latest issue of the ICD and are currently detailed as input to the refined ICD (to be issued beginning of June 2006).

The Phase A study has been successfully closed. However, due to the high launch costs, there were not sufficient funding for a phase B/C/D continuation. Therefore several alternatives will be investigated to fly the MPFL technology at lower costs within the next years.

Status date

Tuesday, October 28, 2008 - 13:37