European Space Agency

Mechanically Pumped Fluid Loop


The MPFL project objective is aimed to provide a European supply for equipment for a Single-Phase Mechanically Pumped Fluid Loop. The purpose of the project is to perform all design and development activities in order to qualify European single-phase cooling loop equipment (pump package, By-pass assembly, connectors and coolant fluid) that could potentially be used as heat transfer device for the @BUS Deployable Radiator compulsory for the extended payload power range of @BUS.

The main requirements are as follows:


  • Heat to be transported: 3 kW, to be rejected via two 4,5m² dual active faces Deployable Radiator (DPR), with less than 30°C increase of fluid temperature;


  • Piping length PHX 70m and RHX 90m;


  • Lifetime >15 years.

MPFL Qualification Model Hardware (Pump Package)
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  MPFL Qualification Model Hardware (Bypass Assembly)
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In view of supporting the @BUS Deployable Radiator (DPR) system level trade-off, relative to a single- or two-phase cooling system, a dedicated DM level fully redundant Mechanically Pumped Fluid Loop are prepared and tested according system level requirements.

Besides this primary objective, some additional analysis and design tasks are carried out in order to define the Thermal Control algorithm and design an @BUS-compliant MPFL.


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 15 years and successful flights on multiple space missions.


The team selection is based on the synthesis of expertise in the fields of the most stringent MPFL requirements and uses acquired knowledge out of past co-operation and space programs to its best. Special emphasis is spent to create a modular pump package design, which can be used for a variety of applications within a 3 to 6 kW payload range, hence is compatible with a variety of coolants. As a result of this approach, the qualified equipment will be suitable for multiple applications, using the latest state-of-the-art technology. Furthermore, recurrent costs will be kept competitive.


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  Referring to the figure at left, parts of the @Bus satellite Payload dissipates its heat into the Payload Heat Exchanger (PHX). The Radiator Heat Exchanger (RHX) will provide heat rejection from the coolant to the external environment.

The By-pass Valve regulates the flow through the RHX branch. This 3-way valve can be put in a position between 0 and 100%, whereas the pump package provides an almost constant fluid flow through the PHX branch. The inputs for the temperature control are the Pump Inlet Temperature and the on-ground settable temperature value.

The pump package also provides failure detection information to the ground via the data bus. The pump package interfaces with the satellite power bus, data bus, the rest of the cooling loop and ground support equipment for integration and test activities.

The pump package includes the following items:

  • Two parallel redundant BLDC motor driven centrifugal pumps,
  • Electronics for pump motor driving and speed control and for the monitoring equipment,
  • A fluid accumulator for compensation of fluid expansion,
  • Isolation valves for selection of active/redundant branch,
  • Flow, Temperature and pressure sensors.

The by-pass assembly consists of two redundant Flow Control Assemblies (FCA) for adjustment of radiator flow rate between 0 to 100% of the pump package fluid nominal flow rate. This is achieved by a stepper motor driven 3-way valve equipped with a position sensor and passive end switches for housekeeping data.

Qualification Model Pump and By-pass 3 way-valve Close-up

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PHX and RHX are not in the scope of the MPFL development program.


The activities performed under the project will be organised in three phases as follows:

  • Phase 1: Trade off analysis and Preliminary design of single-phase loop equipment,
  • Phase 2: Development and validation of the single-phase loop Components,
  • Phase 3: Qualification of the single-phase loop components.

During phase 1 the preliminary pump design has been verified at BBM level in order to obtain valuable performance parameters for the DM and QM design phases. In phase 2, main objective is to prove feasibility of the design concept to meet the MPFL requirements at DM level. The formal qualification during phase 3 is divided into 2 parts: Part 1 encompasses full qualification of the loop design and in part 2 of the qualification an accelerated life test of minimum 12 months will be performed.

The main CCN2 activity is the system-level characterisation tests of MPFL (with focus on the Control Law) supported by the development of an ESATAN/FHTS Thermal Model of the MPFL including the two DPRs. For model correlation a dedicated test bed will be built, including full scale RHX and PHX simulators. By use of the (dynamic) Thermal Model, the MPFL control algorithm will be determined.

Furthermore a number of additional Design and Analysis activities are performed in order to ensure an @BUS-compliant MPFL (out of scope of the nominal MPFL pre-development contract).

Current status

The nominal contract has been successfully completed.

As a phase 1 activity, trade-off of the loop design, coolant, operating points and the individual components has been performed. PDR was successfully closed and phase 2 was started mid 2004. The Development Model hardware has been manufactured. First results show compliance with the performance requirements. The DM test campaign, including environmental and loop performance tests, were finished May 2005. TRB has been held successfully.

The CDR has been held successfully. The phase 3 has been started on 9 June 2006, authorizing the manufacturing of the QM MPFL. After manufacturing and assembly of the MPFL QM Hardware the QM TRR has been held in February 2008.

After completion of the assembly level tests, the first part of the TRB was held in February 2009. This milestone also depicted the start of the life-test. The total duration of the life-test is 1 year. The pump has successfully performed 600 on/off cycles in a temperature range of -40°C to +70°C. The 1 year life test for the complete loop has been completed. The pump has run without any anomalies and it has been confirmed that with a minor modification, the Three-Way Valve can meet the 104.000 open/close cycles.

MPFL QM Life-Test Test Bed

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Final TRB has been successfully held in September 2010 and Contract Close-Out is expected end of 2010.

An extension of the life test of 2 years is foreseen to accumulate confidence and running hours in the pump within a representative loop.

Kick-off was held in December 2005. Hardware manufacturing and Pre-analysis with Dynamic Thermal Model have been finalized. The CCN2 test campaign has been successfully finalised and the TRB has been held in October 2006. The CCN2 close-out was held in May 2007.

MPFL Development Model (DM2) Test Bed

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Status date

Monday, November 22, 2010 - 18:38