Space Relays Failures Occurring & Lessons Learnt at ESA

source: ESA ESTEC; ESA SPCD 2018 Symposium

EPCI e-symposium library article

ESA component engineers Dr.Denis Lacombe and Dr.Léo Farhat are introducing their presentation on space relays failures and lessons learnt.

published by EPCI under approval of ESA SPCD 2018 organizing committee.

Title: Relays Failures Occurring & Lessons Learnt
Author(s): Dr.Denis Lacombe and Dr.Léo Farhat
Organisation(s): ESA ESTEC, The Netherlands
Symposium: ESA SPCD 2018
Reference: Lessons Learned and In-flight Experiences
e-Sessions Applications: Aerospace
e-Sessions Scope Components: Relays, Inductors
e-Sessions Topics: Technology, Materials, Quality & Reliability


“An electromechanical relay is an electrical switching device. Its function corresponds to a mechanical switch, which is electrically actuated. The main advantages of electromechanical relays are the electrical isolation of the driving system and the load side, the insulation resistance of open contacts, as well as the low resistance of the closed contacts.”

Contact Material
The choice of the contact material depends on the switching capability of the relays. In general, a trade off is made between low resistance material and abrasive resistance. In space application, contact are usually made with silver for low current, silver oxide for high current and tungsten for high voltage.
Tuning and arcing
The settings of the relays are based on the Holm curves and take into account several elements like the contact materials, the contacts gap, the internal gas inside the cavity, the pressure, etc.
Relay Failures
High voltage relay: increase of latch voltage
Actuator side not in hermetic package then vacuum may induce displacement but also cleaning process may cause damage to the gel.
Failure analysis
Failures’ analysis of relays are tricky
  • Complex device with many pieces’part (40 to more than 100)
  • Risk of losing the defect
  • Interest of new methods (Xray, tomography, FIB)

Root cause of observed failures

On 13 observed failures:

5 (≈40%) of the observed failures may have been avoided if better knowledge of relay was used.

… see more at the full presentation link below…


ESA alert recommendations

New procurement of ESCC qualified TL26 relays:

Lesson learnt and recommendations

see the full presentation here:






Exit mobile version