scope:

Description of Driving Event:

Non-flight test heaters located on each of the three non-flight, inert TIRS (Transverse Impulse Rocket System) motors were powered during system thermal test of the Mars Exploration Rover (MER 1) to accelerate return of the test chamber to ambient conditions. Post-test inspection of the TIRS assembly revealed that the heaters had burned through the heater Kapton insulation (Figure 1) and severely damaged the surrounding flight MLI (multi layer insulation) blanket (Figure 2) on all three units.

The failure was caused by the lack of a current limit specification on the controlling GSE (ground support equipment) power supplies. Test temperature sensors were located 4-5 inches from the heater; this was too far away to detect the high temperature due to the low thermal conductance of the TIRS motor case.

The only flight hardware damaged by the test heater failures were the three flight TIRS MLI thermal blankets. These were refabricated because failure to correct the damage might have been mission catastrophic.