Application Note...

PCS400 Pressure Calibration System

Application:

Calibration of sensors used on the space shuttle's solid rocket boosters (SRBs) to determine altitude for parachute deployment.

Challenge:

One of the primary contractors to the US Space program has the responsibility of designing and providing a solution for the recovery of the SRBs used in the launch of the space shuttle. The space program is an extremely expensive program and efforts have been targeted toward reusable components where possible and where safety will not be impacted. The SRBs are jettisoned when their fuel supply has been exhausted. In earlier space programs, these components were allowed to splash back into the ocean and no effort of recovery was considered. In order to make recovery possible, the SRBs have been fitted with parachutes. Deployment of the parachute has to be timed such that they can be recovered. Pressure sensors that determine the altitude of the SRB accomplish this. At predefined altitudes, the sensor triggers a mechanism that deploys the parachutes. The sensors have to be calibrated precisely to prevent premature or late deployment, both of which can produce disastrous results.

Solution:

Mensor supplied (2) PCS400 Pressure Calibrator Systems with ranges of 0-16 psia and an accuracy of 0.01% of full scale. Also added was an optional TTL level interface and software modifications to provide a discrete logic level signals to interface with existing test equipment. The same system is utilized to perform pressure leak testing to check the o-rings in the modules. A typical leak test is performed at 4 psia for 5 minutes.