It's not rocket science...or is it?

Motes have been launched into a new dimension. Researchers at NASA Ames Research Center have taken the capabilities of the MICAz Mote platform and sent them to a new level...literally. Wireless sensor networks and Motes are used to monitor environments or objects to detect changes and provide information or alerts about the current configuration in real-time. This time Crossbow's MICAz Mote platform was used in a rocket engine monitoring system.

Unlike most mechanical systems, rocket engines rarely fail gradually. It's not like having your brakes wear out in your car where you can feel the brake pads getting warped. In a rocket engine, if something fails, it happens quickly making it difficult to determine the root cause or to do anything to avoid the failure. When a rocket engine does malfunction, sensor data provides important clues about the cause. The vehicle health monitoring system relays pressure, temperature, voltage, strain and acceleration data back to the Mission/Launch Control Center. Integrated Vehicle Health Monitoring (IVHM) goes a step further by providing onboard processing capability often detecting engine anomalies earlier and responding faster than a ground-linked system.

The goal of the IVHM project is to replace the standard MIL-STD-1553 databus with an 802.15.4 wireless link between groups of sensors and the Stargate flight-data-recorder. The system was used as a platform to demonstrate intra-vehicle wireless transmission and power management software for long duration missions.

The system used wireless pressure sensors with 1 mounted on the engine chamber and 1 on the fuel tank. There were 4 wireless accelerometers distributed through the vehicle and 2 thermocouples for each fuel tank. All the sensors were connected to a MICAz Mote platform as they were able to provide power/control to the sensors. The sensors transmitted their data to the flight-data-recorder based on Crossbow's Stargate platform over the 802.15.4 link as it interfaced with the MICAz. Before the flight test, the equipment was vibe tested to 6.5g rms for 30 seconds on the X, Y and Z axes to mimic the conditions during the space shuttle launch. A piezoelectric buzzer was attached to the Stargate and each sensor board to easily perform diagnostics at the test range. To optimize power management the MICAz Motes were set to go into low-power mode when the flight-data-recorder was powered off and the Stargate was modified to generate a periodic heartbeat data packet. When the MICAz radios did not see the heartbeat they would go into a low-power watchdog routine.

The IVHM system first flew last September onboard the Garvey Spacecraft Corp's P-8A rocket in Mojave, CA. This engine monitoring system is an advanced concept demonstrator for a wireless 802.15.4 databus where stage-separation makes traditional bus architectures difficult. Motes have been used in many environments for many different monitoring requirements but this deployment certainly reached new heights!