Tech Briefs

Autoignition Chamber for Remote Testing of Pyrotechnic Devices

This rugged, reusable chamber is portable and can remotely heat pyrotechnics for autoignition tests.

The autoignition chamber (AIC) performs by remotely heating pyrotechnic devices that can fit the inner diameter of the tube furnace. Two methods, a cold start or a hot start, can be used with this device in autoignition testing of pyrotechnics. A cold start means extending a pyro - technic device into the cold autoignition chamber and then heating the device until autoignition occurs. A hot start means heating the autoignition chamber to a specified temperature, and then ex - tending the device into a hot autoignition chamber until autoignition occurs. Per - sonnel are remote from the chamber during the extension into the hot chamber.

The autoignition chamber, a commercially produced tubular furnace, has a 230-V, single-phase, 60-Hz electrical supply, with a total power output of 2,400 W. It has a 6-in. (15.2-cm) inner diameter, a 12-in. (30.4-cm) outer diameter and a 12-in.-long (30.4-cm), single-zone, solid tubular furnace (element) capable of heating to temperatures up to 2,012 ºF (1,100 ºC) in air. The furnace temperature is controlled by a commercial single-zone, setpoint temperature controller and solid-state relay.

The furnace features a stainless steel shell with 1/4-in.-thick (6-mm) steel end plates, and a rugged insulation package. A thermocouple port is supplied in the center of the control zone. The furnace has a 2.5-in.-long (6.4-cm) vestibule at the top and bottom. The approximate overall length of the furnace is 17.5 in. (44.5 cm). Thermocouples on the pyrotechnic device monitor its temperature during the heating process on a strip chart recorder, or an equivalent data acquisition system. A remotely actuated ceramic protective cover is installed on top of the auto ignition chamber when test personnel are working around it.

A cage is mounted to a 115-VAC 500-lb (2,224-N) force electromechanical actuator that has an 18-in. (46-cm) stroke. The pyrotechnic device is installed in an appropriate mounting fixture, which is then installed in the cage. The actuator can be remotely operated to extend or retract the pyrotechnic device into the tube furnace. When the actuator is completely extended into the autoignition chamber, a ceramic insulating lid sits on top of the chamber to keep heat from escaping.

An accelerometer is installed on the stainless steal fixture of the electro-mechanical actuator to record the autoignition event. A strip chart recorder, or equivalent data acquisition system, monitors the accelerometer output. The chamber is capable of withstanding stress while still being able to function. In one instance of STS-107 Pyrotechnic Hardware, the autoignition chamber was reused a total of 18 times and did not require rebuilding.

This work was done by Maureen L. Dutton, Richard J. Dean, Douglas W. Harrington, and Gerald R. Steward of Johnson Space Center and Toby W. Dartez of Jacobs Sverdrup Corp. For further information, contact the JSC Innovation Partnerships Office at (281) 483-3809. MSC-24433-1