Patch or polyimide heaters can be used in custom shapes for space travel, however hermetically sealed cartridge heaters are often used to heat blocks of material or components requiring high temperature. Monopropellant rockets depend on the use of a wire-wound resistor enclosed in a metallic sheath using a ceramic insulator for dielectric strength. A reamed hole is then typically drilled into the rocket engine component and a clamp or flange is welded on to the sheath of the heater.
The BCE Hem Sealed Heater™ incorporates both the cartridge heaters’ wire wound resistive element encased in a metal sheath and the vacuum compatibility of a feedthrough. Furthermore, the BCE proprietary epoxy seal allows the heater to pass strict electrical tests ensuring the purity of the dielectric materials and hence, preventing shorting. The BCE Hem Sealed Heater™ outperforms as heat flows uniformly from inside the cartridge directly to the heated bodies.
Controlling the heater typically falls to the command of the either a thermostat or solid-state relay turning the heater on when needed at temperatures that have been determined prior to the rocket launch. Satellites control heaters using an onboard computer to monitor temperatures turning them off and on at the optimal time. A common use is heating up a catalyst bed on a monopropellant thruster to around 100°C prior to the rocket engines being engaged.
Most applications utilizing the Hem Sealed Heater® also require an automatic control of the heater to allow the unit to maintain the desired temperature. Mechanical thermostats are the most common device, which can be incorporated into the Hem Sealed Heater® using additional metallic tubing and hermetically sealing the control section with BCE’s proprietary epoxy.
The spacecraft heater application will be solved utilizing one interconnected component set at the optimal temperature. Ask BCE to assist in your rocket engine design.