TABLE OF CONTENTS Heaters are resistor elements that generate heat ( I 2 R dissipation) when an electric current passes through them. They have been a standard fixture in satellite thermal systems since the early days of the space program, and it is not unusual that experimenters and subsystem engineers supply them as integral elements of their equipment. Their main function is to maintain components' temperatures above critical values, but they are also used to warm up dormant electronics prior to activation, to control temperature differences for enhanced dimensional stability, and as dissipators of excess satellite power.
Patch heaters are the kind used most often. They consist of etched foil (electrical resistance elements, such as Nichrome) bonded within two thin sheets of a flexible insulator (75-125 ?m Kapton is common), which can be made into various shapes and sizes, including long narrow strips. A typical patch is shown in Fig. 6.46. The wiring is often two or more independent elements for redundancy or varied heating levels. Standard installations use film adhesives to bond the heater on the intended surface, and sometimes clamps or screws are added to secure the corners against lifting.
Shunt heaters, in the shape of cylindrical cartridges of wound resistors encased within metallic housings (usually about 0.5-cm diameter and various lengths), are sometimes used in regions of high temperatures, where adhesive bonds are not reliable. The cartridge (on right in Fig. 6.46) is normally potted...
