The RWSS reaction wheel consists of a momentum wheel mounted on a brushless DC motor and enclosed in a mechanical housing. The mechanical housing had to be sealed to maintain atmospheric pressure inside, to protect the lubricant of the wheel bearings and so ensure an operational lifetime of at least fi ve years.
The design team needed to find a way to connect the wires of the brushless DC motor inside the housing to the external reaction wheel drive electronics without compromising the pressure seal. Experience had shown them that from a starting internal pressure of 1atm, the end-of-life internal pressure needed to be at least 0.1atm after fi ve years as this is
the minimum required to maintain the lubrication.
The SunSpace design team selected the Martec 5425-14-19-PN hermetically sealed MIL-DTL-26482 circular connector (19-way male jam nut) for the task. They built a qualifi cation model of the reaction wheel using the Martec connector and subjected it to a range of product level and system level environmental tests.
The tests verified that the leakage rate met the specification and that the seal would not be compromised by the launch and orbit environments.
A satellite fitted with three RWSS reaction wheels, each using the Martec hermetically sealed connector, was launched in the first half of 2007.