SunSpace and Information Systems (Pty) Ltd builds small and medium sized satellite systems for the international market. The company had designed a reaction wheel (the RWSS) to control the orientation of a satellite in the vacuum of space, and needed a way to connect the electronics from the motor inside the housing to the external drive without compromising the pressure seal.
Advanced production and sealing
Design team support
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.
The assistance provided by Martec during the project was invaluable. Their prompt service enabled us to arrive at a solution within the short time scales of our project, and their advice on the type of vacuum grease to use and how to prepare the contact surfaces to ensure proper sealing was much appreciated. Martec was also most helpful in scheduling the manufacturing of the connectors, which are usually only manufactured to order.Sunspace