how to design satellite model in simmechanics...?

a simple box model of satellite with 3 reaction wheel.. requirment-1.. satellite should be floating in space... requirment-2.. wheel and body should have angular momentum coupling.. ie if wheel is rotated in some direction then body has to rotate other direction.. question is " how to configure momentum coupling in sim mechanics ?? " and "how to make satellite body floating in space ?? " i have develop satellite model in solidworks..and imported to simulink ... used matlab2009a