Basic ideas

Basic requirements and ideas for the mechanical design are

  1. the antenna is deployed by a single command to a pyro-device to cut a wire (or during ground test this wire can be cut with a wire-cutter). This pyro-wire fixes the antenna in the folded position (launch position). After the wire has been cut the antenna deploys automatically in a controlled manner;
  2. once released, the deploying forces acting on the antenna are 'much 'larger' than the opposing friction forces; but small enough to avoid a collision of the antenna with the spacecraft during deployment;
  3. deployment forces are provided by spring forces; no motors are involved;
  4. two deployment indicators signals the successfull deployment;
  5. once deployed the antenna structure will lock-on, such as to be unaffected by normal forces associated with orbiter maneuvers.

    6. Two masts supports the antenna elements. The masts are of carbon fiber material covered by plasmocer traited aluminium foil. The springs that deploy the masts are Carpenter-Springs. The Carpenter Spring connects the two masts, and another spring connects the end of one mast to an antenna foot, that is bolted to the spacecraft. In folded position the masts are parallel and placed along a spacecraft edge. When the antenna is released the Carpenter Springs go into action. The Carpenter Spring, when straightened out, is in an equilibrium position, where a large force is needed to bend the spring. This provides for stability of the deployed antenna. The stability is further enhanced by the manchets 'which are pushed across the Carpenter Springs to lock against the support structure.

    The antenna- and reflector elements are aluminium rods with a surface of plasmocer. Each dipole element is connected to one of the masts with a spring. When the antenna is the folded position, then each dipole- and reflector element is folded back along the mast to which it is attached, and kept in place by a 'manchet'. When the antenna deploys the manchets are pushed back to release the elements, which are deployed each by the spring. Each of these springs has the form of a coil. inside each springs is a latch, which locks on when the spring has straigtened out, thereby fixing the elements in the wanted position.

    The antenna is kept in launch position, (folded position) by three supports and is lashed to the central support with a wire. The wire is cut by a pyro-device to deploy the antenna.

    An initial push to the masts to deploy is provided by springs located in the central support.

    The controlled deployment of antenna- and ground elements are basically provided by spring action.

    Each carpenter-spring is supplied with an Ohmic resistor (r), Deployment Indicator, to provide a deployment check:

    Folded antenna: R<50 OHm.
    Deployed antenna: R>1MOhm.