SQUID experiment

Mechanical design

The SQUID experiment consists of two main parts, the Rocket Mounted Unit (RMU) which is basically its interface to the rocket with several electronic systems, a camera and the ejection system, and the Free Flying Unit (FFU), which unlike the RMU will be separated from the spinning rocket.

The outer design of the SQUID experiment is constrained by the interface to the rocket, which limits the diameter of the experiment and also its shape, as the experiment has to be placed between the piping for the ejection mechanism of the nosecone (see figure on the left).

As the FFU needs to fly as stable as possible (with minimum precession and nutation angles) its height is limited by the dynamic stability. After separation from the rocket the spinning FFU can be compared to a Frisbee which means it has to be as flat as possible to make it fly as stable as possible. 

FFU

Free Flying Unit (FFU)

The most complex element of the experiment is the FFU. It needs to house the four wire boom deployment mechanisms (SCALEs), the landing and recovery system as well as the electronics and sensors controlling the experiment. The outer structure  of the FFU consists of the bottom plate, eight wall elements and a top frame giving the FFU its octagonal shape. The top plate, which is placed on top of the frame, is ejected during the landing phase in order to activate the landing system.

 

The electronics box containing the electronics, power system and several sensors is attached to the bottom plate through four PEEK blocks, providing thermal insulation during reentry. The four wire boom systems are also attached to the bottom plate, placed in diametrically opposite directions in order to keep the FFU stable during the deployment of the wire-booms. An overview of the FFU and its components can be seen in the figure on the left.

Rocket Mounted Unit (RMU)

The disc underneath the FFU contains all the components of the RMU, including connectors supplying power to the FFU, electronics for converting the power and relaying signals from the rocket service module, a camera which records the FFU ejection and the FFU ejection system.

The FFU has to be ejected slow enough not to catch up with the nose cone, but fast enough so that is isn't caught up with again once the motor ejection pushes the experiment module section forward. To do this, a powerful custom-made spring from Lesjöfors is used, giving an ejection speed of about 3 m/s. The Free Flying Unit is held down against the spring using a wire, which is cut with a small pyrotecnhic wire cutter when the experiment is to be ejected. The picture on the left shows a photo of the RMU, with the spring in place and the brass pins in the middle to achieve the electrical connection between the rocket and the FFU.