Image: ESA

From the lathe to space

In the engineering workshops at DTU Mechanical Engineering, the two foremen Torben Bender Christensen and Jan Frank Pedersen have produced parts for the magnetometer and space telescope now mounted on the Swarm satellites that were launched into orbit around the Earth in November 2013.

Magnetometer to measure the Earth’s magnetic field

The vector magnetometer was used for the first time on the Ørsted satellite in 1999, having been developed through a working relationship between researchers from various departments and engineering workshops at DTU. On board the current satellites, it will be used to measure the Earth’s magnetic field. The measuring instrument will subsequently have a role to play in connection with missions to Mars and Jupiter.

The purpose of the measurements from the vector magnetometer is to acquire more knowledge about the core of our planet. The Earth’s magnetic field is generated in the fluid, outer layer of the core, and currents in the core make it possible to register changes in the magnetic field. Measurements of the magnetic field can also be used to help identify deposits of raw materials such as oil.

 

How the magnetometer shells were made

Torben Bender Christensen explains that the first step in the process to produce the shell sections for the magnetometer—a male and a female part—involved making a cast in araldite mixed with small glass beads to boost the strength of the material. The casting itself was carried out in a vacuum to remove the air pockets that can otherwise easily form during the process. The choice of material was crucial with regard to the quality of the measurements. “It is essential to place the measuring equipment in a non-magnetic material so as to prevent disruptions, static and incorrect measurements,” relates Torben Bender Christiansen, who made the shells in the engineering workshop with the assistance of Allan Martensen. Following the casting process, direction holes were drilled in the units to allow the subsequent milling of the grooves. The grooves are for the vector magnetometer’s copper coils that were installed at DTU Space—the department responsible for all the assembly work. The people who have made units for DTU Space are: Torben Lund, Søren T. Hansen and Arne Kronborg. Jan Kleeberg from DTU Space has acted as ‘anchor man’ for the project.

 

Skallerne til magnetometeret
 The magnetometer shells were made in Torben Bender Christensens workshop.

 


Star camera for the new satellites

Jan Frank Pedersen, foreman in the engineering workshop in Building 427, was responsible for making several components for the star camera that is now aboard the SWARM satellites. The housing for the star camera is made of titanium. The workshop also cast the baffles that keep the star camera stable. The satellites use the camera to navigate according to the position of the stars—so it is essential that it remains stable. The star camera itself was developed by DTU Space, just like the vector magnetometer.

 

On a mission for ESA, the European Space Agency

Both the vector magnetometer and the star camera are now mounted in the SWARM satellites. The satellites were launched on 22 November 2013 and the equipment is functioning impeccably. The three satellites are operating in unison to measure the Earth’s magnetic field. Using three satellites to take measurements increases accuracy ten-fold in relation to the performance of a single satellite.
The Swarm mission is run under the auspices of ESA, the European Space Agency.

SWARM satellit
 SWARM satellite. Image: ESA.

 

Facts:

 

CNC milling or lathing as a production method

In a CNC milling machine or lathe, the programming defines how the unit is processed. In this context, CNC stands for Computer Numerical Control. For the actual machining of the unit, the operator plans the process in a CAM—Computer Aided Manufacturing—programme. This is generally based on the design outline prepared using CAD (Computer Aided Design). When refining the design outline for the unit in the CAM program, the operator defines aspects such as the tool tracks it will be most appropriate to use. Decisions in this context are made on the basis of factors such as the stress lines of the material, which are of importance to how the unit will behave during processing. The shells for the vector magnetometer are CNC lathed and then milled manually using a special tool head.

 

One of the major benefits of CNC milling and lathing is that the system allows the application of much more stringent requirements on surfaces and tolerances than other production methods. CNC milling and lathing also allow the production of units with geometric shapes that it would be impossible to make using other tools.

 

 

Contact

Torben Bender Christensen
Head of Workshop, Precision Mechanic
DTU Mechanical Engineering
+45 45 25 62 18

Contact

Jan Frank Pedersen
Head of Workshop
DTU Mechanical Engineering
+45 45 25 48 63