Isar Aerospace: Electrical Engineering in rocket construction

Missile tests: No lift-off without control cabinets

To ensure that everything runs like clockwork on future missions, the tests and validations of every component and part are of great importance. Each test stand has programmable logic controllers and individually configured control cabinets. Their size varies depending on the requirement. Small boxes measuring 30×30 centimeters are sufficient for testing subcomponents such as valves or batteries. To validate a rocket engine, however, larger test facilities are needed, such as those at the Esrange Space Center, located near the northern Swedish city of Kiruna. There, the development engineers at Isar Aerospace work with an entire network of different control cabinets that communicate with each other. In addition to PLCs, 24V power supply units, contactors, relays, frequency converters, motor controls and lots of safety technology are installed. „In 2021 alone, we designed more than 20 control cabinets and built them ourselves,“ reports Marc Rötzer, electrical designer at Isar Aerospace. Trend: still increasing.

Isar Aerospace’s electrical engineering department can only manage this output because it uses a professional electrical CAD application. The five-man team creates all circuit diagrams with WSCAD’s Electrical Engineering Software. In addition to some standard circuits, many individual developments have to be taken into account on the test stands. Macros speed up the design and help to avoid mistakes at the same time. As soon as the circuit diagrams have been drawn up, the WSCAD Cabinet Engineering module is used to construct the control cabinet. At this stage, it is already clear where which relays are located, which fuses have to be installed later and where top-hat rails and cable ducts run. Drilling data for metre goods such as mounting rails can be easily configured via dialog.

3D visualization for more planning reliability

The software also helps to place individual components for the later production of the cabinets right or left side flush to an accuracy of tenths of a millimetre. The calculation of wire lengths including routing during the planning phase provides a noticeable productivity boost in the work processes. The filling degree of the cable ducts is also immediately visible. In the 3D view, components are checked for collisions using native 3D data based on actual component dimensions. You can quickly determine whether the cupboard doors are closing properly or not. In addition, the 3D control view with photorealistic images provides a better spatial overview.

Without additional software and costs, the control cabinet data generated in WSCAD can be exported via interfaces, for example to label terminal strips from Phoenix Contact. With several hundred terminal markings, this saves an immense amount of time and avoids manual errors. „We can’t and don’t want to do without such features any more,“ says Marc Rötzer. Wiring is currently still done exclusively on the basis of the circuit diagrams. „But we will soon be testing and using the Cabinet AR wiring app included in WSCAD.“

The Isar Aerospace designers obtain the empty control cabinets prefabricated with cut-outs for ventilators and holes for the operating elements. Assembly and wiring are carried out internally for quality assurance reasons. At the Ottobrunn site near Munich, cables and components are available for this purpose in a specially equipped electrical warehouse.

Professional turbo training: mix of theory and practice

When Isar Aerospace launched in 2018, every electrical engineer in the company had experience with a different electrical CAD software. The team therefore put the different solutions to the test and evaluated the scope of services and costs. At the end of the selection process, three applications were shortlisted – the decisive factors for WSCAD were functionality and purchase price. A decision that no one has regretted from day 1.

Because time is an important success factor for any start-up, the introduction of WSCAD also had to be as quick and efficient as possible. Isar Aerospace completed a modified 5-day training course attended by all electrical engineers and also the PLC planners and programmers. In contrast to the usual training courses, many standard circuits were also created and saved as partial circuits in the form of macros. For example, for the PLCs, the article data stored in WSCAD by Isar Aerospace’s preferred PLC manufacturer did not exactly match Isar Aerospace’s requirements. They were easily changed during the training and saved as new item data and macros for quick use in the future. The training with its coordinated mix of theory and practice helped all course participants to use the many functions of WSCAD quickly and optimally right from the start.

After this dream start, Isar Aerospace is currently expanding its electrical engineering department and is looking for new colleagues. Jobs await you in an extremely exciting technical environment where you get to see a lot – from the very first planning, the preliminary discussions with the engineers, to the construction and subsequent installation, right through to the start-up.