Hold-down & release mechanisms (HDRM) for ground testing

Space Hold - down & release mechanisms are usually extremely reliable.  The price for such reliability is very frequently a disposable design. That puts a very high additional refurbishment costs on the development process of the mechanisms based on such HDRM’s.

To reduce the development costs of space mechanisms, LKE (in cooperation with Frentech Aerospace) developed fully resettable and reusable simulators for ground testing of space mechanisms.

Advantage of our solutions for gorund testing are lower development costs, full resetability without a need for disassembly and high reliability due to manual release.

The need for storage of high deformation energy coming from substantial pretension in a small volume – and yet to ensure minimal possible energy needed for actuation - is a great challenge in the design of actuators. Combining analytical and finite element calculations, sufficiently robust but simple system for release of the different values of pretension was found.

Type RMT 2M was designed for mechanism tests with the requirement of low pretension – up to 2500 N. Actuator itself is resilient to actuation by accidental shock and is equipped with safety screw. The head of the inner pin is shaped to provide a tilt of the pretension bolt thus reducing the additional bending stress on the bolt. Material and surface treatment are chosen specifically to allow the parts to withstand high contact pressures inside the actuator mechanism.

Simulator was successfully tested and applied in the development process of hold down and release mechanism of radar antenna for interplanetary scientific probe.

Significantly higher pretension is necessary for applications such as HDRM of multi-segment solar arrays. Type RMT 50M, based on different approach of inner force transmission, was developed for pretension up to 50 000 N. Shape of the contact surfaces was optimized using finite element calculation to achieve uniform distribution of the contact pressure and reduction of the outer envelope.

Both designs can be equipped with metal segment guidance of the actuation cable which extends the usability temperature range. In both cases, interface hub and inner thread can be customized.