3D printed parabolic dish actuator

DREX: deployable antenna technology for spacecraft telecommunications

Solid dish antennas are an extremely common technology used for spacecraft telecommunications thanks to their heritage and reliability. Launching a spacecraft with a pre-deployed solid dish is rarely possible, though, due to volume and mass limitations so another solution is sought: the deployable dish antenna. Deployable structures combine the features of a solid dish antenna with a much-reduced volume and many different types of systems have been used over the years.

The DREX telecommunication system (Deployable Reflector EXperiment)  is a novel design developed by an aerospace engineering research group at the University of Padua, of which Vittorio Netti, Roboze Application Engineer, was part. These project sought to overcome the limitations of current deployable antenna technology by featuring a parabolic reflector that extends its surface through a radially opening, umbrella-like mechanism.

How does DREX telecommunications system work?

The mechanism is actuated by a single system which moves the arms, multiplying the reflector area by nine times compared to its stowed configuration, the deployment sequence is shown below. The deployment arms are connected to a pre-charged, spring-loaded mechanism that is constrained by a retention plate/slab, which governs the correct deployment of the entire system. The potential of this new concept was recognized by SNSB/DLR/ESA who selected it for a flight experiment on its REXUS/BEXUS project.

A DREX deployment sequence
DREX deployment sequence
DREX telecommunication system
DREX in its deployed configuration

Manufacturing and flight testing of DREX

At the time of development, 3D printing was not a viable option because the team had difficulty finding a provider of materials with the required mechanical properties to withstand the stratosphere. As reported by Vittorio, they instead opted to manufacture almost every part using CNC machining and Aluminum 7075, an extremely common alloy in the aerospace sector.

Additive manufacturing had never been an option. At the time, machined aluminum was not even a strategic choice, just the natural order of things.

Vittorio Netti

A part that proved to be a particular manufacturing challenge was the actuation plate that triggered the deployment sequence, shown below. This component had to be strong enough to retain the pre-loaded springs until the antenna reached the operational altitude and had to be manufactured within strict tolerances to avoid a premature or uncoordinated deployment. At the same time, the intricacies of the geometry required advanced 5 to 7 axis CNC machining for monolithic manufacturing or would have had to be broken down into several parts and then assembled.

Actuation plate
Deployment mechanism - Plate close-up

In the end the team opted to manufacture several parts and assemble them together, so the flight-ready plate was composed of 12 individual machined pieces. The consequences of choosing to stick to traditional 7075 aluminum and CNC machining resulted in 2000 EUR of material and machining costs, as well as production delays that almost jeopardized the whole project.

As a research team with limited time and budget, the raw material and machining cost had been a major issue to deal with, especially considering the strict manufacturing requirements needed to operate a so complex mechanism.

Vittorio Netti

DREX flew on the BEXUS24 stratospheric balloon, in the framework of the REXUS/BEXUS programme. The flight took place from the ESRANGE Space Center, Sweden, on October 18th, 2017. Unfortunately, DREX suffered a not-nominal flight during its stratospheric test that caused the failure of the actuation system. After the recovery of the experiment, analysis showed that a screw had scratched the anodization treatment on the external structure, which caused a short-circuit that irreparably damaged the onboard electronics.

Space hardware design: 3D printing to design an actuation plate

3D printing would have been a much better option for manufacturing for several reasons, one of the main ones being a far superior freedom of design.

With the current knowledge of 3D printing and high-strength materials that I have today, the mechanical design of the actuator plate would have probably been very different, for several reasons, thanks to the greater design freedom afforded by this manufacturing technology.

Vittorio Netti

3D printing technology allows the production of geometries that are difficult if not impossible with traditional subtractive techniques. Five years later, the team at Roboze, together with Vittorio has reimagined one of the critical components of DREX’s innovative design, the actuator plate, trying to quantify the advantages that using 3D printing and high-strength polymers could have brought in this context.

Instead of having to manufacture 12 different parts then join them together with screws, the actuator plate could have been printed in one complete part, saving both time and money. Changes in design during the development phase would have also been easy and fast to implement in new prototypes since all that would have been needed was a new CAD file for 3D printing. Furthermore, design optimizations could have been included that reduced mass and limited mechanical complexity, providing an additional hardware safety layer that would have protected the design from unforeseen situations. On top of that, in an unforgiving field like that of space hardware, the design of the space plate would have greatly benefit from the mass reduction guaranteed by the use of polymers in place of metals.

3D printed actuation plate
Actuation plate optimized for reduced mass and greater functionality
 Aluminium 7075, CNC machiningPEKK, 3D printing
Number of parts121
Total mass133 grams60 grams
Cost2020 EUR / 2160.75 USD65 EUR/68 USD

The stratospheric properties of Roboze PEKK

High-altitude balloons need to survive in a harsh environment (high radiation, extreme temperatures, and chemical attack), therefore only the most suitable materials can be used. One such material is Poly Ether Ketone Ketone (PEKK), part of the PAEK family of high-performance thermo-polymers. This is a thermo-polymer with exceptional mechanical (tensile strength: 86 MPa, elastic modulus: 3.2 GPa), thermal (continuous service temperature: 255°C), and chemical characteristics that is perfectly able to survive the rigors of the stratosphere. Having half the density of aluminum, spacecraft parts manufactured with PEKK are much lighter than their metal counterparts, which when combined with the greater design freedom of 3D printing could reduce the mass of the parts by much more than half (while of course always keeping in mind the loads and mechanical requirements).

Advantages of Roboze Plus PRO: contact us for a free consultancy!

As is well known, the greater the complexity of a part, the longer the manufacturing time and the cost. This can create severe bottlenecks in project development, slowing the prototyping process and reducing the number of redesigns made, resulting in a sub-optimal solution. By employing an in-house Roboze Plus PRO 3D printer capable of using high-performance materials like PEKK, prototypes can be made cheaply and quickly, enhancing the design process, and leading to highly optimized parts tailored for specific applications. PEKK can also be used to manufacture flight-ready parts, meaning that the entire design and final manufacturing process can be done internally without resorting to external partners.

Roboze PRO Series is a line of professional 3D printers that can use advanced materials like PEKK. The compact design means that it can easily fit in any workshop or laboratory while still retaining the trademark Roboze features of highest accuracy and repeatability on the market.

Find out more here or contact one of our experts today for a free consultancy.

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