Actual instruments on satellites are very sensitive to contamination. This activity aims to develop a molecular absorption coating that can be applied close to senstive surfaces – e.g. optical instruments – to keep contamination at low level.

Following the development during SLPMC2, this project “A3Lub2” AAC performed successfully the validation of the new material TS8591 by ENSINGER Sintimid (AT). Following that, all critical bearings necessary for a Large Deployable Reflector (LDR) were manufactured. AAC ran extensive testing it ins new “DYNAX” setup which enables at combination of axial and radial pre-loads. as well as changing them in-situ. They could concluded with the success of being selected for the LDR of the earth observation mission “CIMR”.

The primary, major goal of this project was the development of a drive unit for the space sector, which can be used for many applications based on its universal approach. A 66% cost reduction in space drives and a reduction in delivery times from the current typical 10 months to less than 3 months are targeted. AAC’s part was the selection of the tribological components and testing of the drive unit.

The term “Compliant mechanisms” refers to bulk components that can replace tribological components like bearings or gears: in contrast to a bearing or a gear, they do not need lubrication. Using Shape Memory Alloys (SMA) motion can be generated without use of a classical motor. With in the ESA project 4Dprint, RHP (AT) manufactured a compliant mechanism (rotary actuator) by 3D-printing. The performance was tested under TVAC at AAC. Therefore, the gear test rig HADES was adapted to measure stiffness, output torque and output angle in TVAC.

Within the last years, AAC developed a novel hybrid multifunctional piezo / temperature sensor and monitoring concept for flow front, cure and structural health monitoring of composite parts manufactured by resin infusion, mainly for aeronautic applications.
The main objective of “LiMoCoSS” is to use the idea of the above-mentioned concept and to develop a sensor and monitoring technology for space relevant composite structures and manufacturing techniques such as wet winding for through live monitoring of composite structures during manufacturing, storage, transportation and usage.

This activity aims to develop an evaporation model for long life mechanisms including all most important mission factors influencing the total mass loss of lubricants. A web-based tool for calculating the outgassing behavior is created to give space engineers the opportunity to build their mechanisms even more precisely.

ESA has funded a €1 million project led by HPS, AAC, and DLR to develop next-generation multifunctional films for space applications. Aimed at improving satellite protection and performance, the project focuses on creating advanced materials with features like ATOX resistance, non-reflectiveness, and adaptability for use in thermal insulation, deorbiting systems, and stealth technologies.

The usage of linear piezo motors offers attractive advantages (such as outstanding torque vs mass ratio, irreversibility and stable positioning when unpowered). Friction based actuators would not need any energy during holding times. However, the main disadvantage of this necessity of stable friction and low wear.Within an ESA-Project AAC was responsible to validate friction coefficient in a representative way for the stick-slip-motion of such piezo motors. Following the non-promising results, AAC could within an FFG-project “Friction-to-Move” develop a new coating that offers medium and stable friction in ambient air and high vacuum. 

This project aims to develop an improved, simplified methodology for predicting lubricant evaporation through labyrinth seals which can be used by space mechanism designers. This prediction is critical to check if a sufficient amount of lubricant is in the bearings at the end of life and, secondly, to estimate potential risks of molecular contamination of nearby sensitive surfaces.

For ball bearings, steels were developed with a high hardness to obtain good wear resistance and to survive high contact stresses, but not being resistant against stress corrosion cracking (SCC). However, the trend to higher efficiency and mass reduction leads to “integrated solutions”, like combining bearing with housing for which tensile stresses appear in the rings and the problem with SCC compatibility arises.  The project validated a heat treatment enabling Cronidur steel to withstand SCC test at a stress level of 50% of Rp02 without any signs of corrosion and stress-corrosion cracking phenomena. As Harmonic Drive ® Gear was using a Wave Generator Bearing machined from Cronidur and thermally treated via AAC. A life test in thermal vacuum was run for almost 6 months (from +90°C to -40°C) showing the bearing rings to be in good conditions.

Sliprings are a common building block of satellites and are used to transfer electrical signals and electric power onto a rotating axis. A lot of R&D in this field was ongoing in the last years and it was found, that actual tribometers are reaching their limits when it comes to testing of sliprings. Target of the project “LuST” is to extend the existing test method to low temperature to verify, if lubricated sliprings are feasible not only for room- and high tempertures but also in low temperature conditions as well.

In 2019 an ASAP-project under bi-lateral funding of Austria (FFG) and Germany (DLR) could successfully be finalised. It aimed at enhancement of torque and lifetime for solid lubricated Harmonic Drive ® gears (HDs). Together with the manufacturer Harmonic Drive SE (DE) and an Austrian supplier for heat treatments (HMW), reasonable effort was put in the optimisation of nitriding process towards PH-steels used for gears in space. The main problem was that standard nitriding processes cause formation of so called “white etching layers”, which are on PH-steels very brittle. The new process aims at avoiding that layer and just improving the subsurface hardness to provide a better mechanical support of the tribologically stressed surface. Final life tests were done on newly nitrided Harmonic Drive ® gears, having been fully solid lubricated by use of tin coatings in the toothing. They life could be increased from less than 4000 revs to almost 15.000 revs.

An ASAP-project under bi-lateral funding of Austria (FFG) and Germany (DLR) aimed at enhancement of torque and lifetime for solid lubricated Harmonic Drive ® gears (HDs). Together with the manufacturer Harmonic Drive SE (DE) and an Austrian supplier for heat treatments a new nitriding process was developed for PH-steels used for gears in space. The new process aims at avoiding brittle WE-layer and just improving the subsurface hardness. In 2021 the ESA-MREP project “Mechanisms working at low temperatures” a Harmonic Drive ® gear was equipped with newly nitrided parts. Life tests over 63.000 output revolutions under permanent thermal cycling between -80°C and -5°C were successful at high efficiency.

Bulk metallic glasses (BMG) are still an exotic kind of material. In fact, they are rapidly cooled metallic alloys. The rapid cooling “freezes” the amorphous state of the liquid and hinders crystallisation. AAC acting as subcontract to RHP assisted in material characterisation and application tests on springs and hold-down and release mechanisms (HDRM). BMG in contact to itself showed surprisingly low adhesion in fretting tests done in launch conditions. Hence, bulk metallic glasses may become an interesting new option for HDRMs.

To get non-dependent from non-EU-suppliers, a new material based on PTFE was developed by ENSINGER SINTIMID (AT) under assistance of AAC. It’s targeted use as cages in ball bearings offers the lubricant to be transferred by the balls from the cage onto the races. Bearings can be equipped only with a cage made of the new PTFE-based material, showed in long term ball bearing tests low torque.

Within the ESA-project “Magnetic Brake” an Austrian consortium designed, built and tested a braking system which can be attached to a motor and increase it’s holding torque. This device – the magnetic brake – is contactless, wear-free and helps to reduce the power consumption on satellites. AAC’s part was to test the magnetic brake under space conditions (high vacuum hot and cold) and verify it’s predicted performance. The test campaign was finished successful in 2023 and the device outperformed ESA’s specifications.

35 Years anniversary of the “Materials testhouse” @ AAC 

AAC is proud to announce, that its frame contract to ESTEC on Metallic Material Characterisation (“ESA testhouse”) has achieved in 2024 an anniversary of 35 years. The first contract of our space group to ESA/ESTEC could be established in 1989. Since then, AAC was 4 times successful to er-establish this contract in open competition. The aim is to validate new materials and processes for use in space. The contract shall provide data necessary for space engineers to apply new materials or processes in their missions. As qualification for space is cost and time consuming, this is usually not possible within mission. 

Recent studies continued validating the SCC-resistance of new materials made by AM (Additive Manufacturing, 3D-Printing). One of the key competences within this contract is “Cold Welding” having be initiated by ESA in 1990ies. Finally ESA agreed with AAC on a test method to benchmark contact pairs for their risk to cold welding and published it as “STM-279”. Meanwhile, several pairs were screened and the data generated is available via an online data base. Due to upcoming new needs, the standard was recently updated by AAC and is in review at ESA.