May 2019

n MOTORS SUPPLEMENT Steppers help to sense Martian quakes L ast month, Nasa researchers reported that their InSight Mars lander craft, which touched down on the red planet last November after a seven- month journey from Earth, appeared to have detected the first“Marsquakes”. The lander’s sensitive instruments detected a slight trembling that was not due to Martian winds or to movements of the lander’s robotic arm. This could be the first seismic activity ever detected on Mars. The ultraprecise seismometer on board the InSight is capable of capturing sub- nanometre level ground movements as a result of quakes, meteorite impacts, dust storms or landslides, or even the tiny tidal deformation of Mars induced by its moon, Phobos. The SEIS (Seismic Experiment for Interior Structure) seismometer incorporates three extremely sensitive pendulums to detect the tiniest movements of the Martian surface. The displacement of the moving parts of the pendulums is measured electronically. To fine-tune the pendulums for Martian gravity, mission engineers designed a motor- driven equilibrating system. In addition, each pendulum is fitted with a special thermal compensation mechanism to guard against Mars’rapid and wide temperature variations. Phytron, a German company which specialises in designing and building motors, drives and motion systems for the extreme environments, supplied three 19mm- diameter stepper motors for the SEIS instrument. The motors are coupled to in- house designed planetary gears with 48:1 reduction ratios. Phytron has already supplied more than 250 motors for space applications and many more for other demanding tasks. The company started to develop the stepper motors and gears for the Mars mission in 2013, under a contract from the Max Plank Institute for Solar System Research. With several European and American partners collaborating on the SEIS project, the motor systems had to be delivered well before InSight’s launch in May 2018. The three gear-motors form part of a triangular levelling system that aligns the instrument precisely via precision spur gears driving separate threaded spindles. The motors, with nominal currents of 0.3A and a full-step resolution of 200 steps/rev, and the integrated gears, use relatively simple and traditional designs. However, the attention to detail in the development and manufacturing process included separate engineering and qualification models, each of which underwent intensive performance testing for electrical, dynamic, mechanical, and thermal specifications before final flight models were supplied for the mission. The radiation-resistant motion components are designed for use in ultra-high vacuums and for operation in temperatures from 573K (300⁰C) in the motor windings, down to ambient levels of 4K (–270⁰C). The gears incorporate special lubrication and are built using materials such as high-quality stainless- steel and titanium. n Phytron is represented in the UK by Mclennan. Nasa’s InSight spacecraft, which landed on Mars last November, includes a sensitive instrument designed to detect any Martian “quakes”. Key to the instrument are three custom stepper gear-motors. A cut-away view of the SEIS seismometer (image: Nasa/JPL- Caltech/CNES/IPGP) Secure remote access made easy www.appliedautomation/x-stk 02920 494551 / sales@x-stk.com new Sitemanager 35xx from � Connect multiple devices simultaneously � Intelligent cloud data collection module � Easy and ¿rewall friendly internet access � Persistent store-and-forward database � Drag and drop SCADA tunnelling setup � 3 port integrated managed switch

RkJQdWJsaXNoZXIy MjQ0NzM=