MSA Member Reports on ESA’s Young Engineers’ Satellite
Last week saw the launch of ESA’s Young Engineers’ Satellite (YES) 2 - a tethered re-entry mission that seeks to bring a 5kg payload back to Earth using a 30km piece of string! For the past five years, over 300 students and young graduates from around the world, including several RMIT affiliates, have worked on this project, sponsored primarily by the European Space Agency and managed by Delta-Utec SRC in the Netherlands. In addition to providing a rich educational experience, the mission will demonstrate “spacemail” - the ability to send an object, such as an experiment from the ISS, back to Earth without the need for expensive rockets or Space Shuttles.
On Sept. 14th YES 2 was launched into LEO as a piggyback on Foton-M3 (a module on a Russian Soyuz rocket). After the other experiments on Foton have completed their 2-week mission, YES2 will spring-eject a spherical re-entry capsule, which is connected to the main satellite by a 0.5mm-thick tether. As the capsule, Fotino, gets further away from the satellite, the tether continues to deploy from a spool much like unwinding a reel of cotton off one end. As the distance between the two end bodies becomes great, the difference between the gravity forces becomes significant enough to accelerate the deployment. The changing length of the tether causes it to swing away from the vertical, until it reaches its full length (30km). At this point the deployment is halted by a braking device and gravity swings the tether back like a pendulum. The swing motion gives the capsule enough relative speed (opposite to its orbital motion) that by cutting the tether as it passes through the vertical, it is sent on a trajectory back toward Earth. Also assisting in the re-entry is the fact that the tether holds the two masses at unnatural orbital speeds, and when the tether is cut the lower mass is already slow enough to re-enter the atmosphere. Activating a parachute after re-entry, Fotino will hopefully land in Russia with its contents intact.
My personal story with YES2 began in 2004. After graduation from RMIT, I embarked upon a desperate search to find a job in the space industry, spending night after night emailing resumes off to companies in the US and chasing up all the great contacts I had made through Mars Society, Space Futures, and NSSA, to see if I could get a foot in anywhere. Even James Waldie, an MSA member who had worked at NASA on spacesuits, was warning me of the immense difficulties for Australians nabbing a job in the green-card-mandatory field of US Space Engineering. Ready to follow the advice of Daniel Faber, a UNSW grad working in Canada on microsats, my plan was to take a trip around the world to meet contacts and attend a few quasi job interviews. Finally, I got lucky. An email came back from a contractor firm in The Netherlands, who after having read my thesis on space tethers, invited me to come do an internship. With some much welcome funding for my trip from Engineers Australia, I set off to Delta-Utec in Leiden to begin work.
Immediately I was sent to Krefeld, Germany, where the YES2 deployment test rig was being constructed. This beast was a host of reels, pulleys, sensors and computers meant to pull the tether out of the canister in a real-time simulation of the space environment. To achieve the right final tether length, swing velocity and timing, the deployment must follow a carefully designed profile. It was my job to validate the feedback control hardware and software with this closed-loop simulator. But as anyone knows, string likes to get tangled, and I definitely spent two cumulative weeks of my life untangling the tether when the rig would run amuck, in an effort to save the expensive Dyneema from which it was made.
I was immersed in the YES2 project for two years, in a variety of roles, including parachute deployment testing, tether winding machine design, and I even got to lead a parabolic flight test campaign on the Euro Zero-G vomit comet. Other fun contracts that filled in my time were a combined ion engine & electrodynamic tether propulsion system for ESA, and a swinging-tether launch assist stage for the French Space Agency. It was a great environment there amongst interns from all around Europe, and the lunch conversations varied from Spanish students complaining about the Dutch weather to the Greek students arguing that Alexander the Great was truly Greek and not Macedonian.
My advice for anyone wanting to do jump into the Space field would be look for educational outreach projects of NASA and ESA and find ways to get on board. I am now getting a PhD from University of Maryland – where I get to pretend to be an astronaut in their neutral buoyancy tank. When I watch YES2 launch this Friday from the ESTEC operations center, I am certain that a countdown from 10 to 0 will have never before held so much excitement, tension and pride.
For more information check out www.esa.int/yes2 (for an animation of the mission) and www.yes2.info