The YES and YES2 Projects: Fuelling Inspiration for YPSat-1

YES: Pioneering the First Young Professionals-Led Space Mission Series

The first YES project laid the foundation for what would become a series of student led space missions then coordinated in ESA. Initiated in the 1990s, YES was a groundbreaking experiment that involved young engineers at ESTEC. The core idea was to employ long cables in space, or "space tethers," to alter a spacecraft's orbit without using propellant. This concept was revolutionary because it offered a method to maintain the orbit of space stations and satellites without the constant need for refuelling—an operation that costs hundreds of millions of dollars annually.  Moreover, the YES project already tackled the increasingly urgent issue of space debris. The idea of using tethers to systematically remove debris from space was both visionary and necessary. Traditional methods of debris removal, which involve launching rockets to capture and deorbit debris, are not only costly but also potentially exacerbate the problem by creating more debris.

“the YES projects may be the best time of my life (…) We had a lot of night work. There's one of these nights that we had to move the YES2 to the vacuum chamber. The shortest way it was to go outside and it was raining, so we just put some plastic wrap around satellite and put it on one of these trolleys. We have hundreds of memories and anecdotes” Michiel Kruijff, team lead of YES project 

YES2: Building on YES to Advance Tether Technology and Fuel-Free Space Travel

YES2, launched in September 2007, built on the foundation laid by YES. It was the second in this series of young professional-driven space missions, this time involving a more complex experiment with a smaller satellite weighing 36 kg. The mission aimed to demonstrate the tether technology's potential by deploying a 32-kilometer tether in space to return a small capsule to Earth. YES2 was not just a proof of concept but also a record-breaking mission, showcasing the possibilities of low-cost, innovative space missions driven by enthusiasm and perseverance.

The YES2 project, while a vital demonstrator, made it clear that further development was necessary to fully realize the potential of tether technology. YES2 was a first step of several to prove that tethers can convert solar power into propulsion energy, eliminating the need for traditional propellant. This ability to generate propulsion in space without relying on fuel could revolutionize space travel, particularly for missions involving the removal of space debris.

Despite the challenges, YES and YES2 broke several records and demonstrated that even with a restricted budget and hard deadlines , significant contributions to space exploration can be made. The success of YES and YES2 also had a broader impact. They inspired subsequent initiatives like the Euromoon project, led by Dutch astronaut Wubbo Ockels, and the SSETI (Student Space Exploration Technology Initiative), which eventually led to the launch of the SSETI Express satellite. These projects also influenced the formation of ESA's Education Office and the now well-established Concurrent Design Facility (CDF).

YPSat-1: Following in YES2’ Footsteps

Fifteen years later, a new group of passionate young professionals took on a challenge similar to YES and YES2: designing, building, and launching their own satellite. Like their predecessors, they created and tested their own technology. The mission of the Young Professional Satellite (YPSat-1), was to capture key moments of the Ariane 6's inaugural flight, including the fairing separation. What made this mission unique was that YPSat-1 had to wake up before the rocket—something never done before. The team developed a Wake-Up System that triggered the satellite’s onboard computer to start the mission sequence when it detected the pressure conditions typical of a launch.

"YPSat-1 has generated hundreds of anecdotes for a lot of us, I will forever remember those long nights and week-ends spent in the laboratories and clean rooms assembling and testing the YPSat-1. This project has shown that Space is very hard, but Space is also very rewarding. With our success, the whole team is very grateful having dedicated so much time and efforts during almost two years and half, but with or without success, the journey is already 1000 times worth it. Learn by doing, is really our mantra” Julien Krompholtz, Former Team lead of the YPSat-1 Project.

YPSat-2: Validating and Broadening Young Talents

Following the path opened by the YES’ and YPSat-1’ endeavours, the legacy of the Young Professional Satellite, YPSat-2, aims to demonstrate scientific experiments in space conditions. Composed of one team working on two payloads, the mission will enhance the understanding of life's origin (LEOrigin) and the effects of the space environment on the human cardiovascular system (AIM). Currently at the end of the Preliminary Design Review, YPSat-2 is planned to be deployed from the maiden flight of ESA’s reusable spacecraft, Space Rider (scheduled to launch in mid-2026). 

Closing remarks to close the (first) loop

Both projects share the goal of giving young professionals hands-on experience in a supportive space community. Their legacy goes beyond technological achievements—it’s about inspiring future generations of space engineers. As YPSat-1 evolves with YPSat-2, it takes on the spirit of innovation and exploration that YES and YES2 embodied.

"Looking back on the YES initiatives, it is remarkable to see the many similarities between the YES and YPSat projects. The night work, weekends in the lab, pragmatic solutions, but most of all, the learning whilst having fun with our peers! Even 30 years apart, Young Professionals in ESA are demonstrating the same passion and ambition, willing to go the extra mile to achieve something extraordinary." Tuur Strobbe, Team lead of the YPSat-1 Project.