Can you do it in less than 12 parsecs?
It is the year 2060 and the commercial exploitation of Low Earth Orbits (LEOs) went well beyond the trillion of Euros market size. Following the unprecedented explosion of a Sun-synchronous satellite, the Kessler effect triggered further impacts and the Sun-synchronous LEO environment was severely compromised. Scientists from all main space agencies and private space companies isolated a set of 123 orbiting debris pieces that, if removed, would restore the possibility to operate in that precious orbital environment and prevent the Kessler effect to permanently compromise it. You are thus called to design a series of missions able to remove all critical debris pieces while minimizing the overall cumulative cost of such an endeavour. Each single mission cost (in EUR) will depend on how early the mission is submitted via this web-site (regardless of their actual launch epoch) and on the spacecraft initial mass.
Submissions can be undone, so as soon as you have a mission that has chances to end up used, you may want to submit it to freeze its cost!