The European Space Agency (ESA) has addressed the need for cleaning up space for a long time now, but since formation of ESA’s Clean Space initiative in 2012, things suddenly got more serious. Having been part of this movement myself, I’d love to tell more about this. Let’s start with the situation right now: at Space19+, ESA’s Ministerial Council, which took place in Seville, Spain, at the end of November last year, ministers agreed to place a service contract with a commercial provider for the safe removal of an inactive ESA-owned object from low-Earth orbit.
How easy is it to remove a debris in space? According to science fiction like Star Wars it is quite easy: all it takes is a magnetic beam, some tentacles, and a much larger spacecraft than the debris itself.
Back on ‘Earth fiction’, James Bond movies such as You Only Live Twice showed an interesting approach too: have the fairing of a rocket open, and almost eat the other spacecraft (in reality though, the rocket’s fairing is jettisoned a few minutes after launch).
Now let’s take a look at reality. This is NASA’s Space Shuttle flight STS-49 where astronauts tried to capture the Intelsat astronaut. First an astronaut standing on top of a platform connected to the Shuttle’s robotic arm was trying to capture Intelsat using a clamping mechanism, but failed. A comparison was made to the underwater testing during training for the flight, and in space anything you touch will simply drift away; even such a heavy satellite such as Intelsat. After several attempts, NASA decided to deploy three astronauts and capture the satellite with their hands.
Bottom line? Capturing a piece of trash in space is nothing like picking up a trash container (standing still nicely in the street due to gravity) by a garbage truck. Our ‘space garbage truck’ will need to find a way to not only capture it, but also ensure that the slightest touch won’t make the debris move away from it. A methodology enforcing ‘capture before touch’ is required. One solution is to embrace the debris, with whatever capture device, before we actually touch or grab it.
Then there is the close approach. There is no Space Shuttle anymore where pilots put the Shuttle as closely as possible to Intelsat. Autonomous spacecraft without a crew will have to do the job. We can always ‘steer’ a spacecraft from ground by sending commands, but space debris is likely to rotate / tumble, and moving for example a robot hand to capture the debris at a specific point in a tumbling situation with varying light conditions (in space shadows are typically black, not grey-scale), as well as estimating a possible need for abort at every seconds, will be out of reach for controllers on Earth. For those final steps, the spacecraft will need to move and make decisions autonomously. To aid in this, many sensors such as cameras will be needed to navigate the spacecraft close to the debris (this is called visual navigation) and capture it.
ESA has studied this for years with large European spacecraft integrators such as Airbus, during a mission design called ‘e.Deorbit’: a mission to capture the tumbling ENVISAT satellite using a robotic arm. Much was learned during this design phase and the complexity of the mission became apparent: to this day no one has ever captured a dead satellite (tumbling), held it tightly using a firm grip, and remove it from space.
The video above also shows what ‘removing’ means: to lower the debris such that it enters into the atmosphere and burns up. For ESA’s first test mission, the removal of one debris is sufficient to test and demonstrate the removal of space debris (and at the end of the mission’s lifetime, the ‘space garbage truck’ shall also remove itself from space!) however in the future several removals need to be made per remover spacecraft in order to lower the cost-per-removal.
So where are we today again? Following the decision of Space19+, the e.Deorbit mission has been replaced by the ClearSpace-1 mission: a mission that aims to remove a 100 kg upper part of an upper-stage from the VEGA launcher that is stranded in a 800 km high orbit. Supported within ESA’s new Space Safety programme, the aim is to contribute actively to cleaning up space, while also demonstrating the technologies needed for debris removal. Led by a Swiss start-up called ClearSpace Today, the design is about to start.
The capture device? A set of four tentacles that clamp around the debris, ensuring capture before touch (that Star Wars concept wasn’t so bad after all!). The mission shall be launched by 2025. Supporting this mission will be my main activity at work for the next five years, and I’m very excited to work for such a special mission!
Would you like to read more about space debris? Here is a free e-book from 2015 about everything you need to know about space debris! Download here (pdf).
Ciao!
Robin
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