October 8, 2020

SpaceBlower: a rocket to combat space debris

SpaceBlower is a light suborbital rocket designed to eject a cloud of particles into the path of large non-manoeuvrable space debris. Its goal is to avoid collisions likely to generate thousands more debris fragments and thus to keep satellites and their orbits safe. Space Blower is a preliminary project initiated and funded by CNES and its partner Bertin Technologies (now CT France). Christophe Bonnal, senior expert at CNES’s Launch Vehicles Directorate, outlines what this project is aiming to accomplish.

A spent satellite and a launch vehicle upper stage are on collision course: this kind of scenario could become increasingly likely in ten years from now. Neither is manoeuvrable, so action is required to avoid serious consequences. Within hours, SpaceBlower is air-launched to an altitude of 1,000 kilometres and its third stage steered to intercept the debris and eject a cloud of particles into its path. Just slowing the debris by no more than 10 centimetres per second with the artificial atmosphere thus created will be enough: if launched 12 hours ahead, SpaceBlower could ensure the two objects miss each other by 13 kilometres and avoid a collision.

SpaceBlower’s third stage ejects its plume of particles into the path of a non-manoeuvrable debris object. Credits: CT France

CNES’s space debris expert Christophe Bonnal is the initiator behind this project.

“We’ve done a lot of work with CT France on shaping the particle plume,” explains Bonnal. "It needs to be wide but not dense, using gases or particles. Ideally, small particles just 5 microns across, made of copper, for example. SpaceBlower would fly a bell-shaped suborbital trajectory, so all the particles would fall back into the atmosphere without generating any new debris, which is obviously important.”

As well as being air-launched to impart initial velocity and make operating the system a lot less dependent on weather conditions, SpaceBlower could even leverage current efforts to develop reusable launchers to reduce costs.

“We’d like the first two stages to be reusable. The third stage can also be reused with the addition of a parachute and buoy, but that means more weight and carries a significant performance penalty. So the first missions would be expendable to see whether we have the right amount of copper to do the job. And after four, five or six launches, we could scale back the payload and make the system fully reusable. The cost would be around 2 to 3 million euros, about 10 times cheaper than other active debris removal solutions."

Christophe Bonnal, senior expert at CNES’s Launch Vehicles Directorate.

INTERNATIONAL COOPERATION FOR INTERNATIONAL SPACE

SpaceBlower, air-launched from six partner airports around the globe. Credits: CT France

SpaceBlower would be air-launched from six partner airports that would all have to be located near the equator to optimize the intercept trajectory. The airport for each launch would be chosen according to the conjunction geometry, and the lighter of the two debris objects would be targeted.

“The idea is for SpaceBlower to be a global solution,” says Christophe Bonnal. “That would require an aircraft at each airport and two or three available rockets. We could thus avoid major collisions that occur every five years or so. And there would have to be total transparency to avoid its use as an anti-satellite weapon.”

The French Space Operations Act (FSOA) initiated by CNES governs and limits production of space debris since 2010. Prevention remains the best solution to avoid debris breaking up into thousands of fragments.

“All the debris out there for decades before the space operations act still pose a problem. They hit other debris objects and, worse still, active satellites 10 times a year. This exponential growth in the debris population is the result of the Kessler syndrome as illustrated in the movie Gravity. There are two ways to stop that happening: mitigation, by limiting the lifetime of new debris to less than 25 years, or remediation through active debris removal or a system like SpaceBlower to avert collisions.”

LAST-MINUTE INTERVENTION IN SPACE

An identified collision risk between two large catalogued but non-manoeuvrable debris objects. Credits: CT France.

SpaceBlower is one of three avenues being explored by Christophe Bonnal and CT France to avert debris collisions at the last minute, based on the principle of just-in-time collision avoidance or JCA.

“We’re working from the principle that only a small impulse is needed to get debris on a collision course to miss each other by several kilometres. Three or four techniques have been studied, like attaching small cubesats to debris objects to make them manoeuvrable. Even from the ground, a laser could be fired to vaporize the debris surface. With impulses of just 10 picoseconds, the outgassing would still create enough thrust to cause the debris’ course to deviate.”

This same laser vaporization technique is the already used to analyse rocks on Mars by the ChemCam instrument on the Curiosity rover and soon SuperCam on the Perseverance rover scheduled to arrive in February 2021.

Further reading