Hi, for the moment there is no ongoing project for ADR (Active Debris Removal). Serval techniques are currently under investigation: electromagetic methods, capture with net-like systems, momentum exchange methods (for example augmentation of drag of the debris to increase the entry velocity), ground based methods, modification of material properties or change of material state. You can easily find references on these techniques in many papers.

Hi,

ESA's e.Deorbit project invested in developing ADR technologies.

For starting references:

During the Clean Space industry days, this technologies were discussed. See the 2016 presentations (https://indico.esa.int/indico/event/128/) and also the active debris removal session during the Space debris conference in 2017 (proceedings are https://conference.sdo.esoc.esa.int/proceedings/list)

Hi,

as already mentioned above, there are several techniques that have been considered and investigated for ADR. I can give you a quick overview of some existing contactless ADR techniques.

The first one is the ion beam shepherd (also proposed for asteroid deflection), a concept which has been studied during the European Commision project LEOSWEEP (2013-2016). This consists in gently repositioning a space debris object to a different orbit through the ion push of a plasma plume directed towards the debris by a shepherd spacecraft (which must rendezvous with the debris first). The main advantages of this technique are its contactless type and its high propellant efficiency (electric thrusters are considered for both the impulse transfer thruster and the impulse compensation thruster, which maintains formation flight).

The second technique, probably more indicated for space debris in GEO orbit, is the space pusher/tug by Coulomb forces, which consists in charging electrically both the space pusher/tug and the space debris (with the same sign in the pusher configuration, or with opposite sign in the tug configuration) so that a Coulomb force (attractive or repulsive) acts between the two bodies.

Finally, another technique is the use of an electro-dynamic tether, in which an electric current flows through a conductive wire attached to the space debris, and produces an accelerating or decelerating Lorentz force (due to the interaction of the wire current with the Earth's magnetic field). Such a tether could be installed on new satellites and used after their end-of-life.

Best regards

Hi, One the methods which also has been studied as a possible solution for both ADR and End-of-Life disposal scenarios, is drag augmentation method, as Richard mentioned. This concept has the advantage of no need for thrust generating sub-system during de-orbiting phase, basically it adds a cross sectional surface to the rotating object and generates extra drag force vector (opposite to the direction of the debris velocity vector) in LEO to decrease orbital velocity. This method is not effective itself in high LEO orbits, but in general LEO debris problem, it can guarantee to satisfy mitigation guidelines from IADC and NASA which the satellites needed to be removed from space maximum 25 years after their mission operation end time. Currently, Some research institute in different countries are already working to design their own drag sail system to be tested in space including some in space tests from NASA and JAXA with similar deployable mechanism.

Hi, one practical approach is that using the space robotic arm to grasp the space debris and tow it into atmoshpere; Another practical approach is that using deployable or inflatable equipments to increase cross-sectional area and aerodynamic drag, and then reduce the orbital life.

In addition to the options that Shuang Li wrote I remember that someone also proposed to use "space nets" to capture the passive object, but I'm not sure how that concept has evolved so far. Interesting though.

Hi, one promising solution is to use tethered space robots(TSRs). A TSR typically consists of a gripper and a maneuverable platform which are connected by a flexible tether. Thanks to the tether connection, TSR can deploy the tethered gripper to capture the debris in the long distance and then tow it to the disposal orbit, forming what we call 'towing removal'. This Active Debris Removal technology is well being developed at Northwestern Polytechnical University, Xi'an, China. You are very welcome to refer to our papers.