How does water spray behave in Low Earth Orbit (LEO), from the side exposed to the Sun to the side in Earth's shadow? Could it be used as means of augmenting atmospheric drag and deorbiting defunct spacecraft and debris from LEO faster than their orbits would naturally decay?
The only mention of drag augmentation as means of active debris removal that seem to be under consideration for the moment are the use of gossamer drag augmentation structures and deployable sails, or expanding foams, e.g. as mentioned in ESA's Active Removal of Space Debris: Expanding foam application for active debris removal (PDF):
The core idea of this method is to increase the area-to-mass ratio of these objects such that the atmospheric drag can cause their natural re-entry, thus “cleaning up” different regions in the near-Earth space. The drag augmentation system proposed does not require any docking system and just an uncontrolled re-entry can follow, thus it seems a short-term application free from the usual technological issues of these debris removal systems.
Venerable idea, but what about the other way around? Instead of increasing the area-to-mass ratio of space junk, would it be feasible to increase local atmospheric density by means of spraying water ahead of their orbits, while perhaps at the same time using such spraying as means of maintaining orbit (propulsion for orbital reboost) of the "drag augmentation device"?