  Orbital debris remains as an obstacle to further space development. While
efforts are ongoing to avoid newly launched objects becoming debris, the number
of debris would still continue to grow because of collisions. ADR (Active
Debris Removal) is an effective measure, but building a sustainable economic
model for ADR remains as a difficult problem. We propose that the cost of
removal can be paid by circulating digital currency tokens on a blockchain
platform whose values may decrease and/or increase over time, issued by global
cooperation (a consortium) of parties interested in space development, in
exchange with proofs of ADR. The tokens pay their cost by themselves through
contributions by the token holders, who are likely to be benefited by removal
of debris. This scheme imposes virtually no cost to the consortium. We have
generalized this concept as POD (Proof of Disposal), which, we believe,
provides a more accountable foundation for solving social problems with digital
currency than many ICO (Initial Coin or Cryptoasset Offering) in practice
today. We evaluated the feasibility of our proposal through a simulation. We
conclude that dynamic estimation of the economic values of each ADR and
automated pricing of tokens that represent the orbital debris being removed are
indeed possible. Actual prototyping of the proposed digital currency system is
ongoing.
