Assessing the debris risk from the avalanche of CubeSats

In the past five years, the CubeSat class of spacecraft has grown from an easily-ignored `toy' of universities to the most common type of spacecraft launched. With so many spacecraft released on-orbit in such a short time, it is natural to worry about the increased risk of collisions due to CubeSats. Fears of a CubeSat-driven “catastrophe” have surfaced in the trade publications and at symposia. But, are these concerns grounded in data? Using publicly-available orbit data, and the author's own CubeSat database, a numbers-driven examination of CubeSat debris risks will be presented. It will be shown that CubeSats comprise a very small fraction of the objects in orbits of interest. Moreover, rocket bodies and fragmentation debris comprise the dominant sources of collision risk - an assertion borne out by the evidence of collisions to date. Also, it will be shown that NASA/DoD's current policy towards CubeSats (i.e., placing them in naturally-decaying orbits, with lifetimes of less than 7 years) is quite effective in mitigating CubeSat collision risks in the short term. In fact, only a few international launches are responsible for the preponderance of long-orbit-life CubeSats. This paper will conclude with a brief review of other debris mitigation strategies and their possible consequences, based on this study of the orbit data.