Assessing collision algorithms for the NewSpace era

Abstract

The ‘NewSpace’ era of the last two decades has seen increasing disruption and innovation in the space industry driven by a growing commercial element. A new investigation of spacecraft launched between 1980 and 2017 identified an increase in the number of spacecraft being deployed into similar target orbits. This has resulted in a shift from a more random spatial distribution of objects to a situation with greater spatial structure. With collisions expected to be an increasing and leading source of space debris it is important that we understand the performance of collision models and their sensitivity to the changing environment. We believe that current collision algorithms have the potential to introduce errors in the estimation of collision probabilities when modelling NewSpace scenarios. Two probabilistic algorithms, the Cube approach (Liou et al., 2003) and the Orbit Trace method (based on Öpik, 1951) were investigated for a range of scenarios.
An implementation of the Cube algorithm was verified using the original Jovian moons case and highlighted issues relating to convergence of the average collision probability for a pair of objects and to the relationship between the collision probability and the size of the cube used. Further tests compared the collision probabilities generated by the Satellite Orbital Conjunction Reports Assessing Threatening Encounters in Space (SOCRATES) against those calculated using each of the Cube and Orbit Trace algorithms in conjunction with the SGP4 propagator. Simulations of specific sub-sets of the tracked populations for well-defined time periods showed substantial discrepancies between the different collision methods.
The results suggest some inaccuracies in the currently used collision methods, introducing additional uncertainty to the rate of population growth in simulations of the evolution of the debris environment. Further work is ongoing to investigate the relationship between this variance and spacecraft altitude to ascertain whether current models are accurately representing where fragmentations might occur.

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Identifiers

ORCID for Samuel, Douglas Diserens: orcid.org/0000-0001-5521-2041

ORCID for Hugh Lewis: orcid.org/0000-0002-3946-8757

ORCID for Joerg Fliege: orcid.org/0000-0002-4459-5419

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