Research pick: Planning a journey around your asteroid - "Optimal trajectory design for global exploration of an asteroid via bi-impulsive transfers"

Once you have your craft in space, what’s the best way to explore an asteroid? Research published in the International Journal of Space Science and Engineering sets out to answer that question. There have already been several successful missions to examine asteroids, the irregular and fast-moving chunks of rock that orbit our Sun that we consider too small to be called planets. Among them NASA’s NEAR, JAXA’s Hayabusa, and ESAs Rosetta. JAXA’s Hayabusa 2 and NASA’s OSIRIS-REx are currently exploring the asteroids 162173 Ryugu and 101955 Bennu, respectively.

The irregular shapes and mass distribution of an asteroid make their gravity fields remarkably complicated in terms of locating a spacecraft to close proximity with the object and navigating a global route around it with focus on particular points of interest. Now, Yu Shi, Yue Wang, and Shijie Xu of the School of Astronautics at Beihang University in Beijing, China, and Hao Peng of the Department of Mechanical and Aerospace Engineering, at Rutgers, The State University of New Jersey, USA, point out that the trajectory must be optimised for scientific relevance as well as fuel efficiency.

They have found a way to optimise the trajectory for a future spacecraft based on an initial estimate of movements required based on assuming the asteroid is a simple point mass with a uniform gravitational field. They then expand on this using the well-known travelling salesman problem of planning a route that minimises distance covered but allowing the salesman, the spacecraft, to visit each place of interest in its journey around the asteroid. As proof of principle, they have designed an exploratory trajectory around asteroid 433 Eros. Of course, of major importance is that the trajectory avoids any collision between spacecraft and asteroid which would lead to summary termination of the mission.

Shi, Y., Peng, H., Wang, Y. and Xu, S. (2019) ‘Optimal trajectory design for global exploration of an asteroid via bi-impulsive transfers‘, Int. J. Space Science and Engineering, Vol. 5, No. 3, pp.205-222.