It is possible to design heliocentric transfers to Mars culminating in ballistic capture and, with an impulsive-thrust strategy, these have already been studied, but were found to be less fuel-efficient and longer-lasting than Hohmann transfers. The objective of the present work is to investigate the characteristics of Earth-Mars low-thrust transfers to ballistic capture.
Small spacecraft are very mass- and power-constrained, so orbit transfers are challenging for them, especially to interplanetary destinations. To try and shift this paradigm, the study was carried out assuming the spacecraft to be a 16-unit CubeSat. In addition, to improve the validity of the results, ballistic capture was designed using a model that included many perturbing forces, namely third-body perturbations, solar radiation pressure and non-spherical gravity.
Some capture orbits were selected, each with a different arrival date at Mars, and targeted from Earth, on multiple departure dates. It was found that if the spacecraft is given enough time, the low-thrust strategy requires roughly the same fuel regardless of Earth departure or Mars arrival dates. In addition, terminating a low-thrust transfer to Mars in ballistic capture does not carry additional costs, when compared to simply rendezvousing with the planet. With the assumed spacecraft and departure conditions, only around 5 kg of propellant are required to reach Mars and get ballistically captured. Nevertheless, the spacecraft needs to fly for at least 3.5 years, which can be too long for a CubeSat.