Our closest neighboring star system, Alpha Centauri, is located at “mere” 275,000 astronomical units (au) from Earth. Because of its “close proximity” to Earth, Alpha Centauri is often considered as the prime target for a future interstellar exploration mission [1]. It holds significant scientific importance for better understanding our sun, and stars in general, and for advancing our knowledge on the formation and evolution of the solar system [2]. Moreover, by visiting Alpha Centauri, Earth-like exoplanets may be discovered (in addition to the discovery of Proxima Centauri b in 2016 [3]). Voyager 1, our fastest and farthest spacecraft, 146 au from the sun at the time of writing, would take approximately 75,000 years to reach Alpha Centauri. Photon-sail propulsion could substantially reduce this travel time [4] even though it exclusively makes use of the radiation pressure from a star to drive the spacecraft forward [5]. This novel propulsion technology has made significant technological progress in recent years through JAXA’s IKAROS mission, NASA’s NanoSail-D2 mission, and the LightSail-1 and LightSail-2 missions by the Planetary Society. Continued technological advancement will be achieved through other proposed and scheduled missions such as NASA’s NEA Scout mission [6]. Proposals for using photon sails to reach targets far beyond our solar system are not new (see, e.g., Refs. [4,7]), and initiatives with clear goals of reaching Alpha Centauri within a generation are underway, e.g., the Breakthrough Starshot project.§ However, little is known about the dynamics of the photon sail once it arrives in the other star system, especially in a multistar system like Alpha Centauri. To date, the only works investigating these dynamics include Refs. [8,9]. Both articles focused on the dynamics in the binary-star system composed of the stars Alpha Centauri A and B, and investigated the possibility of decelerating the spacecraft after arrival, assuming a graphene-based sail covered with a highly reflective coating. The MIRA Collaboration focused on the computation of artificial equilibria (AE) in the same binary-star system, but for a photon-balloon spacecraft, before investigating capture and transfer trajectories for a photon-sail propelled spacecraft in the elliptical restricted three-body problem (ER3BP) [2,10].@en

A laser-enhanced solar sail is a solar sail that is not solely propelled by solar radiation but additionally by a laser beam that illuminates the sail. This way, the propulsive acceleration of the sail results from the combined action of the solar and the laser radiation pressure. The potential source of the laser beam is a laser satellite that coverts solar or nuclear power into laser power. Such a laser satellite (or many of them) may orbit anywhere in the Solar System and its optimal orbit (or their orbits) for a given mission is still subject to future optimization. This contribution provides the model for an ideal laser-enhanced solar sail and investigates how a laser can enhance its thrusting capability. The term “ideal” means that the solar sail is assumed to be flat and perfectly reflecting and that the laser beam has constant areal power density over the whole sail area. Since a laser beam has a limited divergence, it can provide radiation pressure also at large solar distances and increase the propulsive force into the desired direction. This way, significant reductions in the flight time may be achieved for a variety of missions. This contribution also provides the analysis of some exemplary laser-enhanced solar sailing mission scenarios and presents optimized trajectories without laying too much emphasis on details of the design and operations of the laser source(s).

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A laser-enhanced solar sail is a solar sail that is not solely propelled by solar radiation but additionally by a laser beam that illuminates the sail. This way, the propulsive acceleration of the sail results from the combined action of the solar and the laser radiation pressure onto the sail. The potential source of the laser beam is a laser satellite that coverts solar power (in the inner solar system) or nuclear power (in the outer solar system) into laser power. Such a laser satellite (or many of them) can orbit anywhere in the solar system and its optimal orbit (or their optimal orbits) for a given mission is a subject for future research. This contribution provides the model for an ideal laser-enhanced solar sail and investigates how a laser can enhance the thrusting capability of such a sail. The term ”ideal” means that the solar sail is assumed to be perfectly reflecting and that the laser beam is assumed to have a constant areal power density over the whole sail area. Since a laser beam has a limited divergence, it can provide radiation pressure at much larger solar distances and increase the radiation pressure force into the desired direction. Therefore, laser-enhanced solar sails may make missions feasible, that would otherwise have prohibitively long flight times, e.g. rendezvous missions in the outer solar system. This contribution will also analyze exemplary mission scenarios and present optimial trajectories without laying too much emphasis on the design and operations of the laser satellites. If the mission studies conclude that laser-enhanced solar sails would have advantages with respect to ”traditional” solar sails, a detailed study of the laser satellites and the whole system architecture would be the second next step @en