Fast Solar System transportation with electric propulsion powered by directed energy

Design of a rapid transit to Mars mission using laser-thermal propulsion

“…As a consequence, the propulsive maneuver for laser-electric propulsion missions typically requires days to weeks, which for continuous power delivery would necessitate multiple laser sites on Earth or construction of a laser array in space. The laser-electric missions considered in [8] also necessitated larger arrays (750 to 1000 m in effective diameter) in comparison to the present study's 10-m array for the same class of payload. Our preliminary conclusion is that, as larger laser arrays become available, laser-electric offers the greatest benefits, but for early application of phasedarray lasers with 10-m-scale laser arrays, laser-thermal may offer a greater potential to realize missions with significant payloads.…”

“…Enabled by shorter laser wavelength and the ability to operate as a phased array of unprecedented optical dimensions, laser-thermal propulsion can now be extended two orders of magnitude deeper into cislunar space than previously considered in the 1970s and 1980s. A second advantage that this proposed architecture capitalizes upon is the laser fluxes that are permissible upon the inflatable reflector, which exceed by two orders of magnitude the flux limitations on laser-electric propulsion with no active cooling [7,8]. These high fluxes allow laser-thermal propulsion to "burn hard" early in the mission, while the spacecraft is still within the focal length of the laser, enabling high ∆v missions with 10-m-scale lasers.…”

“…The present study suggests that aerocapture with an approach hyperbolic excess velocity of 15 km/s is feasible with current thermal protection materials and vehicle designs within the state of the art. Several of the LEP flyby missions presented in [8] could thus be turned into orbit transfer missions. Aerocapture maneuvers could be considered for any target with a sufficiently dense atmosphere.…”

“…For a mission ∆v of 15 km/s and an efficiency η of 90%, the payload mass fraction of both laser-thermal and laser-electric propulsion systems are plotted in Figure A.1. Fixed specific impulses were assumed for this comparison, assuming 10 000 s for laserelectric systems as per [8].…”

“…More near-term applications of directed energy for interplanetary flight are better suited to using a reaction mass to couple the delivered laser energy to change the momentum of the spacecraft. Options using laser-based directed energy are laser-electric propulsion [7,8] and laser-thermal propulsion (LTP 1 ). Laser-thermal propulsion is further classified into (1) laser ablation propulsion using an initially condensed-phase reaction mass [9] and (2) laser-thermal propulsion with a gaseous propellant (typically hydrogen) that is heated and expanded through a nozzle.…”