Arrays of lasers can be used to push light weight solar sails to other stars. This has been funded with over $100 millon and it builds upon the technology of the $600 billion laser and photonics industry. A recent paper looks at how different technological improvements will make it more feasible and improve the costs. Integrated photonics and mass production of most of the modular systems will be fundamentally necessary to afford the full-scale realization of this vision. Researchers have derived an analytical cost model which is driven by the fundamental physics of the proposed system. This allows us to make economically informed decisions and create a logical path forward to interstellar flight.

Large scale directed energy offers the possibility of radical transformation in a variety of areas, including the ability to achieve relativistic flight that will enable the first interstellar missions, as well as rapid interplanetary transit. In addition, the same technology will allow for long-range beamed power for ion, ablation, and thermal engines, as well as long-range recharging of distant spacecraft, long-range and ultra high bandwidth laser communications, and many additional applications that include remote composition analysis, manipulation of asteroids, and full planetary defense. Directed energy relies on photonics which, like electronics, is an exponentially expanding growth area driven by diverse economic interests that allows transformational advances in space exploration and capability. We have made enormous technological progress in the last few years to enable this long-term vision.

In addition to the technological challenges, we must face the economic challenges to bring the vision to reality. The path ahead requires a fundamental change in the system designs to allow for the radical cost reductions required. To afford the full-scale realization of this vision we will need to bring to fore integrated photonics and mass production as a path forward. Fortunately, integrated photonics is a technology driven by vast consumer need for high speed data delivery. they outline the fundamental physics that drive the economics and derive an analytic cost model that allows us to logically plan the path ahead.

For relativistic flight (over 10% of lightspeed) development of powerful lasers to push ultra-low mass probes is needed. Recent developments now make both of these possible. The photon driver is a laser phased array which eliminates the need to develop one extremely large laser and replaces it with a large number of modest laser amplifiers in a MOPA (Master Oscillator Power Amplifier) configuration with a baseline of Yb amplifiers operating at 1064 nm. The system is phase locked using a coherent
beacon that is either carried by the spacecraft or reflects off the spacecraft. Maintaining phase integrity is one of the key challenges. This approach is analogous to building a super computer from a large number of modest processors. This approach also eliminates the conventional optics and replaces it with a phased array of small low cost optical elements. As an example, on the eventual upper end, a full scale system (50-100 GW) will propel a wafer-scale spacecraft with a meter class reflector (laser sail) to about c/4 in a few minutes of laser illumination allowing hundreds of launches per day or 100,000 missions per year. Such a system would reach the distance to Mars (1 AU) in 30 minutes, pass Voyager I in less than 3 days, pass 1,000 AU in 12 days, and reach Alpha Centauri in about 20 years.

The same system can also propel a 100 kg payload to about 1% of lightspeed and a 10,000 kg payload to more than 1,000 km/s, though there is a practical trade space of using DDM vs IDM for larger mass spacecraft.

There are other applications for large laser arrays and long range power beaming. Power can be beamed power for ion engine systems, distant spacecraft recharging (eliminating RTG’s in some cases), full standoff planetary defense against both asteroids and comets, solar system wide active illumination or laser scanning (LIDAR) to find and study smaller objects, asteroid manipulation and composition analysis, terraforming applications, and a path to extremely large telescopes.

Beaming power to power ion engines, enables high speed maneuvering beyond Jupiter.