One of the major roadblocks our culture has in regards to space travel is that in order to travel at speeds that could make a trip to a distant planet or star in a reasonable time frame is the application of energy: currently, we’re stuck burning chemical fuel to propel our vehicles, of which means also lugging that fuel along with the vehicle, meaning the vehicle weighs more because of the extra fuel, meaning the vehicle has to carry more fuel to offset that weight — it unfortunately becomes a cycle of inefficiency, making for a very slow vehicle.
We get around this problem with current space probes by not including a propulsion system with them, but rather boosting them with most of the energy they need for their trip at the start of the journey. But at the interplanetary distances that these probes have to traverse, these speeds are still extremely slow: a trip to Mars is measured in months, and despite making a beeline from Jupiter to Pluto, New Horizon’s journey took the better part of a decade. But there may be a way to dramatically increase the speed of our spacecraft, using an adaptation on the idea of a solar sail.
Speaking on the NASA 360 video program, University of California physics professor Philip Lubin outlines his idea of using a combination of next-generation lasers and cutting edge lightweight reflective materials to build a laser-powered sail that, according to his calculations, should be able to reach 30 percent of the speed of light within ten minutes. He argues that we accelerate particles using particle accelerators to relativistic speeds in the laboratory routinely: why not scale up the effect to the macroscopic scale?
Provided he is able to secure funding for his project, he plans to scale the concept upward in size over a series of phases, starting with lightweight, wafer-thin space probes, and eventually building up to a 1,000-kilogram (one ton) spacecraft with a 10-km (6.2 mile) sail, driven by a 50-100-gigawatt laser. He also proposes that the system’s power could be multiplied by having the light that the spacecraft’s sail reflects back to the laser re-reflected back to the ship, pulling even more power out of each individual photon through multiple bounces.
The laser’s power requirements would be comparable to what is expended in the 10-minute launch of a space shuttle, but the efficiencies involved would produce speeds that would be much, much greater, enabling a probe to be sent to Mars in a matter of days, or the nearest star in a little over a decade.
There will be limitations to such a propulsion method: the vehicles will need to be built as lightly as possible, making it better suited for robotic probes, rather than manned missions. Their voyages will also be one-way, since there wouldn’t be another laser at the destination to send it back. But the capacity to accelerate even a small probe to these proposed speeds could prove to be invaluable for near-term space exploration, both in terms of resource cost and travel time.