It will take humanity’s fastest spacecraft thousands of years to reach even the nearest stars. The Breakthrough Initiatives have been investigating ways to reduce this to just a few decades, potentially allowing the scientists who initiate the mission to witness its outcomes. A new paper, published in the Journal of the Optical Society of America B, demonstrates that one of the major challenges for such a project can be addressed using current technology, though the authors acknowledge that other obstacles remain.
The more massive an object, the harder it is to accelerate, especially as it nears the speed of light—a significant issue for any spacecraft carrying its own fuel.
Alpha Centauri, the closest star and planetary system to Earth, is 4.37 light-years away. With current technology, it would take a human around 6,000 years to reach it.
“To cover the vast distances between Alpha Centauri and our own Solar System, we must think outside the box and forge a new way for interstellar space travel,” Dr. Chathura Bandutunga of the Australian National University said in a statement. Lightweight missions could receive an extraordinarily powerful push and then continue their journey independently.
The concept of using lasers for propulsion has been discussed for decades but is now gaining serious attention through the Breakthrough Starshot project. While many challenges remain to make this feasible, Bandutunga asserts that the Earth’s atmosphere does not need to be a roadblock.
The twinkling of stars reminds us how much the atmosphere distorts incoming light. These same distortions can affect laser beams aimed upwards, potentially disrupting the force needed to propel a spacecraft. Some proponents have proposed placing the launch system on the Moon, but the cost of such a venture would be, quite literally, astronomical.
Bandutunga is the lead author of the paper, which argues that the adaptive optics telescopes use to correct atmospheric distortion can be reversed. A small satellite-mounted laser, pointed at Earth, could measure atmospheric effects in real time, enabling the much more powerful ground-based lasers to adjust and maintain their focus on the spacecraft.
“Vastly more powerful” is no exaggeration. Previous studies have shown that the lasers would need to deliver 100GW of power to the spacecraft. For perspective, the entire United States consumes an average of 450GW of electricity at any given moment.
Bandutunga and co-author Dr. Paul Sibley remain optimistic. “It only needs to operate for 10 minutes at full power,” they told IFLScience. “So we imagine a battery or supercapacitors that can store energy built up over several days and release it suddenly.” The energy would be generated by 100 million lasers spread across an area of one square kilometer.
Image Credit Breakthroughs Institute
This enormous power would be focused on an object no larger than 10 meters (33 feet) across. Once the lasers are turned off, the spacecraft would be traveling at roughly 20 percent of the speed of light. With minimal slowing from the Sun’s gravity and interstellar medium, it could reach Alpha Centauri in approximately 22 years, although its transmissions would take an additional four years to arrive back on Earth.
Preventing the probe from melting is “definitely one of the remaining big challenges,” Bandutunga and Sibley admitted to IFLScience. To address this, the probe would need to be a nearly flawless mirror, reflecting 99.99 percent of the incoming light. This would not only reduce heat but also double the momentum transfer.
The probe would travel through the Alpha Centauri system in just a few days, likely without approaching any planets closely. However, the advantage of this concept is that, once the launch system is constructed, sending additional probes would become relatively inexpensive. A fleet of probes could be dispatched to nearby star systems, increasing the chances of one obtaining a close—albeit brief—view of any Earthlike planets.
Image Credit Breakthrough Institute.
