Interstellar travel is time-consuming. A group of astronomers and physicists are playing with making it faster, starting with massive lasers and one of Earth’s most resilient organisms: the tardigrade.
These microscopic aquatic animals, sometimes called “water bears”, are nearly indestructible, capable of withstanding drought, freezing temperatures, accidents, high levels of radiation, harsh pressure and gravity conditions and suspended animation—the slowing of biological functioning for long periods of time. This makes them the perfect candidate for experiments in ramping up the speed of space travel, write researchers in a new paper published in the peer-reviewed journal Acta Astronautica.
Travelling 18-billion kilometers to the end of our solar system currently takes decades using traditional means of chemical propulsion—the burning of fuel. But, with funding from NASA, researchers at the University of California - Santa Barbara have proposed a new means of space propulsion using lasers (“directed-energy” or DE arrays) on Earth that push light sails attached to spacecraft using photons to travel at a rate that’s 20 to 30 percent of the speed of light, achieving relativistic flight. Launched in 2015 via an initiative called Project Starlight, the effort aims to cut travel time to interstellar space from decades to days, all without the use of an onboard propellant.
Now, a team of researchers including Philip Lubin, professor of physics at UC Santa Barbara and lead researcher on Project Starlight, have teamed up to propose a path forward for testing relativistic flight. They propose putting tardigrades, alongside closely-related resilient invertebrates like C. Elegans, on wafer-scale platforms around the size of a human hand, which would be deployed into space at roughly 100 million miles per hour. According to the paper, the power for the laser array could consume 1/10 of the entire U.S. energy grid, but this power would only be needed for a few minutes during launch.
"This has never been done before, to push macroscopic objects at speeds approaching the speed of light,” Lubin, co-author of the paper, said in a press release.
Diagram of a spacecraft being propelled by an Earth-based directed energy array. Image: Lantin et. al.
They propose performing remote experiments on the organisms while on board, studying how tardigrades and other Earthlings handle life in the harsh conditions inherent to distant space realms. Lubin and his team could then extrapolate these findings to assess potential effects of interstellar travel on humans.
“We could start thinking about the design of interstellar transporters, whatever they may be, in a way that could ameliorate the issues that are detected in these diminutive animals,” said Joel Rothman, co-author on the paper and distinguished professor in biomolecular science and engineering at UCSB in the press release.
The authors have weighed the ethical implications of propagating Earth life in space—and, similarly, the risks of bringing life from other star systems back to Earth, which is known as “backward contamination.” Crucially, Lubin and Rothman propose making any tardigrade-loaded space crafts one-way, performing all studies completely remotely to ensure that no extraterrestrial microbes return to Earth.
Ethical considerations are all part of the process of envisioning life beyond Earth, and beyond our currently imagined methods of travel. These considerations are among many that Lubin and Rothman are keen to consider. Indeed, while the plan is to start small, the authors note in the paper that laser propulsion could be used on larger ships, and that the arrays could be built on objects in space and not just on Earth.
“I think it's our destiny to keep exploring,” Rothman said. “We explore at smaller and smaller levels down to subatomic levels and we also explore at increasingly larger scales. Such drive toward ceaseless exploration lies at the core of who we are as a species.”