No longer only in the realm of science fiction, the possibility of interstellar travel has appeared, tantalizingly, on the horizon. While we might not see it in our lifetime – at least not an actual version of the chain-speed, hyper-driving, spatial-folding fictional genre – we have the first conversations about how life might escape the tether. of our solar system, using technology that is at our fingertips.
For UC Santa Barbara professors Philip Lubin and Joel Rothman, now is the perfect time to be alive. Born from a generation that saw breathtaking advancements in space exploration, they carry the unbridled optimism and creative spark of the start of the space age, when humans first discovered that they could leave Earth.
âThe trips to the Apollo moon were among the most important events of my life and to contemplate them always amazes me,â said Rothman, distinguished professor in the Department of Molecular, Cellular and Developmental Biology, and a âgeek. of space “self-admitted.
Barely 50 years have passed since this pivotal era, but humanity’s knowledge of space and the technology to explore it have improved dramatically, enough for Rothman to join experimental cosmologist Lubin in thinking about what ‘it would take living things to undertake a journey through the great distance separating us from our nearest neighbor in the galaxy. The result of their collaboration has been published in the journal Acta Astronautica.
âI think it’s our fate to keep exploring,â Rothman said. âLook at the history of the human species. We are exploring on smaller and smaller levels down to subatomic levels and we are also exploring on larger and larger scales. Such a drive for relentless exploration is at the heart of who we are as a species. “
Think big, start small
The biggest challenge of interstellar travel on a human scale is the enormous distance between Earth and the nearest stars. The Voyager missions have proven that we can send objects the 12 billion kilometers it takes to break out of the bubble surrounding our solar system, the heliosphere. But the car-sized probes, traveling at speeds of over 35,000 miles per hour, have taken 40 years to achieve this, and their distance from Earth is only a tiny fraction of that of the next. star. If they were heading for the nearest star, it would take them over 80,000 years to reach it.
This challenge is a major focus of Lubin’s work, in which he reinvents the technology it would take to reach the next solar system in human terms. Traditional on-board chemical propulsion (aka rocket fuel) is phased out; it cannot provide enough energy to move the craft fast enough, and its weight and the current systems needed to propel the ship are not viable for the relativistic speeds the craft must achieve. New propulsion technologies are needed – and this is where the UCSB-led energy research program to use light as a âpropellantâ comes in.
âThis has never been done before, to push macroscopic objects at speeds approaching the speed of light,â said Lubin, a professor in the physics department. The mass is such a huge barrier, in fact, that it precludes any human mission for the foreseeable future.
As a result, his team turned to robots and photonics. Small probes with on-board instrumentation that detect, collect and transmit data to Earth will be propelled up to 20-30% of the speed of light by the light itself using a laser array parked on Earth, or maybe on the moon. âWe don’t leave home with it,â as Lubin explained, meaning that the main propulsion system stays âat homeâ while spacecraft are âpulledâ at relativistic speeds. The main propelling laser is turned on for a short time, then the next probe is ready to be fired.
âIt would probably look like a semiconductor wafer with an edge to protect it from radiation and dust bombardment as it passes through the interstellar medium,â Lubin said. “It would probably be the size of your hand to begin with.” As the program evolves, the spacecraft gets bigger with improved capacity. The core technology can also be used in a modified mode to propel much larger spacecraft through our solar system at slower speeds, potentially allowing human missions to ">March in less than a month, including shutdown. It is another way of spreading life, but in our solar system.
At these relativistic speeds – about 100 million miles per hour – the wafercraft would reach the next solar system, Proxima Centauri, in about 20 years. Achieving this level of technology will require continued innovation and improvement in both the space wafer, as well as photonics, where Lubin sees “exponential growth” in the field. The core project to develop a roadmap for achieving relativistic flight via directed energy propulsion is supported by ">Nasa and private foundations such as the Starlight program and by Breakthrough Initiatives such as the Starshot program.
âWhen I learned that the mass of these contraptions could reach grams or more, it became clear that they could accommodate live animals,â said Rothman, who realized that the creatures he was studying for decades, called C. elegans, could be the first Earthlings to travel between the stars. These intensively studied roundworms may be small and simple, but they are experimentally accomplished creatures, Rothman said.
“Research on this small animal has so far led to Nobel Prizes for six researchers,” he noted.
The C. elegans are already veterans of space travel, having been the subject of experiments conducted on the International Space Station and aboard the Space Shuttle, even surviving the tragic disintegration of the Columbia shuttle. Among their special powers, which they share with other potential interstellar travelers that Rothman studies, tardigrades (or, more affectionately, water bears) can be placed in suspended animation in which virtually all metabolic functions are shut down. Thousands of these tiny creatures could be placed on a wafer, animated suspended, and stolen in this state until they reach their desired destination. They could then be awakened in their tiny StarChip and precisely monitored for any detectable effect of interstellar travel on their biology, with the observations being relayed back to Earth via photon communication.
“We can ask them how well they remember trained behavior as they move away from their earthly origin at near light speed, and examine their metabolism, physiology, neurological function, reproduction and aging, âRothman added. “Most of the experiments that can be done on these animals in a lab can be done on board the StarChips as they travel through the cosmos.” The effects of these long odysseys on animal biology could allow scientists to extrapolate to the potential effects on humans.
“We could start thinking about designing any interstellar transporters, whatever they are, in a way that could improve the problems detected in these small animals,” said Rothman.
Sure, being able to send humans into interstellar space is great for movies, but in reality, it’s still a distant dream. By the time we get to this point, we may have created more suitable life forms or more resilient human-machine hybrids, Lubin said.
âIt’s a generational program,â he said. Scientists for generations to come will ideally contribute to our knowledge of interstellar space and its challenges, and improve the design of the craft as technology improves. With the main propulsion system being light, the underlying technology is on an exponential growth curve, much like electronics with a capacity for expansion similar to âMoore’s Lawâ.
Planetary protection and alien propagation
We are tied to our solar system for the foreseeable future; humans are fragile and delicate far from our home planet. But that did not stop Lubin, Rothman, their research teams and their various collaborators, including a radiation specialist and a science-trained theologian, from considering both the physiological and ethical aspects of sending life. in space – and possibly even the spread of life. in the space.
âThere is the ethics,â explained Lubin, âof planetary protection,â in which we seriously consider the possibility of contamination, either from our planet to others, or vice versa. “I think if you started talking about the directed spread of life, which is sometimes called panspermia – this idea that life came from somewhere else and ended up on earth through comets and other debris, or even intentionally from another civilization – the idea of ââdeliberately sending us life raises big questions.
So far, the authors say, there is no risk of direct contamination, as probes near any other planet would burn in their atmosphere or be erased upon collision with the surface. Since the wafercrafts are one-way, there is no risk of an alien microbe returning to Earth.
Although still somewhat marginal, the panspermia theory appears to be attracting serious, albeit limited, attention given the ease of propagation of life when the conditions are right and the discovery of several exoplanets and other celestial bodies that could have be, or could be, supportive of life as we know it.
âSome people have reflected on and published ideas like ‘is the universe a laboratory experiment of an advanced civilization’,â said Lubin. âSo people are certainly ready to think of advanced civilizations. The questions are good, but the answers are better. Right now, we are just thinking about these questions without the answers yet. “
Another question currently being considered in the larger space exploration community: What is the ethics of sending humans to Mars and other remote places knowing that they may never return home? What about sending small microorganisms or humans DNA? These existential inquiries are as old as the first human migrations and sea voyages, the answers to which will probably come when we are ready to undertake these voyages.
âI think we should not, and will not suppress, the exploratory desire that is intrinsic to our nature,â Rothman said.
Reference: âInterstellar Space Biology via Project Starlightâ by Stephen Lantin, Sophie Mendell, Ghassan Akkad, Alexander N. Cohen, Xander Apicella, Emma McCoy, Eliana Beltran-Pardo, Michael Waltemathe, Prasanna Srinivasan, Pradeep M. Joshi, Joel H. Rothman and Philip Lubin, October 15, 2021, Acta Astronautica.
DOI: 10.1016 / j.actaastro.2021.10.009