Interstellar travel is no longer confined to the realm of science fiction, but it has
emerged as an exciting prospect.
While we may never see a real-world version of the fictional warp-speeding, hyperdrive,
space-folding type, scientists are having early discussions about how life could break
free from the confines of our solar system using technology that is within our grasp.
It’s an exciting time to be alive for UC Santa Barbara academics Philip Lubin and Joel
Rothman.
They were born into an age that witnessed astonishing breakthroughs in space travel,
and they embody the unrestrained optimism and creative spark of the early Space Age
when humanity first discovered they could leave the Earth.
For Joel Rothman, the Apollo moon voyages were among the momentous events in his life,
and contemplating them still blows his mind.
Even though 50 years have passed since that pivotal era, human knowledge of space and
the technology to explore it has improved dramatically, allowing Rothman and experimental
cosmologist Lubin to consider what it would take for living beings to travel the vast
distance that separates us from our nearest galaxy neighbor.
The main challenge to human-scale interstellar travel is the vast distance between our planet
and the closest stars.
The Voyager missions have shown that humans can send objects across the 12 billion miles
needed to leave the heliosphere, the bubble that surrounds our solar system.
However, the car-sized probes took 40 years to get there, traveling at speeds of more
than 35,000 miles per hour, and their distance from Earth is only a minuscule fraction of
the distance to the next star.
It would take them over 80,000 years to travel to the nearest star.
This challenge is the main focus of Lubin’s work, in which he reimagines the technology
required to reach the next solar system in human terms.
Traditional onboard chemical propulsion, also known as rocket fuel, is out; it can’t generate
enough energy to propel the craft fast enough, and its weight and present systems are not
suitable for the relativistic speeds the craft needs to achieve.
New propulsion technologies are needed, and this is where the UCSB directed energy research
program of using light as a “propellant” comes in.
Pushing macroscopic objects at speeds approaching the speed of light has never been done before.
Human missions are out of the question for the foreseeable future because of the huge
barrier, mass.
Consequently, Lubin’s team shifted to robots and photonics.
Small probes with onboard instrumentation that sense, collect, and communicate data
back to Earth will be propelled up to 20-30% of the speed of light by a laser array stationed
on Earth or maybe the moon.
The primary propulsion system stays “at home” while the spaceship is “blasted
out” at relativistic speeds.
The primary propulsion laser is turned on for a short period, and the next probe is
prepared for launch.
It would most likely resemble a semiconductor wafer with a protective edge to shield it
from radiation and dust bombardment as it travels through the interstellar medium.
As the program progresses, the spacecraft become big with enhanced capability.
The fundamental technology may also be adapted to propel much larger spacecraft at slower
speeds within our solar system, perhaps allowing human voyages to Mars in as little as one
month, including stops.
This is another way of life spreading in our solar system.
The wafercraft would reach the next solar system, Proxima Centauri, in about 20 years
if it traveled at relativistic speeds, roughly 100 million miles per hour.
To reach that level of technology, both the space wafer and photonics will need constant
innovation and improvement.
When Rothman discovered that the mass of this craft might reach gram levels or higher, it
became clear that they could carry living beings.
He concluded that the creatures he’d been researching for decades, called C. elegans,
might be the first Earthlings to travel between the stars.
These extensively researched roundworms may be tiny and plain, but they are experimentally
accomplished creatures.
C. elegans have already traveled to space as the subject of studies on the International
Space Station and aboard the space shuttle, even surviving the Columbia shuttle’s terrible
disintegration.
Tardigrades, or more affectionately, water bears, have a remarkable ability that they
share with other prospective interstellar travelers: they can be placed in suspended
animation, which practically stops all metabolic function.
Thousands of these tiny creatures could be placed on a wafer, put in suspended animation,
and flown until they reached their destination.
They could then be awoken in their little StarChip and meticulously monitored for any
detectable interstellar travel effects on their biology, with the observations communicated
to Earth via photonic communication.
Of course, being able to send humans to interplanetary space is fantastic in movies, but it remains
a far-fetched goal in reality.
By the time we reach that stage, we may have developed more suitable life forms or hybrid
human machines that are more resilient.
The next generation of scientists will ideally contribute to our understanding of interstellar
space and its obstacles, and improve the architecture of the craft as technology advances.
The underlying technology is on an exponential development curve similar to electronics with
a “Moore’s Law” like expanding capability.
Humans are weak and vulnerable away from our home planet, but that hasn’t stopped researchers
from thinking about the physiological and ethical implications of sending life to space
and possibly even propagating life in space.
Another issue currently under discussion in the wider space exploration community is:
what are the ethics of sending humans to Mars and other far-off destinations knowing they
may never return?
What about sending microorganisms or human DNA?
These experiential questions date back to the first human migrations and sea trips,
and the answers will most likely arrive when we’re ready to embark on these adventures.