My regular readers appreciate the fact that NASA is partnering with a number of commercial space businesses to permanently expand the human frontier into cis-Lunar space. While $20 billion in federal funding drives NASA’s amazing programs, the agency doesn’t get that money without strong public support. NASA has also long been supported by the National Space Society, a group founded by Werner von Braun. I’m proud to represent NSS as their Vice President of Space Development and to have chaired their International Space Development Conference this year. I’m also a huge fan of the Moon Village Association, which is helping to pave an international path for lunar settlement. The Southern California Commercial Spaceflight Initiative, which I direct at USC, hosted both those groups in a fantastic event last year. I’m excited to note that we will bring in the Mars Society this fall. That organization, founded by Robert Zubrin, leads the push for our next step, colonizing the Red Planet. You may however, be less familiar with the small group of aspirational space visionaries already working on conquering the stars, or with Tau Zero, the foundation dedicated to achieving that most audacious goal.
Anyone following headline space news stories is aware that space telescopes like Keplerand TESS have confirmed the suspicions of Carl Sagan and other visionaries, that our galaxy is swarming with billions of exoplanets. While detecting or possibly even visualizing distant worldsis within the realms of science, travel to those distant world’s presents such enormous challenges that it is usually dismissed as science fantasy. Building a workable interstellar propulsion system presents technical obstacles that make NASA’s ambitious Artemis moon program seem easy. As Seneca the Younger, wrote, “there is no easy way from the Earth to the stars” (non est ad astra mollis e terris via).
Rocket propulsion expert Jeff Greason puts this into context, “Chemical rockets will not get us to the stars and current nuclear propulsion ideas could barely scratch it.” We are going to need entirely new tech and the effort and investment required to design and perfect it will deliver multi-fold returns to those of us who will never leave the Earth. Beyond the obvious thrill of traveling to the stars and the satisfaction of expanding humanity beyond our home system, overcoming such a huge challenge will drive a variety of positive externalities. Our efforts to launch satellites and humans starting in the 1960s resulted in improved communications, weather prediction, navigation and power solutions that benefit our planet and everyone on it.
The pursuit of interstellar transportation will surely generate new spin-offs and ones of greater magnitudes. As Greason explains, “Building civilization from agriculture through coal and oil and nuclear power, has been essentially about learning how to collect energy, store it, transmit it, and work with it.” Interstellar flight will require breakthroughs in all those areas because getting to the stars requires incredible speed. “What makes interstellar flight so demanding, and at the same time so powerful, is that objects moving at speeds of 20 percent of the speed of light must have a lot of kinetic energy in them – something like 25 Hiroshima bombs for each kilogram of ship mass.” A civilization that can do that will make astounding progress in every other realm. The global economic and environmental challenges that currently bedevil our society will seem Paleolithic to a starfaring society.
While solid theoretical work on realistic interstellar transportation systems exists, this research has been done by talented amateurs and academics working in their spare time. There has never been a systematic program of research to tackle the hard problems of such powerful propulsion, and virtually no financial support. The Tau Zero Foundation exists to solve this problem. The nonprofit led by Greason focuses on pioneering interstellar flight by finding revolutionary gains. They’ve got a plan and have identified researchers in diverse fields, ready to tackle the challenges. “We’ve selected several specific opportunities where reasonable philanthropic funding would drive real progress, even in the absence of government support,” explains Greason. He adds that NASA’s Institute of Advanced Concepts (NIAC) has sponsored work that is worth building on.
Breakthrough Starshot funded by Russia’s most influential tech investor, Yuri Milner, is the highest profile effort at interstellar flight. Announced in 2016, Starshot plans to use an array of high-power lasers to create a kilometer-wide 100 gigawatts beam that will drive super-lightweight spacecraft at incredible speeds. The pressure of light itself will accelerate these paperclip-massed craft to 20 percent of the speed of light. Not surprisingly, that won’t be easy. Starshot must fund the enormous cost of superpowered lasers and fabricate gossamer-like material for light sails that can capture the beam power without melting and still handle extreme accelerations. Returning data from such a tiny craft over the great distances between the stars is no small feat either. Starshot is a super-highspeed flyby mission. These probes will literally blast through the target system in hours, offering no opportunity for taking a closer and longer look at anything interesting.
“There’s no question that beams of one kind or another are an important tool in the toolbox for highspeed flight,” explains Greason. Generating energy on the Earth, moon or space platform and applying it to a craft not burdened with the weight of the generators is an excellent way to achieve really good acceleration. Alternately, pellets of fusion fuel might be sent with a much smaller beam, because the fusion reaction would deliver more total energy than the beam itself. Greason notes, “In beam propulsion, generating and powering the beam is the most expensive part, so any way that you can make the beam cheaper is worth exploring.”
Another big idea is to use antimatter as fuel and that’s not just a Star Trek contrivance. Antimatter is the densest form of energy storage we know about. “If you could convert 2 percent of the mass of a ship into propulsive energy, you could achieve 20 percent of lightspeed.” Still, generating antimatter takes an enormous amount of energy applied to particle accelerators, and that’s expensive. Greason notes there are hybrid models that could reduce the required amount of antimatter, “A lot of interesting approaches use the antimatter more as a spark-plug for a nuclear reaction that powers the ship.”
Once you have a ship traveling at a significant proportion of c, the next challenge is stopping without crashing. Having some brakes on a probe would allow it to enter orbit around the target star, sending back data for years and allowing scientist to carefully investigate the most interesting targets the spacecraft encounters. “As you start thinking about very highspeed flight, the space between the stars and planets no longer seems so empty, because the dynamic pressure increases with your speed,” Greason explains. “There are always a few gas molecules spread out there along with solar wind coming off the stars. That’s very important when thinking about slowing down.” Greason explains that engineers could “scoop up” this interstellar medium for propulsive energy and reaction mass.
In the near term, technologies developed for interstellar flight could revolutionize what we can do here in the solar system, long before we send interstellar probes. “One percent of the speed of light is something we can get to a lot sooner, and that gets us to Jupiter in weeks and out to Pluto in nine months instead of nine years,” explains Greason. Instead of an outer-planet flyby as a once-in-a-career event for a scientist, such missions could be launched every couple of years. “We could get back to Neptune, start visiting the outer edges of the Solar System out to the Oort cloud, where comets are born. We’ve never seen that.” Better yet, these months-old probes would be equipped with the latest sensors, computing hardware and communications systems. Deep space researchers have always been frustrated by the fact that technology progresses faster than their spacecraft fly, and even the best spacecraft are electronic antiques by the time they reach their destinations.
In the meantime, better data on what’s between the stars and answers to other scientific questions are needed. “We know the gas cloud around the Sun is a measurably different cloud from the one we see around Alpha Centauri, but we’re just beginning to really understand that as the 1970s vintage Voyager probes pass out of the heliosphere.
Once you get out that far, the mass of the Sun itself could be used as a gravitational lens to create the most powerful telescope ever imagined. Such a scope would make the Hubble and James Webb instruments look like a child’s magnifying glass. Placing an imager at the focal point, about 20 times farther away than Neptune, could yield the stunning images of extrasolar planets we’d all love to see.
A proto-interstellar drive would make these amazing things possible, and so much more. The Tau Zero team is working to get us there. Please consider supporting them and the other space non-profits that are dedicated to helping us all find a brighter future.