Spaceflight Insider

Tennessee Valley Interstellar Workshop taking the long view to the stars

Artist’s impression of a planet around Alpha Centauri B

This artist’s impression shows a hypothetical planet orbiting the star Alpha Centauri B, a member of the triple star system that is the closest to Earth. Image Credit: ESO / L. Calçada / Nick Risinger

HUNTSVILLE, Ala. — While NASA and commercial operators plan to send human beings beyond low-Earth orbit, the participants of the Tennessee Valley Interstellar Workshop (TVIW) spent this past week contemplating something incomparably more ambitious: seeking practical ways to travel to the stars.

Ahead of the curve

The TVIW Chairman Les Johnson is a NASA physicist by day and a science fiction writer and interstellar visionary in his free time. Given that the exploration of the Solar System will be the work of generations, if not centuries, might TVIW not be getting a little ahead of themselves? Johnson told Spaceflight Insider: “Not at all. We’re providing the long-term vision… Can we do it today? No. Can we begin developing the technologies needed? Yes. Can we think about flying precursor missions today? Yes.”

The practical question Johnson and the other approximately 150 TVIW attendees asked was, “What can be done now?They realize that launching even a tiny payload to the nearest star—Alpha Centauri, 4.3 light-years away—requires considerable development and expense.

Breakthrough Starshot 'StarChip'

A StarChip. Photo Credit: Zac Manchester / Breakthrough Initiatives

One starting point is the Breakthrough Starshot, a program suggested by physicist Stephen Hawking and now being funded by internet investor and philanthropist Yuri Milner, among others. The Starshot mission is ambitious, as one might expect: launch a payload weighing no more than one gram—essentially a computer chip with miniaturized sensors aboard—to Alpha Centauri at 20 percent of the speed of light (37,256 miles / 59,957 kilometers per second) within a generation.

Without breaking any laws of physics or requiring magical solutions like nuclear fusion, antimatter, or Star Trek’s “warp drive”, the Starshot founders and TVIW attendees believe such a mission may be possible by the year 2040.

What will it take to launch a payload not much bigger than your average snack cracker to another star? Starshot researchers are considering an ultra-lightweight sail tens of meters wide, propelled by a square-kilometer array of lasers based on Earth.

Once launched into Earth orbit by a conventional rocket, the Starshot sail will unfurl. The sail’s deployment could resemble a NASA program Les Johnson leads, the Near Earth Asteroid Scout (NEA Scout), which will fly as a secondary payload aboard the Space Launch System (SLS).

While NEA Scout uses the Sun as its source of photons, Breakthrough Starshot will ride lasers putting out as much as 100 gigawatts of power from a site in the Southern Hemisphere for anywhere from two to twelve minutes. Acceleration occurs because photons have momentum, and the concentrated light of lasers reflecting from the sail provides enough momentum to accelerate Starshot rapidly. It will reach its target speed of 0.2 light speed (c) by the time it reaches the orbit of Mars.

Science or science fiction?

Even though eminent science fiction writers such as Larry Niven, Gregory Benford, and Allen Steele attended TVIW, the event concentrated on practical concerns rather than fanciful storytelling.

Consider cost. While Yuri Milner is pledging $100 million for initial laboratory studies and simulations, the Starshot mission’s targeted price tag is $10 billion. This includes developing and building the sail, the lasers, and the miniaturized StarChip.

Lasers have existed since 1960 and solar sails have flown since 2010. However, Starshot’s sheer scale puts them in a new category altogether. The laser array alone poses potential global security issues. The most powerful laser the U.S. developed as part of the Strategic Defense Initiative was in the megawatt range. Starshot’s square-kilometer laser array, firing in the 100 GW range, could vaporize a satellite.

Video courtesy of Breakthrough


U.S. Congressmen John Culberson (TX) and Mo Brooks (AL) both attended the meeting on October 7. Culberson did not address the national security question directly and Brooks admitted, “I’d need more information before I could offer an opinion.”

Despite silence on the security question, both Culberson and Brooks expressed support for interstellar-related missions and technology development. Culberson was especially enthusiastic about a mission to Jupiter’s moon Europa, which he wrote into the NASA Authorization Act of 2017. However, both congressmen also sounded a note of caution, given the federal government’s increasing expenditures and deficits. Culberson advocated the “need to unleash American creativity and ingenuity” to grow the economy and ensure that interstellar travel is feasible in the future.

Solar Sail Spacecraft concept

NASA illustration of the unlit side of a half-kilometre solar sail, showing the struts stretching the sail. (Click to enlarge) Image Credit: NASA

So when do we get the starship Enterprise ?

While many TVIW talks covered Breakthrough Starshot, the attendees’ long-term vision naturally includes sending humans to other star systems. However, any propulsion system capable of launching humans to the stars will require unprecedented power.

A space-based laser capable of launching a human-scale sail ship needs 43,000 terawatts to push a sail 621 miles (1,000 kilometers) in diameter. As a point of comparison, the United States generated just over 4.3 terawatts during all of 2016.

Likewise, one of science fiction’s favorite power sources, antimatter, is produced worldwide at a rate of 0.00000000007 (7 × 10-11) ounces, or 2 nanograms, per year. To send a 22-pound (10-kilogram) payload to Alpha Centauri would require 0.35 ounces (17 grams) of antimatter.

All this is before you start getting into magical technologies like faster-than-light travel.

It’s not just a matter of getting to speeds useful for interstellar travel in a single human lifetime. Other problems TVIW participants considered included crew health and social stability, biological compatibility of alien life, and debris deflection.

Starships built to keep entire societies healthy for decades or centuries need to balance safety, health, and freedom. Alien planets filled with tasty plants or animals could still cause malnutrition if their amino acids are incompatible with ours. Single dust particles striking a starship at relativistic speeds produce impacts akin to atomic bomb explosions. And so forth.

Humanity can solve many of the problems associated with interstellar travel while still within our own Solar System. However, TVIW Chairman Les Johnson feels that the interstellar quest is a natural human activity: “How can you look at the stars, think about all the exoplanets we’re finding, and not wonder how we’re going to get there someday?”

Full disclosure: The writer of this article served as TVIW’s volunteer Facebook/Twitter reporter.



Bart Leahy is a freelance technical writer living in Orlando, Florida. Leahy's diverse career has included work for The Walt Disney Company, NASA, the Department of Defense, Nissan, a number of commercial space companies, small businesses, nonprofits, as well as the Science Cheerleaders.

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