Presenting paper at American Nuclear Society meeting in D.C. Nov. 10
Carolyn Krause
| Special to The Oak Ridger
James Webb Space Telescope reveals clues into moon formation
NASA’s James Webb Space Telescope is giving scientists an unprecedented glimpse at how moons might form around distant exoplanets.
- Engineers are developing a concept for interstellar travel using a swarm of 1,000 ultra-light “laser sails.”
- The mission aims to send these sails to Proxima b, an exoplanet 4.25 light-years away, using a powerful laser system on the moon.
- These tiny spacecraft would travel at 20% of the speed of light, reaching their destination within a human lifetime.
- The project, which received a NASA Phase I study grant, seeks to send back high-resolution images of the exoplanet.
Imagine a large, round, flat, thin disk four meters (13 feet) in diameter that weighs just four grams (0.14 ounce, about the same weight as a small coin) and that is big enough to almost cover the wall of a small bedroom.
Imagine that 1,000 of these so-called interstellar laser sails will each be pushed into outer space at different times over several months by laser beams from a yet-to-be-built, 100-billion-watt launch laser system located on the far side of Earth’s moon. It would consist of a multitude of phased lasers that would combine to be by far the most powerful launch laser in the world anytime this century
The powerful laser system would accelerate a “swarm” of laser sails – say, 1,000 – to 20% of the speed of light, enabling them individually to escape from the solar system at different times and each complete a record long-distance flight at the same time.
Their destination: Proxima b, one of the two known exoplanets revolving around Proxima Centauri, the closest star to our sun.
Their purpose: To arrive at the same time – within a human lifetime (maybe 20 years after launch in 2075) – so they can send back the highest-resolution images of the exoplanet to Earth, where the data will be received just over four years later (maybe by 2099).
The exoplanet Proxima b has roughly Earth’s mass and revolves in Proxima Centauri’s “Goldilocks zone,” said Robert G. Kennedy III, noting that NASA scientists are interested in knowing if this b planet shows signs of water and even life. Kennedy spoke about this envisioned mission recently to the League of Women Voters of Oak Ridge.
A modern spacecraft, he added, would take almost 75,000 years to reach Proxima Centauri, a red dwarf star that is 4.25 light-years away, or over 25 trillion miles, from Earth. (See https://youtu.be/XXW_keR5OIM.)
The swarm of these smallest of spacecrafts should be able to fly toward the star and send data as light pulses in synchrony to extremely large telescopes on Earth.
This information was provided by Kennedy, a systems engineer in Oak Ridge who spoke on “This Is What It Looks Like: Interstellar Flight This Century” at the “Lunch with the League” in September. He is the co-founder of two community-scale, grassroots, open-source nonprofit organizations for space in Oak Ridge: the Tennessee Valley Stellar Corp. (www.stellarcorp.tv) and the Institute for Interstellar Studies–U.S. (www.i4is.us).
Kennedy is a co-investigator on a team led by Thomas Marshall Eubanks at Space Initiatives, Inc. (SII). The team’s mission was selected for a 2024 Phase I study by NASA’s Innovative Advanced Concepts (NIAC) program. It failed to make the list for a Phase II study this year, but Eubanks plans to try again in 2026, according to an article in an IEEE journal.
Kennedy and other engineers with these nonprofit space organizations have been promoting the communications concept to NASA. He gave a talk on their work in September 2024 at the NIAC Symposium in Pasadena, California.The nearly full-scale mockup of an interstellar laser sail that he built with the assistance of Denise Johnson of Oak Ridge, who makes wedding dresses, was displayed at this symposium and at the recent League meeting.
Kennedy said the flight version of the laser sail must weigh three grams, leaving just one gram for the entire scientific payload, which will consist of a large array of flat ringlike optical transceivers. He stated that the black side of the mockup of the laser sail he showed will likely be made of “aerographene,” q foamy layer of carbon atoms a few hundred nanometers thick, atop a metallic dielectric to keep the temperature during launch below 600 kelvins (620 degrees Fahrenheit) so no part of a laser sail will melt.
The opposite side of the sail is covered with gold foil or some other reflective surface that would face the launch laser system. Its beams will propel the laser sails, accelerating them one at a time at 10,000 gravities, about the same as an artillery shell, but for 10 minutes, so it attains 20% of the speed of light.
After the fleet is launched, Kennedy said, the laser system will stay on at lower power so it can communicate with the fleet like a metronome during the laser sails’ 20-year flight. The launch system can even illuminate the Proxima system four light years away with a little bit of extra light, like that from a full moon, to help the probes avoid dark obstacles. They call this invention “the interstellar flashlight.”
Kennedy said he believes it will take at least 50 years for the launch laser system and laser sails to be constructed. But it should be possible, he noted, since humankind “went from Sputnik to Neil Armstrong on the moon in 22 years.”
Each of 1,000 laser sails would start at different times but “at some point, during the journey, all 1,000 of them come together briefly,” Kennedy said. “The military calls that ‘time on target.’
“The ones in the tail going faster will pass the ones at the head flying slower. It’s like the cop chasing you on the freeway. He’s not going to zoom past you, because he wants to pull you over and give you a ticket. So, after he catches up to you, he’s got to match velocities with you.”
To enable the laser sails flying behind to catch up with the ones ahead, Kennedy and others invented a way to make each laser sail maintain its velocity by traveling “edge on” to prevent it from presenting its frontal area to hydrogen atoms and interstellar magnetic fields that will slow it down.
But to allow the laser sails behind to catch up with the ones ahead, the tiny spacecraft in front will slow down by turning from “edge on” to flying “face on” as they sail toward Proxima Centauri.
Kennedy said this scheme will ensure that all laser sails arrive at the same time in the vicinity of the exoplanet – what he and his colleagues call “velocity on target” – and send back a single coordinated intelligible signal to Earth. The technologies enabling this achievement will be a tiny atomic clock in each probe and little infrared lasers on the side so fleet members can discover and talk to each other.
“It’s like the synchronous fireflies in the Smokies,” he added.
The original idea of pushing miniature spacecraft to near-relativistic velocities using visible light lasers was proposed in 2014 by Phil Lubin of the University of California at Santa Barbara. His concept was published in his paper that appeared in the spring 2016 issue of the Journal of the British Interplanetary Society.
Yuri Milner, a Russian-born billionaire who has lived in Israel and the United States, approached Lubin and high-profile (but now deceased) scientists like Stephen Hawking and Freeman Dyson about the Lubin concept. Breakthrough Starshot was announced with Milner as the facilitator and sponsor.
“He proposed launching a very lightweight spacecraft to a fraction of the speed of light to the star and getting data back within a human lifetime,” Kennedy said. “But he wanted to put on Earth a launch laser so powerful that the world’s militaries would never tolerate it. It needs to go on the far side of the Moon where it can’t see us from there or hit anything here. It took a long time to convince him that a swarm of tiny spacecrafts – the laser sails – was the way to go, but he came around to it.”
Milner hired Kennedy’s team to take on the systems engineering task of solving the communications problem – that is, to ensure that the launch laser system and the laser sails are all communicating with each other and can send up to 150 kilobits of data from space to Earth about four light-years away. They called this approach “operational coherence.”
It also includes ensuring that each four-gram spacecraft has sufficient onboard electricity to power its scientific payload. Kennedy allotted a third of a gram for a tiny atomic battery that for 30 years will generate 10 milliwatts of electrical power converted to one milliwatt of optical power, meaning that all 1,000 laser sails together would generate one optical watt in synchrony.
One concept for providing very low onboard power over a long lifetime for a four-gram spacecraft was developed by Kennedy and a colleague.
“My co-author and I are presenting a paper on Nov. 10 at the American Nuclear Society meeting in Washington, D.C., on strontium-90 beta voltaic power,” he said.
Strontium-90, a common radioactive isotope produced by nuclear fission that has a half-life of about 29 years, decays by emitting beta particles. They are high-energy electrons that can, by colliding with atoms in semiconductor material, trigger the flow of a direct current.