Graphic representation of the Proxima Centauri Swarm: A Coherent Picospacecraft Flying Across Interstellar Distances Thomas Eubanks
Tiny gram-scale interstellar probes propelled by laser light are likely to be the only technology capable of reaching another star this century. We predict that by mid-century there will be a laser beam powerful enough (~100 GW) to accelerate the relativistic speed by a few grams, laser sails strong enough to survive launch, and terrestrial light buckets (~1 sq km) large enough , to catch our optical signals. Then our proposed representative mission, sometime in the third quarter of this century, is to fly past our nearest neighbor, the potentially habitable world Proxima b, with a large autonomous swarm of 1,000 tiny probes.
Given the extreme limitations on launch mass (grams), on-board power (milliwatts) and communication aperture (centimeters to meters), our team has determined in their work over the past 3 years that only a large swarm of many probes acting in unison can create an optical the signal is strong enough to travel the vast distance back to Earth. The 8-year round-trip delay precludes any practical control from Earth, so the swarm must have an extraordinary degree of autonomy, for example to prioritize data returned to Earth. Thus, the reader will see that coordinating individuals into an effective whole is a dominant task for our flagship mission to Proxima Centauri b. Coordination, in turn, relies on creating a mesh network over low-power optical communication channels and synchronizing the probes’ on-board clocks with Earth and each other to support precise location, navigation and timing (PNT).
Our representative mission begins with a long series of probes launched one at a time to ~0.2c. Once triggered, the drive laser is used to signal and synchronize the clock, providing a continuous time signal like a metronome. The initial gain is modulated so that the tail of the string catches up with the head (“time to target”). Using the drag created by the interstellar medium (“target velocity”) during the 20-year cruise holds the group together as it gathers. An initial string of 100 to 1000 AUs is dynamically combined over time into a lens-shaped grid #100,000 km across, large enough to account for ephemeris errors in Proxima, ensuring that at least some probes pass close to the target.
A swarm whose members are in a known spatial position relative to each other, with modern micro-miniature clocks to maintain synchronicity, can use its entire population to communicate with Earth by periodically generating a single short but extremely bright simultaneous laser pulse from all of them. Operational coherence means that each probe sends the same data, but adjusts the timing of the emission according to its relative position, so that all pulses arrive simultaneously at the receiving arrays on Earth. This effectively multiplies the power from any probe by the number of N probes in the swarm, providing an order of magnitude higher data throughput.
The swarm will withstand significant attrition along the way, reducing the risk of “putting all your eggs in one basket” and allowing close observation of Proxima b from multiple vantage points. Fortunately, we don’t have to wait until mid-century to make practical progress—we can research and test swarming techniques now in a simulated environment, which is what we propose to do in this paper. We expect our innovations to have a profound impact on space exploration, complementing existing methods and enabling entirely new types of missions, such as swarms of picospacecraft spanning the entire cylindric space or instruments of the entire planetary magnetosphere. Well before mid-century, we envision a series of such missions, beginning in near-Earth or lunar orbit, but eventually extending deeper into the solar system. For example, such a swarm could probe the rapidly receding interstellar object 1I/’Oumuamua or the Sun’s gravitational lens. Both would be precursors to the eventual interstellar mission, but would also be scientifically valuable in their own right.
— Thomas Eubanks Space Initiatives, Inc.:
2024 NIAC Phase I Selection, NASA
Astrobiology, Interstellar,