NASA Selects Bold Proposal To 'Swarm' Proxima Centauri With Tiny Probes

In order to reach places like Alpha Centauri this century, we'll need to utilize gram-scale spacecraft that rely on directed-energy propulsion. To that end, NASA has selected the Swarming Proxima Centauri project for Phase I development as part of this year's NASA Innovative Advanced Concepts (NIAC) program. According to Universe Today, Swarming Proxima Centauri is 'a collaborative effort between Space Initiatives Inc. and the Initiative for Interstellar Studies (i4is) led by Space Initiative's chief scientist Marshall Eubanks.' From the report: According to Eubanks, traveling through interstellar space is a question of distance, energy, and speed. At a distance of 4.25 light-years (40 trillion km; 25 trillion mi) from the Solar System, even Proxima Centauri is unfathomably far away. To put it in perspective, the record for the farthest distance ever traveled by a spacecraft goes to the Voyager 1 space probe, which is currently more than 24 billion km (15 billion mi) from Earth. Using conventional methods, the probe accomplished a maximum speed of 61,500 km/h (38,215 mph) and has been traveling for more than 46 years straight.

In short, traveling at anything less than relativistic speed (a fraction of the speed of light) will make interstellar transits incredibly long and entirely impractical. Given the energy requirements this calls for, anything other than small spacecraft with a maximum mass of a few grams is feasible. In contrast, concepts like Breakthrough Starshot and the Proxima Swarm consist of 'inverting the rocket' -- i.e., instead of throwing stuff out, stuff is thrown at the spacecraft. Instead of heavy propellant, which constitutes the majority of conventional rockets, the energy source for a lightsail is photons (which have no mass and move at the speed of light). But as Eubanks indicated, this does not overcome the issue of energy, making it even more important that the spacecraft be as small as possible. 'Bouncing photons off of a laser sail thus solves the speed-of-stuff problem,' he said. 'But the trouble is, there is not much momentum in a photon, so we need a lot of them. And given the power we are likely to have available, even a couple of decades from now, the thrust will be weak, so the mass of the probes needs to be very small -- grams, not tons.'

Their proposal calls for a 100-gigawatt (GW) laser beamer boosting thousands of gram-scale space probes with laser sails to relativistic speed (~10-20% of light). They also proposed a series of terrestrial light buckets measuring a square kilometer (0.386 mi2) in diameter to catch the light signals from the probes once they are well on their way to reaching Proxima Centauri (and communications become more difficult). By their estimates, this mission concept could be ready for development around midcentury and could reach Proxima Centauri and its Earth-like exoplanet (Proxima b) by the third quarter of this century (2075 or after). Eubanks and his colleagues hope that the development of a coherent swarm of robotic probes will have applications closer to home. Swarm robotics is a hot field of research today and is being investigated as a possible means of exploring Europa's interior ocean, digging underground cities on Mars, assembling large structures in space, and providing extreme weather tracking from Earth's orbit. Beyond space exploration and Earth observation, swarm robotics also has applications in medicine, additive manufacturing, environmental studies, global positioning and navigation, search and rescue, and more.

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