This propulsion technology could significantly hasten the advent of interstellar travel.
Proxima Centauri (PC), the nearest star to Earth, is approximately 8000 times farther away than Pluto. To collect valuable data, a probe must travel to PC at speeds much higher than those currently achievable. A proton beam, made resistant to diffraction by intricate algorithms, might be the key solution.
Earlier this year, the iconic Voyager 1 probe made headlines when it lost contact, then remarkably regained it thanks to meticulous, long-distance repairs. Voyager 1 is about 15.2 billion miles from Earth, which is more than five times the distance from Earth to Neptune, highlighting its extraordinary distance.
Yet, Proxima Centauri sits about 1600 times farther away from us than Voyager 1. This star system is considered a prime candidate for human habitation beyond Earth, spurring interest for decades. However, at 25 trillion miles away, it's far beyond our current reach, especially given Voyager took 50 years to reach its current distance from Earth.
To explore PC and its exoplanets, we need a revolutionary approach to spacecraft propulsion. The small size of a probe, like the 1,500-pound Voyager (compared to the Space Shuttle's 4.5 million pounds at launch), makes it apt for trialing interstellar propulsion strategies.
In 2018, NASA's Innovative Advanced Concepts (NIAC) group issued a report by scientist Chris Limbach on a proton beam propulsion concept named PROCSIMA: Photon-paRticle Optically Coupled Soliton Interstellar Mission Accelerator.
This beam concept might sound radical compared to the nuclear battery powering Voyager 1. However, in the 70s, even that technology seemed groundbreaking—and it proved successful. Although the beam is still theoretical, it offers real-world benefits. Limbach noted that beam propulsion systems derive their primary capability from separating power and propulsion from the spacecraft, freeing them from traditional rocket limitations.
Essentially, propulsion takes place on Earth, simplifying calculations for the spacecraft itself. You can liken the probe to a baseball; the propulsion system (like swinging a bat) remains grounded on Earth, unlike most systems where the baseball (probe) must generate its own power.
Limbach acknowledges that while these ideas aren’t new, beam diffraction has historically prevented practical use, as beams significantly lose efficacy over great distances. His notable contribution is a method to maintain beam focus over trillions of miles. Despite the crowded portrayal of space in fiction, our path to Proxima Centauri is actually quite clear.
Limbach's paper reviews existing knowledge and introduces new ideas to stimulate further discussion on self-maintaining, non-diffracting beams. Although complex, housing this complexity on Earth means repairs aren’t unexpectedly miraculous.
"These studies did not uncover any critical barriers," Limbach concludes—just promising ideas in need of further exploration. As space travel increasingly captures our attention, these concepts may gain renewed urgency.
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