Solar Sail Doubling as an Atompunk Design: TFINER's Innovation

In a groundbreaking proposal, James A. Bickford has introduced TFINER (Thin-Film Nuclear Engine Rocket), a novel space propulsion method that resembles a solar sail. The design calls for a 400-meter-long cable for the payload, allowing for some degree of thrust-vectoring but not making it highly maneuverable.

The heart of TFINER lies in its "sail," which hosts a thin film of nuclear material. The decay products of this material provide the reaction mass, propelling the spacecraft forward. The specific impulse (ISP) on TFINER is an impressive 1.81 million seconds, making it highly efficient.

TFINER employs alpha particles from Thorium-228 or Radium-228 as its propellant. These alpha particles travel at about 5% the speed of light. Notably, most of these emissions from the initial isotope and its decay products aim roughly normal to the surface, allowing them to escape effectively.

The proposal for TFINER references the Sun's gravitational lens effect. Unlike traditional lenses, the focus of the Sun's gravitational lens effect is a line, not a point, for TFINER. This potential focus could offer unique opportunities for spacecraft navigation and trajectory planning.

The sail of TFINER is made of a 9.5 um thin film on a 35 um beryllium back-plane, designed to absorb alpha emissions going the wrong way around. The current status of the TFINER project is not explicitly detailed in the provided search results, but it has advanced to a Phase II study, with NASA taking the lead.

In the Phase I study for NASA's Innovative Advanced Concepts office (NIAC), TFINER used alpha particles from Thorium-228 or Radium-228. Future work on TFINER includes the idea of combining it with a solar sail for maximum possible delta-V from an Oberth-effect sundive.

TFINER has been summarised on Centauri Dreams by Paul Gilster, highlighting its potential as a game-changer in space exploration. With the Phase II study involving some actual hardware, specifically a 1 square centimeter demonstrator, the future of TFINER is looking promising. The project, however, does not seem to have a clear leader as of yet.

Intriguingly, TFINER also proposes using extra-solar comets like Oumuamua as potential flyby targets, adding another layer of excitement to this innovative space propulsion method. As TFINER continues to evolve, it could revolutionise the way we navigate and propel spacecraft, opening up new possibilities for deep-space exploration.