What if we had the ability to chase down interstellar objects passing through our Solar System, like Oumuamua or Comet Borisov? Such a spacecraft would need to be ready to go at a moment’s notice, with the capacity to increase speed and change direction quickly.

That’s the idea behind a new mission concept called the Extrasolar Object Interceptor and Sample Return spacecraft. It has received exploratory funding from NASA through its Innovative Advanced Concepts (NIAC) program.

“Bringing back samples from these objects could fundamentally change our view of the universe and our place in it,” says Christopher Morrison, an engineer from the Ultra Safe Nuclear Corporation-Tech (USNC-Tech) who submitted the proposal to NIAC.            

The concept Morrison and his team propose is a radioisotope-electric-propulsion spacecraft that relies on Chargeable Atomic Battery (CAB) technology, a power system that USNC has been developing for commercial use. The batteries are compact and possess one million times the energy density of state-of-the-art chemical batteries — as well as fossil fuels.

“Radioisotopes have about the same amount of total energy stored in each atom,” Morrison explained. “How quickly they release that energy depends on the half-life. Pu-238 has a half-life of 88 years, great for long missions to the outer solar system. The CAB batteries we are developing at USNC-Tech have shorter half-lives and possess a higher power density. In the NIAC, we are using a radioisotope with a five-year half-life and a power density over 30 times that of Plutonium-238 (Pu-238).”

Artist’s impression of NASA’s New Horizons spacecraft encountering a Pluto-like object in the distant Kuiper Belt. Credits: NASA/JHUAPL/SwRI/Alex Parker

Pu-238 is NASA’s usual nuclear power of choice for its spacecraft. It has been used for more than two-dozen U.S. very successful space missions — such as New Horizons, and the Curiosity and Perseverance Mars rovers – for their radioisotope power systems (RPS).

Pu-238, however faces some challenges. Only a limited amount of Pu-238 can be produced (a mere 14 ounces (400 grams) each year right now with a path toward 50 ounces (1500 g) over the next few years). This is just barely enough to meet
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