Catching Up to the Ship Passing in the Night
What is Oumuamua?
The cigar-shaped, interstellar object passed through our solar system in 2017, but it was gone nearly as quickly as it arrived—making it one of, if not the, biggest space mysteries of recent years.
“I don’t know what Oumuamua is, but I want to find out,” said Jim Bickford, group leader and distinguished member of Draper’s technical staff. “And the only way I can see doing that in my lifetime is to build a spacecraft on an order of magnitude faster than anything before to go find Oumuamua and catch it.”
And that’s exactly what he is doing.
Bickford is leading the Thin Film Isotope Nuclear Engine Rocket (TFINER) project to develop a system for propelling a craft through space faster and farther than ever before. The project was selected for a 2024 NASA Innovative Advanced Concepts award, which is designed to nurture “visionary ideas that could transform future NASA missions with critical breakthroughs.”
Faster than a speeding bullet
TFINER is based on the concept of “thrust sheets,” which were originally proposed by Wolfgang Moeckel in the 1970s. Thrust sheets are thin films coated with radioactive isotopes that leverage nuclear decay to push items through space.
As radioactive isotopes decay, they emit “alpha” particles, some of which can travel as fast as 5 percent of the speed of light.
“This is tremendously fast compared to a conventional chemical rocket and allows us to push payloads at a velocity of almost 100 kilometers a second,” said Bickford, adding that a conventional rocket would need to have a mass greater than the global human population to operate that fast.
Layering different isotopes can create decay chains that can drive a ship faster and farther than ever before, and the TFINER project is working to determine the right mix of radioactive isotopes to fuel the thrust sheets for extended space travel.
Thick, but not too thick
The other key component to TFINER is optimizing the size of the thrust sheets. To create propulsion, thrust sheets use various substrate materials to fine-tune the direction the decaying alpha particles go. Essentially, the substrates create a wall that the alpha particles push against.
Without these substrates, the isotopes would decay in all directions, and the ship would essentially remain stationary in space.
This means that the substrates must be thick and strong enough to hold up against the alpha particles but not add too much mass that will slow the craft’s speed. Bickford’s current estimate puts the substrate sheets around 35 microns – about as thick as the skin of an onion.
With sheets that thin, the TFINER system results in an incredibly small craft – small enough to fit in the back of a pickup truck, making it relatively easy to launch into space.
Catching oumuamua
Using current space technology, a conventional spacecraft would never be able to reach Oumuamua. TFINER enables a spacecraft to get there in not much more than a decade, allowing Bickford and others to better understand the strange object.
By opening the door to faster, farther space travel, TFINER gives researchers more opportunities to understand our solar system, galaxy and more. The technology can be applied to a range of other missions. TFINER is an ideal option for getting sensors to something called the solar gravitational focal line allowing researchers to directly see and image exoplanets orbiting other solar systems.
And Bickford may finally be able to answer his questions about Oumuamua.
