LA CAÑADA FLINTRIDGE >> Inspired by the “Hitchhiker’s Guide to the Galaxy,” a Jet Propulsion Laboratory expert devised a potential way to catch a ride through space using a strong tether and perhaps a hefty diamond harpoon.
Unlike the classic sci-fi novel’s protagonist, JPL’s Masahiro Ono, principal investigator of Comet Hitchhiker, said his goal isn’t to visit extraterrestrial civilizations or to dine at the Restaurant at the End of the Universe.
His team’s concept is an attempt to answer some of NASA’s quandaries: fuel-less landing and orbit insertion, non-gravitational slingshotting around small bodies and deep space energy production.
“New Horizons was like an express train that passes a station,” Ono said, referring to a NASA spacecraft that flew by Pluto in July. “It doesn’t make a stop at a station. When it passes a station, it just takes a glimpse.
“What this hitchhiker does is like someone in a local train. It stops at the station, he walks out of the train, walks around, gets food and talks to a lot of people, and then gets back on the train to go to the next target.”
The eight-member Comet Hitchhiker team hopes to one day harvest kinetic energy from small bodies to enable fast and low-cost deep space exploration. The theoretical method could enable NASA to land on comets and asteroids, which have low gravitational pull.
The NASA Innovative Advanced Concepts Program provided $100,000 for Ono’s 9-month, Phase I study.
“The purpose of NIAC is early studies of visionary concepts,” said Jay Falker, former NIAC program executive, in a video. “They have to be innovative yet credible, and so we are really looking for revolutionary ideas.”
Ono presented the results of his concept study Tuesday at the American Institute of Aeronautics and Astronautics SPACE 2015 conference in Pasadena.
How this idea solves a space exploration puzzle
The New Horizons spacecraft flew by Pluto at a speed akin to hopping from Los Angeles to San Francisco in 45 seconds, Ono said.
“To stop New Horizons at Pluto, you would need 30 metric tons of propellent fuel,” he said. “Launching something that big is not impossible, but it is very unrealistic.”
Comets and asteroids are similar to old, preserved villages that could unfold details about the origin and evolution of the solar system some 4.6 billion years ago, Ono said. Flying by celestial objects answers some questions, but a more leisurely probe would be ideal.
How the technology works
The solar system is like a busy intersection with more than 670,000 asteroids and 3,800 comets, Ono said. Astronomers estimate that more than 100,000 Kuiper belt objects exist, so “wouldn’t it be a good idea to hitch a ride on one of those vehicles instead of driving on your own?” Ono wrote in his study.
When a spacecraft is close to a target, it would cast a harpoon attached to an extendable tether. Once it snags an asteroid or comet, the vehicle will let out rope and apply a brake system that generates energy as the machine accelerates to meet the galactic object’s velocity.
Once the small body and spacecraft are traveling at the same speed, the spacecraft will reel in the tether and gently land.
When NASA is done with scientific observations, the spacecraft could journey on by harpooning another celestial body, extending its tether, pulling on the tether and then detaching itself. The pulling portion expends energy that was collected and stored in the initial hitchhike maneuver.
“You visit multiple small bodies in the solar system by using a harpoon and tether like Spider-Man, who shoots his string to move between buildings,” Ono said, adding that five to 10 stops or slings could be made in the main asteroid belt or the Kuiper Belt.
Because this reusable tether system generates its own energy source, it could be an alternative to using propellent to enter orbit and land spacecraft.
More technical details
Ono and his team determined a velocity change of about 1 mile per second is possible using Zylon or Kevlar. But to catch a comet or asteroid they would need faster, stronger materials than currently exist, the researchers reported.
A 6.2-mile-per-second velocity change would require a diamond harpoon and advanced technologies such as a carbon nanotube tether, which doesn’t yet exist.
“I’m pretty sure the diamond would be much bigger than the diamond on my wife’s ring finger or on any princesses’ finger,” Ono said with a laugh.
The tether would need to be some 62 to 620 miles long for the hitchhiking maneuver to work. It needs to be able to absorb jerks and somehow not get damaged when small meteorites hit it.
Next steps
Ono is seeking funding for Phase II of the Comet Hitchhiker study, which will do more high-fidelity simulations and attempt to cast a mini-harpoon at a comet- or asteroid-like target.
