Researchers at NASA’s Jet Propulsion Laboratory (JPL) have devised a new way to get into orbit and land on Solar System’s small bodies.
Comet Hitchhiker is a concept for orbiting and landing on comets and asteroids. The idea involves using a carbon nanotube tether to hitchhike on to a comet as it flies by. Image credit: NASA / JPL-Caltech / Cornelius Dammrich.
“Hitchhiking a celestial body is not as simple as sticking out your thumb, because it flies at an astronomical speed and it won’t stop to pick you up. Instead of a thumb, our idea is to use a harpoon and a tether,” said Dr Masahiro Ono of JPL, who had ‘Hitchhiker’s Guide to the Galaxy’ in mind when dreaming up the idea, dubbed Comet Hitchhiker.
A reusable tether system would replace the need for propellant for entering orbit and landing, so running out wouldn’t be an issue.
While closely flying by the target, a probe would first cast an extendable tether toward the asteroid or comet and attach itself using a harpoon attached to the tether.
Next, the probe would reel out the tether while applying a brake that harvests energy while the probe accelerates.
“This kind of hitchhiking could be used for multiple targets in the main asteroid belt or the Kuiper Belt, even five to ten in a single mission,” Dr Ono explained.
“In Comet Hitchhiker, accelerating and decelerating do not require propellant because the spacecraft is harvesting kinetic energy from the target.”
Comet Hitchhiker requires a tether made from a material that can withstand the enormous tension and heat generated by a rapid decrease in speed for getting into orbit and landing.
Comet Hitchhiker. Image credit: NASA / JPL-Caltech / Cornelius Dammrich.
Dr Ono and co-authors calculated that a velocity change of about 0.9 miles (1.5 km) per second is possible with some materials that already exist: zylon and kevlar.
“But the bigger the velocity change required for orbit insertion, the shorter the flight time needed to get from Earth to the target – so if you want to get to a comet or asteroid faster, you need even stronger materials. A 6.2 mile-per-second (10 km-per-second) velocity change is possible, but would require more advanced technologies such as a carbon nanotube tether and a diamond harpoon.”
The team also estimated that the tether would need to be about 62 to 620 miles long (100 to 1,000 km) for the hitchhiking maneuver to work. It would also need to be extendable, and capable of absorbing jerks on it, while avoiding being damaged or cut by small meteorites.
The results about the concept were presented September 1 at the American Institute of Aeronautics and Astronautics SPACE Conference in Pasadena, CA.
Dr Ono and his colleagues said that the next steps for studying their concept would be to do more high-fidelity simulations and try casting a mini-harpoon at a target that mimics the material found on a comet or asteroid.
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Masahiro Ono et al. 2015. The Hitchhiker’s Guide to the Solar System: A Tethered Orbit Insertion and Landing Concept for Small Body Exploration. American Institute of Aeronautics and Astronautics SPACE Conference, abstract: AIAA-2015-4567
