NASA engineers say they have come up with an easier way of exploring comets and asteroids in our Solar System: harpooning fast-moving space rocks. The idea is to make a probe — called Comet Hitchhiker — that would "catch rides" on asteroids by spearing them with tethers. Once the vehicle finishes a ride with one asteroid, it will disconnect and hitch a ride with another. The idea was dreamed up by NASA's Jet Propulsion Laboratory as a way of using less fuel to land spacecraft on these space rocks.
Right now, landing objects on asteroids is tough since these rocks move at a speed of about 15 miles per second. So a spacecraft has to be much faster than an asteroid to catch up. Then if it does reach the asteroid, the vehicle has to slow down to match the object's speed. Asteroids and comets are pretty small too, with low gravitational pulls, so the spacecraft has to do most of the work to land. This braking process requires a lot of propellant.
Think of it like going fishing
The hitchhiking idea would get rid of the need for fuel during the landing process, JPL says. Think of it like going fishing. When the spacecraft meets up with an asteroid, it will cast out its line; harpoons will shoot out tethers to connect the spacecraft to the rock. The vehicle will then extend the tethers a bit so there isn't too much tension on the rope. (Fishermen also do this when they hook big prizes, so their line doesn't snap right away from too much force.) Eventually the spacecraft will match the velocity of the asteroid. When it does, the probe will reel in its tethers very slowly in order to land.
Masahiro Ono, the principal investigator based at JPL, says the spacecraft's tethers will have to be made of super strong material. Zylon and Kevlar could work, but the engineers are also considering more advanced technologies like a carbon nanotube tether with a diamond harpoon — incredibly strong materials. The tethers would also need to be between 62 and 620 miles long for the maneuver to work.
Overall, the idea is to send the Comet Hitchhiker to as many small bodies as possible throughout our cosmic neighborhood. The spacecraft could then gather samples from these rocks to determine what they’re made of. So far the project is only in Phase 1 through the NASA Innovative Advanced Concepts (NIAC) Program. But if it does become a reality, hopeful the vehicle will receive more hospitality than other hitchhiking robots have gotten in the past.