The next giant leap in space exploration could start with a small spin around the lab. A new propulsion system for shrunk-down satellites called CubeSats just passed a key lab test, and could be headed to space in the near future.
CubeSats, cheap, simple satellites built from off-the-shelf parts, promise a revolution in space exploration – but only if only we can steer them. Because they are so simple to build, they could open up space exploration to students and countries that lack their own space programmes, says Paulo Lozano at the Massachusetts Institute of Technology.
“We want to offer space access to people who don’t currently have space access,” Lozano told a meeting of science writers in Cambridge, Massachusetts, on Sunday.
About 10 of the 1-kilogram satellites can hitch a ride into space with a larger payload. Once they’re there, they can do serious science, from climate modelling to exoplanet hunting.
But they are also stuck in that orbit for their entire working lives. Not only does this limit their usefulness, but CubeSats can become dangerous space junk.
“If little satellites had the capability to move, we could do a lot of things that currently we cannot,” Lozano says.
So Lozano and his colleagues are designing a miniature propulsion system – small enough to fit in your pocket – that can steer CubeSats around low-Earth orbit – or even out of the solar system altogether.
Instead of chemical fuel, which is heavy and inefficient, they use an ionic liquid, made entirely of positively or negatively charged ions.
Because the material is liquid at room temperature, it is safer and simpler to take it into space than a plasma or gas. Applying an electric field can send these ions streaming away from the satellite at high speeds, producing a force in the opposite direction.
The theory was sound, but a few questions kept Lozano up at night. Would the ions left behind corrode the spacecraft? Would the spacecraft itself remain neutrally charged, or would the positive ions left behind pull the negative ions back in, cancelling out the thrust? And would the thrust be large enough to be useful?
This August, Lozano and his students tested the complete system, CubeSat and all. They put it in a vacuum chamber and magnetically levitated it to mimic the conditions in space, and placed the thrusters on opposite sides of the CubeSat to push it in a circle, rather than having it fly around the lab. One thruster emitted positive ions and the other negative ones, keeping the CubeSat neutrally charged.
After 20 minutes of continuous firing, the CubeSat spun at about 2 rotations per minute. Lozano says this would be enough to take a CubeSat from an altitude of 400 kilometres up to 800 kilometres, or to de-orbit it at the end of its life.
“It produces the force it should be producing given the amount it was emitting,” Lozano told New Scientist. “We’re quite happy.”
Next, the team fired the thrusters continuously for 140 hours, using up all the fuel without corroding the spacecraft.
“This is one of the other show stoppers we had at the beginning: will we be able to deplete all the ions from this ionic liquid?” Lozano says. “But we were able to get every single ion out. The tank was completely dry. This is the most exciting test we have run so far.”
How long until the satellites are ready for flight? The team has given three of their propulsion systems to the NASA Glenn Research Center in Ohio, where they are running more tests. “It’s up to them if they want to fly them,” Lozano says. “I hope maybe this year or next year – we are extremely close.”