Comment by fsloth

ELY 5:

No, this is actual Newtonian physics. Rockets function based on Newton's third law: every reaction creates an equal and opposite reaction. We sit on wheeled office chairs, I push you- we both move, to opposite directions.

Rockets aren't fueled by office chairs, though, but by gases. They push the gas molecules into a particular direction and themselves are pushed into another.

So, to move in space by pushing stuff, you need two things: a) mass to push away b) some power to do the pushing

(This ignores several categories of other forms of force generation on space craft like solar sails).

Chemical fuel rockets happen to strike two flys on one go - the mass they carry also generate the energy for the push, so that's only a matter of plumbing and hydrodynamics to get them going.

The problem with this approach, though, is that once you run out of fuel, you run out of fuel. No more chairs, no more acceleration. Refueling in space is really expensive, if you need to bring up the propellant from a deep gravity well like earths surface to the orbit (https://xkcd.com/681/).

There is no necessity the propellant (i.e the 'chairs') needs to generate the energy for pushing itself away. You can you Some Other Physics to push the propellant away from the vehicle. It works just as fine.

This system collects the fuel from sparse gas surrounding it, and expels it using an electric thruster, which probably get's it's energy from solar panels.

Potentially, like some other poster noted, you could design a spacecraft with this that once it reaches planetary orbit, it can hop from planet to planet and refuel itself indefinetly (just as long as the planets have an atmosphere).

So it's Way Cool, and this has been hypothesized in science fiction for decades, so it's also Genuine Scifi Space Tech :)