Without propellant, spacecraft would be little more than space junk. Or would it?
An ingenious system for satellites that does not rely on propellant actually exists now. Conceived by researchers at the Universidad Carlos III de Madrid (UC3M) and the Universidad Politécnica de Madrid, it replaces fuel with electric power and on-board thrust. The system can actually use available power found in space to produce thrust that sends a satellite higher up, or the opposite — passively generate power as the satellite approaches Earth.
Behind this sci-fi advancement is something called a low-work-function tether, which is a long conductor (aluminum in this case) that is rolled up until being deployed once the satellite is in orbit. Sunlight and heat will activate the advanced electron emission properties it has been upgraded with. Here is where it gets mind-blowing. It generates energy from solar radiation as well as our planet’s ionospheric plasma and geomagnetic field, with the laws of electromagnetism allowing it to propel a spacecraft upward or downward. Enter Lorentz drag, an electrodynamic effect that merges electric and magnetic forces. Just imagine a satellite in this video.
“This is a disruptive technology because it allows one to transform orbital energy into electrical energy and vice versa without using any type of consumable,” said researcher Gonzalo Sánchez Arriaga of the Bioengineering and Aerospace Engineering Department at UC3M, in an article posted on the university's website.
The anti-propellant of the future could actually be huge for the ISS. Keeping an airborne space station afloat and in orbit means burning massive amounts of propellant to fight off atmospheric drag. If it were powered by the new system, the tether would convert any thrust caused by gravity into usable electricity as the space station approached Earth.
“With a low- work function tether and the energy provided by the solar panel of the ISS, the atmospheric drag could be compensated without the use of propellant,” Sánchez Arriaga said.
Even though the team earned two patents — “System for generating electrical power in orbit by means of floating conductor cables” and “System for in-orbit propulsion via floating conductor cables” — space tethers have been around for a while and have taken off with 20 space missions. Sánchez Arriaga and colleagues have leveled up this technology by simplifying it so a lightweight duo of aluminum tethers to power a spacecraft, ditching the electron emitter and instead amping the photoelectric effect when sunlight hits the tape.
The system will be just as useful for a deorbiting satellite as it is for one in orbit. By gradually sending a spacecraft downward until it reenters the atmosphere and self-immolates, it could eliminate space junk. Sánchez Arriaga, fellow patent author Claudio Bombardelli, and colleagues need to start prototyping and manufacturing the system, boosted by a government grant. Their technology could prove extremely useful when the ISS goes out of commission.
Now if only cars could generate their own fuel like that.