The Institute is about to launch its own five-year mission to design and build thrusters, which incorporate the magnets, to propel spacecraft and adjust their track.
The research programme is a joint initiative with the University of Auckland and the University of Canterbury, with funding from the Ministry of Business, Innovation and Employment (MBIE).
Institute Director Dr Nick Long says once in orbit, satellites need to change velocity, whether that is to adjust their orbit, re-orient themselves or stay in the right place.
“Most satellites need to adjust their orbits or orientations during their lifetimes, including at the end of lifetime to de-orbit or go to a ‘graveyard’ orbit. Some are launched into one orbit but then slowly propel themselves to a different orbit to carry out their function.
“With chemical propulsion systems, they burn fuel every time they accelerate. But these new ion thrusters will be solar-powered, allowing the propulsion energy to be captured while in flight.
“And by using superconductors, the thrusters will be more powerful for their weight.
“To do science fiction-like stuff in space, we have to use the most high-performance materials available. For creating magnetic fields, this is superconductors.
“Our job is to take the fiction out of the science fiction.”
Superconductors transport huge electric currents with close to no energy loss, and allow incredibly high-current densities to be achieved.
Their development is one strand of the Robinson Institute’s work to meld innovative engineering with applied physics to build advanced technologies for global benefit.
Dr Long says the project will apply a rare-earth barium copper oxide wire to form the magnet in an applied field magneto-plasma dynamic thruster.
“This is a type of ‘electric propulsion’ for satellites or other spacecraft. Electric propulsion uses a combination of electric and magnetic fields to create a force on ions which propels the ions from the spacecraft at very high velocities.
“The advantage is that the energy can be harnessed from solar panels and then transferred to the ions, unlike chemical propulsion where you take an explosive fuel with you and burn it to release energy.”
Getting the efficiency of the thruster just right by optimising the combination of electric and magnetic fields is the key to the programme’s success, Dr Long says.
“The experimental testing of the thruster is very difficult. The amount of force created is very small, and this type of engine is only useful for moving objects around which are already in space, as it doesn’t produce the magnitude of forces which can lift a rocket into orbit.
“We also have to work out how to keep the superconductor magnet cold while in space without this using too much energy. We already have some ideas on how to do this efficiently–one key step is to induce the currents in the magnet inductively, which means the magnet is not physically coupled to a warm power supply.”
After testing the system in the lab, a small version will be built for launch so the thruster can be trialled on a small satellite. The intention is to launch with New Zealand company Rocket Lab within five years.
The team faces its biggest challenges with attempting to minimise the system’s power requirements while maximising the speed with which ions are emitted from the thruster.
It is also crucial they can get accurate test results of the amount of thrust created, Dr Long says.
“We face other challenges too. We have to make the system robust and reliable so it can be launched and operate remotely, something never done before with a superconductor system.
“Also the strong magnetic field of the thruster may affect other parts of the satellite system – the guidance, navigation and control (GNC) systems that all satellites and spacecraft must have. A strong magnetic field on a satellite will produce forces when interacting with the Earth’s magnetic field, so this has to be accounted for by the GNC system.”
The researchers want to know if a proven superconductor propulsion system on a small scale can work at a larger one.
“ It would also be very useful for interplanetary travel. It is generally too inefficient to use chemical propulsion for example to go to Mars, stop there (stopping requires a lot of energy), and then come back. But electric propulsion means much of this energy can come from the Sun–you don’t have to lift all this energy in the form of fuel off the Earth’s surface.
“There are also many other potential uses for superconductors in space, including creating magnetic brakes to help slow a spacecraft down as it enters a planet’s atmosphere, or magnetic heat shields to deflect heat away from a spacecraft and enable reusable vehicles for re-entry to Earth’s atmosphere.
“We could also make magnetic radiation shields. At the moment, if you went to Mars you’d be fried by radiation, so you either need a magnetic shield or thick layers of steel to absorb the radiation.”