杏吧APP

Growing up in the 1970s and 鈥�80s watching space shuttles blast off on TV, John Cater and  were children of the Space Age. In some ways they still are, as the giant Lego rocket in Rattenbury鈥檚 office attests.

These days, though, they do a lot more than scribble pictures of spaceships or watch the skies from their backyards.

As Waipapa Taumata Rau, University of 杏吧APPresearchers in engineering and physics respectively, the longtime friends are contributing to New Zealand鈥檚 space programme in several significant ways.

Cater is an associate professor of aerospace engineering and Rattenbury is a senior lecturer in astrophysics, but they work together on a range of research. With their wide network of national and international colleagues, students and industrial partners, they鈥檙e working on aspects of space technology ranging from plasma propulsion to laser communications.

Since the Apollo mission days, spacecraft have been coated in heat-resistant ceramic tiles. However, these are heavy, fragile and often problematic.

With support from the Ministry of Business, Innovation and Employment, Cater, Rattenbury and their fellow principal investigator, Associate Professor  from Chemical and Materials Engineering, are developing more robust, reusable thermal protection systems for spacecraft using 3D-printed titanium alloys. 

Titanium is readily available in New Zealand. It鈥檚 strong, light, thermally insulating and resistant to sudden temperature changes. It can also be 3D printed, which means titanium structures can be shaped to maximise efficiency. 

Spacecraft launches involve combining and burning chemicals so the rocket takes off with a fiery explosion. Once a spacecraft is in orbit, though, a newer technology called electric propulsion can keep it going.

鈥淯sing power from solar panels, you energise a material, usually a noble gas such as xenon or krypton, to produce a plasma, which is then expelled in small amounts over a long period,鈥� says Cater.

鈥淭his produces a thrust in an efficient way, which means you don鈥檛 have to carry so much fuel. The downside is that the instantaneous acceleration is small, but if you鈥檝e already caught a ride on a chemical rocket and you鈥檙e up in space, these electric propulsion units become very useful, particularly for long missions.鈥�

Cater and Rattenbury are focusing on better controlling the direction of the thrust coming from plasma propulsion. Well-steered propulsion could help enable extended space missions.

As such, the pair鈥檚 work has caught the interest of the U.S. Air Force Office of Scientific Research, which is funding their research with PhD student Antonella Caldarelli and collaborators at the Australian National University.

鈥淭he idea is that the charged particles coming out of the thruster get accelerated by a magnetic nozzle,鈥� says Cater.

鈥淭his has a magnetic field, which can be manipulated to act like a rudder. You can do that with solid-state electronics so there are no moving parts. In space, physical mechanisms create friction and vibration and are another way your spacecraft can fail.鈥�

When you think about space communications, do you imagine a lagging, crackling radio voice saying, 鈥淗ouston, we have a problem鈥�? No real-life astronaut ever said that but the lagging, crackling radio is real. 

鈥淎s we鈥檝e developed more sophisticated technologies in space, such as imaging and radar systems, we require greater fidelity and security in our communications,鈥� says Rattenbury. 鈥淲e鈥檙e reaching a limit to what can be done with radio frequencies, because there鈥檚 only a certain amount of bandwidth, and if you have more data, it takes longer to download that data.鈥�

The solution? To change the wavelength. Like radio waves, laser radiation is part of the electromagnetic spectrum. As anyone who has ever used a CD or DVD can attest, large amounts of information can be transmitted via laser. 

Laser communications between satellites and Earth could also have another benefit: super-secure encrypted communications around the world.

Rattenbury and Cater are working with Jevon Longdell of the University of Otago, who has developed quantum memory, which is able to hold a quantum state for long periods. This makes it possible to create encrypted communications using a quantum-entangled laser beam. Quantum cryptography is virtually unbreakable because any attempt to intercept the signal is detectable. 

鈥淲ith laser communications, you can encrypt it with a quantum state and know for certain whether your data has been interfered with,鈥� says Rattenbury.

鈥淭o make the system work, we鈥檇 need to have quantum memory in space,鈥� says Cater. 鈥淣ick鈥檚 working on collecting the photons and my part of it is the systems that would keep a quantum memory operating in orbit.鈥�

Cater and Rattenbury have plans for even more space-related projects.

One idea is to use carbon fibre-reinforced polymer parts in space to take advantage of the light weight and unusual properties of the material.

Another idea involves synthetic aperture radar, which can penetrate cloud and smoke. Cater, Rattenbury and  of the Department of Electrical, Computer, and Software Engineering are looking at using the technology on small satellites for purposes ranging from spotting ships 鈥� maritime surveillance 鈥� to detecting tectonic movements on land.