Using Ion drives to propel spacecraft and repurposing space debris as fuel sounds like the realm of science-fiction, but it’s not. We’re discussing the work of Paddy Neumann from Neumann Space, an Australian company soon to have their technology tested on the International Space Station. The Neumann Drive is a type of ion drive that Dr Neumann developed as a part of his PhD, it’s also a technology that has bested the efforts of NASA in terms of fuel efficiency and energy output.
Theoretically, it can use space junk as fuel, potentially making it a part of the solution to the problem of polluting environments, and shooting ourselves in the foot. We spoke with Paddy to try to understand how the Neumann Drive works, in as lay terms as possible. We also delve into the nightmarish (potentially species-ending) Kessler Syndrome, rogue satellites, and what’s next for space exploration.
The origins of this story go back to Paddy’s early days at University, where he had trouble staying awake during class. “I did as much practical work as I could because it’s kind of hard to fall asleep in a lab”. This lead to a practical project on plasma diagnostics, “measuring what’s going on inside a plasma discharge…how it’s all behaving, how hot and how dense the electrons are in the plasma”.
“I took all these measurements, did a little bit of processing on them, and one of the things that popped out of the processing was the average effective velocity of the plasmas. Turns out, under the conditions I was looking at, that the average effective velocity of the titanium ion was about 23km/s.” Paddy went on to explain that the velocity of an ion being accelerated out the back of a Hall-effect thruster, averages around 18km/s, a fairly significant increase. Throughout his university career, Paddy furthered his research, looking for the ideal shape for electrodes and measuring the efficiency of solid materials as fuel sources.
With years of research behind him, Paddy formed the company that brought his University assessments to life. So far, the results are promising.
“One of the comparison metrics that people use to compare different thruster technologies is called ‘specific impulse’, it’s like miles per gallon but for rockets. A chemical thruster tops out around 450 seconds of specific impulse. Hall-effect thrusters at about 1600, 1700. Ion Thrusters at about 3500.” Using the Neumann Drive, and magnesium as a fuel source, Paddy got results around 11,300, which could have positive implications for long distance, return trips.
I asked Paddy to explain the mechanisms behind the technology, in as basic terms as possible.
“The physics behind how it works is very similar to how an arc welder works. In an arc welder, you’ve got the long skinny welding rod, that’s the cathode, the negative part of your circuit. What you clamp the jumper lead cable type-thing onto, the two bits you’re welding together, that’s the anode, that’s the positive side of the circuit.”
“When you bring the tip of the welding rod to the weld piece, you create a very intense electric field between the tip of the rod and the bits you’re welding together. This causes what is called ‘breakdown’. Basically, you’re ripping apart air molecules and making a nice conductive pathway for the electricity to go through the rod, and into the weld piece. This heats up the tip of the welding rod. You get material boiling off the rod, moving down this plasma discharge, and then accumulating on the weld piece.”
“With our system, we use similar physics but in a different environment. We have our cathode and anode, the negative and the positive part of the plasma discharge, but we don’t have an atmosphere”, no air molecules to rip apart.
“So, we need to trigger the arc. We’ve got a little trigger electrode that works like a switch. When we trigger the arc, we can create the conditions necessary to start the plasma, and then we’ve got a capacitor bank to drive the rest of the plasma charge by dropping the energy into the plasma, keeping it going. The plasma is generated by materials being boiled off and evaporated from the surface of the cathode, just like with the welding rod, and then being flung out into the vacuum chamber or away from the spacecraft.”
“As the material moves away it is…pushing back on the spacecraft. Just like when you fire a bullet out of a gun and you get recoil pushing your hand backwards. The exact same psychics happen here for spaceship momentum; we throw exhaust downrange, the entire vehicle gets pushed along.”
Understandable analogies. But, in a video on Neumann Space’s YouTube, Paddy noted that the exhaust from the Neumann Drive is neutrally charged, giving it an advantage in terms of efficiency. Understanding little of physics or chemistry, I sheepishly enquired further.
“With current generation propulsion technologies, the Hall-effect thruster and ion thrusters, the way they work, is they create a plasma from a gas called xenon and then use one of two different methods to extract the ions from the plasma, out of the discharge chamber, and then accelerate them down range.”
“The problem is, if you only throw the ions, then you’re only throwing things that are positively charged. So, the total charge of your spacecraft becomes more and more negative, until you reach a point where the ions get thrown out the back, but then slow down and get attracted back, and then redeposit back in the spacecraft. You’re not actually going anywhere. What these other systems then need is a charge neutralisation system.”
Essentially, A system that fires electrons into the exhaust stream. Systems like these require a lot of energy to run and adds complexity to the engineering of the drive. Another benefit is that using solid metals as fuel is much less hazardous than storing and transporting volatile liquids or gasses, and could potentially save space and weight on a spacecraft.
One of the more terrifying problems with space exploration is that at a species-wide level, we’re messing it all up. Humans have been exploring space for less than 60 years. In that time, we’ve almost reached a point that Donald Kessler warned of, a point where there is so much debris orbiting our planet, that to exit our atmosphere will be too dangerous. The problem of debris worsens when space junk collides, exponentially increasing the amount of shrapnel.
“Kessler Syndrome is a very scary thing and we’re starting to see the early signs effects of it now with debris collisions becoming more common. It’s only going to be a matter of time until you have a few large collisional events, creating even more debris than is currently in space.”
Paddy described the collision between Kosmos-2251 and Iridium 33 that occurred about 12 years ago, that the Chinese have tested anti-satellite weapons which have added considerably to the debris, and that there’s a rogue satellite in orbit, the Envisat; eight and a half tonnes of non-responsive metal hurtling around our planet. All problems in need of resolution. I asked Paddy if his technology could be a part of the solution to the problem of space junk and debris.
“We reckon it could be…As you’ve mentioned before, our system uses solid conductive materials; titanium, magnesium, aluminium, they all work to a greater or lesser extent…These metals are light and strong, they are the aerospace metals for those reasons. It’s what you build rockets out of, therefore it’s what space junk is made of.”
It would likely require some form of autonomous or semi-autonomous ‘junk hunter’, as Paddy described them, to collect materials from orbit and transport them to a plant for reprocessing. Though this sounds like science fiction, “there’s a particular mission the European’s have been working on in recent years”, the previously mentioned rogue Envisat.
“They’re planning to put up a half tonne worth of junk hunters, to go up there and grapple onto the bits where Envisat got bolted onto its rocket launch vehicle. And then turn on some chemical rockets, so it can be safely de-orbited into the South Pacific.”
Looking to the more immediate future, the Neumann Drive is at Technology Readiness Level (TRL) 4…or 5, “depending on how charitable you want to be”. The next step is to test the drive in a relevant environment, obviously in this case, space.
“We contacted Airbus Defence and Space to be part of their Bartolomeo Mission Platform, to be able to test our system on the side of the International Space Station, starting mid-2019. We’ll get to test our thruster in space, an important test…Additionally, we don’t need all the space for ourselves. We need about 20-25kg, we need about another 20kg for structural members, as well as power points and networks, and our mass allotment is 125kg total. That leaves 80-odd kilos for us to be able to on-sell to other people.”
Surprisingly, Neumann Space sold a kilogram to SA Department Education and Childhood Development, “SA High Schools have a space program now.” Other than funding, it seems that governmental involvement in space exploration has tumbled from its heights during the Space Race.”
“In the early days was space travel is the playground of large governments doing things for national prestige. As the 60s wore on, people were working on figuring out how to use space for commercial purposes.” More recently, “about 70% of the worlds space revenue has been commercial…20% of the space business has been governmental, and the remaining 10% is NASA”.
For further developments in the Neumann Drive project, check the Neumann Space website for the latest.