A new screw-on propulsion system should keep satellites out of trouble.
Bigger and better usually satisfies the need for speed. But in space, slow and steady is now the subject of a new race.
Traffic up there is getting heavy – fast. Orbital highways are getting congested. Satellite collisions are now a “thing”.
“Space is big – everybody knows that,” says Morpheus Space co-founder and president István Lőrincz. “But there are hubs, like airports and crossroads, where the risk of collision soars. And if you don’t have a traffic management system, those collisions will happen.”
Which is why the ability to “change lanes” has become a matter of urgency. It’s a new concept – at least for space.
Satellites aren’t built with brakes. They don’t have steering wheels. And propulsive engines don’t come as standard. At least, they didn’t. But now the need is real.
That’s why the race is on to fit lightweight, high-efficiency thrusters on satellites in orbit. Morpheus Space has its own contender, the Nano Feep Effect Electric Propulsion unit. It’s already produced results.
“Our NanoFEEP actually performed collision-avoidance manoeuvres in June 2020. It was a world-first,” says Lőrincz.
Earth observation satellites have optimal altitudes for their cameras and sensors, which is why there is competition for particular routes. It’s a similar story for the internet constellations and communications satellites, all of which want to be as low as practically possible to minimise signal lag.
Others are jockeying for the geosynchronous spots that give them broad coverage of productive pieces of the Earth with as much power-generating solar radiation as possible.
“All these regions are becoming crowded,” says Lőrincz, who co-founded Morpheus Space in 2018. “If you’re in business and you lose your satellite, you could go out of business.”
“Optimised orbits need optimised thrusters to keep satellites in place,” says Lőrincz. “In the beginning, thruster optimisation was about getting to the Moon. Now we are optimising for business and profitability. And that changes a lot of things.
“We now have many different types of missions, from low-orbit observation and communications to deep space exploration. They all have very specific needs. And we need to optimise the hell out of each project.”
That means optimising the need to avoid collision with the more than 2,000 low-Earth orbit (LEO) satellites already in operation, along with the tens of thousands of deadly pieces of debris circling the Earth.
The current situation of low-Earth orbit can be compared to the roaring ’20s, when carefree drivers cannoned along our country roads – with inevitably high casualty rates. It took until the 1950s before safer highways evolved into the form we know today.
At present, there is no space traffic management. There are few formal rules of the orbital roads, no highway patrol, and no traffic-light or signage system. This is why space situational awareness is suddenly big business. The need to track every orbiting object bigger than a fingernail has resulted in radar arrays and telescopes popping up planet-wide.
Lőrincz says such systems give satellite operators about a week’s notice of a potential threat.
“So you have seven days to act,” he says. “That means you can coordinate with the other party and decide who moves and where, and still have plenty of time.”
It isn’t about slamming on the brakes or putting the pedal to the metal. “A low-thrust system is more than enough,” he says. “And you want to make sure you can make that dodge manoeuvre as many times as necessary over the lifetime of your satellite.”
Again, optimisation comes into play.
“Obviously, most people want to wait until the last moment because of the time it takes to refine the certainty of a collision. Do you really need to burn fuel on a manoeuvre or not? But that’s where the trade-off comes in. Will I have enough fuel to dodge next time? And the time after that?”
And when it comes to fuel economy – measured in terms of specific impulse (Isp) – electric ionisation outperforms chemical reaction by up to a thousand times.
Fuels ain’t fuels
Space and weight are at a premium in orbit. And strapping a V8 chemical reaction thruster on a lawnmower-sized CubeSat system simply isn’t economical or practical.
“Traditional chemical propulsion systems don’t make any sense at all,” Lőrincz says. “It’s overkill to have a system that can provide such high thrust at very low fuel efficiency. That’s where you turn to electric propulsion. And when you turn to electric propulsion, you have a wide spectrum of options.”
Chemical thrusters combine fuel with an oxidiser. The resulting gas expands and rushes through an outlet to generate thrust. Fuel efficiency is about the rate of expansion.
Ion engines use solar-generated electricity to excite a relatively small number of ions from a fuel source to great speeds. Fuel efficiency in this case is about how easy it is to excite those ions – and how much those ions weigh.
Until recently, the electric-propulsion fuel of choice was gas. The 2007 Dawn asteroid belt exploration mission used xenon gas to power its ion engine. Eventually, the thrust-to-weight ratio gave the probe a speed some 10 times greater than that of a similar 415kg chemical reaction thruster. And there was enough left over to manoeuvre between the Vesta and Ceres planetoids.
Now the preferred fuels are solids – these can be a salt or a metal, as both tick all the space optimisation boxes. Neither needs the volume or weight of storage tanks or distribution systems. And potential failure points, such as valves and pressurised pipes, aren’t required.
“We simply melt the fuel so we can ionise it and produce thrust out of it,” says Lőrincz.
Navigating the highways
Changing lanes to avoid traffic is one thing. Then there’s the challenge of being where you’re needed when you’re needed. And that usually involves turnouts and bypasses. In satellite terms, that means shuffling the orbits of constellations.
“This is something we are working on,” says Lőrincz. “We call it Sphere Flow.”
For example, an observation satellite may pass over the Blue Mountains in NSW twice a day – such regularity and reliability are essential for farming and industry updates. But with raging bushfires in the region, the need for the satellite’s sensors may suddenly become much greater.
“Up until now, the only way to increase the number of observation passes has been to shoot up more satellites. But what we are doing with our propulsion systems is combining it with intelligent software that can nudge the satellite in such a way that four passes can be achieved in a day.”
These are not big manoeuvres, says Lőrincz. Instead, it’s a matter of adjusting a satellite’s orbital phase – nudging it a little in one place to produce a significant outcome in another.
“If you wanted to do this with chemical propulsion systems, you wouldn’t be able to build a satellite big enough. It would be 99% fuel, weigh many tons, and still only have a payload the size of a shoebox. That’s the scale we are talking about.”
Small, light and highly fuel-efficient electric thrusters offer 100 times more movement potential, Lőrincz says. And that opens up immense possibilities to respond to evolving situations.
“You can improve your understanding of a hurricane, for example, if you’re taking more measurements more often. The faster and better predictions that data produces could lead to a city being evacuated sooner – and save lives.”
Full speed ahead
Lőrincz says manoeuvring thrusters shouldn’t be a problem for universities or businesses seeking a foothold in space. He anticipates his scalable, plug-and-play propulsion modules will become as common as mobile phones.
“You just have to fasten a few screws and plug in a connector. You don’t need to design your satellite around a fuel tank, pipes and gimbals. There are no leaks, no valves. There’s nothing that can freeze or break. And the autopilot comes pre-installed.”
And all it takes to put such a thruster setup on a satellite is a mobile phone plan.
“We want our customers to be able to buy modules for a low upfront fee. We build it and deliver it. And once your satellite goes into orbit and is creating revenue, you start to pay a subscription. Instead of buying blocks of data, you buy movement potential – or Delta V. And you can use that as much or as little as you like, and top it up if need be.”
Such an approach would make satellites cheaper to build upfront, he says.
“We de-burden the initial investment. We share the risks of the mission. We then share in its success.”
So, what’s next? Lőrincz makes a bold prediction: “We will become the industry leaders in terms of the number of propulsion systems in space around the end of this year.”
Jamie Seidel is a freelance journalist based in Adelaide.