Would you hesitate if it cost tens of thousands of dollars every time you tapped the brakes on your car to avoid a collision on a freeway? What if switching lanes to avoid traffic cost the same? Now image you have to control a satellite merge?
On Earth, the price of safe driving can be measured in cents and minutes, and getting the tyres and brake pads checked out during an annual service.
In space, it can be in the tens of thousands of dollars and hours – if not days – of inconvenience. And because fuel is finite in space, once a limited number of moves is used up, your multimillion-dollar asset becomes a liability.
This, says Germany company Morpheus Space, President and co-founder, István Lőrincz, underlines the fundamental problem facing the world’s rapidly expanding orbital space industry.
It’s getting crowded up there – but nobody wants to give way!
“Right now, to this date, we don’t have a serious problem,” he told Cosmos. “We do, however, see a huge problem coming down the line where – if we don’t react now – we might close off the low-Earth orbit environment altogether.”
He warns that time is already too short for global politics to thrash out a treaty over who has the right of way under what circumstances.
“But we do have time to react. We have time to create proper management and control solutions for space traffic. As engineers, we can bring the problem down a notch and push out the politicians.”
That means making safe driving so cheap it’s no longer a conscious issue.
Morpheus’ “NanoFeep” propulsion system of tiny thrusters provides continuous thrust over many years to ensure the satellite can avoid collisions. The thrusters are small enough to fit in the palm of your hand.
Lőrincz says Morpheus Space’s tiny thrusters need a guidance system to ensure they are as efficient as possible. And that means finding a good driver. They pair with Colorado company, Kayhan Space.
“Kayhan Space has ways to find an optimal trajectory,” he says. “And by doing that, they minimise the required propellant for an average avoidance maneuver – to our astonishment – by orders of magnitude.”
Even significant shifts in orbit can come at an insignificant cost, Lőrincz adds. “Looking at the numbers, it became like an average low Earth orbit satellite could perform a maneuver for the price of a pizza party. It’s a game changer.”
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Many low-Earth satellites don’t even have the equivalent of a steering wheel or brake pedal installed. They’re simply coasting in orbit. says Lőrincz.
“It must be terrifying to see that day in, day out and not be able to move out of the way, just sitting there – fingers crossed – waiting for the beep after the conjunction that tells you if it survived.”
When satellites merge
When is it best to burn a limited resource?
“I’ve seen the alerts for possible collisions,” Lőrincz says. “Some companies that operate constellations can see thousands of conjunction warnings per month”.
Making matters worse is not knowing exactly where any given satellite is.
Positions are plotted as “probability clouds.” These are usually ellipsoid bubbles stretching over tens of kilometres.
“It makes you weary,” Lőrincz says. “On the one hand, if I drain a satellite’s fuel tanks, I lose something of value – something of commercial importance. On the other hand, the collision environment gets even worse, and I could maybe take out a lot of other satellites.”
Everything hinges on a single asset – propellant.
“What if we lower the barrier for deciding to move a satellite?” Lőrincz asks. “What if we have such a low barrier for pushing that brake pedal, that an engineer can make the decision? If it did not have to go all the way up to the executives as it won’t cost the company hundreds of thousands of dollars?
The idea of using metal-powered thrusters (which use a spark similar to that generated by an arc welder) has gone a long way towards reducing the size, weight and complexity of giving satellites steerage.
“It’s very dense,” says Lőrincz. “It does not take up much real estate in the spacecraft. And that is very valuable. So if you have an abundance of propellant, then you’ve solved one problem.”
Metal isn’t as powerful as liquid fuel.
High-thrust systems can wait until about an hour before a projected collision and still nudge a satellite hard enough to get it out of the way but Lőrincz says metal thrusters need three to four hours. “So the difference is not that significant. But, with the proper calculations, a manoeuvre can be initiated within minutes, and you don’t even have to throttle it up to maximum”.
No operator, he adds, will wait until the final hours anyway: “If it gets down to the one-day mark, it’s panic mode”.
However, brakes and a steering wheel aren’t enough on their own.
Satellites also need an alert, competent driver.
“We can’t just think in terms of one collision,” says Lőrincz. “We also must look ahead in time. If you’re in a very crowded space and you dodge to avoid a collision, it could mean that you actually generate three others.”
“But, again, we need to go down the political path there because there must be rules and regulations about autonomous movement. Especially when you talk about moving entire constellations across a large chunk of low-Earth orbit.”
That will take time. “Until then, someone will always have to push a button”, Lőrincz says.