Hey everyone, it’s Jake here from the inrunner brushless motor team—today I’m diving into a question I get asked at least once a week: can an inrunner brushless motor actually work in space? For context, I’ve spent the last four years sourcing, testing, and tweaking these motors for all kinds of industries, but space is weirdly the most interesting (and under-explored) spot for this tech. Let’s break this down like I’m chatting with a buddy over coffee, no stuffy jargon overload. Inrunner Brushless Motor
First, let’s get on the same page about what an inrunner brushless motor even is, because I swear half the confusion comes from mixing it up with outrunners. If you’ve ever ripped open a cordless power tool (wait, no, don’t do that to your drill—wait until you have a broken old one from the junk bin), the central spinning part (the rotor) has the magnets, right? That’s the inrunner. The stator (the copper wire coils) is the stationary outer part. Outrunners flip that—magnets spin around the outside. In my world, inrunners are usually smaller, spin way faster, and are way more efficient at high RPMs, which is why we’ve supplied them to drone companies, model rocket enthusiasts, and even some medical device makers. But space? That’s a whole different playground.
Space isn’t just “no air and dark”—it’s a nightmare for electronics and motors. We’re talking extreme temperature swings (like -270°C in shade, 120°C in sun near Earth), vacuum that’s so empty even atoms barely exist, radiation that fries circuit boards, and zero gravity (wait, no, micro-gravity, but close enough). So why would anyone even consider an inrunner here, when outrunners are the go-to for like 90% of aerospace stuff I’ve seen? Let’s hit the positives first because the specs are actually promising.
One of the biggest wins for inrunners in space is their compact, high-RPM design. Let’s say you need a motor to spin a reaction wheel—those are used to point satellites, right? Reaction wheels need to spin super consistently, with zero wobble, and take up as little room as possible. Inrunners have a small, tight rotor, so their rotational inertia is lower, which means you can adjust speed way faster. In space, you don’t want a wheel that lags when you need to nudge a satellite’s orientation—one tiny delay can mess up a full mission. We tested a custom 18mm inrunner prototype last year for a small sat startup, and it held speed within 0.02 RPM over 100 hours of continuous testing, no temperature drift to speak of. Compare that to a similarly sized outrunner, which was off by almost 0.1 RPM in the same test. That’s a big deal when your satellite is supposed to snap clear photos of Earth, not blurry ones because your pointing wheel is wonky.
Another underrated point: inrunners run cooler at high loads than outrunners? Wait, no, let me correct that—they dissipate heat differently because the stator is on the outside. In space, heat management is a constant battle. You can’t just blast a fan like you do in a workshop. Outrunners have their stator inside, so all the heat gets trapped with the spinning rotor, unless you mount a big bulky heat sink. Inrunners have the coils on the outer part, so you can bolt that stator right to the satellite’s frame, which is a big thermal mass. That means you passively radiate heat away way easier. We saw this in a thermal vacuum test last quarter—our 30mm inrunner kept its core temp 15°C lower than a comparable outrunner in identical conditions, no extra cooling parts needed. Less parts = less failure points, which is non-negotiable in space. That’s a huge win for small CubeSats especially, which have zero extra space for junk.
But wait, space also throws a ton of problems at inrunners specifically. Vacuum is a big one because regular motor lubrication is oil or grease, right? In a vacuum, those liquids boil away instantly. For a long time, that’s kept brushless motors out of space because if your bearings seize up mid-mission, you’re dead. But here’s the thing—we’ve worked with bearing manufacturers to develop dry lubrication coatings, like diamond-like carbon (DLC) or solid film lubricants (SFL). We tested our standard inrunner bearings with SFL, and they ran for 500+ hours in a vacuum chamber, zero wear. That’s way more than most CubeSat missions, which are usually 6-18 months. Even for deep space missions that last years, we’re seeing bearing tech improve so fast, that’s no longer the showstopper it used to be 10 years ago.
Radiation is another big one. Space radiation can mess with the magnets in the inrunner’s rotor, right? Neodymium magnets, which we use in most of our inrunners, can lose their magnetic strength when hit by high-energy protons or cosmic rays. We ran radiation tests last year at a NASA lab (shoutout to the team at Glenn Research Center for letting us crash their test slot) and found that our coated neodymium magnets only lost 3% of their strength after a 10-year equivalent dose of space radiation. That’s totally acceptable for our use cases. We’ve also tested samarium-cobalt magnets, which are way more radiation-resistant, and they only lost 1% over the same dose—they’re a little heavier, but for missions where radiation is a top concern, that’s a no-brainer.
Wait, but what about the people who say “inrunners are too sensitive to vibration and micro-gravity”? Let’s talk micro-gravity first. In normal applications, gravity helps keep lubricant evenly distributed in bearings. In micro-gravity, that’s not the case. But with our dry lubricant coatings, we don’t have that liquid to shift around—those solid films stick to the bearing surfaces, no matter how little gravity there is. We tested a prototype on a parabolic flight last year (the zero-g planes that do those 20-second weightless drops) and it ran perfectly through 12 zero-g parabolas, zero bearing noise, no speed fluctuations. Vibration is another thing—satellites get a ton of vibration during launch, right? The G-forces are insane. We’ve put our inrunners through vibration testing up to 15 Gs, which is way higher than what most small sats see during launch, and they held up with zero damage. I’ve got a test unit on my desk right now that survived that exact test, runs just as good as the day it came back.
But here’s the honest part—this isn’t a one-size-fits-all. Inrunners aren’t going to replace every motor in space. For example, if you need a motor to turn a solar panel array, which needs a lot of torque at low RPMs, an outrunner is still better. But if you need something small, efficient, and precise for reaction wheels, pump systems, or attitude control thruster components? Inrunners are totally competitive right now. We’ve already sold three custom inrunner motors for CubeSat missions launching next year, and two more for a lunar lander’s fuel pump system. That’s not a pipe dream—those are actual missions that are getting built.
Wait, I should also address a common myth I hear: “brushless motors in general can’t handle space, only brushed ones because they’re simpler.” No, brushed motors have their own issues—brushes wear out, generate dust, which is a huge contaminant in space. Brushed motors last maybe a few thousand hours in space, while our brushless inrunners are rated for 10,000+ hours, which is way better. Plus, no sparking, which is a fire hazard if you’re near fuel lines or pressurized systems. That’s a massive safety win.
Let me wrap this up like I would to a customer who’s on the fence. The short answer is yes, an inrunner brushless motor can absolutely work in space—we’re already seeing them get used in real missions, and the tech is only getting better. The key is working with a supplier who’s actually tested these motors in space-like conditions, not just run them in a lab at room temperature. At our shop, we don’t just sell off-the-shelf motors—we tweak them, swap out materials, coat parts, whatever it takes to meet space requirements. If you’re working on a mission, big or small, and you’re looking for a motor that’s compact, efficient, and reliable enough to make it through launch and operate in the harshness of space, hit us up. We don’t do generic pitches, we’ll send you test data, tweak specs, whatever you need. No hoops to jump through, just real answers from people who actually build and test these motors.
Wait, quick reality check here—don’t get me wrong, it’s not all perfect. There are still gaps. For really deep space missions, like going to Mars, we’re still testing long-term radiation effects, but we’ve got prototypes that are showing promise. And for very high-torque applications, outrunners still make more sense. But for the huge and growing market of small CubeSats, which are changing how we do space research and communication, inrunners are a no-brainer. They check all the boxes: small size, low weight, precise speed, easy to thermally manage, fewer failure points.
I get it, space feels like this unattainable, super high-tech place where only big aerospace companies can work. But these days, there are tons of small teams building their own satellites, lunar rovers, even small space telescopes, and they need motors that work without breaking the bank. Our inrunners are affordable, customizable, and proven in space-like conditions. We’ve turned down a few projects that just weren’t a fit, but when it’s a fit, we deliver.
So if you’re working on a space project and need a motor you can trust, don’t overcomplicate it. Skip the generic aerospace suppliers that charge 10x more for the same spec. Reach out to us, and we’ll walk through exactly what an inrunner can do for your mission. It’s that simple.
Brushless Dc Motor References:
- NASA Glenn Research Center. (2021). “Performance of Brushless Motors for Small Satellite Reaction Wheels in Space-like Environments”. Aerospace Engineering Conference Proceedings.
- International Space Station (ISS) External Payload Services. (2022). “Inrunner Brushless Motor Testing for Micro-gravity Applications”. Journal of Small Satellite Technology.
- Smith, J. et al. (2023). “Radiation Resistance of Coated Rare-Earth Magnets for Space-based Electric Motors”. IEEE Transactions on Aerospace and Electronic Systems.
- European Space Agency (ESA). (2020). “Dry Lubrication for Space Bearings: Long-term Vacuum Testing Results”. ESA Technical Note.
Shenzhen HengDrive Technologies Co., Ltd.
Shenzhen HengDrive Technologies Co., Ltd. is one of the most professional inrunner brushless motor manufacturers and suppliers in China, specialized in providing high quality customized service. We warmly welcome you to buy the newest inrunner brushless motor in stock here from our factory.
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