The ring screw does the work of a ball screw at three to four times the rotational speed — so it couples straight to a high-speed motor. No reduction stage. No recirculating balls. Nothing sliding where the power goes through.
Microgravity Robotics builds high-speed linear actuators for space. Our core technology is the ring screw — a transmission licensed exclusively from the Istituto Italiano di Tecnologia. We are starting where the need is immediate: actuation for launch, docking and in-space systems. We are building toward the robots that will work in orbit and on other surfaces.
Measured on an instrumented bench prototype and in a fielded robotic actuator.
In a like-for-like comparison, replacing a same-size ball screw with a ring screw tripled hopping height. The motor could finally reach its power band during leg extension.
Published in IEEE Robotics and Automation Letters.
Thrust vector control where mass and drivetrain simplicity decide the design.
Force-controlled struts that backdrive freely and carry almost no reflected inertia.
Explosive power-to-mass for mobility and manipulation off Earth.
Invented at the Istituto Italiano di Tecnologia · Exclusively licensed to Microgravity Robotics · Protected by patent US 10,364,871 B2
A ball screw is excellent and nearly universal, but its recirculating balls cap it at roughly 4,000–4,500 rpm — well below where a modern brushless motor is efficient. So ball-screw actuators add a reduction gearbox, and inherit its mass, backlash, losses and failure modes.
A roller screw carries far higher force, but its intricate threaded rollers make it expensive — and it does not solve the speed problem.
The ring screw takes a third route. Two to five rings, each held in an ordinary four-point-contact bearing, engage the rod's thread groove along a line of contact whose geometry guarantees pure rolling. There is no recirculation path and nothing slides where the power is transmitted. The screw couples directly to the motor.
Schematic. Rings roll in continuous line contact with the rod's thread groove; there is no return channel and no recirculation.
Not every application values all six. Some value one.
The nut descends the rod under its own weight — a direct demonstration of how little is lost in the contact.
An efficient screw backdrives. In most machine design that is a nuisance. In force-controlled space mechanisms it is the point.
The mechanism is proven. Two prototypes built, one fielded in a robot, peer-reviewed results, and a measured performance envelope.
What remains is a characterisation campaign — bandwidth, stiffness, endurance and environmental qualification. Every item on it is a standard test on hardware that already exists. None requires redesigning the mechanism.
That distinction matters. We know exactly what we need to measure, how to measure it, and what it costs. Serious evaluators get the full breakdown of which figures are measured, which are derived, and which are still ahead of us.
We are mapping these applications with the engineers who build them. What follows is our own initial assessment, not a finished answer.
Nozzle steering on launchers, kick stages and landers is already linear-electromechanical territory, at forces close to what we have demonstrated. Deleting the gear stage removes mass, backlash and a failure mode from a flight-critical chain.
Soft-capture mechanisms drive a compliant ring on six linear actuators. Free backdrivability and near-zero reflected inertia — properties often counted against screws — are assets here, and a dry contact suits contamination-sensitive proximity operations.
Explosive power-to-mass is the enabling metric for low-gravity mobility. This is where the mechanism has already been fielded.
Ground facilities that reproduce contact dynamics need actuation that is fast, transparent and genuinely force-controllable. Equipment that never leaves Earth is also where a new mechanism can prove itself first.
It is not a replacement for roller screws at sustained very high force, and it is irrelevant wherever the motion problem is rotary. An efficient screw backdrives, so holding a load needs a powered motor or a brake.
We would rather tell you in a paragraph than in a procurement cycle.
If you work on linear actuation in space, we want to know where this fits and — just as usefully — where it doesn't. A rejection with a reason is worth more to us than a polite maybe.
PhD at the Istituto Italiano di Tecnologia and the University of Genoa on mechanism and behaviour co-optimisation of high-performance mobile robots — the work that produced the fielded ring-screw actuator.
LinkedIn →PhD at the Istituto Italiano di Tecnologia and the University of Genoa on the design, build and control of Skippy, a balancing and hopping robot — the first application of the ring-screw actuator on a working robot.
LinkedIn →The ring screw was invented by Roy Featherstone at the Istituto Italiano di Tecnologia. Microgravity Robotics leads the design, space qualification, and market integration of the Ring Screw.
Robotics is where we are going, and it is why the actuation has to be this good.
We are at an early stage and actively looking for engineers who will tell us where this technology fits — and where it doesn't.