ESA's Loader crane would lift 1 tonne off Argonaut landers and place it 6 m away

A scaled prototype of a lunar cargo crane has now been run through its paces in ESA's Planetary Robotics Laboratory in the Netherlands. The machine, called Loader, was built by the Romanian gas-turbine and aerospace institute COMOTI together with Initium Space under ESA's Technology Development Element. The full-size design is meant to lift up to 1,000 kg off a lander such as Argonaut and set it down up to six metres away. What exists today is a demonstrator, and the 1,000 kg figure is a design target, not a measured result.

01The problem: the last six metres

Each Argonaut lander is designed to deliver up to 1,500 kg of cargo to the lunar surface. That cargo may be rovers, science packages or pieces of infrastructure. Once the lander is down, every kilogram of it still has to get from the deck to the regolith.

The two usual answers each cover only part of the job. Ramps work for wheeled payloads. Astrobotic, for example, angled Griffin's ramps up to 33 degrees in its rover-egress tests to cover tipped and rolled landing attitudes. A ramp does nothing for a static instrument, a power unit or a habitat element that cannot drive itself. Robotic arms handle small items but, according to ESA, some cargo, like sensitive science instruments, must sit metres from the lander, beyond a robotic arm's reach. The reason is that the lander's own thermal, vibration and electromagnetic signature would contaminate measurements. This is the engineering rationale for the six-metre reach, though ESA's release does not tie that figure to a specific instrument.

The pressure is growing as cargo gets heavier. NASA's Moon Base plans, as reported by NASASpaceFlight, resize the crewed-rover candidates to about one tonne to match current lander capabilities, and delivery of those rovers is planned on Blue Origin's Blue Moon MK1 using a crane for offloading. A crane is therefore not unique to Europe. It is an emerging pattern for landers that carry tonne-class payloads.

02How Loader is built

ESA and COMOTI describe the architecture in a few strokes:

• Stowage: The crane launches folded on the lander's payload deck and deploys after touchdown. A dedicated cable-management system and a defined unfolding sequence keep it compact when stowed. Cable routing is a real constraint for any folding arm. Harnesses must survive launch and repeated joint motion without snagging, and the unfolding order has to avoid collisions with the payload.
• Levelling: A levelling system keeps the crane vertical even when the lander rests on sloped terrain. A crane with a long reach turns small tilts into large overturning moments and horizontal placement errors, so verticality matters more than it would for a short arm.
• Arm: Above the base, a long arm with two joints ends in a set of grippers. Two joints is a deliberately small number of degrees of freedom. NASA-era lunar crane studies stressed the same logic, with a design objective of minimizing complexity and maximizing simplicity.
• End effectors: One gripper is passive and spring-loaded and locks without power. The other is battery-powered and rotates the load for finer positioning. The passive gripper means a dead battery or a lost power bus does not drop the payload. The powered gripper adds the orientation control that precise instrument placement needs.

The sources give no mass, materials, actuator types or power budget for the crane. Those are the numbers that will decide whether it is a good fit for a lander with a limited payload allowance, and they are not public yet.

03What the lab test does and does not show

ESA robotics engineer Gunter Just said the scaled model lifts 30 kg under Earth gravity, equivalent to a little over 180 kg on the Moon. That is a force-equivalent statement: the model handles about 294 N of load, which is what a 180 kg mass would weigh under lunar gravity. In lunar terms the 1,000 kg target is roughly 5.5 times the capacity of the model. That ratio is my own arithmetic, not a figure from the project. The final crane will be more than twice as big as the prototype, so the full-size structure has to carry a considerably higher load per unit of size than the demonstrator does.

The test was run on Earth, under 1 g, in the lab's sand-covered rock yard. According to New Space Economy's summary, it was a ground test of a scaled mechanism, not a demonstration of lifting a tonne on the Moon. Lower gravity helps with static loads, but it does not remove the harder problems:

• Inertia is unchanged. A swinging or slewing load has the same mass in 1/6 g, so it takes the same effort to start and stop. Low gravity also means less restoring force on a swinging payload, which makes damping and control more important.
• Launch loads dominate sizing. A structure that must survive a rocket launch while folded is typically sized by those loads, not by lunar lifting loads. The sources do not say what Loader's governing case is.
• Thermal and dust environments are absent from this test. The lab validated function and accuracy, which is what Just said it was for.

COMOTI's Daniel Useriu says the demonstrator met, and in some areas exceeded, initial expectations, and that much refinement remains. The sources give no quantitative accuracy results.

04Dust, slope and the Argonaut context

Dust is the failure mode most specific to the Moon. A 2025 ESA workshop presentation on Loader describes it as a concept-stage electro-mechanical system for autonomous deployment of scientific payloads and surface infrastructure. The abstract lists the mitigation options under evaluation as sealed actuators, passive barriers, surface coatings and mechanical design adaptations. Which of these ended up in the demonstrator is not stated. An earlier NASA field-test paper on a lunar crane set related requirements, including robustness to regolith dust and minimizing the number of rotating parts. Those requirements point to a design that is simple and sealed rather than dexterous.

Slope and landing accuracy are also relevant here. Argonaut is designed to land autonomously within 250 metres on the first flight, improving to 50 m by the third. The lander will target the south polar region, where terrain is rough, so a payload-handling system cannot assume a flat pad. That makes the integrated levelling mechanism a core requirement and not an optional extra.

The schedule is tight. Argonaut Mission 1 is planned to launch on a four-booster Ariane 6 by the end of 2030, with later missions every two to three years, and each lander has a designed five-year surface life. ESA frames Loader as usable on "a lander like Argonaut", and COMOTI's own posts describe Argonaut as the baseline. Neither source says Loader is manifested on a specific mission, so whether it flies on Mission 1 or on a later lander is open. Flight hardware would also have to fit the Argonaut architecture, which separates the Lunar Descent Element from the mission-specific Passenger.

05What remains unproven

The next steps are the ones ESA and COMOTI leave open. The full-scale crane has to be built and loaded to its rated capacity. It has to show placement accuracy in thermal vacuum and with simulated regolith contamination, and it needs a flight-style mass budget. The 1,000 kg and six-metre figures describe what the architecture is meant to do, and so far only the 30 kg prototype has been tested. The broader logistics gap is real, though. The Moon will receive more tonne-class cargo than ramps and short arms can place, and a lightweight, unpowered-gripper crane is one credible way to close that gap.