YAOKI

Dymon Co., Ltd.

Overview

A rover that rides down to the surface inside a CLPS lander’s payload bay has to survive an uncontrolled drop, has no ground crew to right it if it lands wrong, and gets one lander’s worth of power and radio range to work with. Most of the small lunar rovers flown since 2019 answer that problem by keeping mass and part count to a minimum and by making the vehicle indifferent to which way up it ends up [8]. YAOKI is Dymon Co., Ltd.’s answer: a 498 g two-wheeled rover, 15 x 15 x 10 cm, built around a single axle with one wheel at each end of a central body [12], [10], rated to withstand 100 G and designed to keep working after impact and after coming to rest either way up. It flew on the Intuitive Machines IM-2 Nova-C lander, launched 26 February 2025 [1], and was not deployed because the lander came to rest on its side [2].

The single-axle, two-wheel layout with no suspension and no steering actuators is one of two architectures this generation of micro-rovers converged on for the same constraint. JAXA’s SORA-Q, flown on Hakuto-R M1 and again as LEV-2 on SLIM, instead folds a ball into two eccentric hemispherical wheels with a tail stabilizer, trading YAOKI’s axle symmetry for a transformable housing that also serves as the stowed launch configuration [3]. Both designs put the entire mobility and impact-survival problem into passive mechanical geometry rather than into control software, because there is no ground link fast enough to recover a teleoperated vehicle that tips over. A JPL survey of the same period places small CLPS-class rovers like YAOKI within a broader field of extreme-terrain and planetary mobility work [4], and a 2024 review of the surge in lunar landers and rovers from 2019 onward counts nine such missions launched and four failed by that point, the base rate against which IM-2’s outcome sits [8].

The vehicle was originally manifested on Astrobotic’s Peregrine lander under an agreement announced on 14 October 2019, for a 2021 flight [11]. Peregrine Mission One launched instead on 8 January 2024 without YAOKI aboard, and was lost in cislunar space after a valve failure ruptured its oxidizer tank about 92 minutes after separation [6]; Dymon’s rover had by then moved to IM-2. Dymon states eight years of development with the base technology completed in 2018 and more than 100 tests passed. The name is from a Japanese proverb about getting up again however many times one falls, and the self-righting design is the literal expression of it [12].

No peer-reviewed or conference publication on YAOKI was located. Vehicle numbers below come from Dymon and from Mitsubishi Chemical Group, which supplied the exterior materials [12], [10]. The NASA conference paper cited [1] covers the IM-2 flight, not the rover.

Specifications

Parameter	Value	Source
Mass	498 g	manufacturer [12], [10]
Dimensions	15 x 15 x 10 cm	manufacturer [10]
Wheels	2, on one common axle	manufacturer [11]
Impact tolerance	100 G	manufacturer [12], [10]
Body material	CFRP with cyanate ester resin matrix	supplier [10]
Wheel material	polyamide-imide
Camera lens treatment	anti-soiling coating
Self-righting	yes, operates either way up	manufacturer [12], [10]

Drive speed, slope limit, obstacle capability, power source, battery capacity, radio band, data rate, processor and thermal limits are not published. For comparison, a compiled record of every vehicle that has actually driven on the Moon puts the operating limit for wheeled lunar mobility at a ground contact pressure below about 7 to 10 kPa and a slope capability around 25 degrees [9]; nothing in the public YAOKI material states where its two-wheel, no-suspension geometry sits against either figure.

Mission profile

These describe IM-2, not the rover.

Parameter	Value	Source
Lander	Intuitive Machines Nova-C, IM-2	[1]
Launch	26 February 2025
Planned surface duration	up to two weeks of lunar daylight
Landing	6 March 2025, Mons Mouton, 250 m from target	[2]
Outcome	lander on its side, rover not deployed
Mission end	7 March 2025

Athena landed on its side inside a crater at Mons Mouton, about 250 m from the intended site [2]. Intuitive Machines did not expect the lander to recharge, given the sun direction, the solar panel orientation and the crater temperatures, and declared the mission concluded on 7 March 2025. NASA’s PRIME-1 suite accelerated several payload milestones before the batteries depleted. Its centerpiece, the TRIDENT rotary-percussive drill built by Honeybee Robotics for this same lander, did not penetrate the surface in that orientation [5]; YAOKI, riding the same lander, was not deployed either. The two payloads failed for the same reason, an attitude the lander was never meant to operate in, not for any fault of their own.

The earlier Peregrine assignment did not fly with YAOKI aboard; the rover moved to IM-2 [11].

Mobility

Two wheels on a single axle [12], described by the manufacturer as the smallest effective rover wheels produced [11]. The architecture has no suspension and no steering actuators; with two ground contacts and a body suspended between them, attitude about the axle is unconstrained, which is why the vehicle is designed to operate inverted. Dymon states it can be thrown into a cave and continue working [10], which is the same requirement as the 100 G impact rating.

Wheels are polyamide-imide, chosen for cold and heat resistance, wear resistance and impact strength, specifically so the wheels survive being dropped onto the lunar surface from a deployer [10]. No drawbar pull, slip or slope data has been published.

Structure and materials

The body is carbon fiber reinforced plastic in a cyanate ester resin matrix, chosen for low permittivity and temperature resistance [10]. It replaced an aluminum design, and the substitution gave about 30 percent lower mass, a five times better safety factor, and about 4 million yen lower lunar transport cost per unit. The deployer that releases the rover from the lander uses the same cyanate ester CFRP. Mass is the cost driver for a vehicle of this class, and the material substitution is quantified against lunar transport cost rather than against structural performance alone.

Power and energy

No solar array, battery capacity or night survival capability is published.

Thermal

Not published as a subsystem [12]. The only thermal information is at material level: the cyanate ester CFRP body is selected for temperature resistance and the polyamide-imide wheels for cold and heat resistance [10].

Autonomy

None claimed in the manufacturer material [12], [11]. The vehicle is operated through the lander. A contemporary micro-rover, MoonRanger, was built for the opposite case, a mission with no real-time link to Earth at all, and its designers found that dead reckoning alone on a lunar analog drifted about 5 percent of distance traveled over an unsupervized traverse [7]. YAOKI’s short-range, lander-relay teleoperation avoids that problem by never asking the rover to navigate further than the lander can see, which is one reason a two-wheel vehicle with no onboard perception is a workable design for this mission class even though it would not be for a multi-kilometer trek.

Communications

Through the lander, which on IM-2 also hosted a 4G/LTE network for other payloads [1]. YAOKI’s own band, data rate and range are not published [12].

Payload and instruments

A camera is the payload. Its lens carries an anti-soiling coating developed against lunar regolith, whose jagged particle shape and electrostatic behavior make it adhere to optics [10]. The photograph above shows the camera aperture flanked by two lamps on the body face. Sensor format, resolution and field of view are not published.

Modes of operation

Deployment is from a dedicated deployer on the lander, from which the rover is dropped to the surface [10].

Technologies developed

The transferable results are material substitutions with quantified outcomes: a cyanate ester CFRP body replacing aluminum at about 30 percent lower mass and five times the safety factor, polyamide-imide wheels qualified against drop impact, and an anti-soiling lens coating developed specifically against regolith adhesion [10]. The single-axle, two-wheel, operates-either-way-up architecture is the second result, and it has not been demonstrated on the lunar surface because the vehicle was never deployed [2].

What is not established

Drive speed, slope limit, obstacle capability, power source, battery capacity, radio band, data rate, processor and thermal design margins have not been published by Dymon or by any third party, and no peer-reviewed or conference paper on the rover itself was located; every number above traces to manufacturer and supplier marketing material [12], [10]. Because YAOKI was never deployed on the lunar surface, none of its mobility, thermal or communications claims have flight validation, and the vehicle’s actual performance against the ground contact pressure and slope limits established for prior lunar rovers [9] remains unmeasured.