On April 19, 2026, the Honor Lightning humanoid robot ran a half-marathon in 50 minutes and 26 seconds, beating the human world document by 7 minutes and the most effective robotic time from 2025 by virtually two hours.
How did they do it? Is there some magical know-how or method that unlocked this efficiency? How did they beat the considerably better-known Unitree (who reportedly needed to provide an ice backpack to attempt to full the race with out overheating)? My doctoral thesis concerned building and controlling hopping and running robots, and since then I’ve tried to design and build efficient commercial legged robots, giving me a good concept of the constraints concerned. On this article, we check out the basic underlying constraints to attempt to reply these questions.
The Physics of Operating
Running consists of alternating phases of a leg pushing towards the bottom (“stance part”) and the physique flying by means of the air (“aerial part”). Within the aerial part, the physique falls attributable to gravity, dropping vertical momentum. The leg in stance part pushes towards the bottom to redirect the vertical momentum upward, whereas the opposite leg swings ahead to reposition for the following foothold.
Electric motors use vitality to supply torque- the upper the torque, the extra vitality misplaced as warmth. Including a geartrain after the motor amplifies its torque and reduces its pace. A big discount helps with torque manufacturing, however because the rotor of the motor itself has to spin quicker, it turns into very sluggish at accelerating its output. That is clearly unhealthy for the swing part described above. These competing results imply that for a specific motor, there may be often a candy spot for the gear ratio:
The ability consumed by a robotic leg is minimized at an optimum gear ratio (30:1 on this instance).Avik De/Datawrapper
How Honor Did It
Whereas the Lightning’s motor specs aren’t printed, the hip and knee motors roughly have a 110-150mm outer diameter. For an approximate set of motor parameters, I appeared to the ILM115x25 motor attributable to its related dimension and detailed specs.
We will use a easy physics mannequin to estimate the facility consumption for working at 7 m/s (the Lightning’s common half marathon pace) as gear ratio varies:
The sunshine blue curve exhibits methods to decide the optimum gearing (45:1). The darkish blue curve exhibits how a lot warmth will likely be produced within the knee motor, ~150W for the optimum gearing.Avik De/Datawrapper
We see that the drivetrain shouldn’t be magical: with a gear ratio chosen for this activity (we’ll return to this under), the approximate robotic energy consumption could be a really affordable 400W.
Nonetheless, the dissipated knee energy ( usually the primary thermal limiting issue) is ~150W. That is virtually an unavoidable consequence — working at human speeds with a humanoid-sized robotic will inevitably generate this quantity of warmth! Over a protracted interval, protecting the motor from overheating could be a problem, however the Lightning has a trick up its sleeve:
In accordance with Honor, the liquid – cooling pipes penetrate deep into the motors like capillaries. The excessive – energy liquid pump has a warmth – change circulation charge of greater than 4 liters per minute. Every of the 4 drive motors within the decrease limbs is supplied with an unbiased liquid – cooling circuit.
Liquid cooling shouldn’t be new, however it’s undoubtedly not a commodity. It has proven up in analysis periodically, and on the industrial aspect Apptronik tried it for a few of their prototypes however (to my information) doesn’t apply it to their predominant Apollo platform. Primary air convection-based cooling wouldn’t repeatedly have the ability to extract 150W out of the knee motor, and so the cooling know-how is a key enabler of this kind of efficiency.
Why Others Couldn’t Compete
Why did Honor’s rivals, together with extra established and widely-shipped humanoids comparable to from Unitree or Agibot, not compete as properly?
We will use the identical mannequin to generate an equal energetics plot for strolling at 1.5 m/s, a way more modest however doubtlessly extra frequent exercise for a industrial humanoid robotic:
The strong and dashed mild blue strains present a running-optimized design, whereas inexperienced strains present a walking-optimized design. The optimum ratio for strolling is far decrease (30:1 vs 45:1). Nonetheless, the facility dissipated within the knee motor whereas working (darkish blue) is far increased at 30:1 vs 45:1—the worth to pay for working with a walking-optimized design.Avik De/Datawrapper
The plot provides a brand new inexperienced curve for the strolling energy, and the optimum gearing is considerably totally different!
Let’s say you design your robotic to excel on the regular strolling activity and select the inexperienced design with 30:1 gearing. The knee motor energy to run a half marathon is over 300W (purple arrow), greater than 2x what we had with the running-optimized design. It wouldn’t be so stunning to want ice packs!
Conversely, visually following the inexperienced curve exhibits that the running-optimized robotic wastes extra energy for strolling. Utilizing bigger motors sized for working will increase the burden of the robotic and wastes energy when it’s standing or strolling. The bigger motors additionally pose sensible points like bumping into objects whereas working in houses or factories.
Closing Ideas
Honor’s half marathon efficiency was a formidable engineering effort and end result. It didn’t want any magical leaps in know-how, however the deployment of the capillary motor cooling answer is a notable advance with out which this working tempo would have been unsustainable. The cooling, weight optimization, and robustness advances could be helpful for extra sensible functions like carrying heavy payloads down the road.
The Honor Lighting robotic [right] has a lot bigger motors driving its legs than the Unitree H1 robotic [left], making it a extra environment friendly runner however a much less environment friendly walker.Left: Wei Zhiyang/Zhejiang Each day Press Group/VCG/Getty Pictures; Proper: VCG/Getty Pictures
Nonetheless, the Lightning shouldn’t be as well-suited to different duties as a robotic designed for higher versatility. Engineering is at all times characterised by tradeoffs, and making the proper ones separates good merchandise from nice ones. With persistently enhancing AI language fashions, this very human ability is changing into probably the most invaluable one an engineer can have.
The information protection appeared to overly concentrate on the truth that the human half-marathon document had been damaged by a robotic. Machines and people have very totally different capabilities and constraints, so why ought to we ever have anticipated the half marathon time for a robotic and human to be associated? As in Deep Blue’s 1997 defeat of Garry Kasparov in chess, the place it couldn’t bodily transfer the items, the Honor robotic’s capabilities are a lot narrower than a human working elbow-to-elbow with different runners whereas visually navigating the course with out GPS. Evaluating the robotic runner to a human runner is simply an apples-to-oranges comparability, and solely dangers diminishing Honor’s engineering achievement on one hand, and human athletic achievement on the opposite.
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