On April 19, 2026, the Honor Lightning humanoid robotic ran a half-marathon in 50 minutes and 26 seconds, beating the human world file by 7 minutes and the most effective robotic time from 2025 by nearly two hours.
How did they do it? Is there some magical expertise or approach that unlocked this efficiency? How did they beat the considerably better-known Unitree (who reportedly needed to provide an ice backpack to try to full the race with out overheating)? My doctoral thesis concerned constructing and controlling hopping and operating robots, and since then I’ve tried to design and construct environment friendly business legged robots, giving me an honest concept of the constraints concerned. On this article, we check out the basic underlying constraints to try to reply these questions.
The Physics of Operating
Operating consists of alternating phases of a leg pushing in opposition to the bottom (“stance part”) and the physique flying via the air (“aerial part”). Within the aerial part, the physique falls resulting from gravity, shedding vertical momentum. The leg in stance part pushes in opposition to the bottom to redirect the vertical momentum upward, whereas the opposite leg swings ahead to reposition for the following foothold.
Electrical 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 for the reason that rotor of the motor itself has to spin quicker, it turns into very sluggish at accelerating its output. That is clearly dangerous for the swing part described above. These competing results imply that for a specific motor, there’s normally 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 resulting from its related dimension and detailed specs.
We will use a easy physics mannequin to estimate the facility consumption for operating at 7 m/s (the Lightning’s common half marathon pace) as gear ratio varies:
The sunshine blue curve exhibits the best way to choose the optimum gearing (45:1). The darkish blue curve exhibits how a lot warmth will probably be produced within the knee motor, ~150W for the optimum gearing.Avik De/Datawrapper
We see that the drivetrain isn’t magical: with a gear ratio chosen for this process (we’ll return to this beneath), the approximate robotic energy consumption could be a really affordable 400W.
Nevertheless, the dissipated knee energy ( sometimes the primary thermal limiting issue) is ~150W. That is nearly an unavoidable consequence — operating at human speeds with a humanoid-sized robotic will inevitably generate this quantity of warmth! Over a protracted interval, preserving the motor from overheating could be a problem, however the Lightning has a trick up its sleeve:
In line with Honor, the liquid – cooling pipes penetrate deep into the motors like capillaries. The excessive – energy liquid pump has a warmth – alternate circulate price of greater than 4 liters per minute. Every of the 4 drive motors within the decrease limbs is supplied with an impartial liquid – cooling circuit.
Liquid cooling isn’t new, but it surely’s undoubtedly not a commodity. It has proven up in analysis periodically, and on the business facet Apptronik tried it for a couple of of their prototypes however (to my data) doesn’t apply it to their predominant Apollo platform. Fundamental air convection-based cooling wouldn’t repeatedly be capable to extract 150W out of the knee motor, and so the cooling expertise 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 resembling 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 business humanoid robotic:
The strong and dashed gentle blue traces present a running-optimized design, whereas inexperienced traces present a walking-optimized design. The optimum ratio for strolling is way decrease (30:1 vs 45:1). Nevertheless, the facility dissipated within the knee motor whereas operating (darkish blue) is way increased at 30:1 vs 45:1—the value to pay for operating 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 process and select the inexperienced design with 30:1 gearing. The knee motor energy to run a half marathon is over 300W (pink arrow), greater than 2x what we had with the running-optimized design. It wouldn’t be so shocking 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 operating will increase the load 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 properties or factories.
Closing Ideas
Honor’s half marathon efficiency was a powerful engineering effort and outcome. It didn’t want any magical leaps in expertise, however the deployment of the capillary motor cooling answer is a notable advance with out which this operating tempo would have been unsustainable. The cooling, weight optimization, and robustness advances might 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 Photos; Proper: VCG/Getty Photos
Nevertheless, the Lightning isn’t as well-suited to different duties as a robotic designed for larger versatility. Engineering is at all times characterised by tradeoffs, and making the right ones separates good merchandise from nice ones. With persistently enhancing AI language fashions, this very human talent is changing into probably the most beneficial one an engineer can have.
The information protection appeared to overly concentrate on the truth that the human half-marathon file 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 operating 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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