Robotics 5 November 2026 5 MIN READ
From BigDog to Atlas: Hydraulic to Electric
From the 2008 BigDog paper to a production electric Atlas in 2026: what Boston Dynamics and its sources say, the specifications and what is still unknown.
THE SHORT ANSWER
BigDog, a 2008 hydraulic robot with a combustion engine, carried loads across rough ground but was loud and expected to fall over. Boston Dynamics retired hydraulic Atlas in 2024 and unveiled a production electric Atlas in January 2026, with 56 degrees of freedom. Its working record is not yet public.
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The problem BigDog was built to solve
The clearest starting point is a 2008 paper by Marc Raibert and colleagues at Boston Dynamics, presented at the IFAC World Congress in Seoul. Its first line states the motive: less than half the Earth’s land can be crossed by wheeled and tracked vehicles, while people and animals on legs can go almost anywhere.
The team had built legged robots for decades, but the earlier machines, developed at Carnegie Mellon and MIT between 1981 and 1995, were powered through hoses by a remote hydraulic pump. The paper names two limits to fix: the robot needed its own power so that it could work in the field without hoses, and it needed control software that kept it upright on rough ground. BigDog, funded by DARPA with extra support from the US Marine Corps and Army, was the attempt to do both.
What BigDog was
The numbers in the paper describe a very different machine from today’s humanoids.
- Size and weight: about 109 kg, roughly 1 m tall, 1.1 m long and 0.3 m wide.
- Power: a water-cooled two-stroke combustion engine of about 15 horsepower drove a hydraulic pump. The oil fed hydraulic cylinders at the joints, four powered joints per leg plus one passive one.
- Senses: about 50 sensors for body motion, joint position and force, and the state of the engine and hydraulics.
- Control: a human steered it by radio, giving direction and speed. The robot’s own software worked out how to place its feet and keep its balance.
- Performance: a crawl at about 0.2 m/s, a trot at about 1.6 m/s, and a brief 3.1 m/s bound in the laboratory. It carried 154 kg on flat ground, although the authors say 50 kg was more typical. Its longest continuous run was a 10 km hike lasting 2.5 hours, and its reliability goal was 20 hours between failures.
The paper is just as direct about the downsides. BigDog was loud, “sounding like a motorcycle”, and the plans for the next version included a custom muffler, a four-stroke engine, an enclosure for the engine and pump, and “possibly optional hybrid power”. The authors also expected it to fall over in the field and wanted it to be able to right itself.
Hydraulic Atlas, then the switch
The Atlas humanoid grew out of the same line of work. The company’s own account describes more than a decade of humanoid research, from PETMAN, a machine used to test protective clothing, to the hydraulic Atlas performing parkour. In April 2024 Boston Dynamics announced the retirement of the hydraulic Atlas and unveiled a fully electric successor. IEEE Spectrum summed up the change in a sentence: batteries and electric actuators, “no more messy hydraulics”.
What the company says it gained is concrete but short on figures. The electric Atlas would be stronger and have a wider range of movement than any earlier generation, and it would not be limited to a human range of motion. The company also said the first customer would be Hyundai, with a small group of partners testing applications over the following years, the same approach it had used for Stretch, its box-moving robot.
The product, as announced in January 2026
On 5 January 2026, at the CES show in Las Vegas, Boston Dynamics presented the production version of Atlas and said it would start building the robots at its Boston headquarters. The published specifications are:
- 56 degrees of freedom, most of them fully rotational joints;
- a reach of 2.3 m and a lift of up to 50 kg;
- operation between -20 and 40 degrees Celsius, with water resistance;
- three ways to control it: autonomous, teleoperated or by tablet;
- the ability to walk to a charger and swap its own batteries.
On supply, the company said all 2026 deployments were already committed, with fleets going to Hyundai’s robot application centre (RMAC) and to Google DeepMind, and more customers planned for early 2027. Hyundai Motor Group’s own announcement adds its plans: it aims to build a production system for 30,000 robots a year by 2028, to put Atlas on repetitive parts-sequencing tasks from 2028 and to extend it to component assembly by 2030. These are targets, not results.
What the sources do not tell us
The company’s announcements give no price, no battery life, no measure of how many parts an hour Atlas moves, and no failure rate. The 2008 paper at least stated a reliability goal, 20 hours between failures; the 2026 material we read gives no such figure. Until the first fleets report real working data, the claims about industrial usefulness remain claims.
The 2008 and 2026 figures also describe different jobs. BigDog carried a load across country; Atlas lifts and places objects in a factory. Comparing 154 kg with 50 kg would say nothing useful.
Our take: the interesting change is less about hydraulics against electric motors than about what a machine is designed to be. BigDog was built to prove a robot could keep its balance outdoors, and its builders listed noise and falls as problems to solve. The 2026 Atlas is described in the maker’s own words as “the most production friendly robot we’ve ever designed”, with fewer unique parts and components chosen to suit automotive supply chains. That is the language of something meant to be built in numbers and maintained like a car part. Whether it works in a real factory is the part still to be shown.
Questions and answers
What powered BigDog?
A water-cooled two-stroke engine of about 15 horsepower drove a hydraulic pump, which fed hydraulic cylinders at the joints. The 2008 paper says it was loud, like a motorcycle.
When did Boston Dynamics retire hydraulic Atlas?
In April 2024 the company announced the retirement of the hydraulic Atlas and unveiled a fully electric Atlas the same week.
What can the 2026 electric Atlas do, according to its maker?
The announced specifications are 56 degrees of freedom, a 2.3 m reach, a lift of up to 50 kg, three control modes and the ability to swap its own batteries. No independent working data was available in the sources we read.
Is Atlas working in factories yet?
The company said all 2026 deployments were committed, with fleets going to Hyundai's application centre and Google DeepMind. Hyundai plans to put Atlas on parts-sequencing tasks from 2028. Those are plans, not results.
Do you agree?
Take it to Chevlume: write your view, add your sources and let others answer. The closed alpha is by invitation.
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Sources
- BigDog, the Rough-Terrain Quadruped Robot (Raibert, Blankespoor, Nelson, Playter), 17th IFAC World Congress, Seoul, 2008 · International Federation of Automatic Control / Boston Dynamics · Accessed
- An Electric New Era for Atlas · Boston Dynamics · Accessed
- Boston Dynamics Unveils New Atlas Robot to Revolutionize Industry (5 January 2026) · Boston Dynamics · Accessed
- Hyundai Motor Group Announces AI Robotics Strategy to Lead Human-Centered Robotics Era at CES 2026 · Hyundai Motor Group · Accessed
- Hello, Electric Atlas (E. Ackerman, 17 April 2024) · IEEE Spectrum · Accessed
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