VIDEO: Thought Leader Series – Neutralizing Gravity on Earth

Gravitational force varies significantly from Earth, to the Moon, and Mars. In order to prepare astronauts to work in a variety of environments, NASA must continuously develop innovative training systems.

NASA Johnson Space Center is home to the Active Response Gravity Offload System (ARGOS), which simulates reduced gravity environments. Learn about this unique training system in our August Thought Leader Series, presented by The University of Texas Medical Branch (UTMB).


August Thought Leader Series panelists include Paul Valle, ARGOS project manager at NASA Johnson Space Center; Jocelyn Dunn, human performance engineering at KBR, supporting the NASA Human Physiology, Performance, Protection and Operations (H-3PO) laboratory; and retired NASA astronaut Mike Foreman.

Valle oversees ARGOS operations for human testing and leads the development of the future next-generation ARGOS. As the project manager, he interfaces with internal and external test and training customers for ARGOS, leads the operations team that operates the system, and leads an engineering team to develop the next-generation human-rated ARGOS.

Dunn serves as the technical lead for the Space Suits and Exploration Operations (SS&EO) technical area of H-3PO. This team supports astronaut training for extra-vehicular activities (EVAs, or spacewalks), physiological data analysis and modeling to support EVA planning, and lunar analog testing of next-generation spacesuits, tools, and concepts of operation. Prior to joining H-3PO, Jocelyn worked as a research scientist for the NASA Cardiovascular and Vision laboratory managing and analyzing data from bed rest and ISS flight studies.

Foreman was selected as an astronaut in 1998. A veteran of two space flights, he flew on STS-123 and STS-129, and has logged more than 637 hours in space, including five spacewalks. Those spacewalks were instrumental in the construction of the International Space Station. Following his own Astronaut Candidate training, he was assigned technical duties in the Astronaut Office Space Station Branch representing the Astronaut Office on training issues. During his final three years at NASA, he served as the Safety Branch Chief in the Astronaut Office. Foreman now serves as Mayor of Friendswood, Texas.


ARGOS is designed to simulate reduced gravity environments, such as lunar, Martian, or microgravity, using a system similar to an overhead bridge crane.

Currently under continuous development and improvement, ARGOS is intended to support testing, development, and training for future missions to the Moon, Mars, asteroids, or any other celestial destination. It is also intended to support EVA training for NASA’s ongoing activities on the International Space Station.

ARGOS uses an inline load cell to continuously offload of a portion of a human or robotic payload’s weight during all dynamic motions, which can include walking, running, and jumping under lunar or Martian gravities, as well as a wide range of microgravity activities.

Using a cable angle sensor, ARGOS actively tracks and follows the payload’s motion in all horizontal directions to maintain a vertical offload force. The facility is capable of supporting surface operation studies, suit and vehicle requirements development, suit and vehicle design evaluation, robotic development, mass handling studies, and crew training with both suited and shirt-sleeved subjects.

The current steel structure accommodates movement in all three directions of motion (one vertical and two horizontal). The ARGOS facility is rapidly reconfigurable to allow for a quick turnaround between different tests and a variety of surface or training analogs.

Various interfaces to the system (also known as gimbals) have been developed to provide a full range of natural motion for a realistic simulation. These gimbals have been developed for both human (suited and shirt-sleeve) and robotic subjects, and are specialized for various test situations (such as planetary gravities or microgravity).

The horizontal axes are driven by electric motors that are attached to friction drive wheels which drive on the underside of the trolley rails. Motion of the subject is measured by a cable angle sensor, which is used to command the system to keep the lifting mechanism centered above the load. In addition, ARGOS is designed to accurately reproduce a microgravity environment. This means that a force in any direction results in constant velocity motion until another force acts on the payload, which results in high fidelity testing and training.

The first-generation ARGOS system was extensively tested and evaluated with both human and robotic subjects over the course of approximately two years and was retired in July 2012.

A second-generation system is currently in use and provides improved dynamics and sensitivity, as well as an increased lifting capacity of 750 pounds. The second-generation system also corresponded to an increase of the structure height from 18.5’ to 25’ to provide a larger simulation envelope.

Learn more about Thought Leader Series

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