Validating Microgravity Mobility Models for Hopping/Tumbling Robots

PI: Issa Nesnas, Jet Propulsion Laboratory

We will test the mobility of a new class of low-mass (<10 kg) hopping/tumbling robots in the low-gravity environment offered by the ZeroG aircraft and on terrains with properties typical of small Solar System bodies: asteroids, Near-Earth Objects (NEOs), and small moons. This is a knowledge payload that seeks to evaluate control and mobility strategies, gather data on the dynamical properties, and validate simulation models of these internally-actuated robots. The tests will inform and refine future design iterations and further our understanding of microgravity mobility dynamics.

Technology Areas (?)
  • TA04 Robotics, Tele-Robotics and Autonomous Systems
Problem Statement

Researchers at Stanford University and at the Jet Propulsion Laboratory have recently been investigating low-mass surface platforms that can traverse the rugged and soft terrains of small bodies, where gravity is extremely low. These platforms impart mobility by generating a reaction force through simple internal actuation mechanisms, enabling them to traverse by hopping (for large surface coverage) and tumbling/shuffling (for fine mobility and instrument pointing). These platforms would position science instruments through a sequence of tumbling and shuffling maneuvers.

Technology Maturation

To date, these platforms have been validated in ground-based microgravity test beds and in physics-based simulation environments, including testing with granular media simulations. Our team has also conducted constrained experiments using a single degree-of-freedom prototype to demonstrate the ability to hop and tumble on flat, soft and sandy surfaces. Preliminary results from our experiments in physical test beds show agreement with our simulations under certain conditions. However, ground-based experimental test beds have limitations due to, for example, internal friction of the gravity-offloading mechanisms, undesired and exogenous dynamical effects, and limited degrees-of-freedom of experimental setups. Therefore, we seek to conduct more comprehensive experiments under the microgravity conditions offered by the parabolic flight of the ZeroG aircraft (727-F200), where such limitations would not be present. Our desired gravity level would be 0.0g +/-0.05g, where we will trigger various tests during the positive microgravity levels. We can gain valuable test data over a range of gravity levels from Martian, Lunar to zero gravity.

Future Customers

Furthering our understanding of mobility and operations around small bodies would have relevance to both NASA's Science Mission Directorate as well as Human Exploration Mission Directorate, thus helping the Space Technology Mission Directorate accomplish its crosscutting capabilities goals.

Flight Experiment Objectives

The primary experiments will study the dynamics of hopping and tumbling, and additional best effort experiments will examine the landing impact following hops and demonstrate attitude control during ballistic hops. The experiments will help us characterize limitations of ground-based test beds and simulations and further our understanding of microgravity mobility, which has implications for future robotic and crewed missions to asteroids and small moons.

Payload Description

Our payload box is a strapped down, sealed 1m x 1m x 1m enclosure that houses a 7 kg robot and a container enclosing the experimental surface. The container will hold one of three simulant/rock combinations that mimic the surface properties of small bodies. The enclosure will be instrumented with telemetry sensors. We will use the telemetry data to accurately reconstruct the trajectory of the robot during each maneuver. The robot will be rigidly secured inside the payload box during aircraft maneuvering and lightly restrained with electromagnets to counter-act negative gravity fluctuations during zero gravity parabolas.

Technology Details

  • Selection Date
    AFO8 (April 2014)
  • Program Status
  • Current TRL (?)
    Successful FOP Flights
  • 0 Parabolic

Development Team

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