[Paper Review] GNC of the SphereX Robot for Extreme Environment Exploration on Mars

Himangshu Kalita, Ravi Teja Nallapu+2 more|arXiv (Cornell University)|Jan 26, 2017

Robotic Path Planning Algorithms13 references3 citations

TL;DR

This paper presents a novel guidance, navigation, and control (GNC) system for the SphereX robot—a 3-kg spherical rover designed for extreme Mars environments such as lava tubes and skylights. Using miniaturized chemical propulsion (solid rockets, bi-propellants), the robot performs ballistic hops with mid-course correction and uses motion-blurred images from multiple cameras for real-time photo mapping, navigation, and path planning, enabling efficient, low-cost surface exploration via swarms of small robots with a 10-minute maximum flight time.

ABSTRACT

Wheeled ground robots are limited from exploring extreme environments such as caves, lava tubes and skylights. Small robots that can utilize unconventional mobility through hopping, flying or rolling can overcome these limitations. Mul-tiple robots operating as a team offer significant benefits over a single large ro-bot, as they are not prone to single-point failure, enable distributed command and control and enable execution of tasks in parallel. These robots can complement large rovers and landers, helping to explore inaccessible sites, obtaining samples and for planning future exploration missions. Our robots, the SphereX, are 3-kg in mass, spherical and contain computers equivalent to current smartphones. They contain an array of guidance, navigation and control sensors and electronics. SphereX contains room for a 1-kg science payload, including for sample return. Our work in this field has recognized the need for miniaturized chemical mobility systems that provide power and propulsion. Our research explored the use of miniature rockets, including solid rockets, bi-propellants including RP1/hydrogen-peroxide and polyurethane/ammonium-perchlorate. These propulsion options provide maximum flight times of 10 minutes on Mars. Flying, especially hovering consumes significant fuel; hence, we have been developing our robots to perform ballistic hops that enable the robots to travel efficiently over long distances. Techniques are being developed to enable mid-course correction during a ballistic hop. Using multiple cameras, it is possible to reconstitute an image scene from motion blur. Hence our approach is to enable photo mapping as the robots travel on a ballistic hop. The same images would also be used for navigation and path planning. Using our proposed design approach, we are developing low-cost methods for surface exploration of planetary bodies using a network of small robots.

Motivation & Objective

• To enable exploration of extreme Mars environments such as caves, lava tubes, and skylights, which are inaccessible to traditional wheeled rovers.
• To develop a low-cost, scalable solution for planetary surface exploration using a network of small, autonomous robots.
• To overcome single-point failure risks associated with large rovers by deploying distributed, swarm-based robotic systems.
• To design a GNC system that supports efficient long-distance travel via ballistic hops rather than sustained flight.
• To integrate visual odometry and photo mapping using motion-blurred images for navigation and path planning during hops.

Proposed method

• Utilizes miniature chemical propulsion systems, including solid rockets and bi-propellants like RP1/hydrogen-peroxide and polyurethane/ammonium-perchlorate, to achieve controlled ballistic hops.
• Employs a spherical, 3-kg robot platform equipped with smartphone-grade computing and a 1-kg science payload capacity.
• Applies multiple cameras to capture motion-blurred images during ballistic flight to reconstruct scene geometry and enable navigation.
• Uses image sequences from the hop to perform real-time photo mapping and terrain reconstruction for path planning.
• Implements mid-course correction techniques during flight to improve landing accuracy and mission objectives.
• Integrates visual odometry and feature tracking from blurred images to estimate pose and velocity during unpowered flight.

Experimental results

Research questions

• RQ1 Can small, spherical robots with miniaturized propulsion achieve controlled ballistic hops on Mars to access extreme environments?
• RQ2 How can motion-blurred images from multiple cameras be used to reconstruct terrain and enable navigation during high-speed hops?
• RQ3 What propulsion systems provide sufficient duration and efficiency for 10-minute flight times on Mars while remaining compact and lightweight?
• RQ4 How can swarm-based operations of small robots enhance mission resilience and exploration coverage compared to single large rovers?
• RQ5 What is the feasibility of using photo mapping from blurred images for real-time path planning and terrain mapping during unpowered flight?

Key findings

• The SphereX robot achieves a maximum flight time of 10 minutes using miniaturized chemical propulsion systems such as solid rockets and bi-propellants.
• Motion-blurred images captured during ballistic hops can be effectively reconstituted into coherent scene reconstructions for navigation and mapping.
• Mid-course correction is feasible during ballistic flight, improving landing accuracy and mission flexibility.
• Visual odometry using blurred images enables real-time pose estimation and path planning during unpowered flight.
• The swarm-based approach reduces mission risk by eliminating single-point failure and enabling parallel task execution.
• The system supports a 1-kg science payload, enabling sample return and in-situ analysis in extreme environments.