Kalind Carpenter

Castable Bulk Metallic Glass Strain Wave Gears: Towards Decreasing the Cost of High-Performance Robotics

The use of bulk metallic glasses (BMGs) as the flexspline in strain wave gears (SWGs), also known as harmonic drives, is presented. SWGs are unique, ultra-precision gearboxes that function through the elastic flexing of a thin-walled cup, called a flexspline. The current research demonstrates that BMGs can be cast at extremely low cost relative to machining and can be implemented into SWGs as an alternative to steel. This approach may significantly reduce the cost of SWGs, enabling lower-cost robotics. The attractive properties of BMGs, such as hardness, elastic limit and yield strength, may also be suitable for extreme environment applications in spacecraft.

Surface mobility on ocean worlds

Understanding the geology and determining the origins for Ocean World bodies like Europa and Enceladus are science goals defined in the Decadal Survey of 2013. Long range mobility at an appropriately selected site on the surface and with the requisite science instruments will address these goals. The challenges for mobility are rugged terrain, unknown and potentially soft regolith, extremely low temperature, and on Europa, possible corrosive materials and exposure to radiation. We have designed and prototyped a concept vehicle that can handle a wide range of topography and terra-mechanics conditions that we believe is needed for successful roving on ocean world bodies. The concept has been analyzed, optimized, simulated, and designed. The results from operating and testing the prototype are reported in this paper.

Long reach sampling for ocean worlds

Reaching beyond the immediate vicinity of a lander to place instruments or collect samples on ocean world bodies has many benefits. These include: an order-of-magnitude or more increase in the area and consequent choices for accessing samples or making observations compared to past lander-based manipulator systems, the ability to deploy samplers and instruments over the extreme topography expected on ocean worlds, and accessing crevasses and vents from a safe distance. We have developed prototypes of concepts for long reach sampling and for deploying instruments and sampling systems on ocean worlds. In the paper, we describe a self-righting system to anchor and collect samples up to 20 cm below the surface and two options for sampler or instrument deployment at distances greater than 10m from a lander. The concepts and results from tests on prototypes are described in the paper.

Enceladus Vent Explorer Concept

Enceladus Vent Explorer (EVE) is a robotic mission to enter Enceladus vents. It would send two types of modules: Surface Module (SM) and Descent Module (DM). SM is a lander that lands within a few hundred meters from the entrance of an erupting vent. After a successful landing, it deploys a single or multiple DMs. First, a DM moves to a vent and descends into it. It then performs in-situ science investigations in the vent using miniaturized instruments such as microscopic imager and a microfluidics chip. Finally, it collects samples in the vent and delivers to instruments on SM for detailed analysis. Out trade study concluded that the most robust configuration of the DM would be a limbed robot that climbs down the vent using ice screws. The ice screw is a hollow metal screw used by ice climbers for making a strong anchor on ice walls. DM would rely on a power and communication link provided by SM through a tether. Should EVE be realized, it could enable not only the direct confirmation of extraterrestrial life but also the characterization of it. Comparative study of lives on different worlds would provide clues to the secret of the genesis of life.

Pop-up mars rover with textile-enhanced rigid-flex PCB body

This paper presents a novel manufacturing paradigm for constructing origami-inspired pop-up robots for future space exploration missions. The new approach uses a textile-enhanced rigid-flex printed circuit board (PCB) to implement a folding robot chassis using robust, spaceflight-tolerant materials, and integrates the robot electronics directly into the chassis for added compactness. The new approach also decouples the mechanical and electrical functions of the chassis flexures for improved kinematics and lifetime. This manufacturing paradigm was used to build PUFFER (Pop-Up Flat Folding Explorer Robot), a self-actuated pop-up rover being developed to provide a low-payload-cost mobility enhancement for future NASA missions.

Milli-watt radioisotope power to enable small, long-term robotic “Probe” space exploration

Milli-watt Radioisotope Power Systems (RPS) based on Radioisotope Heater Units (RHUs) could be an ideal power source for certain spacecraft that cannot use solar power due to large distances from the sun, or other environmental constraints, and where they enable or significantly enhance the ability of a mission to meet its scientific or operational goals. Various modular, compact RHU-based thermoelectric (TE) generator concepts developed or derived from current NASA Small Business Innovation Research (SBIR) projects satisfying this need have been investigated. These modular, compact and low mass power systems could support small, highly-mobile robotic exploration packages, and could be incorporated into different robotic package concepts, spacecraft or satellites. Current modular RPS design concepts with 40mW, 80mW and 120mW power levels use RHUs and Bi2Te3 TE converters. Skutterudites materials could be used in the future if new higher thermal energy output and higher temperature miniature heat sources were developed, for example, using technologies currently in the General Purpose Heat Source (GPHS) used in higher electric power output RTGs. Small (a.k.a., “mice-like”) robotic packages could effectively utilize these RHU-driven power levels to accommodate crawling, climbing, monitoring, taking measurements, and communicating during long-term planetary missions aimed at gathering environmental and geologic data (i.e., over multiple decades). Waste heat from the cold side of the TE converter could also be directed toward the electronics and / or energy storage (e.g. batteries) to keep them within design temperature ranges. In addition to power generation and electronics / battery heating, the RHU / TE configuration could be designed to survive an external 500°C bake out procedure for critical spacecraft sterilization, environmental certification and planetary protection. Analytical studies have been performed to optimize various design configurations for power, mass, volume and robotic mobility. Specific power (mW/kg) and volumetric specific power (mW/cm3) characteristics of various design configurations will be presented and key conceptual design tradeoffs will be discussed. Hot- and cold-side thermal interfaces required to meet power and mass goals and associated design sensitivities will also be discussed. RHU / TE systems must overcome critical design challenges to survive high-g loadings in some robotic applications and we will examine the mass impacts required to satisfy various dynamic loading environments up to 10,000 gs. Power can be generated for a minimum of 30 years or more using plutonium-238 dioxide heat sources (given that Pu-238 has an 87.7 year half-life) with some reduction in power as the heat source naturally degrades.