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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Monitoring Human Performance on Future Deep Space Missions Abstract

NASA and the commercial spacecraft community are working diligently to put the first woman on the moon in the 2024 timeframe. At the same time, NASA researchers are thinking about how to solve the even larger challenges that future deep space missions will bring. Space travel itself is difficult, but astronauts on deep space missions will face obstacles and unknowns never before experienced. In addition to the altered gravity and hostile/closed environment of a spacecraft, deep space crews will face increased radiation, isolation, and distance from Earth. During Extravehicular Activity (EVA, or “spacewalk”) operations, crew will experience increased physical and cognitive workload due to extended types, frequencies and durations of tasks performed on exploration missions in partial gravity environments. All of these stressors will impact crew physical and mental health and performance in difficult-to-anticipate ways. Crew autonomy may be one of the biggest challenges faced. Communication delays and blackouts will occur, and in those situations, the crew may not have access to the Mission Control Center (MCC). They may be forced to be solely dependent on each other and the available information onboard to stay alive, healthy, and achieve the mission. The only conceivable way to meet the challenges of Earth independence is to enable the crew to monitor their own health and performance -- preferably unobtrusively as they perform their duties. Technologies and techniques must be developed to aid the crew in these assessments. A deep space mission is expected to have relatively short periods of high cognitive demand, stress, and fatigue, alongside potentially long periods of cognitive underload during the transit, where boredom, loneliness, and depression can set in. Both ends of this spectrum are dangerous. Crew must be made aware when their task performance drops significantly, when their cognitive workload is too high, when they have lost situation awareness, or when they are too stressed or too fatigued to perform well. They must be able to identify these risks, and then mitigate them with countermeasures available onboard. A number of self-monitoring technologies are presently being explored by NASA to advance crew state determination capabilities. These range from real-time, physiological workload and situation awareness assessments, to crew health measurements determining physical and mental fitness for duty, to task performance metrics such as suit resource expenditures. For EVA tasks during surface exploration missions, biomedical information such as metabolic rate may be provided to crewmembers for situational awareness related to task performance efficiency. In addition, translation distances, hydration, nutrition, inspired CO2 exposure and other consumables usage rates may be useful input metrics for modeling individualized performance during tasks to inform crew or provide estimates of work efficiency. Oculomotor metrics such as gaze dwell time, pupilometry, and eye tracking collected in advanced helmet mounted displays could potentially be used to characterize crew situation awareness. This paper highlights some of these projects, and provides broader discussion about the need for advanced monitoring and smart technologies, as NASA takes the leap into the next generation of space exploration.

Kritina Holden↗
NASA NTRS2013

Dawn's operations in cruise from Vesta to Ceres

On 5 September 2012, Dawn concluded its successful exploration of Vesta, the second most massive object in the main asteroid belt. The spacecraft departed after 14 months in orbit and is now using its ion propulsion system to travel to dwarf planet Ceres, the most massive main-belt asteroid. The principal activity now is thrusting with the ion propulsion system to provide the 3.3 km/s required to rendezvous with Ceres early in 2015. Because two of the four reaction wheels have experienced faults and are likely unrecoverable, a substantial effort has been invested in preparing for Ceres operations with alternate attitude control methods. The project has engaged in an intensive campaign to reduce hydrazine expenditures, which has resulted in a significant increase in the hydrazine expected to be available for Ceres. Based on this work, studies provide good confidence that the required activities at Ceres can be completed. This paper describes post-Vesta operations, including measures taken to conserve hydrazine as well as other preparations for Ceres.

Mase, Robert A.↗
NASA NTRSDate not supplied

The Effective Use of Metrics in Space Life Support System Trade-Offs

Engineering metrics are useful in space life support technology selection, but they must be carefully used. Metrics are only part of a complete system trade-off. Metrics do harm if they cause neglect of other important technical, organizational, or intuitive decision factors. Two metrics have damaged space life support, closure and Equivalent Systems Mass (ESM). Closure measures the fraction of the required system inputs that are produced by recycling system outputs. Increasing closure produces diminishing returns and becomes increasingly expensive. Increasing closure does not directly contribute to providing better life support. ESM measures the total launch mass required to provide life support. ESM includes the mass of the system hardware and of its power, cooling, pressurized volume, spares, and logistics. ESM predicts launch costs, but recently launch costs have been reduced by a factor of 20 or more. System development cost for space hardware is often much greater than launch cost. The past nearly exclusive use of ESM has led to the neglect of Life Cycle Cost (LCC), reliability, cost, and the other engineering factors. Closure and ESM have misguided space life support technology selection for more than twenty years and have adversely affected the expenditure of 100’s of millions of dollars. Metrics can be effectively used three ways in space life support technology selection: 1. A small set of key engineering metrics for preliminary screening. 2. A full set of engineering to guide technical selection. 3. Combining engineering metrics with organizational, political, and intuitive decision factors to understand technology selection. The past emphasis on closure and ESM served to support recycling life support over resupply and built on the intuitive appeal of a human ecosystem in space.

Harry W. Jones↗
NASA NTRS2021

Tonlé Sap Food Security and Agriculture II: Evaluating Changes in Ecosystem Vitality and Freshwater Healthin the Tonlé Sap Basin using Remotely Sensed Data

The Tonlé Sap Lake and river basin in central Cambodia provide critical ecosystem services to the region, including fisheries, agricultural irrigation, hydropower, and biodiverse habitats. Deforestation, increased pumping for farming, and effects of climate change such as droughts and forest fires threaten the health of the lake and food security in the region. This project built upon the previous term through a partnership with Conservation International (CI), the Cambodian Ministry of Water Resources and Meteorology, and the Tonlé Sap Authority to assess ecosystem vitality and implement CI’s Freshwater Health Index (FHI) tool, in an effort to prioritize resource expenditure and highlight areas of concern. Due to the COVID-19 pandemic and related travel restrictions, partners had not been able to readily collect in situ data for the past year, which make up the majority of FHI inputs. To help fill this data gap, we developed a methodology for using Gravity Recovery and Climate Experiment (GRACE) satellite data to calculate groundwater storage depletion, and a Python Application Programming Interface for processing and formatting remotely-sensed data for the Soil and Water Assessment Tool (SWAT) model. We then used SWAT to model nutrient flows and of phosphorous, nitrogen and suspended sediments amounts in the basin from October 2000 to December 2020. These outputs served as inputs for the FHI and provided policy makers with robust monitoring information to aid decision-making in the area and safeguard the lake’s vital fisheries and biodiversity.

Justine Spore↗
NASA NTRSDate not supplied

Optimal Angle of Attack Control for Aerocapture Maneuvers

Recent investigations of aerocapture maneuvers have considered direct force control as a promising alternative to bank angle control. By modulating the angle of attack and sideslip angle independently, the longitudinal and lateral channels can be decoupled and thus solved separately. However, the optimal angle of attack profile for minimizing post-atmospheric propellant expenditure was previously unknown. This research applies principles of optimal control theory to numerically solve for the optimal angle of attack profile for control of the longitudinal channel. Direct methods are first employed to discretize the angle of attack profile and show that an optimal solution follows a nearly bang-bang (full lift up then full lift down) structure under a variety of conditions along the flight path angle corridor. To corroborate these results, indirect methods were also applied to scope the Optimal Control Problem (OCP) as a Two Point Boundary Value Problem (2P-BVP) which could then be solved numerically. The indirect optimization results aligned closely with the direct results, providing further evidence that a bang-bang structure provides a good approximation for the optimal angle of attack profile for aerocapture maneuvers using direct force control.

aerocapture↗
NASA NTRS2021

Temporal and Spatial Distribution of Health, Labor, and Crop Benefits of Climate Change Mitigation in the United States

Societal benefits from climate change mitigation accrue via multiple pathways. We examine the US impacts of emission changes on several factors that are affected by both climate and air quality responses. Nationwide benefits through midcentury stem primarily from air quality improvements, which are realized rapidly, and include human health, labor productivity, and crop yield benefits. Benefits from reduced heat exposure become large around 2060, thereafter often dominating over those from improved air quality. Monetized benefits are in the tens of trillions of dollars for avoided deaths and tens of billions for labor productivity and crop yield increases and reduced hospital expenditures. Total monetized benefits this century are dominated by health and are much larger than in previous analyses due to improved understanding of the human health impacts of exposure to both heat and air pollution. Benefit–cost ratios are therefore much larger than in prior studies, especially those that neglected clean air benefits. Specifically, benefits from clean air exceed costs in the first decade, whereas benefits from climate alone exceed costs in the latter half of the century. Furthermore, monetized US benefits largely stem from US emissions reductions. Increased emphasis on the localized, near-term air quality–related impacts would better align policies with societal benefits and, by reducing the mismatch between perception of climate as a risk distant in space and time and the need for rapid action to mitigate long-term climate change, might help increase acceptance of mitigation policies.

climate change↗
NASA NTRSDate not supplied

Going South: Warnings from the Largest Project Engineering Failure in Modern History

NASA’s successful conduct of the Apollo Program greatly enhanced the prestige of the United States and remains broadly accepted as America’s gift “for all Mankind.” NASA’s Artemis Program to return humanity to the Moon promises to again reveal America’s leadership in this field. In preparation for the initiation of Artemis and its predecessor project Constellation, NASA thoroughly examined space program precedents. There remains, however, another relevant precedent which has not been examined in this context. Though this project involved technology radically different from that managed by NASA, its scope and environment in many ways parallel NASA’s large programs. This project was initiated by a private sector team that had, ten years before, successfully completed an effort that, at a cost of $275 billion (in 2021 USD), had stimulated new technology, had brought economic growth, had established their country as the world leader in engineering innovation, and, though it was a commercial success, had been broadly accepted as their nation’s gift “to all Mankind.” The new project was inspired by popular belief that private capital could again be marshalled to enhance national prestige and make yet another major contribution to the progress of Humanity. This new effort was predicted to require eight years and $258 billion. However, after the passage of nine years, achievement of only 45% complete on the baseline design, and expenditures 96% beyond the baseline cost, the project collapsed amid bankruptcy, political scandal, and criminal prosecution. While the private sector team that carried out this project was exceptionally well educated and experienced in the field, their efforts resulted in what remains (in terms of the money wasted) the largest project engineering failure in modern history. This paper examines what went wrong.

Project Management↗
NASA NTRS2022

Exploring the Clouds of Venus: Science Driven Aerobot Missions to Our Sister Planet

Venus is essential to our understanding of the evolution and habitability of Earth-size planets throughout the galaxy. The selection of the VERITAS, EnVision, and DAVINCI missions by NASA and ESA in June 2021 is an important step in advancing the science. However, addressing many of the most challenging questions will require in situ platforms that can operate in the Venus environment for extended periods in order to capture the full complexity of our sister planet. Aerobots are aerial vehicles that exploit buoyancy to achieve long-duration operation in the Venus cloud layer where environmental conditions are comparatively benign. Buoyancy control, explained in more detail in a companion paper at this conference, allows aerobots to change altitude with little energy expenditure enabling new scientific measurement opportunities. These include atmospheric chemistry, dynamics, geophysical measurements of the crust and interior and geological investigations enabled by high resolution surface imaging. One aspect to our approach to defining missions that fit within the resource constraints of competitive missions is keeping the scale small. Today’s science-driven appetite for sophisticated measurements and large volumes of data is driving size upwards but advances in technology can enable aerobots that can be delivered to Venus at manageable costs. The other aspect is supporting the aerobot at Venus with orbiters providing data relay, localization and synergistic science. The recently selected orbiters, equipped with low-cost proximity relay systems routinely used at Mars may obviate the need for dedicated orbiters thereby enabling Discovery mission candidates. Four aerobot mission concepts have been defined which fit comfortably within the current New Frontiers (NF) cost cap ($900M in $FY22). One of these concepts would also be a candidate for a Discovery mission if that cost cap ($500M in $FY19) were raised. Raising the NF cost cap would enable more capable aerobot missions combining both altitude control with synergistic orbital observations. Investigations of surface geology at high resolution with subcloud NIR nightside imaging and dropsondes on the dayside of Venus could also benefit from collaborations with foreign contributions.

"O'Rourke, Joseph"↗
NASA NTRSDate not supplied

Teal Cycle Ergometer Vibration Isolation and Stabilization System Human-in-the-Loop Ground Evaluation for Long-Duration Spaceflight

Purpose: To counter the deleterious effects of weightlessness on the cardiopulmonary system, astronauts living on the International Space Station exercise on a variety of countermeasure equipment including the Cycle Ergometer Vibration Isolation and Stabilization System (CEVIS). Operational since 2001, the onboard CEVIS will be replaced by a new model, known as Teal CEVIS (TC). As a part of ground evaluation, TC hardware underwent human-in-the-loop (HITL) testing to verify the TC hardware produces workloads that elicit physiologic responses comparable to a laboratory cycle ergometer (LAB). Methods: Seven subjects (5 M/2 F) performed submaximal cycle ergometer testing with indirect calorimetry measures on TC and LAB on separate test days. Testing consisted of graded 30 watt increases in workload until subjects reached 85% of age-predicted max heart rate (HR). Exercise outcomes included rate of oxygen uptake (VO2; liters/min), rate of energy expenditure (REE; kcal/min), and HR (beats/min). Linear mixed models (LMM) were fitted to compare VO2, REE, and HR responses between devices across power outputs with fixed effects for power (P) and device (D) and with random effects for subject. LMM effect coefficients (β), std errors (SE), pseudo-partial R2 of effects (pR2), and model likelihood ratio statistics (χ2, Pr(> chisq); α<.05) are provided. Results: LMM main effects for P and D were observed for VO2 (βp=.0107, SE = .0002, pR2=0.97; βd = -0.075, SE = 0.019, pR2=0.14; χ2(1)= 13.57, p<.001), such that VO2 was higher across stages on TC. Main effects of P and D were observed for REE (βp= .0586, SE = 0.001, pR2= 0.97; βd = -0.33208, SE = 0.099, pR2= 0.056; χ2(1)=10.481, p < .01), such that REE was higher across power outputs on TC. A P x D interaction was observed for HR, along with main effects for P and D (βp x d =-0.048, SE = 0.02, pR2=0.048; βp= 0.42, SE = 0.016, pR2=0.87; χ2(1) = 5.398, p = 0.02), such that higher workloads elicited a greater difference in HR between devices. Conclusions: HITL results show, TC elicits greater physiologic responses across power outputs compared to LAB. However, pR2 for device effects show small differences between devices. Therefore, TC can be expected to provide appropriate physiological stimulus across workloads and be considered a reliable tool to mitigate the effects of weightlessness.

Cycle Ergometer Vibration and Isolation System↗
NASA NTRSDate not supplied

How Can We Efficiently Build A Spacecraft That Has Longevity? Experiences From the GSFC Perspective to Inform Lunar Exploration and Science Orbiter’s Architecture

Recent successes in NASA planetary science missions has shown that long-lived missions can yield significant science return. These missions, despite their longevity, were not planned to operate beyond their deign life. For example, the Lunar Reconnaissance Orbiter has a design life of 2-3 years, and yet we are entering its 14th year on orbit. Spacecraft longevity in practice has been related to: 1) mission class; 2) did we test it long enough and resolve all the anomalies to be beyond the early failure curve; 3) consumables budgets, and 4) how components are de-signed and tested. Mission class has been perceived as one of the primary ways to drive longevity. But higher mission class is a significant cost and mission driver. Parts selection only from the limited military standard parts and extensive parts qualification adds to development time and cost. Largely redundant (often erroneously interpreted as fully redundant) adds to launch mass and increases testing complexity (which may reduce the amount of testing in the nominal con-figuration). Lower Risk Posture (reflected in a higher mission class) drives significant additional processes and quality assurance analyses. Higher mission class also drives significantly greater sparing and life testing costs. This discussion focuses on whether this is indeed the best way to achieve longevity efficiently or whether there are more efficient ways to achieve longevity. Empirical evidence shows that lower mission classes that implement effective risk reduction and selective redundancy generally results in long life at a lower Spacecraft bus cost. By evaluating redundancy careful-ly, spacecraft cost can be lowered which can enable a more capable payload. Risk of the mission is highly dependent on the complexity of the mission and is only loosely dependent on Class of Mission. High complexity missions can have many single point failures and require the development of new technology, while lower class mission can have lower risk by baselining or incorporating: (selective) redundancy, fault-tolerant design, design for minimum risk, ability to reset, and/or design for graceful degradation. The team met with Goddard Space Flight Center Space Systems Mission Operations leaders to discuss which avionics have proven in flight to be the most reliable and which have had lifetime issues. The paper proposes a list of components to focus on for redundancy for a long-lived lunar mission. Reliability numbers are presented for both single string and dual string missions. The history of life-time performance versus planned mission life according to mission class is presented. A mission with well thought out selective redundancy and effective on the ground test program, can be expected to last well beyond its mission lifetime and provided enhanced return for the community. This approach minimizes project expenditures that do not retire significant risk and allows the project to focus risk mitigation efforts on those risks that will have a significant likelihood of threatening mission success. This is aided by keeping the amount of technology maturation and mission complexity low, while focusing effort on ensuring all component stress-ing parameters well within the bounds of their capabilities.

Lessons Learned↗
NASA NTRS2022

Towards Finding Energy Efficient Paths for Hybrid Airships in the Atmosphere of Venus

This paper presents a solution to the motion planning problem for an autonomous airship under superrotation winds of the Venusian atmosphere. The airship uses both buoyancy and aerodynamic lift to control its altitude. In addition, solar panels distributed over the aircraft provide energy to the propellers and allow for battery recharging. Our approach uses a sampling-based planner that relies on Dubins’ Airplane paths deformed under the influence of the winds to create a tree of kinematically feasible trajectories. We use the battery state to prune energetically unfeasible trajectories and we propose a cost function that accounts for the energy expenditure of the propulsive system and that considers battery charging by using the Economics notion of opportunity cost. The method is illustrated through a series of simulations that show how the vehicle takes longer and high-altitude paths to minimize the use of energy and favor battery recharge. Our results also show that naive trajectories are not feasible in terms of energy, justifying the need for more efficient solutions.

Bernardo Martinez R. Jr↗
NASA NTRSDate not supplied

Exploration Exercise System (EES) Physiology

Exploration class missions will be required to have an exercise device that is lightweight, has a small footprint, and is capable of providing enough physical stimulus and exercise variability to be an effective countermeasure against muscle, bone, aerobic fitness, and sensorimotor loss that results from the microgravity environment. Ground studies, inflight studies, and results analyses are required to inform Moon2Mars Design Reference Missions (DRMs) and vehicle designs. This activity encompasses two related projects, an evaluation study called Zero T2 and a requirements development for an exploration treadmill (ET). Exploration class missions’ mass/power/volume restrictions have resulted in the development of exercise devices that are motorized and flywheel-based to provide both aerobic and resistive training on one platform. These devices provide a variety of full body resistance exercise options as well as rowing and cycling for aerobic exercise, but do not provide ambulatory exercise via a treadmill. Because a treadmill has been available for use on the ISS since 2001, we do not understand the efficacy of exploration exercise modalities on muscle performance, aerobic fitness, bone health, or sensorimotor performance. A retrospective study was performed to quantify the association between total exercise (including specific contributions of treadmill exercise) and functional performance upon landing. Due to the relatively small variation in treadmill usage inflight, there is a need to do a controlled study where inflight crewmembers will not use the ISS treadmill (called T2) for the duration of their flights. There will be 3 arms to the Zero T2 study: 1) participants use all currently available exercise platforms aboard ISS (control group), 2) participants use only ARED and CEVIS, and 3) participants use only European Enhanced Exploration Device (E4D). (Please see the TechPort Entry for Exploration Exercise System Development for further detail on the E4D.) This study started in Oct 2020 and will continue through Sep 2027. In a parallel effort, a team will be developing requirements for an exploration treadmill. This project will be broken into two phases. Phase 1 will develop and implement energy prediction models based on available in-flight exercise data to quantify energy expenditure during 0g treadmill running. Phase 2 will then use the available biomechanical and metabolic evidence from Phase 1 to determine the hardware specification requirements essential to providing the desired exercise stimulus. Subject Matter Experts (SMEs) will then leverage the Standardized Process for Evaluating Exercise Devices (SPEED) developed by the team to 1) assess available technologies for candidate treadmills which meet defined requirements, 2) perform hands-on evaluations of top candidates, 3) provide evaluation outcomes and recommendations to developers. This project will begin in 2025 and continue through Sep 2030.

Kent Lawrence Kalogera↗
NASA NTRSDate not supplied

Control of the Lunar Reconnaissance Orbiter Reaction Wheel Angular Momentum Using Attitude Slews

The Lunar Reconnaissance Orbiter (LRO) makes use of four Reaction Wheel Assemblies (RWA) for the purpose of adjusting and maintaining the spacecraft attitude. Reduction of RWA angular momentum through the use of propulsive momentum unloads is the principal source of fuel use. Nominally, LRO maintains a nadir orientation but frequently slews off-nadir for science observations. Off-nadir attitude slews can reduce RWA angular momentum by changing the direction of the external torques in the spacecraft body frame. Control of RWA angular momentum using momentum attitude slews has the potential to significantly reduce fuel expenditure. The momentum slew planning process requires careful evaluation of spacecraft constraints, ground constraints, and science observations. Momentum slews are projected to extend LRO fuel lifetime by several years.

Operations↗
NASA NTRS2025

Assessing Commercialization Strategies for Evolving Network Demand (ASCEND) in the NASA Space Communications and Navigation (SCaN) Program

What will NASA’s future communications demand and expenditure look like, in a paradigm where space policy encourages maximum private sector involvement? In this paper we consider this question, as NASA moves towards commercial procurement for Direct-To-Earth and Space Relay communication services. We develop a new quantitative Techno-Economic Assessment (TEA) model capable of evaluating the incremental cost over time to NASA of utilizing commercial communication services, for different mission and market scenarios. We find that current and future NASA demand could be viably procured from commercial services, with the potential to reduce cost using non-exclusive networks and the sharing of fixed costs. However, there is a key trade-off identified between maximizing economies of scale benefits and ensuring sufficient competition between communication providers to avoid collusion and excessive pricing. For example, procuring from 1-2 providers would maximize scale economies, whereas procuring from 5-6 providers would maximize competition. Given this context, it would be prudent to seek to award service contracts for 3-4 providers to optimize economies of scale benefits, while mitigating possible market collusion. These recommendations enable NASA to successfully achieve its scientific mission over the next decade, while managing limited financial and networking resources.

NSN↗
DOE OSTI2012

Spiral Development for Safeguards Instrumentation

Safeguards instrumentation is highly specialized, so a common approach in the US has been to develop initial prototypes for performance, operability and security within the US National Laboratories for the IAEA and then seek one or more commercial partners. Transfer of technology from US National Laboratories is a legal requirement for products that have the potential for mass production. Other important objectives include minimizing time to deployment and lifecycle cost, and optimizing product maintainability, sustainability and manufacturability. Unfortunately, the deployment of systems developed via this model has sometimes been seriously delayed or never adopted because of the difficulty of optimizing the significant parameters of the process between the public and private sectors. The authors suggest that forming an R&D partnership between a research laboratory and a commercial company much earlier in the process would provide significant advantages. The present US practice leads to unnecessary expenditures during the early R&D phase since many decisions are made based on research needs that are counterproductive for commercialization and manufacturability. If the ultimate goal of the project is to produce a reliable and cost effective commercial product, the commercial input is needed early and often. The new “model” of developing systems in a closer collaboration with the private sector, in a spiral “Commercialization by Design” approach, should also limit the long term financial mortgages that Member States frequently experience with respect to safeguards instrumentation development using the present process. As a concrete example, the potential for incorporating Wire Integrity Verification Technology into the iCobra Reader System is discussed.

Koskelo, M.↗
DOE OSTI2013

Technology Prioritization: Transforming the U.S. Building Stock to Embrace Energy Efficiency

The U.S. Buildings sector is responsible for about 40% of the national energy expenditures. This is due in part to wasteful use of resources and limited considerations made for energy efficiency during the design and retrofit phases. Recent studies have indicated the potential for up to 30-50% energy savings in the U.S. buildings sector using currently available technologies. This paper discusses efforts to accelerate the transformation in the U.S. building energy efficiency sector using a new technology prioritization framework. The underlying analysis examines building energy use micro segments using the Energy Information Administration Annual Energy Outlook and other publically available information. The tool includes a stock-and-flow model to track stock vintage and efficiency levels with time. The tool can be used to investigate energy efficiency measures under a variety of scenarios and has a built-in energy accounting framework to prevent double counting of energy savings within any given portfolio. This tool is developed to inform decision making and estimate long term potential energy savings for different market adoption scenarios.

energy efficiency↗
DOE OSTI2014

Magnetically coupled system for mixing

The invention provides a mixing system comprising a magnetically coupled drive system and a foil for cultivating algae, or cyanobacteria, in an open or enclosed vessel. The invention provides effective mixing, low energy usage, low capital expenditure, and ease of drive system component maintenance while maintaining the integrity of a sealed mixing vessel.

47 OTHER INSTRUMENTATION↗