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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Smart Charging for Electric Ride-Hailing Vehicles using Renewables: A San Francisco Case Study

Charging large fleets of electric ride-hailing vehicles (ERVs) is a complex matter that could serve different objectives: lower carbon dioxide emissions, lower monetary expenditures, or maximize solar photovoltaics (PV) energy consumption. Currently, it is unclear how each of those objectives could impact the business and performance of a ride-hailing fleet. In order to fill this gap, this article employs a dynamic transportation model: a smart charging simulation that combines agent-based, discrete-event, and system dynamic modelling by comparing the above-mentioned objectives in separate scenarios. The results show that each scenario successfully manages to shift between 34% and 87% of all load to hours of the day when the objectives of those scenarios are met. Therefore, in comparison to the baseline, smart charging can save between 5% and 26% of monthly emissions and between 4% and 57% of monthly expenditures. The solar PV scenario, however, results in the highest savings, while ensuring profitable economics via net metering in the short- as well as long term. Finally, the sensitivity analysis points to important trade-offs between several fleet performance metrics. The article concludes by giving business and policy recommendations for maximising the economic, energy and environmental efficiency of large ERV fleets.

ADVANCED PROPULSION SYSTEMS,SOLAR ENERGY↗
DOE OSTI2023

End-Use Savings Shapes Measure Documentation: Variable Refrigerant Flow with Heat Recovery and Dedicated Outdoor Air System

Building on the successfully completed effort to calibrate and validate the U.S. Department of Energy's ResStock™ and ComStock™ models over the past 3 years, the objective of this work is to produce national data sets that empower analysts working for federal, state, utility, city, and manufacturer stakeholders to answer a broad range of analysis questions. The goal of this work is to develop energy efficiency, electrification, and demand flexibility end-use load shapes (electricity, gas, propane, or fuel oil) that cover a majority of the high-impact, market-ready (or nearly market-ready) measures. "Measures" refers to energy efficiency variables that can be applied to buildings during modeling. An end-use savings shape is the difference in energy consumption between a baseline building and a building with an energy efficiency, electrification, or demand flexibility measure applied. It results in a time-series profile that is broken down by end use and fuel (electricity or on-site gas, propane, or fuel oil use) at each time step. ComStock is a highly granular, bottom-up model that uses multiple data sources, statistical sampling methods, and advanced building energy simulations to estimate the annual subhourly energy consumption of the commercial building stock across the United States. The baseline model intends to represent the U.S. commercial building stock as it existed in 2018. The methodology and results of the baseline model are discussed in the final technical report of the End-Use Load Profiles project. This documentation focuses on a single heating, ventilation, and air-conditioning (HVAC) end-use savings shape measure - a variable refrigerant flow with heat recovery (VRF HR) heating and cooling system coupled with a dedicated outdoor air system (DOAS) for ventilation. This measure replaces existing multi-zone variable air volume (VAV) systems or single-zone rooftop units (RTU) with a VRF HR system coupled with a DOAS that includes an energy/heat recovery ventilator (E/HRV). The measure covers 53% of exisiting building stock's floor area and is not applicable to HVAC system types using district heating or cooling or buildings/spaces that include high-ventilation spaces such as kitchens where the amount of exhaust air is large. A DOAS with E/HRV is used to provide required outdoor ventilation air to spaces since ventilation air is generally not supplied by a VRF HR system. An exhaust air energy recovery ventilator (ERV ) with sensible and latent heat exchange is added to humid climate zones while a heat recovery ventilator (HRV ) with sensible only exchange is added to drier climate zones. The ERV is modeled as a fixed membrane plate counterflow heat exchanger, while the HRV is modeled as a sensible-only fixed aluminum plate counterflow heat exchanger. Both systems include a bypass (for temperature control and economizer lockout) and minimum exhaust temperature control for frost prevention.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1989

Avionics architecture studies for the entry research vehicle

This report is the culmination of a year-long investigation of the avionics architecture for NASA's Entry Research Vehicle (ERV). The Entry Research Vehicle is conceived to be an unmanned, autonomous spacecraft to be deployed from the Shuttle. It will perform various aerodynamic and propulsive maneuvers in orbit and land at Edwards AFB after a 5 to 10 hour mission. The design and analysis of the vehicle's avionics architecture are detailed here. The architecture consists of a central triply redundant ultra-reliable fault tolerant processor attached to three replicated and distributed MIL-STD-1553 buses for input and output. The reliability analysis is detailed here. The architecture was found to be sufficiently reliable for the ERV mission plan.

Dzwonczyk, M. J.↗
NASA NTRS1989

Mars Rover Sample Return ascent, rendezvous, and return to earth

Ascent, rendezvous and earth return are three operational mission sequences in the sample return phase of the Mars Rover Sample Return (MRSR) mission. In the conduct of the current study, several vehicles have been identified to enable the sample return phase of the mission. These elements are the Mars Ascent Vehicle (MAV), the Earth Return Vehicle (ERV), the rendezvous and docking module (RDM), and the sample return capsule (SRC). The sample return elements, when combined with other elements performing the launch and delivery functions, form the basis of the MRSR system. This paper summarizes the significant mission aspects of the sample return phase, describes the Mars ascent and earth return scenario, illustrates the conceptual designs developed for the MAV, ERV, RDM, and SRC, and discusses the results of significant trade studies conducted.

Lance, Nick↗
NASA NTRS1992

Ventilation-perfusion relationships in the lung during head-out water immersion

Mechanisms of altered pulmonary gas exchange during water immersion were studied in 12 normal males: 6 young (aged 20-29) and 6 older (aged 40-45). It is concluded that, in young subjects with closing volume (CV) less than expiratory reserve volume (ERV), gas exchange was enhanced during immersion, because normal ventilation-perfusion relations were preserved, and by mass balance, the ventilation/O2 uptake changes elevated arterial P(O2). In older males with CV greater than ERV and 52 percent of tidal volume below CV, immersion-induced airways closure during tidal breathing was associated with minimally increased shunt that did not significantly impair gas exchange. It is suggested that airways closure of this degree is of little importance to gas exchange.

Derion, Toniann↗
NASA NTRS1992

Project Minerva: A low cost manned Mars mission based on indigenous propellant production

Project Minerva is a low-cost manned Mars mission designed to deliver a crew of four to the Martian surface using only two sets of two launches from the Kennedy Space Center. Key concepts which make this mission realizable are the use of near-term technologies and in-situ propellant production, following the scenario originally proposed by R. Zubrin. The first set of launches delivers two unmanned payloads into low Earth orbit (LEO): the first payload consists of an Earth Return Vehicle (ERV), a propellant production plant, and a set of robotic vehicles; the second payload consists of the trans-Mars injection (TMI) upper stage. In LEO, the two payloads are docked and the configuration is injected into a Mars transfer orbit. The landing on Mars is performed with the aid of multiple aerobraking maneuvers. On the Martian surface, the propellant production plant uses a Sabatier/electrolysis type process to combine nine tons of hydrogen with carbon dioxide from the Martian atmosphere to produce over a hundred tons of liquid oxygen and liquid methane, which are later used as the propellants for the rover expeditions and the manned return journey of the ERV. The systems necessary for the flights to and from Mars, as well as those needed for the stay on Mars, are discussed. These systems include the transfer vehicle design, life support, guidance and communications, rovers and telepresence, power generation, and propellant manufacturing. Also included are the orbital mechanics, the scientific goals, and the estimated mission costs.

Beder, David↗
NASA NTRS2002

Vehicle and Mission Design Options for the Human Exploration of Mars/Phobos Using "Bimodal" NTR and LANTR Propulsion

The nuclear thermal rocket (NTR) is one of the leading propulsion options for future human missions to Mars because of its high specific impulse (lsp~850-1000 s) capability and its attractive engine thrust-to-weight ratio (~3-10). To stay within the available mass and payload volume limits of a “Magnum” heavy lift vehicle, a high performance propulsion system is required for trans-Mars injection (TMI). An expendable TMI stage, powered by three 15 thousand pounds force (klbf) NTR engines is currently under consideration by NASA for its Design Reference Mission (DRM). However, because of the miniscule burnup of enriched uranium-235 during the Earth departure phase (~10 grams out of 33 kilograms in each NTR core), disposal of the TMI stage and its engines after a single use is a costly and inefficient use of this high performance stage. By reconfiguring the engines for both propulsive thrust and modest power generation (referred to as “bimodal” operation), a robust, multiple burn, “power-rich” stage with propulsive Mars capture and reuse capability is possible. A family of modular “bimodal” NTR (BNTR) vehicles are described which utilize a common “core” stage powered by three 15 klbf BNTRs that produce 50 kWe of total electrical power for crew life support, an active refrigeration / reliquification system for long term, zero-boiloff liquid hydrogen (LH 2 ) storage, and high data rate communications. An innovative, spine-like “saddle truss” design connects the core stage and payload element and is open underneath to allow supplemental “in-line” propellant tanks and contingency crew consumables to be easily jettisoned to improve vehicle performance. A “modified” DRM using BNTR transfer vehicles requires fewer transportation system elements, reduces IMLEO and mission risk, and simplifies space operations. By taking the next logical step—use of the BNTR for propulsive capture of all payload elements into Mars orbit—the power available in Mars orbit grows to 150 kWe compared to 30 kWe for the DRM. Propulsive capture also eliminates the complex, higher risk aerobraking and capture maneuver which is replaced by a simpler reentry using a standardized, lower mass “aerodescent” shell. The attractiveness of the “all BNTR” option is further increased by the substitution of the lightweight, inflatable “TransHab” module in place of the heavier, hard-shell hab module. Use of TransHab introduces the potential for propulsive recovery and reuse of the BNTR / Earth return vehicle (ERV). It also allows the crew to travel to and from Mars on the same BNTR transfer vehicle thereby cutting the duration of the ERV mission in half—from ~4.7 to 2.5 years. Finally, for difficult Mars options, such as Phobos rendezvous and sample return missions, volume (not mass) constraints limit the performance of the “all LH 2 ” BNTR stage. The use of “LOX-augmented” NTR (LANTR) engines, operating at a modest oxygen-to-hydrogen mixture ratio (MR) of 0.5, helps to increase “bulk” propellant density and total thrust during the TMI burn. On all subsequent burns, the bimodal LANTR engines operate on LH 2 only (MR=0) to maximize vehicle performance while staying within the mass limits of two Magnum launches.

Nuclear thermal rocket↗
NASA NTRS2011

Propulsion Technology Development for Sample Return Missions Under NASA's ISPT Program

The In-Space Propulsion Technology (ISPT) Program was tasked in 2009 to start development of propulsion technologies that would enable future sample return missions. Sample return missions could be quite varied, from collecting and bringing back samples of comets or asteroids, to soil, rocks, or atmosphere from planets or moons. The paper will describe the ISPT Program s propulsion technology development activities relevant to future sample return missions. The sample return propulsion technology development areas for ISPT are: 1) Sample Return Propulsion (SRP), 2) Planetary Ascent Vehicles (PAV), 3) Entry Vehicle Technologies (EVT), and 4) Systems/mission analysis and tools that focuses on sample return propulsion. The Sample Return Propulsion area is subdivided into: a) Electric propulsion for sample return and low cost Discovery-class missions, b) Propulsion systems for Earth Return Vehicles (ERV) including transfer stages to the destination, and c) Low TRL advanced propulsion technologies. The SRP effort will continue work on HIVHAC thruster development in FY2011 and then transitions into developing a HIVHAC system under future Electric Propulsion for sample return (ERV and transfer stages) and low-cost missions. Previous work on the lightweight propellant-tanks will continue under advanced propulsion technologies for sample return with direct applicability to a Mars Sample Return (MSR) mission and with general applicability to all future planetary spacecraft. A major effort under the EVT area is multi-mission technologies for Earth Entry Vehicles (MMEEV), which will leverage and build upon previous work related to Earth Entry Vehicles (EEV). The major effort under the PAV area is the Mars Ascent Vehicle (MAV). The MAV is a new development area to ISPT, and builds upon and leverages the past MAV analysis and technology developments from the Mars Technology Program (MTP) and previous MSR studies.

Anderson, David J.↗
NASA NTRS2012

Status of Sample Return Propulsion Technology Development Under NASA's ISPT Program

The In-Space Propulsion Technology (ISPT) program was tasked in 2009 to start development of propulsion technologies that would enable future sample return missions. ISPT s sample return technology development areas are diverse. Sample Return Propulsion (SRP) addresses electric propulsion for sample return and low cost Discovery-class missions, propulsion systems for Earth Return Vehicles (ERV) including transfer stages to the destination, and low technology readiness level (TRL) advanced propulsion technologies. The SRP effort continues work on HIVHAC thruster development to transition into developing a Hall-effect propulsion system for sample return (ERV and transfer stages) and low-cost missions. Previous work on the lightweight propellant-tanks continues for sample return with direct applicability to a Mars Sample Return (MSR) mission with general applicability to all future planetary spacecraft. The Earth Entry Vehicle (EEV) work focuses on building a fundamental base of multi-mission technologies for Earth Entry Vehicles (MMEEV). The main focus of the Planetary Ascent Vehicles (PAV) area is technology development for the Mars Ascent Vehicle (MAV), which builds upon and leverages the past MAV analysis and technology developments from the Mars Technology Program (MTP) and previous MSR studies

Anderson, David J.↗
NASA NTRS2013

A Mars Sample Return Sample Handling System

We present a sample handling system, a subsystem of the proposed Dragon landed Mars Sample Return (MSR) mission [1], that can return to Earth orbit a significant mass of frozen Mars samples potentially consisting of: rock cores, subsurface drilled rock and ice cuttings, pebble sized rocks, and soil scoops. The sample collection, storage, retrieval and packaging assumptions and concepts in this study are applicable for the NASA's MPPG MSR mission architecture options [2]. Our study assumes a predecessor rover mission collects samples for return to Earth to address questions on: past life, climate change, water history, age dating, understanding Mars interior evolution [3], and, human safety and in-situ resource utilization. Hence the rover will have "integrated priorities for rock sampling" [3] that cover collection of subaqueous or hydrothermal sediments, low-temperature fluidaltered rocks, unaltered igneous rocks, regolith and atmosphere samples. Samples could include: drilled rock cores, alluvial and fluvial deposits, subsurface ice and soils, clays, sulfates, salts including perchlorates, aeolian deposits, and concretions. Thus samples will have a broad range of bulk densities, and require for Earth based analysis where practical: in-situ characterization, management of degradation such as perchlorate deliquescence and volatile release, and contamination management. We propose to adopt a sample container with a set of cups each with a sample from a specific location. We considered two sample cups sizes: (1) a small cup sized for samples matching those submitted to in-situ characterization instruments, and, (2) a larger cup for 100 mm rock cores [4] and pebble sized rocks, thus providing diverse samples and optimizing the MSR sample mass payload fraction for a given payload volume. We minimize sample degradation by keeping them frozen in the MSR payload sample canister using Peltier chip cooling. The cups are sealed by interference fitted heat activated memory alloy caps [5] if the heating does not affect the sample, or by crimping caps similar to bottle capping. We prefer cap sealing surfaces be external to the cup rim to prevent sample dust inside the cups interfering with sealing, or, contamination of the sample by Teflon seal elements (if adopted). Finally the sample collection rover, or a Fetch rover, selects cups with best choice samples and loads them into a sample tray, before delivering it to the Earth Return Vehicle (ERV) in the MSR Dragon capsule as described in [1] (Fig 1). This ensures best use of the MSR payload mass allowance. A 3 meter long jointed robot arm is extended from the Dragon capsule's crew hatch, retrieves the sample tray and inserts it into the sample canister payload located on the ERV stage. The robot arm has capacity to obtain grab samples in the event of a rover failure. The sample canister has a robot arm capture casting to enable capture by crewed or robot spacecraft when it returns to Earth orbit

Wilson, David↗
DOE OSTI2021

Integrated heat and energy recovery ventilator system

A heat recovery ventilator (HRV) and/or energy recovery ventilator (ERV) that integrates with a residential capacity air handling unit (AHU) is embodied in a small footprint HRV or ERV unit that connects directly to the return side of an AHU and to outdoor air inlet and exhaust ducts. The ventilator includes a control system incorporating a processor and sensors that control the operation of the system to provide desired ventilation flow rates under varying conditions.

Puttagunta, Srikanth↗
DOE OSTI2017

Development of Smart Ventilation Control Algorithms for Humidity Control in High-Performance Homes in Humid U.S. Climates

Past field research and simulation studies have shown that high performance homes experience elevated indoor humidity levels for substantial portions of the year in humid climates. This is largely the result of lower sensible cooling loads, which reduces the moisture removed by the cooling system. These elevated humidity levels lead to concerns about occupant comfort, health and building durability. Use of mechanical ventilation at rates specified in ASHRAE Standard 62.2-2013 are often cited as an additional contributor to humidity problems in these homes. Past research has explored solutions, including supplemental dehumidification, cooling system operational enhancements and ventilation system design (e.g., ERV, supply, exhaust, etc.). This project’s goal is to develop and demonstrate (through simulations) smart ventilation strategies that can contribute to humidity control in high performance homes. These strategies must maintain IAQ via equivalence with ASHRAE Standard 62.2-2013. To be acceptable they must not result in excessive energy use. Smart controls will be compared with dehumidifier energy and moisture performance. This work explores the development and performance of smart algorithms for control of mechanical ventilation systems, with the objective of reducing high humidity in modern high performance residences. Simulations of DOE Zero-Energy Ready homes were performed using the REGCAP simulation tool. Control strategies were developed and tested using the Residential Integrated Ventilation (RIVEC) controller, which tracks pollutant exposure in real-time and controls ventilation to provide an equivalent exposure on an annual basis to homes meeting ASHRAE 62.2-2013. RIVEC is used to increase or decrease the real-time ventilation rate to reduce moisture transport into the home or increase moisture removal. This approach was implemented for no-, one- and two-sensor strategies, paired with a variety of control approaches in six humid climates (Miami, Orlando, Houston, Charleston, Memphis and Baltimore). The control options were compared to a baseline system that supplies outdoor air to a central forced air cooling (and heating) system (CFIS) that is often used in hot humid climates. Simulations were performed with CFIS ventilation systems operating on a 33% duty-cycle, consistent with 62.2-2013. The CFIS outside airflow rates were set to 0%, 50% and 100% of 62.2-2013 requirements to explore effects of ventilation rate on indoor high humidity. These simulations were performed with and without a dehumidifier in the model. Ten control algorithms were developed and tested. Analysis of outdoor humidity patterns facilitated smart control development. It was found that outdoor humidity varies most strongly seasonally—by month of the year—and that all locations follow the similar pattern of much higher humidity during summer. Daily and hourly variations in outdoor humidity were found to be progressively smaller than the monthly seasonal variation. Patterns in hourly humidity are driven by diurnal daily patterns, so they were predictable but small, and were unlikely to provide much control benefit. Variation in outdoor humidity between days was larger, but unpredictable, except by much more complex climate models. We determined that no-sensor strategies might be able to take advantage of seasonal patterns in humidity, but that real-time smart controls were required to capture variation between days. Sensor-based approaches are also required to respond dynamically to indoor conditions and variations not considered in our analysis. All smart controls face trade-offs between sensor accuracy, cost, complexity and robustness.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2024

End-Use Savings Shapes Measure Documentation: Demand Control Ventilation

This documentation focuses on a single end-use savings shape measure - Demand Control Ventilation (DCV). DCV can save energy by reducing the rate at which outdoor air (OA) is delivered during periods of less-than-design occupancy. This measure will enable DCV for air loops using applicable HVAC system types (all except dedicated outdoor air systems [DOAS], packaged systems, or that have an energy recovery ventilator [ERV]) and serving applicable space types (all except kitchens, dining areas, patient spaces, mechanical rooms, stairwells and corridors, or high exhaust space types) using model occupancy schedules to control the DCV. The measure is applicable to 72.7% of the stock floor area. As office buildings outside of California in ComStock are modeled using a single, whole-building space type, DCV is not applied to these building types. The DCV measure demonstrates 2.6% total site energy savings (119 trillion British thermal units [TBtu]) for the U.S. commercial building stock modeled in ComStock.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2026

Heat Pumps and Energy Recovering Ventilators in Northern Alaska

The intended purpose of this project was to bring alternative heat and ventilation options to rural communities off the road system in Northwestern Alaska. Most of the residents of these communities are reliant upon kerosene or other fossil fuels to provide heat to their homes. Our intention was to offer an alternative to using those sources by providing heat pumps to 45 homes in the communities of Elim and Koyuk. When projecting energy use for these units based on the fuel prices at the time, it was discovered that energy costs for heat pumps would equal or slightly exceed the costs of existing kerosene units. Secondly, as part of our E&l grant we installed 45 energy recovery ventilators (ERV’s) in those same homes. This was important given our experience over the years with moisture and comfort issues in most homes within this region. Exhaust-only systems are rarely used due to the high heating costs. Additionally, exhaust-only systems have a potential risk of back drafting due to tight building construction. Balanced systems like this eliminate that risk while improving indoor air quality. Another benefit to these types of systems is the fact that they help transfer heat from a single heat source equally throughout the building. Our overall goal was to offer new technology options to improve these structures and the families that reside in them where, given their location and extreme seasonal temperature swings, they have historically never been offered.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1987

An Adaptive Numeric Predictor-corrector Guidance Algorithm for Atmospheric Entry Vehicles

An adaptive numeric predictor-corrector guidance is developed for atmospheric entry vehicles which utilize lift to achieve maximum footprint capability. Applicability of the guidance design to vehicles with a wide range of performance capabilities is desired so as to reduce the need for algorithm redesign with each new vehicle. Adaptability is desired to minimize mission-specific analysis and planning. The guidance algorithm motivation and design are presented. Performance is assessed for application of the algorithm to the NASA Entry Research Vehicle (ERV). The dispersions the guidance must be designed to handle are presented. The achievable operational footprint for expected worst-case dispersions is presented. The algorithm performs excellently for the expected dispersions and captures most of the achievable footprint.

Spratlin, Kenneth Milton↗
NASA NTRS1986

The tethered satellite system for low density aerothermodynamics studies

The feasibility of the operation of the Tethered Satellite System (TSS) as a continuous open wind tunnel for low-density aerothermodynamic studies (applicable to the design of hypersonic space vehicles including STARFAC, AOTV, and ERV) is considered. The Shuttle Continuous Open Wind Tunnel (SCOWT) program, for the study of the energy and momentum transfer between the tethered satellite and its environmental medium during the TSS/2 mission, is described. Instrumentation and TSS design requirements to meet SCOWT objectives are also considered. SCOWT will provide information on the gasdynamic processes occurring downstream of the bow wave standing in front of the TS, the chemistry and physics of the upper atmosphere related to satellite aerothermodynamics, and TSS's overall experimental envelope of operation.

Carlomagno, Giovanni M.↗
NASA NTRS1994

Hubble Space Telescope UV spectral observations of Io passing into eclipse

Time-resolved spectra of Io have been obtained with the Faint Object Spectrograph on the Hubble Space Telescope in January 1992 at times centered on the passage of Io into Jupiter's shadow. Two different eclipse observations covered 1100-1600 A and 2250-3300 A. In the far ultraviolet(far-UV) range, emission lines of atomic sulfur and oxygen from Io's atmosphere (similar to those previously detected with the International Ultraviolet Explorer (IUE)) have been observed from Io in sunlight, and the spatial extent of the emitting region has been resolved for the first time: this is 0.5-1 Io radii (R(sub Io)) above the surface. The emission lines are typically 1kR in brightness while Io is in sunlight, and decrease to a few hundred Rayleighs within 20 min or less of Io's passing into shadow. If the emissions are produced in Io's ionosphere, the decrease in shadow appears consistent with the collisional slowing and recombination of photoelectrons in 100-1000 s, with recombination an important quenching process if the dominant ion is molecular (i.e., SO2(+)) condensation, with the residual emission in shadow due either to plasma impact of gas above the hot volcanic calderas or electron impact on S and O. In the near-UV range, we have not detected any airglow emissions from Io's atmosphere in shadow, with the main limitation being a high level of scattered light from Jupiter. We derive a 3 sigma upper limit to the 2560 A SO emission feature of 1 KR, which is close to what is expected from electron impact on SO2 based on the obs erved brightness of the FUV S and O lines in shadow. A high signal-to-noise spectrum of Io's albedo in sunlight reveals a spectral shape similar to laboratory spectra of SO2 frost reflectivity, and the relative albedo spectrum changed as Io passed into eclipse and part of the disk was in shadow. No specific SO2 gas absorption features appear in the albedo spectrum, although there could be substantial gas absorption near 2800 A if the individual lines are narrow and saturated. Finally, we present preliminary models for the near-UV spectrum of Io as functions of SO2 frost areal coverage and SO2 gas density.

Clarke, John T.↗
NASA NTRS1998

Vehicle and Mission Design Options for the Human Exploration of Mars/Phobos Using "Bimodal" NTR and LANTR Propulsion

The nuclear thermal rocket (NTR) is one of the leading propulsion options for future human missions to Mars because of its high specific impulse (Isp-850-1000 s) capability and its attractive engine thrust-to-weight ratio (approximately equal 3-10). To stay within the available mass and payload volume limits of a "Magnum" heavy lift vehicle, a high performance propulsion system is required for trans-Mars injection (TMI). An expendable TMI stage, powered by three 15 thousand pounds force (klbf) NTR engines is currently under consideration by NASA for its Design Reference Mission (DRM). However, because of the miniscule burnup of enriched uranium-235 during the Earth departure phase (approximately 10 grams out of 33 kilograms in each NTR core), disposal of the TMI stage and its engines after a single use is a costly and inefficient use of this high performance stage. By reconfiguring the engines for both propulsive thrust and modest power generation (referred to as "bimodal" operation), a robust, multiple burn, "power-rich" stage with propulsive Mars capture and reuse capability is possible, A family of modular "bimodal" NTR (BNTR) vehicles are described which utilize a common "core" stage powered by three 15 klbf BNTRs that produce 50 kWe of total electrical power for crew life support, an active refrigeration / reliquification system for long term, "zero-boiloff" liquid hydrogen (LH 2 ) storage, and high data rate communications. An innovative, spine-like "saddle truss" design connects the core stage and payload element and is open underneath to allow supplemental "in-line" propellant tanks and contingency crew consumables to be easily jettisoned to improve vehicle performance. A "modified" DRM using BNTR transfer vehicles requires fewer transportation system elements, reduces IMLEO and mission risk, and simplifies space operations. By taking the next logical step--use of the BNTR for propulsive capture of all payload elements into Mars orbit--the power available in Mars orbit grows to 150 kWe compared to 30 kWe for the DRM. Propulsive capture also eliminates the complex, higher risk aerobraking and capture maneuver which is replaced by a simpler reentry using a standardized, lower mass "aerodescent" shell. The attractiveness of the "all BNTR" option is further increased by the substitution of the lightweight, inflatable "TransHab" module in place of the heavier, hard-shell hab module. Use of TransHab introduces the potential for propulsive recovery and reuse of the BNTR/ERV. It also allows the crew to travel to and from Mar on the same BNTR transfer vehicle thereby cutting the duration of the ERV mission in half--from approximately 4.7 to 2.5 years. Finally, for difficult Mars options, such as Phobos rendezvous and sample return missions, volume (not mass) constraints limit the performance of the "all LH 2 " BNTR stage. The use of "LOX-augmented" NTR (LANTR) engines, operating at a modest oxygen-to-hydrogen mixutre ratio (MR) of 0.5, helps to increase "bulk" propellant density and total thrust during the TMI burn. On all subsequent burns, the bimodal LANTR engines operate on LH 2 only (MR=0) to maximize vehicle performance while staying within the lift capability of two Magnum launches.

Nuclear thermal rocket↗