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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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At least 217 records · Page 12

Development of a Rapid Cycling CO2 and H2O Removal Sorbent

The National Aeronautics and Space Administration (NASA) planned future missions set stringent demands on the design of the Portable Life Support System (PLSS), requiring dramatic reductions in weight, decreased reliance on supplies and greater flexibility on the types of missions. Use of regenerable systems that reduce weight and volume of the Extravehicular Mobility Unit (EMU) is of critical importance to NASA, both for low orbit operations and for long duration manned missions. The carbon dioxide and humidity control unit in the existing PLSS design is relatively large, since it has to remove and store eight hours worth of carbon dioxide (CO2). If the sorbent regeneration can be carried out during the Extravehicular Activity (EVA) with a relatively high regeneration frequency, the size of the sorbent canister and weight can be significantly reduced. TDA Research, Inc. is developing compact, regenerable sorbent materials to control CO2 and humidity in the space suit ventilation loop. The sorbent can be regenerated using space vacuum during the EVA, eliminating all CO2 and humidity duration-limiting elements in the life support system. The material also has applications in other areas of space exploration including long duration exploration missions requiring regenerable technologies and possibly the Crew Exploration Vehicle (CEV) spacecraft. This paper summarizes the results of the sorbent development, testing, and evaluation efforts to date.

Alptekin, Gokhan↗

FD/DAMA Scheme For Mobile/Satellite Communications

Integrated-Adaptive Mobile Access Protocol (I-AMAP) proposed to allocate communication channels to subscribers in first-generation MSAT-X mobile/satellite communication network. Based on concept of frequency-division/demand-assigned multiple access (FD/DAMA) where partition of available spectrum adapted to subscribers' demands for service. Requests processed, and competing requests resolved according to channel-access protocol, or free-access tree algorithm described in "Connection Protocol for Mobile/Satellite Communications" (NPO-17735). Assigned spectrum utilized efficiently.

Yan, Tsun-Yee↗

Adaptive mobile access protocol (AMAP) for the message service of a land mobile satellite experiment (MSAT-X)

This paper describes a feasibility study of the adaptive mobile access protocol (AMAP) for MSATA-X, a proposed experimental mobile satellite communication network. The mobiles are dispersed over a wide geographical area and the channel data rate is limited due to the size and cost limitations of mobile antennas. AMAP is a reservation based multiple-access scheme. The available bandwidth is divided into subchannels, which are divided into reservation and message channels. The ALOHA multiple-access scheme is employed in the reservation channels, while the message channels are demand assigned. AMAP adaptively reallocates the reservation and message channels to optimize system performance. It has been shown that if messages are generated at a rate of one message per hour, AMAP can support approximately 2000 active users per 2400 bit/s channel with an average delay of 1.4 s.

Li, V. O. K.↗

Regional Modeling and Simulation for Vertiport Location Assessment

There is increasing interest in the Urban Air Mobility concept and the realization of electric Vertical Take-Off and Landing (e-VTOL) vehicles flying in the National Airspace System. NASA, FAA, and the industry are investigating various aspects of this new mode of transportation for cargo and humans. There are significant challenges in making this mode a reality, including feasibility, safety, infrastructure, traffic management, public acceptance, and scalability. From the infrastructure perspective, one of the aspects that needs to be addressed is the location of vertiports (named similar to heliports, for vertical take-off and landing vehicles). There is significant on-going research for selecting location of vertiports. However, the locations are largely based on demand models. Also, these efforts are focused in specific local regions, San Francisco/Bay Area, Chicago, Tampa, etc. This talk presents an approach to determine the location of vertiports in regional areas (across the United States), incorporating the desire to have certain attributes closer to or further from the location using a regional modeling tool. The feasibility of flying e-VTOL vehicles between various vertiport locations is also presented using a mobility operations simulation tool.

Air Mobility↗

Advanced Air Mobility Vertiport Considerations: A List and Overview

Advanced air mobility (AAM) is an emerging field in aeronautics that involves utilizing small aircraft for everyday transportation and other services, and many AAM aircraft are envisioned to take off and land at new infrastructure termed vertiports. This paper describes a variety of considerations related to AAM vertiports that need to be considered in the planning for and deployment of vertiports in practice. The factors include siting, design, regulations, safety, environmental impact, social acceptance, equity, and operational integration factors. Over 450 considerations were compiled from Subject Matter Experts (SMEs) participating in NASA’s AAM Ecosystem Working Groups (AEWGs) in October 2021. This paper consolidates these considerations and broadly disseminates the valuable knowledge of these SMEs. These considerations can be used by researchers to conduct demand and network analysis, local transportation planners to develop AAM networks for their community, and the AAM ecosystem members to identify policy, standards, and research gaps.

vertiport considerations↗

A Data Analysis and Simulation Study of Urban Air Mobility

For the Urban Air Mobility (UAM) industry, NASA has defined a series of UAM Maturity Levels (UML) corresponding to increasingly more complex and operationally dense UAM operations. In support of the gradual progression towards higher UML levels, NASA is currently conducting a set of UAM air traffic simulations—collectively referred to as X4. This paper describes a set of system effectiveness measures, and their associated metrics, for data analysis of X4 simulations. The descriptions, rationales, and calculation procedures for two metrics to be used in data analysis of simulation results, the number of predicted demand-capacity imbalances and the pre-departure delays, are described. Results from data analysis of one set of simulation runs are presented to demonstrate how these metrics support the assessment of performance of the system architecture for X4 simulations and the verification of experiment requirements.

Urban Air Mobility↗

The Apollo Lunar Roving Vehicle.

After listing the basic requirements such as operational demands and lunar environmental conditions, characteristic design data of the roving vehicle are given with special attention to the four wheel drive and its control system, the steering system, and the navigational instrumentation. The overall system is optimized in view of total mass, range, mobility, load carrying capability, safety, highest reliability through redundancy, and last but not least, cost and development time. Optimization of the drive and power system has first been evaluated by mathematical models and computational simulation of the vehicle hardware, the wheel/soil interaction, and the lunar terrain profile. The next step to refine optimization and evaluation of the drive, steering, and power system including man/machine interaction has been carried out by the use of a six-degree-of-freedom simulator subjecting the astronauts in their space suits to simulated vehicle motions while driving over a simulated terrain, observable on a cathode ray tube display.

Haeussermann, W.↗

Power system requirements and definition for lunar and Mars outposts

Candidate power systems being considered for outpost facilities (stationary power systems) and vehicles (mobile systems) are discussed, including solar, chemical, isotopic, and reactor. The current power strategy was an initial outpost power system composed of photovoltaic arrays for daytime energy needs and regenerative fuel cells for power during the long lunar night. As day and night power demands grow, the outpost transitions to nuclear-based power generation, using thermoelectric conversion initially and evolving to a dynamic conversion system. With this concept as a guideline, a set of requirements has been established, and a reference definition of candidate power systems meeting these requirements has been identified.

Petri, D. A.↗

Architecture of the TELEDESIC satellite system

There is a significant worldwide demand for broadband communications capacity. Teledesic plans to meet this demand using a constellation of 924 low-Earth orbit (LEO) satellites operating in Ka-band (30/20 GHz). The Teledesic network will provide 'fiber-like' service quality, including low transmission delay, high data rates, and low bit error rates, to fixed and mobile users around the world starting in 2001.

Sturza, Mark A.↗

A Data Analysis Approach for Simulations of Urban Air Mobility Operations

For the Urban Air Mobility (UAM) industry, NASA has defined a series of UAM Maturity Levels (UML) corresponding to increasingly more complex and operationally dense UAM operations. In support of the gradual progression towards higher UML levels, NASA is currently conducting a set of UAM air traffic simulations—collectively referred to as X4. This paper describes a set of system effectiveness measures, and their associated metrics, for data analysis of X4 simulations. The descriptions, rationales, and calculation procedures for two metrics to be used in data analysis of simulation results, the number of predicted demand-capacity imbalances and the pre-departure delays, are described. Results from data analysis of one set of simulation runs are presented to demonstrate how these metrics support the assessment of performance of the system architecture for X4 simulations and the verification of experiment requirements.

Urban Air Mobility↗

Investigation and Evaluation of Advanced Spectrum Management Concepts for Aeronautical Communications

With the emergence of new aerial vehicles into the airspace and the continued growth of aviation operations, there will be an increasing demand for voice and data communications within the National Airspace System (NAS). The continued use of existing VHF and UHF frequency allocations is not a sustainable approach, and as a result, a new spectrum management solution is required to support future mission needs. The proposed spectrum management concepts leverage modern advancements such as artificial intelligence (AI) and big data to dynamically optimize the spectrum utilization based on the predicted communications demand throughout the airspace. This technical investigation considers both air-ground and air-air communications networks, and can be applied to both existing applications such as the air traffic control (ATC) system, as well as future applications, such as the emerging Advanced Air Mobility (AAM). To support the evaluation of the proposed concepts and technologies, a modeling and simulation capability is currently under development and will continue to evolve to support new and advanced airspace applications. It is anticipated that this proposed spectrum concept will better serve the spectrum needs of future NAS applications.

Eric J Knoblock↗

Investigation and Evaluation of Advanced Spectrum Management Concepts for Aeronautical Communications

With the emergence of new aerial vehicles into the airspace and the continued growth of aviation operations, there will be an increasing demand for voice and data communications within the National Airspace System (NAS). The continued use of existing VHF and UHF frequency allocations is not a sustainable approach, and as a result, a new spectrum management solution is required to support future mission needs. The proposed spectrum management concepts leverage modern advancements such as artificial intelligence (AI) and big data to dynamically optimize the spectrum utilization based on the predicted communications demand throughout the airspace. This technical investigation considers both air-ground and air-air communications networks, and can be applied to both existing applications such as the air traffic control (ATC) system, as well as future applications, such as the emerging Advanced Air Mobility (AAM). To support the evaluation of the proposed concepts and technologies, a modeling and simulation capability is currently under development and will continue to evolve to support new and advanced airspace applications. It is anticipated that this proposed spectrum concept will better serve the spectrum needs of future NAS applications.

Eric J Knoblock↗

Satellite multiple access systems for mobile communication

This paper considers multiple access techniques for a mobile radio system which incorporates a geosynchronous orbiting satellite repeater through which mobile terminals communicate. The communication capacities of FDMA, TDMA and CDMA systems are examined for a 4 MHz bandwidth system to serve up to 10,000 users. An FDMA system with multibeam coverage is analyzed in detail. The system includes an order-wire network for demand-access control and reassignment of satellite channels. Satellite and terminal configurations are developed to a block diagram level and system costs and implementation requirements are discussed.

Lewis, J. L.↗

Developing the next phase in NASA's satellite communications program

Since 1973, NASA has conducted hundreds of user experiments and demonstrations using the Applications Technology Satellites ATS-1, -3, and -6, and the Communications Technology Satellite CTS. Now, projections show that the commercial demand will continue to increase, soon exceeding the current technology's capacity. The next phase in NASA's satellite communication program include 30/20 GHz Ka-band technology, extending the current work in advanced multibeam antennas; a narrow-band system and technology study that could lead to mobile and transportable communication developments; and studies of future uses of technology in communications.

Dement, D. K.↗

NASA GRC/Aeronautics Overview

Twenty-first-century aeropropulsion and power research will enable new transport engine and aircraft systems including: 1) Emerging ultralow noise and emissions with the use of intelligent turbofans; 2) Future distributed vectored propulsion with 24-hour operations and greater community mobility; 3) Research in hybrid combustion and electric propulsion systems leading to silent aircraft with near-zero emissions; and 4) The culmination of these revolutions will deliver an all-electric- powered propulsion system with zero-impact emissions and noise and high-capacity, on-demand operation

Sehra, Arun K.↗

Adaptive data rate SSMA system for personal and mobile satellite communications

An adaptive data rate SSMA (spread spectrum multiple access) system is proposed for mobile and personal multimedia satellite communications without the aid of system control earth stations. This system has a constant occupied bandwidth and has variable data rates and processing gains to mitigate communication link impairments such as fading, rain attenuation and interference as well as to handle variable data rate on demand. Proof of concept hardware for 6MHz bandwidth transponder is developed, that uses offset-QPSK (quadrature phase shift keying) and MSK (minimum shift keying) for direct sequence spread spectrum modulation and handle data rates of 4k to 64kbps. The RS422 data interface, low rate voice and H.261 video codecs are installed. The receiver is designed with coherent matched filter technique to achieve fast code acquisition, AFC (automatic frequency control) and coherent detection with minimum hardware losses in a single matched filter circuit. This receiver structure facilitates variable data rate on demand during a call. This paper shows the outline of the proposed system and the performance of the prototype equipment.

Ikegami, Tetsushi↗

Exploratory Analysis of the Airspace Throughput and Sensitivities of an Urban Air Mobility System

The use of small, vertical-takeoff and landing aircraft to provide efficient, high-speed, ondemand passenger transportation within a metropolitan area (e.g. intra-city transportation) is a topic of increasing interest and investment within the aerospace and transportation communities. Preliminary, mostly vehicle-level analysis suggests that passenger-carrying “Urban Air Mobility” has the potential to provide meaningful door-to-door trip time savings compared to identical trips taken solely by automobile, even for relatively short trips of a few tens of miles. Subsequent analysis has shown that if such trips can be conducted at costs competitive with ground transportation, the demand for such flight operations, not surprisingly, becomes unprecedented by historical airspace operations counts, raising fundamental questions regarding feasibility, practicality, capacity and basic system attributes such as separation criteria. In this paper, we conduct a preliminary assessment of vertipad requirements and en route separation minima relative to the feasibility of large-scale urban aviation operations. This analysis is acknowledged as being far from comprehensive and is intended to help define the initial boundaries of an airspace system compatible with enabling high-volume operations.

Goodrich, Kenneth H.↗

Performance analysis of an adaptive multiple access scheme for the message service of a land mobile satellite experiment (MSAT-X)

This paper describes an Adaptive Mobile Access Protocol (AMAP) for the message service of MSAT-X., a proposed experimental mobile satellite communication network. Message lengths generated by the mobiles are assumed to be uniformly distributed. The mobiles are dispersed over a wide geographical area and the channel data rate is limited. AMAP is a reservation based multiple access scheme. The available bandwidth is divided into subchannels, which are divided into reservation and message channels. The ALOHA multiple access scheme is employed in the reservation channels, while the message channels are demand assigned. AMAP adaptively reallocates the reservation and message channels to optimize the total average message delay.

Yan, T.-Y.↗