Search Results

THE NASA SPACE STATION holds remarkable similarity to the modern nuclear powered submarine. Both are required to provide a 90-day mission capability during which all aspects of human habitation must be accomodated. The requirements for environmental control, and failure tolerance of environmental control systems, are also quite similar. Although the resources, operating environments, and mission objectives for the submarine and space station are distinctly different, the problems faced by the environmental control and life support system (ECLSS) engineer require application of the same technologies and design principles. This paper addresses the resources and mission requirements specific to the two vehicles, and discusses their influence on the design of the ECLSS. The design constraints for individual ECLSS subsystems are discussed with the resultant impact on design approach selected for each vehicle.

Mars, our nearest planet outward from the sun, has been targeted for several decades as a prospective site for expanded human habitation. Background space radiation exposures on Mars are expected to be orders of magnitude higher than on Earth. Recent risk analysis procedures based on detailed dosimetric techniques applicable to sensitive human organs have been developed along with experimental data regarding cell mutation rates resulting from exposures to a broad range of particle types and energy spectra. In this context, simulated exposure and subsequent risk for humans in residence on Mars are examined. A conceptual habitat structure, CAD-modeled with duly considered inherent shielding properties, has been implemented. Body self-shielding is evaluated using NASA standard computerized male and female models.

The current status of the NERVA Nuclear Rocket Engine Design Methodology is presented together with specific examples of the application of modern probabilistic design techniques which lead to having high reliability in the initial design.

THE LOW-POWER SPACE NUCLEAR ROCKET conceived by NASA engineers is described in this paper. It is compared with the chemical rocket and the nuclear turboelectric ion propulsion system. In developing the concept for this low-power rocket, NASA engineers concentrated on attaining low weight and high hydrogen temperature, and on solving problems concerned with automatic control and operation of high-temperature reactors. It was presumed that the NASA 1.5 million-lb thrust engine would be available, and could place 25,000 lb in orbit, at the time the nuclear rocket is ready for test. As experience is gained reactors of higher power can be developed. These can, perhaps, be used as second stages of larger chemical boosters. Finally, high-power, high-temperature rockets for booster application can be undertaken.

Use of nuclear power systems in space requires approval which is preceded by extensive safety analysis and review. This careful study allows an informed risk-benefit decision at the highest level of our government. This paper describes the process as it has historically been applied to U.S. isotopic power systems. The Ulysses mission, launched in October 1990, is used to illustrate the process. Expected variations to deal with reactor-power systems are explained.

A nuclear-magnetogasdynamic (MGD) power generation system is described which is capable of satisfying the long-duration, high power level mission requirements of space vehicles. In this Rankine cycle system, radio-frequency (RF) electric fields are used to ionize a cool supersonic gas, and the Hall effect is used to generate electrical power. Following an analysis of MGD energy conversion and RF plasma production, preliminary design is made of an-experimental system having a generator power density of 10 megawatts/cu m in which 5% of the output power is used to produce the cool plasma.

A NASA Learjet was used to produce a low-gravity environment for two series of nucleate pool boiling experiments. Surface-temperature and heat-flux measurements and high-speed microphotography of bubble phenomena were made on 18 prepared boiling surfaces. The surfaces were polished copper disks, 25.4 mm and 19.1 mm in diameter, with variable artificial nucleation site densities from 0.2 to 32 sites/cm2. Both 1-g and low-g data were obtained for comparison. In every case, the boiling heat-transfer coefficient increased significantly to a new steady value for the duration of the low-gravity period. Rapid movement of the surfaces of the large vapor masses that were observed is indicative of considerable turbulent liquid motion, apparently induced by the bubble growth and coalescence. In no case was a decreased heat-transfer coefficient observed, which would be indicative of film boiling.

A typical nucleonic propellant gaging and utilization system for space vehicles is described, together with a detailed discussion of the individual components. Photographs of prototype installations and test results of these configurations are presented to substantiate the theoretical analyses for signal propagation and radiation pattern mapping including measurements under zero gravity conditions. The results are concluded as verifying the nucleonic measurement system capability for providing an accurate, highly reliable approach to maximum cost effectiveness of propellant gaging and utilization system design.

For the ice protection of the engine air induction part manufactured with low thermal conductivity composite material, the combined heating method using interior impingement and exterior air film has certain advantages. To study the influence of the external jet air film on the impingement characteristics of droplets, the numerical simulation method of three dimensional water droplet impingement based on Eulerian method was developed and verified by experimental data from references. The droplets impingement characteristics under three different blowing ratios and two different velocities were then investigated based on the configuration of 3D cylinder with two parallel jet holes.

Reliable tools for the prediction of aeroacoustic noise are of major interest for the car industry and also for the vendors of heating, ventilation and air conditioning (HVAC) systems whose aim is to reduce the negative impact of HVAC noise onto passengers. In this work a hybrid approach based on the acoustic perturbation equations is tested for this purpose. In a first step, the incompressible flow field is computed by means of a commercial finite volume solver. A large eddy simulation turbulence model is used to obtain time resolved flow data, which is required to accurately predict acoustic phenomena. Subsequently, the aeroacoustic sources are computed and conservatively interpolated to a finite element grid, which is used to calculate the sound radiation. This procedure is tested for an HVAC unit, a radial blower and finally for a complete system, which combines these two components.

The proper design procedure is a critical factor that restricts the capacity of an unmanned aerial vehicle (UAV) to fly freely for long periods. A UAV could fly with a high lift force and less drag if the aerodynamic performance of the wings is taken into account. With the aim to identify the best configuration that provides a high aerodynamic ratio (L/D) at low flying speeds, the current study investigates single-taper wings with three different configurations (conventional, dihedral, and polyhedral). This is achieved by applying the fundamentals of sailplanes to the single-taper wing planform in this study. Various attacking angles from 0° to 15° were tested in the research using a high-lift low-speed airfoil, the AG-16, and a constant low Reynolds number of 3 × 105. SOLIDWORKS software was used to model the wings under investigation, while ANSYS Fluent software was used to run the simulation.

It is necessary to develop a small positive pressure control system for the closed ecology experiment facility (CEEF) to protect against over-differential pressure loading. In the present study, a numerical method was developed to calculate the quantity of state of the closed module, which is fitted with rubber buffers, for the small positive pressure control system. Experiments to examine the pressure change of the closed module were carried out at CEEF. Comparison of calculated and experimental results showed that the present dynamic simulation is suited to estimating the quantity of state of the closed module.

Two three-dimensional cabin airflow configurations have been the subject of experimental and analytical testing to establish the validity and role of computational fluid dynamics (CFD) tools in the design of cabin airflow distribution systems. The CFD tools considered here are two separate Navier-Stokes computer codes which have been used for a number of applications, including those in the present study. A correlative study of a detailed air supply nozzle configuration has been examined to further understand its flow characteristics and to establish a procedure for examining cases with large size scale differences. The comparison of experimental results with the numerical simulations in the two cases is generally quite good, leading to an increased confidence in the application of CFD methods within the cabin airflow distribution system design arena.

A numerical simulation system of airflow around the Detroit Flying Cars-Wild Dream 1 (WD-1) is introduced. It involves the application of FVM, the mesh-independence system, boundary conditions and the verification of the simulation conditions to NACA airfoil data and the discussion of technological treatments corresponding to the evaluation of asymmetric wings. The present work is investigating the aerodynamic behavior of an asymmetric canard-wing system used on the Detroit Flying Cars-WD 1 model. The work involves the application of Finite Volume Method (FVM), the mesh-independence system, boundary conditions and the verification of simulation conditions to NACA airfoil data using OpenFOAM software. The Reynolds number based on free stream velocity and root chord is 5X106.

For a disaster relief and automatic inspections, an unmanned helicopter is strongly expected. To develop this, a very high power density source is required. A Wankel-type rotary engine can be the best candidate for the power source. In this study, the development of a very small rotary engine with a displacement of 30 cc is targeted. In order to improve the combustion efficiency, gas exchange and stable ignition, a multi dimensional simulation inside the combustion chamber was carried out. At first, the effect of volumetric efficiency on the maximum power is mentioned. Secondly, the effect of scavenging efficiency is discussed. Thirdly, a blow off through a plug hole is described. The position of plug hole was found important to reduce the blow off amount. Finally, the effect of combustion speed on the engine performance is predicted. As a result, the proposed design will be tested using a proto-type engine.

This paper focuses on the issues concerning gyroplane powertrain cooling. The Rotax 912S engine was selected as a propulsion system following a detailed analysis. A one-dimensional model, simulated with the AVL Boost software, was applied to determine the heat balance of the engine and the heat flux penetrating through each of engine's surfaces. The geometrical quantities defined in the model were obtained by measuring a three-dimensional geometry provided by an authorized Rotax engine supplier company. Calculation results were then verified by comparing the obtained values with data available from the Rotax 912S engine and with the values of individual parameters given in the literature.

In a satellite thruster the function of injector plays a major role in controlling the combustion. This paper presents the numerical simulation of two most used injectors namely, impinging doublet, and triplet using Ansys fluent. The injectors are designed for the non-toxic, green propellants used in satellite thrusters. The present study focuses on the design and simulation of the injectors with 2 variant of green propellants i.e., Kerosene/Hydrogen-peroxide and Ethanol Amine/Hydrogen-peroxide. The objective of the study is to investigate the performance of the two injectors in terms of atomization, combustion efficiency and thrust generation. Theoretical design calculations were performed for a 20 N bi-propellant satellite thruster. A comparative study on the condensed combustion products and injector was carried out using NASA CEA Run code and Ansys fluent, respectively. The ethanol amine/hydrogen-peroxide injector showed better performance in terms of combustion efficiency.

Despite the continuous efficiency increase, traditional vehicles still dissipate large amounts of energy. While actual hybrid powertrains allow to recover kinetic energy during the braking phases, exhaust gas energy can be recovered through the electric turbo compound (ETC). A turbocharger (TC) match with an electric machine (EM) appears to be the best solution for passenger cars since it also permits turbo lag reduction with restricted system complexity increase. The goal of this paper is to investigate the TC electrification impact on fuel consumption, considering transient behavior during a whole drive cycle simulation. This is obtained coupling a detailed one-dimensional (1-D) engine model with vehicle dynamics and signal processing by means of sole GT-Suite software. A baseline engine refers to a 1.3 L, SI, 3-cylinder turbocharged engine while a class C vehicle is modelled.

Materials play a key role in our day to day life and have shaped the industrial revolution to a great extent. Right selection of material for meeting a particular objective is the key to success in today’s world where the cost as well as sustainability of any equipment or a system have assumed greater significance than ever before. In automotive industry, materials have a definitive role as far as the mobility and safety is concerned. Materials that can absorb the required energy or impact can be manufactured through different manufacturing as well as metallurgical processes which involves appropriate heat treatment and bringing correct chemical compositions etc. However, they can also be formed by simpler methods such as combining certain materials together in the form of layered combinations to form light weight composites.