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NASA NTRS2000

Climatological Processing and Product Development for the TRMM Ground Validation Program

The Tropical Rainfall Measuring Mission (TRMM) satellite was successfully launched in November 1997.The main purpose of TRMM is to sample tropical rainfall using the first active spaceborne precipitation radar. To validate TRMM satellite observations, a comprehensive Ground Validation (GV) Program has been implemented. The primary goal of TRMM GV is to provide basic validation of satellite-derived precipitation measurements over monthly climatologies for the following primary sites: Melbourne, FL; Houston, TX; Darwin, Australia- and Kwajalein Atoll, RMI As part of the TRMM GV effort, research analysts at NASA Goddard Space Flight Center (GSFC) generate standardized rainfall products using quality-controlled ground-based radar data from the four primary GV sites. This presentation will provide an overview of TRMM GV climatological processing and product generation. A description of the data flow between the primary GV sites, NASA GSFC, and the TRMM Science and Data Information System (TSDIS) will be presented. The radar quality control algorithm, which features eight adjustable height and reflectivity parameters, and its effect on monthly rainfall maps, will be described. The methodology used to create monthly, gauge-adjusted rainfall products for each primary site will also be summarized. The standardized monthly rainfall products are developed in discrete, modular steps with distinct intermediate products. A summary of recently reprocessed official GV rainfall products available for TRMM science users will be presented. Updated basic standardized product results involving monthly accumulation, Z-R relationship, and gauge statistics for each primary GV site will also be displayed.

Marks, D. A.↗

NASA NTRS2002

Affordable Flight Demonstration of the GTX Air-Breathing SSTO Vehicle Concept

The rocket based combined cycle (RBCC) powered single-stage-to-orbit (SSTO) reusable launch vehicle has the potential to significantly reduce the total cost per pound for orbital payload missions. To validate overall system performance, a flight demonstration must be performed. This paper presents an overview of the first phase of a flight demonstration program for the GTX SSTO vehicle concept. Phase 1 will validate the propulsion performance of the vehicle configuration over the supersonic and hypersonic airbreathing portions of the trajectory. The focus and goal of Phase 1 is to demonstrate the integration and performance of the propulsion system flowpath with the vehicle aerodynamics over the air-breathing trajectory. This demonstrator vehicle will have dual mode ramjet/scramjets, which include the inlet, combustor, and nozzle with geometrically scaled aerodynamic surface outer mold lines (OML) defining the forebody, boundary layer diverter, wings, and tail. The primary objective of this study is to demonstrate propulsion system performance and operability including the ram to scram transition, as well as to validate vehicle aerodynamics and propulsion airframe integration. To minimize overall risk and development cost the effort will incorporate proven materials, use existing turbomachinery in the propellant delivery systems, launch from an existing unmanned remote launch facility, and use basic vehicle recovery techniques to minimize control and landing requirements. A second phase would demonstrate propulsion performance across all critical portions of a space launch trajectory (lift off through transition to all-rocket) integrated with flight-like vehicle systems.

Krivanek, Thomas M.↗

NASA NTRS1984

Deployable beam flight experiment (MAST)

Improvement of technology of space systems control is discussed. Future space systems such as large antennas or a space station may have dimensions on the order of 30 m to 200 m, yet their basic structures may be relatively lightweight and flexible, making ground tests for loads, controls analyses, and design verifications questionable if not impossible. Abandoning the extensive ground test and analysis verification program that led to the success of previous spacecraft is not a sensible option; making it meaningful using current technology will require inefficient, ultraconservative structure and control designs. New test methods are outlined.

Hanks, B. R.↗

NASA NTRS2003

Affordable Flight Demonstration of the GTX Air-Breathing SSTO Vehicle Concept

The rocket based combined cycle (RBCC) powered single-stage-to-orbit (SSTO) reusable launch vehicle has the potential to significantly reduce the total cost per pound for orbital payload missions. To validate overall system performance, a flight demonstration must be performed. This paper presents an overview of the first phase of a flight demonstration program for the GTX SSTO vehicle concept. Phase 1 will validate the propulsion performance of the vehicle configuration over the supersonic and hypersonic air- breathing portions of the trajectory. The focus and goal of Phase 1 is to demonstrate the integration and performance of the propulsion system flowpath with the vehicle aerodynamics over the air-breathing trajectory. This demonstrator vehicle will have dual mode ramjetkcramjets, which include the inlet, combustor, and nozzle with geometrically scaled aerodynamic surface outer mold lines (OML) defining the forebody, boundary layer diverter, wings, and tail. The primary objective of this study is to demon- strate propulsion system performance and operability including the ram to scram transition, as well as to validate vehicle aerodynamics and propulsion airframe integration. To minimize overall risk and develop ment cost the effort will incorporate proven materials, use existing turbomachinery in the propellant delivery systems, launch from an existing unmanned remote launch facility, and use basic vehicle recovery techniques to minimize control and landing requirements. A second phase would demonstrate propulsion performance across all critical portions of a space launch trajectory (lift off through transition to all-rocket) integrated with flight-like vehicle systems.

Krivanek, Thomas M.↗

NASA NTRS1977

The 6670-Newton attitude-control thruster using hydrogen-oxygen propellant

The development of a reusable, attitude-control propulsion system for the space transportation system is discussed. A flight weight, gaseous oxygen attitude control thruster assembly was tested to obtain data on cyclic life, thermal and hydraulic characteristics, pulse response, and performance. The basic thruster components were tested in excess of 51,000 pulses and 660 seconds, steady state, with no degradation of the 93 percent characteristic exhaust velocity efficiency level. Nominal operating conditions were a chamber pressure of 207 N sq cm (300 psia), a mixture ratio of 4.0, a pulse width of 100 ms, and a pulse frequency of 2 Hz.

Gordon, L. H.↗

NASA NTRS2011

Engineering the System and Technical Integration

Approximately 80% of the problems encountered in aerospace systems have been due to a breakdown in technical integration and/or systems engineering. One of the major challenges we face in designing, building, and operating space systems is: how is adequate integration achieved for the systems various functions, parts, and infrastructure? This Contractor Report (CR) deals with part of the problem of how we engineer the total system in order to achieve the best balanced design. We will discuss a key aspect of this question - the principle of Technical Integration and its components, along with management and decision making. The CR will first provide an introduction with a discussion of the Challenges in Space System Design and meeting the challenges. Next is an overview of Engineering the System including Technical Integration. Engineering the System is expanded to include key aspects of the Design Process, Lifecycle Considerations, etc. The basic information and figures used in this CR were presented in a NASA training program for Program and Project Managers Development (PPMD) in classes at Georgia Tech and at Marshall Space Flight Center (MSFC). Many of the principles and illustrations are extracted from the courses we teach for MSFC.

Blair, J. C.↗

NASA NTRS2000

Black Holes, Worm Holes, and Future Space Propulsion

NASA has begun examining the technologies needed for an Interstellar Mission. In 1998, a NASA Interstellar Mission Workshop was held at the California Institute of Technology to examine the technologies required. Since then, a spectrum of research efforts to support such a mission has been underway, including many advanced and futuristic space propulsion concepts which are being explored. The study of black holes and wormholes may provide some of the breakthrough physics needed to travel to the stars. The first black hole, CYGXI, was discovered in 1972 in the constellation Cygnus X-1. In 1993, a black hole was found in the center of our Milky Way Galaxy. In 1994, the black hole GRO J1655-40 was discovered by the NASA Marshall Space Flight center using the Gamma Ray Observatory. Today, we believe we have found evidence to support the existence of 19 black holes, but our universe may contain several thousands. This paper discusses the dead star states - - both stable and unstable, white dwarfs, neutron stars, pulsars, quasars, the basic features and types of black holes: nonspinning, nonspinning with charge, spinning, and Hawking's mini black holes. The search for black holes, gravitational waves, and Laser Interferometer Gravitational Wave Observatory (LIGO) are reviewed. Finally, concepts of black hole powered space vehicles and wormhole concepts for rapid interstellar travel are discussed in relation to the NASA Interstellar Mission.

Barret, Chris↗

NASA NTRS1995

Marshall Space Flight Center Electromagnetic Compatibility Design and Interference Control (MEDIC) handbook

The purpose of the MEDIC Handbook is to provide practical and helpful information in the design of electrical equipment for electromagnetic compatibility (EMS). Included is the definition of electromagnetic interference (EMI) terms and units as well as an explanation of the basic EMI interactions. An overview of typical NASA EMI test requirements and associated test setups is given. General design techniques to minimize the risk of EMI and EMI suppression techniques at the board and equipment interface levels are presented. The Handbook contains specific EMI test compliance design techniques and retrofit fixes for noncompliant equipment. Also presented are special tests that are useful in the design process or in instances of specification noncompliance.

Clark, T. L.↗

NASA NTRS1983

Shuttle measured contaminant environment and modeling for payloads. Preliminary assessment of the space telescope environment in the shuttle bay

A baseline gaseous and particulate environment of the Shuttle bay was developed based on the various measurements which were made during the first four flights of the Shuttle. The environment is described by the time dependent pressure, density, scattered molecular fluxes, the column densities and including the transient effects of water dumps, engine firings and opening and closing of the bay doors. The particulate conditions in the ambient and on surfaces were predicted as a function of the mission time based on the available data. This basic Shuttle environment when combined with the outgassing and the particulate contributions of the payloads, can provide a description of the environment of a payload in the Shuttle bay. As an example of this application, the environment of the Space Telescope in the bay, which may be representative of the environment of several payloads, was derived. Among the many findings obtained in the process of modeling the environment, one is that the payloads environment in the bay is not substantially different or more objectionable than the self-generated environment of a large payload or spacecraft. It is, however, more severe during ground facilities operations, the first 15 to 20 hours of the flight, during and for a short period after ater was dumped overboard, and the reaction control engines are being fired.

Scialdone, J. J.↗

NASA NTRS1999

Constrained Vapor Bubble

The nonisothermal Constrained Vapor Bubble, CVB, is being studied to enhance the understanding of passive systems controlled by interfacial phenomena. The study is multifaceted: 1) it is a basic scientific study in interfacial phenomena, fluid physics and thermodynamics; 2) it is a basic study in thermal transport; and 3) it is a study of a heat exchanger. The research is synergistic in that CVB research requires a microgravity environment and the space program needs thermal control systems like the CVB. Ground based studies are being done as a precursor to flight experiment. The results demonstrate that experimental techniques for the direct measurement of the fundamental operating parameters (temperature, pressure, and interfacial curvature fields) have been developed. Fluid flow and change-of-phase heat transfer are a function of the temperature field and the vapor bubble shape, which can be measured using an Image Analyzing Interferometer. The CVB for a microgravity environment, has various thin film regions that are of both basic and applied interest. Generically, a CVB is formed by underfilling an evacuated enclosure with a liquid. Classification depends on shape and Bond number. The specific CVB discussed herein was formed in a fused silica cell with inside dimensions of 3x3x40 mm and, therefore, can be viewed as a large version of a micro heat pipe. Since the dimensions are relatively large for a passive system, most of the liquid flow occurs under a small capillary pressure difference. Therefore, we can classify the discussed system as a low capillary pressure system. The studies discussed herein were done in a 1-g environment (Bond Number = 3.6) to obtain experience to design a microgravity experiment for a future NASA flight where low capillary pressure systems should prove more useful. The flight experiment is tentatively scheduled for the year 2000. The SCR was passed on September 16, 1997. The RDR is tentatively scheduled for October, 1998.

Huang, J.↗

NASA NTRS1974

Evaluation of soft rubber goods

The performance of rubber goods suitable for use as O-rings, seals, gaskets, bladders and diaphragms under conditions simulating those of the space shuttle were studied. High reliability throughout the 100 flight missions planned for the space shuttle was considered of overriding importance. Accordingly, in addition to a rank ordering of the selected candidate materials based on prolonged fluid compatibility and sealability behavior, basic rheological parameters (such as cyclic hysteresis, stress relaxation, indicated modulus, etc.) were determined to develop methods capable of predicting the cumulative effect of these multiple reuse cycles.

Merz, P. L.↗

NASA NTRS1993

Performance characteristics of a variable-area vane nozzle for vectoring an ASTOVL exhaust jet up to 45 deg

Many conceptual designs for advanced short-takeoff, vertical landing (ASTOVL) aircraft need exhaust nozzles that can vector the jet to provide forces and moments for controlling the aircraft's movement or attitude in flight near the ground. A type of nozzle that can both vector the jet and vary the jet flow area is called a vane nozzle. Basically, the nozzle consists of parallel, spaced-apart flow passages formed by pairs of vanes (vanesets) that can be rotated on axes perpendicular to the flow. Two important features of this type of nozzle are the abilities to vector the jet rearward up to 45 degrees and to produce less harsh pressure and velocity footprints during vertical landing than does an equivalent single jet. A one-third-scale model of a generic vane nozzle was tested with unheated air at the NASA Lewis Research Center's Powered Lift Facility. The model had three parallel flow passages. Each passage was formed by a vaneset consisting of a long and a short vane. The longer vanes controlled the jet vector angle, and the shorter controlled the flow area. Nozzle performance for three nominal flow areas (basic and plus or minus 21 percent of basic area), each at nominal jet vector angles from -20 deg (forward of vertical) to +45 deg (rearward of vertical) are presented. The tests were made with the nozzle mounted on a model tailpipe with a blind flange on the end to simulate a closed cruise nozzle, at tailpipe-to-ambient pressure ratios from 1.8 to 4.0. Also included are jet wake data, single-vaneset vector performance for long/short and equal-length vane designs, and pumping capability. The pumping capability arises from the subambient pressure developed in the cavities between the vanesets, which could be used to aspirate flow from a source such as the engine compartment. Some of the performance characteristics are compared with characteristics of a single-jet nozzle previously reported.

Mcardle, Jack G.↗

NASA NTRS1993

Performance characteristics of a variable-area vane nozzle for vectoring an ASTOVL exhaust jet up to 45 deg

Mcardle, Jack G.↗

NASA NTRS1966

A Modular Nuclear Vehicle System with Multi-Mission Capability for Mars Stopover Missions

In depth studies conducted over the past two years have established a modular nuclear stage concept which offers multi-mission capability with a maximum of hardware commonality, i.e., a concept which minimizes total hardware development effort and investment in facilities while providing a logical development evolution from ground test systems to flight test and from initial to more ambitious space applications. Recent results oriented toward the definition and application of such a vehicle concept for the manned Mars landing mission are presented. The basic modular concept employing NERVA nuclear rocket engines is reviewed and the mission peculiar factors affecting the module sizes and number of modules required are discussed. Specific results presented are restricted primarily to the 1982 Mars landing mission via the opposition class mission mode since this is the earliest anticipated date for such a mission. The realistic effects of orbital launch windows are considered and brief discussions of orbital assembly and packaging options with a modular approach are given. Typical ground launch and orbital assembly operations are defined assuming an uprated Saturn V class launch vehicle and the connecting mode of orbital assembly, in which all modules are orbited fully loaded with propellant. The effect of a significant increase in nuclear engine specific impulse is discussed.

Harris, Ronald J.↗

NASA NTRS2000

Laboratory Studies of Optical Characteristics and Condensation Processes of Cosmic Dust Particles

Information about the optical characteristics and physical processes involving cosmic dust particles is vital for interpretation of astronomical observations and an understanding of the formation and processing of dust in the evolutionary cycle of matter in the interstellar medium. Cosmic dust particles are formed in a variety of astrophysical environments such as in cool stellar outflows and circumstellar envelopes. Definitive knowledge of the nature, composition, and physical processes of cosmic dust grains, however, can only be inferred from astronomical observations through laboratory experiments on the analogs of hypothesized dust particles and with modeling calculations. Laboratory investigations of the nature, composition, and optical characteristics of cosmic dust particles are being, carried out at many institutions with a variety of experimental techniques. Despite a wealth of available data, however, many basic issues remain unresolved. An experimental facility based on suspension of dust particles in electrodynamic balance in a pressure/temperature controlled environment in a cavity has been operational at the NASA Marshall Space Flight Center, and is currently being employed for studies of dust particle charging mechanisms using electron beams and with UV radiation. In this paper, we discuss two general classes of experiments under planning stages that may be simultaneously carried out on this facility for cosmic dust investigations (i) Infrared optical characteristics (extinction coefficients and scattering phase functions) of the analogs of hypothesized of cosmic dust particles, such as natural and synthetic amorphous silicates with varying compositions, amorphous carbon grains, polycyclic aromatic hydrocarbons (PAHs), and icy core-mantle particles etc. The initial spectral range under consideration is 1-25 micrometers, to be extended to the far infrared region in the future (ii) Condensation of volatile gases on nucleus dust particles to be investigated for planetary and astrophysical environments.

Spann, J. F., Jr.↗

NASA NTRS1985

Vibration characteristics of the HPOTP (High Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine)

A review is presented of various rotordynamic problems which have been encountered and eliminated in developing the current flight engines, and continuing subsynchronous problems which are being encountered in developing a 109% power level engine. The basic model for the High Pressure Oxygen Turbopump (HPOTP) of the SSME including the structural dynamic model for the rotor and housing and component models for the liquid and gas seals, turbine-clearance excitation forces, and impeller-diffuser forces are discussed. Results from a linear model are used to examine the synchronous response and stability characteristics of the HPOTP, examining bearing load and stability problems associated with the second critical speed. Various seal modifications are examined and shown to have favorable consequences with respect to bearing reactions and stability.

Childs, D. W.↗

NASA NTRS1996

Analysis of space radiation data of semiconductor memories

This article presents an analysis of radiation effects for several select device types and technologies aboard the Combined Release and Radiation Effects Satellite (CRRES) satellite. These space-flight measurements covered a period of about 14 months of mission lifetime. Single Event Upset (SEU) data of the investigated devices from the Microelectronics Package (MEP) were processed and analyzed. Valid upset measurements were determined by correcting for invalid readings, hard failures, missing data tapes (thus voids in data), and periods over which devices were disabled from interrogation. The basic resolution time of the measurement system was confirmed to be 2 s. Lessons learned, important findings, and recommendations are presented.

Flight Experiment↗

NASA NTRS1988

The Cooperative VAS Program with the Marshall Space Flight Center

Work was divided between the analysis/forecast model development and evaluation of the impact of satellite data in mesoscale numerical weather prediction (NWP), development of the Multispectral Atmospheric Mapping Sensor (MAMS), and other related research. The Cooperative Institute for Meteorological Satellite Studies (CIMSS) Synoptic Scale Model (SSM) has progressed from a relatively basic analysis/forecast system to a package which includes such features as nonlinear vertical mode initialization, comprehensive Planetary Boundary Layer (PBL) physics, and the core of a fully four-dimensional data assimilation package. The MAMS effort has produced a calibrated visible and infrared sensor that produces imager at high spatial resolution. The MAMS was developed in order to study small scale atmospheric moisture variability, to monitor and classify clouds, and to investigate the role of surface characteristics in the production of clouds, precipitation, and severe storms.

Diak, George R.↗