Coatings for directional eutectics

Coating compositions were evaluated for oxidation protection of directionally solidified composite alloy NiTaC-13. These coatings included three NiCrAlY compositions (30-5-1, 25-10-1 and 20-15-1), two FeCrAlY compositions (30-5-1 and 25-10-1), a CoCrAlY composition (25-10-1), and one duplex coating, Ni-35Cr + Al. Duplicate pin samples of each composition were evaluated using two cyclic furnace oxidation tests of 100 hours at 871 C and 500 hours at 1093 C. The two best coatings were Ni-20Cr-15Al-lY and Ni-35Cr + Al. The two preferred coatings were deposited on pins and were evaluated in detail in .05 Mach cyclic burner rig oxidation to 1093 C. The NiCrAlY coating was protective after 830 hours of cycling, while the duplex coating withstood 630 hours. Test bars were coated and cycled for up to 500 hours. Tensile tests indicated no effect of coatings on strength. In 871 C air stress rupture, a degradation was observed for coated relative to bare material. The cycled NiCrAlY coating offered excellent protection with properties superior to the bare cycled NiTaC-13 in 1093 C air stress rupture

Measurement of precipitation induced FUV emission and Geocoronal Lyman Alpha from the IMI mission

This final report describes the activities of the Lockheed Martin Palo Alto Research Laboratory in studying the measurement of ion and electron precipitation induced Far Ultra-Violet (FUV) emissions and Geocoronal Lyman Alpha for the NASA Inner Magnetospheric Imager (IMI) mission. this study examined promising techniques that may allow combining several FUV instruments that would separately measure proton aurora, electron aurora, and geocoronal Lyman alpha into a single instrument operated on a spinning spacecraft. The study consisted of two parts. First, the geocoronal Lyman alpha, proton aurora, and electron aurora emissions were modeled to determine instrument requirements. Second, several promising techniques were investigated to determine if they were suitable for use in an IMI-type mission. Among the techniques investigated were the Hydrogen gas cell for eliminating cold geocoronal Lyman alpha emissions, and a coded aperture spectrometer with sufficient resolution to separate Doppler shifted Lyman alpha components

The hydrogen coma of Comet Halley before perihelion: Preliminary observations with dynamics Explorer 1

The hydrogen coma of Comet Halley has been observed in resonantly scattered solar Lyman-alpha radiation during the period 1-29 January 1986 as the comet approached perihelion. These observations were obtained with the imaging photometer for vacuum-ultraviolet wavelengths on the spacecraft Dynamics Explorer 1. For the initial analysis of observations available in 17 orbits distributed throughout the period, least-squares fits are computed for the observed exponential decrease in brightness with radial distance from the nucleus. Brightness at the nucleus increased from approx. 3 to 17 kR during the observing period. Preliminary analysis yields water production rates of approx. 3.6 x 10 to the 29th power and 1.9 x 10 to the 30th power molecules/sec on 1 and 29 January, respectively

The ionospheric response to interplanetary magnetic field variations: Evidence for rapid global change and the role of preconditioning in the magnetosphere

We have found observational evidence for a rapid communication of interplanetary magnetic field (IMF) changes to the global ionosphere and evidence for the state of the magnetosphere in the previous hour conditioning this response. These conclusions are drawn from a case study of sunward flow bursts on the nightside polar cap boundary observed by geomagnetically conjugate HF radars. The flow burst excitation consists of two factors: (1) At the time of the flow burst, the magnetosphere still held a memory of the stable and northward IMF period that had persisted up until 1 hour before the flow burst (internal condition). During the northward IMF period a theta aurora associated with a sunward flow channel was formed in the polar cap. After that the IMF turned southward, and the transpolar arc decayed antisunward. However, by the time of the flow burst (i.e., 1 hour after the IMF southward turning), the Sun-aligned arc had not yet completely vanished, and in the poleward expanded portion of the northern plasma sheet, there was still a remnant of the sunward flow channel susceptive to an external forcing. (2) One hour after the southward turning of the IMF a sharp IMF transition from southward to northward Bz impinged on the dayside magnetopause (external condition). On arriving at the dayside cusp ionosphere the Bz transition signal pervaded the entire polar cap ionosphere instantaneously (<1 min) and reached the nightside plasma sheet. There, the remnant of the sunward flow channel was reactivated by the Bz transition, and a sunward flow burst was observed first in the northern ionosphere and then in the southern ionosphere with a 7-min time delay. Thus the sunward flow burst represents a rapid global response of the ionosphere starting 2–3 min after the IMF change at the subsolar magnetopause

Advanced Coal-Fueled Gas Turbine Program

The objective of the original Request for Proposal was to establish the technological bases necessary for the subsequent commercial development and deployment of advanced coal-fueled gas turbine power systems by the private sector. The offeror was to identify the specific application or applications, toward which his development efforts would be directed; define and substantiate the technical, economic, and environmental criteria for the selected application; and conduct such component design, development, integration, and tests as deemed necessary to fulfill this objective. Specifically, the offeror was to choose a system through which ingenious methods of grouping subcomponents into integrated systems accomplishes the following: (1) Preserve the inherent power density and performance advantages of gas turbine systems. (2) System must be capable of meeting or exceeding existing and expected environmental regulations for the proposed application. (3) System must offer a considerable improvement over coal-fueled systems which are commercial, have been demonstrated, or are being demonstrated. (4) System proposed must be an integrated gas turbine concept, i.e., all fuel conditioning, all expansion gas conditioning, or post-expansion gas cleaning, must be integrated into the gas turbine system