479 research outputs found
Effects of airplane characteristics and takeoff noise and field length constraints on engine cycle selection for a Mach 2.32 cruise application
Sideline noise and takeoff field length were varied for two types of Mach 2.32 cruise airplane to determine their effect on engine cycle selection. One of these airplanes was the NASA/Langley-LTV arrow wing while the other was a Boeing modified delta-plus-tail derived from the earlier 2707-300 concept. Advanced variable cycle engines were considered. A more conventional advanced low bypass turbofan engine was used as a baseline for comparison. Appropriate exhaust nozzle modifications were assumed, where needed, to allow all engines to receive either an inherent co-annular or annular jet noise suppression benefit. All the VCE's out-performed the baseline engine by substantial margins in a design range comparison, regardless of airplane choice or takeoff restrictions. The choice among the three VCE's considered, however, depends on the field length, noise level, and airplane selected
Airplane size and staging effects on SST cruise sonic boom
Performance requirements and economic costs to reduce cruise sonic boom of supersonic transpor
Potential of liquid-methane fuel for Mach-3 commercial supersonic transports
Liquid methane fuel for commercial fixed arrow wing supersonic transport
Component test program for variable-cycle engines
Variable cycle engine (VCE) concepts for a supersonic cruise aircraft were studied. These VCE concepts incorporate unique critical components and flow path arrangements that provide good performance at both supersonic and subsonic cruise and appear to be economically and environmentally viable. Certain technologies were identified as critical to the successful development of these engine concepts and require considerable development and testing. The feasibility and readiness of the most critical VCE technologies, was assessed, a VCE component test program was initiated. The variable stream control engine (VSCE) component test program, tested and evaluated an efficient low emission duct burner and a quiet coannular ejector nozzle at the rear of a rematched F100 engine
Comparison of parametric duct-burning turbofan and non-afterburning turbojet engines in a Mach 2.7 transport
A parametric study was made of duct-burning turbofan and suppressed dry turbojet engines installed in a supersonic transport. A range of fan pressure ratios was considered for the separate-flow-fan engines. The turbofan engines were studied both with and without jet noise suppressors. Single- as well as dual-stream suppression was considered. Attention was concentrated on designs yielding sideline noises of FAR 36 (108 EPNdB) and below. Trades were made between thrust and wing area for a constant takeoff field length. The turbofans produced lower airplane gross weights than the turbojets at FAR 36 and below. The advantage for the turbofans increased as the sideline noise limit was reduced. Jet noise suppression, especially for the duct stream, was very beneficial for the turbofan engines as long as duct burning was permitted during takeoff. The maximum dry unsuppressed takeoff mode, however, yielded better results at extremely low noise levels. Noise levels as low as FAR 36-11 EPNdB were obtained with a turbofan in this takeoff mode, but at a considerable gross weight penalty relative to the best FAR 36 results
NASA research in supersonic propulsion: A decade of progress
A second generation, economically viable, and environmentally acceptable supersonic aircraft is reviewed. Engine selection, testbed experiments, and noise reduction research are described
Fuel savings potential of the NASA Advanced Turboprop Program
The NASA Advanced Turboprop (ATP) Program is directed at developing new technology for highly loaded, multibladed propellers for use at Mach 0.65 to 0.85 and at altitudes compatible with the air transport system requirements. Advanced turboprop engines offer the potential of 15 to 30 percent savings in aircraft block fuel relative to advanced turbofan engines (50 to 60 percent savings over today's turbofan fleet). The concept, propulsive efficiency gains, block fuel savings and other benefits, and the program objectives through a systems approach are described. Current program status and major accomplishments in both single rotation and counter rotation propeller technology are addressed. The overall program from scale model wind tunnel tests to large scale flight tests on testbed aircraft is discussed
Design point study of auxiliary airbreathing engines for a space shuttle
Design analysis of auxiliary air breathing engines for space shuttle
Influence of Collision Cascade Statistics on Pattern Formation of Ion-Sputtered Surfaces
Theoretical continuum models that describe the formation of patterns on
surfaces of targets undergoing ion-beam sputtering, are based on Sigmund's
formula, which describes the spatial distribution of the energy deposited by
the ion. For small angles of incidence and amorphous or polycrystalline
materials, this description seems to be suitable, and leads to the classic BH
morphological theory [R.M. Bradley and J.M.E. Harper, J. Vac. Sci. Technol. A
6, 2390 (1988)]. Here we study the sputtering of Cu crystals by means of
numerical simulations under the binary-collision approximation. We observe
significant deviations from Sigmund's energy distribution. In particular, the
distribution that best fits our simulations has a minimum near the position
where the ion penetrates the surface, and the decay of energy deposition with
distance to ion trajectory is exponential rather than Gaussian. We provide a
modified continuum theory which takes these effects into account and explores
the implications of the modified energy distribution for the surface
morphology. In marked contrast with BH's theory, the dependence of the
sputtering yield with the angle of incidence is non-monotonous, with a maximum
for non-grazing incidence angles.Comment: 12 pages, 13 figures, RevTe
Neutron Structure Functions
Neutron structure functions can be extracted from proton and deuteron data
and a representation of the deuteron structure. This procedure does not require
DIS approximations or quark structure assumptions. We find that the results
depend critically on properly accounting for the Q^2 dependence of proton and
deuteron data. We interpolate the data to fixed Q^2, and extract the ratio of
neutron to proton structure functions. The extracted ratio decreases with
increasing x, up to x \approx 0.9, while there are no data available to
constrain the behavior at larger x.Comment: 16 pages, 6 figure
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