348 research outputs found
Full-scale Drag Tests of Landing Lamps
Drag tests were conducted in the N.A.C.A. full-scale wind tunnel on full-scale models of two Army Air Corps type A-6 landing lamps mounted on an 8 by 48 foot airfoil. Drag measurements were made with the lamps in the leading edge and attached to the lower surface at the 5 and 10 percent chord positions. The drag of the lamps when faired into the airfoil was also measured. The results show that at 100 miles per hour and at the angle of minimum drag of the airfoil the unaired lamps in the leading edge produced an increase in drag of 5.5 pounds and that the unaired lamps on the lower surface at either position increased the airfoil drag 22.5 pounds. These increases represent 6 and 24 percent of the minimum drag of the airfoil, respectively. Fairing the lamps into the airfoil reduced the drag of the lamps about 50 percent for the leading-edge position and about 60 percent for the two lower surface positions
Maneuverability Investigation of the F6C-3 Airplane with Special Flight Instruments
This investigation was made for the purpose of obtaining information on the maneuverability of the F6C-3 airplane. It is the first of a series of similar investigations to be conducted on a number of military airplanes for the purpose of comparing the abilities of these airplanes to maneuver, and also to establish a fund of quantitative data which may be used in formulating standards of comparison for rating the maneuverability of any airplane. A large part of this initial investigation was necessarily devoted to the development and trial of methods suitable for use in subsequent investigations of this nature. Air speed, angular velocity, linear acceleration, and position of the control surfaces were measured by instruments in the airplane during loops, push-downs, pull-outs from dives, pull-ups from level flight, barrel rolls, and spins. The coordinates of flight paths were deduced from the data whenever possible, and were checked in some cases by the use of a camera obscura. The results are given in curves showing the variation of the measured quantities with respect to time, and maximum values are tabulated
Full-scale Wind-tunnel and Flight Test of a Fairchild 22 Airplane Equipped with a Zap Flap and Zap Ailerons
A wing equipped with a Zap flap and Zap ailerons was tested on a Fairchild 22 airplane in the full-scale wind tunnel and in flight to determine the effect of the flaps and ailerons on the performance and the control characteristics of the airplane. The flaps were 0.30 of the wing chord and 0.83 of the wing span. Two sets of ailerons having equal areas but different proportions were tested, one set being 0.56 of the semispan and 0.18 of the chord and the other set being 0.46 of the semispan and 0.22 of the chord. The wind-tunnel tests showed that, when the ailerons and horizontal tail surfaces were removed, the flaps increased the maximum lift coefficient from 1.48 to 2.39. In flight, the fully deflected flaps decreased the minimum speed from 48.2 to 38.8 miles per hour. The take-off and landing distances were both reduced by the flaps. The wind-tunnel tests showed the ailerons to increase the drag coefficient, at a lift coefficient and Reynolds Number corresponding to the high speed of the airplane, from 0.0432 to 0.0498 and 0.0514, the 0.46 semispan ailerons giving the highest drag. In the flight tests both sets of ailerons were found to give satisfactory rolling action in the normal-flight range. They required relatively large stick forces for their operation, however, and the variation of the forces with aileron deflection was not linear
Full-scale Wind-tunnel and Flight Tests of a Fairchild 22 Airplane Equipped with a Fowler Flap
Full-scale wind-tunnel and flight tests were made of a Fairchild 22 airplane equipped with a Fowler flap to determine the effect of the flap on the performance and control characteristics of the airplane. In the wind-tunnel tests of the airplane with the horizontal tail surfaces removed, the flap was found to increase the maximum lift coefficient from 1.27 to 2.41. In the flight test, the flap was found to decrease the minimum speed from 58.8 to 44.4 miles per hour. The required take-off run to attain an altitude of 50 feet was reduced from 935 feet to 700 feet by the use of the flap, the minimum distance being obtained with five-sixths full deflection. The landing run from a height of 50 feet was reduced one-third. The longitudinal and directional control was adversely affected by the flap, indicating that the design of the tail surfaces is more critical with a flapped than a plain wing
Vascular uptake of rehydration fluids in hypohydrated men at rest and exercise
The purpose of this study was to formulate and to evaluate rehydration drinks, which would restore total body water and plasma volume (PV), for astronauts to consume before and during extravehicular activity, a few hours before reentry, and immediately after landing. In the first experiment (rest, sitting), five healthy men (23-41 yr), previously dehydrated for 24 hr., drank six (1a, 2, 4, 5, 6, 7) fluid formulations (one each at weekly intervals) and then sat for 70 min. Pre-test PV were measured with Evans blue dye and changes in PV were calculated with the hematocrit-hemoglobin transformation equation. This rest experiment simulated hypohydrated astronauts preparing for reentry. The second experiment (exercise, supine) followed the same protocol except four healthy men (30-46 yr) worked for 70 min. in the supine position on a cycle ergometer at a mean load of 71+/-1 percent of their peak aerobic work capacity. This exercise experiment simulated conditions for astronauts with reduced total body water engaging in extravehicular activity
Origin and evolution of the light nuclides
After a short historical (and highly subjective) introduction to the field, I
discuss our current understanding of the origin and evolution of the light
nuclides D, He-3, He-4, Li-6, Li-7, Be-9, B-10 and B-11. Despite considerable
observational and theoretical progress, important uncertainties still persist
for each and every one of those nuclides. The present-day abundance of D in the
local interstellar medium is currently uncertain, making it difficult to infer
the recent chemical evolution of the solar neighborhood. To account for the
observed quasi-constancy of He-3 abundance from the Big Bang to our days, the
stellar production of that nuclide must be negligible; however, the scarce
observations of its abundance in planetary nebulae seem to contradict this
idea. The observed Be and B evolution as primaries suggests that the source
composition of cosmic rays has remained quasi-constant since the early days of
the Galaxy, a suggestion with far reaching implications for the origin of
cosmic rays; however, the main idea proposed to account for that constancy,
namely that superbubbles are at the source of cosmic rays, encounters some
serious difficulties. The best explanation for the mismatch between primordial
Li and the observed "Spite-plateau" in halo stars appears to be depletion of Li
in stellar envelopes, by some yet poorly understood mechanism. But this
explanation impacts on the level of the recently discovered early ``Li-6
plateau'', which (if confirmed), seriously challenges current ideas of cosmic
ray nucleosynthesis.Comment: 18 pages, 9 figs. Invited Review in "Symposium on the Composition of
Matter", honoring Johannes Geiss on the occasion of his 80th birthday
(Grindelwald, Switzerland, Sept. 2006), to be published in Space Science
Series of ISS
Effect of Finite Mass on Primordial Nucleosynthesis
We have calculated the small effect of finite nucleon mass on the
weak-interaction rates that interconvert protons and neutrons in the early
Universe. We have modified the standard code for primordial nucleosynthesis to
include these corrections and find a small, systematic increase in the 4He
yield, , depending slightly on the
baryon-to-photon ratio. The fractional changes in the abundances of the other
light elements are a few percent or less for interesting values of the
baryon-to-photon ratio.Comment: 15 pages, 8 figures, uses psfig.st
Thermohaline Mixing and its Role in the Evolution of Carbon and Nitrogen Abundances in Globular Cluster Red Giants: The Test Case of Messier 3
We review the observational evidence for extra mixing in stars on the red
giant branch (RGB) and discuss why thermohaline mixing is a strong candidate
mechanism. We recall the simple phenomenological description of thermohaline
mixing, and aspects of mixing in stars in general. We use observations of M3 to
constrain the form of the thermohaline diffusion coefficient and any associated
free parameters. This is done by matching [C/Fe] and [N/Fe] along the RGB of
M3. After taking into account a presumed initial primordial bimodality of
[C/Fe] in the CN-weak and CN-strong stars our thermohaline mixing models can
explain the full spread of [C/Fe]. Thermohaline mixing can produce a
significant change in [N/Fe] as a function of absolute magnitude on the RGB for
initially CN-weak stars, but not for initially CN-strong stars, which have so
much nitrogen to begin with that any extra mixing does not significantly affect
the surface nitrogen composition.Comment: 33 Pages, 10 Figures. Accepted for publication in The Astrophysical
Journa
The N Enrichment and Supernova Ejection of the Runaway Microquasar LS 5039
We present an investigation of new optical and ultraviolet spectra of the
mass donor star in the massive X-ray binary LS 5039. The optical band spectral
line strengths indicate that the atmosphere is N-rich and C-poor, and we
classify the stellar spectrum as type ON6.5 V((f)). The N-strong and C-weak
pattern is also found in the stellar wind P Cygni lines of N V 1240 and C IV
1550. We suggest that the N-enrichment may result from internal mixing if the
O-star was born as a rapid rotator, or the O-star may have accreted N-rich gas
prior to a common-envelope interaction with the progenitor of the supernova. We
re-evaluated the orbital elements to find an orbital period of P=4.4267 +/-
0.0010 d. We compared the spectral line profiles with new non-LTE,
line-blanketed model spectra, from which we derive an effective temperature
T_eff = 37.5 +/- 1.7 kK, gravity log g = 4.0 +/- 0.1, and projected rotational
velocity V sin i = 140 +/- 8 km/s. We fit the UV, optical, and IR flux
distribution using a model spectrum and extinction law with parameters E(B-V)=
1.28 +/- 0.02 and R= 3.18 +/- 0.07. We confirm the co-variability of the
observed X-ray flux and stellar wind mass loss rate derived from the H-alpha
profile, which supports the wind accretion scenario for the X-ray production in
LS 5039. Wind accretion models indicate that the compact companion has a mass
M_X/M_sun = 1.4 +/- 0.4, consistent with its identification as a neutron star.
The observed eccentricity and runaway velocity of the binary can only be
reconciled if the neutron star received a modest kick velocity due to a slight
asymmetry in the supernova explosion (during which >5 solar masses was
ejected).Comment: 38 pages, 9 figures; 2004, ApJ, 600, Jan. 10 issue, in press
Discussion revised thanks to comments from P. Podsiadlowsk
The Role of Thermohaline Mixing in Intermediate- and Low-Metallicity Globular Clusters
It is now widely accepted that globular cluster red giant branch stars owe
their strange abundance patterns to a combination of pollution from progenitor
stars and in situ extra mixing. In this hybrid theory a first generation of
stars imprint abundance patterns into the gas from which a second generation
forms. The hybrid theory suggests that extra mixing is operating in both
populations and we use the variation of [C/Fe] with luminosity to examine how
efficient this mixing is. We investigate the observed red giant branches of M3,
M13, M92, M15 and NGC 5466 as a means to test a theory of thermohaline mixing.
The second parameter pair M3 and M13 are of intermediate metallicity and our
models are able to account for the evolution of carbon along the RGB in both
clusters. Although, in order to fit the most carbon-depleted main-sequence
stars in M13 we require a model whose initial [C/Fe] abundance leads to a
carbon abundance lower than is observed. Furthermore our results suggest that
stars in M13 formed with some primary nitrogen (higher C+N+O than stars in M3).
In the metal-poor regime only NGC 5466 can be tentatively explained by
thermohaline mixing operating in multiple populations. We find thermohaline
mixing unable to model the depletion of [C/Fe] with magnitude in M92 and M15.
It appears as if extra mixing is occurring before the luminosity function bump
in these clusters. To reconcile the data with the models would require first
dredge-up to be deeper than found in extant models.Comment: 13 Pages, 3 figures. Accepted for publication in the Astrophysical
Journa
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