3,732 research outputs found
Eclipse radius measurements
Methods for predicting the path edges and reducing observations of total solar eclipses for determining variations of the solar radius are described. Analyzed observations of the 1925 January eclipse show a 0.7 (arc second) decrease in the solar radius during the past fifty years
Dynamic stability and parametric resonance in cylindrical propellant tanks Final report
Dynamic stability and parametric resonance of longitudinally excited liquid propellant tank mode
Detailed pressure distribution measurements obtained on several configurations of an aspect-ratio-7 variable twist wing
Detailed pressure distribution measurements were made for 11 twist configurations of a unique, multisegmented wing model having an aspect ratio of 7 and a taper ratio of 1. These configurations encompassed span loads ranging from that of an untwisted wing to simple flapped wings both with and without upper-surface spoilers attached. For each of the wing twist configurations, electronic scanning pressure transducers were used to obtain 580 surface pressure measurements over the wing in about 0.1 sec. Integrated pressure distribution measurements compared favorably with force-balance measurements of lift on the model when the model centerbody lift was included. Complete plots and tabulations of the pressure distribution data for each wing twist configuration are provided
Low speed wind tunnel investigation of span load alteration, forward-located spoilers, and splines as trailing-vortex-hazard alleviation devices on a transport aircraft model
The effectiveness of a forward-located spoiler, a spline, and span load alteration due to a flap configuration change as trailing-vortex-hazard alleviation methods was investigated. For the transport aircraft model in the normal approach configuration, the results indicate that either a forward-located spoiler or a spline is effective in reducing the trailing-vortex hazard. The results also indicate that large changes in span loading, due to retraction of the outboard flap, may be an effective method of reducing the trailing-vortex hazard
Study of explosions in the NASA-MSC Vibration and Acoustic Test Facility /VATF/ Final report
Damage potential of titanium alloy pressure spheres relative to spacecraft vibration testin
Combining asteroid models derived by lightcurve inversion with asteroidal occultation silhouettes
Asteroid sizes can be directly measured by observing occultations of stars by
asteroids. When there are enough observations across the path of the shadow,
the asteroid's projected silhouette can be reconstructed. Asteroid shape models
derived from photometry by the lightcurve inversion method enable us to predict
the orientation of an asteroid for the time of occultation. By scaling the
shape model to fit the occultation chords, we can determine the asteroid size
with a relative accuracy of typically ~ 10%. We combine shape and spin state
models of 44 asteroids (14 of them are new or updated models) with the
available occultation data to derive asteroid effective diameters. In many
cases, occultations allow us to reject one of two possible pole solutions that
were derived from photometry. We show that by combining results obtained from
lightcurve inversion with occultation timings, we can obtain unique physical
models of asteroids.Comment: 33 pages, 45 figures, 4 tables, accepted for publication in Icaru
Wake vortex technology
A brief overview of the highlights of NASA's wake vortex minimization program is presented. The significant results of this program are summarized as follows: (1) it is technically feasible to reduce significantly the rolling upset created on a trailing aircraft; (2) the basic principles or methods by which reduction in the vortex strength can be achieved have been identified; and (3) an analytical capability for investigating aircraft vortex wakes has been developed
Contingency study for the third international Sun-Earth Explorer (ISEE-3) satellite
The third satellite of the international Sun-Earth Explorer program was inserted into a periodic halo orbit about L sub 1, the collinear libration point between the Sun and the Earth-Moon barycenter. A plan is presented that was developed to enable insertion into the halo orbit in case there was a large underperformance of the Delta second or third stage during the maneuver to insert the spacecraft into the transfer trajectory. After one orbit of the Earth, a maneuver would be performed near perigee to increase the energy of the orbit. A relatively small second maneuver would put the spacecraft in a transfer trajectory to the halo orbit, into which it could be inserted for a total cost within the fuel budget. Overburns (hot transfer trajectory insertions) were also studied
Doubly-periodic orbits in the Sun-Earth-Moon system
A series of periodic orbits in the Earth-Moon circular restricted problem of three bodies was found which is ideally suited for exploring the Earth's geomagnetic tail. The mean apsidal motion of the basic highly elliptical Earth orbit was maintained at about one degree per day by a sequence of lunar swingbys, keeping the apogees in the anti-Sun direction. The orbits were periodic in reference frames rotating at both lunar and solar rates. Apogee distances were alternately raised and lowered by the lunar swingby maneuvers. Several categories of these Sun-synchronous double lunar swingby orbits were identified. The strength and flexibility of this trajectory concept was demonstrated with real world simulations
- …