70,170 research outputs found
Summary of Apollo and Lunar Logistics System Plans
The basic mission objective of Project Apollo is to land men on the Moon and return them to Earth at the earliest practicable date. The Apollo crew will consist of three men, two of whom will land on the surface of the Moon, conduct surface operations for up to 24 hr, and then rejoin the third crew member in lunar orbit for return to Earth. Initial Apollo spacecraft capabilities will require the early landings to be within +or-lO deg of the lunar equator on the visible side of the Moon, with preference for landing sites in the leading quadrant (between 270 and 360 deg lunar longitude). As presently planned, the Apollo spacecraft will be capable of carrying approximately 200 lb of scientific equipment to the lunar surface and of bringing approximately 80 lb of lunar material back to Earth. A detailed plan for utilization of crew capabilities while on the lunar surface is not expected to be complete for some time. The first Apollo lunar mission is now scheduled for the late 1960's with additional launches planned at reasonable intervals.
An associated solvent theory of polymer solutions
Association model theory for thermodynamic properties of nonpolar polymer mixtures with polar solven
Modification of an astronaut's mock up tool kit Final report
Design and tests of astronauts tool kit and tools for in-flight space maintenanc
Identifying Compact Symmetric Objects in the Southern Sky
We present results of multifrequency polarimetric VLBA observations of 20
compact radio sources. The observations represent the northern and southern
extensions of a large survey undertaken to identify Compact Symmetric Objects
(CSOs) Observed in the Northern Sky (COINS). CSOs are young radio galaxies
whose jet axes lie close to the plane of the sky, and whose appearance is
therefore not dominated by relativistic beaming effects. The small linear sizes
of CSOs make them valuable for studies of both the evolution of radio galaxies
and testing unified schemes for active galactic nuclei (AGN). In this paper we
report on observations made of 20 new CSO candidates discovered in the northern
and southern extremities of the VLBA Calibrator Survey. We identify 4 new CSOs,
and discard 12 core-jet sources. The remaining 4 sources remain candidates
pending further investigation. We present continuum images at 5 GHz and 15 GHz
and, where relevant, images of the polarized flux density and spectral index
distributions for the 8 new CSOs and CSO candidates.Comment: accepted to Ap
Research in far ultraviolet filtering for space optical systems
Design and fabrication of multilayer interference filters for ultraviole
Analytical design and evaluation of an active control system for helicopter vibration reduction and gust response alleviation
An analytical study was conducted to define the basic configuration of an active control system for helicopter vibration and gust response alleviation. The study culminated in a control system design which has two separate systems: narrow band loop for vibration reduction and wider band loop for gust response alleviation. The narrow band vibration loop utilizes the standard swashplate control configuration to input controller for the vibration loop is based on adaptive optimal control theory and is designed to adapt to any flight condition including maneuvers and transients. The prime characteristics of the vibration control system is its real time capability. The gust alleviation control system studied consists of optimal sampled data feedback gains together with an optimal one-step-ahead prediction. The prediction permits the estimation of the gust disturbance which can then be used to minimize the gust effects on the helicopter
Spectral methods for the wave equation in second-order form
Current spectral simulations of Einstein's equations require writing the
equations in first-order form, potentially introducing instabilities and
inefficiencies. We present a new penalty method for pseudo-spectral evolutions
of second order in space wave equations. The penalties are constructed as
functions of Legendre polynomials and are added to the equations of motion
everywhere, not only on the boundaries. Using energy methods, we prove
semi-discrete stability of the new method for the scalar wave equation in flat
space and show how it can be applied to the scalar wave on a curved background.
Numerical results demonstrating stability and convergence for multi-domain
second-order scalar wave evolutions are also presented. This work provides a
foundation for treating Einstein's equations directly in second-order form by
spectral methods.Comment: 16 pages, 5 figure
Cross-correlation Tomography: Measuring Dark Energy Evolution with Weak Lensing
A cross-correlation technique of lensing tomography is presented to measure
the evolution of dark energy in the universe. The variation of the weak lensing
shear with redshift around massive foreground objects like bright galaxies and
clusters depends solely on ratios of angular diameter distances. Use of the
massive foreground halos allow us to compare relatively high, linear shear
values in the same part of the sky, thus largely eliminating the dominant
source of systematic error in cosmological weak lensing measurements. The
statistic we use does not rely on knowledge of the foreground mass distribution
and is only shot-noise limited. We estimate the constraints that deep lensing
surveys with photometric redshifts can provide on the dark energy density
Omega, the equation of state parameter w and its redshift derivative w'. The
accuracies on w and w' are: sigma(w) ~ 0.02 fsky^{-1/2} and sigma(w') ~ 0.05
fsky^{-1/2}, where fsky is the fraction of sky covered by the survey and
sigma(Omega)=0.03 is assumed in the marginalization. Combining our
cross-correlation method with standard lensing tomography, which has
complementary degeneracies, will allow measurement of the dark energy
parameters with significantly better accuracy.Comment: 5 pages, 2 figures, submitted to PRL. Error in shear signal corrected
- parameter constraints about a factor of 2 wors
- …