Performance of recoverable single and multiple space tugs for missions beyond earth escape

A recoverable space tug launched by the space shuttle to provide the required post-orbital propulsion needed for placement of unmanned satellites is described. The space tug will also be used to launch interplanetary spacecraft from low earth orbit. The performance of single and multiple space tugs (in tandem) for launching spacecraft beyond earth escape is summarized. Trajectories are developed that allow recovery of the tugs whenever practical. The effects of important tug and trajectory parameters on performance are presented. It is concluded that a single tug can inject spacecraft to Mars or Venus and still be recovered. The use of several tugs in tandem can provide a significant increase in capability over the use of a single tug. The more difficult missions involve a mix of recovered and expended tugs

No-moving-part hybrid-synthetic jet actuator

In contrast to usual synthetic jets, the “hybrid-synthetic jets” of non-zero timemean nozzle mass flow rate are increasingly often considered for control of flow separation and/or transition to turbulence as well as heat and mass transfer. The paper describes tests of a scaled-up laboratory model of a new actuator version, generating the hybrid-synthetic jets without any moving components. Self-excited flow oscillation is produced by aerodynamic instability in fixed-wall cavities. The return flow in the exit nozzles is generated by jet-pumping effect. Elimination of the delicate and easily damaged moving parts in the actuator simplifies its manufacture and assembly. Operating frequency is adjusted by the length of feedback loop path. Laboratory investigations concentrated on the propagation processes taking place in the loop

Top 10 Law School Home Pages of 2012

For a fourth consecutive year, every website home page of every ABA-accredited law school is evaluated and ranked based on objective criteria. The goal is to identify well-executed sites adopting best practices. For the 2012 report, twenty-six elements are evaluated across these three categories: Design Patterns and Metadata, Accessibility and Validation, & Marketing and Communications. For 2012, there are four new elements, two prior elements have been combined, and one element was dropped. For 2012, forty-six schools now use the HTML5 doctype, which is up from thirteen in 2011 and just one in 2010. Eighteen schools achieve perfect scores in an adjusted web accessibility evaluation, which is a slight increase over previous years. One of the new elements awards points for use of Responsive Web Design practices, which is a page layout method that shifts the order and number of elements on a page, based on the screen size displaying the content. Our survey discovered fourteen home pages using responsive web design. As has been the case since this annual study launched in 2009, there is still no objective way to account for good taste. For interpreting these results, please decide for yourself whether any home page is greater or less than the sum of its evaluated elements

Evaluation of the HARDMAN comparability methodology for manpower, personnel and training

The methodology evaluation and recommendation are part of an effort to improve Hardware versus Manpower (HARDMAN) methodology for projecting manpower, personnel, and training (MPT) to support new acquisition. Several different validity tests are employed to evaluate the methodology. The methodology conforms fairly well with both the MPT user needs and other accepted manpower modeling techniques. Audits of three completed HARDMAN applications reveal only a small number of potential problem areas compared to the total number of issues investigated. The reliability study results conform well with the problem areas uncovered through the audits. The results of the accuracy studies suggest that the manpower life-cycle cost component is only marginally sensitive to changes in other related cost variables. Even with some minor problems, the methodology seem sound and has good near term utility to the Army. Recommendations are provided to firm up the problem areas revealed through the evaluation

Program for refan JT8D engine design, fabrication and test, phase 2

The objective of the JT8D refan program was to design, fabricate, and test certifiable modifications of the JT8D engine which would reduce noise generated by JT8D powered aircraft. This was to be accomplished without affecting reliability and maintainability, at minimum retrofit cost, and with no performance penalty. The mechanical design, engine performance and stability characteristics at sea-level and altitude, and the engine noise characteristics of the test engines are documented. Results confirmed the structural integrity of the JT8D-109. Engine operation was stable throughout the airplane flight envelope. Fuel consumption of the test engines was higher than that required to meet the goal of no airplane performance penalty, but the causes were identified and corrected during a normal pre-certification engine development program. Compared to the baseline JT8D-109 engine, the acoustically treated JT8D-109 engine showed noise reductions of 6 PNdB at takeoff and 11 PNdB at a typical approach power setting

A computer program for hydrostatic bearings including the effects of non-uniform film thickness and relative velocity for various methods of lubricant supply final technical report

Computer program for hydrostatic bearing - effects of nonuniform film thickness and lubricant suppl

Some properties of sulfoacetic acid and 3-sulfopropionic acid and their use as analytical masking agents

The values of Ka2 for sulfoacetic and 3-sulfopropionic acids were determined potentiometrically. The values are (8.6 ± 0.3) x 10-5 and (3.0 ± 0.1) x10-5, respectively. These values or Ka2 were much lower than those predicted by the Branch and Calvin equation for the calculation of values or pKa of derivatives of acetic acid

Turbine Engines for High-Speed Flight

This analysis investigates the application of gas turbine engines at a cruise Mach number of 4