Wind tunnel investigation of rotor lift and propulsive force at high speed: Data analysis

The basic test data obtained during the lift-propulsive force limit wind tunnel test conducted on a scale model CH-47b rotor are analyzed. Included are the rotor control positions, blade loads and six components of rotor force and moment, corrected for hub tares. Performance and blade loads are presented as the rotor lift limit is approached at fixed levels of rotor propulsive force coefficients and rotor tip speeds. Performance and blade load trends are documented for fixed levels of rotor lift coefficient as propulsive force is increased to the maximum obtainable by the model rotor. Test data is also included that defines the effect of stall proximity on rotor control power. The basic test data plots are presented in volumes 2 and 3

Experimental Investigations of Elastic Tail Propulsion at Low Reynolds Number

A simple way to generate propulsion at low Reynolds number is to periodically oscillate a passive flexible filament. Here we present a macroscopic experimental investigation of such a propulsive mechanism. A robotic swimmer is constructed and both tail shape and propulsive force are measured. Filament characteristics and the actuation are varied and resulting data are quantitatively compared with existing linear and nonlinear theories

Investigation of rotor blade element airloads for a teetering rotor in the blade stall regime (second wind tunnel test)

A test was conducted in the NASA-Ames 7 x 10 ft low speed wind tunnel on a seven-foot diameter model of a teetering rotor. The objectives of the test were: (1) acquire pressure data for correlation with laser and flow visualization measurements; (2) explore rotor propulsive force limits by varying the advance ratio at constant lift and propulsive force coefficients; (3) obtain additional data to define the differences between teetering and articulated rotors; and (4) verify the acceleration sensitivity of experimental transducers. Results are presented

Electrostatic Solar Sail: A Propellantless Propulsion Concept for an Interstellar Probe Mission

The propulsion of an electrostatic solar sail (E Sail) is obtained by extracting momentum from the solar wind through electrostatic repulsion of the positively charged solar wind ions (see Figure 1). The positively charged solar wind protons are deflected by the electric field created around the tethers.This electric field grows in diameter as the spacecraft moves away from the Sun, therefore the E Sail effective area grows. The growth of the E-Sail effective area allows the propulsive force to decrease as 1/r up to distances of 20 AU as it moves away from the Sun, unlike solar sail propulsion whose thrust decreases as 1/r 2 but only to distances of 5AU. This propulsive force is created without using propellant and, therefore, E-sail avoids both the mass and complexity of chemical rockets (that require large amounts of propellant, propellant storage tanks, plumbing, valves, and insulation)

Installed performance assessment of a boundary layer ingesting distributed propulsion system at design point

Boundary layer ingesting systems have been proposed as a concept with great potential for reducing the fuel consumption of conventional propulsion systems and the overall drag of an aircraft. These studies have indicated that if the aerodynamic and efficiency losses were minimised, the propulsion system demonstrated substantial power consumption benefits in comparison to equivalent propulsion systems operating in free stream flow. Previously assessed analytical methods for BLI simulation have been from an uninstalled perspective. This research will present the formulation of an rapid analytical method for preliminary design studies which evaluates the installed performance of a boundary layer ingesting system. The method uses boundary layer theory and one dimensional gas dynamics to assess the performance of an integrated system. The method was applied to a case study of the distributed propulsor array of a blended wing body aircraft. There was particular focus on assessment how local flow characteristics influence the performance of individual propulsors and the propulsion system as a whole. The application of the model show that the spanwise flow variation has a significant impact on the performance of the array as a whole. A clear optimum design point is identified which minimises the power consumption for an array with a fixed configuration and net propulsive force requirement. In addition, the sensitivity of the system to distortion related losses is determined and a point is identi ed where a conventional free-stream propulsor is the lower power option. Power saving coefficient for the configurations considered is estimated to lie in the region of 15%

Investigation of a Compound Helicopter Flying the Depart and Abort Mission Task Element

The next generation of rotorcraft will have to satisfy the appropriate handling qualities requirements before entering service. Many of these vehicles will operate at significantly greater speeds than the conventional helicopter and will therefore have different capabilities than current helicopters. Due to the different capabilities of the compound helicopter, it is possible that new Mission Task Elements (MTEs) need to be developed to assess the handling qualities of this type of helicopter. It is also possible that existing MTEs may be suitable without modification. Overall, it seems necessary to review the US Army’s current handling qualities specification, ADS-33, and determine the suitability of the current MTEs for compound vehicles. The broad aim of the paper is to assess the performance of compound helicopter during manoeuvring flight. More specifically, a simulation study of a compound helicopter flying the Depart and Abort ADS-33 Mission Task Element. There are two objectives: firstly the capabilities of the compound vehicle is compared with those of a conventional helicopter, and secondly, the suitability of the current Depart and Abort MTE, for compound vehicles, is assessed. The results of the research study highlight the capability of compound helicopters in low speed acceleration manoeuvres. These results can be used to redefine low speed acceleration manoeuvres in the new update to the ADS-33 specification. The results also indicate some information about the potential design issues with the compound helicopter

Lateral displacement system for separated rocket stages Patent

Development of remotely controlled shaped charge for lateral displacement of rocket stages after separatio

Medusan Morphospace: Phylogenetic Constraints, Biomechanical Solutions, and Ecological Consequences

Medusae were the earliest animals to evolve muscle-powered swimming in the seas. Although medusae have achieved diverse and prominent ecological roles throughout the world\u27s oceans, we argue that the primitive organization of cnidarian muscle tissue limits force production and, hence, the mechanical alternatives for swimming bell function. We use a recently developed model comparing the potential force production with the hydrodynamic requirements of jet propulsion, and conclude that jet production is possible only at relatively small bell diameters. In contrast, production of a more complex wake via what we term rowing propulsion permits much larger sizes but requires a different suite of morphological features. Analysis of morphometric data from all medusan taxa independently confirms size-dependent patterns of bell forms that correspond with model predictions. Further, morphospace analysis indicates that various lineages within the Medusozoa have proceeded along either of two evolutionary trajectories. The first alternative involved restriction of jet-propelled medusan bell diameters to small dimensions. These medusae may be either solitary individuals (characteristic of Anthomedusae and Trachymedusae) or aggregates of small individual medusan units into larger colonial forms (characteristic of the nectophores of many members of the Siphonophorae). The second trajectory involved use of rowing propulsion (characteristic of Scyphozoa and some hydromedusan lineages such as the Leptomedusae and Narcomedusae) that allows much larger bell sizes. Convergence on either of the differing propulsive alternatives within the Medusozoa has emerged via parallel evolution among different medusan lineages. The distinctions between propulsive modes have important ecological ramifications because swimming and foraging are interdependent activities for medusae. Rowing swimmers are characteristically cruising predators that select different prey types from those selected by jet-propelled medusae, which are predominantly ambush predators. These relationships indicate that the different biomechanical solutions to constraints on bell function have entailed ecological consequences that are evident in the prey selection patterns and trophic impacts of contemporary medusan lineages