Scanning afocal laser velocimeter projection lens system

A method and apparatus for projecting and focusing parallel laser light beams from a laser doppler velocimeter on a target area are described. The system includes three lenses. Two lenses work together as a fixed afocal lens combination. The third lens is a movable scanning lens. Parallel laser beams travel from the velocimeter through the scanning lens and through the afocal lens combination and converge, i.e., are focused, somewhere beyond. Moving the scanning lens relative to the fixed afocal combination results in a scanning of the focus area along the afocal combination's optical axis

Clevis joint for deployable space structures

This invention relates generally to pin clevis joints, and more particularly, to zero play pin clevis joints for connecting structural members of a deployable space structure. A joint includes a pin, a tang, and a shackle. The pin is tapered at the same angle as the bores extending through the projections of the shackle and the tang. A spring washer biases the tang onto the tapered sidewall of the pin. The invention solves the free play problem associated with deployable space structures by using a tapered pin which is held in tapered holes by the spring washers

Preloaded space structural coupling joints

A coupling device for tubular members of large truss structures with a locking collar being the only moving part is described. Each tubular member is constructed with an end bell section that has a belled flange with a mating face, and a necked area which is smaller in diameter than the tubular members to be joined. A split ring is affixed to each tubular member and is constructed so that when two tubular members are laterally moved into axial alignment and the collar is rotated over it, the split ring loads the joint with axial forces by pressing the belled flange mating surfaces together, and a preloading force is provided by the collar mating with a taper on the outside of the split rings. All free play is thereby removed by preloaded force. A major object is to provide an ability to remove and replace individual tubular members without disturbing other structural parts of a truss structure. An additional anticipated use of this joint is to couple high pressure fluid lines

New concepts in deployable beam structures

The design of deployable structures involves a complicated tradeoff of packaging efficiency, the overall mechanism associated with deploying and latching beam joints, and the requirements and complexity of the beam deployer/repacker. Three longeron deployable beams, controllable geometry beams, and hybrid deployable/erectable beam concepts are evaluated

Optical scanner

An optical scanner that sequentially focuses optical energy (light) at selected points in space is described. The essential component is a scanning wheel including several glass windows with each window having a different thickness. Due to this difference in thickness, the displacement of the emerging light from the incident light is different for each window. The scanner transmits optical energy to a point in space while at the same time receiving any optical energy generated at that point and then moves on to the next selected point and repeats this transmit and receive operation. It fills the need for a system that permits a laser velocimeter to rapidly scan across a constantly changing flow field in an aerodynamic test facility

Design considerations for joints in deployable space truss structures

All of the structures considered for the Control of Flexible Structures (COFS) flight experiments are deployable truss structures and their response will be dominated by the structural response of the joints. To prepare for these experiments some fundamental research work is being conducted in the Structures and Dynamics Division at LaRC which will provide insight into structurally efficient and predictable deployable truss joints. This work involves generic studies of the static and dynamic response of joints as well as the development of analytical models which can be used to predict the response of a large multijointed truss. In addition to the generic joint studies, the research effort encompasses the design and fabrication of a 20-meter long deployable truss beam for laboratory evaluation of its structural characteristics and correlation with developed prediction methods. The experimental results have indicated the importance of attention to detail in the design and fabrication of joints for deployable truss structures. The dimensional relations and material considerations for efficient pin-clevis joints have been outlined. Results of tests on the near-center latch are discussed

‘When the cage came up there was something crouched a-top of it’the haunted tales of L.T.C. Rolt - a contextual analysis

British writer and historian L.T.C. Rolt’s collection of ghost stories, Sleep No More was published in 1948. His short fiction deserves greater exposure. More than simply a ‘derivative imitation’ of what came before, one could argue the collection provides an end point for the Victorian and Edwardian ghostly tale. Whilst heavily influenced by, and indebted to, the works of Sheridan Le Fanu and M.R. James, Rolt’s tales assuredly re-shape the traditional ghost story from the outdated gothic settings of the past and the academic background of James’s works - the isolated country churches, foreign abbeys and country halls - into the more identifiable surroundings of post-war Britain with its steam trains, canals and factories. Gone too are Le Fanu’s country squires and James’s fusty antiquarians, replaced by railwaymen, steel-workers and motor-racing enthusiasts. It is into this recognisable world populated by ordinary characters that Rolt slips his unease. In doing so, he forges the way, alongside Fritz Leiber for the generation of ‘working-class’ or ‘blue-collar’ stories that follow. Beginning with a close analysis of the key fundamentals of a ghost story as laid down by M.R. James, and juxtaposing those against Rolt’s informative essay The Passing of the Ghost Story (1956) we can see how Rolt’s tales provide a distinctive connection between the traditional ghost stories of James and the industrial short horror fiction of Leiber. Rolt also sets a portion of his tales in isolated Welsh valleys and the Shropshire border country where he was raised. It is in these more wild and brooding locations, more aligned to the works of Algernon Blackwood and Arthur Machen, that his tales of ghosts and hauntings are transformed into unsettling, disorientating excursions where ‘angel satyrs’ stir

Predictions and measurements of isothermal flowfields in axisymmetric combustor geometries

Numerical predictions, flow visualization experiments and time-mean velocity measurements were obtained for six basic nonreacting flowfields (with inlet swirl vane angles of 0 (swirler removed), 45 and 70 degrees and sidewall expansion angles of 90 and 45 degrees) in an idealized axisymmetric combustor geometry. A flowfield prediction computer program was developed which solves appropriate finite difference equations including a conventional two equation k-epsilon eddy viscosity turbulence model. The wall functions employed were derived from previous swirling flow measurements, and the stairstep approximation was employed to represent the sloping wall at the inlet to the test chamber. Recirculation region boundaries have been sketched from the entire flow visualization photograph collection. Tufts, smoke, and neutrally buoyant helium filled soap bubbles were employed as flow tracers. A five hole pitot probe was utilized to measure the axial, radial, and swirl time mean velocity components