Rapid Prototyping for Aerospace Launch Vehicles

Initial studies of the aerodynamic characteristics of proposed launch vehicles can be made more accurately if lower cost, high-fidelity aerodynamic models are available for wind tunnel testing early in design phase. Rapid Prototyping (RP) is an emerging key technology for producing accurate parts directly from CAD models quickly, with little need of human intervention. Use of RP models was studied at the NASA Marshall Space Flight Center (MSFC). It was concluded that RP methods and materials can be used only for preliminary design studies and limited configurations because of the RP material properties that allow bending of models under higher loading conditions. The reported results and analysis were based on wind tunnel balances. These balances give total load on the body. Thus, there is a need for studying the pressure distribution, the wave pattern and the system behavior under high-speed conditions. In order to study the above goals, a blunt nose cone of a launch vehicle/ missile was tested which was made using the solid based RP method FDM, with a Mach number of 2.0. It is concluded that RP models can take the load at the Mach number 2.0 and also can capture the pressure distribution and wave pattern.Mechanical Engineerin

Recycling of RP Models by Solution - Casting Technique

Most of the Rapid Prototyping systems process polymeric materials for model making. Increased environmental concerns and waste minimization demands the recycle of these polymeric models. One way is to melt the models and cast it. However, in this method polymer degradation may occur leading to diminished functionality. In the present work a preliminary attempt has been made to reuse the polymer components by dissolving in a suitable solvent and casting the same into the required shape using soft tooling. Acrylonitrile Butadiene Styrene (ABS) polymer components, made by Fused Deposition Modeling (FDM) process were taken for the present studyMechanical Engineerin

Active Control of Flow through the Nozzles at Sonic Mach Number

ABSTRACT The effectiveness of micro jets to control the base pressure in suddenly expanded axi-symmetric ducts are studied experimentally. As an active control in the form of four micro jets of 1 mm orifice diameter located at 90 0 intervals along a pitch circle diameter of 1.3 times the nozzle exit diameter in the base region was employed. The Mach number of the present study is unity. The area ratio (ratio of area of suddenly expanded duct to nozzle exit area) studied are 2.56, 3.24, 4.84 and 6.25. The L/D ratio of the sudden expansion duct varies from 10 to 1. From the experimental results, it is found that the micro jets can serve as active controllers for base pressure. Further, the control effectiveness of the micro jets is getting enhanced under the influence of favourable pressure gradient. To study the effect of micro jets on the quality of flow in the enlarged duct wall pressure was measured and it is found that the micro jets do not disturb the flow field

ACTIVE CONTROL OF BASE PRESSURE IN SUDDENLY EXPANDED FLOW FOR AREA RATIO 4.84

Abstract: Airflow from convergent-divergent axi-symmetric nozzles expanded suddenly into circular duct of larger cross-sectional area than that of nozzle exit area are studied experimentally, focusing attention on the base pressure and the flow development in the enlarged duct. Micro-jets of 1 mm orifice diameter located at 90 0 intervals along a pitch circle diameter (pcd) 1.3 times the nozzle exit diameter were employed as the controller of the base pressure. The tests are conducted for Mach numbers 1.87, 2.2 and 2.58. The area ratio of the present study is 4.84. The length-to-diameter ratio of the suddenly expanded duct is varied from 10 to 1 and nozzle pressure ratio (NPR) in the range 3 to 11. It is found that the active control in the form of blowing through small orifices (micro jets) are effective in controlling the base pressure field and even do not augment the flow field in the duct. An increase of 45 percent in base pressure was achieved for certain combination of parameters of the present study