| Abstrakt: |
Drag is one of the aerodynamic forces that affect the performance of a sounding rocket. Accurate drag calculation is needed in order to accurately determine the performance of the rocket. To simplify the calculation, in many sounding rocket designs, analytical calculation for drag of a sounding rocket assumes the body has a smooth surface. However, due to manufacturing constraints, in most cases, some protuberances cause discontinuities in the rocket body. Bolts are an example of protuberances that exists on the structure joints of the rocket. These bolts disturb the local flow and create a local shock in supersonic speed, creating additional drag. The objective of this research is to investigate the drag contribution from the bolts used in the structure joints of RX-450. RX-450 is a sounding rocket prototype developed by the Research Organization for Aeronautics and Space, National Research and Innovation Agency, with a 458 mm in diameter and 7.18 m in total length. There are 48 bolts in motor tube joint with cap and 48 bolts in the motor tube joint with nozzle. The Computational Fluid Dynamics method is used to calculate the drag from the bolts. In this research, due to limited computational capacity, the model is limited to zero angle of attack, and free stream Mach number of 1.5, 2.0, 2.5, 3.0 and 3.5, which is the range of supersonic flight regime of RX-450. The result shows that these bolts create shocks which increased the pressure drag around the bolts. It is found that the bolts increased the drag of the rocket ranging from 8.34% to 9.55% at Mach number from 1.5 to 3.5. The maximum increment of drag occurred at a Mach number equal to 2.0. [ABSTRACT FROM AUTHOR] |
