![]() The fits are done for 5 functions: Conic, Parabola, Elliptical, Sears-Haack and Tangent Ogive. We assume this to be linear so that the constant varies according to a Is assumed to be a constant (generally between 0.05 and 0.2) that varies slightly between Similarly, the linearįits to M=1.05 to M=1.2 also give two coefficient m and b which are also fit to That work vary for different nosecone models but it tends to fit:įor a the function a exp(x^b), for b simply an average (a constant), for c the logisticįormula which is 1/(1 bexp(-c x)), where in all cases x = L/D. Relate the variation of the coefficients in L/D to the variation over speed. Then the variation in the coefficients a, b, and c are fit which The fit that is done generally is the Hoerlįunction which is:Cd = a b^xx^c, where a, b, c are all constants that vary with L/D. The finalįit is in segment from M=1.2 onwards. M=1.2 so it is not possible to have a good fit from M>1.05(ie and ). These curves tend to have a very steep fall off from M=1 to Is also intepreted linearly from M=1.05 to M=1.2 (essentially a linear interpolation The next segment is a very steep fall off to M=1.2 and Segment is the easiest and is interpolated linearlyįrom L/D=1 to L/D=3. In each of these sections the curves vary as aįunction of M and of L/D ratio. These curves can be divided into three segments from M=0 to M=1.05, from M=1.05 Note that this drag also does not include Is a fit of total drag which includes the body drag plus the fricton drag and base drag. Nosecone) and for various mach speeds were produced using HyperCFD code. ![]() The drag coefficient CD functions for various L/D (length of nosecone/ max diameter of ![]() I have used his results essentially as a look up The HyperCFD code is developed by John Cipolla and can be obtained from his website at: The drag due to various length bodies because it does not seem to be a large effect. Note that this is a fit of total drag which includes the body drag plus the fricton dragĪnd base drag. The calculation uses the formula from the book: Mandell, Gordon K., George J. Major modification to code to include the drag caused by the fins. Made modifications in layout and size of frame and the way buttons are displayed. Instread the area is independently calculated on the fin height, tip chord and the root chord. Note that the Sweep Angle is not used in the code. "Estimating the dynamic and aerodynamic parameters of passively controlled high power rockets for flight simulation." Cambridge Rocketry (2009). It confirms the techniques described in: Box, Simon, Christopher M. The method is described in the hard to get book: Topics in Advanced Model Rocketry by (Thanks for Bruno Berger from the Swiss Propulsion Laboratory GmbH (LLC) for scanning the chapter on drag!). This is the United States Air Force Stability and Control (DATCOM being an acronymįor Data Compendium). Included fin drag which is taken from the DATCOM method. To turn off the fins just place zeroes for all the fin parameters.
0 Comments
Leave a Reply. |