Descent Characteristics
Reynolds Number Regime
Relative Descent Dynamics
Booster Section
Assuming we are falling horizontally with flow conditions above the critical Reynolds number, we expect a drag coefficient (based on diameter) around 1.6. [1] This gives us a CdS of 0.53 m2, given a diameter of 6 in = 0.1524 m and a length of 85.73 in = 2.178 m (this neglects the fins). If we are falling axially, we expect a drag coefficient of around 0.8 [2]. Given a reference area of a circle with diameter 6 in (π*(0.0762m)2 = 0.0182 m2), we find that the CdS is 0.0146 m2.
It is difficult to predict in which configuration the booster will fall. On the one hand, if it falls horizontally, there will be greater drag-based restoring forces to counteract any perturbations to its configuration. On the other hand, if it falls axially, perturbations will have less of an effect due to smaller moment arms. This analysis is complicated by the fact that we are unsure of the rocket's orientation during deployment and the effect of altitude.
One way to predict things is to look at videos of drogue or tumble recovery experienced by other rockets. We have summarized the findings in the table below:
| Video Link | Falling Configuration | Notes |
|---|---|---|
| Tumble Recovery | Mostly horizontally, at a bit of an angle | |
| Therion Flight Test 1 | Mostly horizontally, at a bit of an angle, tumbles around a lot | Under drogue with similar drag to body |
Drogue
The drogue has a CdS of (this is at Mach 0.137) 0.662 m2.
Descent/Landing Rates
Resources
[1] DRAG OF CIRCULAR CYLINDERS FOR A WIDE RANGE OF REYNOLDS NUMBERS AND MACH NUMBERS
[2] Aerospaceweb.org, Drag of Cylinders and Cones