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| Variable | Length (in inches) | Description |
|---|---|---|
| hmp | 57.4 | Height of the mission package from nose cone tip to the end of the airframe |
| lmp | 14.5 | Depth into the cup |
| lfc | 7.6 | Depth of booster coupling section |
| hfc | 86.23 | Total height of booster including coupling section. |
| RB | 7.5 | Height of the main deployment bag, not including flaps (should make sure there is enough margin on relevant constraint(s)). |
| DM | 114 (9.5 ft) | Diameter of the main parachute |
| RM | 80.6 | Height of the main parachute (found using 0.707 aspect ratio): RM = DM*0.707 |
| SM | 126 | Length of shroud lines on the main parachute (may change when we update the main) |
| RD | 31 | Height of the drogue parachute (measured 2/15/2018) |
| SD | 100 | Vertical length (accounts for confluence angle) of the drogue shroud lines. Taken from the DGB parameters spreadsheet. |
| FD | 17 | Forebody diameter used for drogue parachute shock cord calculation. Please see the extended note on calculation below. |
| DD | 38 | Disk diameter of the drogue parachute. Taken from the DGB Parameters spreadsheet. |
| HTD | 2.7 | Height of the Tender Descender, including 1.5 quicklinks. (Since two Tender Descenders will be used in the calculation below, this will yield the appropriate length) |
Constraints and Calculations v2.0
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| Constraint | Description |
|---|---|
| WC,D > RB | The line connecting the top of the main chute canopy to the inside of the deployment bag must be long enough such that the main parachute is not stuck inside the deployment bag upon full line extension. |
| WA,H > WA,E,F,G + RD + SD + lfc | When lines between the mission package and fin can are fully extended, the drogue parachute must be within the airstream. |
| WA,H > lmp + hmp + lfc | Assuming full line extension, the mission package and booster section should not hit one another during descent. This neglects the effect of drag on these sections and their respective masses. |
| WA,E,F,G - lmp > 8.5*FD- SD | This constraint reduces the impact of forebody wake on the drogue parachute during drogue descent. Please see the extended note below on the calculation of forebody diameter. We subtract the vertical height of the shroud lines to reach a total canopy distance of ~9 forebody diameters.1 |
| WE,F + 2*HTD= 1.5*RB | Placing the junction between the tender descender (TD) and the main chute load paths at the edge of the mission package reduces the likelihood that the main parachute will enter the airstream prior to the designated release altitude of 2,000 ft. |
| WA,E |
Note on Drogue Forebody Diameter
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