Reefing Parachute Research
9/15/2024
Goals:
Develop a reefing parachute that successfully deploys and efficiently controls rocket flight/descent.
Purpose:
Condensing two parachutes (drogue + main) into a singular parachute that can perform the actions of both.
Skirt Reefing:
- controls canopy shape by routing a reefing line through reefing rings attached to the skirt of the canopy
Suspension-line reefing:
- controls the canopy shape by tying all the suspension lines together at some point between the canopy and the payload
Canopy reefing:
🦑: Not a fan of reefing the suspension lines as it seems there can be issues of it sliding down which could make the parachute expand slowly before the proper time. I would be more interested in looking at skirt reefing primarily and then canopy reefing. Canopy reefing could (negligibly) experience the same issues as suspension line reefing but the effects seem to be minimized by the parachute itself.
Line cutters:
https://www.apogeerockets.com/Electronics_Payloads/Dual-Deployment
https://www.tinderrocketry.com/the-mako-para-cord-cutter
https://www.tinderrocketry.com/the-piranha-cutter
Line Material:
Open ended, nothing specific is used from what it seems. Obviously needs to be cut-able by the line cutter used.
9/15/2024
Lines Diagram:
Assumes separation point is between the MPT and nosecone. Also assumes a skirt-reefing method where the line cutter is attached with lines/avionics wiring to the MPT. The reefing line remains attached to the parachute after the line is cut, so no components should fully separate from the rocket at any point.
10/3/2024
Parachute sizing was found using the drag force equation at the bottom left corner of figure 6. Putting in average assumed values resulted into a previously made spreadsheet calculator resulted in a total diameter of roughly 8 feet and a reefed diameter of roughly 3 feet.
Figure 6 Spreadsheet calculator and values used
Using the values in the spreadsheet, the shock force was found on OSCalc as shown in figure 7. For the drogue opening at 30,000ft, the upper bound of force is calculated to be 303.2 slugs*ft/s^2
Figure 7 OSCalc results
10/06/2024
We developed a concept for the reefing skirt.
Our concept is to stitch webbing onto the existing shroud line connections at the bottom edge of the parachute. Since there's already a connection point there for the lines we figured it would be a better place to stitch something else onto as compared to another point on the bottom edge of the parachute where the fabric is more fragile. The reefing line will be fed through all of these webbing loops and tied into a loop of the appropriate circumference to achieve our desired cross-sectional area.
We will have two line cutters at two points on the reefing line for redundancy and the wires to each cutter will be attached to the reefing line to hopefully prevent them from getting wrapped around as much. If a line cutter demonstration shows that they eject hot gas/flame on activation that would potentially damage the parachute material, we will make small covering bags for each line cutter to prevent the hot gases/flames from touching the parachute material.