payload parachute design delivery testing

Parachute Design and Deployment: A Technical Study and Experimental Framework

1. Theoretical Foundation: Understanding Parachute Dynamics

Parachutes function as aerodynamic decelerators, converting gravitational potential energy into drag force to reduce terminal velocity during descent. Their application spans aerospace recovery systems, payload delivery, and recreational skydiving. The core principle behind parachute operation lies in the balance between gravitational force and drag force. Parachute systems are optimized to maximize drag to achieve stable and slow descent. The configuration of the canopy, the materials used, and the method of suspension play critical roles in aerodynamic performance.

2. Structural Components of a Parachute System

A parachute system typically comprises the following major elements:

2.1 Canopy

The canopy is the primary surface that interacts with airflow to produce drag. It can take various geometric forms Circular (flat or conical), Cylindrical, Elliptical, Annular (with central hole). The choice of canopy shape directly affects drag coefficient, stability, and deployment dynamics.

2.2 Gores

Gores are the individual fabric segments that are joined to form the complete canopy. Each gore corresponds to a suspension line and is essential for uniform load distribution. The number of gores influences the symmetry and strength of the parachute.

2.3 Suspension Lines

Suspension lines connect the canopy to the payload (or riser), distributing the load evenly across the canopy’s surface. Their length and attachment symmetry are critical for ensuring a stable descent.

2.4 Spill Holes

Spill holes are apertures in the center of the canopy that allow controlled airflow through the structure. Their function is to reduce oscillations and stabilize the descent path. In this study, spill holes were not used to isolate the impact of canopy geometry.

2.5 Payload Interface

The payload connection (hook, harness, or riser) must be secure and centered to prevent tilting or tangling during deployment.

3. Canopy Design Parameters and Variants

This investigation studied two primary parachute configurations:

3.1 Cylindrical Canopy (No Spill Hole)

Specifications:

  • Diameter: 38.2 cm
  • Height (Length): 59 cm
  • Material: Medium-sized polythene garbage bag
  • Gores: 4
  • Suspension Lines: 4
  • String Length: Equal to cylinder height
  • Canopy Surface Area Approximation: A≈πdhA \approx \pi d h

This shape is unconventional in aeronautics but suitable for simplified material handling in small-scale tests.

3.2 Circular Canopy (No Spill Hole)

Specifications:

  • Radius: 50 cm
  • Canopy Angle (Φ): 300°, 360°, 420°
  • Material: Polythene sheet (flattened garbage bag)
  • Gores: 8
  • Suspension Lines: 8
  • String Length: 1.5 × Radius = 75 cm
  • Surface Area: A=πR2A=\pi R^2, adjusted based on effective arc angle

Three variants were evaluated: 300°, 360°, 420°

4. Experimental Observations and Comparative Analysis

4.1 Testing Methodology

  • Drop Height: ~60 ft (5 building floors)
  • Test Environment: Still-air outdoor conditions
  • Payloads: 100g, 150g, 250g bottles
    Deployment: Manual release from rooftop

4.2 Testing Inferences

  • IEffective for low to moderate weights. Drag coefficient was lower than circular designs.
  • Higher canopy angles improved load distribution but introduced lateral drift. Circular designs generally outperformed cylindrical models in descent rate control and stability.

4.3 Insights

  • String Symmetry is critical, imbalanced lines result in uneven loading and canopy tilt.
  • Warping in canopy angle = 420° created lateral instability despite good drag.
  • Material Elasticity (polythene) limits performance, stretch under load affects shape retention.
  • Spill Hole Absence made some canopies oscillate slightly but helped maximize drag

5. Procedural Method for Experimental Fabrication

Although not the core focus of this document, the following fabrication procedures were applied during testing:

5.1 Cylindrical Parachute Construction

  1. Select a cylindrical polythene bag with desired dimensions.
  2. Identify four equidistant points along the vertical edge of the surface.
  3. Attach four equal-length strings using tape; tie ends symmetrically. Secure the other end of the strings to the payload.
  4. Conduct manual test drop from a controlled height.

5.2 Circular Parachute Construction

  1. Cut a circular sheet of radius 50 cm from plastic material.

  2. Modify canopy geometry based on desired Φ:

    • For Φ < 360°: Remove segment and seal edges to form cone.
    • For Φ > 360°: Add segment and seal to form a warped disk.

  3. Attach eight suspension lines, evenly spaced around the canopy

  4. Tie lines to the payload, ensuring symmetric length and tension.

  5. Deploy parachute via manual release.

6. Conclusion and Future Work

This study establishes a baseline for understanding how parachute shape, canopy angle, and string configuration influence descent behavior. Key findings include:

  • Circular canopies are superior to cylindrical models in drag production
  • Higher canopy angles increase drift;
  • Lightweight polythene is viable for small payloads but lacks the performance of professional fabrics.

Future Considerations:

  • Evaluate effect of spill holes on stability and terminal velocity.
  • Introduce controlled deployment systems (e.g., spring-loaded boxes).
  • Use precision timers or high-speed cameras for quantitative velocity tracking.
  • Extend analysis to material deformation and multi-canopy configurations.
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