Parachute
Contents
- What is a Parachute?
- How to Design a Parachute?
- Parachutes Types
- How to Manufacture a Parachute?
- How to Fold a Parachute?
- References & Further Reading
What is a Parachute?
A parachute is an aerodynamic device used to slow down the descent of an object to the ground at a specific speed. It can come in various geometries and sizes to accommodate different landing speeds. In model rockets, parachutes are essential components for the safe landing of the rocket and any payload it may carry.
How to Design a Parachute?
Before designing a parachute, it is necessary to determine the impact velocity of the object it will carry – whether it’s a rocket or a payload. Then, the most suitable geometry should be selected. When choosing the geometry, the space that the folded parachute will occupy inside the rocket needs to be calculated to achieve the desired landing speed. Different geometries may be preferred to achieve the same landing speed in smaller sizes. To calculate landing speed with different geometries, you can use Rocket Fx’s “Parachute Size” calculation page and the “Speed During Recovery” calculation page for ready-made parachutes, accessible via the Rocket Fx application on both mobile and desktop platforms.
Other considerations when designing a parachute include the choice of material and the ropes used in the parachute. Additionally, the space occupied by the parachute inside the rocket and the weight it adds will be determined. Commonly, non-porous fabrics such as ripstop nylon are used as parachute materials. These fabrics are known for their durability and resistance to air permeation. The ropes used to attach the parachute to the object should be shock-resistant and non-stretching, as they will be exposed to shock during deployment. On average, parachutes use 4, 6, or 8 pieces of rope. The number varies depending on the type of parachute fabric, sewing method, geometry, and size. The most suitable rope attachment method is to attach ropes to every seam of the parachute, ensuring even weight distribution and stronger seams during shocks.
Drag Coefficient: 0.75-0.80
Drag Coefficient: 0.85-0.95
Drag Coefficient: 0.62-0.77
Drag Coefficient: 0.75-0.90
Drag Coefficient: 0.75-0.92
Drag Coefficient: 0.80-0.96
Drag Coefficient: 0.28-0.42
Drag Coefficient: 0.30-0.32
Drag Coefficient: 0.60-0.85
Drag Coefficient: 0.78-0.87
Drag Coefficient: 0.75-0.87
How to Manufacture a Parachute?
Before starting parachute manufacturing, the correct fabric must be obtained. The required fabric area can be calculated using Rocket Fx’s “Parachute Size” calculation page. After obtaining the fabric, different manufacturing methods can be applied for different geometries. If a circular parachute is to be manufactured, the circle can be divided into 6 or 8 triangular parts, which are then cut from the fabric and sewn together using a sewing machine. If the parachute is intended to be long, it can be constructed using isosceles triangles. For a wider parachute, equilateral triangles can be employed. By utilizing different triangular geometries, parachutes with various characteristics can be produced. Instead of joining the vertices of the triangles at the apex of the parachute, cutting off the tips of the triangles and inserting a circle within the resulting gap can prevent the disadvantage of reduced durability due to multiple stitches at a single point. This approach will result in a more robust parachute. While hand-sewing is possible, it is not recommended for high-altitude or heavy objects as the stitching points may open during shock. If a zigzag stitch is desired, the fabric can be folded and sewn on top of each other to the width of the fabric stitching. To give the parachute a skirt profile, an additional fabric piece can be sewn to the end of the circular shape. For an X-shaped parachute, two rectangular pieces can be cut and sewn on top of each other, or the “X” shape can be drawn and cut on the fabric. When cutting fabric for the parachute, it is important not to forget to leave seam allowances. Holes can be made on the parachute to attach ropes, where ropes can be tied. Another method is to sew an additional fabric piece in a “V” shape at the point where the ropes will be attached, and ropes can be tied to these pieces.
How to Fold a Parachute?
For circular parachutes: first, fold the parachute in half to form a semicircle. Fold it again from the side ends. Pass the parachute ropes through the center and fold it again from the side ends. Then, roll it from the pointed end like making a roll, and wrap the remaining ropes around it.
References & Further Reading
- Juan R. Cruz, Exploration Systems Engineering Branch NASA Langley Research Center, Parachutes for Planetary Entry Systems.
- DUTlab, DUTlab VENÜS Project, 2021