Evolution of Parachute Materials

The materials used in parachutes, both the canopies and ropes have evolved quite a bit over recent years. This blog post gives an overview of the various requirements and materials used for canopies, roped and the parachute bag. 

Canopy materials

The key design factors for a parachute canopy material are:

• Strength to Weight ratio: It determines the minimum weight of the parachute.
• Durability/Tear resistance: Weaving and stitching techniques have a strong impact on durability, but it is still strongly dependent on the base material.
• Elastic Energy Stored and Elongation: Higher stored energy leads to better performance under shock loads. On the other hand, a very higher elongation can lead to parachute deformation which can result in unexpected aerodynamic properties.
• Ease of Manufacturing and Cost: It is more important for some missions than others.

While Silk has been known for its exceptional strength and modulus for centuries, it was largely used in parachutes and hot air balloons from 1900-1945. Emergency parachutes weren’t a norm for majority of WW1 but were part of necessary equipment in WW2. Rayon’s use in parachutes was relatively short-lived because of the brittleness of fibre and was only being used for Cargo Parachutes.

While Silk has been known for its exceptional strength and modulus for centuries, it was largely used in parachutes and hot air balloons from 1900-1945. Emergency parachutes weren’t a norm for majority of WW1 but were part of the necessary equipment in WW2. Rayon’s use in parachutes was relatively short-lived because of the brittleness of fibre and was only being used for Cargo Parachutes.

The invention of Nylon by DuPont and the timing of WW2 shifted the market. United States Military switched from Japanese Silk parachutes to Nylon Parachutes because of their superior shock energy absorption properties in November 1941. The adoption of Nylon in parachutes practically engulfed the entire supply of Nylon from 1942-1945. Nylon has been the primary material of choice for parachute canopies, lines, and ribbons ever since.

NASA Supersonic High Altitude Parachute Experiment (SHAPE) program in 1971 used Dacron canopies because of their higher thermal stability. A key requirement of the parachute material was to be stable at 135°C for 100 hours. Dacron canopies are comparable to Nylon in energy absorption but have lower strength. It was also in this program that aramids were used in the crown region of the canopies for even greater thermal stability at high temperatures. The use of Dacron and Aramids in canopies has been largely limited to supersonic parachutes.

Rope Materials

The key design factors for the parachute rope materials are:

• Strength to Weight Ratio: it determines the weight of the cables.
• Bulk Factor: It has a large influence on the packing volume of the cables.
• Elastic Energy Stored and Elongation: To handle shock loads. A large elongation can dissipate the impulse energy of the shock load and reduce the maximum load on the payload.
• Abrasion resistance: The ropes are tightly packed in the parachute bag and fast deployment of parachutes can lead to abrasion.
• Max Operating Temperature: This mostly plays a role in supersonic parachutes. The area of transition from the riser to the suspension lines sees the highest temperatures.

Nylon is one of the oldest materials used in parachute ropes ever since its invention. It has a good balance of all design properties at a low cost. Dacron lines are seldom used in skydiving parachutes because of their high elongation and low cost. They have a high bulk factor which makes them unattractive for high-performance applications.

UHMWPE and Vectran are relatively new materials only manufactured by a few companies. They have excellent specific tensile strength and low bulk factor. They do have a low elongation which can lead to higher shock loads on the payloads. These can however be mitigated using reefing techniques. UHMWPE has poor thermal stability which can lead to shrinkage in the application of heat. Vectran has high thermal stability but relatively low wear resistance.

For supersonic parachutes, Aramids are the material of choice because of their higher specific strength and thermal stability. Zylon has similar if not superior properties to Aramids and has been used in ropes in mars missions. They are significantly more expensive which limits their use. While Aramids have low UV resistance, Zylon has even lower UV resistance and needs to be coated or stored away from direct sunlight.

Parachute bag materials

The key design factors for parachute bags are:

• Friction: A low friction coefficient leads to lower heat during deployment.
• Abrasion resistance: It is crucial for multi-use bags.
• Thermal Stability/Fire retardance: Only necessary when pyrotechnic charges are directly used to deploy the parachute.

While Cotton and Nylon are the most common parachute bag materials. Teflon coatings are applied sometimes to further reduce friction. Aramids such as Nomex are used when fire retardance is needed.