No Pump? No Problem: The Wilson Airless Basketball
No pump? No problem. Wilson’s Airless Gen1 Basketball ditches traditional basketball design for an airless lattice that somehow still bounces. No punctures, no pressure loss, just a $2,500 price tag and a weirdly quiet bounce. Will it replace traditional basketballs? Read more to find out.
Basketball is a sport that has been widely played and enjoyed since 1891. It was invented by James Naismith, a Springfield College instructor and graduate student. At first, the game was played with a leather football. However, as this ball was not specifically designed to bounce well, a new leather ball held together with lace was designed. The new ball was very light and had a very high air pressure, which improved the handling and allowed for a higher bounce. The high air pressure inside this ball became the standard that traditional basketballs still rely on to this day. However, in February 2023, the well-renowned sporting brand Wilson released a prototype for a new concept of the basketball, the Airless Basketball.
What is an Airless Basketball?
Wilson’s Airless Basketball is characterised by its repeating geometric lattice structure which can deform elastically when subjected to a force. This deformation is governed by Hooke’s law which is essential for the ball to return to its original shape after deformation. This is because Hooke’s law states that the force exerted on the structure is proportional to the extension (deformation) shown by the equation: 𝐹 = 𝑘𝑥, where 𝐹 is the force, 𝑘 is the stiffness of the material, and 𝑥 is the extension. As the lattice is a repeating pattern, the force exerted on the ball is distributed evenly across the network of the lattice. The energy of the force is redirected through the bending and compression in the struts of the lattice to ensure there are no points on the ball which are under more stress than others.
A traditional basketball consists of an inner rubber bladder that holds all of the air, and an outer layer which provides grip to the ball. The high air pressure inside the ball allows it to bounce since it will push back against the area of compression and spring the ball back off the floor. However, the pressurised interior of the ball can create problems as it is not only difficult to get the air pressure exactly right, but the pressure also decreases over time. On the contrary, the Airless Gen1 Basketball does not suffer from these issues due to its lack of an inner rubber bladder, meaning that the ball itself does not require extra internal air pressure to bounce. This makes it much more versatile and removes any possibility of the ball puncturing.
Material Properties and Elasticity
Wilson optimised the stiffness and elasticity of the ball's material to achieve a COR of approximately 0.85-0.9, which is similar to that of a traditional air-filled basketball. The lattice on the ball is composed of an inner and outer layer. This helps to increase the COR by making the layers rebound against each other.
The lattice is highly energy-efficient because there is no internal friction within the ball, preventing energy loss as heat. The force is also evenly distributed across the structure, so each strut absorbs only a small amount of energy, minimising heat dissipation. Additionally, the lattice produces much less noise when it bounces, which reduces energy lost as sound waves. Its spherical shape ensures there are no weak spots that could compromise its durability. This gives the airless basketball an advantage over regular basketballs, which often have indentations or features such as air intake holes that concentrate force in specific areas, leading to damage and a shorter lifespan.
The material of the ball is also critical in explaining how the ball functions. It is essential to find a material with exactly the right properties to allow the ball to perform optimally and to extend its lifespan. Whilst no specific details have been released, the ball is most likely made from a type of elastomer (elastic polymer) which is a polymer that exhibits flexible properties. A key material property that must be considered is the Young’s Modulus (𝐸). This is calculated with the stress-strain relationship on the material (\(𝐸=\frac\sigma\epsilon\)). The ball needs to have an optimum Young’s Modulus to exhibit linear elasticity for as much deformation as possible in order for it to not only return to its original shape after compression, but also to provide the bounce. The material chosen had quite a low Young’s modulus, meaning that for a low amount of stress it undergoes a high amount of strain. This is useful because it allows the ball to deform when under load, resulting in a bounce. However, the Young’s modulus could not be too low as the ball would otherwise be too flexible and simply collapse. Therefore, it was necessary to create a material that had just the right balance of flexibility and stiffness.
Manufacturing using 3D Printing
The last major aspect of the ball is its fabrication. It would be impossible to produce this ball using traditional fabrication techniques. However, it is possible to 3D print a structure like this due to the layer-by-layer approach to manufacturing used by 3D printers. 3D printing allows the use of advanced polymers that are tailored for the specific properties of the ball. The process used to manufacture the basketball is Selective Laser Sintering (SLS), which involves using a laser to fuse a powdered polymer layer by layer. This allows for incredibly intricate designs with very precise tolerances. However, drawbacks to this method of manufacture include the high cost, as well as decreased durability from the layers on the ball. However, Wilson picked 3D printing as it was the only possible option for creating the ball due to its highly complex design.
Unique Characteristics
With such an unusual basketball, there are bound to be some unique characteristics. Firstly, and possibly one of the most notable aspects of the ball, is its sound. Its bounce is much quieter than a traditional ball due to the energy conservation of the lattice and the lack of echo in an inner bladder. There are mixed opinions on this as some think that this will allow people who live in more compact areas to play without disturbing others, and some think that the noise is disturbingly quiet, although this idea may gradually fade as people grow more accustomed to airless basketballs.
Another interesting aspect of the ball is its texture. It is said that this basketball has less grip than a traditional ball due to the polymer material used. This means that the ball is more slippery in a player’s hand and on the floor, resulting in an element of unpredictability when compared to a traditional ball.
The aerodynamics of this ball are also different to a traditional basketball. When both balls were thrown for a three pointer with a similar force, the airless basketball travelled less far and seemed to be heavier than the traditional ball, even though they are of approximately the same size and mass. This may potentially be due to the disturbance of air as it passes through the holes in the lattice structure of the ball, creating more drag on the ball and therefore decreasing its velocity.
Finally, there’s the ball’s price. To purchase a Wilson Airless Gen1 basketball, it will costs a staggering $2,500. Most people will not be willing to pay such a large amount of money for a basketball, so it is unlikely that these balls will become commonplace anytime soon.
Whilst there are definitely flaws in the ball’s design, Wilson has almost certainly named the ball a "Gen1" for a reason, implying that there are more generations to come which may better mimic a traditional ball. One day, we may even see these airless basketballs being used for the NBA.
