Alex Miller

Final Project

Viper: police self-defence PAVA device

In looking to combat the rise in violent attacks on under protected police officers in the UK and Metropolitan area, Viper is a solution to replace existing underperforming irritant spray devices that have limited range and accuracy. It looks to reduce the need for use of force in officer protection during a time of increased awareness of perceived police brutality. Post COVID, the knife crime epidemic has already returned to its previous peaks and is continuing to rise again. For the Police, who suffer constant budget cuts and a stretched workforce, there is a need for better cost-effective equipment to protect themselves. Conducted Energy Devices (CEDs) such as the Taser, in addition to their safety concerns when used, are too expensive for widespread roll out in the force. The standard officer, equipped with a baton and PAVA spray that currently can “only be relied on at distances of 3-4 ft from an attacker”, are completely exposed when facing knives and increasingly heavily equipped criminals.

The product was designed alongside insight, feedback, and advice from a Midlands Special Police Unit officer. Its elements were developed through rigorous performance testing and iterative development in both its functionality and threatening aesthetic. The product needed to also conform to home office PAVA safety requirements for deployment in the UK police to be permitted.

Thinking Sustainably

A threatening aesthetic and additional laser dot targeting gives officers several stages of intervention that vary in levels of use of force. An officer can adapt their methods of de-escalation in real-time when using the product in varying situations of danger. Viper’s effective lower use of force options present a more sustainable PAVA solution. Currently PAVA spray is single use and Forces are told to replace cannisters after each use to not risk another officer finding themselves with an empty cannister when out in the field. Viper reduces how often an officer needs to spray PAVA to protect themselves. It features threatening safe dual laser dot targeting so suspects feel threatened and targeted when confronting a drawn device. By improving the threat that the device poses to criminals through aesthetics and improvements in spray performance, Officers can now control situations from a safer distance away from a suspect while reducing their own use of force for de-escalation. Viper hopes to save in materials and cost of pressurised cannisters by reducing how often they are thrown away.

How It Works

In high intensity situations, officers can often struggle to spray current PAVA devices from their traditional top cap triggers because under stress their fine motor skills are severely reduced. Viper’s larger front trigger provides a more reliable spray activation with additional improved spray performance achieved through its nozzle design. For the improved performance of spray, the device’s superior nozzle design needed a 7cm barrel. To keep the product footprint small while holstered on an officer’s vest, the barrel extends upon activation of a 2-stage trigger. When the trigger is squeezed the first stage activates laser targeting and extends the barrel ready for fire, a noticeable further squeeze would then actuate the nozzle against the stem of the cannister and fire PAVA irritant spray from the device towards its intended target.

Nozzle Design Development

Through iterative testing and evaluation of varying nozzle and spray characteristics I was able to determine a nozzle design that would exceed current PAVA spray performance. Testing against current PAVA performance, I could compare my findings and conclude a superior nozzle design and increased cannister pressure that would allow the device to be used reliably from at least double the distance of its current 3-4ft performing predecessor.

Nozzle Design Pressure Simulations

Once I knew the characteristics the nozzle needed to feature for improved performance, I set to test its pressure performance to ensure reliable flow of the PAVA solution through the length of the barrel. Characteristics evaluated in the combination of physical and digital testing included varying nozzle exit and entry diameter, varying pressure as well as volume or discharge rate flowing through the nozzle when fired.