Rainmaker Technology’s proposal to deploy cloud-seeding flares on small drones is facing resistance from the airline pilots union. The union has urged the Federal Aviation Administration to consider denying the startup’s request unless it meets stricter safety guidelines. The FAA’s upcoming decision will signal how the regulator views weather-modification by unmanned aerial systems in the future, placing Rainmaker’s bet on small drones in the balance.
The Air Line Pilots Association told the FAA that Rainmaker’s petition fails to demonstrate an equivalent level of safety and poses an extreme safety risk. Rainmaker is seeking an exemption from rules that prohibit small drones from carrying hazardous materials. The startup filed its petition in July, and the FAA has not yet issued a ruling. Instead, the agency issued a follow-up request for information, pressing for specific details on operations and safety.
In its filing, Rainmaker proposed using two types of flares, one burn-in-place and the other ejectable, on its Elijah quadcopter. These flares disperse particles that stimulate precipitation. The Elijah drone has a maximum altitude of 15,000 feet, which is inside controlled airspace where commercial airliners routinely fly. Drones require permission from Air Traffic Control to operate in this airspace. Rainmaker’s petition states it will operate in Class G uncontrolled airspace unless otherwise authorized. However, the pilots union notes the filing does not clearly state where flights would occur or what specific altitudes would be used.
The union also objects to the flares themselves, citing concerns about foreign object debris and fire safety. ALPA points out that the petition does not include trajectory modeling for the ejectable casings or an analysis of the environmental impacts of the chemical agents.
However, Rainmaker says its flights will occur over rural areas and over properties owned by private landlords with whom the company has developed close working relationships.
Cloud-seeding is already a common practice, largely in the Western U.S., using crewed airplanes flown in coordination with state agencies. Ski resorts commission these operations to help keep their runs white, and irrigation and water districts use them to build snowpack in the winter to feed reservoirs during the spring melt.
The general practice of cloud seeding dates back to the 1950s. Scientists found that by spraying small particles into certain clouds, they could induce precipitation. Typically, cloud seeding operations use silver iodide because the particles mimic the shape of ice crystals. When a silver iodide particle bumps into super-cooled water droplets, it causes the droplet to rapidly freeze. Once the ice crystal forms, it can grow quickly if conditions are right, faster than a liquid water droplet would in similar circumstances. This rapid growth helps the crystals last longer than a water droplet, which might evaporate before it has a chance to fall as precipitation.
Rainmaker’s innovation is to conduct this work with drones instead of piloted aircraft, which it argues could prove safer in the long term. The company states that the flight profiles are tightly bounded, overseen by a remote pilot and trained crews, over rural areas, with other safety checks in place. What happens next hinges on whether the FAA finds those mitigations to be sufficient. However the case is decided, the agency’s response will likely set the tone for novel cloud-seeding approaches going forward.