Rainmaker Technology’s proposal to deploy cloud seeding flares on small drones is facing opposition from the airline pilots’ union, which has urged the Federal Aviation Administration to consider denying the launch request unless it meets stricter safety guidelines.
The Federal Aviation Administration’s decision will signal how the regulator continues to watch weather modification by unmanned aircraft. Rainmaker’s bet on small drones hangs in the balance.
The Air Line Pilots Association (ALPA) told the FAA that the rainmaker petition “fails to demonstrate an equivalent level of safety” and poses an “extreme safety risk.”
Rainmaker is seeking an exemption from regulations that prevent small drones from carrying hazardous materials. The startup filed in July, and the FAA has yet to rule. Instead, it issued a request for additional information, pressing for specifics about operations and safety.
In its submission, the rainmaker proposed using two types of flares—one “spotlight” and the other on its Elijah quadruple to disperse particles that stimulate precipitation. Elijah’s maximum altitude is 15,000 feet MSL (measured above sea level), which is in controlled airspace where commercial aircraft regularly fly. Drones require air traffic control permission to fly in this bubble.
Rainmaker’s petition states that it will operate in Class G (uncontrolled) airspace unless otherwise authorized. ALPA notes that the filing does not explicitly state where the flights would take place or what altitudes would be used. Rainmaker and ALPA did not respond to TechCrunch’s requests for comment.
The union also opposes the flares themselves, citing concerns about foreign debris and fire safety. ALPA points out that the petition does not include trajectory modeling of the discarded shells or analysis of the environmental impact of the chemicals.
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However, Rainmaker says the flights will take place in rural areas and over properties owned by private homeowners, with whom Rainmaker has developed a close working relationship.
Cloud seeding is already happening today, mostly in the western U.S., with service planes flown by government agencies. Ski resorts are handing over the operations to help keep their runs white, and irrigation and water districts are flying them to build snowpack in the winter to help feed their reservoirs during the spring melt.
The common practice of cloud seeding dates back to the 1950s. By spraying small particles into certain clouds, scientists discovered that they could induce precipitation. Typically, silver iodide is used as the particles in cloud seeding operations, primarily because they mimic the shape of ice crystals.
When a silver iodide particle hits a supercooled water droplet, it causes the droplet to freeze rapidly because its water is already below freezing. Once an ice crystal forms, it can grow rapidly, if conditions are right, faster than a liquid water droplet would under similar conditions. Plus, the rapid growth helps the crystals stick around longer than a water droplet, which would evaporate before it has a chance to fall as precipitation.
Rainmaker’s Twist – doing this work with drones instead of a pilot – could prove safer in the long run. The company says that flight profiles are tightly constrained, monitored by a remote pilot and trained crews in rural areas, with other safety checks.
What happens next depends on whether the FAA thinks these mitigations are enough. However it is decided, the agency’s response will likely set the tone for new cloud seeding approaches.
