Hank sat impassively on a Virginia Tech athletic field, ready to take it on the chin for the future of drone commerce.

About 30 yards away, an eight-rotor unmanned copter hovered, buzzing like a swarm of bees. The 21-pound drone tilted forward, accelerated sharply and slammed into Hank’s head, smacking the crash-test dummy’s neck backward and embedding shards of shattered propeller in his plastic face.

There is little disagreement that the small- and medium-sized drones flooding the U.S. market can seriously injure or even kill someone. Understanding and minimizing the risk will be key to convincing regulators to expand their permitted uses, clearing the way for plans by Amazon.com Inc. and Alphabet Inc. to have them deliver packages or news outlets such as Time Warner Inc.’s CNN to use them for aerial video.

“What we need to understand, really, is at what level does injury become death?” said Mark Blanks, director of the government-approved drone test center based at Virginia Tech’s Blacksburg, Virginia campus. “When does the threshold cross an unacceptable level?”

While the FAA liberalized restrictions on drones flown for hire last summer, in most cases they still can’t be flown directly over people or for long distances. The agency had planned by the end of 2016 to unveil a proposal to allow drone flights closer to people but that has been delayed over security concerns.

“So many people are watching these studies,” said Earl Lawrence, director of the Federal Aviation Administration’s Office of Unmanned Aircraft Systems Integration. “FAA needs it to support our rulemaking activities, but so does every other civil aviation authority and interest groups throughout the world. People want some answers.”

Only by testing can officials determine whether there’s a threshold of weight and design properties under which flights would be safe. And it paves the way for the use of commercial drones weighing up to 55 pounds, which are needed for deliveries and other business uses, but could pose a hazard if they fly off course or their batteries run out mid-flight.

Drone flights over crowds remain controversial and the subject of intense debate. The Academy of Model Aeronautics, an umbrella for clubs around the country where people fly remote-control aircraft, has no plans to allow such flights, President Richard Hanson said. “We think it’s too risky,” Hanson said.

The Air Line Pilots Association, a union representing cockpit crews in North America, is urging the FAA to take a “slow and methodical” approach, said the group’s safety chief Captain Steve Jangelis.

Reports of errant drone flights — a handful of which were crashes or near misses with planes or helicopters — rose more than 50% from January through September 2016 compared to the same period a year earlier. There were 1,367 drone-safety reports to the FAA in that nine-month period, according to the agency.

While the research is still under FAA review, there are early indications of at least one piece of good news for the industry: When small consumer drones made of plastic strike an object like a human head, they tend to break apart, lessening the impact, according to David Arterburn, a researcher at the University of Alabama in Huntsville.

Arterburn heads the FAA’s research effort to determine how badly a drone would hurt a person, and whether it’s possible to create a class of vehicle that’s so light and soft they aren’t a hazard. The group conducted its crash tests on dummies last summer at Wichita State University in Kansas.