(Bloomberg) – Hank sat impassively on a Virginia Techathletic 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 andslammed into Hank's head, smacking the crash-test dummy's neckbackward and embedding shards of shattered propeller in his plasticface.

Related: Game of drones: Liability and insurance coverageissues coming

There is little disagreement that the small- and medium-sizeddrones flooding the U.S. market can seriously injure or even killsomeone. Understanding and minimizing the risk will bekey 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 outletssuch as Time Warner Inc.'s CNN to use them for aerial video.

“What we need to understand, really, is at what level doesinjury become death?” said Mark Blanks, director of thegovernment-approved drone test center based at Virginia Tech'sBlacksburg, Virginia campus. “When does the threshold cross anunacceptable level?”

Over people, long distances

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

“So many people are watching these studies,” said Earl Lawrence,director of the Federal AviationAdministration's Office of Unmanned Aircraft SystemsIntegration. “FAA needs it to support our rulemakingactivities, but so does every other civil aviation authority andinterest groups throughout the world. People want someanswers.”

Only by testing can officials determine whether there's athreshold of weight and design properties under which flights wouldbe safe. And it paves the way for the use of commercial dronesweighing up to 55 pounds, which are needed for deliveries and otherbusiness uses, but could pose a hazard if they fly off course ortheir batteries run out mid-flight.

Intense debate

Drone flights over crowds remain controversial and the subjectof intense debate. The Academy ofModel Aeronautics, an umbrella for clubs around the countrywhere people fly remote-control aircraft, has no plans to allowsuch flights, President Richard Hanson said. “We think it's toorisky,” Hanson said.

The Air Line PilotsAssociation, a union representing cockpit crews in NorthAmerica, 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 werecrashes or near misses with planes or helicopters — rose more than50 percent from January through September 2016 compared to the sameperiod a year earlier. There were 1,367 drone-safety reports to theFAA in that nine-month period, according to the agency.

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

Crash tests on dummies

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

SZ DJITechnology Co., the world's largest drone manufacturer, onMonday released a study arguing that craft weighing up to 4.9pounds (2.2 kilograms) — which includes its best-selling Phantommodels — pose minimal risk to people.

Time Warner Inc.'s CNN is conducting its own research on how tosafely operate drones over crowds for news video photography, saidGreg Agvent, senior director of CNN Aerial Imagery and Reporting.

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The network is so far the only company to receive an FAA waiverto fly over the public with a small drone copter that is tetheredto the ground to restrict its movements. It's working to getbroader permission, Agvent said.

One of the key ways to reduce risk is to enclose dronepropellers so they can't cut people, he said. A test at AalborgUniversity in Denmark showed a drone propeller could impale a sideof pork — a stand-in for human flesh — like a dagger.

CNN is looking at a combination of other protections, such asparachutes, and ensuring its drones are more reliable, Agventsaid.

“I want to use these unmanned systems to cover the news, not bethe news,” Agvent said.

FAA-approved drone test sites

The tests at Virginia Tech are a joint effort between theMid-Atlantic Aviation Partnership, an FAA-approved drone test site,and the school's Institute for Critical Technology and AppliedScience, which studies head injuries in car crashes, sports and themilitary. While it was not requested by FAA, researchers said theyplanned to make results available to the agency.

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“Hank,” a dummy dressed in a VT engineering T-shirt, wasequipped with 15 sensors in his head and neck. He was placed in achair on the 50-yard-line of an indoor football practicefacility.

Pilot and test engineer Andrew Kriz then fired up a DJI Phantom3 quad-copter, which is one of the world's most common models andweighs about three pounds. Kriz made a few practice runs, then flewthe white plastic craft into Hank's face.

A new frontier in drone operations

The impact damaged the Phantom's props, cracked the frame andtore off its camera. Graphs displayed on a computer showed spikesin energy as the craft hit Hank, but more analysis and additionaltests will be needed to determine how badly it would hurt ahuman.

Next, Kriz aimed a DJI Inspire, a higher-end device weighingabout eight pounds, at the dummy. On the first attempt, the dronehit the dummy's chest and bounced off. Still flyable, the dronestruck the dummy's face and neck on a second try.

Related: 5 things insurers need to know before usingdrones

Finally, an eight-rotor DJI S1000, a larger craft weighing morethan 20 pounds that professional photographers might want to useover a crowd, was flown at the dummy. Even though the dense centerof the drone missed, arms holding its rotor blades struck thedummy's face, rocking the neck back and forth. Two slivers of blackpropeller blades penetrated the dummy's cheek.

As drones buzzed nearby, Blanks said the purpose of theexperiments is to open a new frontier in drone operations. But italso highlights a truth about existing models: 

“If you're operating a large, multi-rotor aircraft in reallyclose proximity to people and treating it as it's a toy, then Ithink it's asking for some pretty severe outcomes.”