The tether looks at least 10m long. Doubt a helmet will prevent zero injuries when a 30kg mass hits you at 10m/s.
I couldn't find any info on the duration of the flight, was it up there in the same league as being fired from a cannon?
BTW, it's been done before many times by many others in many different ways and all had the same common problem - the battery duration in flight mode is just not practical.