Starting a paramotor without it being on your back is the most
dangerous time. The yet-to-be-implemented SafeStart seems like the best
approach to passively (no pilot action is required) prevent a prop-strike
injury. But here are are some other good ideas for improving a pilot's
odds during start.
Netting triggered Shutoff
Robin Rumbolt has suggested a system requiring no electronics (besides
a switch) and off-the-shelf products. This will only reduce the injury,
not prevent it since it's still possible for the prop's momentum to carry
it into your fragile flanges.
Thread a small diameter steel cable around the cage, though the
netting, in about the middle. Anchor one end. Connect the other end to a
spring loaded, normally open switch that is connected across the kill
switch. Use a small turnbuckle to adjust the tension.
If the cage is pulled backwards due to line contact, no problem. The
line gets a little slacker.
If a body part goes into the netting it will pull on the threaded line
and cause the switch to close, killing the engine.
To disassemble the cage, just undo the anchored end and remove the
cable. It will only take a minute or two to rethread it upon reassembly.
Emergency Shut Off
Bob Armand has suggested a large red back-up button for killing the
motor. It would only be easily accessible while starting the motor from in
front of it.
Jeff's passive version of this is to use the type of shutoff used on
treadmills. The shutoff lanyard is located near where the manufacturer
wants the pilot to start the motor from. The pilot puts the lanyard around
his hand and starts the motor. If the hand holding the cage moves from its
grip, it pulls the lanyard which shuts off the motor.