[addaon]

Basically, the safety analysis will have to show that it the risk to people on-board is mitigated. Ways the risk can be realized are basically by reflection -- even secondary and tertiary reflections of infrared lasers can be dangerous, since the beam energy is quite high and the blink reflex isn't triggered. Concerns would be things like glancing reflections off water, reflections off buildings, etc. Posssible mitigations would include having an independent monitoring system disable the laser if it would intersect the ground (likely required to mitigate hazards to people on the ground anyway), IR notch filters on the windscreens to prevent reflections from entering the cockpit (or laser safety glasses required in situations where it may be used), etc. This is generally the aviation mindset -- a rigorous exploration of what can go wrong (and sometimes, the answer is "not much", but even that needs to be considered and quantified) with multiple layers of mitigation to get the risk to acceptable levels.

[dTal]

That's all very well, but surely you'd only turn the enormous laser on if there were a heat-seeking missile bearing down on you, in which case the laser represents the safer option even without any risk mitigations.

[addaon]

You'd only turn it on if your sensing system had a positive detection for a missile... any such system has its own failure modes, and while it's true that a sensing system with few false positives is a mitigation to hazards to the pilots, you have to consider the system as a whole. Especially if heat-seeking missiles fired at cargo planes are rare (and from what I can tell, they are), you expect the majority of activations to be false positives.

[peteradio]

Curious if you could do this quick enough via a simple detector in the cockpit. Is there a time interval that is short enough that the laser has basically no chance of harm?

[addaon]

In terms of time constants: Yes, probably. Visible lasers can be eye-safe at much higher powers because of the blink reflex, and the blink reflex is on the order of a hundred milliseconds -- detecting IR and shutting down even a gas laser should be millisecond-scale at most. One challenge would be very specular reflections that hit an eye but not your sensor, but a wide-area sensor should be able to get reflections even off the pilot's eye itself. The remaining bit would be very high frequency specificity on the sensor to allow high sensitivity without false positives, but that's pretty trivial.

[djsavvy]

Why is the blink reflex not triggered by these reflections?

[ajuc]

Because we don't see in infrared.

[cuteboy19]

> A pop or click noise emanating from the eyeball may be the only indication that retinal damage has occurred i.e. the retina was heated to over 100 °C resulting in localized explosive boiling accompanied by the immediate creation of a permanent blind spot

Terrifying stuff https://en.m.wikipedia.org/wiki/Laser_safety

[mzs]

IR