[nthompson]

Pulsed femtosecond lasers have repeat rates in the megahertz. The total energy is very high. When I took laser physics in grad school, they were able to drop a razor blade through the beam and slice it in half. That was in 2013.

So yeah, pulsed lasers can do it, and I'm certain the Air Force would rather be using them. They are finnicky though.

[chongli]

Pulsed femtosecond lasers have repeat rates in the megahertz.

Not for petawatt lasers, those are around 1Hz or lower [1].

[1] http://www.eli-np.ro/research-activities-ra1.php

[Retric]

Both systems are cutting edge and a the limit of what we can build. They are not using a continuous beam because it’s inherently better, they are using it because it’s the best compromise.

[jbay808]

Was the time-averaged power higher than 50kW? I think that's what we're talking about here. Peak power is a measurement of something else entirely, and I wouldn't be surprised if this military laser were also pulsed. But it's quite uncommon to find a laser with 50 kW of time-averaged power output, let alone on an airplane, which is what makes this impressive.

[grkvlt]

Yeah, a Petawatt is huge, there is nothing on earth (well, see next sentence) that can provide that sort of average power continuously. For comparison, 4PJ is basically the output of a kiloton nuclear weapon, so one second of a PW laser needs a nuclear weapon powering the thing.

[Retric]

Averaging 50kw is impressive. However, unless you can keep targeting the same area for X unit of time the average power output over X period is not important.

That said, I would be shocked if they can dissipate enough heat to fire a continuous beam for an hour. It’s very likely designed to be pulsed over longer time periods.

[electrograv]

> So yeah, pulsed lasers can do it, and I'm certain the Air Force would rather be using them.

Do you really think they are so incompetent so as not to have thought of this?

I’m sure the labs developing these are aware of what you’re suggesting, have probably even tried them, and have their reasons for the design they’ve chosen.

[Retric]

Want to and can are different things.

They likely want to used pulsed lasers assuming average power output stayed the same, but physics is a bitch. So, they don’t get to arbitrarily chose.

[EpicEng]

Ok, but if we're including things which are currently impossible then I'd assume they'd rather just use Professor X and have him mind blast the missiles out of the atmosphere.

[Retric]

Every new design is building something that does not exist.

We already have pulsed lasers with average power output in the kw range over several hours. Even better, this thing does not need to fire for hours at a time so you can skimp on heat dissipation. But, you can buy 2kw laser cutters off the shelf.

Really, scaling it up in a lab is one thing, but getting everything else to work like dealing with vibration, portability, and targeting is hard. So, while this design had slightly better tradeoffs, that does not say much about the design space they where working with or what they consider useful vs required. Ex: What frequency is this?