You're totally right, I have no idea what I'm talking about!

Some random babble:

I'm glad you're running 6S at least. I was worried you were running something like a 2S rig.

Is your your assertion is no one can build a quadcopter style drone that can go 100mph and carrying a 2lb payload?

Or that you can't add 2lbs to your 6 inch racing style quad and go 100mph without changing something design wise?

Because the first has a number of commercial products (albeit using hybrid powertrains due to longer desired range [https://soninhybrid.com/], [https://dronedj.com/2022/01/04/firefly-really-heavy-lift-dro...]). They'd have no issues doing the same thing over shorter distance, but folks wouldn't buy them - because for the commercial use cases, speed is only useful when it means covering more distance (and is therefore is really speed + distance). Tweaking some variables and changing some thinking would get you something from DJI that would have no issues, but it wouldn't sell, at least to the typical commercial or recreational market.

I would be VERY surprised if DJI didn't already have a healthy set of military contracts for doing exactly this, but if so, it isn't anything public.

The second yeah, should hopefully be obvious. It isn't THAT far off though, as you'll see below.

For the situation I'm mentioning, there are different tradeoffs, and I'm doing the best I can without causing problems re: confidential details:

You're getting confused on amperage, because peak amperage output is a matter of parallelizing batteries and design of the cell, and is NOT battery chemistry limitations (per-se). You can double your peak available amperage by changing the way your battery is wired. It doesn't add weight. It does halve capacity however, but that is range, not peak power.

Thermal management is one of the bigger issues in practice, and higher voltages tend to help a lot there (less resistance in wiring for a given amount of power delivered). It also results in less weight.

If you had a 40 amp peak 6S pack (which is only ~ 800 watts peak), you'd get the same per-pack equivalent draw with 3x in parallel (120amp total is 40 amp per pack) or 2.6kw. But frankly, 12S (or higher voltage) is better in every way but expense/parts availability if you're handy with electronics. A 12S 40A pack delivers 3x the actual power for the same wiring, assuming components are insulated/rated for the voltage.

And yeah, I know 'peak amps' numbers on most batteries are a lie, first thing I do when I do a build is instrument power flow, including amperage under load.

ESCs/motor controllers would likely be your primary sourcing difficulty, but you can get COTS 120 Amp individual motor ESCs [https://www.getfpv.com/electronics/electronic-speed-controll...] inexpensively if you're running 6S, and not too crazy expensive if you're running 12S like that particular one is designed for. That one also already has BLHeli_32, but most of them can be re-flashed, and then every COTS flight controller can deal with them pretty easily. That particular ESC is rated for controlling 32kw PER MOTOR, by the way. You could use a 4 in 1, but as you note, meh on total power rating. They are compact. They also have thermal management issues. Individual ESCs can get out into the airstream easier, and if you fry one it's less work to replace.

Motors with the desired design criteria would be next, sourcing difficulty wise, but that would depend on specific propeller/fan design. There are a LOT of options, and winding your own actually isn't THAT hard (or re-winding a COTS one for different characteristics).

Most likely anyone who is doing what I describe at a state actor level is going to be doing their own ESC design, and ESC + flight control firmware anyway, and the electronics to make a compact ESC for arbitrary amperage/voltages are very well understood. They're used in everything from elevator motors, to milling machines, to handtools. If it's someone doing a military style contract, they'll of course do their own battery packs, nominally to maximize their performance envelope for whatever mission they're trying to get the gov't to cough up cash for, but also because COTS will make them look less awesome.

But it's easy to rewire COTS packs to do pretty much whatever you want tradeoff wise, re: voltage, amperage, etc. Lithium batteries are amazing for their ability to handle very high peak power draw, and in the scenario that I'm describing, the bottleneck would likely be thermals, not chemistry or weight, and considering the time window being discussed, there are lightweight and interesting ways of handling that.

100 mph == 1.6 miles per minute after all, and it's highly unlikely the drone would be anything but hot gas and rapidly disassembled small parts after that amount of time.

You're getting confused on props and tip speed, because you aren't thinking of, or aren't aware of, ducted fans which specifically solve this problem by giving you much higher thrust at the cost of a little (or a lot, depending on the frame design) extra weight. A little less than double, depending on conditions.

Prop pitch and design would look weird, comparatively, depending on the mission, from what you're used to seeing, and depending on the specific numbers, elements like blade count, leading and trailing edge, chord length, etc. tend to differ.

High agility has different airflow and stall characteristics than maximum speed and/or maximum weight and propellers designed for one tend to be not great for the other.

That said, there are a number of aerospace engineers quite familiar with the problem, and it's well solved at this point, up to ~ 160ish mph. And by well solved, I mean Embry-Riddle has it in their basic curricula, and there are a LOT of graduates rattling around. They're pretty smart too, in my experience, and are itching for problems like this to solve. Especially if you are ok with things exploding until they get it right.

After that it requires more complex solutions (usually involving a degree of direct jet propulsion) and some amount of fire.

Alright, I'm done. Anything more and I'm going to get in trouble.