Well, again a big fan of the P-38, but I should mention two issues here. First, there was actually a kind of parallax between the trajectories of the 20mm v the 50 Cals. The 20mm was aimed up compared to the latter and the two didn’t converge except at a specific distance. Luckily, the 50 cals were generally enough on their own to down a target. At just the right range, a target got both at once, which will ruin anyone’s day.
Second was, there were quite a few P-38 pilots lost to the “Mach tuck” phenomenon. At high speed found only in a dive, the center of pressure on the craft slipped backward causing the tail to flutter and rear control surfaces to lock, forcing the plane into an unrecoverable dive. Quite a few pilots were killed by this and really it’s unfair to generalize that it was from inadequate training. It was a design flaw that Kelly Johnson solved with the introduction of dive flaps, which were not as popularly misconstrued as air brakes. They actually deformed the pressure gradient so it didn’t slip backward (while simultaneously slowing the plane). The flaps did not make it into production until the end of the war so there was indeed a pilot-killing design flaw drivers contended with throughout.
So there were these two issues. You can read more about it in Ben Rich’s most excellent book “Skunkworks”. Rich was Johnson’s successor at Boeing.
If there’s a Mach 5+ bird in design, I haven’t heard about it. That would be very surprising to me. NGAD is really intended as a gen 6 fighter. Maybe it uses precooler, rotating detonation, methane, etc. but pushing a fighter to Mach 5 seems odd to me since you can’t maneuver much at that speed. Maybe they’re doing it just to get interdiction ability, etc. Certainly, the whole industry knew about precooler possibilities decades ago.
It is also possible something like NGAD burns hydrogen. Usually jets burn kerosene, same as Soviet rockets and Falcon 9, because volumetrically, it’s the highest energy fuel. Hydrogen is the highest energy fuel by weight, so the US used it in the Apollo program and the Shuttle. However, methane is between these, easy to compress into liquid, easy to handle on the ground. It’s what is in Starship, and New Shepherd. Kelly Johnson looked hard at both methane and hydrogen for the SR-71 Blackbird but put it off to the future because of the technical challenges. Any gen 6 craft might use either methane or hydrogen. Especially now that we’ve learned hydrogen’s volumetric issues can be solved by diffusing it into metal and coaxing the molecules far closer than even a liquid, hydrogen fueled planes could become a thing with an appropriately light metal.
Paul Czysz wrote some great stuff about precoolers early this century. He has a great book if you want to search. I have a copy somewhere. I actually met him at a conference about 2008. Amazing guy. But this whole notion of compressing air until it liquifies, and separating out the O2 or not, that goes back to the 50’s I think. It’s long been held as radical tech just out of the reach of funding.
NGAD has funding for whatever they want, so yeah. Totally believable.
Btw, as to the superturbochargers on the P-38, I was once told that particular piece of kit was so highly valued it was the only technology the US did not share with the UK during the war. Dunno if that’s true. I also heard that the trumpet shaped cover on the top of the cowling was there as a distraction and had nothing to do with the supercharger or its location. Pretty sure that’s true.