Yikes. As a spaceflight enthusiast, this actually rattled me enough to do a deep dive on what would happen if a catastrophe like this happens in real life.
I don't think the explosion would be as devastating as you described, given the specific circumstances (engine explosion 18s into the flight). The N1's engine exploded only 0.25s into the flight, causing the rest of the rocket to fall back directly onto the launchpad shortly after; the Starship explosion would have been airborne, and airborne rocket explosions usually involve an initial small blast that blows the fuel and the oxidiser in opposite directions, igniting the former without the latter. The resulting shockwave would be much weaker than if something like an overpressure fault had ruptured the fuel and oxidiser tanks on the ground, allowing them to mix before igniting.
I've found conflicting info on how energetic a Starship explosion would be (assuming 100% combustion):
one source says a fully-fueled Super Heavy booster alone would be equivalent to 9 kt, while
another says that even a fully-fueled Starship stack (carrying 4,600 tons of Methalox fuel, assuming a TNT equivalent of roughly 40%) would only result in a 1.8 kt blast. The second figure seems more realistic; after all, how could 4.6 kilotons of fuel creates an explosion with a yield exceeding its own weight in TNT?
And even then, the comparison to nuclear weapons yield is deceptive at best. Quoting a
third source:
"a nuclear bomb explodes with EXTREMELY high power (energy/time), so high that some of the biggest thermonuclear devices detonated in the 60s had an instantaneous peak power of a couple percent of the power output of the sun. These are tremendously violent explosive detonations; a rocket filled with flammable liquids is NOT that. A rocket exploding is a deflagration. The shockwaves and overpressures are much lower than for nuclear or high-brisance conventional explosives."
Leaving aside the explosion's scale, the possibility of a catastrophic engine failure in the first place should be much lower for Starship than it was for the N1, which has:
1) single-use, expendable engines which were impossible to static fire before launch day, unlike SpaceX's multiple full-duration runs per Raptor/Merlin engine;
2) no launch clamps to fully test the entire rocket, unlike SpaceX's routine full-countdown, engine ignition, and full-duration burn static fires;
3) very primitive computers by modern standards, unable to reliably shut down a failing engine before it could explode; and
4) severe underfunding.
But still - I sincerely hope that a disaster of this magnitude never happens. The catastrophe you described is virtually certain to bankrupt SpaceX and, considering how far behind Blue Origin is, would instantly render commercial space launch a dead letter; if the very concept of reusable super-heavy rockets ends up being discredited as well, human spaceflight as a whole would be set back by
decades.
