Nuclear physics is by now well understood, and it offers no super-weapon beyond the ordinary scaling of a thermonuclear bomb—and certainly nothing that would run away to Earth- or star-busting scales.
Not earth-busting, but the ordinary scaling of a thermonuclear bomb can go pretty far! I think Project Sundial deserves an honorable mention.
Tsar bomba as reference for comparison: It’s the most powerful weapon tested so far and “yielded the equivalent of 50 megatons of TNT”, while Project Sundial “intended to have a yield of 10 gigatons of TNT”, i.e. a factor 200 between them.
The blast wave circled the globe three times [...]
A seismic wave in the Earth’s crust, generated by the shock wave of the explosion, also circled the globe three times.
The atmospheric pressure wave resulting from the explosion was recorded three times in New Zealand [...]
Glass shattered in windows 780 km (480 mi) from the explosion
Is there an upper limit to the possible yield of thermonuclear weapons? Could the pressure wave become strong enough to break windows and more around the globe?
There’s no hard limit to increasing thermonuclear weapon yield by increasing the number of stages, but you’d have to proportionally increase the bomb size. The Taylor limit of ~6 kt/kg means that a 10 Gt bomb would need to weigh at least ~2000 t. Could easily fit on a cargo ship but an OOM larger than the largest airplane.
Naively the damage radius scales with as yield^(1/3), so you’d need a ~17 Tt bomb to shatter windows on the other side of the planet. For comparison, the Chicxulub impactor that probably killed the dinosaurs released about 100 Tt; smashed windows at the antipode are probably the least of your concerns at that point.
Shouldn’t the scaling be yield^{1/2} if you’re considering energy radial flux? But also, on these scales we should consider whether the atmosphere “channels” the energy as it bounces between the ground and the upper terminal points thus achieving something more like a ~yield scaling?
Thermal radiation goes as yield^{1/2} for the reason you’ve suggested but pressure goes as yield^{1/3} because the region of overpressure expands and therefore maximum pressure is 1/volume. I’m not sure how this interacts with the curvature of the Earth but would generically expect this to make things more benign at the antipode, not less.
I thought we were talking about a shockwave, so ultimately a pressure front? That’s the part that travels several times around the world. I mean obviously with plenty of volumetric loss/dispersion on the road.
Not earth-busting, but the ordinary scaling of a thermonuclear bomb can go pretty far! I think Project Sundial deserves an honorable mention.
Tsar bomba as reference for comparison: It’s the most powerful weapon tested so far and “yielded the equivalent of 50 megatons of TNT”, while Project Sundial “intended to have a yield of 10 gigatons of TNT”, i.e. a factor 200 between them.
Is there an upper limit to the possible yield of thermonuclear weapons? Could the pressure wave become strong enough to break windows and more around the globe?
There’s no hard limit to increasing thermonuclear weapon yield by increasing the number of stages, but you’d have to proportionally increase the bomb size. The Taylor limit of ~6 kt/kg means that a 10 Gt bomb would need to weigh at least ~2000 t. Could easily fit on a cargo ship but an OOM larger than the largest airplane.
Naively the damage radius scales with as yield^(1/3), so you’d need a ~17 Tt bomb to shatter windows on the other side of the planet. For comparison, the Chicxulub impactor that probably killed the dinosaurs released about 100 Tt; smashed windows at the antipode are probably the least of your concerns at that point.
Shouldn’t the scaling be yield^{1/2} if you’re considering energy radial flux? But also, on these scales we should consider whether the atmosphere “channels” the energy as it bounces between the ground and the upper terminal points thus achieving something more like a ~yield scaling?
Thermal radiation goes as yield^{1/2} for the reason you’ve suggested but pressure goes as yield^{1/3} because the region of overpressure expands and therefore maximum pressure is 1/volume. I’m not sure how this interacts with the curvature of the Earth but would generically expect this to make things more benign at the antipode, not less.
I thought we were talking about a shockwave, so ultimately a pressure front? That’s the part that travels several times around the world. I mean obviously with plenty of volumetric loss/dispersion on the road.