A Gigajoule of Damage

[Blood Legend]

What modern weapons do we have that impart close to a Gigajoule of damage?
A megajoule?
Kilojoule?

[Farmer]

Originally Posted by Blood Legend

What modern weapons do we have that impart close to a Gigajoule of damage?
A megajoule?
Kilojoule?

This is a handy list:

https://en.wikipedia.org/wiki/Orders...nitude_(energy)

In the Gigajoule range, they mention things like a lightning bolt, and 1 ton of TNT.

[Anthony]

Originally Posted by Blood Legend

What modern weapons do we have that impart close to a Gigajoule of damage?
A megajoule?
Kilojoule?

A gigajoule is about a quarter ton of TNT, which is a plausible range of filler for a 2,000 lb bomb (most bombs are only a fairly small percentage explosive by weight). There aren't any direct fire weapons that powerful, a 16" battleship cannon is about 350MJ.

A megajoule is in the range of conventional infantry missiles.

A kilojoule is at the high end of pistol ammunition (9mm is about 500J), low end of rifle (.223 is about 1600).

[RyanW]

For purely kinetic energy:

Rifle bullets are in the range of a kilojoule.
An automobile at highway speeds is in the range of a megajoule.
A commuter jet at cruising speed is in the range of a gigajoule.

[edk926]

What was the rating of the nukes dropped on Japan in ww2? How powerful would the modern nuke be?

[whswhs]

Originally Posted by edk926

What was the rating of the nukes dropped on Japan in ww2? How powerful would the modern nuke be?

A gram of TNT released about a kilocalorie, which is 4187 J. So a kilogram is 4.2 MJ, a metric ton is 4.2 GJ, a kiloton is 4.2 TJ, and a megaton is 4.2 PJ. If you know a yield in kT or MT, you can multiply by the relevant constant to get the energy output.

Radius of destruction in meters is approximately the cube root of yield in kilocalories. So 1 m for a gram, 10 m for a kg, 100 m for a tonne, 1 km for a kT, and 10 km for an MT, at least to rough order of magnitude.

[johndallman]

Originally Posted by edk926

What was the rating of the nukes dropped on Japan in ww2?

15-20 kilotons. That seems to be the natural yield of the types that were easiest to build with 1940s technology.

Originally Posted by edk926

How powerful would the modern nuke be?

What size would sir like?

As an example, the Trident II submarine-launched ballistic missile can carry 8 475kT warheads, or 14 warheads in any mixture of 90Kt and 5-7kT yields. Most missiles at sea have fewer warheads, because reducing weight increases range, and because of arms limitation treaties.

[Anaraxes]

Originally Posted by edk926

How powerful would the modern nuke be?

Warhead yields have actually been declining, thanks at least in part to improved missile accuracy. The reason nukes got paired with ICBMs in the first place was because the early rockets could just about hit a city-sized object on a good day. So, you needed a big explosion to hope to catch whatever your actual intended target was somewhere in the circle of destruction. With a more accurate missile, you can shrink the warhead and still keep your intended probability of killing the actual target.

That combines with the development of MIRVs -- multiple warheads per missile. Smaller and lighter warheads means you can put more of them into the same launch platform. And, mathematically, scattering a bunch of small explosions around an area is more efficient than trying to make one big explosion that can do the same damage to that area. (A square-cube law kind of effect. You generally don't want deeper craters or to lift more of the atmosphere up higher. And in the surface plane, there's still the inverse square law reducing intensity with distance.)

So, for example, the largest nuke in the US arsenal went from the B41 (25 MT, retired in 1976) to the B53 (9 MT, last one scrapped in 2011) to the current B83 (variable yield from 800-1200 kT). The newest design was a B90 project cancelled in 1991 (ranging from "low kT" to 200 kT, intended for cruise missiles). The Peacekeeper and Trident missiles carry multiple 475 kT warheads.

So, while modern tech could likely build a more powerful mine-is-bigger-than-yours bomb than the largest ever (USSR's 1961 Tsar Bomba test, est 50-60 MT), that hasn't been a goal. The tech trend led in different directions than a bigger boom.

[Rupert]

Originally Posted by Anthony

A megajoule is in the range of conventional infantry missiles.

Also about what the filler in a 60mm mortar shell or a large hand grenade produces.

[sjmdw45]

Originally Posted by Rupert

Also about what the filler in a 60mm mortar shell or a large hand grenade produces.

Or a Mr. Fusion unit on a flying DeLorean.