Wikipedia:Reference desk/Archives/Science/2018 June 2

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June 2

Nuclear bombs and the Tunguska event

I'm all confused about mt and kt etc. In a nuclear war, would the bombs be as bigger or smaller than the Tunguska event?

Links:

• Tunguska event
• List of nuclear weapons

Many thanks, Anna Frodesiak (talk) 04:17, 2 June 2018 (UTC)

In the modern era probably smaller but higher destruction per megaton due to carpet bombing each city with many small hydrogen bombs instead of the giant Tunguska plus bombs of a long time ago. Firing the world's arsenals is much worse than Tunguska both in destruction and sum of megatons but there's asteroids much worse than a nuclear war. Sagittarian Milky Way (talk) 04:38, 2 June 2018 (UTC)

Did you just say carpet bombing with hydrogen bombs? Tell me you didn't say that. Anna Frodesiak (talk) 05:09, 2 June 2018 (UTC)

A big nuclear war would be thousands of warheads, if it's important to hit metro area X it's going to get sent many (partially to try to overwhelm missile defense systems)). Sagittarian Milky Way (talk) 06:12, 2 June 2018 (UTC)

Smaller, much smaller. There was a time when very large nuclear weapons were actually in service (many of the largest explosions were just tests). The B41 nuclear bomb was the largest ever fielded by the United States, a 25 mt bomb of which 500 were built, serving from 1961 to 1976. So during this time, sure, a nuclear war could see the use of bombs about as powerful as the Tunguska Event. The US also had around 340 of the B53 nuclear bomb with a 9 mt yield. This was served from 1962 until 1997, but it was actually intended as a bunker buster, not a strategic weapon - it would actually detonate on the surface for maximum energy transmission to the ground, rather than in the air for maximum blast radius. Though it could also be used as a strategic weapon if desired.

With both of those phased out, the largest bomb in service in the US is the 1.2 mt B83 nuclear bomb. As SMW said, the modern strategy is many smaller bombs. In part it's just more efficient, since the actual goal is usually to take out specific military targets rather than entire metropolitan areas, and also modern bombs and missiles are far more accurate. See for instance the B61 nuclear bomb which replaced the B53 has a yield of only 340 kt, not even 4% of its predecessor. It can get away with this because the bomb can delivered virtually on top of its target. The "many smaller bombs" strategy also makes anti-missile defense a lot harder. Someguy1221 (talk) 05:07, 2 June 2018 (UTC)

You say in the past a big bomb would be about as big as the Tunguska Event, understood. You also say that targets today are not cities, but military targets. That's a bit of good news, at least. Anna Frodesiak (talk) 05:12, 2 June 2018 (UTC)

Even in the past, the targets were always theoretically military. Even in the bombings of Hiroshima and Nagasaki, military value of the targets was considered, though of course the shock value was most important. But regardless, there was a problem with delivery. At the time, an error of half a kilometer was not unusual for an aviation bomb under poor conditions, and good conditions for bomb delivery tended to also be good conditions for shooting a plane down. Since military targets are likely to be much more heavily built (i.e. thick, reinforced concrete, and large underground sections), the effective radius of a nuclear weapon for destroying a military structure is much smaller than its radius for destroying civilian structures. This meant the bombs had to be enormous to catch the target in its blast radius despite the inaccuracy, especially if you wanted to strike multiple military targets at once, and cities just become collateral damage. All factors considered, it was simply unlikely for a large city to not be close enough to a military target that it would be annihilated by a strategic weapon. Once you had better technology, as well as other reasons to favor small weapons, that changed. I can use a real example.

I grew up near a retired Air Force base (part of Project Nike) that was only 10 miles from New York City. We learned after the Cold War ended that our town was indeed a subject of Soviet satellite surveillance, and was possibly on a target list at one point. A 25 mt air burst detonation over my house would flatten several towns and cities, and the Big Apple itself would be in flames, but buildings possibly left standing. However, if you could accurately deliver a 340 kt weapon directly to the base and detonate it on the ground, the blast would still annihilate my town, but there would be little destruction beyond. Still sucks for me, though. Someguy1221 (talk) 05:32, 2 June 2018 (UTC)

10 miles from the edge or 10 miles from the center? Cause even 20 miles from the center can still be inside New York City. Sagittarian Milky Way (talk) 06:18, 2 June 2018 (UTC)

10 miles from downtown Manhattan. Ish. Someguy1221 (talk) 06:37, 2 June 2018 (UTC)

Nike sites were Army, not Air Force. -Arch dude (talk) 18:38, 3 June 2018 (UTC)

You are correct! Wow, I'd always assumed that since it was a nuclear missile, it was Air Force. But yes, the base was operated by the US Army and the Army National Guard. Someguy1221 (talk) 23:19, 3 June 2018 (UTC)

ICBMs have also gotten more accurate. In the table at Comparison of ICBMs, the last column "CEP" stands for Circular error probable: the radius within which 50% of shots fired are expected to land. Early launch systems had a CEP measured in kilometers. (The first successful Soviet ICBM, the R-16, had a CEP of 2.7 km.) If a 'good' shot is one that doesn't land more than a couple of miles from where it was aimed, there are two ways to make sure you still destroy your target: launch lots of missiles, or use really big warheads. As our ability to aim precisely improved, the bombs tended to get (relatively speaking) smaller. TenOfAllTrades(talk) 13:51, 2 June 2018 (UTC)

The Soviets started development on an actual "Doomsday device", but they apparently decided that it actually was an insane idea. [1], [2], [] -- I haven't got the time to check the details from these articles, but it would have been perportedly sufficient to literally blow-up the earth. —2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 22:29, 2 June 2018 (UTC) -- Postscript: those articles relate to a system that the Soviets and/or Russians possibly actually did develop; there's a project that was cancelled (forgot name) that would have consisted of the largest-bomb-ever, on a barge -- there was a PBS documentary on it (mid-'90s?) -G2G:2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 22:42, 2 June 2018 (UTC)

"Literally blow up the Earth" is not something that humans can do. The Chicxulub crater was created by a 100 teratonne explosion (that is 100,000,000 megatons), and while that killed 90% of living animals, as you can see the Earth is still here. Someguy1221 (talk) 22:54, 2 June 2018 (UTC)

But that is why we need to develop the Solaronite, so that we will be able to! --76.69.118.94 (talk) 23:50, 2 June 2018 (UTC)

• Until the development of the MIRV, an ICBM delivered only one warhead, so an ICBM directed at a city needed a really big weapon. A bunch of smaller weapons with the same total mass is a whole lot more effective, even though the bunch has a lower total megatonnage. For the earlier aircraft-delivered bombs, You pretty much wanted to have one big bomb because the aircraft was likely to be shot down. You sent ini as many aircraft as you had, and each tried to reach its one target. It was MAD. -Arch dude (talk) 18:35, 3 June 2018 (UTC)
• Your question is "in a nuclear war". If you mean a nuclear war today, the bombs are clearly smaller than the Tunguska event. If you mean a theoretical past nuclear war, then a very few of the bombs might have approached the size of the Tunguska event, but probably not: we don't have complete knowledge of all bombs ever developed, and some might theoretically be of that size. If you mean future nuclear wars, there are multiple possible ways to use really big bombs and there is not much to constrain the size of the weapons. -Arch dude (talk) 20:53, 3 June 2018 (UTC)

Thank you all for the very thoughtful and informative answers. They are much appreciated.

If aliens come now, we are going to look so stupid. Never mind the nukes. We will literally all die of embarrassment. Anna Frodesiak (talk) 23:02, 3 June 2018 (UTC)