Could fission-based nuclear explosives be competitive in yield/weight with fusion nowadays?

[Pds314]

Is it possible for a boosted fission device with a fissionable or fissile component outside the main implosion device, or even a pure implosion device using modern technology, to come close to or match modern day moderate yield fission- fusion-fission devices? Like 300 kt range? What's the highest yield/weight that's been achieved with pure or boosted fission? Would density advantages help it achieve parity in a reentry vehicle even if it couldn't achieve parity on its own?

Edited May 15, 2020 by Pds314

[K^2]

If you just go by total yield, it's not even a competition. Even if we limit the discussion to devices that have actually been built, fusion bombs have over a hundred times the yield of fission-boosted ones, and theoretical is well into thousands times difference. There is just no reason to even test a device with several hundred megaton yield, which is why one hasn't been built, but all indication is that we could build one if needed. Fission-boosted devices are limited to sub-megaton range, and in practice, none have been built that are even close to a megaton.

Now, if you're working with limited weight and size, that's where boosted fission can shine. Very often, you don't need more than 200kT per warhead, and boosted fission devices perform great in that range. Likewise, if you want to fit a nuke into an artillery shell or a backpack, you want to go with something small and light, which probably means a fission device.

[kerbiloid]

https://en.wikipedia.org/wiki/Ivy_King

1952, Ivy King, 500 kt, the yieldest fission test, a backup option for the Ivy Mike if it fails.

http://www.sonicbomb.com/modules.php?name=Content&pa=showpage&pid=180

http://sonicbomb.com/modules.php?set_albumName=nuke_us&op=modload&name=gallery&file=index&include=view_album.php&page=4

Edited May 15, 2020 by kerbiloid

[magnemoe]

6 hours ago, K^2 said:

If you just go by total yield, it's not even a competition. Even if we limit the discussion to devices that have actually been built, fusion bombs have over a hundred times the yield of fission-boosted ones, and theoretical is well into thousands times difference. There is just no reason to even test a device with several hundred megaton yield, which is why one hasn't been built, but all indication is that we could build one if needed. Fission-boosted devices are limited to sub-megaton range, and in practice, none have been built that are even close to a megaton.

Now, if you're working with limited weight and size, that's where boosted fission can shine. Very often, you don't need more than 200kT per warhead, and boosted fission devices perform great in that range. Likewise, if you want to fit a nuke into an artillery shell or a backpack, you want to go with something small and light, which probably means a fission device.

Yes, today most nuclear bombs are in the 150-400 Kt. The huge megaton bombs was mostly useful then accuracy was measured in kilometres and target was primary cities. 

Very small bombs has low yields as in below one kiloton. They are not fielded today, far higher risk for them to be stolen or you have an accident with one and why. If you need an nuclear bomb an ICBM is 30 minutes flight away. 

Fun note in that the fatman in fallout 3 and 4 is less lethal than real weapons at the same size like an 120 mm mortar shell
Still mad nobody made an mod with an craft combining an fatman launcher, an pogo stick and orion pulse engine
Would be a bit like the fortify jump 8*100 for 3 second back in Elder scroll Morrowind , but you could do more jumps in the air. 

[Nothalogh]

7 hours ago, K^2 said:

There is just no reason to even test a device with several hundred megaton yield

Sure there is, to film it with the best of modern imaging technology

[kerbiloid]

A typical silo can withstand 20..30 kt at several meters above or ~200 kt at 100-200 m.

So, if the accuracy is about the silo diameter (i.e. ~10 m) and allows a direct hit, and if the warhead can penetrate the ground down to several meters depth, there is no need in something above subkiloton range to destroy the silo.
Also this means the fallout will be only local, a kilometer wide radioactive spot, and no light or direct radiation at all.
And as it's weak, it can be made of pure uranium, gun-type, and be more clean than a plutonium one.

An industrial plant is many times weaker, so still can be disabled with this, if hit a critical part of it.

There is not much sense in killing a city because modern production requires modern plant, not a million of early XX workers.
And also a million of alive citizens make more problems to the opponent because they need a lot of supplies and are hostages.
So, a weak but accurate hit at the logistics is more effective than a megaton extermination.

So, probably the future nukes will be like Pershing 2's ones, but smaller, and of tactical, subkiloton, yield.
In case of ICBM - manoeuevrable, with hafnium or tantalus ceramics for nosecone and flaps.

So, probably there is no practical competition in yield at all. Just in accuracy and miniaturization

Edited May 16, 2020 by kerbiloid

[RCgothic]

In a chart, no.

Given that the optimum target is iron, there's simply vastly more energy to be gained fusing light elements than fissioning any heavy element.

Edited May 16, 2020 by RCgothic

[K^2]

3 minutes ago, RCgothic said:

In a chart, no.

Irrelevant chart, though. Imagine a world where this was backwards, and you were getting more energy from fission than fusion. And not just per atom, but per kg of fuel. You could still make a fusion bomb that's way more powerful, because there is a limit on how much fissile material you can put into a fission bomb due to criticality. There is no such limit for a fusion device.