# Whats the advantage of an H-bomb over an A-bomb **URL:** \ **Category:** Factual Questions\ **Created:** [December 14, 2002, 10:59pm UTC](https://boards.straightdope.com/t/whats-the-advantage-of-an-h-bomb-over-an-a-bomb/142800 "2002-12-14T22:59:04Z")\ **Posts on this page:** 11\ **Page:** 2
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [December 16, 2002, 10:32pm UTC](https://boards.straightdope.com/t/whats-the-advantage-of-an-h-bomb-over-an-a-bomb/142800/21 "2002-12-16T22:32:23Z")
> [@](#): > > \*Originally posted by pravnik \* > \*\*Yowza!! I hadn’t heard that, **Revtim**! That is potentially great news! \*\* Not really. Sorry to continue the hijack but controlled fusion reactions have already been achieved adn were achieved many years ago. The tough part is keeping the reaction going. So far it has taken a greater input of energy to get the fusion reaction started than is extracted. Once they figure how to keep the darned thing chugging along indefinitely we should get excited. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [December 17, 2002, 12:12am UTC](https://boards.straightdope.com/t/whats-the-advantage-of-an-h-bomb-over-an-a-bomb/142800/22 "2002-12-17T00:12:03Z")
> [@](#): > > All Hydrogen bombs require a fission reaction (i.e. an A bomb) to start the fusion reaction. I don’t beleive it’s so. I hear that a fusion ‘bomb’ cound be done with conventional explosives but the quantity would be immense. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 17, 2002, 3:18am UTC](https://boards.straightdope.com/t/whats-the-advantage-of-an-h-bomb-over-an-a-bomb/142800/23 "2002-12-17T03:18:32Z")
Another advantage of a boosted fission bomb, in addition to higher yield, is less severe fallout. Just like in chemical reactions, a good part of the pollution is un"burnt" fuel. Burn the fuel more completely, you get less pollution. ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [December 17, 2002, 3:40am UTC](https://boards.straightdope.com/t/whats-the-advantage-of-an-h-bomb-over-an-a-bomb/142800/24 "2002-12-17T03:40:31Z")
**K2Dave** Everything I have ever read on the subject would indicate that you are wrong. Do you have a cite? While I cannot say with absolute certainty that conventional forces (portable enough to call a bomb) can reach the temperatures, and pressures needed to initiate fusion, I would be fascinated to hear what the technology is that could do it. Where did you hear about it? Tris ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [December 17, 2002, 12:04pm UTC](https://boards.straightdope.com/t/whats-the-advantage-of-an-h-bomb-over-an-a-bomb/142800/25 "2002-12-17T12:04:01Z")
> [@](#): > > Do you have a cite? unfortunatly not > [@](#): > > Where did you hear about it? Years back on some cable channel Nova type show (not actually Nova but that theam). I don’t recall if it was actually done or just theoretically possible but do remember that someone claimed it could work. ---
**Author:** ![mrcrow](https://avatars.discourse-cdn.com/v4/letter/m/838e76/32.png) [@mrcrow](https://boards.straightdope.com/u/mrcrow)\ **Post date:** [December 17, 2002, 3:46pm UTC](https://boards.straightdope.com/t/whats-the-advantage-of-an-h-bomb-over-an-a-bomb/142800/26 "2002-12-17T15:46:50Z")
i think you choose the weapon to be strategically effective do you want to destroy or occupy size i feel should be consistent with the target. air bursts and ground bursts would require differing powers to get the mass of material into the atmosphere for ongoing fallout plumes to cover large areas of land so a big bomb? if you want to knock down a few buildings and use initial radiation then size may not be so critical… ---
**Author:** ![Revtim](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/revtim/32/1042_2.png) [@Revtim](https://boards.straightdope.com/u/Revtim)\ **Post date:** [December 17, 2002, 4:02pm UTC](https://boards.straightdope.com/t/whats-the-advantage-of-an-h-bomb-over-an-a-bomb/142800/27 "2002-12-17T16:02:08Z")
Re: using conventional explosives to trigger a fusion H bomb For fusion to occur, you need heat, and if you add pressure you need less heat, correct? If so, then could one at least theoretically devise a really, really powerful chemical explosion such it provides enough pressure and heat? Is there a way to just keep adding/stacking explosive material to a bomb such that the heat and pressure that will be at the center of the bomb keeps increasing? Maybe the bomb has to be the size of the moon, but is it theoretically possible? ---
**Author:** ![Cerowyn](https://avatars.discourse-cdn.com/v4/letter/c/82dd89/32.png) [@Cerowyn](https://boards.straightdope.com/u/Cerowyn)\ **Post date:** [December 17, 2002, 4:08pm UTC](https://boards.straightdope.com/t/whats-the-advantage-of-an-h-bomb-over-an-a-bomb/142800/28 "2002-12-17T16:08:54Z")
There’s also a new generation of [table-top lasers](http://physicsweb.org/article/news/3/4/6) that can generate the heat and pressure required for fusion reactions (but only for pico-seconds at a time). [Here’s another story](http://abcnews.go.com/sections/science/DailyNews/tablefusion990324.html) about using lasers for fission and fusion experiments. ---
**Author:** ![Sofa\_King](https://avatars.discourse-cdn.com/v4/letter/s/58956e/32.png) [@Sofa\_King](https://boards.straightdope.com/u/Sofa_King)\ **Post date:** [December 17, 2002, 5:00pm UTC](https://boards.straightdope.com/t/whats-the-advantage-of-an-h-bomb-over-an-a-bomb/142800/29 "2002-12-17T17:00:23Z")
I remember reading somewhere that most of the fallout produced by a thermonuclear bomb actually comes from its fission “trigger.” The trigger itself is fairly small in comparison to the size of the detonation, and the intermediate fusion reaction helps to more efficiently break down the explosive material. Therefore an H-bomb may be “better” in the sense that for a given explosion size, it produces less fallout than an A-bomb. Here’s a cached [Google link](http://www.google.com/search?q=cache:lRUxLEAmIl8C:library.thinkquest.org/C004606/applications/thermowpn.shtml+fusion+bomb+less+radiation&hl=en&ie=UTF-8) which echoes these sentiments. However, while the initial fallout from an air-burst thermonuclear bomb may be less, I think they produce more gamma radiation than A-bombs do. I don’t know what role, if any, gamma radiation plays in the production of fallout, or if gamma rays can irradiate other materials. ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [December 17, 2002, 5:14pm UTC](https://boards.straightdope.com/t/whats-the-advantage-of-an-h-bomb-over-an-a-bomb/142800/30 "2002-12-17T17:14:39Z")
Gamma rays don’t change other substances into fallout. Fallout is almost entirely matter from the original bomb materials, either fissioned into other still radioactive elements, or irradiated with neutron flux from the explosion core, and thebye changed into radioactive isotopes, or the original material (uranium, or plutonium) which has not been fissioned, and is still radioactive in its own right. Tris ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [December 17, 2002, 7:09pm UTC](https://boards.straightdope.com/t/whats-the-advantage-of-an-h-bomb-over-an-a-bomb/142800/31 "2002-12-17T19:09:53Z")
This is a “upon memory and belief” post and I don’t vouch for the contents, but: There is a definite maximum “size” (destructiveness) to which a fission bomb can be constructed; that limit does not apply to fusion, which can be orders of magnitude higher (independently of the greater energy-per-nuclear-reaction implicit in the binding-energy equations for each). [Previous page](https://boards.straightdope.com/t/whats-the-advantage-of-an-h-bomb-over-an-a-bomb/142800.md?page=1)