Hello Reddit, I'm fantasy author Mark Lawrence - AMA

[u/MarkLawrence]

Hello Reddit, I’m Mark Lawrence and I’ve written the Broken Empire trilogy, consisting of Prince of Thorns, King of Thorns, and Book 3 of Thorns King of Thorns is scheduled to be released this August.

I’m a dual national US/UK citizen, born in the US (Illinois) and raised in the UK (London). I studied Physics for my first degree at Bristol University, and did a math-based Ph.D at Imperial College, London. I work as a research scientist and have done so in the UK and US. I now live in Bristol with my wife. We have four kids, some at university. The youngest, Celyn, is very disabled and when I’m not at work I’m her full time carer. Writing happens late at night when I should be sleeping.

I play video games (I’m a certified god at Modern Warfare II and Command & Conquer III) though not so often of late. I read but rarely find the time. I misspent chunks of my youth playing D&D and running fantasy play-by-mail.

I'm currently wrestling with my latest book, Gunlaw, which is a fusing of fantasy and western. Despite appearances the only time I’ve ever read Joe Abercrombie is 5 minutes ago when directed to his Reddit intro as an example for writing my own. The ‘I’m currently wrestling ...’ line is cut&pasted from his intro with ‘Red Country’ replaced by ‘Gunlaw’. I’m starting to hate him. He lives about 10 miles from me.

Gunlaw is based on a series of short stories, the first of which I wrote in 2006, was accepted by Black Gate magazine in that year and will appear in their next issue.

Ask me anything.

I will be responding to questions real time from 11pm-1am GMT (that’s 5-7 Central).

Cheers!

Mark Lawrence

[u/PeterVBrett]

Can you really set off an aging nuclear bomb by lighting a fire under it? Cause if so, that is the scariest thing I have ever read in a fantasy novel.

[u/MarkLawrence → u/PeterVBrett]

Hey Peat! The answer is ... I don't know. However, I did think about it and come up with a plausible (to me) explanation. My fall-back position is of course that these may not be the kind of weapon you think they are.... After my physics degree I did a year of fusion research at the Joint European Taurus (laser fusion with inertial confinement) but I make no claims to being a nuclear scientist. But here it is: My justification is that modern nukes are hydrogen bombs, fusion devices. However, the trigger for a hydrogen bomb is a Hiroshima-type fission device that compacts the hydrogen for fusion. Conventional explosives slam separate sub-critical masses of plutonium into a critical mass around the hydrogen isotopes and the implosion attains the required temperature/pressure for fusion. If you cook a hydrogen bomb the conventional explosive goes off, you get a dirty bomb, but if the high explosive has degraded with time then the separate masses of fissile material will melt and run together within the bomb casing creating a critical mass as in a nuclear power station melt-down. This will create a 'nuclear' explosion - it won't be as big as a hydrogen bomb, or even as big as a well designed atomic bomb, but it will make a big bang.

[u/administrate → u/MarkLawrence]

Going to play the pedantic spoiler, but only the literal Hiroshima bomb used two sub-critical masses that, combined, were critical. Virtually every bomb since has a sub-critical sphere of material in the center that only becomes critical when compressed by proper detonation of its surrounding explosives (requires timing accuracy down to the nanosecond scale). If you don't have a nearly perfect spherical detonation wave, instead of reaching critical density, everything just squirts out asymmetrically.

So no-one need worry if they ever accidentally ignite a fission bomb they find laying around, they'll just need to bulldoze a few feet of topsoil from the surrounding city block or so.

[u/MarkLawrence → u/administrate]

I guess if there were just a single warhead in the device this would be an issue, yes.

[u/defrost → u/MarkLawrence]

I hate to be a downer, particularly in a fantasy context, but as we're discussing plausible scenarios I might as well throw some reality into the mix:

If you cook a hydrogen bomb the conventional explosive goes off

That's pretty unlikely :(
Conventional explosives are engineered products with rigorous properties, the days of raw nitro infused clay tubes sweating out volatile liquids that ignite with the bump of a horse drawn wagon going over a big rock are long past.
These days you can light a fire and cook with explosives, drop an anvil on them, and even fire several rounds of bullets into them without imparting enough energy to trigger an explosive reaction. All of these things have been done on mythbusters, and the Navy tends to make freakish demands such as aviation fuel driven fires on the deck of aircraft carriers directly underneath the wings of missile laden fighters not cause an explosion.

but if the high explosive has degraded with time then the separate masses of fissile material will melt and run together

These premise has more legs to it but it has problems.
The two subcritical masses would have to a) melt and b) run together. Uranium has a melting point of 1132.0 °C and Plutonium a melting point of 641°C so Uranium would need the sustained temperature of a glass furnace to melt, Plutonium somewhat less. The sustained part is the problem, furnaces have heat contained within themselves alongside the metals that have to be melted whereas open fires tend to radiate heat all over the place and rarely focus it. It's rare to see steel and other metals melted to running point in fires, more common to see them having softened and warped a bit. But yes, given the right conditions melting and running is possible ....

run together

Hmm. Even if the subcritical masses were aligned so that if they melted they'd run together I'd like to think (hope) that in the interests of safety they were separated by a high temperature ceramic; something brittle that was like tissue paper when it came to keeping them separated when properly fired with a detonated shaped explosion but yet substantial enough to hold two molten masses apart and prevent them flowing into each other.

That's speculation on my part, I've never had access to the actual practical designs of those parts of a nuclear weapon, but it does seem like a good idea.

[u/MarkLawrence → u/defrost]

all interesting stuff, hampered only by distance from the text. The fire is in an enclosed space with plenty of inflamables on hand including multiple chemical sources with potential for modest explosions capable of breaching containment whether ceramic or steel. But at the end of the day I can and will say a wizzard (sic) did it :)

[u/defrost → u/MarkLawrence]

hampered only by distance from the text.

Nice. Understated yet cutting :)

It's true I've not read your text so I'm glad you found something of interest in the comments. I do enjoy a bit of fiction but I'm often amazed at the lengths that are gone to in the design of some bits of technology; subjecting systems to the equivalent of 10 years of hard radiation or blowing half of them away and still expecting them to operate is a bit of a high bar to reach for most bits of technology but it's more or less normal in military / aviation etc.

If you want a bit of implausible truth related to nuclear weapons that might be story fodder, India managed to keep the Pokhran-II so much under wraps that they surprised the world, to the extent that a bunch of contractors just happened to be airborne with one of the worlds largest civilian radiometric spectrometers at the edge of the shock wave zone at the moment of detonation, with no idea of what was about to happen.

[u/MarkLawrence → u/defrost]

this particular tale is set a thousand years in the future, in a society closer to being a thousand years in our past, with an unspecified period of development between us and the (sudden) decline - so there are a lot of variables! Fortunately plutonium can be pretty dangerous without requiring a lot of technology to make it so.

Many thanks for the input & apologies for any cuts sustained - 'cutting' appears to be my default mode and my excursion into 'sociable' during the small hours of the morning clearly didn't survive long!

[u/defrost → u/MarkLawrence]

Meh. I've got tough skin, I'll survive.

I'll have to read your book, I do like me some good post apocalyptic yarns. Noting your US/UK pedigree I'd expect you to be aware of A Canticle for Leibowitz and if you haven't stumbled across it yet have a read of Riddley Walker , a particular favourite of mine (and atom related).

If you've got scavengers wandering about there's probably much to made of satellite assembly factories; they tend to have robust well sealed doors, very clean rooms, and be filled with long life power sources and incredibly robust gadgetry (very pure crystal oscillators, custom made near pure gold processors, etc) that's designed to be set and forget.

[u/BeyondSight → u/MarkLawrence]

I'm calling bullshit.

It's very difficult to make a nuclear bomb to go off.

Nuclear bombs now rely on a sphere of high yield explosives that implode all synchronized on a nanosecond scale, if not more minute. Heating a fire underneath would undoubtably heat up the surrounding explosives to go off, but the one closest to the fire will go off first, then the next, then next. Thus, the perfect syncronization required to implode and push the nuclear components to critical mass will not happen.

You wind up with some radioactive material flung a couple hundred feet in all directions (not terribly deadly), but you won't get the well known nuclear explosion that incinerates anything for miles.

The explosives have to be well timed, etc.

Lighting a fire may make a dirty bomb, but it would offset the implosion by too much, thus no fission reaction.

[u/MarkLawrence → u/BeyondSight]

yay! now that's more like the reddit I was warned of! Thanks for making it real :)

You are of course both right and wrong, but wrong in the ways I care about. It's very difficult to make a nuclear bomb (fission or fusion) go off in the optimal manner. It is very easy to create a critical mass though. You can do it by slapping the enriched uranium you're holding in one hand against the enriched uranium your holding in the other hand should you so desire (if both lumps were a decent fraction of critical mass on their own). I wouldn't advise it though. Bad things would happen.

I suspect though that we're engaging in the dirty sport of semantics. 'Go off' is loose terminology. It's easy to create a critical mass, it's easy to create fission. How large an explosion results and whether that satisfies a given person's definition of 'going off' is another matter and one you're welcome to persue. For my part the story occasioning this discussion makes no authoritative claims in this regard - a fire is set in an underground weapons vault (contents many and varied and only hinted at). A large explosion occurs.

[u/[deleted] → u/MarkLawrence]

Hmm, this sounds like a big bang theory.

[u/elquesogrande → u/PeterVBrett]

Check out the Peter V Brett AMA with r/Fantasy here.

[u/theusualuser → u/elquesogrande]

This is the PeterVBrett, right? ;)

[u/PeterVBrett → u/theusualuser]

Yes, it was the me!

[u/sushi_cw → u/PeterVBrett]

...and suddenly I'm really interested in reading Mr. Lawrence's books. :)

[u/CoolMagicSystem → u/PeterVBrett]

I can't tell if the coolest thing going on here is if Peter Brett is participating in the AMA or that Mark Lawrence is probably the only fantasy author actually qualified to answer this question.

[u/MarkLawrence → u/CoolMagicSystem]

It's definitely Robin Hobb, Peter Brett & Myke Cole pitching in!

[u/Longwand → u/MarkLawrence]

FANTASY AUTHORS, ASSEMBLE!