It's basically impossible to assemble an Orion in space because of the size of the pusher plates and reaction springs. There is no way to get that kind of stuff into orbit without a launcher as large and powerful as an Orion. All extant concepts for Orion drive ships have included some form of single-launching, usually using a very large booster stage or sets of solid-rocket boosters. These push the Orion ship onto a suborbital trajectory so it can start using its own pulse drive in the upper atmosphere. These are all in-atmosphere detonations so fallout is very low, and the specialized in-atmosphere pulse units have very small explosive yields and therefore negligible electromagnetic interference.
And it was in fact kind of the whole "point" that created the Orion drive in the first place in getting as much 'spacecraft' into orbit (and beyond) in one launch. The scientist were quite open and honest that building an Orion that you could launch on a normal rocket was going exactly 180 degrees in the wrong direction to use Orion efficiently as they got more efficient bigger they got. Keep in mind they straight up based a lot of the parameters of the concept on the idea of needing to be able to launch a couple of two-ton each barber's chairs into space by a method where that much mass was so far down in the 'margins' as to be ignored. And they based the 'standard' habitation deck section, (which would be spun to provide gravity) on the two-story round cafeteria they all would have lunch at every day.
What was the number? Something like 100 full-up ISS's into orbit in a single launch AS CARGO! When you need vast amounts of material in space as soon as possible Orion is inarguably the way to go ... But that's the problem too as that's also about the ONLY scenario where it shines.
Once you dig deeper as I noted you then need an extensive but more 'conventional' launch system and infrastructure to then support those Orion's and when all is said and done you end up not every needing a whole lot (especially of the early monsters) of those ships unless you have a priority reason to colonize space or another planet RIGHT DAMN NOW. Barring that the Orion drive isn't as effective as other options once you can actually employ those options.
As I pointed out there's still a very viable use scenario for something like GABRIEL, (why is this all in caps? no idea but all the reports have it that way so... ) but the motivation and political backing is iffy at best. Beyond that? Well I do love the concept but getting something where it can be rationalized let alone actually built...
Correction no "Broken Arrow" every resulted in a NUCLEAR detonation Several had the conventional explosives detonate but not in a viable way to initiate a nuclear event.Note that no 'Broken Arrow' resulted with a detonation
Didn't a b52 crash cause 5 of 6 failsafes to fail?
Goldsburo, North Carolina in 1961 but keep in mind the bomb was actually deployed almost exactly as it would be for an actual mission. The "one-switch" was literally THE one that HAD to be electrically turned on by the crew during a bombing run to get the damn thing to work. The rest of the fail-safes (key word btw) functioned as designed due to the bomb falling free and the parachute deploying as it would have for an actual mission. Even if you don't believe that Pentagon story that it wasn't a fully 'functional' device, (almost impossible to believe given the doctrine of the time and the mission itself) without that one switch being activated by the proper sequencing by the crew the bomb simply couldn't get a nuclear yield.
The SECOND bomb's fail-safe WAS activated but none of the other systems were activated since it didn't separate properly, (the power and systems cables were torn in half so the switches could not physically engage) the parachute didn't deploy, (the NEXT major switch that has to be physically activated to fully arm the weapon) and it hit the ground which essentially warped the conventional explosive array to a point where even if they HAD gone off the nuclear core couldn't detonate.
Even our worst designed weapons, (and we've had more than one ) need a lot to go exactly right to get a nuclear yield. And if you're still worried let me assure you that had things gone 'bad' enough when I was in service one of my JOBS was to put large explosive shape charges on those weapons and sit about 300 yards away and ensure they wrecked them before bugging out. Expendable you say? Hardly as we had to be around to not only 'fix' any that weren't wrecked but we had several other "priority" task that had to be done before we truly bugged out. As a side note that's how I got another raise in my security clearance as even though I wasn't a Nuclear Weapons Technician, (they got to leave a LONG time before us "conventional" folks would ) I happened to know how these work and asked some questions. (What can I say, my grade school couldn't afford the 'new' encyclopedia's so we had late 1950s sets and the US at the time was quite 'proud' of our nukes )
Yes I forgot that priority rule about asking questions... I was young and stupid I admit
No nuke was subjected to a rocket blast...
Actually... (https://en.wikipedia.org/wiki/Johnston_Atoll#Failures) and several were in fact touching the high explosives that were supposed to start the chain reaction when those conventional explosives detonated. So, no you're point still doesn't stand I'm afraid.
That... would effectively turn a considerable chunk of real estate into a radioactive wasteland... not to mention all the radioactive dust carried who knows where...
Again this is simply hyperbole and patently untrue. The Kiwi-TNT reactor experiment was far more radioactive than a pulse unit would have been (considering it was run up to full power in under a second or about a gigawatt of thermal energy and blew parts all over the place it was safe to approach by un-suited personnel in less than an hour and cleaned up fully in less than a week. A pulse unit after a crash would be mostly only slightly radioactive hunks of metal. Dust? What dust? The pulse unit casing is designed to actually RESIST the power of the nuclear detonation for a couple of microseconds to help direct the blast, how is a "little" thing like a fall from space inside a heavy hull and lots of rather 'clunky' machinery supposed to generate any significant radioactive 'dust'? Firstly the most likely place this would crash is into an ocean because that's called flight planning and second you seem to be thinking of plutonium 'dust' (which again is pretty hard to get from smashing a piece of metal against a hard surface) and the pulse units only had highly enriched uranium in them.
Still not getting where you got this from as the material available is pretty clear.
Bomb grade material really isn't that radioactive.U-235 has a half life of 700 million years. Radon gas in Many people's basement is under 4 days.
Yeah... but it wouldn't be one bomb, would it?
it would be hundreds in total with about 50 to 100 in each "storage and handling" cassette, which themselves were built in essentially a shipyard with heavy walls, (seriously the walls were about a foot thick outside and had a lot of internal bracing all around to support the storage and and handling machinery along with the pulse units) and bracing to with stand multiple G's of acceleration. Then as noted you have the pulse unit casing itself to deal with.
Oh and lets address the one thing that everyone seems to get wrong. What is the most likely method of failure of an Orion drive ship?
First an aside: Well unlike a conventional rocket filled with tons of very volatile liquid chemicals and stored in a light weight pressure vessel, the Orion drive by it's nature has to be built less like a 'rocket' and more like a ship, a 'real' space ship if you will. So by their nature the former will tend to explode or fall apart during a catastrophic event.
Fair enough so far. What about Orion? Think about it for a moment. It is literally riding to orbit on successive nuclear blasts and by design a MAJORITY of the blast is directed at the Orion itself. In other words it is literally built from the ground up to stand up to multiple close proximity nuclear explosions as a common event. It has no major amount of those afore mentioned volatile propellants nor does it have the light weight tanks they are normally contained in.
What's the "main" mode of failure? Oddly enough your main worry is, not the first nuclear pulse unit but the second and subsequent units NOT going off! Because if they don't then you suddenly recall that gravity works and the ground/ocean is a long, long way down there. Result? Drop the battleship Iowa, from 10 miles up and you get a pretty good idea probably. Again literally because the Iowa would have nuclear armed cruise missiles on-board which while smashed flat are not likely to scatter highly radioactive material all over the place or explode.
That's probably THE most difficult thing for anyone NOT interested in space/Orion to understand. You are not talking about a huge but frail Saturn V or even a Nuclear powered vehicle like a NERVA. You are talking about something built (likely) stronger and heavier than a WWII battleship pushed into space by sequential nuclear explosions that is totally unlike anything anyone has ever actually seen.
This is something that carries several multi-ton barbers chairs in dedicated barber shop, which sits inside a habitation deck with walls somewhere around 6 inches of solid steel surrounded by a 'dead-space a couple of feet thick with radiation absorbing material surrounded by ANOTHER 6 inch solid steel outer wall which is stacked among about a dozen similar decks, a cargo hold that can carry enough material for 100 ISS's and about a dozen more 'decks' above it all in descending size with accommodations and capacity for about a thousand 'crew' of passengers, scientist and flight personnel all of which then sits on top several dozen more tons of pulse unit storage and handling magazines, shock absorber systems and other machinery which then "finally" sits on a multi-ton "pusher" plate about 20 feet thick.
The Saturn V, N1, hell the NOVA takes one look and dies of embarrassment...
You know the tyranny of the rocket equation and the mantra "every kilogram matters"? Well the Orion drive doesn't even care, not one bit