Nuclear Weapons Accidents- The Broken Arrow Blog.
by Michael H. Maggelet.
The B-52G accident on 24 January 1961 near Goldsboro, North Carolina is another example of unfounded hysteria over a nuclear weapons accident. For decades, claims abounded that one bomb, a Mark 39 Mod 2, "went through five of it's six interlocking safety devices" and was only "one step" away from a nuclear detonation. This is not true.
The following material has been declassified from various documents obtained from DOE and NNSA.
First and foremost, B-52G aircraft power must be applied to the weapon via two crew members using the Aircraft Monitoring and Control System and a specific voltage and amperage (and for a specific amount of time) before the Ready/Safe Switch could be rotated to the "Arm" position.
The pilot of the bomber aircraft controlled power via his T-380 Readiness Switch, which was safety wired and sealed near his seat in the aircraft. The Radar Navigator could monitor the bomb's circuits via the DCU-9, but he could not arm it without electrical input via AMAC nor consent from the pilot. The aircrew, in two physically separate positions in the aircraft, had to perform at least 19 steps from their checklist before nuclear weapons could be pre-armed and dropped.
Bomb 2, the object of the Goldsboro controversy, was not "one step" away from detonation (nor was Bomb 1). The Mark 39 Mod 2 had two additional safety switches, the Trajectory Arm Switch and Rotary Safing Switch. It should be noted that aircraft power to monitor and pre-arm the bomb is separate from power supplied by the bomb's short life thermal batteries.
In Bomb 2, the High Voltage Thermal Battery was not activated, so no electrical power could reach any components necessary to fire the weapon and produce a nuclear explosion. In any regard, the R/S Switch, Trajectory Arm, and Rotary Safing Switch prevented any current from reaching the X-Unit.
While the Ready/Safe Switch in Bomb 2 showed "armed" after recovery, it was actually safe, and post mortem examination by the AEC proved it to be electronically open (the housing having been destroyed during impact). Most importantly, the high voltage necessary to fire bomb components was not present for bomb 2.
In Bomb 1, the HVTB did activate, however the three safety switches, the MC-772 Ready/Safe Switch, the MC-732 Trajectory Arm, and the MC-788 Rotary Safing Switch prevented any voltage to reach components necessary to arm and fire the bomb. The arming and firing sequence is quite complex, and much more was required to produce a nuclear explosion.
It should be noted that in several other accidents, thermal batteries were activated due to severe ground impacts. In all cases, from lightning strikes to accidental jettisonings to crashes, the safety features, although not as advanced as today's nuclear safety concepts, were well designed, tested, and robust.
Documentaton obtained through the Freedom of Information Act, including copies of the original AEC and EOD reports, are available in "Broken Arrow, The Declassified History of Nuclear Weapons Accidents" by Michael H. Maggelet and James C. Oskins. It should also be noted that Bomb 2's secondary, containing uranium and lithium, was not recovered and poses no detonation hazard.
How close was the Goldsboro bomb to producing a nuclear explosion? Not at all.
An excellent, authoritative article. Clearly written with the benefit of great technical expertise and contemporary, hands-on experience of precisely the sort of weapons and systems under discussion.
ReplyDeleteI wonder why it is that Eric Schlosser doesn't appear to have a blog of his own on the subject and we must instead rely on lib/left shills such as The Guardian, the BBC and other commercial media who seem only too happy to reproduce the Goldsboro Myth pretty much verbatim and without comment. Of course, the story as it is reproduced plays into the mentality of the Fischer Price School of Smug Bedwetters as it makes the US seem like irresponsible buffoons just like that 1960s documentary "Dr. Strangelove."
Well done Mssrs. Oskins & Maggalet. That's one in the eye for the clueless old hippies of this World.
Here's a thought: why is it that when such clear evidence is available that neither Mk 39 bomb was in any danger of exploding, has the hysterical article of doom gone global, seemingly without being challenged?
ReplyDeleteHere is an excerpt which I think should have been easy enough for any reasonably diligent journalist to find:
"Contact fuses for U.S. atomic bombs were developed starting in 1951 and they have often been employed as last-ditch backups to other types of warhead fuses.64 These fuses are also known as "salvage" fuses in that they can "salvage" the bomb and cause it to explode when all other fuses fail. These fuses must function after withstanding extreme deceleration forces and delivery vehicle deformation.65
64 AF ATOMIC ENERGY PROGRAM, Vol. IV, p. 89.
65 Rosengren, RDA-TR-122100-001-Rev. 1, p. 102.
www.ibiblio.org/bomb/hansen.html"
Again, Mssrs. O&M are in lock-step with Sandia and Mr. Hansen on this: they indicate quite plainly that the nose crsytals were both present and "crushed." O&M: bang on as usual with impeccable facts.
So, if all the other fuzes failed and the bomb still didn't go bang (conventionally or otherwise) the bomb obviously was neither armed as a viable nuclear weapon, nor had it run through all the other fuzing processes.
As O&M state: How close was the Goldsboro bomb to producing a nuclear explosion? Not at all.
QED.
Additionally, the Mk 39 bomb's thermal batteries could not be used to rotate the MC-772 Ready/Safe Switch.The X-unit was isolated and housed in the cartridge assembly, which is shielded to prevent any stray voltage from activating components. An inadvertently armed weapon can be safed using the AMAC equipment, or by manually rotating the switch to "safe"- it could not be manually armed. As for the MC-772 being a "cheap" switch, Sandia Corporation designed, tested, and oversaw the production (usually through contactors) for the fuzing and firing components of the weapons.
ReplyDeleteCurrent from the high voltage thermal battery could not charge the X-unit due to the MC-772 and MC-788 safety switches. Additionally, they blocked current from the low voltage nose impact switches (piezoelectric crystals) which could not detonate the weapon (since the X-unit was not charged). Many more components in the X-unit would have to be charged in order for a nuclear detonation to take place, and the sequence of operation was blocked by the two safeties (which were electrically operated solenoids). Info declassified from SNL history documents on the Mark 39 and Defense Special Weapons Agency technical safety review.
Some background on the production complex in the early days-
Atomic Weapons Orientation Part One - Organization for Atomic Energy
http://www.youtube.com/watch?v=X5hcWL4IuoM
Hi Michael,
ReplyDeleteI'm doing a story for the BBC and can you please email me at arif.mahmood@bbc.co.uk
Thanks,
Arif
What were the risks of the impact of the bombs creating a critical mass purely physically, rather than electrically?
ReplyDeleteI'm no expert, but the odds seem probably almost nil.The subcritical masses tend to repel each other as they approach each other due to the energy of the increased local fission as the density of fission-triggering free neutrons increases as the masses get closer. A very precisely shaped and timed implosion is required to overcome this repulsion,and this seems unlikely to happen without precise electrical triggering of the implosion.
DeleteClarification: In my above reply "the density of fission-triggering free neutrons increases" means that their number per unit volume increases because, as the masses get closer, more of the neutrons escaping from one of the masses now enters another mass instead of getting lost from the system entirely.
DeleteThe real issue is that this article is dated March 2013, and thus predates the September 2013 declassified document in which expert Parker F. Jones (not mentioned in this article) is shown to have written that it 'seems credible' that a short circuit in the ARM line during a mid-air breakup of the aircraft 'could' have resulted in a nuclear explosion. No precise estimate of this risk is given and it does not seem all that great,at least to me (though a smallish risk of a huge catastrophe can still be worrying,though hopefully safety has been much improved over the subsequent 60 years). But it also seems a rather greater risk than that seemingly implied by this article's claim of '19 steps away'.
DeleteJim Oskins and I are both familiar with the Parker F. Jones document, which brings up some interesting points, but falls short when the facts are examined. As noted above, the status of individual weapon components clearly shows that Bomb 2 could never have detonated, not only because the MC-778 and MC-772 safety switches were SAFE, but the MC-641 High Voltage Thermal Battery was not actuated.
ReplyDeleteI don't know of a single incident involving inadvertent arming of the MC-788 or MC-772, nor charging of the fire set in an incident involving a nuclear weapon in US military custody (test weapons do not count, for obvious reasons). There were about three dozen "arming" incidents which were due to inadvertent electrical shorts, due to smashed pins on cable connectors (load crew errors), or unintentional activation of the AMAC by the aircrew (or AMAC fault). In all cases, only the switch stepped to "Ready" or "Arm", but the weapon was not armed (did not have a charged fire set or X-unit, which is required for detonation). Additional safety devices such as timers, baros, velocity switches, inertial switches, etc., were designed to prevent the X-unit from charging.
There are tons of documents online listing nuclear safety improvements over the decades to include unique signal generators, PAL, etc.
Yours, Michael H. Maggelet