Fat Man
Enable an AI agent to identify records and artifacts associated with the historical nuclear weapon called Fat Man, assess their evidential and physical status, and determine appropriate documentation, access and stewardship actions.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to identify records and artifacts associated with the historical nuclear weapon called Fat Man, assess their evidential and physical status, and determine appropriate documentation, access and stewardship actions.
The Fat Man is the United States' first deployed plutonium implosion fission bomb (Manhattan Project Mark III / Mk-3), a 10-foot-long, 5-foot-diameter weapon whose spherical high-explosive lens system compressed a plutonium-239 pit to supercriticality; the combat unit dropped on Nagasaki on 9 August 1945 had a yield of about 21 kilotons.
It can be Resolve whether an incoming Fat Man record concerns the named weapon, a broader designation or a representation.; Link historical claims to evidence and preserve disagreements between sources.; Compare documented exterior features to flag likely misidentification of images or exhibits.; Classify claimed surviving material by provenance and relationship to Fat Man.; Prepare evidence-qualified catalogue descriptions and exhibit labels.; Route proposed handling, examination or display of associated artifacts through documented custodial and specialist requirements..
Distinguishing features
Require evidence connecting the name to the historical weapon referent; a matching label alone does not distinguish it from a fictional namesake.
Determine whether a source identifies the individual weapon, a design designation or a related weapon before treating two records as the same thing.
Use documented exterior features and authoritative attribution together to distinguish Fat Man imagery from imagery of Little Boy or other weapons.
Require object-specific provenance to distinguish an original associated component from a replica, reconstruction or generic display casing.
Distinguish a record of the historical weapon from a currently existing artifact that represents it; a museum display does not establish survival of the original object.
Scope
+ Evidence establishing what the registry name Fat Man denotes
+ Attribution of records, components and artifacts to the named weapon
+ Documented external appearance and non-operational identifying features
+ Historical event associations and custody provenance
+ Present artifact status, interpretation and authorized stewardship
- Nuclear weapon construction, internal engineering and operational procedures
- Other nuclear weapons and the broader weapon design family
- Delivery aircraft as independently modeled objects
- The bombing event, its casualties and its wider consequences as independently modeled subjects
- Weapons programs, institutions and personnel as independently modeled entities
- Replicas, photographs and fictional namesakes as independent objects beyond their relationship to Fat Man
Characteristics
- Referent level
- individual weapon | design designation | associated component | representation | unresolved Prevents the agent from combining facts about different kinds of referent.
- Attribution confidence
- corroborated | single-source | disputed | unsupported Determines whether an identity claim can support recognition or requires further research.
- Documented exterior identity
- source-supported silhouette, markings and visible configuration; unknown where undocumented Supports identification of depictions and artifacts without recording operational engineering.
- Historical event association
- linked event with date, role, supporting evidence and confidence Connects the named weapon to its documented history without making the event part of the physical object.
- Artifact relationship
- documented component of | attributed to | replica of | reconstruction of | depiction of | association unresolved Keeps authentic material, interpretive substitutes and historical representations distinct.
- Physical persistence
- historical object no longer extant | associated material extant | representation extant | unknown Prevents actions appropriate to a surviving collection object from being assigned to a historical referent.
- Artifact safety determination
- not assessed | specialist assessment documented | restrictions documented | not applicable Prevents a historical label or display context from being treated as proof that an associated artifact is safe to handle.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 9 layers · 16 findings · 24 questions.
Fat Man referent Establishes which historical entity the registry name identifies.
Fat Man may be used at different levels of specificity, and those uses must not silently become one physical object.
Name and designation
Separates evidence about the name from assumptions about what it denotes.
Name usage evidence
Record source-specific uses of Fat Man and the referent intended in each use.
- Does this use of Fat Man denote an individual weapon, a design designation or another referent? definition
- Which contemporary or authoritative source establishes that interpretation? provenance
Catalogue identity boundary
Determines whether Fat Man needs a distinct model or a link to an existing one.
Single referent resolution
Record the evidence for keeping this entry distinct or resolving it to an existing catalogue concept.
- Does an existing world model already own precisely the Fat Man referent intended here? boundary
- What evidence distinguishes this referent from related weapons without creating unsupported registry subdivisions? boundary
Exterior recognition Supports identification of Fat Man in historical imagery and collection displays.
Labels, silhouettes and replicas can produce false matches unless visual evidence is tied to an identified object.
Documented appearance
Captures externally visible identifying features with their evidential limits.
Appearance reference
Record which visible features are supported by attributed historical images or authoritative artifact documentation.
- Which documented exterior features distinguish Fat Man from Little Boy and other commonly substituted weapon images? definition
- What source establishes the identity, date and context of each reference image? provenance
Representation fidelity
Separates historical appearance evidence from later interpretive choices.
Replica and image qualification
Record whether a representation reproduces documented features or includes uncertain reconstruction.
- Is the depicted object the historical weapon, a related test object, a replica or an unidentified exhibit? boundary
- Which markings, colors or exterior details are documented, restored, reconstructed or unknown? provenance
Historical attribution Connects Fat Man to documented events and distinguishes direct evidence from retrospective attribution.
A named weapon's identity depends on its historical associations, but those associations must not absorb the event or its participants into the object model.
Event links
Records evidence-qualified relations between the weapon and historical events.
Weapon event association
Record the event, the weapon's attributed role and the evidence connecting them.
- Which sources establish the relationship between the intended Fat Man referent and the Nagasaki bombing? provenance
- Which claims describe the weapon itself, and which belong to the bombing event or delivery aircraft? boundary
Claim resolution
Preserves differences in source authority, specificity and agreement.
Attribution conflicts
Record disputed identifications and prevent repeated secondary claims from appearing independently corroborated.
- Do the sources independently identify the same weapon, or repeat an earlier attribution? provenance
- What additional evidence would resolve a conflicting caption, designation or historical association? action
Material legacy and stewardship Determines what present objects can legitimately be associated with Fat Man and what actions their evidence permits.
Claims about surviving material, museum casings and replicas require different attribution and handling decisions.
Survival and authenticity
Distinguishes the historical weapon's persistence from the existence of related collection objects.
Claimed material connection
Record the exact relationship claimed for an artifact and the provenance supporting it.
- Is this object claimed to be material from the individual weapon, a related manufactured item or a later representation? boundary
- Which custody records or specialist assessments support that specific relationship? provenance
Permitted artifact actions
Connects proposed stewardship actions to the status of a particular associated artifact.
Stewardship action basis
Record custodial authority, assessment status and evidence limits before acting on an associated physical object.
- What documented custodial authorization and specialist assessment govern examination, handling or display of this artifact? action
- What wording can an agent use to describe its relationship to Fat Man without overstating authenticity or implying an unverified safety status? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Combat Fat Man (Nagasaki, 9 August 1945, B-29 Bockscar, yield ~21 kt TNT equivalent)
- Trinity Gadget (16 July 1945 implosion test device at Alamogordo; same design family, not a deliverable Fat Man casing)
- Mark III (Mk-3) production bombs (postwar stockpile of Fat Man-type implosion weapons, 1947-1950s)
- Pumpkin bombs (inert or conventional-explosive Fat Man shape/ballistic replicas used for B-29 practice and combat shape tests)
- Inert museum and display casings (non-nuclear replicas of the Fat Man outer assembly)
- S-site / Y-12 / Los Alamos pre-combat units (unassembled or unused combat-type assemblies such as the unused Kokura/Nagasaki spare)
- Which of these kinds and varieties hold for the sense of Fat Man this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Wikidata - Q48914 - Wikidata item for Fat Man (the Nagasaki implosion bomb / design).
- U.S. nuclear weapon designation - Mark III / Mk-3 (Fat Man) - Postwar stockpile designation of the Fat Man implosion design.
- Manhattan Project unit name - Fat Man (combat unit dropped on Nagasaki, 9 August 1945) - Project nickname; the Trinity test article was the Gadget, not a named Fat Man drop unit.
- Which of these identifiers and schemes hold for the sense of Fat Man this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Atomic Energy Act of 1946 (McMahon Act), U.S. Congress - transferred nuclear weapons from the Army/Manhattan District to the Atomic Energy Commission and classified design data.
- Atomic Energy Act of 1954, as amended, U.S. Congress - continuing statutory control of special nuclear material, Restricted Data, and weapon design information.
- Nuclear Non-Proliferation Treaty (NPT), 1968, IAEA depositary framework - governs non-transfer of nuclear weapons and related technology; Fat Man-class designs remain Restricted Data.
- U.S. Department of Energy / NNSA classification and nuclear-weapon surety directives (and predecessor AEC/ERDA orders) - control of residual Fat Man/Mk-3 design information, pits, and high-explosive assemblies.
- Convention on Certain Conventional Weapons is not the governing instrument; nuclear weapons are governed by national atomic-energy law, NPT, and (for the 1945 combat use) the then-applicable law of armed conflict as interpreted by the United States.
- Which of these standards and regulation hold for the sense of Fat Man this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Combat employment: one unit dropped by B-29 Bockscar (393rd Bombardment Squadron, 509th Composite Group) on Nagasaki, 9 August 1945, after Kokura was the primary target.
- Design proof: the Trinity Gadget (implosion physics package of the same family) was detonated at Alamogordo, New Mexico, 16 July 1945.
- Ballistic and aircrew training: pumpkin bombs (Fat Man shape) were dropped in practice and, in some cases, as conventional bombs over Japan.
- Postwar U.S. stockpile: Mark III Fat Man-type bombs were produced in limited numbers until superseded by improved implosion designs (Mk-4 and later).
- Museum and interpretive display: inert casings and replicas at sites such as the National Museum of Nuclear Science & History, Los Alamos, and Manhattan Project National Historical Park.
- Historical and forensic study: the object is encountered as a type specimen of early implosion fission weapons in technical history, arms-control, and radiation-effects literature.
- Which of these real-world use hold for the sense of Fat Man this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Length (assembled bomb) - about 3.25 (10 ft 8 in class; often cited ~128 in / 3.25 m) - m
- Maximum diameter - about 1.52 (60 in) - m
- Mass (combat unit) - about 4670 (commonly cited ~10,300 lb) - kg
- Yield (Nagasaki burst) - about 21 (often 20-22) - kt TNT equivalent
- Burst height (Nagasaki) - about 500-550 (commonly ~1,650-1,840 ft above ground; figures vary by source) - m
- Plutonium in pit (order of magnitude, unclassified historical accounts) - about 6 (few-kilogram plutonium-239 core; exact mass remains sensitive) - kg
- Which of these typical measurements hold for the sense of Fat Man this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Implosion asymmetry: incomplete or mistimed detonators / explosive-lens errors can produce a fizzle (yield far below design) rather than a full supercritical assembly.
- Pre-detonation / pre-initiation: plutonium-240 spontaneous fission neutrons can start the chain reaction before full compression, reducing yield (a reason for the Trinity test and for Pu-240 limits).
- Delivery and fuzing failure: aircraft abort, weather, or radar/barometric fuze failure can prevent a nuclear burst (the Nagasaki mission already diverted from Kokura for visibility).
- Prompt radiation, blast, and thermal pulse at detonation: the dominant combat and accident-in-war hazards (tens of thousands of deaths at Nagasaki; lingering residual radiation).
- Criticality and contamination hazard of a damaged pit or unassembled core (not a nuclear yield, but lethal radiation and alpha contamination).
- High-explosive hazard of the lens system even without a nuclear yield (conventional HE detonation can disperse plutonium - a dirty dispersal accident).
- Proliferation and design-secrecy hazard: the Fat Man architecture is the historical template for implosion weapons; remaining Restricted Data is controlled for that reason.
- Which of these failure modes and hazards hold for the sense of Fat Man this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- United States: 'Fat Man' is the Manhattan Project nickname; stockpile documents use Mark III / Mk-3; Trinity's device is 'the Gadget,' not Fat Man.
- Japan: the Nagasaki weapon is commonly referred to by the city and date (Nagasaki atomic bombing) rather than the U.S. nickname; Fat Man (ファットマン) appears in technical and museum contexts.
- Russian and other technical literatures often classify it as an early U.S. implosion plutonium bomb rather than by the cartoon nickname.
- The pumpkin-bomb training shape is sometimes conflated with Fat Man in popular accounts; U.S. Army Air Forces usage treated pumpkin bombs as a separate conventional/practice store.
- Which of these regional variation hold for the sense of Fat Man this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Little Boy (Mark I) - Little Boy is a gun-type uranium-235 weapon (Hiroshima, ~15 kt); Fat Man is a plutonium implosion weapon. Separate by fissile material (U-235 vs Pu-239), assembly method (gun vs explosive lenses), casing shape (long thin vs rotund), and target/date (Hiroshima 6 Aug vs Nagasaki 9 Aug 1945).
- Trinity Gadget - Same implosion physics family, but the Gadget was a tower-fired test device at Alamogordo (16 July 1945), not a ballistic Fat Man drop casing. Separate by employment (ground test vs air-delivered bomb) and outer assembly.
- Mark 4 (and later U.S. implosion bombs) - Mk-4 and successors are improved, more manufacturable implosion weapons derived from Fat Man lessons, not the 1945 combat design. Separate by stockpile designation, production era, and internal improvements (levitated pit, better explosives, safety).
- Pumpkin bomb - A Fat Man-shaped conventional or inert store for ballistics and training. Separate by payload (HE or inert vs nuclear physics package) and by 509th Composite Group mission type.
- Thin Man - Abandoned Manhattan Project plutonium gun-type design (long, thin casing). Separate by assembly method (gun vs implosion) and by the fact Thin Man never became a combat weapon; plutonium gun was dropped because of Pu-240 pre-detonation risk.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of Fat Man this model covers, and on what evidence? provenance
Sources
- Manhattan District History, Book VIII, Los Alamos Project (Y) - Volume 2, Technical - Official U.S. Army Corps of Engineers technical history of the implosion design, plutonium pit, explosive lenses, and the Fat Man combat unit.
- Trinity and the Nagasaki mission: Los Alamos technical histories of the Gadget and Fat Man - Laboratory account of the implosion assembly, Trinity test of the Gadget, and the Nagasaki Fat Man drop parameters.
- Nuclear Weapon Effects and the Nagasaki burst (Defense Threat Reduction Agency / DNA historical summaries) - Yield (~21 kt), burst height, and effects characterization used to distinguish Fat Man from Little Boy and later stockpile weapons.
- Manhattan Project National Historical Park - Fat Man and Little Boy interpretive materials - Public, place-based description of Fat Man as a physical object (casing, dimensions, Nagasaki combat use) versus related devices.
What the second pass must settle
- Does vr.tr.fat-man denote the individual historical weapon, a design designation or another named object?
- Does an existing Vercy world model already cover the intended referent and therefore require linking instead of a separate publication?
- Which accessible primary and authoritative sources establish the intended referent's name, historical associations and exterior appearance?
- Which claimed surviving artifacts have evidence tying them specifically to the individual weapon rather than related production, testing or later reconstruction?
- Which recurring identification disputes or exhibit inaccuracies require explicit unresolved claims in the completed model?