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Experimental MIRV (Fallout 3)

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For an overview of the M42 "Fat Man" Launcher throughout the Fallout series, see Fat Man.
Experimental MIRV
Fat Man.png
Fat Man icon.png
SkillBig Guns
Attack statistics
80 (89) + 12800 (13445) ExplosionIcon explosion.png
10 (11.1) + 1600 (1680.6) ExplosionIcon explosion.png
20336.2 (21368.8)
DPS (reload)
3544.9 (3724.9)
Crit Dmg
Crit % Mult
Ammo & reloading
Ammo TypeMini nuke
Ammo Cap.8
Reload Time
Item HP300
Fat Man
QuestsKeller Family Refuge
Editor ID?
Base ID0003422b
Perk Effects
Perks (dam.)
Bloody Mess
(+4 +640 ExplosionIcon explosion.png)
Ghoul Ecology
(+5 +5 ExplosionIcon explosion.png)

The Experimental MIRV is a weapon in Fallout 3.


The following section is transcluded from Fat Man. To modify, please edit the source page.

The M42 Fat Man was developed at Fort Strong near Boston, Massachusetts. Development began in February 2076, with the goal being the development of a man-portable tactical nuclear launcher easy enough for use by troops on the ground, to destroy reinforced and entrenched positions.[1][2] Problems manifested instantly, as warheads were simply too heavy to clear the blast radius fast enough to provide safety for the operator. Even stripping them to the minimal possible size failed to produce an acceptable effect. Instead, the development team decided to increase the power of the launcher unit, even considering using railgun technology to accelerate the warhead. The notion was largely academic, as it would require for the overburdened soldier to carry an additional power pack the size of a suitcase and turn the Fat Man into a crew-served weapon.[3] Concurrent development ran on the MIRV version of the launcher. Live-fire testing claimed lives, in fact, with two soldiers killed during a test. No remains were recovered and the commanding officer in charge of the project, General Brock, covered up the incident, ordering his subordinates to send sand packed in an urn to their relatives.[4]

The project hit a breakthrough in December 2076,[5] when the project lead discovered a solution for the launcher problems. Six hours, fourteen cups, and one concerned night shift lab crew later, the future M42 launcher was conceptualized: Based on the spigot mortar mechanism, the launcher would only have to accommodate a firing through and system, relying on mechanical launching, rather than chemical or electrical means. Much like the 130 year old PIAT launcher, the Fat Man warhead would be propelled by a sub-charge embedded inside the warhead, "catapulting" the warhead through the air to the target - giving plenty of range with the added bonus of not producing a smoke trail that could reveal the firing team to the enemy.[6]

By September 2077,[7] after one hundred test firings the weapon were complete and ready to be shipped to units overseas. A large number of units was manufactured and shipped together with the appropriate warheads to select locations throughout the United States.[8]


Named for the multiple independently targetable reentry vehicle (MIRV) ballistic missile payload, this variant of the M42 "Fat Man" Launcher fires eight mini nukes at once, arguably making it overkill for any application due to its more plentiful payload and larger spread.

Gameplay attributes

The experimental MIRV is a unique Fat Man that can be found in the bomb shelter area in the National Guard depot. This weapon deals the most damage in the entire game as it acts like a shotgun version of the Fat Man delivering eight mini nukes at once. The MIRV actually does the same damage as a Fat Man per mini nuke, as 12880/8 equals 1610. This means that the MIRV is simply a Fat Man with extra capacity and increased ammunition usage. However, the MIRV can only shoot all eight mini nukes at once, even if seven are loaded it will not fire them.



Name Type Dmg/shot DPS Att/sec Crit mult Crit dmg Spread AP cost Ammo Ammo cap Weight Item HP Value
Fat Man Tactical nuclear catapult 10 + 1600 ExplosionIcon explosion.png 2542 1.6 x0.0 0 2.0 65 Mini nuke 1 30 100 1000
Experimental MIRV Tactical nuclear catapult 80 + 12800 ExplosionIcon explosion.png 20336.2 1.6 x0 0 13.0 65 Mini nuke 8 30 300 2498


The player must complete the unmarked quest Keller Family Refuge before they can gain access to the secure section of the depot housing the weapon.

It's also possible to gain entrance to the armory by using a glitch.


  • The MIRV looks identical to the Fat Man, meaning only 1 mini nuke appears to be loaded on to the weapon; however the game overlaps all eight mini nukes which separate upon exiting the weapon.
  • Sometimes the MIRV (or Fat Man), is set up such that using it in V.A.T.S. will cause the player to aim directly at the enemy, without aiming upwards to compensate for the distance. This, coupled with the fact that only the 8th nuke shot out of the MIRV will go as far as the Fat Man's single nuke (and all other nukes will travel shorter distances) means that using the MIRV in V.A.T.S. can sometimes cause the player's death.
  • If you look directly at the ground and fire the MIRV, the 8 mini nukes' combined power is enough to launch your dead body to the height limit (roughly the height of Tenpenny Tower).
  • Similarly, the MIRV can potentially send the bodies of human enemies hit by multiple mini nukes flying hundreds of feet into the air, potentially rendering their bodies impossible or very hard to find. Keep this in mind before using the MIRV on an opponent whose body you want to loot.
  • It costs more to fire this weapon once than it does to repair a regular Fat Man twice. At several hundred caps per nuke and firing eight nukes per shot, this is the most expensive weapon in the game, albeit the most powerful.
  • Depending on your game system, its age, and the amount of excessive use of the MIRV, it may cause your system to lag and possibly crash.
  • Out of every weapon in Fallout 3 and Fallout: New Vegas, the MIRV is the most powerful in terms of base damage.

Behind the scenes

MIRV is a military term for Multiple Independent Reentry Vehicle (or Multiple Independently Targetable Reentry Vehicle). It is a collection of nuclear weapons carried on a single intercontinental ballistic missile (ICBM). Using a MIRV warhead, a single launched missile can strike several targets, or fewer targets redundantly. The MIRV system was developed throughout the middle of the 20th Century, and one of the main ideas behind the weapon system was to take out an enemy country with a single missile attack before the enemy nation could be able to respond.


  • Xbox 360Icon xbox360.png Sometimes a graphics error can occur when detonation is very close. It can cause large, black rectangles to extend from the weapon out to as far as you can see. A console restart will fix this.
  • Sometimes acquiring this weapon may lead to a crash every time one accesses Tenpenny Tower.
  • Xbox 360Icon xbox360.png Sometimes when lifting the item, it will twirl around in the air, making it very hard to decorate your Megaton house or Tenpenny suite with it.



The following section is transcluded from Fat Man. To modify, please edit the source page.
SingleShotVB.png ReloadVB.png