The Bulletin of Atomic Scientists publishes their Nuclear Notebook which provides extensive detail on the nuclear forces of the world’s nuclear powers.
As I read through some of their publications, some of the highlights and details will be mentioned.
Up first is the Nuclear Notebook – United States nuclear forces, 2020. The document is about 16 pages long including four pages of references.
Want to make one thing clear at the beginning of this discussion. Everything discussed here and the two follow-on posts is based on open source information described in the above cited article. I don’t have any knowledge about any of the information in this article. Even if I did (and I don’t), anything I knew would be completely invisible in this discussion.
Total inventory
The US inventory of nuclear weapons is estimated by the authors at:
- 1,300 – approximate number deployed or available for ICBMs
- 300 – approximate number available for strategic bombers
- 1,750 – estimated currently deployed
- 150 – tactical weapons based in Europe
- 2,050 – in storage
- 3,800 – subtotal, estimated stockpile
- 2,000 – retired and awaiting disassembly
- 5,800 – estimated total number of nuclear warheads
New START
Article says the New START treaty limits the United States to 700 deployed launchers loaded with 1550 warheads. Currently the US has 668 launchers with 1376 warheads that are counted as being loaded. I think the nuance here is that there are 200 MM-III which are allowed to carry three warheads but currently are only armed with one.
Weapon count
Article has a fantastic table with the data I’ve been seeking. Table 1 provides a tally of all U.S. nuclear weapons. Tidbids summarized and described by me:
ICBMs:
Of 450 silos, there are 50 in reserve status, meaning they are operational but not loaded with either an RV or missile.
Of the remainder, 200 silos are loaded with RV Mk12A which can carry between 1 and 3 W78 warheads with 335 kt yield. All of these are only loaded with one warhead with the other two (400 total) in storage, presumably at the various bases.
Another 200 silos have a Mk21/SERV (security enhanced reentry vehicle) carrying 1 W87 warhead with 300 kt yield.
SLBMs:
There are 240 UGM-133A Trident II D5/LE, which means 20 for each of 12 SSBNs. There are two more SSBNs in refueling status so the 40 SLBMs for those subs aren’t part of the count.
The Trident can be loaded with one of three reentry vehicles.
The Mk4a can carry between one and eight W76-1 warheads at 90 kt each. Inventory holds 1,486 warheads, with estimated 890 deployed. That implies there are 76 on each sub.
The Mk4A RV can also carry between one and two of the W76-2 warhead. Article says the W76-2 is a single stage weapon with yield estimated in the 5 to 7 kt range, instead of two stage which gives the W76-1 the above mentioned 90 kt yield. Article assumes each of the 12 deployed subs carries two of Tridents loaded with two W76-2 warheads, for total of rounded 50 in the inventory.
The Mk5 RV can carry between one and eight W88 warheads at 455 kt. There are estimated 384 in the inventory.
That gives an estimated 1,920 warheads for the Trident. About 890 are deployed.
Now I will make some wild guesses about load outs. If 2 Tridents on each of the 12 deployed subs carry 2 W-76 warheads, rounded to 50, that means about 840 of the other warheads are deployed. That means each of the 12 deployed subs have 18 remaining tubes loaded with on average 4 warheads each.
Bombers:
Article says there are 87 B-52Hs, of which 11 are inactive leaving 76 in the active inventory. Of those, only 44 are nuclear capable.
The B-52H is only rated to carry the ALCM, which is armed with a W80-1 warhead with variable yield from 5 kt to 150 kt. There are 528 of those warheads in inventory, which is 12 for each of the nuclear capable aircraft.
A quick search shows one website which says the B-52 can carry 20 conventional ALCMs, or 12 nuclear armed advanced cruise missiles, or 12 nuclear ALCMs. So I’m guessing the warheads are tallied for a loadout of 12 ALCMs per bomber.
Of the 20 B-2A Spirits, only 16 are nuclear capable.
The B-2A can carry any of 3 gravity bombs. The B61-7 has variable yield from 10 kt to 360 kt. The B61-11 has 400 kt yield. The B83-1 has variable yield from low to 1.2 mt. Yes, that’s megaton. Wikipedia article says the yield can be adjusted from low kilotons up to 1.2 mt. That is the only weapon in the U.S. inventory in the megaton range, with W88 at 455 kt on the Trident as the next largest.
The B-1 is no longer rated as nuclear capable according to the Wikipedia article. Oddly, that article also says the B83 can be delivered by an F-15E, F-16, F/A-18, AV-8B, or F-22.
Footnote says current understanding is 200 ALCMs are at Minot and around 100 bombs at Whiteman. The remaining 550 warheads are in long-term storage.
Nonstrategic:
The article says F-15E and F-16 DCA are nuclear capable. They can carry between one and five B61-3 or B61-4 bombs. Variable yields range from 0.3 kt up to 170 kt for the -3 and up to 50 kt for the -4.
There are 230 of those bombs. Footnote says 150 are in Europe, with 80 of those available for our NATO allies. That leaves about 80 bombs which are stored in the United States
Recap:
A recap of the tally, excluding around 2,000 awaiting disassembly:
| ICBM | Mk12A | W78 | 600 |
| ICBM | Mk21/SERV | W87 | 200 |
| SLBM | Mk4a | W76-1 | 1,486 |
| SLBM | Mk4a | W76-2 | 50 |
| SLBM | Mk5 | W88 | 384 |
| B-52H | ALCM | W80-1 | 528 |
| B-2A | gravity | B61-7, -11 | 322 |
| B-2A | gravity | B83 | |
| fighter | gravity | B61-3, -4 | 230 |
| stockpile | 3,800 | ||
| summary: | |||
| deployed | 1,750 | ||
| reserve | 2,050 | ||
| stockpile | 3,800 |
Summarized by deployed or in storage by launcher shows this tally:
| platform | total | deployed | storage |
| ICBM | 600 | 200 | 400 |
| ICBM | 200 | 200 | |
| SLBM | 1,486 | 840 | 646 |
| SLBM | 50 | 50 | |
| SLBM | 384 | A | 384 |
| B-52H | 528 | 200 | 328 |
| B-2A | 322 | 100 | 222 |
| B-2A | B | B | |
| fighter | 230 | 150 | 80 |
| rounding | 10 | (10) | |
| stockpile | 3,800 | 1,750 | 2,050 |
A – Deployment of W88 warhead on Mk5 launcher unknown; tally is included on previous lines.
B – Count of deployed B83 for B-2A is not listed, so whatever amount are deployed would be offset by a reduced count for B61.