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Nuclear Brief April 2005 (updated July 14, 2005)

The Birth of a Nuclear Bomb: B61-11

The history of how the first U.S. post-testing nuclear weapon, the B61-11, was developed and deployed has become clearer following the partial declassification and released of a number of documents by the Department of Energy and Department of Defense under the Freedom of Information Act. Plans to build more "modified" nuclear weapons make it important to revisit how the B61-11 bomb was planned, approved, and produced.

Before the Clinton administration initiated a moratorium on nuclear weapons test explosions in 1992, such experiments served mainly to develop and certify new nuclear weapons. Absent nuclear testing, however, development of nuclear weapons in the future must rely mainly on modification of existing designs and simulation. The B61-11 is the first such example in what over the next decade will rebuild most or all of the warhead types in the U.S. nuclear stockpile.

The B61-11 is significant because it is the first post-testing modification and is significantly different than the weapon it replaced. The B61-11 was first mentioned in public in September 1995 in "Stockpile Surveillance: Past and Future," a report published by the three nuclear weapons laboratories. An obscure footnote on page 11 remarked:

"A modification of the B61 is expected to replace the B53 by the year 2000. Since this modification of the B61 is not currently in the stockpile, there is no Stockpile Evaluation data for it. The B61-7 data can be used to represent this weapon."

At that point the program had already been approved by Congress and underway for two and a half years. After the lab report was discovered by the Los Alamos Study Group and the B61-11 program disclosed to the public, DOE issued a press release on September 20, 1995, which explained that the B61-11 was not a new bomb but simply a modified version of the existing B61-7 to replace the older and unsafe B53. "There is no new mission," DOE assured.

"This is not new, in any way, shape or form," a DOE official told Defense News in March 1997. General Eugene Habiger, then command in chief of U.S. Strategic Command (STRATCOM) further explained: "All we have done is put the components into a case-hardened steel shell that has the capability of burrowing quite a ways underground, through frozen tundra, through significant layers of concrete."

The B53 Nuclear Bomb

The B61-11 officially replaced the B53, a nine-megatons thermonuclear bomb first deployed in 1962. The large yield could destroy facilities buried 750 feet (250 meters) underground.

Nuclear Conception

The B61-11 program initially began on July 16, 1993, when then DOE Deputy Assistant Secretary for Military Application (Defense Programs) Winford Ellis "strongly recommended" to the Assistant to the Secretary of Defense (Atomic Energy) Harold Smith that the B53 bomb be retired "at the earliest possible date." The nine-megatons behemoth, first deployed in 1962, did not meet modern nuclear safety design criteria, DOE said.

A "Quick Look" study of alternatives to the B53 was completed in December 1993 and cited a formal STRATCOM request for a program to replace the bomb.

The government had known about safety issues in the B53 "for twenty years," Sandia Director Paul Robinson stated in 1997. But the brute force of the weapon was considered the only means for holding a few high-priority Soviet underground targets at risk, so public safety was disregarded. Not until the late 1980s did the planners consider replacing the B53 with an earth-penetrating weapon: the Strategic Earth Penetrating Weapon (SEPW). The SEPW program, which examined a spectrum of penetrator designs with relatively large nuclear yields, advanced through Phase II before it was cancelled in 1990 (despite cancellation, some SEPW work continued as late as 1998).

Next on the nuclear drawing table was the W61, a nuclear earth-penetrator warhead based on a retrofitted B61-7 bomb and modified for delivery in a missile. The W61 was proposed as the warhead for the Tiger (Terminal Guided and Extended-Range) II missile (later renamed Extended Range Bomb (ERB), advanced tactical air-delivered weapon, TASM (Tactical Air-to-Surface Weapon), and briefly the ALSOM (Air-Launched Stand-Off Missile). The W61 program received Phase III authorization in 1990 as an interim solution to the target set of the SEPW, but when the TASM was canceled in 1992, the W61 was canceled as well, according to a Sandia report.

B61-11 Chronology


Jul 16: Rear Admiral W. G. Ellis, DOE Defense Programs, asks ATSD(AE) to retire and if necessary replace B53 "at the earliest possible date."

Dec 10: DOE Quick Look study identifies baseline design as modified B61-7 with nose from cancelled W61 program.


Sep 22: Nuclear Posture Review recommends B61-11.

Sep: PDD/NSC-30 directs development of B61-11.

Nov: B61-11 "B61-7 look-alike" concept developed.

Dec: SAF/AQQ, PEO/ST, XOF approve B61-11 concept.


Jan 18: NWCSSC approves baseline design and recommends approval.

Feb 6: Nuclear Weapons Council approves B61-11 concept.

Apr: Congressional committees are briefed.

Jul 18: Congress approves request to start B61-11 effort.

Jul: NWC asks Air Force to lead B61-11 Project Officers Group (POG) to implement project.

Jul: SAF formally tasks B61-11 POG to implement the project and report back in 90 days.

Aug 2: Designers informed by DOE that Congress had approved.

Aug 4: DOE directs Albuquerque and National Labs to begin work on the B61-11 program.

Aug 8: B61-11 Kick-off meeting held at Kirtland AFB.

Sep 1: First draft of Military Characteristics (MC) and Stockpile to Target Sequence (STS).

Sep 6: DOE holds first all-agency B61-11 meeting. First time people in production complex see the B61-11 concept.

Sep 8: First draft B61-11 MC circulated for comments.

Sep 15: Program authorized.

Sep: The B61-11 program is first mentioned in public.

Oct 3: SNLA/DOE proposes accelerating First Production Unit by nine months from August 1997 to December 31, 1996.

Oct 18: B61-11 requirements finalized.

Nov 15: Harold Smith informs NWC that FPU should be accelerated.

Nov 21: ATSD(AE) selects Option 2 (W61-like design) as leading candidate and asks DOE to "devote full resources to this design."

Dec: Final design selected.


Feb: FPU delivery formally accelerated to December 31, 1996.

Apr: Harold Smith states that B61-11 could be "weapon of choice" against Libya

Nov 20: Flight test certification passed.

Dec: B61-11 is accepted as "limited stockpile item" pending further flight tests.


Jan: First B61-11 enters stockpile.

Nov: The B61-11 enters service with the 509 Wing at Whiteman AFB in Missouri.


Oct: ALT 336 begins.


Oct: ALT 349 begins.


Sep: ALT 349 completed and certified.

Dec: ALT 349 recommended for acceptance to the NWCSSC.

Sandia led inter-agency group "to understand more fully the weapon's penetration capabilities."


The B61-11 was certified to meet all requirements, resulting in its acceptance as a "standard stockpile item."

Dec 31: The Nuclear Posture Review Report states that the B61-11 "has a very limited ground penetration capability" and "cannot survive penetration into many types of terrain in which hardened underground facilities are located."


Jul: ALT 336 completed.

Oct: ALT 350 begins.

Phase 6.3 study begun for the refurbishment of the CSA (secondary).


Sep: ALT 350 completion expected.

Oct: ALT 357 start scheduled.


Sep: ALT 357 completion expected.

Managing Political Opposition

Building nuclear weapons was not popular in the early 1990s. After disclosure in the Bulletin of the Atomic Scientists in 1992 that the DOE and nuclear weapons laboratories were working on mini-nukes, Congress decided in November 1993 one month after the Air Force was asked to study the B61-11 to ban any "research and development which could lead to the production by the United States of a new low-yield nuclear weapon, including a precision low-yield nuclear weapon."

As a result, the B61-11 project which was nicknamed "The Duck" because it had identical flight characteristics to the existing B61-7 bomb was not submitted to the Nuclear Weapons Council (NWC) for approval at the time. The Assistant Secretary of Defense for International Security Policy (ASD/ISP) was concerned that Congress would not support it. Conveniently, the Congressional election in November 1994 changed committee chairmanship to one more favorably inclined to reopening the nuclear weapons production line, so the Assistant Secretary of Defense "re-energized [the] project with a strong recommendation that the effort be completed before Congress changed again."

These events occurred at the same time that the Clinton administration completed the Nuclear Posture review in September 1994. The NPR was widely portrayed as reducing the role of nuclear weapons and Deputy Secretary of Defense John Deutch assured Congress that "there is no requirement currently for the design of any new warhead that we can see." He explained that "almost all" nuclear modernization programs had been terminated. Some remained, one of which was the B61-11. In fact, the the NPR Implementation Memo itself specified the B53 be replaced by a modified B61-7 carried by the B-2.

Once the DOD was convinced that opposition in Congress had eroded, things moved fast. The B61-11 project was submitted to the NWC which approved it on February 6, 1995. 

Meeting with congressional committees and their staffs followed with briefings given in April 1995 to the National Security/Defense and Energy and Water Development Subcommittees of both the HAC/SAC and HNSC/SASC.

The initial contact to Congress was made to Senators Ted Stevens and Daniel Inouye and Representatives C. W. (Bill) Young and John P. Murtha. The DOE talking points did not mentioned the earth-penetrating capability, but described the program as an effort to "improve the overall safety posture of the nation's nuclear weapons stockpile." This characterization was derived from the Nuclear Weapons Council decision on the B61-11 program as being "in support of the President's decision (PDD/NSC-30) to enhance the safety of the nation's nuclear weapons stockpile."

The Office of Management and Budget (OMB) was also briefed. On April 7, 1995, Robert Civiak, the Program Examiner in the OMB Energy and Science division, was briefed by Jerry Freedman, Deputy Assistant to the Secretary of Defense for Atomic Energy (Nuclear Matters), and Everet Beckner, DOE Acting Secretary for Defense Programs. Civiak indicated that he wanted to understand what they were doing and "was a bit 'uneasy' with the potential for this to be viewed as 'developing a new warhead.'" Freedman and Beckner assured that it was "not new warhead development" and that "nuclear components are not being modified." The meeting lasted only half an hour.

The justification for the B61-11 program was the need to "improve the overall safety posture of the nation's nuclear weapons stockpile," but DOE did not say explicitly say that the B53 was unsafe. A request for a $3.3 million reprogramming authorization in April 1995, for example, contained the cryptic sentence: "Although it is currently safe...the B53 does not meet current safety criteria." The purpose of the "replacement" program, the request stated, was to "avoid new warhead production."

No one argued with that, and on July 18, 1995 -- two years after the DOE and DOD began planning and designing the B61-11 -- Congress officially approved production of the nuclear earth-penetrator.

As so, less than two months after the United States with a renewed pledge to nuclear disarmament ensured an unconditional extension of the nuclear Non-Proliferation Treaty in May 1995, production of the B61-11 began.

The Work Officially Begins

DOD acted the same day Congress approved the B61-11 program. The Nuclear Weapons Council (NWC) asked the Air Force to head the B61-11 Project Officer Group (POG) and the Secretary of the Air Force asked the B61-11 POG to implement the project and brief the NWCSSC in 90 days on status and milestones.

The DOD also formally asked DOE to join in the joint project to replace B53 with the B61-11. DOE followed up on August 4 by issuing the guidance that directed Albuquerque Operations Office and the National Laboratories to begin work on the B61-11 program. The program guidance to the labs explained that the Air Force B61-11 POG would oversee the program, DOE Albuquerque Operations Office would coordinate and lead the day-to-day field activities, Los Alamos and Sandia would contribute as designers of the B61 and roles in the POG, and Lawrence Livermore would provide peer review of the development activities.

Many of the characteristics of the B61-11 program were agreed to prior to Congressional approval. During a meeting on December 6, 1994, for example, between the DOD, DOE, the Air Force, and the nuclear labs (Sandia and Los Alamos), agreement was reached on modifying the B61-7 bomb, that the B-2 would be the carrier, and that the replacement weapon would be chosen from four different design options. The B83 bomb was also considered as a candidate, but B61-7 was chosen because it was the "most mature" (note that for the RNEP, the DOE chose the B83 rather than the B61).

The official B61-11 kickoff meeting was held at Kirtland Air Force Base on August 8, 1995. The all-day meeting determined the program group structure and the charter for each of the seven working groups: system engineering, cost, testing, environments, logistic support, mission analysis, and surety/reliability. At the meeting, the Air Force gave a briefing on the B61-11 program that summarized the milestones, objectives for the meeting, and showed the following drawing of the baseline conceptual design:

Initial Illustration of B61 Conversion

At the B61-11 kickoff meeting on August 8, 1995, the Air Force presented this comparison of the B61-7 (top) and the B61-11 bombs. The B61-11 design was changed later in the program, adding a drag-cone to the rear and more than 400 lbs to the weight.

According to the meeting minutes, the "baseline design meets weight, CG and roll momentum requirements for the B61-7." The pitch and yaw were "about 10% high," however, but "calculations indicate the delivery profile and CEP will not be affected." The next step in the program would be development of the Military Capability (MC) and Stockpile-to-Target-Sequence (STS) documents as well as classification guidance for the weapon. MC and STS review was performed by an Environments Working Group under the B61-11 POG to reflect the "unique requirements of the B61-11."

The four different design options were based on four different variables: mission capability, cost, B-2 risk, and schedule/complexity. Mission capability was rated from "unsatisfactory" to "best," and the other three variables were rated from "low to highest." Trade-off was necessary if, for example, mission capability was the best but the risk (read: program disturbance) to the carrier high.

The progress of the B61-11 POG in determining which of the options was best is evident from several briefings given in the fall of 1995. In the first briefing, given on September 29, the four different design options are outlined and a notional plan for weapons and aircraft testing stretching through June 1997. Although the briefing includes values for cost, B-2 risk, and schedule/complexity, the mission capability is not rated. That happened in the second briefing, presented to Major General Joersz on October 23, which determined that two of the four design options had an "unsatisfactory" mission capability (see table).

B61-11 Design Option Variables


Option 1*

Option 2

Option 3 Option 4**
Mission capability Unsatisfactory Unsatisfactory Good Best
Cost Highest High Low Low
B-2 Risk Lowest Low Moderate High
Schedule/Complexity Highest High Moderate Low
* Baseline option.  ** Selected option.
Source: Briefing, SAF/AQQ, "B85 Replacement Program President to Maj Gen Joersz," October 23, 1995, slides 4-7. Partially declassified and released under FOIA. [Click to download]

The fact that unsatisfactory mission capability was an issue in the design work was known even before Congress approved the program. Shortly after approval was secured, DOE's B61-11 Program Manager at Oak Ridge, Richard Cawood, remarked in an interoffice memorandum from August 1995 that the initial design definition for the B61-11 case and associated hardware was "pretty soft and structurally adequate for only soft targets. Now that the program appears to be secure perhaps they'll get serious about the design," he remarked.

The October 23 briefing shows that "unsatisfactory" mission capability was still an issue for two of the design options three months later. Yet in a briefing presented by Cawood that same month, one of the design options appear to have been dropped leaving only three options for further consideration. The three remaining options were all based on converting the B61-7, similar to the preliminary cost estimate design, and involving modifying the "nose only."

Computer Simulation of B61-11 Impact

Sandia National Laboratories performed high-speed computer simulations to assess the stress on the B61-11 during impact in sand, soil, rock and permafrost. Two of the initial design options had "unsatisfactory" mission characteristics.

Following a conversation on October with B61-11 Program Manager at Sandia National Laboratories Don McCoy, Cawood noted that McCoy expected the "structural case requirements will firm up soon, perhaps by" October 13, 1995. "The design will be the more robust of the three under consideration," Cawood noted, "with a solid nose and with greater wall thickness."

Coinciding with the structural case requirements firming up, the DOD suddenly informed the NWCSSC on November 15 that delivery of the First Production Unit (FPU) B61-11 should be moved up and "delivered as soon as possible, with a goal of December 31, 1996." This was a considerable change that squeezed production by eight months. The accelerated schedule involved reprogramming $3.3 million from within the DOE's atomic energy defense weapons activities appropriations. Congress was informed but had no objections.

B61-11 Model Wind Tunnel Test

A weapons engineer at Sandia National Laboratories prepares a scaled-down model of a B61-11 for aerodynamic testing in a wind tunnel.

Moreover, DOD felt the design work had progressed sufficiently to be able to select the option. On November 21, 1995, only three months after the design work was officially begun, Herald P. Smith informed the Assistant Secretary for Defense Programs at DOE, Victor H. Reis, that "Option 2 (full steel case) be chosen as the leading candidate." Victor Reis replied on December 18, stating that DOE was "limiting our development to the full steel case option (Option 2)."

In his reply letter, Reis also noted that he expected Option 2 would be validated by "the safe separation analysis to be released later this month." This concerned calculations performed by Northrop, the producer of the B-2 bomber, to examine how B61-11 released and cleared the aircraft. By the time Reis told Smith about the validation, the calculations had already been successfully completed. Northrop told Sandia about them on December 7, after which Don McCoy at Sandia informed Cawood at DOE. McCoy said "this means Option 2 (the W61-like design) is the selected design, although it won't be official until" December 19, 1995.

The W61 Tiger II Missile

Building on Other Designs

The "W61-like design" chosen for the B61-11 made it possible to base part of the B61-11 production on components and tools developed for the W61 program. As mentioned above, the W61 was canceled in 1992 when the missile intended to carry it was canceled.

The B61-11 steel case "was essentially the same case, used for the W61 program." In fact, the B61-11 was so influenced by the W61 that W61 classification guidance was initially used until original classification authority was established for the B61-11.

The B61-11 consisted of "field retrofitting the B61-7 with a machines version of the W61 integral steel case, removing the parachute and installing ballast aft of the bomb, shortening the earth-penetrating nose, and installing a plastic...aeroshell covering to ensure identical standard B61-7 geometry."

Some weapon components were manufactured based on the design of W61 "blanks," but there was concern that "some of the W61 blanks will not yield an adequate product for the B61-11." This included the Penetrator Case and the Threaded Ring components.

In addition to W61, the production of the B61-11 also borrowed from another canceled nuclear program: the B90 nuclear strike/depth bomb. Some of the tools developed for the B90 program were useable with some modification for milling of internal features of the B61-11 case.

Production of the B61-11

The B61-11 program, or the B53 Replacement Program as it was formally called, was budgeted in 1995 to cost more almost $37.5 million, or $750.000 for each of the 50 B61-11s produced. As the first post-testing weapons production, the production program for the B61-11 program encountered many "firsts" that required new or significantly changed production methods.

Due to the very compressed production program, Product Realization Teams (PRT) were not created. It was also the first regular production weapons program to utilize a design process called WorkStream, a small-build program that operate with small inventories for duration of the program. A November 1995 overview of the Y-12 production commitment describes many of the considerations that went into the B61-11 program and how the producers anticipated to accomplish production.

The B61-7 conversion did not involve the Pantex facility. Instead, conversion kits were manufactured at the Nuclear Weapons Complex facilities, principally at the Kansas City Plant and at the Y-12 plant in Oak Ridge. These conversion kits, which included both the physics packages and the Canned Subassemblies (CSA), were then disassembled from the B61-7 "in the field" and reassembled into the earth-penetrator case by military personnel. Kit assembly took place between January and December 1996, according to a detailed DOE production plan. All B61-7s were taken from the active stockpile.

Flight Testing

The choice of design Option 2 presented a problem due to the number of flight tests required to certify the new design on the B-2. There was no time and money in the existing B-2 flight test program for the extensive testing required for a new weapon, so the B-52 was used to conduct drop tests to certify that the B61-11 was developed with identical properties and interfaces to the B61-7 which was already certified on the B-2 (Block 20). This would limit the number of flight tests required on the B-2. Moreover, to compensate for addition flight testing costs to the B-2 program, the B-2 program would be reimbursed up to $500,000 from the B-52 flight test dollars.

B61-11 Drop Test

A B61-11 drop test over the Utah Test and Training Range (UTTR) shows use of rockets to control spin.

Initially, weapons testing was scheduled for the period between November 1995 and December 1996, followed by a four-month aircraft testing period in March-June 1997. But due to the decision in late 1995 to accelerate completion of the First Production Unit (FPU) from August 1997 to December 1996, the initial testing program was cut short. A total of 13 full-scale drop tests were performed in 1996, three in Alaska and 10 at the Tonopah Test Range in Nevada. The B61-11 passed its certification flight tests on November 20, 1996, in time for completion of the FDU.

The frozen soil proof test in Alaska in 1996 was cancelled due to an aircraft system failure on the B-2. The test was rescheduled for march 1998, when two B61-11s were successfully dropped by a B-2 bomber. Altogether, a total of 25 drop tests were conducted from the B-2, B-52, B-1, and F-16. The drops tested the B61-11 earth-penetration capability into sand, hardpan, compact soil, rock, concrete and permafrost, indicating a wide geographic range for potential targets.


Four complete retrofit kits were delivered to the Air Force in mid-December 1996 and by the end of 1996, the B61-11 was accepted as a "limited stockpile item" pending additional tests. The B61-11 officially entered operational service with the 509th Wing at Whiteman Air Force Base in Missouri in November 1997.

The introduction into the stockpile coincided with the B-2 achieving nuclear Initial Operational Capability (IOC) and replacing the B-1 in the SIOP-98 warplan. Air Combat Command (ACC) informed the Defense Science Board Task Force on Nuclear Deterrence that "integration of the B61/11 [sic] has introduced a vastly new means of holding an enemy's buried, hardened and underground high-value targets at risk." Approximately 50 B61-11s were produced.

B61-11 at Whiteman Air Force Base, Missouri

A B61-11 shape on a loader inside a B-2 hangar at Whiteman Air Force Base in Missouri. The B61-11 entered service at Whiteman in November 1997, coinciding with the B-2 replacing the B-1 in the SIOP.
                                                                        Courtesy nukephoto.com

Although the B61-11 entered service with the 509th Wing in November 1997, full certification of the weapons took much longer. STRATCOM was concerned about mission effectiveness and asked Sandia National Laboratories to provide operational analysis and planning tools for the B61-11. This effort included evaluating "fratricide concerns, optimizing delivery with the B-2, and working to maximize both aircraft survivability and weapon effectiveness." Not until 2001 was the B61-11 certified as a "standard stockpile item" meeting all requirements.

Libya: The First B61-11 Target

Five months after Harold Smith called for an acceleration of the B61-11 production schedule, he went public with an assertion that the Air Force would use the B61-11 against Libya's alleged underground chemical weapons plant at Tarhunah if the President decided that the plant had to be destroyed. "We could not take [Tarhunah] out of commission using strictly conventional weapons," Smith told the Associated Press. The B61-11 "would be the nuclear weapon of choice," he told Jane's Defence Weekly.

Smith gave the statement during a breakfast interview with reporters after Defense Secretary William Perry had earlier told a Senate Foreign Relations Committee hearing on chemical or biological weapons that the U.S. retained the option of using nuclear weapons against countries armed with chemical and biological weapons.

The Pentagon quickly retreated from the nuclear sable rattling. "There is no consideration to using nuclear weapons [against Tarhunah], and any implication that we would use nuclear weapons preemptively against this plant is just wrong," said Pentagon spokesperson Ken Bacon.  In the same breath, however, Bacon said that Washington would not rule out using nuclear weapons.

B61-11 Versus B53

The B61-11 program was formally called a B53 replacement program, and government officials have consistently portrayed the B61-11 as merely a "replacement" for the B53. In doing so, the government has insisted that the B61-11 has "no new mission" but simply had to "fulfill the B53 mission." But it is difficult to find any similarities between the B61-11 and B53. Indeed, a comparison of the two weapons illustrate just how different they are and why the operational characteristics of the B61-11 are so different compared with the B53:

B61-11 and B53 Comparison

Characteristics B61-11 B53
Yield 400 Kilotons 9,000 Kilotons
Dimensions 12 ft x 13.4 in 12 ft 4 in x 50 in
Weight ~1,200 lbs 8,900 lbs
Delivery platform B-2A (primary); also tested on B-1B, B-52H,
and F-16
Delivery mode Free fall, airburst, contact, laydown, retarded, time delay, earth-penetration. Free fall, airburst, contact burst, only laydown delivery. Timer armed and fired.
Probability of arrival High (B-2A) Low to moderate

Originally built between 1962 and 1965, the B53s used to be carried by B-52 bombers on continuous airborne alert missions between 1961 and 1968. Retirement of the remaining B53s was underway in 1987 when the Reagan administration suddenly announced it was curtailing retirement and bringing retired (and still assembled) bombs back into the active stockpile. The huge B53 apparently was needed to destroy a few high-value Soviet underground facilities.

Addition June 17, 2005: Click here for new FOIA information about 1987 decision to retain the B53.

The B53 was highlighted as an unsafe weapon in the 1990 Drell Report, which contributed to the decision to replace the weapon. The B53 did not have Command Disable (CD), PAL (Permissive Action Link), or Insensitive High Explosives. Yet these features are also lacking in warheads that are retained (W76 and W88), weapons that have not been retired or replaced. Indeed, all remaining B53s in the stockpile in 1993 were found to be "inherently one-point safe." But the bomb did not have Enhanced Nuclear Detonation Safety (ENDS), intended to prevent accidental firing, and was found to have "no assured level of nuclear safety in a broad range of multiple abnormal environments." Dismantlement operations at Pantex were authorized to begin in July 1994.

"Replacement" Improves Mission Flexibility

The considerable difference is size between the enormous B53 (right) and the B61-11 illustrates the operational gains from "replacing" the old "earth-digger" with the new "earth-penetrator." Whereas the B53 could only be carried on the veteran B-52, the B61-11 is assigned to the B-2 stealth bomber and has been test dropped from B-1B and F-16 aircraft as well.

Safety was not the only reason for replacing the B53. An Air Force briefing from December 1994 indicates that nuclear guidance issued by the Chairman of the Joint Chiefs of Staff had been changed and that the B-52 was no longer considered capable enough to penetrate hostile air defenses on a nuclear bunker-buster mission with the B53. The Air Force briefing states that "a more survivable platform that a B-52 is needed" to "meet JSCP direction" and that the objective is to "increase PA [Probability of Arrival] over target." The nuclear annex (Annex C) to JSCP (Joint Strategic Capability Plan) 1993-1995 was updated three times between July 1993 and the time of the Air Force briefing (December 1994).

Warhead Yield And Mission Adequacy

Many of the statements given by DOE and DOD on the B61-11 program claim that no changes were made to the B61-7 warhead. "This modification involves no change to the nuclear package of the B61-7," DOE stated on September 20, 1995. Vice President for National Security Programs at Sandia National Laboratories, Roger Hagengruber, echoed in a television interview in 1997: "The physics package itself is identical."

If "no change" and "identical" mean that the yield of the B61-11 is the same as the B61-7, then these statements are false. The B61-7 has several selective yields (possibly four) up to 360 kilotons. As of March 1996, the B61-11 was also expected to have this capability, but at some point before March 2000 the yield was changed to 400 kilotons (a 10 percent increase). The selective yield options were also canceled, making the B61-11 a single-yield weapon. This increase in yield may have been a result of the limited earth-penetrating capability of the B61-11.

The frozen soil proof drop tests conducted in Alaska in March 1998 suggests that the earth-penetration capability of the B61-11 is limited. During the test, two B61-11 shapes were dropped from a B-2 bomber at 8,000 feet. The two shapes hit the ground some 45 feet (15 meters) from each other. The Air Force said the B61-11 only proved capable of penetrating some 6-10 feet (2-3 meters) into the frozen soil. At best the weapon would penetrate 15-25 feet (5-8 meters). A photo taken of the retrieval of one of the bombs in Alaska suggests the penetration depth was around 18 feet (6 meters).

B61-11 Test Drop In Alaska

Two B61-11 shapes dropped by a B-2 bomber into the Stuart Creek Impact Area near Fairbanks, Alaska, on March 17, 1998. The weapons were retrieved, indicating penetration depth of roughly 18 feet (6 meters) into frozen soil (left) and with intact front casings but significant structural damage to the rear section (right).

Whether the drop tests prompted changes to the design is unknown, but DOE initiated two alterations to the B61-11 in 1998 (ALT 336) and 1999 (ALT 349. Moreover, in 2000 Sandia National Laboratories followed up with an inter-agency study of the penetration capability of the B61-11. One year later, in December 2001, the Bush administration's Nuclear Posture Review informed Congress that the capability of the B61-11 was inadequate and incapable of holding at risk some deep and hardened targets:

The B61-11 "cannot survive penetration into many types of terrain in which hardened underground facilities are located. Given these limitations, the targeting of a number of hardened, underground facilities is limited to an attack against surface features, which does not does not provide a high probability of defeat of these important targets."

On the one hand this suggests that conversion of the B61-7 into an earth-penetrator left significant issues unresolved that the planners have been trying to resolve after the B61-11 was rushed into the stockpile in 1997. On the other hand, it suggests that the mission of the weapon has evolved since the initial design was approved. Since the Air Force determined in October 1995 that the B61-11 did "satisfy USSTRATCOM requirements," the NPR's determination that that no longer is the case suggests that STRATCOM has changed its requirements for the mission.

After ten years and tens of millions of dollars spent on developing the B61-11, the Bush administration is now trying to persuade Congress that the solution to the unsatisfactory mission capability of the B61-11 is to build yet another modified bomb: the Robust Nuclear Earth Penetrator (RNEP). The RNEP will be built around a modified B83 very-high yield bomb, the weapon that the B61-11 program rejected in favor of the more "mature" B61-7.

RNEP: The Follow-On To B61-11

The Bush administration plans to spend $26 million on developing the Robust Nuclear Earth Penetrator the next two years. Since this slide was produced, a decision has been made to use the B83 bomb. Compared with the 400 kiloton B61-11, the B83 has selective yields up to 1.2 megatons.

At the same time the Bush administration is asking Congress to provide $26 million for RNEP in 2006-2007, new alterations continue to be added to the B61-11: ALT 350 for completion in September 2005 and ALT 357 (refurbishment of secondaries) from October 2005 with completion in September 2008.

Hans M. Kristensen/Federation of American Scientists | www.nukestrat.com | 2004-2006

Message, ACC/LG Director of Logistics, to MGen D. Haines, ACC/LG, et al., "INFO: DSB Task Force on Nuclear Deterrence," December 8, 1997, w/attch.
[0.37 MB]
Partially declassified and released under FOIA.

Interoffice Memorandum, Nolan E. Moore, DOE, to Richard Cawood, et al., March 6, 1996. [0.09 MB]
Released under FOIA.

Letter, Thomas P. Seitz, DOE/ADASMASS, to Harold P. Smith, Jr., [no subject], December 18, 1995. [0.05 MB]
Released under FOIA.

Interoffice Memorandum, Department of Energy, Richard C. Cawood to Bowersgl, et al., "B61-11 Design Release Status," December 7, 1995. [0.04 MB]
Released under FOIA.

Internal Memorandum, R. C. Cawood, DOE, to F. P. Gustavson, "Y-12 Commitment to the B61-11 Program," November 27, 1995. [0.53 MB]
Released under FOIA.

Letter, Harold P. Smith, Jr., Assistant to the Secretary of Defense (Atomic Energy), to Victor H. Reis, Assistant Secretary for Defense Programs, Department of Energy, [Revised B53 Replacement Program], November 21, 1995. [0.69 MB]
Partially declassified and released under FOIA.

Memorandum, Thomas P. Seitz, DOE/ADASMASS, to Rodger Hagengrubar, et al., "B61-11, First Production Unit (FPU)," November 17, 1995. [0.06 MB]
Released under FOIA.

Briefing, SAF/AQQ, "B53 Replacement Program Presented to Maj Gen Joersz," October 23, 1995. [0.56 MB]
Partially declassified and released under FOIA.

Briefing, Dick [Richard] Cawood, DOE, "B61-11 Program Briefing," October 1995.
[0.07 MB]
Released under FOIA.

Interoffice Memorandum, Richard E. Cawood, DOE, to Bowersgl, et al., "B61-11 Design/Production Issues," October 4, 1995. [0.08 MB]
Released under FOIA.

Briefing, BGen James Richards, SAF/AQQ "B53 Replacement Program," September 29, 1995. [0.21 MB]
Partially declassified and released under FOIA.

Major Selva for Lt. Col. Billy M. Mullins, USAF, SAF/AQQS(N), "Background paper on why the B61-11 is being developed," September 22, 1995. Secret/FRD. [0.13 MB]
Partially declassified and released under FOIA.

Press Release, Department of Energy, "A Modification of the B61 is Expected to Replace the B53," September 20, 1995. [0.14 MB]

Lt. Col. Billy M. Mullins, USAF, SAF/AQQS(N), "Talking Papers on the B61-11 Program Status and History," September 11, 1995. Secret. [0.19 MB]
Partially declassified and released under FOIA.

Briefing, DOE/DASMASS Weapons Panel, "B53 Replacement Project," n.d. [August 1995]. [1.4 MB]
Partially declassified and released under FOIA.

Memorandum for the Record, USAF, "B61-11 Program Update to AQQ and PEO/ST," n.d. [probably August 28, 1995].
[0.07 MB]
Partially declassified and released under FOIA.

Briefing, SAF/AQQS, "B61-11 Program Update," August 28, 1995. [0.25 MB]
Partially declassified and released under FOIA.

Memorandum for distribution, Craig L. Loisel, AFMC/SA-SLC/NWIE, "B53 Replacement Kickoff Meeting," August 27 [probably July 27], 1995.
[0.33 MB]
Released under FOIA.

Letter, Victor H. Reis, DOE, to Harold P. Smith, Chairman NWCSSC, [no title], August 15, 1995. [0.21 MB]
Partially declassified and released under FOIA.

Message, Armen E. Mardiguian, SAF/AQQS, to Robert L. Ostrander, et al., "B61-11 Meeting," August 9, 1995. [0.05 MB]
Partially declassified and released under FOIA.

Interoffice Memorandum,  Richard C. Cawood, DOE, to Areharttajr, et al., "B61-11 Authorization," August 2, 1995, 11:17 am EDT. [0.05 MB]
Released under FOIA.

Memorandum, Harold P. Smith, Jr., to Assist Secretary for Defense Programs, DOE, "Replacement of the B53 Strategic Gravity Bomb," July 18, 1995, w/attch. [0.34 MB]
Partially declassified and released under FOIA.

Department of Energy, "B53 Replacement Program Budget Profile," April 27, 1995.
[0.05 MB]
Released under FOIA.

Letter, Joseph F. Vivona, DOE Chief Financial Officer, to Senator Strom Thurmond, [no subject], April 18, 1995.
[0.16 MB]
Partially declassified and released under FOIA.

Message, Michael Fulca, DOE/DP-10, to Charles Beers, et al., "Civiak bomb brief," April 7, 1995, 3:57 PM. [0.07 MB]
Partially declassified and released under FOIA.

Briefing, Everet Beckner, DOE, PDAS(DP), "DoD/DOE B53 Replacement Program: Presentation to Professional Staff Members," n.d. [April 1995. [0.23 MB]
Partially declassified and released under FOIA.

Memorandum, Ward Sigmond, Assistant Staff Director, NWC, to Members, NWC/NWCSSC, "Replacement of the B53 Strategic Gravity Bomb," Information Item NWC 95-04, February 3, 1995, w/attch.
[0.29 MB]
Partially declassified and released under FOIA.

Memorandum, Maj Rex R. Kiziah, USAF, OASD/AE, to B53 replacement working meeting attendees, "Summery of B53 Working Meeting of December 6, 1994," December 9, 1994.
[0.76 MB]
Partially declassified and released under FOIA.

Memorandum (w/attachment), J. David Finley, Department of Energy, Albuquerque Operations Office, "Nuclear Explosive Safety Study Report," August 23, 1994. [1.88 MB]
Partially declassified and released under the FOIA.

Letter, DOE, Winford Ellis, Rear Admiral, U.S. Navy, Deputy Assistant Secretary for Military Application Defense Programs, to Harold Smith, Assistant to the Secretary of Defense (Atomic Energy), July 16, 1993.
[0.07 MB]
Partially declassified and released under FOIA.

N. R. Hansen, "Nuclear Safety Themes for Earth Penetrating Weapons," Sandia National Laboratories, April 1, 1993.
[1.2 MB]
Released under FOIA.

Other background information:

Christopher E. Paine, et al., "Countering Proliferation Or Compounding It?," Natural Resources Defense Council, May 2003.

Robert W. Nelson, "Low Yield Earth Penetrating Nuclear Weapons," FAS Public Interest Report, January/February 2001, pp. 1-5.

Hans M. Kristensen, "Proliferation of Weapons of Mass Destruction and U.S. Nuclear Strategy," BASIC, April 1998.

Greg Mello, "New Bomb, No Mission," Bulletin of the Atomic Scientists, May/June 1997, pp. 28-32.

William M. Arkin, "New, and stupid," Bulletin of the Atomic Scientists, January/February 1996, p. 64.
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  Hans M. Kristensen