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Nuclear Brief April 3, 2006

Divine Strake: Global Strike Low-Yield Nuclear Simulation


DTRA announces cancellation of Diving Strake.

4/7/06: After DTRA told Washington Post that Divine Strake is not a nuclear simulation after all, we're waiting for an official explanation from DTRA why it told FAS (and Congress) that it is nuclear. More to come...
The conventional Divine Strake test scheduled for June 2006 is expected to create a large mushroom cloud, an image associated with atmospheric nuclear tests in the 1950s and early 1960s. This image shows the Misers Gold test at White Sands in 1989, a surface blast equivalent of 5 kt TNT. Divine Strake will be nearly 0.6 kt TNT.
                              Source: LANL

The Department of Energy is readying the Nevada Test Site for a large-scale, open-air, high explosive detonation on a tunnel complex. The Defense Threat Reduction Agency (DTRA), the DOE customer which is conducting the test, is stressing that the test is not a nuclear blast and the Russian government reportedly has been notified to avoid misunderstanding about the event. "The test is aimed at determining how well a massive conventional bomb would perform against fortified underground targets," the Washington Post reported on March 31st.

No one - with the notable exception of Andrew Lichterman and John Fleck who first reported on this - seems to have tried to dig deeper than the press release from DTRA. I too have monitored the preparations for Divine Strake; It is much more than was reported (for media reports about Divine Strake after publication of this Nuclear Brief, click here).

Divine Strake is neither a bomb nor conventional. Instead, the test is a detonation of a pile of chemical explosives to simulate a "low-yield nuclear weapon ground shock" effect to "improve the warfighter’s confidence in selecting the smallest proper nuclear yield necessary to destroy underground facilities while minimizing collateral damage."

Divine Strake, moreover, is an integral part of STRATCOM's new Global Strike mission, which is otherwise said to provide mainly non-nuclear means of defeating time-critical targets. Divine Strake is the first nuclear effects simulation of this kind against underground targets since President George W. Bush in Summer 2004 directed STRATCOM to "extend Global Strike to counter all HDBTs [Hard and Deeply Buried Targets] to include both tactical and strategic adversarial targets." (see guidance overview here)

Update April 4, 2006:

Here is DTRA's confirmation:

"Yes, the event described is Divine Strake. Better predictive tools will reduce the uncertainties involved with defeating very hard targets, and therefore reduce the need for higher yield weapons to overcome those uncertainties. There are no nuclear tests planned or desired."

DTRA Public Affairs, email to Hans Kristensen, 4/3/2006 6:06 PM

The Divine Strake Event

Divine Strake was approved in 2002 as part of the congressionally authorized DOD FY2002 Tunnel Target Defeat Advanced Concept and Technology Demonstration (ACTD). Since then, DTRA has prepared for the event under its Counterforce program. DTRA confirmed today that Divine Strake is the event described in the budget documents. The DTRA counterforce RDT&E (Research, Development, Testing and Engineering) budget for FY2006 described the experiment this way:

"Conduct the Tunnel Target Defeat Advanced Concept and Technology Demonstration(s) (ACTD) Full-Scale tunnel defeat demonstration using high explosives to simulate a low yield nuclear weapon ground shock environment at Department of Energy's Nevada Test Site."

The Divine Strake event involves placing high explosives on the surface similarly to the Misers Gold experiment in 1989.
                              Source: DTRA

The reference to low-yield nuclear weapons was omitted from the section in the FY2007 budget request, which instead describes the event like this: "Conduct the Tunnel Target Defeat ACTD large-scale tunnel defeat demonstration using high explosives to produce the desired ground shock environment at the Department of Energy's Nevada Test Site." Yet the nuclear reference is used elsewhere in the FY2007 budget:

"The Tunnel Target Defeat ACTD will develop a planning tool that will improve the warfighter’s confidence in selecting the smallest proper nuclear yield necessary to destroy underground facilities while minimizing collateral damage."

Divine Strake reflects a concern in the Pentagon over what is said to be an increasing number of a underground facilities in potentially hostile countries. The 2001 Nuclear Posture Review warned that the existing B61-11 nuclear earth-penetrator does not have sufficient capability against certain deeply buried targets. The Robust Nuclear Earth Penetrator was supposed to provide additional capability, but Congress has refused to fund the weapon due to concern that it could lower the nuclear threshold.

The U16B tunnel shown in a 3D simulation of a 10 kt nuclear agent defeat experiment  conducted by Los Alamos in 2004. 
                              Source: LANL

Divine Stake is not an RNEP-type experiment because it simulates the use of a very low-yield nuclear weapon against an relatively shallow underground target. Divine Strake follows a previous 3D computer simulation conducted by scientists at Los Alamos National Laboratory in 2004, which examined the use of a 10 kt nuclear detonation inside the U16B tunnel as an agent defeat weapon. The experiment concluded that the relatively large yield was necessary for radiation to penetrate through the entire length of the tunnel "indicating that such yields might be necessary to guarantee agent destruction stored inside large tunnel complexes."

Divine Strake, in contrast, does not simulate agent defeat destruction but simply envisions using the explosive yield of a small nuclear weapon to destroy or severely damage and underground structure. Also important is that the simulation is not directed against the tunnel entrances, but involves detonating the explosives on top of the surface above the tunnel.

The Divine Strake explosion is half as powerful as the lowest yield option of the B61 nuclear gravity bomb. 
                                Source: SNL

The contract for collecting the seismo-acoustic data from Divine Strake was awarded to Southern Methodist University on March 16, 2006.

The "Weapon"

Contrary to most of the media reports, Divine Strake is not testing a conventional bomb but simply detonates a huge pile (700 tons) of Ammonium Nitrate and Fuel Oil (ANFO). For comparison, the largest conventional weapon in the U.S. inventory is the MOAB (Massive Ordnance Air Blast) bomb, which contains nearly nine tons of explosives with a yield of approximately 0.012 kt TNT.

The explosive power of Divine Strake will be approximately 593 tons of TNT equivalent, or roughly 0.6 kt. This is about double the lowest yield option on the non-strategic B61 nuclear gravity bomb, and suggests that Divine Strake may be intended to fine-tune use of the B61 bomb. There are three modifications of the non-strategic B61 bomb in the U.S. stockpile with yields ranging from 0.3 kt to 170 kt.

B61 Tactical Nuclear Bomb Characteristics

Weapon Yield Years Build

Total U.S. Stockpile

      Active Inactive Total
B61-3 0.3, 1.5, 60, or 170 kilotons 1979-1989 200 196 396
B61-4 0.3, 1.5, 10, or 45 kilotons 1979-1989 200 212 412
B61-10* 0.3, 5, 10, or 80 kilotons 1990-1991 0 208 208
 Total     400 610 1,010
* The B61-10 is a converted Pershing II missile W85 warhead.

The B61 also exists in a strategic version (B61-7) with four yields up to 350 kt, but given the strategic mission of this weapon the lowest yield option may be higher than the non-strategic version. Finally, the B61-11 has a single yield of 400 kt.

Divine Strake is not the first large-scale, open-air, high explosive detonation conducted by DTRA. Such events apparently play an important role in fine-tuning the plans for using nuclear weapons against underground and surface targets. Since 1977, at least 10 similar events have been carried out at the White Sands Missile Range in New Mexico. The events have involved from 24 tons to as much as 4,744 tons of high explosives.

The Minor Scale event in 1985 (left) detonated 4,744 tons of high explosives on the ground, the largest such event ever conducted. The experiment simulated the use of a 4 kt nuclear weapon. The 609 tons Direct Course event in 1983 (right) simulated the effect of a tactical nuclear weapon exploding above the ground.
                                                                                 Source: DTRA

Other detonations have included an underground detonation of 1,410 tons in the U12n tunnel at NTS in 1993. In addition, Seven 120-ton detonations were carried out at Misers Bluff at Planet Ranch in Arizona in 1978. Finally, in 2002, an 18 tons explosion was set off at the Nevada Test Site.

Experience obtained from these detonations were used to develop the plans for Divine Strake scheduled for June 2, 2006, at the U16B tunnel complex at the Nevada Test Site.

The U16B Tunnel Complex

Divine Strake will be conducted at the U16B complex on the Nevada Test Site. U16B consists of a hook-shaped tunnel drilled through a limestone formation and connected to three portals and a vent hole. Each of the tunnel entrances are sealed by large steel doors 14x13 feet and 1.5 foot thick.

The Divine Strake detonation will be conducted at the U16B Tunnel Complex approximately 83 miles northwest of Las Vegas, only eight miles west of the Yucca Flat where hundreds of nuclear tests were conducted between the 1950s and 1992. The precise coordinates of the site are 37° 1'20.51"N, 116°10'54.30"W.
                                                                                                          Source: DOE

The target

The U16B target was "carefully chosen" for Divine Strake so that it "simulates the characteristics of important potential, global adversaries," according to the DOE. The detonation will be conducted in a limestone bed with specific geological properties, according to the DOE's draft environmental assessment for Divine Strake: "As a number of potential adversarial military targets are based in similar limestones, [Divine Strake] needed to be sited in a similar geological setting to actual military targets."

According to the DOE, such HDBTs are used by adversaries for command and control, storage of munitions (including weapons of mass destruction, and long-range missiles), modern air defenses, a variety of tactical weapons, wartime refuge for national leaders, and a multitude of other offensive and defensive military uses.

An example of such a target may be the Chinese airbase at Feidong, which includes what appears to be a large underground facility for hiding aircraft and potentially also other of the capabilities mentioned by DOE.

The tunnel at the Chinese airbase at Feidong is one of many military facilities that may be a potential target for the nuclear capabilities developed by Divine Strake.
                                                                              Source: DigitalGlobe/ImagingNotes


© Hans M. Kristensen/Federation of American Scientists | www.nukestrat.com | 2004-2007

download documents:

» Defense Threat Reduction Agency, "DIVINE STRAKE Experiment," n.d. (August 1, 2006).

» Defense Threat Reduction Agency, FY2007 Budget Request, RDT&E, Exhibit R-1, Line Item No. 26, February 2006, pp. 16, 22 (excerpts only). [0.06 MB]

» Defense Threat Reduction Agency, FY2006 Budget Request, RDT&E, Exhibit R-1, Shopping List - Item No. 28-26 of 28-27, February 2005 (excerpts only). [0.04 MB]

» U.S. Department of Energy, "Large-Scale, Open-Air Explosive Detonation DIVINE STRAKE at the Nevada Test Site," Revised Environmental Assessment, DOE/EA-1550, Pre-Approval Draft, November 2005. [12.1 MB]

» U.S. Department of Energy, "Large-Scale, Open-Air Explosive Detonation DIVINE STRAKE at the Nevada Test Site," Environmental Assessment, DOE/EA-1550, May 2006. [14 MB]

background information:

» Hans M. Kristensen, Global Strike," Federation of American Scientists, March 15, 2006.

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  © Hans M. Kristensen