On 19 April 1989, an explosion occurred within the Number Two 16-inch gun turret of the United States Navy battleship USS Iowa (BB-61) during a fleet exercise in the Caribbean Sea near Puerto Rico.

Bulkeley personally recommended to the Chief of Naval Operations (CNO), Admiral James Watkins, and the Secretary of the Navy, John Lehman, that Iowa be taken out of service immediately.

[10] In August 1988, Iowa set sail on sea trials around the Chesapeake Bay area and then began refresher training in the waters around Florida and Puerto Rico in October.

[12] In January 1989 Iowa's master chief fire controlman, Stephen Skelley, and gunnery officer, Lieutenant Commander Kenneth Michael Costigan, persuaded Moosally to allow them to experiment with increasing the range of the main guns using "supercharged" powder bags and specially designed shells.

Although the shells had been fired without serious incident, Meyer and Petty Officer First Class Dale Eugene Mortensen, gun chief for Turret One, told Skelley that they would no longer participate in his experiments.

[8][15] A week after the long-range shoot at Vieques, Iowa's new executive officer, Commander John Morse, directed a main battery drill, over the objections of his gun crews, in which turrets One and Two fired while both were pointed 15° off the starboard side of the ship's bow.

An explosive ordnance disposal technician, Operations Specialist First Class James Bennett Drake from the nearby USS Coral Sea, was sent to Iowa to assist in unloading the powder in Turret Two's left and right guns.

Unsure whether she could trust Truitt, Kathy Kubicina, Hartwig's sister, mailed letters on 4 May to Moosally, Morse, Costigan, Iowa's Chaplain Lieutenant Commander James Danner, and to Ohio Senators Howard Metzenbaum and John Glenn in which she described the life insurance policy.

An informal investigation meant that testimony was not required to be taken under oath, witnesses were not advised of their rights, defense attorneys were not present, and no one, including the deceased, could be charged with a crime no matter what the evidence revealed.

Admiral Leon A. Edney, the U.S. Navy's Vice Chief of Naval Operations, however, told Gordon that formal NIS participation in the investigation under Milligan's supervision was fine.

[65] Beginning in May, reports on the NIS investigation began to appear in news media, including The Virginian-Pilot, Newsday, The Washington Post, The New York Times, and the Daily Press, most of which mentioned Hartwig or Truitt by name.

[71] On 28 August, technicians at the Naval Weapons Support Center at Crane, Indiana confirmed the FBI's conclusion that an electronic timer, batteries, and/or a primer were not involved in the explosion.

[75] Donnell, on 28 July, endorsed Milligan's report, saying that the determination that Hartwig had sabotaged the gun "leaves the reader incredulous, yet the opinion is supported by facts and analysis from which it flows logically and inevitably".

[77] Although Miceli had just announced that test results at Dahlgren showed that an electronic timer had not caused the explosion, Trost endorsed the report on 31 August, stating that Hartwig was "the individual who had motive, knowledge, and physical position within the turret gun room to place a device in the powder train".

Also, Congresswoman Mary Rose Oakar asked Nicholas Mavroules, chairman of the Investigations Subcommittee of the House Armed Services Committee, to look into the Navy's findings and schedule hearings.

During the hearing, Sam Nunn announced that Sandia National Laboratories in Albuquerque, New Mexico, had agreed to a request by the GAO to assist with the Navy's technical investigation to see if there might be a natural explanation for the explosion.

The committee, including Mavroules, Les Aspin, Larry Hopkins, Norman Sisisky, and Joseph Brennan, interviewed Donnell, Ault, Hazelwood, Milligan, Miceli, Truitt, Nimmich, and Richard Froede, the Armed Services Medical Examiner.

Navy technicians stated that the discovery under the center gun's projectile's rotating band of minute steel-wool fibers that were encrusted with calcium and chlorine, a fragment of polyethylene terephthalate (commonly used in plastic bags), and different glycols, including brake fluid, hypochlorite, antifreeze, and Brylcreem together indicated the use of a chemical igniter.

Borders concluded that ordinary sources accounted for all of the "foreign materials" found by the Navy on the center gun projectile, and that the theory that a chemical igniter had been used to cause the explosion was extremely doubtful.

After spending 50 hours exploring the ramifications on a Cray supercomputer, Schuler concluded that this overram, combined with the 2,800 pounds-force per square inch (19 MPa) of pressure produced by the rammer, likely compressed the powder bags to the point that they had ignited.

[96] Concerned that Miceli's refusal to conduct full-scale drop tests was placing Navy gun crews at risk, on 11 May Schwoebel contacted Rick DeBobes, Nunn's counsel for the SASC.

The tests consisted of vertically stacking five D-846 powder bags under an 860-pound (390 kg) weight and dropping them 3 feet (0.9 m) onto a steel plate to simulate a high-speed overram in a 16-inch gun barrel.

[98] The next day Schwoebel, Schuler, Cooper, and Borders publicly briefed the SASC in the Hart Senate Office Building on the results of their investigation, stating that, in Sandia's opinion, the explosion had occurred because of an overram of the powder caused by either an accident due to human error or an equipment failure.

The Sandia team members also noted that Miceli refused to allow his civilian technicians to test alternate overram scenarios and appeared, by various means, to deliberately delay the progress of the investigation.

Tom Doran, a civilian member of Miceli's team, told Schwoebel on 18 July that his tests had shown that overram explosions could occur much more easily and at slower speeds depending on the configuration of loose pellets in the powder bags.

Sandia theorized that the overram may have occurred due to inadequate training of some members of the center gun crew; a poorly conceived, briefed, and executed firing plan that contributed to confusion; and—possibly—a malfunction of the rammer.

And indeed, despite the Sandia theory and almost two years of subsequent testing, a substantial body of scientific and expert evidence continue to support the initial investigation finding that no plausible accidental cause can be established."

[112] As part of the National Defense Reserve Fleet, Iowa was berthed at the Naval Education and Training Center in Newport from 24 September 1998 to 8 March 2001, when she began her journey under tow to California.

The Hartwig family filed objections, but on 10 November 1999 District Judge Solomon Oliver, Jr. adopted the recommendation to dismiss, ruling that "however hurtful the government's action may have been, they cannot form the basis of a claim against the United States.

[132] In March 2001 Captains Moosally, Miceli, Morse, and CDR Finney filed suit against Glimpse of Hell author Thompson, his publisher, W.W. Norton, and Dan Meyer, who the plaintiffs stated provided much of the information used in the book, for libel, false light privacy, and conspiracy.