Morton Thiokol’s responsibility for the Challenger disaster

Morton Thiokol’s responsibility for the Challenger disaster emerged in two sharply separated stages: the stock market identified the company almost immediately, while the public explanation came six months later through an official investigation. The contrast is central to the episode’s significance. Investors’ rapid judgment proved correct, yet neither the available public reports nor the researchers who examined trading could establish how the market had reached it.

The market’s immediate signal

At 11:38 a.m. on January 28, 1986, Challenger lifted off from Cape Canaveral; seventy-four seconds later, the shuttle exploded. The launch had been televised, and news spread quickly. Within minutes investors began selling the stocks of the four major contractors involved in the launch: Rockwell International, which built the shuttle and its main engines; Lockheed, which managed ground support; Martin Marietta, which manufactured the external fuel tank; and Morton Thiokol, which built the solid-fuel booster rocket.

The first price movements distinguished Thiokol from the other contractors. Twenty-one minutes after the explosion, Lockheed was down 5 percent, Martin Marietta 3 percent, and Rockwell 6 percent. Thiokol’s shares drew such heavy selling and so little buying that trading was halted almost immediately. When trading resumed nearly an hour after the explosion, the stock was down 6 percent. By the close of the day, its loss had nearly doubled to almost 12 percent, while the other three firms’ shares had recovered part of their initial declines and ended down only around 3 percent.

This divergence amounted to an unusually clear market judgment. A stock price reflects expectations about a company’s future earnings; Thiokol’s much steeper fall than its competitors’ therefore signaled that investors associated the company with responsibility for the disaster and anticipated severe consequences for its business. The signal arrived before a public explanation did.

The evidence available that day

The timing makes the market’s judgment remarkable. On the day of the explosion, no public comment singled out Thiokol as the guilty company. The next morning, The New York Times mentioned two circulating rumors, but neither implicated Thiokol; the paper concluded, “There are no clues to the cause of the accident.” Investors’ differentiation among the contractors thus preceded the public account that would later confirm the company’s responsibility.

The researchers who studied the market’s reaction, finance professors Michael T. Maloney and J. Harold Mulherin, investigated whether informed insiders could explain the initial fall. They examined insider-trading records for Thiokol executives who might have known that their company was responsible, but found no evidence that those executives dumped stock on January 28. Nor did they find evidence that executives at the competing contractors, who might have learned about the O-rings and sold Thiokol short, made the corresponding trades. There was no sign of someone with inside information selling Thiokol while buying shares in the other three companies.

Instead, the first-day decline resulted from the behavior of investors who were mostly relatively uninformed and who simply would not buy Thiokol stock. Maloney and Mulherin could not give a convincing account of why buyers withdrew. In the end, they assumed insider information was responsible, but remained unable to explain how that information had produced the price movement. Their unresolved question preserves the difference between observing a correct collective signal and knowing the mechanism that generated it.

The later technical explanation

Six months after the explosion, the Presidential Commission on the Challenger disclosed the failure that had connected Thiokol’s equipment to the disaster. The booster rockets made by the company used O-ring seals intended to prevent hot exhaust gases from escaping. In cold weather, the seals became less resilient; gaps formed, allowing gases to leak out. In Challenger’s case, the escaping gases burned into the shuttle’s main fuel tank and caused the explosion. Thiokol was held liable, while the other three contractors were exonerated.

The physical property of the seals could be demonstrated directly. At a congressional hearing, physicist Richard Feynman placed an O-ring in a glass of ice water; after it had cooled, it had become brittle. The demonstration made tangible the crucial relation between low temperature and the seals’ failure, and helped explain why a component designed to contain hot gases had not done so in this case.

What the episode establishes—and leaves open

The market had marked Thiokol out within roughly half an hour of Challenger’s destruction, and the later investigation confirmed that the company’s booster seals were responsible. The episode is presented as evidence that investors can sometimes combine dispersed judgments into a useful collective estimate before a public explanation is available. In this instance, the stock market acted as a weighing mechanism: buyers and sellers responded to what they believed had happened, and their price signal pointed to the company later held liable.

The account nevertheless treats the result cautiously. It was a single event, so Thiokol’s sharp decline might have been luck. Its business could also have seemed especially vulnerable to a downturn in the space program, or the trading halt itself might have warned investors away. The episode therefore does not show exactly how the market knew, or prove that markets will reliably make such judgments. Its force lies in the unresolved contrast: the public record initially offered no clue, the researchers could not identify a convincing information channel, and yet the market’s first-day distinction between Thiokol and its competitors proved accurate.