A Norwegian metallurgist claims to have solved the puzzle of why the US Twin Towers collapsed – because molten aluminium from the aircraft that hit the World Trade Centre reacted with water in the buildings, causing massive explosions. The aluminium industry has recorded hundreds of such explosions, says Christian Simensen, senior scientist at SINTEF, an independent research organisation in Scandinavia. The official report missed the true cause, he adds.
Some conspiracy advocates point to powerful explosions heard before the buildings collapsed as evidence for demolition charges. Simensen has another explanation: when the plane struck the building, it slowed and dragged material around it; the steel in the building cut up the softer parts of the aircraft such as the fuel tank. ‘All that was put on fire due to very strong friction,’ Simensen explains: ‘In the middle you have an aircraft surrounded by insulation material, which is heated by burning aircraft fuel.’ There were 38 t of fuel and 30 t of aluminium in the jet, he notes.
The aircraft metal would have reached ca 660oC within half an hour to an hour, melting the aluminium. When temperatures got above 700oC, it became like water, says Simensen. He believes the melt reached a temperature of 800oC, and a stream of molten aluminium flowed down through the floor. When the metal met the automatic sprinkler device, the result was a series of violent explosions.
Hydrogen gas would also have been released at extreme pressure, blowing everything to pieces, Simensen says; rust was everywhere and would have facilitated the metal’s reaction with water. ‘The explosion took place beneath the floor that was burning. You can even see grayish liquid coming out the windows. That is aluminium alloy,’ he explains. Simensen notes that aluminium has incredibly high heat conductivity, allowing the metal from the aircraft to quickly become superheated.
Scientists from aluminium company Alcoa agreed it was an aluminium– water explosion, says Simensen, who believes the official report missed this because of a lack of relevant experts. Materials chemist Mark Ward at the UK’s University of Birmingham says Simensen’s theory looks reasonable. ‘Sprinklers firing water into molten Al could create finely divided Al which could react rapidly with water,’ he comments.
Niels Harrit, a chemist at Copenhagen University, has doubts over the official explanation that the aircraft impact and fires weakened the building and caused it to topple; his report of evidence for demolition has helped to fuel conspiracy theories. However, Harrit agrees that aluminium can react with water at elevated temperatures and that hydrogen/air mixtures are explosive.
In a letter to Simensen and his colleague, Harrit expresses frustration at the proliferation of non-scientific information on the collapse of the World Trade Center and calls for a public hearing. ‘A number of observations have to be accounted for before we can reach a generally acceptable model for the collapses,’ he wrote.
Simensen believes that it should be possible to look for solidified droplets of aluminium and aluminium oxide in the walls of neighbouring buildings as evidence for an aluminium–water reaction. In the event of a similar scenario in the future, he suggests turning off the sprinkler systems and launching missiles armed with fire retardant to cool the aluminium.