Khalid Sheikh Mohammed and his vacuum cleaner

Khalid Sheikh Mohammed, the alleged 9/11 mastermind captured in 2003, kept in secret CIA detention facilities and water-boarded 183 times, wanted to design a vacuum cleaner — likely to keep himself sane.

An exclusive Associated Press report claims Mohammed, or KSM, who has a bachelor's degree in mechanical engineering from North Carolina A&T State University, had been permitted during his 2003 detention at a CIA black site to design the household appliance.

The story gives a sneak peek into the life and mind of Pakistan-born KSM, and perhaps more importantly, the thought process of CIA captors who excessively used "enhanced interrogation" techniques — what many consider to be torture. 

So why did the authorities indulge this man's hobby? What if KSM actually stood trial or decided to cooperate one day? In that instance, it would help if he was mentally sane. (KSM is being tried in a military tribunal.) 

"We didn't want them to go nuts,'' a former senior CIA official told the AP.

The project appears to have worked, with KSM reportedly in good health.

You can't see the vacuum cleaner designed by the same mind that American security officials believe orchestrated the Sept. 11 terrorist attacks.

In fact, it's unclear how far KSM got with his project, which likely ended after his move to Guantanamo when the CIA's prison in Romania closed in 2006. The design is part of an operational file, which means it's highly classified and could never be seen by the public.

"It sounds ridiculous," Jason Wright, KSM's military lawyer, told the AP. "But answering this question, or confirming or denying the very existence of a vacuum cleaner design… would apparently expose the US government and its citizens to exceptionally grave danger."