Addison Bain’s obsession with the Hindenburg disaster began on his lunch break in the early 1990s when three words caught his eye.

A rocket fuel expert, Bain liked to wander across the street from his office in the old NASA headquarters building to the Smithsonian National Air and Space Museum for inspiration and reflection among some of the most exciting flying machines ever built.

He stopped to admire a 28-foot replica of the Hindenburg, the airship considered the pride of Nazi Germany until a raging fire tore through it 80 years ago Saturday as it prepared to land in Lakehurst, New Jersey.

That’s when Bain noticed the plaque describing the Hindenburg disaster and the three words – “Its hydrogen exploded” – that set him on a controversial mission he’s still chasing nearly three decades later.

“I said, ‘No, no, no, there’s something wrong here,” said Bain, 81, about the explanation for what left 36 people dead.

“Hydrogen doesn’t explode.”

The fire that engulfed the Hindenburg devoured the vision of airships as an elegant passenger vehicle, and forever linked hydrogen – used on the Hindenburg and highly flammable  – in the public mind with the threat of inferno. The Hindenburg was destroyed in less than a minute, but the damage inflicted on hydrogen as a clean fuel source continues today.

The blaze, caught on black-and-white film and captured in a breathless radio broadcast, also ignited the public’s imagination, earning the disaster a place alongside the Titanic sinking and Amelia Earhart’s disappearance as a topic for endless speculation.

What caused the Hindenburg fire? Experts, historians and armchair enthusiasts are still disagreeing over the nuances of the answer 80 years later.

Bain, who retired in 1994 as NASA’s hydrogen program manager, set out to debunk the long-accepted conclusion that hydrogen proved the Hindenburg’s fatal flaw, that it leaked and was ignited by an electrostatic discharge. Bain’s goal: Exonerate the element he’s spent his life studying. He even wrote a book laying out what he thinks happened.

So what does Bain think brought the Hindenburg down?

Not so fast. Let’s back up a little.