The cause of a SpaceX explosion that resulted in the destruction of a crew capsule and sent orange smoke into Space Coast skies has been pinpointed, the spaceflight company confirmed Monday.

Just 100 milliseconds before an uncrewed Crew Dragon capsule fired its eight SuperDraco thrusters during a test at Cape Canaveral Air Force Station on April 20, the capsule exploded, leaving Landing Zone 1 littered with fire, debris and chemicals. The cause, SpaceX said, was traced down in recent weeks to a reaction between a liquid oxidizer – nitrogen tetroxide, or NTO – and a titanium check valve, which caused an ignition and the subsequent explosion.

According to accident investigators, a component allowed nitrogen tetroxide to leak into the spacecraft’s pressurization system tubes well before testing began. When the pressurization system activated and attempted to simulate a firing of the SuperDraco thrusters, a “slug” of the NTO that had leaked into the tubes was blasted through at high speed, resulting in ignition with the titanium valve.

Tuesday marks 50 years since three men in space suits set off on the greatest scientific adventure of all time. As the astronauts of Apollo 11 headed to the moon, the women of NASA were blazing new trails on Earth. “CBS Evening News” anchor Norah O’Donnell has their story.

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Fifty years ago on July 16, 1969, a three-man crew launched into space from Kennedy Space Center in Florida aboard the Apollo 11 spacecraft.

On the evening of July 12th, SpaceX technicians put Starhopper’s freshly-installed Raptor – serial number 06 (SN06) – through a simple but decidedly entertaining test, effectively wiggling the engine in circles.

Designed to verify that Raptor’s thrust vectoring capabilities are in order and ensure that Starhopper and the engine are properly communicating, the wiggle test is a small but critical part of pre-flight acceptance and a good indicator that the low-fidelity Starship prototype is nearing its first hover test(s). Roughly 48 hours after a successful series of wiggles, Starhopper and Raptor proceeded into the next stage of pre-flight acceptance, likely the final more step before a tethered static fire.

Routine for all Falcon rockets, SpaceX’s exceptionally rigorous practice of static firing all hardware at least once (and often several times) before launch has unsurprisingly held firm as the company proceeds towards integrated Starhopper and Starship flight tests. Despite the fact that Raptor SN06 completed a static fire as recently July 10th, SpaceX will very likely put Starhopper and its newly-installed Raptor through yet another pre-flight static fire, perhaps its fourth or fifth test this month.

The small, fast-moving New Horizons spacecraft is likely to be the only Pluto mission in the lifetimes of many of us. It changed forever the way we on Earth perceive this outermost world and its moons.