This is an LA Times Studios podcast.

Hi, I'm Faith Pino from LA Times Studios in Washington, D.C.

Here are some of today's top stories from the Los Angeles Times.

40 years ago today, the spacetle Challenger exploded 73 seconds after taking off at Cape

Canabrell's Kennedy Space Center.

But what went wrong that day?

Ed Kellyn Turner, education manager at the National Space Center in the UK, explains.

Now, inside those boosters, there was something called an O-ring,

which is basically sort of like a rubber seal.

And it was found that, due to it being so cold on the day of this launch,

that those rubber O-rings sort of seized up,

so they weren't actually providing a good enough seal. So hot gas escaped

when the booster was actually fired and started melting through the strut that connected

the booster to the main tank. After that strut failed, the booster basically pivoted and

collided with the main tank causing that explosion.

Kristen McColliffe was going to be the first teacher in space.

What I really remember was that she's the kind of person that used to stir that kind of

independent interest. She was extremely enthusiastic. You know, that's one of our hallmarks

of her teaching style, that enthusiasm, her cheerfulness, to be able to support students in a very happy and kind way.

My last encounter with her, I think, is just an illustration of her general personality. This was about the time that she was

doing the anti-gravity testing, you know, when they go up in the plane and down and up and down

so that they get to float in the plane. And I ran into her at the hallway. We were talking about this,

...