On January 28, 1986, I was working in the lab supply storeroom on the first floor of the Biological Sciences Building at the Ohio State University. A graduate student stuck her head in the door and said, “Did you hear, Mike? The space shuttle exploded!”

That — not the subsequent video replays — is the moment I’ll never erase from my memory.

I asked questions, but she didn’t have many details. What she had heard wasn’t encouraging. I hoped she’d heard wrong.

I imagined a hundred different scenarios. There had been a terrible accident on the launch pad, but everyone had gotten safely away. If the shuttle exploded in orbit, ground controllers would see only a loss of downlink: the radio would go silent, and the constantly-changing numbers on their consoles would stop changing. Then someone would observe that radar was tracking multiple targets. I didn’t want to think of the scenarios where the astronauts didn’t escape.

We’ve been putting people onto rockets since 1961, and every journey begins with a lump in the throat, and a sense of dread that takes the breath away, and makes us whisper “Godspeed.” When do we breathe easy?

Before the Challenger disaster, I think we breathed a sigh of relief when the shuttle cleared the launch tower. The rockets had all lit, and hadn’t exploded. The spacecraft was on its way. Everything was going to be alright.

The night of the Challenger explosion, I saw a high-school class cheer and groan when the shuttle exploded. The sequence of launch events had been explained to them. Most saw the two solid-rocket boosters (SRBs) flying away, and thought it was the planned SRB separation. Others sensed instantly that there was something wrong.

Later, we learned that the Challenger was destroyed by a flaw in one of the SRBs. After the Challenger disaster, we held our sigh of relief until after the SRB separation. I held mine for MECO — Main Engine Cutoff. I suspect the people really in the know didn’t relax even then.

The shuttle Columbia broke up on re-entry 17 years and 4 days after the Challenger disaster. Controllers lost their downlink. Radar started tracking multiple targets. Witnesses heard a sonic boom that lasted for thirty seconds or longer. What they heard was actually a sequence of sonic booms — the spacecraft had broken into pieces, and each piece made a separate boom.

Email from my brother living near Los Angeles:

At about 5:02AM Tuesday, August 9th, a double sonic boom rattled Southern California announcing the return of the space shuttle Discovery.

It woke me up. .......... Hoorah!

I saved my sigh of relief until the wheels stopped turning.

Godspeed, Discovery, and welcome home.