 The Challenger disaster was one of NASA's greatest tragedies, and the lessons it taught us are still just as important today. The story of Challenger is pretty well known by now. On the morning of Tuesday, January 28, 1986, the crew of STS-51L boarded their spacecraft. At 11.38 local time in Florida, the space shuttle lifted off the launch pad, and it looked like it would be a beautiful, successful 25th mission of the shuttle program. But it never reached orbit, 73 seconds after launch, an explosion ripped through the sky, and NASA lost seven American astronauts live on television. In the wake of the accident, a presidential commission was established to figure out what exactly went wrong. The culprit, it found, was an O-ring. This was a joint seal between sections of the solid rocket boosters, those two rockets on either side of the main tank of the shuttle stack. The so-called Rogers Commission Report painted a very different picture of what looked to average observers on the ground like a beautiful launch. Right before liftoff, there was smoke coming from one of the joints on the right SRB. 66 seconds after launch, at the same point, they could see a flame coming from that same spot on the SRB. That flame grew and was pushed inwards and backwards by the aerodynamic slipstream. Eventually, it hit the main tank, the big orange external tank that was under the belly of the shuttle. The flame breached the main tank, and the first to rupture was the liquid hydrogen tank. It exploded with enough force to send the physical tank going into the liquid oxygen tank, forcing it to rupture as well. This meant that the two tanks, which were nearly full because it was only 73 seconds after launch, were ripe to become a massive explosion. This ripped the shuttle orbiter apart, and it was all because a joint seal failed on the SRB. But why did the joint seal fail? It turned out that the O-rings were designed to work at temperatures above 53 degrees centigrade, but temperatures on the launch pad around the time the crew ingressed the spacecraft that morning were almost freezing, just 36 degrees Fahrenheit. Physicist Richard Feynman, who was part of that presidential commission, made a brilliant demonstration of this fact in a press conference about five months after the accident. He took an O-ring, twisted it and put it in a clamp and then put it in cold water, just an average glass of drinking water with ice in it. When he released the clamp, the O-ring didn't bounce back to shape. It was clear evidence that if an O-ring was too cold, it would lose elasticity at least for a little bit, which meant that as the SRB started firing, the O-ring wasn't allowed, or able, rather, to expand to fill the gap. This allowed the leak, which allowed the flame, which allowed the entire shuttle stack to rupture and explode. Of course, this raised a much larger and much more significant question. If Morton Thygall knew that there were problems with O-rings at cold temperatures, and everyone involved in the launch knew that it was nearly freezing on the morning of launch, why did NASA launch it all? On this point, the Rogers Commission unveiled a disastrous culture at NASA. Not only were the concerns of Thygall engineers not properly communicated to NASA management, no one at NASA was concerned with the technical issues so much as the public relations issues that would come from not launching on time. You see, one of the main reasons people were interested in the launch of STS-51L was because Christa McAuliffe was on board. McAuliffe was flying as part of NASA's Teacher in Space Initiative, and the mission had her giving a live lesson from orbit on the fourth day of the mission. The launch on Tuesday meant that the broadcast would be on Friday, when all the kids in America were in school. If NASA delayed the launch by another day, that broadcast would fall on Saturday, and that would mean nobody would be in the classroom to watch. It would be a massive PR loss for the agency. Another concern NASA had was that President Ronald Reagan was meant to mention McAuliffe and the Teacher in Space program in his State of the Union address that Tuesday night. If NASA didn't launch on Tuesday, it wouldn't get the publicity that would come from a mention in the State of the Union address. Add to that that NASA was falling badly behind on its shuttle promises. When the program was incepted, NASA had the goal of launching upwards of 50 shuttle missions a year. That is so many space shuttle flights, especially considering the fact that the agency only had four orbiters at the time. So in December of 86, NASA was only launching its 25th mission. That's an average of just five launches a year, not 50. NASA really needed to launch on time and fly a successful mission to prove that the program was worth the taxpayer dollars. The presidential mention would of course help that. Ultimately, the Rogers Commission found that the cause of the Challenger accident was an o-ring. It was a technical flaw, but the root cause of the accident, the cause that had allowed that flaw to fly, was NASA's own culture. The Challenger disaster also changed America's relationship with spaceflight. Not 20 years after the moon landing, when we were supposed to have people on Mars already, America was reminded that spaceflight is dangerous, and that even though we may have developed the technology, the technology can still turn back on us and show us who is really in control. This is scratching the surface of a much larger story, one that I took a deeper dive into over on history.com. If you would like to read my full thoughts on how the Challenger disaster affected American spaceflight, be sure to check it out. The link is in the description. If you love spaceflight history, be sure to subscribe for weekly vintage space videos, and remember that you can now sponsor vintage space. That means that you have a chance to help make sure that I can keep making the content that you guys love. And of course, leave me all of your thoughts in the comments below. Any questions, comments, thoughts, things you'd like to see in future episodes, leave all of that down in the comments. And you can also follow me on social media for daily vintage space content. That's Instagram, Twitter, and Facebook. And as always guys, thank you so much for watching.