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Why Endeavour scrubbed - SpacePod 2011.04.30

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Hey space cadets! Here's a random, quick Space Pod I guess for why space shuttle Endeavour did not launch on the first attempt for STS-134. And, if you're watching live, you heard them starting to talk about APU heaters, and it became a bigger and bigger issue until finally we scrubbed because two APU heaters had failed. So what is an APU heater? Why do we care? An APU is an auxiliary power unit, and an auxiliary power unit is a very deceiving name because it sounds like it's auxiliary, it's spare, it's extra. But in actuality it is a very very important piece of equipment. The APUs are what provide the hydraulic pressure for gimballing the space shuttle main engine, so being able to move the space shuttle main engines, which basically steers the space shuttle, as well as controlling the control surfaces of the space shuttle, so the flaps and the tail and stuff like that. If you're ever on an airplane and you see the wings kind of move up or down like that, that would be the APU doing that. The space shuttle main engines are powered by hydrazine-based APUs and during ascent it's not as big of a deal to have those heaters going. Obviously they want to make sure they're working. The thing is, they only need it during ascent or launch and then the landing itself. Or deorbit burn and landing and it's going to be spending a couple of weeks in space without any access to real heat or anything like that. And they could just eventually radiate out and then freeze up. We don't want that because if we start to land and you have frozen APUs, you can't provide hydraulic pressure to the vehicle and all of a sudden you can't control your vehicle and you can't do the controlled S-curves and actually steer the vehicle to land it because they can't move the flaps of the space shuttle. And remember, the space shuttle is unpowered when it lands. It's a glider. It has no engines, no jet engines, nothing like that. So if they can't move those flaps, they can't steer it. It's just going to go *thunk* and be done. That's why the APUs are so important and that's why the heaters are so important! We don't want the APUs to freeze while it's in orbit. So that's what's going on. They have delayed it no earlier than this Monday, which is a 72 hour hold. It's a little bit longer than we at the press site thought that it was going to be, of course we didn't know the magnitude of the problem at the time. We actually were thinking, what was it, 24 hours at first? We thought it was going to be about 24 hours, maybe 48 hours. And then they announced 72 and we were like, "Whoa!" So then the next steps are they're going to bring the rotating service structure back around the orbiter after all the fuel has been pulled out of the external tank. They're going to go in there, they're going to look and see what's going on. There's an A side and a B side to these APU heaters. It sounds like it was the B side that was malfunctioning and it was affecting more than one heater. And once they isolate the problem, they'll hopefully be able to fix it pretty quickly without rolling it all the way back to the Vehicle Assembly Building, which by the way if they if they do need to roll it back to the Vehicle Assembly Building, we are not launching at this time. It's going to be a month or two before we go. But they're going to try to fix it while it's still at the launch pad and see what they can do to get it going. And hopefully we'll be able to fly this Monday. So that is why we weren't able to fly today. The stuff that controls the ability to move the vehicle around, it broke. So no launch for today. Here's hoping that this Monday is a successful final launch of Space Shuttle Endeavour. I'm just hoping it's a little less windy. Look at my hair, this is just insane! Wow, this is actually what it looks like after launch day today. It was windy onsite! I did want to thank everyone for joining us during our live show. It was a lot of fun. We had people calling in via Skype. We had people asking their questions via Twitter, E-mail, all of it! It was great and I hope you guys will join us again for our launch coverage of STS-134, the final flight of Space Shuttle Endeavour.

Video Details

Duration: 4 minutes and 1 second
Country: United States
Language: English
Genre: None
Views: 73
Posted by: spacevidcast on May 3, 2011

I may be in my hotel room, but it's time to get some SpacePods started again and explain exactly why Endeavour scrubbed today!

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