Our second stop was Launch Pad 39A, which has been left intact with mobile launch platform and stack since STS-135’s launch on July 8th, 2011.
All astronauts that walked on the moon were launched from this platform. (Apollo 10 launched from 39B, but that one didn’t land on the moon.) And this pad launched 92 of 135 space shuttle launches.
The VAB is exactly 3.5 miles away from the launch pads, which is the closest a human can be to a shuttle launch before sustaining physical damage.
The last picture shows how far away we stopped, but then we went around to the rear and got to stand in the flame trench! (Do you see that big gray patch on the left wall in there? That’s from STS-124, and when Discovery launched, a huge bunch of Apollo-era bricks were dislodged and went hurtling through the air at hundreds of miles an hour. (You can still see dents and repairs in the perimeter fence behind the launch pad.) They’re currently renovating 39B’s flame trench to a) avoid a repeat and b) withstand the upcoming Space Launch System launches.
That big metal thing in the middle of the flame trench is the deflector. For Saturn V launches, it was set further back, deflecting all the heat and exhaust towards where I was standing. But for space shuttle launches, it was set neatly in the middle between the SRBs and the space shuttle’s engines. (If you look at the bottom of the platform, you can see three holes— two for the SRBs and one for the engines!) The SRBs do most of the legwork for liftoff, so that’s 80% of the energy coming right towards where we were standing.
That big white tank is the liquid hydrogen tank, which was used for fueling the external tank (each gets its own compartment, which is good, because when they combine, you basically get liftoff). There’s another one on the other side that contains liquid oxygen. Both of these substances are very, very cold: the hydrogen checks in at −423 °F and the oxygen is kept at −297 °F.
On the bus we watched a little video about liftoff, learning about when and why everything happens during launch.
- At T-minus 10 seconds, if you’re watching a video, you’ll see a bunch of little sparks firing underneath the shuttle. This is to make sure to catch and burn off any extra hydrogen that may be sitting down there, because it’d be Very Bad News is there was any still there when it’s time to go.
- The main shuttle engines fire at 6.6 seconds. The shuttle pitches forward from the thrust, which is called the twang, but it resets quickly, since it can’t go anywhere yet! The SRBs are still attached to the platform by explosive bolts.
- At 0 seconds, the bolts are detonated and the SRBs fire and it’s all uphill from there!
The big water tower you see in the last photo pumps… well, water. It was quickly discovered after the first couple launches that it was just too loud up there. The decibel level was around 180, I believe, and it was enough to knock tiles off the orbiter (which, as we have learned, is NOT a good thing). So they decided to pump in about 900,000 gallons of water prior to and during liftoff to help suppress the sound. (Most of that white smoke you see right after SRB ignition is steam!) This is known, creatively, as the Sound Suppression System. However, this system is not foolproof, as we discovered from the loss of Columbia. :(
The second-to-last photo there is part of the emergency egress system. If something were to happen while the astronauts were in the tower, like a hazmat situation, they (and any crew still around) could run back down the gangway, file into one of seven baskets (each of which held three people), and the baskets would slide 1200 feet down a giant zipline, going a max of 55mph! From there they had two options— they could either hop into a waiting vehicle (an M113 Armored Personnel Carrier) and leave the premises as quickly as possible, or they could go into the bunker under the hill, where they had food and water for a couple weeks and could survive until the hazmat crew OK’d their escape.
Only one person ever actually did the zipline, though, and that was Kennedy Space Center director Bob Cabana. He got to the end and said, yep, it works.
Here’s a nifty video of the crew releasing the baskets for the very last time.
At any rate, it was really cool to be able to see this, especially since it probably won’t be there much longer. SpaceX has put down a bid to use the platform for their launches over the next ten years, and it’s highly unlikely they’ll leave very much of the structure intact. (They’re tired of using Cape Canaveral’s launchpads— they’re military over there, and SpaceX is apparently tired of following all those rules. Haha.)