Authors: David Hitt,Heather R. Smith
Astronaut Terry Hart recalled his launch day at
’s Kennedy Space Center (
) in Florida, home of the Space Shuttle’s launch complexes: “It was a clear, cool morning there and we went through the whole morning, going through the traditions of having breakfast together, and there was always a cake there for the crew before they go out. And then going into the van and realizing that all the Mercury guys went on that van, it was really a very heady experience.”
For three-time shuttle veteran David Leestma, that experience of waving to people while walking out to the Astrovan, suited up and ready for launch, was a memorable moment. “We always called that the last walk on Earth,” Leestma said. “There’s always crowds of people there to see you in case you never come back or something. It was one of those little bits of kind of gruesome humor. And then you go out to the launchpad, and you’ve been through this. You’ve been there many times before, because you train in the orbiter a few times and you have countdown demonstration tests and things. And this time you get to the pad and there’s nobody there. You go, ‘Ooh.’ And the vehicle is steaming and creaking and groaning and you go, ‘This is for real.’”
On the launchpad, the Space Shuttle is positioned vertically, its three major components having been stacked together in the enormous Vehicle Assembly Building at Kennedy Space Center before having been rolled out—slowly—to the launchpad atop a huge crawler. Standing tallest is the orange-brown external tank. The external tank has no engines of its own
but carries the liquid fuel for the launch in two separate tanks, one containing liquid oxygen and the other holding liquid hydrogen. The tanks are supercooled to maintain the fuels at the cryogenic temperatures needed to keep them in liquid state—below minus four hundred degrees Fahrenheit in the case of the hydrogen. Fully fueled, the external tank weighs about 1.7 million pounds.
On either side of the external tank is a slender, white solid rocket booster (
), the two of which together provide the bulk of the power for the first two minutes of the launch. Once ignited, they together provide 6.2 million pounds of thrust. Their name comes from the fact that they carry their propellant—consisting largely of aluminum mixed with an oxidizer to cause it to burn—in a solid, rubbery form.
And then there’s the orbital spacecraft itself, the winged, white-and-black orbiter. Near the nose of the orbiter is the crew cabin, where the astronauts fly the vehicle and live during their mission. Farther aft is the payload bay, with its two large doors. And in the rear are the three Space Shuttle main engines, fueled by the external tank, each capable of generating a thrust of almost half a million pounds.
By launch day, the launch complex’s servicing structure has been rotated back, revealing the orbiter. The shuttle is ready for its crew. The entrance to the orbiter is through a hatch in the side of the crew cabin, near the top of the vertically stacked vehicle, almost 150 feet above the launchpad.
Leestma recalled the process of boarding the vehicle via an elevator in the launch tower and a gantry arm near the top of the structure:
As usual, people don’t say much in elevators. It’s true whether you’re in a hotel or on the launchpad. You kind of watch the numbers tick by, and instead of floors, they do everything in feet in the elevators, so you’re so many feet above sea level. And then across the gantry, and when you walk across the gantry you’re looking down into the flame trench. And you’ve been there before, but the obvious thing that’s striking you is that this is for real, we’re going to go. At least you hope we’re going to go today. . . . You get up to the White Room, the access arm, and there’s only two, maybe three people there and that’s it. There’s nobody else on the pad and everybody’s blocked off for four or five miles away. This is for real. And it’s groaning and moaning and you know that it’s going to launch, and it’s fueled and ready to go. It’s a big bomb there, sitting on the pad. And you hope that all
the fire goes down and you go up, and let’s go, let’s get on it with it. It’s great. . . . We got strapped in, and again, the guys strapping us in were a lot of the same guys that strapped in Al Shepard on his flight [to become the first American in space during Project Mercury]. So it was a very heady time. . . . You get in and you just can’t wait for it to happen.
Astronaut Jerry Ross, who was the first to launch into space seven times, said journeying out to the launchpad when the vehicle is fully fueled and ready to go is quite different than going out there any other time, not only because of the reality of the situation, but because the shuttle itself is different.
The vehicle really does give you this sense that it’s an animal that’s awake and just ready to go do something. When you go out there and the vehicle’s not fueled, it’s not hissing, it’s not boiling off vapors, it’s not making noises that you don’t hear, that you do hear when it’s fueled. And there’s the tremendous amount of anticipation. My first flight was the twenty-third flight of the shuttle, and I had listened to every crew come back, and I took very detailed notes of their debriefings, which were quite exhaustive early on. I listened to everything they said, and they would give us a very detailed description of what it was like, what the sensations were of launch. I put that into my databank, and I would daydream about that when I’d go running or work out at the gym or something like that. I knew it was going to be a pretty exciting ride.
The crew cabin of the shuttle has two levels. The “upper” deck is the flight deck, where the commander and pilot sit at the vehicle’s controls, with a bank of large windows in front of them. The flight deck has room for up to two more astronauts to sit during launch, and behind them are windows looking into the payload bay and the controls for the orbiter’s robotic arm.
Below the flight deck is the mid-deck, where the rest of the crew sits during launch. Once in orbit, the mid-deck serves as the primary living area for the crew, with storage lockers and the orbiter’s kitchen and bathroom and main sleeping area. The mid-deck also provides access to the vehicle’s payload bay. During launch, the mid-deck has very limited visibility, and the astronauts sitting there depend largely on word from the flight deck and the very obvious physical sensations of launch to know what’s going on during ascent.
-1 crew members Commander John Young (left) and Pilot Bob Crippen inside Space Shuttle Columbia in the Orbiter Processing Facility at the Kennedy Space Center. Courtesy
Prior to launch, once the crew members have boarded the orbiter and been strapped into their seats, the waiting begins. Traditionally, the astro
nauts board about three hours before the scheduled launch time, lying on their backs in their chairs until launch.
Very often, this is as far as things get. Any number of issues, from unacceptable weather conditions to a technical glitch with the vehicle and more, can result in the launch being scrubbed and pushed back. In those cases, the astronauts are helped out of the vehicle, and work begins to prepare for the next launch attempt. “Probably one of the most frustrating things is when you get near your takeoff time, your launch time, and then you know there’s a problem, and you go, ‘Please solve it. We don’t want to wait here. Get us off the pad,’” noted Leestma. “The last people you want to have to make the real technical decision whether you go or not is the crew, because they’re always, ‘Go.’ ‘Yeah, we’ll be fine. Let’s go.’ That’s why you’ve got a whole team of folks in the launch control room doing that.”
But on other occasions, the weather does what it’s supposed to, the vehicle is operating properly, any number of other factors come together as they should, and launch preparations continue to proceed. Finally, as launch nears, the Space Shuttle main engines “gimbal,” or tilt, to test that they will move properly, and at five seconds before launch they are ignited to make sure all three engines are functioning properly. The vehicle continues to sit on the pad, but the firing of the engines causes it to pitch slightly. It then rocks slightly back, a process called the “twang,” and when the stack is vertical again, at T minus zero, a spark at the top of the fuel casing of the solid rocket boosters ignites the propellant. With more than seven and a half million pounds of thrust pushing the Space Shuttle upward, it begins to move.
Shuttle pilot and commander Fred Gregory recalled the feeling of the main engines first firing, describing it as almost a nonevent. “You could hear it; you were aware of it. It sounded like some kind of an electric motor at some distance, but you looked out the window and you saw the launch tower there and the launch tower moved back. At least that’s what you thought, but then you realized the orbiter was moving forward and then back, and when it came back to vertical, that’s when those solids ignited and there was no doubt about it. You were going to go someplace really fast, and you just watched the tower kind of drop down below you.”
At the very beginning of the ascent, there’s the brilliant light of the engines, which no photograph or video can truly capture: a brightness that
seems to puncture the sky. The brilliance of the flames from the engine is dramatic during the day, and far more so when they light up the sky at night. Payload specialist astronaut Charlie Walker recalled the experience of launching on the Space Shuttle in the dark:
At night, you look outside, and this launchpad is a blue gray from the xenon light reflections bouncing off of it, with a completely black background behind it. All of a sudden the launchpad brightens up with the solid rockets igniting. The launchpad brightens up to a yellow gray, but then the whole background, suddenly there’s like a sunrise that’s happened over Florida. You can see the Florida landscape for miles back that way. Sure, the sky is still black, but suddenly Florida has been illuminated by a new sunrise. I can see the Florida countryside, and it’s a yellow, white-yellow-orange color, the coloration of the brilliant, hot flame from the solid rocket boosters.
Like Gregory, Jerry Ross recalled that, while he was aware when the main engines first ignited, things didn’t really get exciting until the solid rocket boosters fired.
As the shuttle’s main engines came up, you could really feel the vibrations starting in the orbiter, but when the solid rocket motors hit, when they ignite, it’s somebody taking a baseball bat and swinging it pretty smartly and hitting the back of your seat, because it’s a real “bam!” And the vibration and noise is pretty impressive. The acceleration level is not that high at that point, but there is that tremendous jolt as the solid rocket motors ignite, and you’re off. I’ll never forget the vibrations of the solid rocket motors. As we accelerated in the first thirty seconds or so, the wind noise on the outside of the vehicle just became really intense, like it was just screaming. It was screeching on the outside. I was already thinking about “what am I doing here” before then, but [it was] just a sheer, incredible experience of the energy.
In many ways the flight deck, with its large windows, is the superior seating for experiencing the launch. In one way, however, the mid-deck has the advantage. Since the pilot and commander are busy with the tasks of making sure the vehicle is operating properly during ascent, they don’t have the luxury of stopping to really take in the experience of the launch. While the astronauts on the mid-deck don’t have the same view as those on the flight deck, they have the freedom to focus more on the sensations. Hart, for example, recalled being able, as a mission specialist, to really enjoy the experience.
You talk a lot [to other astronauts about what launch is like], obviously, and you see a lot of pictures, and you think about it a lot, so you think you’re pretty well prepared and you probably won’t have too many surprises, but I had a couple of surprises. The shake, rattle, and roll for the first two minutes, that was about what I thought, maybe even a little bit less than what I thought it would be, because the solid rockets kind of have a “whoof-whoof” [rumble]. You don’t really hear it; you more feel it. It’s like a very low-frequency rumble, and just a tremendous sense of power as you lift off and all.
Another part of the experience that simply cannot be replicated on the ground is the pressure of the g-forces during ascent, according to
-6 commander P. J. Weitz: “The value of our simulators ends when those engines light and you lift off. They try to fake you out a little bit by tipping the Shuttle Orbiter Simulator and that, but it doesn’t compare with three shuttle main engines and two solids going. As I tell people, I said, ‘You know you’re on your way and you’re going somewhere and you hope they keep pointed in the right direction, because it’s an awesome feeling.’”
Weitz compared the launch of the Space Shuttle to the launch of a Saturn IB, which he took into space on the first Skylab mission. The Saturn, he said, produced about half again as much acceleration force as the shuttle’s three gs, and the force was felt in somewhat different ways on the two vehicles. In the Saturn, the thrust was “actual,” or directly in line with the vehicle, so the crew was pressed directly back into the couches. With the shuttle, on the other hand, because of the way the orbiter is stacked on the external tank, the thrust from the main engines is offset from the vehicle’s center of gravity, meaning that the crew members aboard felt the pressure pushing them not only into the back but also into the bottom of their seats.