"Atlantis, the weather plane is making one last check of some clouds and as soon as the pilot gives us a clearance, we'll continue the countdown."
The Commander answers the Launch Director's call, "Roger.  We're ready."
I hear the announcement through my "Snoopy" cap headset and think to myself, Please, let the weather be okay and let us launch. 
I'm Mission Specialist 1, right behind the Pilot, in the cockpit of the space shuttle Atlantis.  I'm ready for my second ride into space.  I'm also miserable.  I try to wiggle in my seat to get comfortable but it's impossible.  I have 85 pounds of equipment wrapped around my body: long underwear, pressure suit, boots, helmet, gloves, parachute, oxygen bottles, life raft, and survival harness.  There are straps coming over my shoulders, between my legs, and around my waist, all holding me tightly to the steel chair.  The space shuttle seats are not couches like they had in the old days of the space program.  Then, there were just a few astronauts.  Now, there are many and it would be too expensive to build a couch for all their different sizes.  So the seats are all the same, just flat plates of heavy steel with thin cushions covering them.  They're a torture to lay in and I've been laying in mine for the past 4 hours waiting for the weather to clear.  Try tilting your chair on the floor and then laying in it for a couple hours on your back.  You'll have a sense of what an astronaut feels like waiting for launch.

And the diaper I'm wearing is soaked.  Yes!  A diaper!  Astronauts wear diapers during launch.  When you're in a space suit and strapped on your back to a seat, you can't get up and use the shuttle toilet.  So, astronauts wear diapers.  Actually, there are three times when an astronaut has to wear a diaper:  during launch, during reentry and during a space walk.  During each of those times, it's impossible to get to the toilet.  So, I'm laying in a very wet diaper, knowing why babies cry when they have wet diapers.  It's gross!
I try to gain some relief from the pain by inflating my pressure suit.  It expands like a big, orange balloon and gives me a little room to wiggle.  Actually, it is a balloon.  It's a balloon in the shape of a suit.  We wear it during launch and reentry in case the vibrations should cause a window to break or air to leak out of the cockpit for any reason.  If that ever happened, and we weren't wearing a pressure suit, our blood would boil inside our skin and we would die.  The suit has nothing to do with the g-force pressure of the rocket pushing us.  Rather, the word "pressure" refers to the need to keep air pressure on our skin so our blood doesn't boil.
"Atlantis, the weather pilot just reported that the clouds are no longer a problem.  We'll be coming out of the hold in five seconds...four... three...two...one...T-minus 9 minutes and counting."
"Roger, we see the clock running."
I silently shout for joy, Finally, we're counting down to launch!  Each of the three computer screens has a digital countdown clock and those flicker toward zero.
Humming, whirring, flashing electronic boxes are now checking everything about the shuttle and sending the information, the "data", to the Mission Control team.  The thought of that wonderful team of men and women watching over us erases a little of the fear that we feel.

Astronauts get the "glory" part of a space mission.  You see them floating around the cockpit and doing space walks.  You see their pictures in the newspapers and the President shaking their hands.  But have you ever thought about the rest of the NASA team?  It takes thousands of people working together as a team to accomplish a space mission.  Nobody can do it by themselves.  It's just like a baseball or soccer team.  The person that scores the winning goal is the one that everybody runs to lift on their shoulders and congratulate.  But did they win the game by themselves?  No.  Somebody passed the ball to them.  Somebody blocked for them.  Nobody wins the game and nobody flies into space by themselves.  It's a team effort.  Everybody depends upon everybody else.
"Okay, review your emergency escape procedures."
The order is from the Commander.  He wants us to look over the procedures we would have to follow in case there's an emergency before launch.  Remember, we are sitting on top of 4 million pounds of dangerous fuel and if something went wrong and there was a fire before liftoff, we would want to shut the engines off and get away as quickly as possible.
I look at the "checklist" of emergency procedures that is velcroed on the back of the Pilot's seat.  It tells me the steps I would need to follow to release my seat belts, oxygen hoses, and communications cords.  Then, it says to crawl from the cockpit, run across the launch pad platform (that's called the "gantry") and jump in a basket that's 200 feet above the ground.  As I read the steps, I think, I hope I never have to do this!  It would be an awesome ride, like something out of an Indiana Jones movie, but it would also be very scary.
Just imagine for a moment, that it's happening to you........
"Atlantis!  We see a fuel leak!  Get out!  Mode 1 egress!  Mode 1 egress!"  The launch team has detected an emergency that might cause the shuttle to explode and they want you to escape - to egress - in the basket.
Because you've just reviewed your emergency procedures it only takes you a moment to release all the connections that hold you to the seat.  Next, you  roll off your seat and crash onto the back instrument panel.  Remember, the shuttle is standing on its tail, so the back of the cockpit is now the "floor".

There's no room to stand up, so you crawl on your hands and knees to the side hatch.  In ten seconds you have that open and crawl through it and onto the gantry.   Water is everywhere!  What's going on?!  Then you remember.  The launch team has turned on the water sprinklers to help protect you from any fire.
After making certain that the rest of the crew is out of the shuttle, you run through the water spray and jump into an escape basket.  The ground is 200 feet straight down and the basket swings and bounces.  You think this is the scariest thing you've ever done.
BAM!  You smash your fist onto a paddle that cuts a cord and releases the basket.  This begins your escape off the launch pad.  You can't go down the stairs or the elevator.  It would take too long.  Besides, if there was a fire at the bottom of the gantry, running down the stairs or taking an elevator would put you right in the middle of it.  The escape basket takes you to the ground while moving you away from the rocket.  It slides on a steel cable that stretches sideways a thousand feet from the launch pad.
What a ride!  A loud hissing sound comes from the cable as the basket accelerates.  The ground rushes toward you.  If you crash into it, you'll be killed.  What's going to stop you?
WHAM!  Just before the basket reaches the ground, it slaps into a net that's hung between two poles.  The net drags your basket to a stop.
But you're still not safe.  Even though you're a thousand feet from the launch pad, a big explosion could kill you.  Get going!
You jump from the basket and run into a nearby
underground bunker.  Or maybe you decide the danger is so great that even the bunker wouldn't protect you.  So you get in an old army APC, armored personnel carrier (it looks something like a tank), and drive away.  NASA parks an APC near the bunker for that purpose.
Good job!  It only took you four minutes and thirty-five seconds to un-strap from your seat, get out of the shuttle, run to the basket and slide down the cable.
My countdown continues.  The clock shows T-minus six minutes.
I check that all of my straps are tight.  There will be a lot of vibration during launch.  I double check that my parachute is attached.  After the solid-fueled boosters burn out and the liquid-fueled engines stop, the space shuttle is a glider.  That means there's always the possibility something could go wrong and we might not be able to glide to a runway for landing.  In that case we would bail out, using parachutes that are attached to our backs.  After floating into the ocean, we would get in small life rafts that are also folded up and clipped to our backs.  Hopefully, we could stay alive long enough for a helicopter to reach us.
"Atlantis, start the APUs."
The call comes from the Launch Director.  The countdown has reached T-minus 5 minutes and it's time to start the hydraulic motors that will steer the three, giant rocket engines.  APU stands for Auxiliary Power Units.  Calling every piece of equipment by their complete name would be tongue twisting, so astronauts and the rest of the NASA team use abbreviations, like APU, IMU, EPS, MPS, MECO, MLS.  There are hundreds of them that we learn in our training.
The APU switches are on the Pilot's side, so I watch him follow the checklist.  Everything an astronaut does is written on a checklist.  The walls, ceiling and instrument panel are papered (velcroed) with them.  Why do we use checklists?  You never see anybody on Star Trek using a checklist.  But Star Trek is make believe.  Nobody on Captain Picard's Enterprise is really going to die if they make a mistake.  But in the real world, a mistake could threaten an astronaut's life.  There are nearly 2000 switches and controls in the shuttle cockpit, so a mistake is certainly possible.  Even though we practice the mission until we know what every one of those switches does, we never trust our memories.  We always do things by following our checklists.
The APU motors are at the back of the shuttle, but as they start I can feel their vibrations in the cockpit.  For the first time, I get the sensation that the machine is alive.  It's like some giant beast stirring from its sleep.

No longer do I think about my backache and wet diaper.   Now, I'm scared.  In just a few minutes Atlantis will liftoff in a thunderous cloud of fire and smoke.  With such enormous power, there's a lot that can go wrong and put us in danger.  The rocket has many parts.  It's a very complicated machine.  So, in these last few minutes before launch, I'm scared.  My heart pounds inside my chest.  I can feel it in my throat...THUD...THUD...THUD...like I've just run a race.  I try to swallow but my mouth is dry.  Fear does that to you.  It makes your heart pound and your mouth feel like it's full of cotton.

"Atlantis...Close visors."

"Roger...Closing visors."

The countdown has reached T-minus 2 minutes and the checklist says to close our helmet visors.  These are the clear, plastic coverings on the faces of the helmets.  Before I close mine, I pull a drink container from a velcro patch on the wall and suck down a few swallows of water through a plastic straw.  The container is the same design as we use on orbit.  It's a foil pouch with a straw on the end.  I clip the straw closed, re-attach the container to the velcro and lock my visor down.  A cool flow of oxygen swirls around my face.  If a window should break during launch, now I'm completely protected.
The beast awakens some more.  I can feel it shaking.  The computers are making a final check of the steering controls and it causes the rocket to sway back and forth.  The bottoms of the two solid-fueled rocket motors are held to the launch pad by 8 giant threaded nuts, so I know we can't fall over.  Still, the shaking is another indication that the shuttle is readying itself to fly.  My fear increases and my breathing becomes faster...SSSSSSSSSS...SSSSSSSSSS ...SSSSSSSSSS.  I can hear it inside the sealed helmet.  It's a hissing sound as air is inhaled and exhaled.