NOTHING I HAD EVER SEEN, HEARD, OR READ about a space-shuttle launch prepared me for the real thing. Everything happens too quickly.
Night is instantaneously transformed into day as the booster engines ignite. The incandescent light of the rocket exhaust, so bright that its image burns into my retina, is followed by a long plume of dark smoke as the shuttle swiftly soars into infinity.
It takes 15 seconds for the sound to reach us at the viewing stand three miles away. When it does, I feel it as much as hear it, rumbling deep within my chest.
Two minutes into the flight, I can see the fiery trails of the booster engines at cut-off. At eight and a half minutes the spacecraft is in orbit, a brilliant point of light racing through the night sky.
The public and the media have become blasŽ about shuttle missions, but at Cape Canaveral every launch is a happening. STS 104 was even more special, because one of us was aboard.
Mission specialist Mike Gernhardt is a diver, the most experienced ever to soar into space.
A veteran of three previous shuttle missions, he was once a commercial diver and a resort instructor, and is a recognised authority on decompression theory, both in space and under water.
He has been diving since the age of eight. Its his passion, his profession - and was his non-traditional means of becoming an astronaut.

Gernhardts inspiration came on early fishing trips to Florida with his dad.
It caught me deep in my soul as a young kid. Diving was always my motivation and almost everything Ive done was connected with it.
He had read Cousteau in third grade, and made his first dives at Barbuda in the Caribbean. As soon as he turned 12, Gernhardt got certified and dived everywhere he could in his native Ohio, from stone quarries to Lake Erie.
It was in his high-school physics class that he became fascinated with the universe. I put the connection between diving and space together and decided I wanted to be an astronaut.
People told me to join the Air Force, but my love was the ocean and I wanted to take that path. I made decisions that wouldnt preclude me from being an astronaut but didnt just go out and get the conventional astronaut resumé.
Gernhardts professional diving resumé began at age 17, working during the summer as a divemaster at the Virgin Islands Diving School.
The owner, Marv Ellis, sent him through an instructor course.
After two summers of leading tourists on resort dives, Gernhardt was ready for new challenges. By this time he was majoring in physics at Vanderbilt University and had done an independent study on bubble dynamics, inspired by Dr Christian Lambertsens work.
Today bubble mechanics is accepted decompression theory, but at the time it was a pioneering concept.

In the summer of 1976, the 20-year-old sophomore applied to every commercial diving company in the Gulf of Mexico. Intrigued by his research, Jerry Evans of Santa Fe International offered Gernhardt a job as a tender if he could pass the written test. He had had no commercial training, but he aced it.
It was the start of a nine-year career in the oilfields, during summers until after graduation, when he went full-time.
Initially I was a clearwater diver, and not into welding and working in the mud. Then I got intrigued with the challenge and art of getting a construction dive done against limited bottom time and a lot of environmental stresses. As a commercial diver you learn tricks, how to cheat and make the dive as easy as you can. Why bust your butt if you dont have to Its hard enough anyhow. He would eventually adapt some of these techniques for use in space.

After graduation, Gernhardt joined Ocean Systems as an engineer, repairing oil platforms off the coast of Peru.
For three years, despite his parents reservations, he was a full-time diver. My mom isnt afraid about my going into space, but was scared all the time I did commercial diving, he says.
In 1980, Gernhardt entered graduate school at the University of Pennsylvania, studying under Lambertsen, who was also medical director of Ocean Systems. For 10 years he worked between the university and the field, developing and implementing a variety of decompression tables for commercial diving.
When Gernhardt discusses decompression theory, he becomes animated, leading the listener into a complex maze of technical theory and application at breakneck speed. At such times I keep my mouth shut, hoping that he doesnt realise how far I am lagging behind.
The bottom line is that these tables allowed more bottom time with shorter decompression and more safety. I learned a lot of stuff first-hand, saw a lot of bends and got a good sense for the different profiles, had the unique opportunity to directly integrate academics and operations and to work with Dr Lambertsen, says Gernhardt.
The tables they generated are used by Oceaneering (which bought Ocean Systems in 1983) to this day.

The company was grooming Gernhardt for an executive position, and agreed to pay him a retainer while he was in graduate school. Combined with a deans fellowship, this allowed amenities beyond the reach of a typical graduate student, including a nice apartment overlooking the river, and a Porsche.
Then it was back to work: in Mexico, South America, the North Sea and South-east Asia, mixed gas and saturation diving to as deep as 200m.
Oceaneering assigned Gernhardt to its advanced technical group in Houston, working on robotics and decompression. With Lambertsen, who continued to be a mentor, he developed new tables on contract for Britains Health Department.
But how does a diver become an astronaut By 29 Mike Gernhardt was a vice-president at Oceaneering, heading up special projects. He had applied to NASA after graduate school, but narrowly missing the interview stage convinced him that he needed a PhD.
He also convinced Oceaneerings president John Huff to form a space division of the company, aiming for NASA contracts. Gernhardt gathered a team of about 70 engineers.
I was the old man in this group. Most of the kids were 23, 24 and superstars. My job was to stimulate them with ideas; I gave them the ball. They worked on projects such as manipulators, umbilicals and cryogenic systems.
Gernhardt continued his studies of decompression theory, and earned his doctorate in 1991. He applied again for the astronaut corps and this time made the cut. It was tough to leave the company. I had this vision of commercial space, which is still my long-term goal.

At NASA, Mike continued to apply commercial diving techniques to space.
One innovation was a body restraint tether for spacewalks, which allowed astronauts to have both hands free. Some senior personnel said that it would never work, but Mike showed how they could save 100 hours on assembly sequences. Its now standard issue.
His current project involves leading a multi-centre team of decompression experts to develop improved decompression methods for spacewalks. Using a combination of heavy and mild exercise combined with oxygen prebreathing, his technique improves safety and cuts in half the time required for decompression before activity outside the spacecraft.
Gernhardt had done two spacewalks on his previous shuttle missions, and made three more on STS 104. His task was to attach the airlock module to the International Space Station. On the final walk, he and James Reilly became the first astronauts to undertake EVAs (extra-vehicular activities) from the airlock.

What is it like to walk in space Theres this tremendous sense of speed as you race by the Earth at 18,000mph. Were up 250 to 300 miles, and the relative motion is about the same as if you were doing a wing-walk on a supersonic jet.
Looking down at the Sea of Cortez, I punch some numbers into an electronic checklist. When I look down again Im over Florida.
On my first spacewalk we were riding on the robot arm high above the payload bay. Looking straight down, I had this sense of falling, but when I looked at the horizon and saw the curvature of the Earth, I knew I was just floating in space. We started at night, the lights were out, and Im seeing the stars like Ive never seen them before.
On Earth, sunrises and sunsets happen over about 30 minutes. Looking down the wing, I see a fine line of white light, and 10 seconds later a crescent like a moon, but its the blue Earth. About a minute later, this jewel-blue ocean is just staring me in the face.
Your whole life, you hear that the world is three-fourths water and you accept that intellectually. It takes getting up into space to see that. I feel very much in tune with the ocean; I understand its personality - I know how to work with it.
I remember going over the Tongue of the Ocean in the Bahamas and seeing where Id spent my teenage years, from the perspective of space. I was thinking about all the fish down there and synthesising these two worlds together.
I spent most of my life in the ocean and I understand that. Ive only spent a thousand hours or so in space and maybe thats not enough; maybe youve got to live up there for six months to really understand it.
Like any other environment you have to understand the parameters and how to work in it. I learned that from commercial diving, and thats helped me a lot with the spacewalks. For me, doing the first walks from the space station using the new decompression protocol is like the ultimate dive.
Looking back, its my love of the ocean that got me into diving, diving caught my interest in space, and commercial diving got me into working techniques on how to do this stuff. So this is the culmination of all those goals and desires, but it traces back to falling in love with the ocean at a young age.

Gernhardt stands on the arm of the space-shuttle to watch the progress of a hurricane in the Caribbean
Checking gear before a training session in NASAs Neutral Buoyancy Lab in Houston
Technicians help Mike Gernhardt get into the top of his spacesuit. His underwear has cooling tubes to prevent overheating.
The Neutral Buoyancy Lab is a gigantic pool in which astronauts can practise spacewalks.
The space-shuttle Atlantis rockets into the night at the start of one of Gernhardts missions