Sussex astronaut Tim Peake shared a private moment with family members from behind glass at Building 252 earlier this morning, where they wished him farewell as he sat in his pressure suit.
The three space-suited astronauts then left to deliver the traditional salute to Cosmodrome officials and boarded the bus to the launch pad.
Smiling broadly, Major Peake waved to his sons from inside the bus, and gave them the thumbs up.
He has also been sent a message of encouragement from a fellow Rocket Man - albeit a slightly different one.
Elton John, who released the track Rocket Man in 1972, said on Twitter: “From one Rocket Man to another, good luck @astro_timpeake with your launch and mission!”
Watching the build-up to the launch from the Science Museum in London were Professor Brian Cox and comedian Dara O’Briain.
Mr O’Briain told BBC Breakfast: “It’s always part of the mission, to inspire the next generation and we’ll have hundreds, I think a couple of thousands of school kids in the Science Museum with us when the launch occurs.
“It’s a man sitting on top of a giant firework, being fired into space. The very moment of launch, I’ve been to one myself, is incredible - there’s a kinetic oomph of that rocket taking off as it punches is way out of the Earth’s gravity.
“It’s always a spectacular sight.”
Professor Cox added: “If just one or two of the school children here decide to be engineers or scientists or test pilots as a result of this mission, then it’s going to be worth it.”
After the Russian Soyuz rocket takes off and reaches orbit in less than 10 minutes, the crew will travel for six hours before reaching the ISS.
The space station goes around the Earth at 17,500mph (28,164kph) at an average altitude of 220 miles (354km).
But Professor Brian Cox warned that if the launch is miscalculated slightly, it could take about two days to dock.
Upon arrival, Major Peake and his crew will spend six months performing a variety of experiments and tests for researchers.
Among them will be a UK-designed test to check for problems suffered by astronauts - including visual complications and sickness - caused by increased brain pressure.
In total, he is expected to take part in 265 experiments.
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