Wannabe astro-physicist Charlotte Jones-Todd touched down at NASA's Johnson Space Centre in Houston, Texas, one day before the Discovery space shuttle and her seven-person crew blasted into orbit.
She was one of 30 outstanding young scientists worldwide to be selected to help astro-physicists design a shuttle capable of transporting people to Mars.
Her first mission was to watch Discovery's lift-off, however. And even though Charlotte stayed at ground control, she communicated with the astronauts tens of thousands of miles away via her teacher's email.
Charlotte, 16, a GCSE pupil at Tregaron secondary, Ceredigion, went on the mission with physics teacher Chris Greenfield, a part-time lecturer at Houston's international space school.
He said: "It was a thrilling trip - and even more so because we were closely watching the progress of Discovery and its crew."
Charlotte said her experience was "amazing" - the highlight being the safe return of the Discovery.
She said: "I would love to work in research or in the Houston resource centre, but I don't think I'm brave enough to go into space. I experienced what it would be like and it was very, very odd. We were all crossing our fingers for the safe return of the shuttle and every student cheered when it landed."
Charlotte even received an email from the Discovery crew: "It was surreal - an email from space landed in my inbox."
While in Houston, Charlotte cooked some Welsh cakes for fellow students.
She said: "I taught them how to say 'Bore da' ('Good morning') and they all know a lot more about Wales now."
Discovery blasted off on July 26, and was the first such mission since the Columbia disaster in 2003. Columbia broke up on re-entry, with the loss of all seven crew, because heat-protection tiles were damaged on take-off by insulation falling from a fuel tank.
Fears of a repeat performance were raised after insulation fell off Discovery's fuel tank on lift-off. Three space walks were carried out, including one in which ceramic fibre strips had to be removed from the outer casing.
The shuttle returned safely on August 9 after a 5.8million-mile journey that lasted 14 days.
Mr Greenfield said: "There was a really relaxed atmosphere out there, despite the worries over part of the shuttle falling off. I can honestly say this was a trip of a lifetime for Charlotte, and I have nicknamed the mission a voyage of discovery for all the aspiring astro-physicists taking part."
Charlotte had to write an essay and take part in an interactive exercise to test her scientific abilities before she was selected.
Mr Greenfield said: "I think Charlotte might have a career in astro-physics already mapped out, but she's only young and a lot can change."