But though her job as a chemist in the well-known chocolate factory had its rewards, it was interstellar only in name.
It was her next adventure, aboard Soyuz TM-12 en route to the Mir space station, that was to seal her place among the planetary pioneers. When she returned home to Sheffield, she was a global celebrity.
She has avoided the public spotlight in the years since, but on the 30th anniversary of her historic mission, code-named Project Juno, one of her colleagues in Yorkshire suggested that her name ought to be on the lips of more young people who aspired to follow her lead.
“If you ask someone to name a British astronaut today, they will more than likely think of Tim Peake,” said Professor Brad Gibson, director of the Milne Centre for Astrophysics at Hull University. “I think it’s important to continually remind people of the pioneering role that Helen played.
“We sometimes lose sight of the fact that she was the first – the one who paved the way for the other UK and European astronauts. We should celebrate that and keep it in the consciousness of the British public.”
It was in 1989 that Ms Sharman answered an advertisement she heard on her car radio. Astronaut wanted – no experience necessary, it said.
She was eventually selected from more than 13,000 applicants, and spent the next 18 months training at Star City, the Soviet showpiece facility in Star City, 18 miles north-east of Moscow.
At 1.50pm British time on May 18 1991 – a couple of weeks before her 27th birthday – she and her fellow cosmonauts, Anatoly Artebartsky and Sergei Krikalyov, were aboard the Soyuz capsule as it made a textbook launch from the Baikonur cosmodrome in the republic of Kazakhstan.
She carried with her a photograph of the Queen and a “space passport” in case she was forced to land outside the Soviet Union. Half a mile away, her parents and sister watched from a viewing platform.
During her week on board the space station, she conducted a raft of medical and agricultural experiments, and Professor Gibson said it was her commitment to science that marked out her contribution.
In a rare interview three years ago, she told The Yorkshire Post that her ambition was to “make this country embrace science and engineering in a way that many other countries already do”.
Ms Sharman, who now works in the Department of Chemistry at Imperial College London, added: “Science is not just necessary – it’s something that’s going to improve our lives and it should be interesting to discuss, rather than just a part of industry or something we have to learn at school. It’s really part of part of our culture in the same way as music, the arts and the theatre.”
Professor Gibson, who collaborated with her at the British Science Festival in Hull, said her influence was broader than simply having been the first in her field.
“It’s a cool thing to be able to say, but her bigger legacy has been her commitment to training the next generation and never losing sight of her background as an academic,” he said.
Erin McNeill, outreach officer, at Leeds University’s School of Physics, said Ms Sharman was an inspiration for future physicists.
“If you can see it you can be it,” she said. “Having someone who looks like you as a role model is really important.
“And it was wonderful to see her name back in the spotlight when Tim Peake went into space in 2015. Helen had done it all 25 years before.”
Britain did not have a spaceflight programme in the 1990s, but a private consortium was formed to raise money to pay the Soviet Union for a seat on one of its Soyuz missions. A Japanese journalist had previously flown under a similar arrangement.
It was the UK’s later involvement in the European Space Agency that eventually to Major Tim Peake becoming the second British astronaut, in 2015.
“The application process would have been very different by then,” said Professor Gibson.
To date, only 554 other people have gone into space.
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