Sarah Brightman has been working with her former husband Andrew Lloyd Webber on a song she can perform in space.
The British soprano, who is training at Star City near Moscow, is due to blast off on a Russian Soyuz craft on 1 September.
The 54-year-old will spend 10 days aboard the International Space Station (ISS), 260 miles (420 km) above Earth.
Brightman said singing in space was a “very different” proposition to performing on Earth.
Speaking at a press conference in central London, the Phantom of the Opera star said her team were trying to work out the technical details of performing on the ISS.
“I would like to connect with a choir, or children or another singer or an orchestra on Earth,” she told reporters.
Brightman said she had been working with Lord Lloyd-Webber to find a song that “suits the idea of space”.
She recorded the song in New York last week and it will appear on a retrospective of her career, out later this year.
“To sing in microgravity is a very different thing to singing down here,” she said. “We use the Earth to ground ourselves when we sing and the air around us.
“This is going to be very different. I’m trying to find a piece that is beautiful and simple in its message, as well as not complicated to sing.”
She didn’t want to “promise too much”, she went on, because of the complexity of the idea.
In 2013, Canadian astronaut Chris Hadfield’s rendition of David Bowie’s Space Oddity from the ISS become a huge YouTube hit.
Brightman is thought to be paying around £34m ($51m) to become the eighth space tourist. She said she had paid for the trip herself, but could not “contractually” say how much it had cost.
She will be part of a three-person crew travelling to the ISS. The last space tourist to make the trip was Cirque du Soleil founder Guy Laliberte in 2009.
Brightman said the Moon landing in 1969 – which she watched as a nine-year old – had been “a pivotal moment” in her life.
She joked that while in space she might “do some of the movements” from 1978 chart hit I Lost My Heart to a Starship Trooper.
The track was performed on Top of the Pops by dance troupe Hot Gossip, with whom Brightman began her career.
‘Laughter and tears’
In the 1980s, Brightman starred on the West End stage in Cats and The Phantom of the Opera. Both were penned by Andrew Lloyd Webber, whom she married in 1984.
The pair divorced in 1990 and Brightman embarked on a solo singing career.
The singer helped popularise the classical crossover genre, scoring a worldwide hit with her duet with Italian tenor Andrea Bocelli, Time To Say Goodbye.
Brightman began Tuesday’s press conference by saying she had talked to many people who have travelled in space.
“They have all said it is indescribable. You feel a mixture of laughter and tears. You feel humble but you can see the bigger picture.
“It’s been an unusual path that has taken me to this point and it hasn’t been an easy journey. I’ve found out a lot about myself.”
The singer has also spent time training at Star City with Tim Peake, who will become the first “official” British astronaut when he goes to the ISS at the end of 2015.