London: R&B star Rihanna has reportedly got herself on the waiting list for mega-expensive space flight, following fellow celebrities Justin Bieber, Paris Hilton and Brad Pitt. The 'Umbrella' hitmaker is expected to splash out 500k pounds for three seats on Richard Branson's Virgin Galactic, for her brother Rorrey, 23, and a bodyguard on the mission, reported Daily Star. "Rihanna has already put down a deposit for the flight. She has been obsessed with space since she was a child so it would be a dream come true for her," a source said. Rihanna's rapper-DJ brother told last month about their obsession with aliens. "She believes there are UFOs. No-one knows for sure, but Rihanna and I think they're out there," he had said.