Amazon founder Jeff Bezos's space flight, scheduled for Wednesday NZ time, has been blasted by Oxfam as "human folly".
The Blue Origin billionaire is following Virgin Galactic's Richard Branson who, earlier this month, flew 80km above the earth's surface as a space tourist.
But the charity says the latest venture is not something that should be seen as a human achievement.
"We’ve now reached stratospheric inequality," Deepak Xavier, Oxfam International's global head of inequality campaign, said.
"Billionaires burning into space, away from a world of pandemic, climate change and starvation. Eleven people are likely now dying of hunger each minute while Bezos prepares for an 11-minute personal space flight.
Oxfam says global food prices have risen by 40 percent in the past year, contributing to 20 million more people having fallen into hunger and a six-fold increase in famine-like conditions.
"Bezos pays next to no US income tax but can spend US$7.5 billion on his own aerospace adventure," Xavier said.
"What we need is a fair tax system that allows more investment into ending hunger and poverty, into education and healthcare, and into saving the planet from the growing climate crisis - rather than leaving it,"
Bezos, who recently stepped down as Amazon CEO, has a net worth of around US$208 billion according to Forbes, up from US$113 billion in 2020.
And, on the eve of his flight aboard the New Shepard spaceship, he played down any sense of competition with Branson to be the first billionaire in space.
"This isn’t a competition, this is about building a road to space so that future generations can do incredible things in space," Bezos told NBC.
He will be joined on the flight by his brother Mark as well as 18-year-old Dutch student Oliver Daemen and 82-year-old aviation pioneer Wally Funk.
The latter two will become the youngest and oldest to fly into space.
Bezos has previously defended spending billions on the venture by telling Wired's 25th anniversary summit in 2018 that he wouldn't spend a minute of his life on something that wasn't contributing to civilisation and society.
That was in response to a question about whether his personal fortune would be better spent on dealing with societal issues such as poverty.
"You want risk-taking," he continued. "If you have a vision that everybody agrees with, you probably shouldn’t do it because someone else will do it first. All of the real needle-movers are driven by being right when most of the world is wrong."