https://www.dailymail.co.uk/sciencetech/article-10186369/The...
has some more info:
"A 10ft-long projectile was rapidly accelerated to thousands of miles an hour in a rotating arm before being released for launch 'in less than a millisecond'.
The first suborbital flight used about 20 per cent of the accelerator's full power capacity and reached a test altitude 'in the tens of thousands of feet,' Yaney said.
The vehicle used did not have a rocket engine onboard but SpinLaunch does plan to add one, as well as other internal systems, in future test flights.
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