Good question! I assume that the weight of the launch vehicle is relatively small compared to the weight of the spinning apparatus so there's no big imbalance upon launch.
From the SpinLaunch FAQ: Does the launch create a sonic boom? Yes. However, it does not have a higher sonic impact than a traditional rocket lifting off. During launch, a short duration sonic boom is projected outwards and upwards along the trajectory of the launch vehicle. SpinLaunch uses industry standard methodologies to evaluate and comply with the Federal Aviation Administration’s requirements for noise profile analysis the same as traditional rocket launches.
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Does the launch create a sonic boom?
Yes. However, it does not have a higher sonic impact than a traditional rocket lifting off. During launch, a short duration sonic boom is projected outwards and upwards along the trajectory of the launch vehicle. SpinLaunch uses industry standard methodologies to evaluate and comply with the Federal Aviation Administration’s requirements for noise profile analysis the same as traditional rocket launches.