Another way to get a spacecraft to 550AU would be to use solar sails and ground based lasers.

You have a small spacecraft (USB memory stick sized). Do a sub-orbital launch to get it out of the atmosphere. Then deploy the solar sails and fire ground based lasers at the craft to accelerate it. IIRC the theoretical maximum acceleration gets a you to 550AU in a few months.

https://www.space.com/laser-propelled-spaceships-solar-syste...