The scenario you've described, where a protoplanet collides with Uranus two times, would have significant and unpredictable effects on Uranus. The exact outcome would depend on various factors such as the mass, velocity, and angle of impact of the protoplanet, as well as the specific dynamics of the collisions.
However, it's important to note that Uranus is a gas giant planet composed mostly of hydrogen and helium, with a small rocky core. If a protoplanet were to collide with Uranus, it would likely have a disruptive impact on the planet's structure and potentially alter its gravitational field and axial tilt.
The collisions could lead to the redistribution of mass within Uranus, affecting its overall gravitational field. If significant mass were added or redistributed in certain regions, it could potentially alter the gravitational forces experienced by nearby objects.
As for Uranus' axial tilt, it is already quite peculiar compared to other planets in the solar system. Uranus has an extreme axial tilt of approximately 98 degrees, which means its rotational axis is almost parallel to its orbital plane. This gives rise to extreme seasons on Uranus, where one pole faces the Sun while the other experiences extended periods of darkness.
If multiple collisions were to occur, especially in a specific manner, it could potentially perturb Uranus' axial tilt even further. The resulting interactions between the colliding protoplanet and Uranus could induce chaotic changes in its rotational dynamics.
However, it's important to remember that these scenarios involve complex astrophysical processes, and making precise predictions about the exact outcomes would require detailed simulations and knowledge beyond our current understanding.