Momentum and Kinetic energy are conserved in both elastic and inelastic collisions.
In an elastic collision, both momentum and kinetic energy are conserved. This means that the total momentum and the total kinetic energy of the objects involved in the collision will remain the same before and after the collision.
In an inelastic collision, while momentum is still conserved, kinetic energy is not. This means that the total momentum of the objects involved in the collision will remain the same, but the total kinetic energy will decrease. This decrease in kinetic energy is due to the conversion of some of the energy into other forms such as heat, sound, or deformation.
Explosions are a type of collision where both momentum and energy are not conserved, as the energy from the explosion is converted into other forms such as heat, light, sound, and kinetic energy of the fragments.
Spacecraft, as they move through space, can also conserve momentum, but it is dependent on the specific scenario and the interactions between the spacecraft and other objects such as other spacecraft, planets, or space debris.