But depending on the weight of the rocket, an extra boost may be needed to get off Earth. In these cases, solid propellent, usually aluminum, is combined with an explosive, such as ammonium perchlorate, to propel the rocket all the way into space.
But that’s just the start of the journey for a spacecraft. For minor course corrections, small thrusters attached to the craft fire off small puffs of gas, such as hydrogen peroxide. Scientists can also plan for gravitational assists from nearby planets for an extra boost as the craft travels to the far reaches of our solar system.
Spacecrafts also need a reliable supply of electricity to report back their findings. Crafts operating close to the Sun can reliably use solar panels. But as a probe moves further out in the solar system, the Sun’s rays become too weak. In that case, it can use radioisotope thermoelectric generators, which is a fancy way to say nuclear batteries. As radioactive material decays, it releases heat that can be converted into electricity for the craft.