How do spacecraft use an orbit to move from planet to planet?
Any spacecraft sitting on a launch pad on Earth is already in orbit around the Sun because the Earth is orbiting around the Sun. We can put a spacecraft in orbit so it goes around the Sun the same way. From that point, the spacecraft can have its speed adjusted to change its orbit around the Sun. Those adjustments can take a craft to Mars or to Venus from Earth. This is called a Hohmann Transfer Orbit, or a least energy orbit, because this is the easiest way to send spacecraft between planets. Basically, a spacecraft in a Hohmann Transfer Orbit is put into an irregular orbit around the Sun, with one part that is “lower” or closer to the Sun than the other. When a spacecraft is going to Mars, the spacecraft’s perihelion (section closest to the Sun) will be Earth’s orbit, and the aphelion (farthest distance from the Sun) will intercept the orbit of Mars at a single point. The spacecraft will change its orbit by speeding up with its thrusters. Spacecraft can go to Venus in the opposite wa
