When Hubble swings from one galaxy to another, engineers fire no thrusters—Hubble has none. They change the speeds of four internal reaction wheels, making the observatory rotate the opposite way, while magnetic bars push against Earth’s field to bleed off excess momentum: a propellant-free steering system used since 1990.
When the Hubble Space Telescope finishes observing one galaxy and turns toward another, nothing fires into space. There…
