Gravity can speed spacecraft — or slow them
Spacecraft can use planetary gravity assists to change speed while saving fuel. The Voyager probes accelerated during outer-planet flybys, while the Parker Solar Probe decelerated after flying by Venus.
Spacecraft can use planetary gravity assists to change speed while saving fuel. The Voyager probes accelerated during outer-planet flybys, while the Parker Solar Probe decelerated after flying by Venus.