Retro tubes fly over the English countryside. (TV: The Android Invasion)
A retro tube was a capsule designed to transport its occupant from orbit to the ground. The Kraals used them to move their androids. The craft slowed before impact, allowing the occupant to survive.
Styggron fitted several retro tubes with androids as part of his invasion of Earth. The Fourth Doctor and Sarah Jane Smith used them to travel down to the planet's surface from the XK-5 space freighter being used by the Kraals. Android replicas of the Doctor and Sarah were transported to Earth in the same manner. (TV: The Android Invasion)
