In the Pegasus galaxy, some Stargates have been placed in space in orbit of planets, rather than on their surfaces. Rather than using a connected DHD, space-based gates are powered by three power nodes, and dialing is accessed by a panel on a ship. Puddle jumpers and Wraith Darts are both equipped with such DHDs, and are among the few ships capable of going through the Stargate. (SGA: "Rising")
The power nodes also contain some kind of stabilizers to keep the gate orbiting the planet, in case it is knocked out of position. They most likely recharge on the residual power of an incoming wormhole. (SGA: "Ghost in the Machine")
A Spacegate powered by three power nodes