Reusable rocket stage

A method of guiding a rocket stage of a multistage space launch vehicle back to earth for reuse, wherein the rocket stage provides thrust with a main engine for liftoff of the space launch vehicle from the surface of the earth and wherein the rocket stage is separated from remaining parts of the space launch vehicle during ascent after the liftoff such that the space launch vehicle continues towards space and the rocket stage returns to the surface of the earth, the method comprising:

• initiating, via a control unit, an inflation of an inflatable hull connected to the rocket stage when a predefined condition after stage separation is fulfilled such that the hull is receiving and retaining lifting gas from a pressure tank attached to the rocket stage for increasing the volume of the hull with the lifting gas to generate aerostatic lift;
• and
• controlling, via the control unit, a propulsion and steering unit to maneuver the rocket stage to a specified landing site on the surface of the earth in a descent, wherein the propulsion and steering unit provides thrust and attitude control while the hull is at least partially inflated and wherein the hull is at least partially filled with the lifting gas during the descent, wherein the rocket stage is in a horizontal attitude while suspended below the inflated hull during a phase of descent, wherein the hull that is fully inflated has the shape of a blimp-airship comprising aerodynamically stabilizing tail fins, wherein the rocket stage comprises a deceleration system configured to decrease velocity of the rocket stage with respect to the earth, and wherein the control unit is further configured to start activation of the deceleration system during or after the stage separation and before the inflation of the hull.

A rocket stage for a multistage space launch vehicle, wherein the rocket stage comprises a main engine to provide thrust for liftoff of the space launch vehicle from the surface of the earth and wherein the rocket stage is configured for stage separation from remaining parts of the space launch vehicle during ascent after the liftoff such that the space launch vehicle continues towards space and the rocket stage returns to the surface of the earth, the rocket stage comprising:

• an inflatable hull configured to receive and retain lifting gas from a pressure tank attached to the rocket stage;
• an inflation unit configured to perform inflation of the hull with the lifting gas;
• a propulsion and steering unit configured to provide thrust and attitude control for the rocket stage while the hull is at least partially inflated;
• and
• a control unit configured to control the inflation unit and the propulsion and steering unit, wherein the control unit is configured to:
• initiate the inflation of the hull by controlling the inflation unit when a predefined condition after the stage separation is fulfilled, the inflation increasing a volume of the hull by filling the hull with the lifting gas to generate aerostatic lift;
• and
• control the propulsion and steering unit to maneuver the rocket stage in a descent to a specified landing site on the surface of the earth while the hull is at least partially filled with the lifting gas during the descent;
• wherein the rocket stage comprises a deceleration system configured to decrease velocity of the rocket stage with respect to the earth, and wherein the control unit is further configured to start activation of the deceleration system during or after the stage separation and before the inflation of the hull;
• wherein the deceleration system comprises a device configured to generate aerodynamic drag;
• wherein the device configured to generate the aerodynamic drag is a parachute;
• and
• wherein the parachute is attached to the rocket stage at a movable attachment point, the attachment point being movable along a longitudinal axis of the rocket stage.