US Patent 10246186 Unmanned aerial vehicle with inflatable membrane

This disclosure describes an unmanned aerial vehicle (“UAV”) including an inflatable membrane (e.g., a balloon) and a compressed gas chamber containing a gas (e.g., helium, hydrogen, etc.) for inflating the membrane. When the UAV is approaching or departing from a location where noise reduction is desirable (e.g., a delivery location), the membrane may be inflated so as to increase the buoyancy of the UAV and allow the propulsion system (e.g., utilizing propellers, etc.) to be operated with less thrust and correspondingly with less noise. Once the UAV has departed and reached a certain distance from the location, the membrane may be deflated and retracted back into a storage area of the UAV.