lighter-than-air vehicles - Defense Innovation Marketplace

Appendix B – Glossary of TermsAAerostat: A tethered, unmanned airship.Airlift: The transportation of people, equipment, or other cargo by air.Airship: An aircraft that obtains buoyant lift from a contained volume of helium or other gasthat is less dense than the surrounding air.CConventional Aircraft: An aircraft that does not rely on buoyant lift to achieve flight. Thisrefers to heavier-than-air (HTA) aircraft such as fixed-wing aircraft, tilt-rotor aircraft, andhelicopters.Conventional Airship: An airship that uses only buoyant lift to achieve flight.EEnvelope: The external structure of an airship within which the helium or other buoyant gas islocated. There are three categories of envelopes: rigid, semi-rigid and non-rigid. Rigid envelopesuse an internal frame to keep their shape. Semi-rigid envelopes use a “keel” along the bottom ofthe envelope to distribute weight. Non-rigid envelopes have no frame and use only gas andenvelope design to keep their shape.HHybrid Airship: An airship that uses a combination of buoyant lift from helium, aerodynamiclift from the shape of the envelope, and variable-direction thrust (more commonly calledvectored thrust) to stay aloft.IIntelligence, Surveillance, and Reconnaissance (ISR): Reconnaissance operations observe anarea to collect information. Surveillance is the systematic observation of a particular area.Intelligence is the product of surveillance and reconnaissance once the information from thoseoperations has been analyzed and evaluated.SStrategic airlift: The use of aircraft to transport materiel, weaponry, or personnel weighing 50–100 tons over long distances, e.g., between theaters of operations.TTactical airlift: The use of aircraft to transport materiel, weaponry, or personnel weighing 20–30 tons within a theater of operations.B-1