Orbital Spaceflight Quiz

Orbital Spaceflight: Key Facts and Figures

• An orbital spaceflight places a spacecraft on a trajectory where it could remain in space for at least one orbit.
• To remain in orbit around Earth requires an orbital speed of ~7.8 km/s and an altitude at perigee around 80 kilometers.
• The Fédération Aéronautique Internationale has established the Kármán line at an altitude of 100 km as a working definition for the boundary between aeronautics and astronautics.
• The lowest altitude at which an object in a circular orbit can complete at least one full revolution without propulsion is approximately 150 kilometers due to atmospheric drag.
• Orbital spaceflight is mostly used to distinguish from sub-orbital spaceflights, where the apogee of a spacecraft reaches space, but the perigee is too low.
• Orbital spaceflight from Earth has only been achieved by launch vehicles that use rocket engines for propulsion, requiring a delta-v of about 9.3–10 km/s.
• There are many proposed methods for achieving orbital spaceflight that have the potential of being much more affordable than rockets, such as the space elevator and rocket-assisted aircraft/spaceplanes.
• SpaceX has demonstrated significant progress in reducing the cost of orbital spaceflight through propulsive landing, reusable rocket booster stage, Dragon capsule, payload fairings, and 3D printing of rocket engines.
• An object in orbit at an altitude of less than roughly 200 km is considered unstable due to atmospheric drag, and 350 km is a more standard altitude for low Earth orbit.
• There are three main "bands" of orbit around the Earth: low Earth orbit (LEO), medium Earth orbit (MEO), and geostationary orbit (GEO).
• An orbital maneuver is the use of propulsion systems to change the orbit of a spacecraft.
• Returning spacecraft have to slow down as much as possible while still in higher atmospheric layers and avoid hitting the ground or burning up, with deceleration provided by retrofiring of rocket engines or atmospheric drag.