Spaceplane

A spaceplane is a vehicle that can fly and glide as an aircraft in Earth's atmosphere and function as a spacecraft in outer space. To do so, spaceplanes must incorporate features of both aircraft and spacecraft. Orbital spaceplanes tend to be more similar to conventional spacecraft, while sub-orbital spaceplanes tend to be more similar to fixed-wing aircraft. All spaceplanes as of 2024 have been rocket-powered for takeoff and climb, but have then landed as unpowered gliders.

Four examples of spaceplanes have successfully launched to orbit, reentered Earth's atmosphere, and landed: the U.S. Space Shuttle, Russian Buran, U.S. X-37, and the Chinese Shenlong. Another, Dream Chaser, is under development in the U.S. As of 2024 all past and current orbital spaceplanes launch vertically; some are carried as a payload in a conventional fairing, while the Space Shuttle used its own engines with the assistance of boosters and an external tank. Orbital spaceflight takes place at high velocities, with orbital kinetic energies typically greater than suborbital trajectories. This kinetic energy is shed as heat during re-entry. Many more spaceplanes have been proposed.

At least two suborbital rocket-powered aircraft have been launched horizontally into sub-orbital spaceflight from an airborne carrier aircraft before rocketing beyond the Kármán line: the X-15 and SpaceShipOne.

Spaceplanes must operate in space, like traditional spacecraft, but also must be capable of atmospheric flight, like an aircraft.

Spaceplanes do not necessarily have to fly by their own propulsion, but instead often glide with their inertia while using aerodynamic surfaces to maneuver in the atmosphere during descent and landing. The U.S. Space Shuttle for instance, could not fly under its own propulsion but used its momentum after de-orbit to glide to the runway destination.

These requirements drive up the complexity, risk, dry mass, and cost of spaceplane designs. The following sections will draw heavily on the US Space Shuttle as the biggest, most complex, most expensive, most flown, and only crewed orbital spaceplane, but other designs have been successfully flown.

The flight trajectory required to reach orbit results in significant aerodynamic loads, vibrations, and accelerations, all of which have to be withstood by the vehicle structure.

If the launch vehicle suffers a catastrophic malfunction, a conventional capsule spacecraft is propelled to safety by a launch escape system. The Space Shuttle was far too big and heavy for this approach to be viable, resulting in a number of abort modes that may or may not have been survivable. The Challenger disaster demonstrated a lack of survivability on ascent.^{[citation needed]}