![]() ![]() Various advanced technologies have been developed to enable atmospheric reentry and flight at extreme velocities. Most objects enter at hypersonic speeds due to their sub-orbital (e.g., intercontinental ballistic missile reentry vehicles), orbital (e.g., the Soyuz), or unbounded (e.g., meteors) trajectories. Meteors are also often travelling quite fast relative to the Earth simply because their own orbital path is different from that of the Earth before they encounter Earth's gravity well. Uncontrolled objects reach high velocities while accelerating through space toward the Earth under the influence of Earth's gravity, and are slowed by friction upon encountering Earth's atmosphere. Furthermore, slow-speed returns to Earth from near-space such as high-altitude parachute jumps from balloons do not require heat shielding because the gravitational acceleration of an object starting at relative rest from within the atmosphere itself (or not far above it) cannot create enough velocity to cause significant atmospheric heating.įor Earth, atmospheric entry occurs by convention at the Kármán line at an altitude of 100 km (62 miles 54 nautical miles) above the surface, while at Venus atmospheric entry occurs at 250 km (160 mi 130 nmi) and at Mars atmospheric entry at about 80 km (50 mi 43 nmi). Such vehicles have high kinetic energies and atmospheric dissipation is the only way of expending this, as it is highly impractical to use retrorockets for the entire reentry procedure.īallistic warheads and expendable vehicles do not require slowing at reentry, and in fact, are made streamlined so as to maintain their speed. ![]() Crewed space vehicles must be slowed to subsonic speeds before parachutes or air brakes may be deployed. Reentry has been achieved with speeds ranging from 7.8 km/s for low Earth orbit to around 12.5 km/s for the Stardust probe. These forces can cause loss of mass ( ablation) or even complete disintegration of smaller objects, and objects with lower compressive strength can explode. Objects entering an atmosphere experience atmospheric drag, which puts mechanical stress on the object, and aerodynamic heating-caused mostly by compression of the air in front of the object, but also by drag. Technologies and procedures allowing the controlled atmospheric entry, descent, and landing of spacecraft are collectively termed as EDL.Īnimated illustration of different phases as a meteoroid enters the Earth's atmosphere to become visible as a meteor and land as a meteorite There are two main types of atmospheric entry: uncontrolled entry, such as the entry of astronomical objects, space debris, or bolides and controlled entry (or reentry) of a spacecraft capable of being navigated or following a predetermined course. Mars Exploration Rover (MER) aeroshell, artistic renditionĪtmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. For other uses, see reentry (disambiguation), hiad (disambiguation), and irve (disambiguation). ![]() "Reentry", "HIAD", and "IRVE" redirect here. ![]()
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