EDL (rocketry) | Wikipedia audio article
Channel: wikipedia tts
Date: 02/06/2019

This is an audio version of the Wikipedia Article:
https://en.wikipedia.org/wiki/Atmospheric_entry


00:03:58 1 History
00:07:01 2 Terminology, definitions, and jargon
00:07:55 3 Entry vehicle shapes
00:08:10 3.1 Sphere or spherical section
00:10:50 3.2 Sphere-cone
00:14:15 3.3 Biconic
00:16:37 3.4 Non-axisymmetric shapes
00:18:23 4 Reentry heating
00:19:40 4.1 Shock layer gas physics
00:20:13 4.1.1 Perfect gas model
00:21:26 4.1.2 Real (equilibrium) gas model
00:27:29 4.1.3 Real (non-equilibrium) gas model
00:32:36 4.1.4 Frozen gas model
00:34:40 5 Thermal protection systems
00:35:17 5.1 Ablative
00:38:21 5.1.1 Super light-weight ablator
00:40:03 5.1.2 Phenolic-impregnated carbon ablator
00:41:47 5.1.2.1 PICA-X
00:42:53 5.1.3 SIRCA
00:44:30 5.1.4 AVCOAT
00:45:10 5.2 Thermal soak
00:46:16 5.3 Passively cooled
00:51:41 5.4 Actively cooled
00:53:14 6 Feathered reentry
00:56:15 7 Inflatable heat shield reentry
00:57:36 7.1 NASA IRVE
00:58:53 7.2 NASA HIAD
00:59:46 8 Entry vehicle design considerations
01:05:01 9 Notable atmospheric entry accidents
01:07:38 10 Uncontrolled and unprotected reentries
01:11:00 10.1 Deorbit disposal
01:13:28 11 Successful atmospheric reentries from orbital velocities
01:14:29 12 Selected atmospheric reentries
01:14:49 13 See also
01:14:58 14 Further reading
01:17:37 15 Notes and references
01:17:47 16 External links



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SUMMARY
=======
Atmospheric 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. 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. Technologies and procedures allowing the controlled atmospheric entry, descent, and landing of spacecraft are collectively termed as EDL.

Atmospheric drag and aerodynamic heating can cause atmospheric breakup capable of completely disintegrating smaller objects. These forces may cause objects with lower compressive strength to explode.
Crewed space vehicles must be slowed to subsonic speeds before parachutes or air brakes may be deployed. Such vehicles have kinetic energies typically between 50 and 1,800 megajoules, and atmospheric dissipation is the only way of expending the kinetic energy. The amount of rocket fuel required to slow the vehicle would be nearly equal to the amount used to accelerate it initially, and it is thus highly impractical to use retro rockets for the entire Earth reentry procedure. While the high temperature generated at the surface of the heat shield is due to adiabatic compression, the vehicle's kinetic energy is ultimately lost to gas friction (viscosity) after the vehicle has passed by. Other smaller energy losses include black-body radiation directly from the hot gases and chemical reactions between ionized gases.
Ballistic warheads and expendable vehicles do not require slowing at reentry, and in fact, are made streamlined so as to maintain their speed. Furthermore, slow-speed returns to Earth from near-space such as 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.
For Earth, atmospheric entry occurs at the Kármán line at an altitude of 100 km (62.14 mi / ~ 54 nautical mi) above the surface, while at Venus atmospheric entry occurs at 250 km (155.3 mi / ~135 nautical mi) and at Mars atmospheric entry at about 80 km (50 mi / ~ 43.2 nautical mi). Uncontrolled, objects reach high velocities while accelerating through space toward the Earth under the influence of Earth's gravity, and are slo ...