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| Entry, Descent, and Landing | |
|---|---|
| Name | Entry, Descent, and Landing |
| Type | Spaceflight phase |
| First | V-2 rocket |
| Notable | Viking program, Apollo program, Mars Science Laboratory, Hayabusa2 |
Entry, Descent, and Landing Entry, Descent, and Landing is the phase of an atmospheric or surface approach in which a spacecraft transitions from spaceflight to surface contact, encompassing high-speed atmospheric entry, controlled aerobraking, parachute deployment, powered descent, and touchdown. It integrates engineering principles developed by programs such as Apollo program, Viking program, Mars Reconnaissance Orbiter, and Mars Science Laboratory and operational practices used by organizations including NASA, European Space Agency, Roscosmos, and JAXA to land payloads safely on bodies like Earth, Moon, Mars, and Venus.
The entry, descent, and landing sequence combines thermal protection strategies from projects like Apollo 11 and Space Shuttle Columbia with descent hardware exemplified by Curiosity (rover), Perseverance (rover), and Hayabusa2 to achieve surface access. Designing EDL draws on expertise from institutions such as Jet Propulsion Laboratory, Lockheed Martin, Blue Origin, and SpaceX and benefits from flight data obtained during missions like Viking 1, Mars Pathfinder, Phoenix (spacecraft), and Chang'e 4. Mission planning must reconcile constraints from launch providers like United Launch Alliance and scientific objectives of teams at Caltech, MIT, and European Southern Observatory.
Atmospheric entry physics is grounded in hypersonic aerothermodynamics developed during work by Hermann Oberth, Robert Goddard, and research programs at Langley Research Center. Key processes include shock-layer heating studied on Apollo 13, convective and radiative heat transfer examined for Venera 7 and Pioneer Venus missions, and stagnation-point ablation characterized in tests at Sandia National Laboratories. Aerodynamic stability ties to ballistic coefficient concepts used by Viking 2, lift-to-drag optimization seen in Space Shuttle Columbia, and trajectory shaping used in Mars Science Laboratory to manage deceleration, heating, and g-loads for crewed missions like Skylab and proposed Orion (spacecraft) returns.
Descent employs technologies ranging from traditional supersonic parachutes used on Apollo 11 and Curiosity (rover) to supersonic retropropulsion demonstrated by Falcon 9 booster landings and studied for Mars Sample Return and Starship. Aerodynamic decelerators include inflatable hypersonic decelerators tested on ILRV concepts and supersonic parachute trials by NASA and CNES. Airbags, used by Mars Pathfinder and Beagle 2, complement retro-rockets as in Lunar Module and Venera lander designs, while sky crane techniques were pioneered by Mars Science Laboratory and adapted for Perseverance (rover).
Landing systems range from passive to fully powered architectures: passive systems such as those on Genesis (spacecraft) and Huygens rely on aerodynamics and parachutes, whereas powered landers include Lunar Module, Chang'e 3, InSight (spacecraft), and commercial designs by Blue Origin and SpaceX. Structure and mass trade-offs reference work at NASA Ames Research Center, manufacturing by Northrop Grumman, and materials developed at MIT Lincoln Laboratory. Touchdown sensors and landing legs trace lineage to Viking program, iterative improvements in Phoenix (spacecraft), and prototype testing at facilities like Kennedy Space Center.
Guidance, navigation, and control for EDL leverage radar altimeters used on Voyager program flybys, inertial measurement units from GRACE heritage, star trackers used on Hubble Space Telescope, and terrain-relative navigation demonstrated by Mars 2020/Perseverance (rover). GN&C algorithms developed by teams at Jet Propulsion Laboratory, Aerospace Corporation, and ESA integrate data from Deep Space Network communications and autonomous hazard avoidance informed by Mars Reconnaissance Orbiter imagery and mapping efforts by USGS planetary cartography.
Risk management for EDL encompasses probabilistic risk assessment frameworks used after Challenger disaster and Columbia disaster, fault-tolerant avionics from Apollo program, and safety culture practices from NASA and Roscosmos. Mitigation strategies include redundant systems seen on Voyager program, flight termination protocols from Delta II heritage, contamination control mandated by COSPAR policies to protect Europa and Enceladus from forward contamination, and recovery operations developed for Apollo 11 and Soyuz TMA-1.
Notable EDL missions illustrate evolving approaches: Viking program achieved the first successful Martian landings, Apollo 11 proved crewed lunar EDL, Mars Pathfinder and Sojourner introduced airbag landings, Mars Exploration Rovers expanded surface mobility, Mars Science Laboratory used sky crane EDL for Curiosity (rover), Hayabusa and Hayabusa2 returned samples using unique touch-and-go profiles, Chang'e 4 performed the first far-side lunar landing, and InSight (spacecraft) executed precision touchdown for geophysical studies. Contemporary efforts like Mars 2020/Perseverance (rover), Starship, and Artemis program are advancing EDL methods for sample return and human exploration.