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{{short description|Landing technique}} |
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{{Refimprove|date=August 2007}} |
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'''Lithobraking''' is a whimsical "[[Emergency landing|crash landing]]" euphemism used by spacecraft engineers to refer to a spacecraft impacting the surface of a planet or moon.<ref name=McDowell>McDowell, Jonathan (2020). [https://planet4589.org/space/gloss/glossary.pdf "Lithobraking"], ''Astronautical Glossary''. Retrieved May 16, 2022.</ref><ref name=etech20250430/><ref name=npr20150430/> The word was coined by analogy with "[[aerobraking]]", slowing a spacecraft by intersecting the [[atmosphere]], with "lithos" ({{lang-grc|[[wikt:λίθος#Ancient Greek|λίθος]]}} [{{transl|grc|líthos}}], "rock")<ref>{{cite web |url=https://www.dictionary.com/browse/litho- |title=litho |publisher=Dictionary.com}}</ref> substituted to indicate the spacecraft is intersecting the planet's solid [[lithosphere]] rather than merely its gaseous atmosphere. |
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According to [[Jonathan McDowell]],<ref name=McDowell/> "Lithobraking reduces the [[apoapsis]] height to zero instantly, but with the unfortunate side effect that the spacecraft does not survive. Originally a whimsical euphemism, but increasingly a standard term." |
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'''Lithobraking''' is a landing technique used by uncrewed space vehicles to safely reach the surface of a celestial body while reducing landing speed by impact with the body's surface. The word was probably coined as a whimsical adaptation of [[aerobraking]], which is the process of slowing a space vehicle by the use of [[Drag (physics)|aerodynamic drag]] in a [[planet]]'s [[celestial body atmosphere|atmosphere]]. ''Lithos'' is a [[Greek language|Greek]] word meaning "rock" or "stone," similarly used in the word [[Lithosphere|lithosphere]]. |
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== End-of-mission lithobraking == |
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[[Image:Pathfinder Air Bags - GPN-2000-000484.jpg|thumb|right|[[Mars Pathfinder]] lithobraking airbag test]] |
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| ⚫ | Lithobraking is used to refer to the result of a spacecraft crashing into the rocky surface of a body with no measures to ensure its survival, either by accident or with intent. For instance, the term has been used to describe the impact of ''[[MESSENGER]]'' into [[Mercury (planet)|Mercury]] after the spacecraft ran out of fuel.<ref name=etech20250430>{{cite web |url=http://www.extremetech.com/extreme/204672-nasas-messenger-probe-is-crashing-into-mercury-today |title=NASA's MESSENGER probe is crashing into Mercury today |publisher=Extreme Tech |date=April 30, 2015| access-date = September 13, 2020 |first=Ryan |last=Whitwam}}</ref><ref name=npr20150430>{{Cite news |first=Bill|last=Chappell| date=April 30, 2015 |title=Kill The Messenger: NASA Orbiter Crashes Into Mercury |work =NPR.org |access-date=September 13, 2020 |url=https://www.npr.org/sections/thetwo-way/2015/04/30/403279933/kill-the-messenger-nasa-orbiter-set-to-crash-into-mercury-thursday}}</ref> More recently, the term has also been used to describe the successful completion of the [[Double Asteroid Redirection Test|Double Asteroid Redirection Test (DART)]], when a probe crashed into [[Dimorphos]] to test lithobraking as a method of planetary defense.<ref>{{cite web |url=https://www.lpi.usra.edu/publications/newsletters/lpib/new/first-line-of-defense/ |title=First Line of Defense |website=Lunar and Planetary Institute |quote=... the live feed dropped out at the heartbreaking/lithobraking moment of impact ... |first=Lori S. |last=Glaze |author-link=Lori Glaze |date=October 2022 |access-date=November 17, 2022 |url-status=live |archive-url=https://web.archive.org/web/20221117060111/https://www.lpi.usra.edu/publications/newsletters/lpib/new/first-line-of-defense/ |archive-date=November 17, 2022}}</ref> |
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== Intact lithobraking == |
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Successful lithobraking requires either reducing the velocity of the lander prior to impact or protecting the probe with sufficient cushioning to withstand an impact with the surface undamaged. The velocity of a lander can be reduced using retrorockets or parachutes, and it can be protected from the force of impact by cushioning air bags or shock absorbers. The first successful lithobraking was achieved by the [[Soviet Union|Soviet]] [[Luna 9]] probe resulting in the first soft landing on the [[Moon]] using a combination of retrorockets and gas-filled cushioning bags.<ref>{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1966-006A|title=NASA-NSSDC-Spacecraft-Details|publisher=NASA|accessdate=September 13, 2020}}</ref> |
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Successful lithobraking requires a spacecraft capable of impacting the planet or moon at high velocity, or protecting the probe with sufficient cushioning to withstand an impact with the surface undamaged. Incoming angles are made shallow enough such that the impact has the characteristic of a glancing blow, rather than a direct impact on the surface. Lithobraking can be combined with other braking techniques, where the velocity of a lander can be reduced using retrorockets or parachutes, and it can be protected from the force of impact by cushioning air bags or shock absorbers.{{Citation needed|date=April 2023}} |
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| ⚫ | In the absence of a thick atmosphere, lithobraking is difficult due to the extremely high orbital velocities of most bodies. However, the orbital velocity of small moons (for example, Phobos), asteroids, and comets can be sufficiently small for this strategy to be feasible. For example, ''[[Rosetta (spacecraft)|Rosetta]]''{{'s}} lander, ''[[Philae (spacecraft)|Philae]]'', passively landed on the comet [[67P/Churyumov–Gerasimenko]] after separating from the orbiter, dissipating energy only through impact with the surface of the comet.<ref>{{Cite journal| doi = 10.1016/j.asr.2009.06.009| issn = 0273-1177| volume = 44| issue = 7| pages = 847–858| last1 = Ulamec| first1 = Stephan| last2 = Biele| first2 = Jens| title = Surface elements and landing strategies for small bodies missions – Philae and beyond| journal = Advances in Space Research| date = 2009| bibcode = 2009AdSpR..44..847U| url = https://linkinghub.elsevier.com/retrieve/pii/S0273117709003858}}</ref> The [[MASCOT]] lander from [[Hayabusa2]] landed on asteroid [[162173 Ryugu]] in a similar manner.<ref>{{Cite web| date = October 2, 2018| first = Elizabeth| last=Howell| title = Tiny German Spacecraft Poised for Hopping Landing on Asteroid Ryugu| work = Space.com| access-date = 2020-09-13| url = https://www.space.com/41996-mascot-prepares-for-asteroid-landing.html}}</ref> |
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When landing on bodies with an atmosphere, lithobraking can be combine with aerobraking instead of relying on retrorockets and air-bags. For bodies with a significant yet insufficiently thick atmosphere (e.g., [[Mars]]) all of these may be used together. The [[Mars Pathfinder]] and [[Mars Exploration Rover]] programs have used this approach successfully.<ref name=pathfinder>{{cite web |url=http://marsprogram.jpl.nasa.gov/MPF/mpf/edl/edl1.html |title=Entry Descent and Landing |work=JPL/NASA Mars Pathfinder |year=2005 |accessdate=September 12, 2020 |archive-url=https://web.archive.org/web/20120319230448/http://marsprogram.jpl.nasa.gov/MPF/mpf/edl/edl1.html |archive-date=March 19, 2012 |url-status=live }}</ref><ref name=mer>{{cite web|url=https://mars.nasa.gov/mer/mission/spacecraft_edl_airbags.html |title=Mars Exploration Rover Mission: The Mission |publisher=NASA |website=NASA.gov |accessdate=September 12, 2020}}</ref> The Russian [[Mars 96]] mission would have attempted a similar landing had it not been lost in earths atmosphere shortly after launch.<ref name=beyond_earth> {{cite book|url=https://www.nasa.gov/sites/default/files/atoms/files/beyond-earth-tagged.pdf|title=Beyond Earth: A Chronicle of Deep Space Exploration, 1958–2016|last1=Siddiqi |first1=Asif A.|lccn=2017059404|isbn=9781626830424|publisher=NASA History Program Office|edition=second|year=2018|id=SP2018-4041|series=The NASA history series|location=Washington, D.C.}}</ref>{{rp|193-194}} For bodies such as [[Venus]] with an exceptionally thick atmosphere, the combination of lithobraking and aerobraking can be sufficient. The Soviet [[Venera]] landers descended using parachutes high in the atmosphere before falling freely through the dense lower atmosphere until finally dissipating their remaining velocity (between approximately 7.5 and 8 [[m/s]]) on impact.<ref name=beyond_earth/>{{rp|150-157}} |
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| ⚫ | Instead of attempting to slowly dissipate the incoming velocity, it can be used to enable the probe to penetrate the surface. This can be tried on bodies with low gravitation, such as [[comet]]s and [[asteroid]]s, or on planets with atmospheres (by using only small parachutes, or no parachutes at all). Several such missions have been launched, including penetrators on the two [[Phobos program|Phobos probe landers]] targeted for Mars' moon [[Phobos (moon)|Phobos]] and ones for Mars itself on [[Mars 96]] and [[Deep Space 2]], but so far none have succeeded. The cancelled [[LUNAR-A]] probe would have carried penetrators to the [[Moon]].{{Citation needed|date=April 2023}} |
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| ⚫ |
In the absence of a thick atmosphere, lithobraking is difficult due to the extremely high orbital velocities of most bodies. However, the orbital velocity of small moons ( |
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===Related concepts=== |
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Instead of attempting to slowly dissipate the incoming velocity, it can be used to enable the probe to penetrate the surface. |
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| ⚫ | This can be tried on bodies with low gravitation, such as [[comet]]s and [[asteroid]]s, or on planets with atmospheres (by using only small parachutes, or no parachutes at all). Several such missions have been launched, including penetrators on the two [[Phobos program|Phobos probe landers]] targeted for Mars' moon [[Phobos (moon)|Phobos]] and ones for Mars itself on [[Mars 96]] and [[Deep Space 2]], but so far none have succeeded. The cancelled [[LUNAR-A]] probe would have carried penetrators to the [[Moon]]. |
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[[Kraft Ehricke]] had proposed the idea of a slide landing on the Moon, where a spacecraft's orbit is tangent to the lunar surface, and the spacecraft skids to a stop by sliding against the regolith. Related concepts involve the spacecraft in an orbit tangent to the surface of the body in question, and "docking" with a [[magnetic levitation|magnetically levitated]] (maglev) [[magnetic levitation train|train]], and the train then slowing.<ref>{{cite journal |url=http://adsabs.harvard.edu/full/1988LPICo.652...26B |title=Lunar Landing via a Linear Accelerator |author=Binder, A. B.|journal=Second Conference on Lunar Bases and Space Activities of the 21St Century |year=1988 |volume=652 |page=26 |bibcode=1988LPICo.652...26B }}</ref> This technique requires extremely precise guidance and control, in addition to a large infrastructure, and is thus not yet a viable option{{snd}}although it may be in the future.{{Citation needed|date=April 2023}} |
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Lithobraking is |
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==See also== |
==See also== |
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{{Portal| Spaceflight }} |
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[[Category:Spacecraft propulsion]] |
[[Category:Spacecraft propulsion]] |
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[[Category:21st-century neologisms]] |
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Lithobraking is a whimsical "crash landing" euphemism used by spacecraft engineers to refer to a spacecraft impacting the surface of a planet or moon.[1][2][3] The word was coined by analogy with "aerobraking", slowing a spacecraft by intersecting the atmosphere, with "lithos" (Ancient Greek: λίθος [líthos], "rock")[4] substituted to indicate the spacecraft is intersecting the planet's solid lithosphere rather than merely its gaseous atmosphere.
According to Jonathan McDowell,[1] "Lithobraking reduces the apoapsis height to zero instantly, but with the unfortunate side effect that the spacecraft does not survive. Originally a whimsical euphemism, but increasingly a standard term."
Lithobraking is used to refer to the result of a spacecraft crashing into the rocky surface of a body with no measures to ensure its survival, either by accident or with intent. For instance, the term has been used to describe the impact of MESSENGER into Mercury after the spacecraft ran out of fuel.[2][3] More recently, the term has also been used to describe the successful completion of the Double Asteroid Redirection Test (DART), when a probe crashed into Dimorphos to test lithobraking as a method of planetary defense.[5]
Successful lithobraking requires a spacecraft capable of impacting the planet or moon at high velocity, or protecting the probe with sufficient cushioning to withstand an impact with the surface undamaged. Incoming angles are made shallow enough such that the impact has the characteristic of a glancing blow, rather than a direct impact on the surface. Lithobraking can be combined with other braking techniques, where the velocity of a lander can be reduced using retrorockets or parachutes, and it can be protected from the force of impact by cushioning air bags or shock absorbers.[citation needed]
In the absence of a thick atmosphere, lithobraking is difficult due to the extremely high orbital velocities of most bodies. However, the orbital velocity of small moons (for example, Phobos), asteroids, and comets can be sufficiently small for this strategy to be feasible. For example, Rosetta's lander, Philae, passively landed on the comet 67P/Churyumov–Gerasimenko after separating from the orbiter, dissipating energy only through impact with the surface of the comet.[6] The MASCOT lander from Hayabusa2 landed on asteroid 162173 Ryugu in a similar manner.[7]
Instead of attempting to slowly dissipate the incoming velocity, it can be used to enable the probe to penetrate the surface. This can be tried on bodies with low gravitation, such as comets and asteroids, or on planets with atmospheres (by using only small parachutes, or no parachutes at all). Several such missions have been launched, including penetrators on the two Phobos probe landers targeted for Mars' moon Phobos and ones for Mars itself on Mars 96 and Deep Space 2, but so far none have succeeded. The cancelled LUNAR-A probe would have carried penetrators to the Moon.[citation needed]
Kraft Ehricke had proposed the idea of a slide landing on the Moon, where a spacecraft's orbit is tangent to the lunar surface, and the spacecraft skids to a stop by sliding against the regolith. Related concepts involve the spacecraft in an orbit tangent to the surface of the body in question, and "docking" with a magnetically levitated (maglev) train, and the train then slowing.[8] This technique requires extremely precise guidance and control, in addition to a large infrastructure, and is thus not yet a viable option – although it may be in the future.[citation needed]
... the live feed dropped out at the heartbreaking/lithobraking moment of impact ...
