Delta-v
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'''Delta-''v''''' (also known as "[[Delta (letter)#Upper case|change]] in [[velocity]]"), symbolized as and pronounced {{IPA|/dɛltə viː/}}, as used in [[flight dynamics (spacecraft)|spacecraft flight dynamics]], is a measure of the [[impulse (physics)|impulse]] per unit of spacecraft [[mass]] that is needed to perform a maneuver such as launching from or landing on a planet or moon, or an in-space [[orbital maneuver]]. It is a [[scalar (mathematics)|scalar]] that has the units of [[speed]]. As used in this context, it |
'''Delta-''v''''' (also known as "'''[[Delta (letter)#Upper case|change]] in [[velocity]]'''"), symbolized as and pronounced {{IPA|/dɛltə viː/}}, as used in [[flight dynamics (spacecraft)|spacecraft flight dynamics]], is a measure of the [[impulse (physics)|impulse]] per unit of spacecraft [[mass]] that is needed to perform a maneuver such as launching from or landing on a [[planet]] or [[Natural satellite|moon]], or an in-space [[orbital maneuver]]. It is a [[scalar (mathematics)|scalar]] that has the units of [[speed]]. As used in this context, it is not the same as the physical change in velocity of said spacecraft. |
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A simple example might be the case of a conventional rocket-propelled spacecraft, which achieves thrust by burning fuel. Such a spacecraft's delta-''v'', then, would be the change in velocity that spacecraft can achieve by burning its entire fuel load. |
A simple example might be the case of a conventional rocket-propelled spacecraft, which achieves thrust by burning fuel. Such a spacecraft's delta-''v'', then, would be the change in velocity that spacecraft can achieve by burning its entire fuel load. |
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===LEO reentry=== |
===LEO reentry=== |
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For example the Soyuz spacecraft makes a de-orbit from the ISS in two steps. First, it needs a delta-''v'' of 2.18 m/s for a safe separation from the space station. Then it needs another 128 m/s for [[Atmospheric entry|reentry]].{{cite web |last1=Gebhardt |first1=Chris |title=Soyuz MS-17 safely returns three Station crewmembers to Kazakhstan |url=https://www.nasaspaceflight.com/2021/04/soyuz-ms-17-landing/ |website=nasaspaceflight.com |date=17 April 2021 |access-date=10 July 2022}} |
For example, the [[Soyuz (spacecraft)|Soyuz spacecraft]] makes a de-orbit from the [[International Space Station|ISS]] in two steps. First, it needs a delta-''v'' of 2.18 m/s for a safe separation from the space station. Then it needs another 128 m/s for [[Atmospheric entry|reentry]].{{cite web |last1=Gebhardt |first1=Chris |title=Soyuz MS-17 safely returns three Station crewmembers to Kazakhstan |url=https://www.nasaspaceflight.com/2021/04/soyuz-ms-17-landing/ |website=nasaspaceflight.com |date=17 April 2021 |access-date=10 July 2022}} |
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==See also== |
==See also== |
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