Editing Hypersonic speed (section)

== Classification of Mach regimes ==
Although "subsonic" and "supersonic" usually refer to speeds below and above the local [[speed of sound]] respectively, aerodynamicists often use these terms to refer to particular ranges of Mach values. When an aircraft approaches [[transonic]] speeds (around [[Mach number|Mach]] 1), it enters a special regime. The usual approximations based on the [[Navier–Stokes equations]], which work well for subsonic designs, start to break down because, even in the freestream, some parts of the flow locally exceed Mach 1. So, more sophisticated methods are needed to handle this complex behavior.<ref>{{Cite web |title=Hypersonics |doi=10.1007/978-3-030-60777-7_6 |url=https://link.springer.com/chapter/10.1007/978-3-030-60777-7_6}}</ref>

The "supersonic regime" usually refers to the set of Mach numbers for which linearised theory may be used; for example, where the ([[air]]) flow is not chemically reacting and where [[heat transfer]] between air and vehicle may be reasonably neglected in calculations. Generally, [[NASA]] defines "high" hypersonic as any Mach number from 10 to 25, and re-entry speeds as anything greater than Mach 25. Among the spacecraft operating in these regimes are returning [[Soyuz (spacecraft)|Soyuz]] and [[SpaceX Dragon|Dragon]] [[space capsule]]s; the previously-operated [[Space Shuttle]]; various reusable spacecraft in development such as [[SpaceX]] [[SpaceX Starship|Starship]] and [[Rocket Lab]] [[Electron (rocket)|Electron]]; and (theoretical) [[spaceplane]]s.{{cn|date=October 2014}}

In the following table, the "regimes" or "ranges of Mach values" are referenced instead of the usual meanings of "subsonic" and "supersonic".{{cn|date=October 2014}}

{| class="wikitable sortable"
! Regime
! [[Mach number|Mach No]]
! Speed
! General characteristics
!style="width: 280px;"| Aircraft 
!style="width: 280px;"| Missiles/warheads
|-
! style="background:#FFFFFF;" | [[Speed of sound|Subsonic]]
| data-sort-value=0 | [0–0.8)
| data-sort-value=0 | <{{cvt|614|mph|kph m/s}}
| Most often propeller-driven and commercial [[turbofan]] aircraft with high-aspect-ratio (slender) wings, and rounded features like the nose and leading edges.
The subsonic speed range is that range of speeds within which, all of the airflow over an aircraft is less than Mach 1.  The critical Mach number (Mcrit) is lowest free stream Mach number at which airflow over any part of the aircraft first reaches Mach 1.  So the subsonic speed range includes all speeds that are less than Mcrit.
|All commercial aircraft
|—
|-
! style="background-color: #00ff00;" | [[Transonic]]
| data-sort-value=0.8 | [0.8–1.2)
| data-sort-value=614 | {{cvt|614|-|921|mph|kph m/s}}
| Transonic aircraft nearly always have [[swept wing]]s that delay drag-divergence and [[supercritical airfoil|supercritical wings]] to delay the onset of wave drag and often feature designs adhering to the principles of the Whitcomb [[area rule]].
The transonic speed range is that range of speeds within which the airflow over different parts of an aircraft is between subsonic and supersonic. So the regime of flight from Mcrit up to Mach 1.3 is called the transonic range.{{cn|date=June 2021}}
|
* {{Flagicon|USA}} [[Northrop X-4 Bantam]] (Mach 0.9)
|—
|-
! style="background:#FFA0A0;" | [[Supersonic]]
| data-sort-value=1.2 | [1.2–5)
| data-sort-value=922 | {{cvt|921|-|3836|mph|kph m/s}}
| The supersonic speed range is that range of speeds within which all of the airflow over an aircraft is supersonic (more than Mach 1).  But airflow meeting the leading edges is initially decelerated, so the free stream speed must be slightly greater than Mach 1 to ensure that all of the flow over the aircraft is supersonic.  It is commonly accepted that the supersonic speed range starts at a free stream speed greater than Mach 1.3.
Aircraft designed to fly at supersonic speeds show large differences in their aerodynamic design because of the radical differences in the behavior of flows above Mach 1. Sharp edges, thin [[aerofoil]]-sections, and all-moving [[tailplane]]/[[Canard (aeronautics)|canards]] are common. Modern [[combat aircraft]] must compromise in order to maintain low-speed handling; "true" supersonic designs, generally incorporating delta wings, are rarer.
|
* {{Flagicon|USA}} [[North American XB-70 Valkyrie|XB-70 Valkyrie]] (Mach 3)
* {{Flagicon|USA}} [[SR-71 Blackbird]] (Mach 3)
* {{Flagicon image|Flag_of_France_and_the_United_Kingdom.svg|size=23px}} BAC/Aérospatiale [[Concorde]] (Mach 2)
* {{Flagicon|USSR}} [[Tupolev Tu-144]] (Mach 2)
|—
|-
! style="background-color:#FF7070;" | Hypersonic
| data-sort-value=5 | [5–10)
| data-sort-value=3837 | {{cvt|3836|-|7673|mph|kph m/s}}
| Cooled [[nickel]] or [[titanium]] skin; small wings. The design is highly integrated, instead of assembled from separate independently-designed components, due to the domination of interference effects, where small changes in any one component will cause large changes in air flow around all other components, which in turn affects their behavior. The result is that no one component can be designed without knowing how all other components will affect all of the air flows around the craft, and any changes to any one component may require a redesign of all other components simultaneously{{cn|date=June 2021}}. 
|
* {{Flagicon|USA}} [[North American X-15]] (Mach 6.7)
* {{Flagicon|USA}} [[NASA X-43]] (Mach 9.6)
* {{Flagicon|USA}} [[Boeing X-51 Waverider]]  (Mach 5)
* {{Flagicon|China}} [[WZ-8 (drone)|WZ-8]] (Mach 5) 
|
* {{Flagicon|Russia}}{{Flagicon|India}} [[BrahMos-II]] (Mach 8)
* {{Flagicon|Russia}} [[Kh-47M2 Kinzhal]] (Mach 10)
* {{Flagicon|Russia}} [[3M22 Zircon]] (Mach 8-9)
* {{Flagicon|China}} [[DF-ZF]] (Mach 5–10)
* {{Flagicon|India}} [[HSTDV]] (Mach 6)
* {{Flagicon|DPRK}} [[Hwasong-8]] (Mach 6–10)
|-
! style="background:#FF0000;" | Ubersonic
| data-sort-value=10 | [10–25)
| data-sort-value=7674 | {{cvt|7673|-|19180|mph|kph m/s}}
| Thermal control becomes a dominant design consideration. Structure must either be designed to operate hot, or be protected by special [[silicate]] tiles or similar. Chemically reacting flow can also cause corrosion of the vehicle's skin, with free-atomic [[oxygen]] featuring in very high-speed flows. Hypersonic designs are often forced into [[Atmospheric entry#Blunt body entry vehicles|blunt configurations]] because of the [[aerodynamic heating]] rising with a reduced [[Radius of curvature (mathematics)|radius of curvature]].
|—
|
* {{Flagicon|USSR}} [[53T6]] (Mach 17)
* {{Flagicon|USA}} [[Hypersonic Technology Vehicle 2|HTV 2]] (Mach 20)
* {{Flagicon|India}} [[Agni-V]] (Mach 24)
* {{Flagicon|China}} [[DF-41]] (Mach 25)
* {{Flagicon|France}} [[M51 (missile)|M51]] (Mach 25)
* {{Flagicon|Russia}} [[Avangard (hypersonic glide vehicle)|Avangard]] (Mach 20–27)
|-
! style="background:#000000;" | [[Atmospheric entry|Re-entry speeds]]
| data-sort-value=25 | ≥25
| data-sort-value=19180 | ≥{{cvt|19180|mph|kph m/s}}
| [[Ablative heat shield]]; small or no wings; blunt shape. See [[reentry capsule]].
|
* {{Flagicon|USA}} [[Space Shuttle orbiter]] (Mach 22)
* {{Flagicon|USSR}} [[Buran (spacecraft)|Buran]]
* {{Flagicon|USA}} [[Boeing X-37]] (Mach 25)
* {{Flagicon|China}} [[Chinese reusable experimental spacecraft|Reusable experimental spacecraft]] (~Mach 25) 
* {{Flagicon image|ESA_logo_simple.svg}} [[IXV]] (Mach 22)
|
* {{Flagicon|Russia}} [[Avangard (hypersonic glide vehicle)|Avangard]] (Mach 20–27)
|-
! style="background:#000000;" | 
| data-sort-value=estimated |168+
|201,168 - 241,596<sup>φ</sup>km/h
|flat circular
|{{Flagicon|USA}} [[Operation Plumbbob#Missing steel bore cap|iron seal]] (Mach 168 <ref>{{cite web|author=Rebecca Harrington|url=https://www.businessinsider.com/fastest-object-robert-brownlee-2016-2?international=true&r=US&IR=T#brownlee-wanted-to-measure-how-fast-the-iron-cap-flew-off-the-column-so-he-designed-a-second-experiment-pascal-b-and-got-an-incredible-calculation-6|title=A manhole cover launched into space with a nuclear test is the fastest human-made object. A scientist on Operation Plumbbob told us the unbelievable story.|date=March 3, 2023|publisher=[[Business Insider]]|access-date=6 May 2025 |archive-url=|archive-date=}}</ref><ref>{{cite web|url=https://www.unitconverters.net/speed/mph-to-kph.htm|website=unitconverters.net|title=calc. mph ⇒ kph  |access-date=6 May 2025 |archive-url=|archive-date=}}</ref><ref>{{cite web|url=https://www.calculateme.com/speed/kilometers-per-hour/to-mach/201168|website= calculateme.com|title=calc. Km/hr ⇒ Mach |access-date=6 May 2025|archive-url=|archive-date=}}</ref> - 202.5 <ref>{{cite web|url=https://space.stackexchange.com/questions/54763/where-would-the-pascal-b-manhole-cover-be-now|website= stackexchange.com|title=Space Exploration |date=November 11, 2021 |access-date=6 May 2025 |archive-url=|archive-date=}}</ref><ref>{{cite web|url=https://www.calculateme.com/speed/kilometers-per-hour/to-mach/241611|website=calculateme.com|title=calc. Km/hr ⇒ Mach   |access-date=6 May 2025  |archive-url=|archive-date=|via=sciencenotes.org/escape-velocity-definition-and-formula/: "11,185.73 meters per second" verified: S. Chands Principles Of Physics For XI p.718 "11.2km/s" (rounded 11.185km/s <sup>φ</sup>)}}</ref>)
|none
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