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should the history and recent progress be moved to hypersonic flight or hypersonic aircraft really this page should just be a definition of the term with links to hypersonic vehicles and proposals. Theon 20:35, Jun 18, 2004 (UTC)
This article lacks any real detailed information on the subject. I have tagged it for an expert. Ifnord 14:15, 11 January 2006 (UTC)
Surly all fluid flows obay the navier stokes equations, unless the dencity becomes too low to assume bulk flow charicteristics, ect. can some one expand on this? — Preceding unsigned comment added by 132.244.246.25 ( talk) 12:49, 31 July 2006 (UTC)
And that's exactly what it says in the article. AKAF 07:31, 8 August 2006 (UTC)
can we get a plain english version for this page? Hard to understand for us layfolks. — Preceding unsigned comment added by 71.195.33.69 ( talk) 00:37, 7 January 2007 (UTC)
To get into earth orbit, people are telling me that you need to do Mach 25, and that the NASA Space Shuttle does in fact kick up to that speed. That's hypersonic. But what about the hypersonic shockwaves? NASA simulates their launches with OVERFLOW, a computer program for computational fluid dynamics, and as far as I can tell -- from reading Peter G. Buning's website -- there are no modified Navier-Stokes used in the program. The NS equations are known to fail beyond Mach 2 (or so) except in the case of the modifications by Howard Brenner and Reese et al., telling me that NASA is probably not accounting for hypersonic shockwaves since they can generate so much thrust with their truly awesome supply of LOX. Alternatively, maybe Max Q lets us know when we can kick up to hypersonic speeds, where shockwaves cannot be generated due to air density? Can anybody help me resolve this problem? Once again, it's just that it seems that NASA does not take into account hypersonic shockwaves, and I don't know why or how that's possible without them blowing up. Launch only, re-entry doesn't matter much to me at the moment. -- kanzure ( talk) 16:10, 9 March 2008 (UTC)
The article should include coverage of vehicles that fly at these speeds. Are there currently only two vehicle designs which are used for non-experimental controlled flight at hypersonic speeds (Shuttle and Soyuz re-entry)? Except when the Soyuz capsule reverts to ballistic reentry (as has happened recently), it is in controlled flight, as is (obviously) the shuttle. After shuttle's retirement (2010-ish), will there be only one, and an unreliable one at that? Or on ascent is any orbit-bound rocket "flying" at hypersonic speed? Is there a way to distinguish the kinds of aerodynamics involved in rocket ascent and capsule or orbiter reentry? ( sdsds - talk) 17:37, 14 June 2008 (UTC)
I marked the article as too technical because of a number of technical terms it uses, and a huge number of assumptions it makes about the reader's knowledge. The article is entirely inaccessible to a person who does not already know the material in the article, which makes it useless. Since my tag was removed, here's a list of the problems in the article: a) "The hypersonic regime is a subset of the supersonic regime." - The word "regime" as used here does not match any common English definition of the word, so I assume it's jargon. b) "Flow" is never defined, but it is implied that it means "airflow". c) The section "Thin shock layer" has no link or explanation of the definition of "shock", and a very poor explanation of "shock layer". d) "Entropy" should be linked or defined. e) "a strong entropy gradient and highly vortical flow that mixes with the boundary layer" - Incomprehensible without definitions of "entropy gradient", "vortical flow", and "boundary layer". f) "large kinetic energy associated with flow at high Mach numbers transforms into internal energy in the fluid due to viscous effects" - "internal energy" is not linked. The whole thing is poorly explained... what viscous effects? What fluid? Why is large kinetic energy associated with flow at "high Mach numbers"? g) "High temperatures discussed previously as a manifestation of viscous dissipation cause non-equilibrium chemical flow properties such as dissociation and ionization of molecules resulting in convective and radiative heating." - First use of "dissipation" in the article (even though is says it was discussed previously), failure to define "non-equilibrium chemical flow", dissociation and ionization not linked. h) "The hypersonic flow regime is characterized by a number of effects which are not found in typical aircraft operating at low subsonic Mach numbers. The effects depend strongly on the speed and type of vehicle under investigation." Contains no useful information.
"Similarity parameters" is well-written and well-linked. Woo.
i) "Regime" is still undefined, even in its own section. j) References are made, again, to "the gas" without explanation of what gas. k) "Adiabatic" is hardly common English. l) "This is a subset of the perfect gas regime, where the gas can be considered chemically perfect, but the rotational and vibrational temperatures of the gas must be considered separately, leading to two temperature models. See particularly the modeling of supersonic nozzles, where vibrational freezing becomes important." - The section claims to "separate" hypersonic flow into a number of regimes, then says that one regime is a subset of another, so they're not, in fact, separate. This part also refers to a "chemically perfect" gas, "rotational and vibrational temperature", "supersonic nozzles", and "vibrational freezing", none of which are defined. m) "The type of gas selected begins to have an effect on the flow." - No selection was mentioned up until this point, so how can the reader understand what that word means? n) "the ionized electron population of the stagnated flow becomes significant" - What ionized electron population? Where did it come from? What is a stagnated flow? o) "freestream" is undefined. p) The link for "plasmas" does not explain "non-radiating plasmas", and neither does this section. q) "the heat transfer to a vehicle changes from being conductively dominated to radiatively dominated" - Barely understandable phrasing for a very simple concept.
Is it really necessary to have an entire alphabet of problems with an article for it to be deemed unacceptable? Someone needs to clean this article up, and since I don't know anything about hypersonic aircraft, I cannot be the person to do it. So I mark it for someone else to fix. Timaster735 ( talk) 21:39, 17 February 2009 (UTC)
Can someone with knowledge on this topic please complete the 'High temperature flow' section, as it ends in the middle of a sentence (after the word radiative) 1812ahill ( talk) 01:23, 4 January 2010 (UTC)
In the second line it is stated that: "The hypersonic regime is a subset of the supersonic regime." Also, in the "Supersonic" article, the first sentence reads: "The term supersonic is used to define a speed that is over the speed of sound (Mach 1)."
However, in the "Classification" section the supersonic range is defined as "1.0 - 5.0 Mach".
Wouldn't it be more correct to change the line in the "Classification" section to "> 1.0 Mach"?
Rasmuskold ( talk) 11:35, 20 August 2010 (UTC)
I have changed the "subsonic" definition in the table, as well as the supersonic definition. If you're GOING to talk about a class of flows (and aircraft) called "transonic" then subsonic should be below the generally acknowledged limit of the validity of the Prandtl-Glauert compressibility correction.
Yes, of course I understand the "technicality" that below M=1 is "subsonic" but by the exact same token Mach 12 is then also "Supersonic".
With the general agreement that Supersonic-Regime only goes up to Mach 5 or so, comes the condition that Transonic gets to be it's own class, without overlapping with the others.
An aircraft designed to fly at M=0.9 for example would only rarely be described as "Subsonic". Modern airliners for example, often cruising at between M=0.8 and M=0.85 get referred to as "transonic aircraft".
Princeofdelft 18:39, 16 September 2010 (CEST)
That table is partially useless. Hypersonics/supersonics etc. is all well and good but doesn't only apply to air. 768 mph is only sonic velocity (i.e. mach = 1) at Sea Level in AIR at a certain temperature. That table should be removed if it isn't clarified that those are sea level values in air at 0 celsius (I believe). Speed of sound is dependent on temperature and gas characteristics. You can achieve hypersonic speed in the atmosphere of different planets and it won't be at the same speeds as on earth. 66.102.16.20 ( talk) 01:58, 16 November 2010 (UTC)
The table list "high hypersonic" (> Mach 10). The technical term for this is "plasmasonic". [1] [2] [3] This should be mentioned in the article, perhaps even that entry in the table retitled "plasmasonic".-- Solomonfromfinland ( talk) 07:56, 4 December 2018 (UTC)
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The chart showing mach speeds, mph, km/h, and m/s needs going over with some math. The m/s and mph equivalencies are dodgy as shit. I would fix it, but I don't know which figures to go with (whether the mph or m/s figures are more accurate to the mach figures). Deltopia ( talk) 23:17, 25 April 2011 (UTC)
The topic is challenging on its own, yet I found some of the paragraphs in this article to be formulated in a rather convoluted manner, which only adds to the difficulty. If someone with sufficient knowledge on the topic could look into that, I'd much appreciate it.
Examples:
"The density behind the shock that a body generates increases with its Mach number because conservation of mass demands a corresponding to a decrease in volume behind the shock wave and its distance to the body."
This sentence seems malformed. ("...demands a corresponding to a decrease...")
"Viscosity causes some of the great
kinetic energy associated highly supersonic flow to become
internal energy in the fluid, thereby increasing its temperature."
Does "great" carry meaning here? Could the "A associated B C" sentence structure be rephrased? If it means to say "supersonic flow associated with kinetic energy", then phrase it that way.
"The pressure gradient normal to the flow within a boundary layer is almost zero for low to moderate hypersonic Mach numbers, increasing the boundary layer's temperature and decreasing the layer's density and thus so expanding the layer's bottom that the boundary layer thickens and often merges with the leading edge's shock wave."
Sentences like this need to be split; it's almost incomprehensible. If you shorten it while maintaining its general structure, it too looks malformed: ("The pressure gradient is almost zero, increasing the layer's temperature, and thus expanding the bottom that the layer thickens and often merges with the leading edge's shock wave.")
I hope you see my point. I lack the required knowledge on this topic to fix these issues myself. MSUGRA ( talk) 16:18, 6 May 2014 (UTC)
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