Talk:North American X-15

Navy pilot never earned astronaut wings
" The only Navy pilot in the X-15 program never took the aircraft above the requisite 50 mile (80 km) altitude and thus never earned astronaut wings.[3][4]"

Neil Armstrong, first man on the moon, is the navy pilot mentioned. It is erroneous to say that he "never earned astronaut wings". — Preceding unsigned comment added by 142.19.97.4 (talk) 17:06, 12 October 2018 (UTC)


 * It means he never earned them in the X-15. - BilCat (talk) 17:38, 12 October 2018 (UTC)
 * It also isn't referring to Neil Armstrong, a member of NASA at the time, but Forrest S. Petersen. Buffs (talk) 22:26, 12 October 2018 (UTC)

duration of/distance covered by the flights at record speed
you guys should add duration of/distance covered by the flights at record speed if known... — Preceding unsigned comment added by 2001:67c:10ec:578f:8000::39 (talk • contribs) 22:31, 12 June 2020 (UTC)

Mach number
The last time I was accused of taking part in a so-called "editing war" was almost 5 years ago about the page "Get Out." I cited multiple references showing that this film was in fact of the "horror movie" genre. In the end, I just gave up, realizing that Wikipedia can't really be edited by anyone but by a clique engaging in crass cronyism. The level of bickering is beyond sensibilities and rather tiresome, dissuading anyone outside this clique to ever have the gall to dare contributing ever again.

Nothing really changed since then. The same clique prefers pronouncements from Official sources (what are you, their PR agents?) instead of scientific scrutiny. In this instance, NASA claims that Mach 6.7 equals 7 274 km/h. You won't find that conversion from ANY conversion tool available online today. Not even Google can come-up with it.

The argument that both altitude and temperature affect Mach speed is correct. These same conditions affect just the same speed measured in km/h. That's like saying one foot doesn't equate 12 inches. Both Mach reading and km/h reading are measuring the same movement, affected by the same conditions, the reading is just in different units

Alas, you just don't get that. So once again, I'm just going to abandon the whole debate. I promise to never interfere with your club ever again.24.53.51.129 (talk) 05:28, 11 October 2021 (UTC)


 * It is a useful topic to discuss and debunk here. The relationship between Mach number and speed (measured in any units you like: km/h, mph, knots, furlongs/fortnight, etc) are not fixed and vary greatly depending on air temperature and therefore altitude. The statement The argument that both altitude and temperature affect Mach speed is correct. These same conditions affect just the same speed measured in km/h. is only party correct. The first sentence is right and the second sentence is wrong. A vehicle travelling at 1,000 km/h is always travelling at 1,000 km/h, regardless of air temperature or altitude, but the corresponding Mach number for 1,000 km/h will vary by a large measure due to those factors. There is no fixed relationship between speed and Mach number, as they will vary within a range. The claim Mach 6.7 equals 7 274 km/h will be right for one temperature and wrong for all others. Without knowing the temperature and/or altitude the statement is fairly meaningless. Likewise That's like saying one foot doesn't equate 12 inches. Both Mach reading and km/h reading are measuring the same movement, affected by the same conditions, the reading is just in different units is not correct and shows a fundamental misunderstanding of the measurements of these two speed parameters. One is an absolute speed relative to the surface of the earth and the other is a relative ratio between the aircraft and the local speed of sound.


 * While we are debunking myths here is it also worth noting that when someone disagrees with you here it does not indicate that it is due to some vague conspiracy as you expressed: In the end, I just gave up, realizing that Wikipedia can't really be edited by anyone but by a clique engaging in crass cronyism. In fact the reason people disagree with you is that you have a poor grasp of the subject and the claims you have made are demonstrably false. We actually have guidance on just this subject. - Ahunt (talk) 12:20, 11 October 2021 (UTC)


 * We are not here to figure out the math. We are here to summarize the reliably published sources, which are all in agreement that the X-15 hit Mach 6.7. Book sources for that number include Michelle Evans's book The X-15 Rocket Plane: Flying the First Wings Into Space, Peter E. Davies's book North American X-15, Dennis R. Jenkins's book X-15: Extending the Frontiers of Flight, Frank Hitchens's book The Encyclopedia of Aerodynamics, William A. Flanagan's book Aviation Records in the Jet Age, T.A. Heppenheimer's book Facing the Heat Barrier: A History of Hypersonics, and many more—even the magazine Popular Mechanics in an article by William Garvey. That represents just a few minutes of searching. Binksternet (talk) 12:53, 11 October 2021 (UTC)


 * While we aren't here to figure out the math, it's a fair question to ask on the talk page concerning the computation. I too am completely new to this page and, when checking the four cited sources on max speed, was wondering how they calculates 4,520 mph as 6.7 mach, even though "plain" math yields 5.9 mach. Don't really care much about bloggers and journalists, but when NASA (source #2) calculates it so, that does lead one to ask questions. One has to go to nearly the last section of the mach speed wiki page to find even a mention of this. — Preceding unsigned comment added by 97.120.137.228 (talk) 16:59, 6 June 2022 (UTC)
 * I really don't understand why some people find it so hard to understand that Mach number is variable depending upon atmospheric conditions. I heard about it at age 13, and it wasn't that difficult a concept to get. Is modern education really that bad now? BilCat (talk) 17:36, 6 June 2022 (UTC)
 * Thank you for correcting. Hadn't noticed the pre-existing conversation.Tmpst (talk) 19:56, 9 June 2022 (UTC)
 * It sounds like in this case NASA is not just official but authoritative which is what counts. For one thing they certainly have the propellerheads available to do it right. For another, if that page is wrong I would expect that it would have pointed out to them several times and they would have fixed it. Herostratus (talk) 21:36, 9 June 2022 (UTC)


 * Sorry, I thought the speed of sound was constant at 340 meters per second thank you so much 197.37.243.55 (talk) 20:12, 26 August 2022 (UTC)
 * It's OK. At least you know now. BilCat (talk) 21:16, 26 August 2022 (UTC)
 * Thank you all, I didn't realize it was variable either, but makes perfect sense. :)  -  FlightTime  ( open channel ) 21:45, 26 August 2022 (UTC)
 * You're not alone, as it's a very common misconception, but unfortunately you both seem to rare in accepting that fact without endless arguments. Thanks also! BilCat (talk) 02:05, 27 August 2022 (UTC)

The Mach numbers in the tables in the "Highest flights" and "Fastest recorded flights" sections don't seem to be accurate - for example, Flight 188 is listed as Mach 6.00 even though it's (correctly) stated to be Mach 6.7 elsewhere. It looks like the tables are using something close to the sea level conversion factor between speed and Mach #. I think it would be better if the Mach numbers were either removed or corrected with a source to back them up. This NASA page has a log of all X-15 flights and seems to be a reliable source. Any objections to updating the tables with the Mach numbers listed there? Nyvhek (talk) 20:30, 15 September 2022 (UTC)


 * We may have missed some "corrections" that weren't correct. I'd say go ahead and update it using NASA's numbers. BilCat (talk) 20:45, 15 September 2022 (UTC)

Plane 66672 Blown Up?
On YouTube, there is a documentary that was clearly produced in close co-ordination with the USAF, NASA and North American. During this documentary, footage is shown of the "big" XLR99 engine undergoing a ground test, attached to plane 66672, being controlled by Scott Crossfield. After an engine shutdown, he restarts the engine, and the entire rear half of the plane explodes. It appears this happened on 6-8-60 (I'm guessing it's an American date, so June 8th 1960?). There is an interview with Crossfield where he shows pictures of the wreckage, and explains that the failure was caused by the hydrogen peroxide tank being smashed open by the ammonia tank, which had failed due to over-pressure; the over-pressure should have been prevented by the main valve turning off when commanded, but it was found to likely have been frozen in the full-open position. Additionally, there was an emergency vent valve that should also have blown to relieve the pressure, but it too was faulty. He specifically says "A frozen regulator, a faulty relief valve, and a high back pressure relief system had gotten together, and we had wrecked an airplane" (emphasis mine).

There doesn't seem to be any mention of this anywhere in the article, which I found surprising considering that it appears to have caused extensive damage, if not an outright loss, of the plane numbered 66672. The article lists this as plane #3, the same plane that later killed Michael J. Adams. So was this plane actually repaired, or did they re-use the plane number? Unfortunately the documentary doesn't have enough detail or any credits/title sequences to figure out who produced it, and without knowing this I don't think it can be used as a citation to add this info to the article.

FYI, one of the photos has an ID number on it of 240-861-30H -- it might be possible to do a FOIA request or similar to get a copy of this photo to add to the article, which may also lead to more info about the accident and the report(s) surrounding it, if any. Thoughts?  M r A urelius R  Talk! 12:28, 28 March 2023 (UTC)