Talk:Reduced-gravity aircraft

Not an aircraft type.

The lead is misleading. It's not a type of aircraft at all it's just a particular use of an aircraft. Almost any aircraft is capable of zero-g trajectory flight. Roger (talk) 17:16, 20 July 2012 (UTC)

vomit

"On commercial flights offered by Zero Gravity Corporation, very few passengers (cite) experience motion discomfort. This is because the flight profile of 15 parabolas, versus NASA's 40–60 parabolas, is designed to help alleviate airsickness."

The (cite) is Zero Gravity Corp's site, which seems to be selling their service. — Preceding unsigned comment added by 68.248.74.222 (talk) 23:39, 18 July 2013 (UTC)

Missing connections to Wikipedia articles in other languages

https://de.wikipedia.org/wiki/Parabelflug — Preceding unsigned comment added by 2A02:8109:B00:4776:C8:F17F:6360:C6AB (talk) 09:01, 6 January 2021 (UTC)

Is "parabolic" accurate?

Elementary physics courses tell us that falling objects follow a parabola. This is because most everyday falling objects don't transverse downrange for an appreciable difference between parallel gravity and real gravity. A vomit comet also don't travel very far along the "x-axis" in a particular dip. So a parabola is probably close enough.

But if we were being super accurate, would we be talking about ellipses instead of parabolas/ae? Or does Earth's whole "I'm not a single point in space but rather a body that occupies a bit of that space" make "parabolic" more accurate than "elliptical" at this altitude range? Sincerely asking, because I know parabolic models fall off with increasing altitude. Tom Something (talk) 08:01, 26 November 2022 (UTC)

I made and added the picture with parabolic and elliptic trajectories. If Earth isn't a symmetric sphere there'll be distortions, e.g. if there's sea, land and mountains. It really should be 'elliptic' unless we're on an escape trajectory with c3=0. Parabolas have nicer math, though. Darsie42 (talk) 14:01, 10 October 2023 (UTC)

I suspect that in the specific case here - an aircraft creating 'weightlessness' - the difference between the theoretical ellipse required and a parabola is insignificant in comparison to the limits to which an aircraft can realistically be flown. The diagram exaggerates the discrepancy greatly since the height of the climb/descent is far larger in relation to the radius of the Earth than is the case in reality. AndyTheGrump (talk) 14:22, 10 October 2023 (UTC)

Elementary physics and math can be used to show that an object moving in a vacuum, solely under the influence of its own weight, follows a ballistic path that is parabolic. Reduced gravity aircraft don’t move in a vacuum - they move through the air and that air exerts considerable drag on the aircraft; even the effect of the drag isn’t uniform because it is partly counteracted by the thrust from the engines. Finally, reduced gravity aircraft aren’t free to follow a ballistic path - the aircraft is flown by an autopilot which manipulates the elevator in order to maintain, as closely as possible, a zero-G environment for a significant period of time. The result is that it is inaccurate to imagine that these aircraft follow a parabolic path. Dolphin (t) 14:43, 10 October 2023 (UTC)

Ok, someone do the math, and tell us how much the discrepancy between elliptical and parabolic paths there would be, in the cases described in this article. AndyTheGrump (talk) 15:01, 10 October 2023 (UTC)

Note also that NASA (who presumably understand the relevant physics), describe the flight paths as 'parabolas' on their own website. [1] Evidently they don't consider nit-picking worthwhile. AndyTheGrump (talk) 15:12, 10 October 2023 (UTC)

I've removed the 'ballistic trajectories' image, as grossly out of scale. Without secondary sources, we shouldn't be trying to contradict NASA etc over terminology for the sake of inconsequential nit-picking WP:OR. AndyTheGrump (talk) 21:08, 10 October 2023 (UTC)

Yes, it's true, In the case of parabolic flight the difference is insignificant. Well, I guess, I haven't calculated the difference. If it's <1 cm I'd say it's insignificant. Fun fact, the speed of light is infinite, for practical situations. Turn the light on and the room is lit instantly, practically. But the speed of light is not actually infinite. And 0 g flights are not parabolic, actually. They are also not elliptic, if we nitpick, because the plane doesn't follow the ideal path exactly and corrects for that all the time. Also Earth doesn't have perfectly spherical gravity. But the truth is closer to elliptic than to parabolic. Parabolic would be true if Earth was flat and accelerating up. Hey, it's ok to say Earth is flat, it's true, kinda. It's average curvature is flatter than an optical flat, which you could reasonably say is flat. But it's also ok to say it's round. So everybody calls them 'parabolic flights', even NASA, as you said below. It's ok, approximately. But elliptic is closer to the truth.

I made the image that way so you can see the deviation between parabola and ellipse clearly. It's not meant to suggest planes fly that high. I could have drawn a straight line from the center to the surface, that would better reflect this case, but it wouldn't convey what it should. I didn't even calculate and draw the ellipse exactly where it should be, just where it looked ok. It doesn't need to be 100% accurate to convey the meaning, like a drawing on the back of an envelope. By removing it you needlessly took away some information some people wonder about sometimes, like Tom Something. Darsie42 (talk) 22:29, 5 February 2024 (UTC)