Talk:Gravity loss

message: "It might be expected that the gravity losses would up to 9.8 m/s per second of thrusting. However, by thrusting at an angle wherever possible, the overall losses are reduced by Pythagorus."
Um no. If you thrust at, say, 4g diagonally at the right angle so that you get 1g vertical component, do the maths and you get 3.87g horizontal component. So it's more efficient to thrust diagonally than to have two engines, one vertical and one horizontal. It really is due to pythagorus, and it really does reduce the gravity losses.
:Ok, I see what you mean.  You're just reminding us that forces are a vector quantity.  That's a good point that was missing from the article.  I don't think an unexplained reference to Pythagoras is sufficient, though...  I'll see if I can think of anything better.  --Doradus 20:52, Jun 17, 2005 (UTC)
===Centrifugal Force===
A may be pedantic, but centrifugal force is ficticious.  Second, the reason we want horizontal speed is never explained.  I am guessing that it is due to the fact that at a sufficiently high velocity you enter a state of constant freefall, but this is just a guess.
:It's not really ficticious in a rotating frame of reference, such as an object rotating around the center of the Earth. Or if you think it is ficticious, many other everyday forces in physics are also ficticious.WolfKeeper 02:24, 15 July 2006 (UTC)
replies: text: "Fictitious force" doesn't mean "bogus term", it's merely indication that the apparent force comes from the frame of reference being non-inertial, but it still serves a perfectly valid tool for calculations. The article on Coriolis force is doing pretty fine; one could similarly protest the imaginary number. Gravity drag is fictitious, because it's "tainted" by centrifugal force component due to the "horizontal" speed being in fact circular motion above (round) planet's surface. It absolutely doesn't make it "bogus" though, merely classifying it as a specific class of forces. Sharpfang (talk) 08:13, 9 February 2017 (UTC)
thread_title: Bogosity?

message: A may be pedantic, but centrifugal force is ficticious.  Second, the reason we want horizontal speed is never explained.  I am guessing that it is due to the fact that at a sufficiently high velocity you enter a state of constant freefall, but this is just a guess.
:It's not really ficticious in a rotating frame of reference, such as an object rotating around the center of the Earth. Or if you think it is ficticious, many other everyday forces in physics are also ficticious.WolfKeeper 02:24, 15 July 2006 (UTC)
replies: text: "Fictitious force" doesn't mean "bogus term", it's merely indication that the apparent force comes from the frame of reference being non-inertial, but it still serves a perfectly valid tool for calculations. The article on Coriolis force is doing pretty fine; one could similarly protest the imaginary number. Gravity drag is fictitious, because it's "tainted" by centrifugal force component due to the "horizontal" speed being in fact circular motion above (round) planet's surface. It absolutely doesn't make it "bogus" though, merely classifying it as a specific class of forces. Sharpfang (talk) 08:13, 9 February 2017 (UTC)
thread_title: Centrifugal Force

message: The comment about directing the thrust downwards to increase acceleration would presuppose either a really weak surface or that the rocket is already airborne.  Since gravity drag seems to be concerned with getting up higher, this example seems silly and confusing (gravity generally tends to make it easy to accelerate downwards.)
128.151.161.49
Iain Marcuson
:I removed that.--Patrick 06:39, 21 June 2007 (UTC)
replies: text: I've restored it, hopefully in a way that highlights that the downward thrust is absurd.  I also removed the remark about GEO versus escape velocity, because that has little to do with gravity drag.  It is a general statement about Hohmann transfer orbits.  --Doradus 23:52, 15 November 2007 (UTC)
thread_title: Vector Considerations

message: It would really help me as a reader if the article included a few real-world examples with actual numbers for specific spacecraft launch trajectories. Is data available for the gravity drag penalty incurred by the Space Shuttle on a launch to the ISS? Would other vehicles (e.g. Soyuz with Progress or Ariane with ATV or H-IIB with HTV) pay a lower penalty because (without humans aboard) they can accelerate more rapidly? Also, this would help make clear what units (is it meters per second squared ?) would be appropriate for measures of gravity drag. (P.S.: I don't mean the article needs to show how these values are derived -- just a table of the results would be fine. ;-) (sdsds - talk) 05:18, 16 July 2007 (UTC)
thread_title:  Numerical examples 

message: This article has no citations at all, and thus no proof is given that anyone in the real world uses the word drag to refer to the gravitational resistance on a space vehicle. Does it need to be moved to a new title? I don't think so; it seems to actually fit the intended meaning of WP:Original research: someone's presentation of a subject, and probably should be deleted. The topic is covered in Flight dynamics (spacecraft)#Powered flight. After powered flight (i.e. achieving orbit or greater), it's generally just considered gravity, not drag. It has nothing at all to do with Drag (physics). JustinTime55 (talk) 16:49, 21 February 2014 (UTC)
replies: text: Gravity drag is a term in common use in the space community though. A search for phrase "gravity drag" through KSP forum produces 373 hits. ("gravitational drag", another variant of the same, yields additional 30.)  space.stackexchange.com yields 30+4. I'm yet to see it in any scientific papers (doesn't mean it's absent there) but it definitely deserves an article, to serve as aid for people who encounter it for the first time - even if actual, peer-reviewed materials are hard to come by. Sharpfang (talk) 08:02, 9 February 2017 (UTC)
replies: text: Gravity "drag" is a term in common misuse in the KSP community.  In the scientific community is known as "gravity loss", while aerodynamics drag produces "drag loss", there is also "steering loss" for when the thrust angle is not collinear with the orbital velocity forward velocity vector.  Lamontcg (talk) 01:46, 3 May 2019 (UTC)
replies: text: A space simulation video game "community" does not count as part of the astrodynamics or rocketry scientific community, no matter how much NASA "endorses" it. The professional term is gravity loss, and the page was moved there. JustinTime55 (talk) 01:22, 6 March 2021 (UTC)
thread_title:  Original research 

message: Logsdon, Tom, "Orbital Mechanics: Theory and Applications" ISBN-13: 978-0471146360.  See the discussion on page 119 that may be accessible through google books.  Curtis, Howard D.  "Orbital Mechanics for Engineering Students", 3rd ed. also has an appendix D with code samples at the publisher site -- Under "D.40 Calculation of a gravity-turn trajectory" there is a matlab script which integrates an ascent and calculates gravity loss and drag loss.  And note that the term used in these references is "gravity loss" not "gravity drag" and "drag loss" is consistently used across both for atmospheric drag.  I believe the KSP and stackexchange community are likely misusing terminology (and the article title should get updated).  The Vinh reference also is going to be useless to understand this concept and should be dropped.  The section in the Logsdon book is vastly clearer.  I'd update the article myself, but I don't have the patience to deal with the wikipedia process (and the poor quality of this article as it is just frustrates me)  Lamontcg (talk) 03:46, 14 July 2018 (UTC)
thread_title:  Better References