Talk:Gravity assist

message: For the record, the Saturn example was somewhat imprecise.  It claimed the delta-v for the Hohmann transfer from Earth to Saturn is 15.7 km/s.  However, this figure disregards two effects that alter the situation drastically:
# The planets' own gravity.  To get from a low-Earth orbit to a low-Saturn orbit actually requires about 18 km/s.
# Aerobraking.  Upon arriving at Saturn, it's only necessary to alter the spacecraft's orbit around Saturn from a hyperbola to an ellipse with a periapsis passing through Saturn's atmosphere; after that, subsequent passes through periapsis will circularize the orbit.  Taking this into account leads to a delta-v more like 10 km/s.
I added "disregarding Earth's and Saturn's own gravity wells".  (I forgot to mention aerobraking, but I figure that's not worth disrupting the flow of the sentence any more than I already have.)  --Doradus 21:09, Jun 18, 2005 (UTC)
:For clarity, it ought to be a comparion of the same mission flown with and without the slingshot. What happens at the destination should be the same, whether it's a flyby, braking into orbit with a rocket, or aerobraking. Since the paragraph uses Cassini as an example, what would the total delta-V be, going directly to the same orbit around Saturn? The cited 2 km/s figure obviously doesn't include Cassini's intial boost.
:—wwoods 00:04, 19 Jun 2005 (UTC)
thread_title:  Saturn example 

message: Under the section Powered slingshots, does the last sentence of the first paragraph make sense? "The extra energy comes from the propellant being "left behind" in the planet's gravity well." ~ Rollo44 15:02, 9 February 2007 (UTC)
replies: text: No, it's nonsense. If that were true they could just dump some propellant to "leave it behind" - Rod57 (talk) 14:56, 29 November 2019 (UTC)
thread_title:  Question on powered slingshot 

message: :to decelerate a spacecraft (useful when traveling to an inner planet) or accelerate a spacecraft (useful when traveling to an outer planet).
I have always thought it should be vice versa, the inner planets are traveling much faster than the outer. (Igny (talk) 16:26, 6 October 2008 (UTC)
replies: text: All explained in, eg. Hohmann transfer. You slow down to drop your perihelion or shrink the orbit. You speed up to raise your aphelion or expand the orbit. - Rod57 (talk) 14:47, 29 November 2019 (UTC)
thread_title:  Error in the lead? No 

message: What is the data and/or source of the data for the animations of the satellite launches? The animations are very pretty but they are not cited or defined in any way. BigBadAlgae (talk) 11:42, 29 March 2020 (UTC)
thread_title:  Data/source for animations? 

message: I check pages listed in :Category:Pages with incorrect ref formatting to try to fix reference errors. One of the things I do is look for content for orphaned references in wikilinked articles. I have found content for some of :Gravity assist's orphans, the problem is that I found more than one version. I can't determine which (if any) is correct for this article, so I am asking for a sentient editor to look it over and copy the correct ref content into this article.
Reference named "PionOdys":
From Pioneer 10: 
From Pioneer 11: 
I apologize if any of the above are effectively identical; I am just a simple computer program, so I can't determine whether minor differences are significant or not. AnomieBOT⚡ 02:22, 18 April 2021 (UTC)
thread_title:  Orphaned references in [[:Gravity assist]] 

message: Too much irrelevant detail in the summary of Voyager 1 & 2 (and maybe other missions). Only the details of the trajectory and gravity assist are needed in this article ? - Rod57 (talk) 19:52, 26 September 2021 (UTC)
thread_title:  Too much irrelevant detail 

message: > Another potential application of gravity assist is alteration of the Earth's orbital distance from the Sun to reduce increasing global temperatures.
Thus paragraph sounds like a mad scientist running amok. Firstly, a civilization capable of such a grand feat would have already mastered controlled thermonuclear fusion and tapping of Casimir-vacuum for clean energy and thus need not worry about AGW. On the other hand, significantly displacing Earth and Moon within the Solar System might make other planets deviate as a side-effect and maybe end with a collision of (AGW-free) Earth and a perturbed asteroid, exterminating all life... 78.131.76.69 (talk) 20:15, 15 December 2022 (UTC)
thread_title:  Is this super-villainy subplot really warranted in the article? 

message: Not sure this is correct: 'General relativity predicts that a spinning black hole is surrounded by a region of space, called the ergosphere, within which standing still (with respect to the black hole's spin) is impossible, because .'
I think that would only be the case in the limit where the black hole is spinning so fast it can't grow anymore, and in all other cases, a spinning black hole would cause the space around it to spiral inwards rather than moving in exactly circular motion. 125.253.110.41 (talk) 06:45, 21 August 2023 (UTC)
thread_title:  'space itself is dragged at the speed of light in the same direction as the black hole's spin'???