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Juice rerouted to Venus in first lunar-Earth flyby
- ninju 2y agoHere's a deep link to an animated overview https://www.esa.int/ESA_Multimedia/Videos/2024/08/Juice_s_lunar-Earth_flyby_in_depth https://www.esa.int/ESA_Multimedia/Videos/2024/08/Juice_s_lu... (for those that are more visual)
- istultus 2y agoThanks! (everyone is more visual, though we have less aggregated data on how blind people use their visual cortex)
- JumpCrisscross 2y ago“using the gravity of Earth to send it Venus-bound” While technically correct, this sentence is misleading. The ESA can do better. Passing by a body can deflect a spacecraft. So technically, the Earth’s gravity sends the craft “Venus bound.” But “the gravity of Earth” imparts no net delta-v and wouldn’t on its own allow the craft to reach Venus. A “gravity assist around a planet changes a spacecraft's velocity (relative to the Sun) by entering and leaving the gravitational sphere of influence of a planet” [1]. The Earth’s revolution around the Sun gets the craft to Venus, not the Earth’s gravity. [1] https://en.m.wikipedia.org/wiki/Gravity_assist https://en.m.wikipedia.org/wiki/Gravity_assist
- deleted 2y ago[deleted]
- jessriedel 2y agoThe gravity of the Earth absolutely changes the speed of the probe. In terms of the basic momentum transfers, non-propulsive gravity assists are essentially the same as elastic collisions with balls of non-equal mass. In particular, energy can be transferred, and that is mediated by the interaction forces: if a very heavy ball is rolling along at speed v and I place a tiny ball at rest in front of it, the tiny ball will bounce off at about 2v. We could certainly say “the atomic forces between the heavy ball and the tiny ball during the collision propel the tiny ball to its new destination”. This is true even though the tiny ball’s speed is constant in the center-of-mass frame.
- JumpCrisscross 2y ago> non-propulsive gravity assists are essentially the same as elastic collisions with balls of non-equal mass From the Earth’s frame of reference there is no change in delta-v other than a change in direction. It’s only from the Sun’s frame of reference that there is velocity added in the speed component (v_infinity, commonly). If you can find a single measurement to the contrary, that’s novel enough to be worth publishing. That’s why you can’t gravity assist around the Sun to get around the Solar System faster.
- saagarjha 2y agoYou’ve retreated to a different argument nobody was making.
- JumpCrisscross 2y ago> You’ve retreated to a different argument nobody was making Respectfully, I have a background in aerospace engineering. This is the number one popular misconception about gravity assists/slingshot maneuvres.
- nick238 2y agoIf jessriedel hadn't said > The gravity of the Earth absolutely changes the speed of the probe. but instead > The gravity of the Earth absolutely changes the characteristic energy with respect to the sun of the probe. Would you be happy?
- JumpCrisscross 2y agoNo. The gravity of the Earth doesn't do any work on the probe. It's a coupling mechanism. The work that is done is by Earth's orbital energy around the Sun. That is the energy that is less after the spacecraft encounters the Earth than before. The Earth is "dragging" the spacecraft along with it around the Sun. Not trebucheting it.
- verzali 2y agoCommon mistake, but it is just ESA, not "the ESA". Just as it is NASA and not "the NASA".
- deleted 2y ago[deleted]
- adolph 2y agoPrepositions in English are highly idiomatic. Although there are some rules for usage, much preposition usage is dictated by fixed expressions. [0] Prepositions are fascinating. Why is it that NASA and ESA don't get a "the" but the Sun, Earth, Moon and USA do? Why does it always feel wrong when Apple doesn't use "the" before iPod, iPhone, etc? 0. https://academicguides.waldenu.edu/writingcenter/grammar/prepositions https://academicguides.waldenu.edu/writingcenter/grammar/pre...
- thomukas 2y ago“The” is not a preposition but a definite article.
- adolph 2y agoThanks! The rules for definite articles are also odd. Only very specific categories of proper nouns are articled. USA gets one because "of" is in the name. I think the categories of articled proper nouns is probably missing sports leagues, like the NFL and the NBA. https://academicguides.waldenu.edu/writingcenter/grammar/articles https://academicguides.waldenu.edu/writingcenter/grammar/art...
- anigbrowl 2y agoI read 'send' as being about the change in direction rather than any change in velocity.
- xeonmc 2y agoIn other news, Lunchables may soon be meeting its demise: https://www.cbsnews.com/news/lunchables-lead-sodium-consumer-reports-kraft-heinz/ https://www.cbsnews.com/news/lunchables-lead-sodium-consumer...
- snapcaster 2y agoInteresting article but i think posted on wrong thread
- MatthiasPortzel 2y agoTheres a Sci-Fi story called 17776 which features a sentient version of Juice as a main character. In this interpretation, Juice is a fan of Lunchables, so it would be a shame if they stopped production before Juice became sentient.
- istultus 2y agoIsn't it time, as the process is becoming normalized (as with the Artemis project) to start using the term "(gravitational) slingshot" in headlines?
- munchler 2y agoAgreed. The word "rerouted" makes it sound like this represents a change of plans, which it is not.
- gmiller123456 2y agoSadly, the tech savy of the news seems to be going the other direction IMHO. It might also be that "redirected" sounds like something went wrong and will get more clicks.
- smcin 2y ago- 8/2025 Venus flyby - 2nd and 3rd Earth flybys 9/2026 and 1/2029 - 7/2031 arrives Jupiter; Jupiter orbit insertion and apocentre reduction with multiple Ganymede gravity assists - 1/2032 .. 11/2034 Reduction of velocity with Ganymede–Callisto assists. Increase inclination with 10–12 Callisto gravity assists. - 12/2034 enter Ganymede orbit for its close-up science mission - 12/2035 will impact on Ganymede when runs out of propellant summarizing https://en.wikipedia.org/wiki/Jupiter_Icy_Moons_Explorer#Summary_of_intended_Jupiter_mission_phases https://en.wikipedia.org/wiki/Jupiter_Icy_Moons_Explorer#Sum...
- johnklos 2y agoI'm not a fan of this inexact and incorrect language. "Rerouted" means that the route was changed, not that the trajectory was changed. The route was planned before launch, and that hasn't changed. The headline makes it seem like there was an unplanned change.