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| | ==Explanation== | | ==Explanation== |
| − | The six words are: "It works in ''Kerbal Space Program''". | + | The {{w|Kuiper Belt}} is a region of the outer Solar System beyond the orbit of Neptune consisting of numerous small icy bodies, including the dwarf planets {{w|Pluto}} and {{w|Eris (dwarf planet)|Eris}}. An {{w|Oberth effect|Oberth maneuver}} is a spaceflight maneuver, assisted by an engine burn, performed during the flyby near an other celestial body. The point of this is to optimize usable energy, because rocket burns are more effective to perform at high speeds than at low speeds. The more massive the body and the lower the altitude, the higher the flyby speed will be, and the greater the performance gain due to the Oberth effect. The theoretical way to use rocket fuel most efficiently is therefore to execute the burn during a flyby of the most massive space body available, as close as possible. |
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| − | ===Oberth maneuvers===
| + | Cueball is proposing to implement an "Oberth Kuiper Maneuver", and the proposal diagram shows the spacecraft using {{w|Gravity assist|gravity assists}} to slingshot towards a distant body after first travelling toward {{w|Venus}} for a first boost, and then heading back towards the Sun by using the the "Oberth Maneuver" at an Kuiper Belt object. The travel to an object so far will take a long time, but the advantage would be that the probe does not need to alter its speed that much to reach the sun as it would be necessary at a solar distance at earth's orbit. After that maneuver the probe will just ''fall'' into the direction of the sun. |
| − | The {{w|Kuiper Belt}} is a region of the outer Solar System beyond the orbit of Neptune consisting of numerous small icy bodies, including the dwarf planets {{w|Pluto}} and {{w|Eris (dwarf planet)|Eris}}. An {{w|Oberth effect|Oberth maneuver}} is a spaceflight maneuver, specifically an engine burn performed during the flyby of a celestial body. The point of this is to optimize usable energy, because rocket burns are more effective to perform at high speeds than at low speeds. The more massive the body and the lower the altitude, the higher the flyby speed will be, and the greater the performance gain due to the Oberth effect. The theoretical way to use rocket fuel most efficiently is therefore to execute the burn during a flyby of the most massive celestial body available, as close as possible.
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| − | [[Cueball]] is proposing to implement an "Oberth Kuiper Maneuver", and the proposal diagram shows the spacecraft using {{w|Gravity assist|gravity assists}} to travel first towards (presumably) {{w|Venus}} for a first boost, then towards Jupiter for another swing by, aiming it back towards the {{w|Sun}}, the most massive Solar System body, to perform an Oberth maneuver at the point of closest approach, as indicated by a small dot along the spacecraft trajectory. It is possible that the diagram might only be a simplified outline of a more complex flight plan. For example, the trajectory from Earth to Venus would require two separate burns in deep space. The first burn would occur immediately after escaping Earth's sphere of influence. The second burn would occur about halfway to Venus. Alternatively, Cueball may have gotten it wrong, or [[Randall]] may simply not have concerned himself with such things for the purpose of a webcomic sketch.
| + | Such a maneuver, while theoretically possible, would however be infeasible in real life, because the spacecraft could be incinerated during a too-close flyby of the Sun. But if it succeeded, the probe would accelerate to high speed, eventually leaving our solar system. |
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| − | An Oberth maneuver in the close vicinity of the Sun, while theoretically possible and extraordinarily effective at the speeds the spacecraft would reach, would however be very difficult to carry out in real life, because the neighborhood of the Sun is an extremely hostile environment{{Citation needed}} and the spacecraft could be incinerated during a too-close flyby.
| + | Cueball's argument for why the maneuver will work in real life is that it works in {{w|Kerbal Space Program}}, an in-progress sandbox space flight simulator. While it does take into account quite a bit of the physics in a space flight, many liberties were taken in its production, such as a very simple relationship between mass and drag. The humour in referencing it lies in using a simple game program to simulate programs which take a great number of experts to implement. Use of Kerbal Space Program alone isn't a good enough argument for NASA to agree to implement the proposal; therefore one should not say it at NASA. |
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| − | ===''Kerbal Space Program''===
| + | The title text refers to {{w|Orbiter_(simulator)|Orbiter}}, which is another space flight simulator program. The title text suggests that the argument doesn't work for NASA, not because it's not scientifically sound, but because NASA relies on the Orbiter simulator rather than the Kerbal simulator (although the proposed maneuver would appear to work in both). Note, however, that [http://news.cnet.com/8301-1023_3-57495117-93/mars-curiosity-rover-team-prefers-macs-to-pcs/ a few team members "love" to play Kerbal]. (OK, it is getting bad when explainxkcd needs it's own explain; the "Kerbal vs Orbiter" is a simple reference to the nerdy PC vs Mac argument). |
| − | Cueball's argument for why the maneuver will work in real life is that it works in ''{{w|Kerbal Space Program}}'' (KSP), a sandbox spaceflight simulator game. While KSP does simulate a lot of the physics of space flight, it is (necessarily) simplistic in its modeling of orbital dynamics. For example, KSP does not do any {{w|N-body simulation}}s, so if one were flying a rocket from Earth to the moon, in the game the rocket would only be affected by Earth's gravity until it reaches a certain point where it will only be affected by the moon's gravity, unlike in real life where the rocket would feel the effects of both celestial bodies at all times. Therefore, orbits modeled using KSP would poorly reflect the actual orbital behavior of a probe traveling through the solar system on a multi-year mission involving multiple fly-by maneuvers.
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| − | Another reason why using KSP would not inspire confidence is that many players playing the game use a 'trial-and-error' method, field testing designs and inevitably either crashing them or running out of fuel stranding the craft in deep space. Inside a game this is not a major issue as one can simply reload an earlier save with no repercussions, but in real life this would result in expensive costs constructing new spacecraft and even loss of human life, which NASA would likely frown upon.{{Citation needed}}
| + | The identity of the distant object is unclear, but it could be Pluto or Eris. Nevertheless, there are many more (even unknown) objects at the belt. |
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| − | The humor in referencing KSP in the comic lies in using a simple game program to simulate complex space missions which in reality take a great number of experts to plan and implement. Fly-by maneuvers, used to minimize the fuel needed to reach a destination, need to be very carefully timed - often to within seconds - so the use of ''Kerbal Space Program'' to simulate them isn't a good enough argument for NASA to agree to implement the proposal, and implies simplistic thinking on the part of the proposer; therefore one should not say it at NASA.
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| − | The title text refers to ''{{w|Orbiter (simulator)|Orbiter}}'', which is another spaceflight simulator program. The title text suggests that the argument doesn't work for NASA, not because it's not scientifically sound, but because NASA relies on the ''Orbiter'' simulator rather than the ''Kerbal'' simulator (although the proposed maneuver would appear to work in both).
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| | ==Transcript== | | ==Transcript== |
| − | :[Caption above the frame:]
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| | :The six words you ''never'' say at NASA: | | :The six words you ''never'' say at NASA: |
| − | | + | :Cueball: And besides- |
| − | :[A diagram shows a possible trajectory path for a space probe starting at Earth and involving two slingshots around two other planets, and finally the Sun. There is a title above and a label beneath the diagram. The diagram is being presented by Cueball in front of three other Cueball-like guys. Behind Cueball Ponytail appears to be taken by surprise by his six words, and holds her hand to her mouth.]
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| − | :Title: Proposal:
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| − | :Label: Oberth Kuiper Maneuver
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| − | :Cueball: And besides— | |
| | :Cueball: It works in Kerbal Space Program. | | :Cueball: It works in Kerbal Space Program. |
| | + | :[Cueball pointing at a diagram labelled "Proposal:", with the Sun in the middle and a trajectory showing a spacecraft launching from Earth, slingshotting around Venus and a remote Solar System body, then executing a maneuver at close Sun flyby. The label below the diagram reads "Oberth Kuiper Maneuver".] |
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| | ==Trivia== | | ==Trivia== |
| − | *In 2018, {{w|NASA}} launched a mission to the sun with a closest distance of only 8.5 solar radii. The {{w|Parker Solar Probe}} is using seven Venus flybys to reach its [http://parkersolarprobe.jhuapl.edu/index.php first close approach]. The maneuvers will last nearly seven years, before the real mission starts. | + | *{{w|NASA}} is planning a mission to the sun at a closest distance of only 8.5 solar radii. The {{w|Solar Probe Plus}} will use seven Venus flybys to reach its [http://solarprobe.jhuapl.edu/index.php first close approach]. The maneuvers will last nearly seven years, before the real mission does start. |
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| − | *{{w|Project Lyra}} is a proposed mission to {{w|Oumuamua}} using gravity assists from Earth and Jupiter to perform a sun flyby at 3-10 solar radii. With a 2030 launch suggested, it would then take the craft over two decades to catch up to the fast-moving body.
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| − | *Humorously, in real life [http://news.cnet.com/8301-1023_3-57495117-93/mars-curiosity-rover-team-prefers-macs-to-pcs/ a group of NASA team members "love" to play ''Kerbal''].
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| | {{comic discussion}} | | {{comic discussion}} |
| − | | + | [[Category:Physics]] |
| | [[Category:Comics featuring Cueball]] | | [[Category:Comics featuring Cueball]] |
| | [[Category:Comics featuring Ponytail]] | | [[Category:Comics featuring Ponytail]] |
| − | [[Category:Multiple Cueballs]]
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| − | [[Category:Astronomy]]
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| − | [[Category:Space probes]]
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| − | [[Category:Space]]
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| − | [[Category:Kerbal Space Program]]
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