1244: Six Words

Explain xkcd: It's 'cause you're dumb.
(Redirected from 1244)
Jump to: navigation, search
Six Words
Ahem. We are STRICTLY an Orbiter shop.
Title text: Ahem. We are STRICTLY an Orbiter shop.

[edit] Explanation

The six words are: "It works in Kerbal Space Program".


Cueball is proposing to implement an "Oberth Kuiper Maneuver", and the proposal diagram shows the spacecraft using gravity assists to travel first towards (presumably) Venus for a first boost, then towards Jupiter for another swing by, aiming it back towards the 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.


Cueball's argument for why the maneuver will work in real life is that it works in Kerbal Space Program (KSP), a sandbox spaceflight simulator. While KSP does take into account quite a bit of the physics of space flight, it is (necessarily) simplistic in its modeling of orbital dynamics. KSP does not make any attempt to deal with the N-body problem (for which there is no complete solution), or even simpler 2-body mechanics. Instead celestial bodies are "on rails" and have fixed Spheres of Influence (SOI); a craft within a particular SOI feels the gravitational influence of only that body, and transitions are abrupt when a craft crosses the edge of an SOI. This means there are no Lagrangian points, Lissajous orbits, or, critically for this context, orbital perturbations by distant bodies or other factors. 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. KSP does however have a big modding community and one of its members has created a mod called Principia that implements an approximation of N-body physics by using numerical integration.

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.


Humorously, in real life a group of NASA team members "love" to play Kerbal.

[edit] Transcript

[Caption above the frame:]
The six words you never say at NASA:
[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.]
Title: Proposal:
Label: Oberth Kuiper Maneuver
Cueball: And besides—
Cueball: It works in Kerbal Space Program.

[edit] Trivia

  • NASA is planning a mission to the sun at a closest distance of only 8.5 solar radii. The Parker Solar Probe will use seven Venus flybys to reach its first close approach. The maneuvers will last nearly seven years, before the real mission does start.





strictly an orbiter shop








Slightly off-topic, but I just wanted to add this. You know how the ESA hosts their little Moon Mission competition and stuff? A theoretical mission to the moon whereby one researches and proposes a Moon Mission and writes out the mission details, although it won't actually happen, as far as I know. My college (well really, only me and one other girl) is collaborating with some other colleges in the US and some others from other countries (in total, 11 of us on one team) is participating in it. Part of the mission requirement is that we must be able to simulate the mission. Of course I read the details... and I absolutely died laughing when I read that Kerbal Space Program is officially a viable simulator for the "mission." I immediately thought of this comic, haha! I suppose you don't say it at NASA, but it's OK at ESA, I suppose! International Space Station (talk) 02:09, 9 October 2015 (UTC)

Kerbal Space Program

Made some adjustments to the section about KSP. Mostly just describing which limitations of the game would make it inappropriate for use at NASA, simulating a complex orbital trajectory. As a side note: in the full release they dramatically overhauled the drag modeling and re-entry dynamics, making it somewhat more realistic. There's also a fairly significant modding community that has offered improved realism via alternate atmospheric drag modeling, life support systems, drilling for fuel (now in the game-proper), and more realistic planet size/density/separation (the default settings have bodies ~1/10th the size of similar bodies in our own solar system, with very high densities, and relatively close together, resulting in comparable surface gravity but making it much easier to reach orbit and beyond in the KSP system). As far as I know nobody has looked at N-body simulation in KSP (while there is no general solution partial ones can be determined, and complete solutions exist for 2-body and a limited 3-body system). I think Orbiter had it to some degree, as you could make use of more complex orbits and Lagrangian points. I'd love to put a refueling station at the Kerbin-Mun L1 point. -- 22:01, 29 October 2015 (UTC)

My friend's dad took a tour of SpaceX recently and said the designers there use Kerbal Space Program extensively. Benjaminikuta (talk) 22:57, 25 December 2015 (UTC)

Has anyone tried this? I am trying, for one. That's right, Jacky720 just signed this (talk | contribs) 03:00, 21 February 2017 (UTC)

Personal tools


