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| Rejected Space Mission Profiles |
 Title text: Although NASA agreed that Voyager 2 'seemed lonely' they decided against launching a companion orbiter mission after further measurements indicated that the spacecraft actually preferred the peace and quiet. |
Explanation
This comic depicts four space missions which were supposedly rejected, because each would obviously be a bad idea.
The "Jupiter rover" mission depicts a Mars rover-like vehicle on Jupiter. As the rover is a wheeled vehicle, it can only operate on a body with a solid surface such as Mars. Jupiter is a gaseous planet with no solid surface. In addition, Jupiter has winds in excess of 1,000 km/hr, atmospheric pressures exceeding 1 million atm, and temperatures exceeding 24,000 K; any rover made with current technology and materials would be destroyed upon deployment; the Galileo probe specifically designed to penetrate the Jovian atmosphere was destroyed when the atmospheric pressure was approximately 24 atm.
The "Voyager 2 orbiter" mission would send a probe to orbit Voyager 2, which is itself a space probe. As Voyager 2 was built on Earth, its size, shape, and features were already well known to NASA before it was launched into space, making this mission pointless; it would also interfere with some of Voyager's own still-ongoing measurements of its current environment. Orbiting Voyager 2 would also be a non-trivial task. Voyager 2 has a mass of 722 kg and a minor axis of 2.5 m. Escape velocity for any unpowered orbit would be 0.68 m/hr, and the relative mass of the 'orbiter' is likely to form a binary system between the two objects. Trivial fluctuations in velocity would lead the co-orbiting pair to be unstable; these are unavoidable due to the asymmetry of the Voyager probe. Powered orbits would require non-trivial mass for station keeping. Not to mention that it would mean somehow catching up with with the second-furthest man-made object there is, which will have five or more decades of head start on any mission yet to be launched.
The "Crewed Pluto flyby" mission would send astronauts to pass by Pluto in order to collect scientific data about the minor planet. However, the mission as depicted would have the astronauts pass Pluto and continue out of the solar system, apparently with no way of returning to Earth. In addition, current timeframes for a Pluto flyby are on the order of a decade. Sustaining astronauts on such missions for years requires on the order of 1 kg/person/day. The entire mass of the New Horizon probe would be required each year for each astronaut. Due to the limits of the rocketry equation, this quickly exceeds the combined payloads of all space missions to date.
The "Neptune core return" mission would somehow extract the solid core deep beneath Neptune's gaseous atmosphere, then tow it back to Earth. The core of Neptune is estimated to be on the order of the size of the earth; any such towing out of the gravity well would require impractical amounts of energy. Additionally, the atmospheric pressure near the Neptunian core is estimated to exceed 100,000 atm and would again require significant advances in technology to survive descent to Neptune's core.
The title text extends the joke of the Voyager 2 orbiter, claiming that the project was scrapped because the probe actually prefers to be alone. Voyager is not sentient (although a successor to it become so, for the film Star Trek: The Motion Picture), so it doesn't actually have preferences.
Transcript
- [Caption above the panels:]
- Rejected Space Mission Profiles
- [Four panels in a 2x2 grid.]
- [Upper left panel:]
- Jupiter Rover
- [A Mars rover-type vehicle falls through the gaseous clouds of Jupiter.]
- Rover: AAAAA!
- [Upper right panel:]
- Voyager 2 Orbiter
- [A small probe is shown in an orbit around Voyager 2.]
- [Lower left panel:]
- Crewed Pluto Flyby
- [A diagram depicting part of the solar system, with the sun and four planets, probably Earth, Jupiter, Saturn, and Pluto, each with curves indicating part of their orbits. A dotted line shows the path of a spacecraft passing Pluto.]
- Voice from spacecraft: Uh, bye, I guess.
- [Lower right panel:]
- Neptune Core Return
- [A rocket is shown above the surface of Neptune. On two sides there are arms extending from the rocket. At the ends of the arms are cables connected to an enormous rock that's being pulled out of the planet.]
This Week's Explanation for Improvement
As part of the Explanation Improvement Project, each week the community selects one older, stagnant, or otherwise neglected explanation to expand and polish together. This week's pick is comic 430: Every Damn Morning, you can help us by editing its explanation!
To get involved with the project, you can also nominate an explanation that you think should be improved, or vote on current nominations!
| Every Damn Morning |
 Title text: There was something about a cup and a sword and a tree and a green hill... |
Explanation
|
Welcome to This Week's Explanation for Improvement! Anyone is encouraged to help explain comic 430: Every Damn Morning; click here to get started! If you are new to wiki editing, you can read our editing FAQ for guidance. Here are some suggestions for improving this explanation: .svg){kind=icon} Explain the various occurrences in the dream! Could they be references to other comics?
.svg){kind=icon} Why do humans forget their dreams so quickly?
.svg){kind=icon} Improve the #Transcript, it's not descriptive enough.
|
Cueball has had a wondrous and striking dream (seemingly involving various action-packed escapades with Megan and/or on board a Zeppelin), including, among other things, a swordfight and a nuclear detonation, but is unable to recount it to Megan, as he has forgotten it.
The title of the strip suggests that this is a regular occurrence: he wakes up with vivid memories of elaborate and fascinating dreamscapes, but is unable to tell anyone about it, because the memories fade so quickly, he's lost almost everything before he gets the chance. The title text is a reference to C. S. Lewis's novel The Voyage of the Dawn Treader, in which Lucy Pevensie reads a story that “refreshes her spirit” – “That is the loveliest story I’ve ever read or ever shall read in my whole life. Oh, I wish I could have gone on reading it for ten years.” – but afterwards can only remember that it had something to do with "a cup and a sword and a tree and a green hill."
The various things in the dream have references to other comics. Zeppelins were seen before in 73: Zeppelin and 288: Elevator, and continue to be a recurring theme in xkcd.
An effort to remember dreams was made in 269: TCMP.
Transcript
- [In the background, a vivid dream scene is apparent, including mountains, a city with a mushroom cloud, a Zeppelin where one person has knocked another off, another person climbing on or off the blimp on a rope, another blimp anchoring to a city in the background, one Cueball and Megan holding hands, one Cueball looking at the person on the rope, one Megan using a sword to pin down a Cueball over a cup of spilled liquid, another set looking at a laptop, another set hugging, another set sliding down a separate rope from the blimp and a last set falling. In the far right there is a third blimp flying over a mountain range. All in all, this seems very much like an apocalypse and not something one would forget easily. In the inset, Cueball awakens, very surprised.]
- Cueball: !!!
- [Dream's edges are fading, mountains, city, and Zeppelin less clear. In the inset, Cueball is seen running down stairs.]
- [Zeppelin, city, and mountains are very hazy and unclear. The people can still be seen. In the inset, Cueball gets the attention of Megan, who is sitting at a breakfast table.]
- [The dream has completely faded, only the outlines of three people can still be seen. In the inset, Cueball looks confused.]
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