3291: Launchpad
| Launchpad |
 Title text: It does come at the cost of some launchpad expansions and increased fuel requirements, but that all comes out of the facility's budget. |
Explanation[edit]
This comic is about launching a spacecraft into space, seen as a problem of separating the spacecraft from the Earth. Traditionally this is done by accelerating the spacecraft away from the Earth using a rocket, but in this comic it's done by accelerating the Earth away from the spacecraft. Instead of the rocket engines being part of the rocket, the engines are mounted upside-down on the launch platform, and by extension, on the planet Earth itself.
Even from a purely theoretical perspective this is difficult to achieve: the exhaust of the engines would be in Earth's gravitational field and thus be slowly pulled back towards it. According to Newtons's Third Law this would, in turn, cause the exhaust to pull the Earth backwards too, negating any thrust generated by the engines. To prevent this, the speed of the exhaust would have to exceed Earth's escape velocity (11.2 km/s), but neither solid fuel (2.5 km/s) nor liquid fuel (4.5 km/s) rockets do so. The presence of Earth's atmosphere exacerbates this: The interaction of the exhaust with the stationary atmosphere would dissipate the energy of the exhaust, lowering the speed of the moving gases. This means the engines would have to exceed the escape velocity by a lot to be able to generate any thrust.
Ignoring this, there would still be literally massive practical problems. Three main issues come from the same underlying fact: The Earth has a lot more mass than a typical spacecraft.[citation needed] This means that the engines would need to produce gigantic amounts of force, even by rocketry standards, to accelerate the Earth away from the spacecraft.
Firstly, the structural integrity of the object experiencing the force (both the rocket engine and the ground) would be concerning, given the amount of force needed. Even if the Earth could be moved away from the spacecraft, the spacecraft would be directly in the exhaust stream of the (extremely powerful) engines, which is likely to immediately incinerate it.
Secondly, the spacecraft would be unlikely to actually lift off the Earth if the planet were somehow moved, as the Earth's gravity would keep it in place; the Earth would need to be accelerated at more than one g (one gravity) to separate it from the spacecraft, causing widespread destruction to everything on the planet. In addition to the spacecraft, every other untethered object in approximately the same hemisphere would also separate, including the atmosphere. To what extent the spacecraft would ever be in space is debatable.
Thirdly, the rocket itself would still need some form of propulsion for maneuvering in space, so it would not completely remove the requirement to have some form of propulsion attached to it. (In multi-stage rocketry, the propulsion for use in space remains attached to the remaining part(s) of the rocket even after the first and heaviest element(s) of the rocket used to get out of the atmosphere are jettisoned to save weight once no longer needed. Nothing in the comic says that maneuvering thrusters and propellant are not present in the capsule, though one could also imagine the xkcd scenario keeping similarly supersized thrusters on Earth, somehow further maneuvering the planet beneath the free-floating capsule.)
The title text further ridicules the situation. Costs in an organization are sometimes split between different budgets. In a space launch organization, each launch might have its own budget, with a separate budget for the launch facility that's shared by the projects. In this comic, Cueball is, in effect, saying that one shouldn't worry about the project's budget paying for moving the Earth, since the cost will come out of the facility budget. This assumes, amusingly, that the facility's budget will somehow cover the cost of physically moving the Earth. Of course, not only would it be unlikely anyone would have the budget to deal with this elaborate scheme, but it is also unlikely there would be enough resources, full stop, to generate the power needed to move the Earth. Possibly the facility is linked in with Beret Guy, which would make the venture more probable, given his history of making bizarre things work.
The comic 1366: Train demonstrated a similar Earth-moving principle; with the exception being that this other example could be considered feasible, albeit by adopting an unorthodox frame of reference.
Transcript[edit]
|
This is one of 34 incomplete transcripts: |
- [Two giant twin engines are sitting on the ground pointing downwards, with a pod in between them. A Megan and a Ponytail are to the left of the first one, with a Cueball carrying something to the right of the thruster. Another Cueball is pointing to the pod from the right, talking to another Ponytail, and there is another Megan on the right side of the right thruster.]
- Second Cueball: To reduce the spacecraft´s weight, we´re mounting the engines on the launchpad and having them push the Earth away from the spacecraft.
Trivia[edit]
This comic is very similar to a 2016 Buttersafe comic where Jolly Octopus successfully pushes the Earth away from Saddest Turtle in this same manner.
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Discussion
This is very similar to a Buttersafe comic where Jolly Octopus pushes the earth away from Saddest Turtle in this very same manner. Xkdvd (talk) 19:34, 28 August 2026 (UTC)
- Here it is! https://www.buttersafe.com/2016/04/28/time-for-takeoff-saddest-turtle/ Xkdvd (talk) 21:16, 28 August 2026 (UTC)
Liquid-fuel cryogenic engines or nuclear pulse propulsion? Either way, this seems an excellent way for Planet Earth to enter the Twilight Zone. 205.175.118.2 20:02, 28 August 2026 (UTC)
- Nuclear Pulse might work but no chemical rocket has the isp. The article also seems to get escape velocity wrong, it’s 11.2km/s not 7.6 iirc Bubli (talk) 20:12, 29 August 2026 (UTC)
This is a mass driver. KSP style rocket based mass driver.Xurkitree10 (talk) 22:03, 28 August 2026 (UTC)
"...but that all comes out of the facility's budget." - To me, this was by far the funniest part of the comic. I interpreted this as one department (Engineering) coming up with a ridiculous solution to a problem because the cost of implementing it comes out of another department's (Facility/Operations) budget. They are just blithely tossing the cost of moving the Earth over the fence. 75.112.204.110Pat
Isn't there an additional issue not mentioned in the current description, that usually spacecraft have a specific destination other than "away from the Earth" which this scheme wouldn't help them reach? 2A0D:5600:8:308:0:0:0:17 23:48, 28 August 2026 (UTC)
- It does not appear to have been considered but now you can consider fancy orbit maneuvers. If you accelerate the earth in the direction of its orbit. The earth will go into a higher orbit and slow down. The spacecraft will follow but lose ground until the earth gravity is relatively weak and effectively decouple. Then, if that isn't enough, since you have infinite (imaginary) fuel you could bring the earth around next orbit and slingshot it faster/higher. Lordpishky (talk) 21:02, 29 August 2026 (UTC)
Getting to space is so expensive that even a partial ground based propulsion system would likely drastically reduce the cost of space travel. A short barrelled space gun might be one of the least practical ideas due to the forces applied to the payload (compared to an elevator or loop), but the worst part of the proposed idea is still that it's accellerating the wrong object. Mneme (talk) 10:54, 29 August 2026 (UTC)
"...causing widespread destruction to everything on the planet" - sounds like it'd be a feature if applied to a What-If comic! Esp666 (talk) 00:24, 29 August 2026 (UTC)
Am I the only person who thinks 1366: Train is relevant here? 2601:189:8502:5C00:E7E4:1F5F:E6C0:181D 12:59, 29 August 2026 (UTC)
I'd note that 7.6 km/s is orbital speed -- escape velocity is 11.2 km/s. 185.242.6.70 09:19, 29 August 2026 (UTC)
All launch windows are scheduled for opposite day/night launches to prevent global warming from being exacerbated... or reversed. 174.134.128.173 07:43, 30 August 2026 (UTC)
Having the power source attached to the ground is the real idea behind SpinLaunch, mass drivers, laser propulsion and space elevators. 2A00:23C7:F7BC:BC01:7410:7CC5:52BB:221A 12:08, 4 September 2026 (UTC) Add comment