Editing 2534: Retractable Rocket

{{comic
| number    = 2534
| date      = October 27, 2021
| title     = Retractable Rocket
| image     = retractible_rocket.png
| titletext = Hard to believe that for so many years once they were fully extended we just let them tip over.
}}

==Explanation==

This comic documents another of [[Beret Guy]]'s [[:Category:Beret Guy's Business|Business]] and [[:Category:Strange powers of Beret Guy|strange powers]]. He explains to [[Megan]] that "we" (possibly [[1997: Business Update|his company]]) are testing their new "retractable" rocket. 

{{w|Reusable launch system|Reusable rockets}} are a growing industry, as they are more economically viable in the long run &ndash; though technically much more difficult to operate &ndash; than rocket boosters that are just discarded after use (which have been standard throughout the majority of space-faring history). Thus, Megan is understandably confused about Beret Guy's assertion that theirs is "retractable", asking if he misspoke. In typical fashion, he assures her that he did not misspeak, with a single "No" without further explanation. 

They proceed to watch the rocket "launch", proving that it is indeed ''retractable''. In fact the rocket does not launch, but merely ''extends'' &ndash; apparently all the way to the {{w|International Space Station}} (ISS), a height of over 400 km (over 250 miles) &ndash; before retracting, as promised, to its original position. The top part, with the astronauts in it, has been left in space. Presumably, it is docked to the ISS, as the crew onboard the ISS say hello to them in panel 4.

Of course, it would not be possible to extend anything this far.{{Citation needed}} The top would need to be moving very fast compared to the bottom part, or it would bend westwards and break, and even with the strongest material a fully extended, very thin, presumably, hollow structure with a payload on top would {{w|buckling|buckle}} very soon after extension began. Also, the ISS moves at 27,600 km/h (17,100 mph) compared to the ground under it, making an orbit in about one and a half hours. So making the tip follow this long enough to dock would be even more impossible. 

Beret Guy's retractable rocket has more than a few similarities to a {{w|space elevator}} which has been discussed in real life. The chief difference is, a space elevator is only extended once (and most likely this would be down from space, not extended upwards), and never retracted unless it needs to be dismantled. Randall has referenced space elevators in [[697: Tensile vs. Shear Strength]]. A more similar theoretical means to attain orbit is that of the {{w|space fountain}}. He has also examined the problems of a solid metal object extending through the atmosphere [https://what-if.xkcd.com/157/ in a what-if].

The current method of sending rockets into space requires huge amounts of fuel, and the more fuel you attempt to carry, the heavier the rocket, leading to more fuel being required, etc. ({{w|Tsiolkovsky rocket equation}}), which makes the current method inefficient.  Alternate methods are being explored, such as using a slingshot ({{w|SpinLaunch}} had a successful test flight of a smaller scale launcher just days before this comic was published, probably the influence for this comic), theoretical {{w|space elevators}}, or this comic's impossible retractable rocket idea, all of which would leave the majority of the "fuel" requirements on Earth or elsewhere rather than having to carry heavy fuel with the rocket.  The only fuel carried might be minimal amounts for course adjustments once in space rather than large amounts used to get there.  However, many of these methods are less flexible than rockets; the space elevator, for instance, operates on the basis of constant angular velocity relative to the Earth's axis of rotation, meaning that it cannot launch payloads directly into low-earth orbit, polar orbits, or many other orbits frequently used by satellites for their desirable characteristics, and satellites intended for these orbits might still need to carry considerable amounts of fuel, even if less than that required to launch directly from the ground.

The title text parodies the 'old' single-use boosters. It appears that the predecessors to the 'retractable rockets' were capable of controlled extension only. Once they had lofted the payload to orbit, they were then allowed to fall over, destroying them in the process so they could not be used again just like booster rockets. However, if a 250 mile/400 km high construction just fell over, it would be much more difficult to avoid other damage, than to the rocket (booster), than for just a few small booster rockets falling out of the sky.{{Citation needed}}

This comic was released four days before (and possibly refers to) SpaceX's {{w|SpaceX Crew-3|Crew-3 mission}} to send astronauts to ISS with a reusable rocket on 31 October 2021.

==Transcript==
:[Beret Guy and Megan is talking. Behind them near the horizon is a tall rocket on a launchpad.]
:Beret Guy: We're testing our new retractable rocket.
:Megan: You mean reusable?
:Beret Guy: No.

:[A zoom in on the launchpad and rocket. It has the appearance of having a long first stage, a second stage with slightly wider fairing and an Apollo-style capsule with escape-tower atop it all. There is a directionless speech-bubble at the top depicting a count down voice.]
:Count down: Three...Two...One...Liftoff!

:[Same view as before, but while the base of the rocket-stack remains stationary, the first stage is apparently elongated, with a hint of a bend to the right, to raise the total height to which the upper-stage and capsule assembly reaches almost to the top of the panel.]

:[In a wider panel, with the base to the left, the first stage is now elongated far enough to disappear off the top of the center of the frame, thus clearly bending to the right. Two peoples voices are indicated as coming from the space capsule far above, as it reaches it destination.]
:Voice 1: Hi, welcome to the ISS!
:Voice 2: Hello!

:[The final panel shows the same view as in the third panel. The first stage is now retracting, and has similar length as in the third panel, but the capsule is no longer atop the 'second stage' fairing. Four movement lines above the top of the retracting rocket indicates that it is returning back to the original position.]

==Trivia==
*The [https://web.archive.org/web/20211028014542/https://xkcd.com/ original comic] misspelled "retractable" as "retractible". Has been documented on the web archive.
**This was done both in the [https://www.explainxkcd.com/wiki/images/archive/5/57/20211028040721%21retractable_rocket.png comic itself], and [https://www.explainxkcd.com/wiki/index.php?title=2534:_Retractible_Rocket&redirect=no the title]. 

{{comic discussion}}

[[Category:Comics featuring Beret Guy]]
[[Category:Comics featuring Megan]]
[[Category:Beret Guy's Business]]
[[Category:Strange powers of Beret Guy]]
[[Category:Space]]