explain xkcd - User contributions [en]

2148: Cubesat Launch

2025-12-03T15:26:22Z

Batbrain55: New category idea, since there are at least three comics with this specific premise and accidents are a recurring theme in general.

{{comic
| number = 2148
| date = May 10, 2019
| title = CubeSat Launch
| image = cubesat_launch.png
| titletext = Luckily, the damages were partly offset by the prize money we got from accidentally winning the nearby water skiing championship tournament.
}}

==Explanation==
A {{w|CubeSat}} (aka U-class spacecraft) is a miniature artificial-satellite with cubic dimensions of 10 cm × 10 cm × 11.35 cm (~ 4 in × 4 in × 4.5 in), and masses of about 1.33 kg (2.9 lbs) per unit. CubeSats are put into orbit from the International Space Station or launched as secondary payloads. As of January 2019, at least 900 CubeSats have successively achieved orbit, and at least 80 have been destroyed in launch failures. Their common functions include: Earth observation, amateur radio transmitters, as well as testing prototype small-satellite technology.

The comic begins with [[Megan]] telling [[Cueball]] that being officially part of a CubeSat launch is fairly expensive (starting at around $40,000),<ref>https://makezine.com/2014/04/11/your-own-satellite-7-things-to-know-before-you-go/]</ref> but she has an idea for a much cheaper alternative: use a fishing line on a drone to attach to a rocket (that is similar visually to the European Vega rocket) just before launch, with the CubeSat attached to the other end of the fishing line so it gets pulled into space.

In reality, this plan would fail for multiple reasons.

# Security would presumably prevent the drone from reaching the rocket.
# Even if Megan were to pilot the drone past security undetected, the launch would have been scrubbed as soon as any observer noticed the drone near the rocket and told Mission Control, who would order a countdown halt and stop the rocket launch, which prevents Megan from launching her CubeSat in the first place — after which Security would locate the drone's user and take her into custody.
# The drone would not be able to attach itself to the rocket in a way that would remain secure.
# The fishing line would not hold - either the rocket exhaust would sever it, or the force from the CubeSat, gravity, and the acceleration of the rocket would become more than its tensile strength could withstand.
# The unshielded CubeSat would likely be destroyed by aerodynamic forces.
# The comic shows the drone attaching to the lower part of payload fairing, a shell at the tip of the rocket protecting the satellites from aerodynamic forces in the early phase of the launch. The fairing is ditched as soon as practical and falls back to Earth, so the drone would never reach orbit.
# Precise weight is an important number during launch. The extra weight of the drone, the fishing line, the air drag from the drone, and the CubeSat all would combine to put more downward force on the rocket than planned. The rocket may be able to compensate for this unexpected extra weight, but if it can't, the rocket may find itself in a lower orbit than planned, or unable to reach orbit at all.

Upon realizing her plan, Cueball immediately responds with "uh-oh", indicating his concern, but Megan assures him that it will be fine, before piloting the drone towards the rocket. She successfully connects the drone to the rocket, and the rocket lifts off.

Whatever her plan was, it goes wrong almost immediately. The unexpected force on the rocket from the side causes it to tilt and go off course. Perhaps if the rocket's control software employed {{w|adaptive control}} techniques, it could have maintained control in the presence of this unexpected force. It is implied that it's not due to the comparatively small force of the CubeSat, but because Cueball is standing on the fishing line. However in real life the force from Cueball stepping on the line would still be very small and would be unable to cause a scenario like this. Megan and Cueball get tangled in the fishing line and are carried away. While the fate of the rocket is not shown, it is likely that its unplanned {{w|Attitude_control|attitude change}} would activate the automatic termination sequence or result in manual activation of the destruction protocol.

Megan and Cueball miraculously survive and are brought to an investigative board to explain their actions. Megan attempts to defend herself using flawed logic: something was bound to go wrong sooner or later, so it's not her fault that she was the cause. This logic does not account for the fact that this particular rocket's chance to crash was greatly increased by the drone attempting to connect to it. She isn't totally to blame for the accident anyways, since the launch should have been scrubbed as soon as the drone came anywhere near the rocket, and the failure of Mission Control to do so is negligence on their part, and hence they are more responsible for the failure of the mission than Megan and Cueball as they did not follow proper protocol and allowed the launch to occur under unsafe conditions.

The title text describes that the supposedly huge amount in damages they had to pay (for all the damage they caused) was partly covered by the earnings from a water skiing championship, which Cueball and Megan presumably won by being dragged across the water by the rocket. This might be a tangential reference to an incident in the {{w|The Adventures of Tintin|Tintin}} adventure ''{{w|The Black Island}}'', where {{w|Thomson and Thompson}} blunder into and win an aerobatics competition when they compel a mechanic with no flying experience into taking off in pursuit of that volume's antagonists. Alternatively, it may simply be a case of the title text being largely irrelevant to the comic itself and simply something Randall found funny.

This topic of CubeSats has been covered in older comics: [[1866: Russell's Teapot]] and in [[1992: SafetySat]].

==Transcript==
:[Megan is holding a cube attached by a string to a quad-copter drone flying above her head. She talks to Cueball standing next to her.]
:Megan: A spot on a CubeSat launch costs a lot, but you can get a drone and a spool of fishing line for cheap.
:Cueball: Uh oh.

:[A wide shot of Megan flying the drone with the cube at her feet while Cueball stand behind her looking after the drone that flies up to the left.]
:Megan: No no, watch.
:Megan: This is gonna go great.

:[Wide shot of a rocket standing on its launch pad with the support tower. The, now very small, drone is approaching, string attached, from the right.]

:[Slim shot of the rocket as the drone attaches to the rocket, just under the tip with the payload. The string goes down and out to the right.]
:Megan (off-panel): Perfect!

:[A huge cloud is emitted from the bottom of the rocket as it lift off the ground every so slightly.]
:''Foom''

:[As the rocket is taking off it begins tilting in the direction of the string. Two off-panel voices come from Megan and Cueball's direction.]
:Off-panel voice #1: Should it be tilting already?
:Off-panel voice #2: Hey, move your leg.

:[Close up of Megan and Cueball struggling in tangle of string that surrounds Megan while she is holding the cube in one hand and the remote for the drone in the other. Cueball uses both hands to try and help her out of the tangle. The string goes out to the left towards the rocket.]
:Megan: Ugh, let go, I can get-
:Cueball: -No, lift your ''other'' arm-

:[Three slim panels follow, one above the others, of the rocket, with string, tilting increasingly to the right and down as if pulled by the string. In the final panel of the three the tip of the rocket is now further than where the string goes down to the bottom of the panel. So, the string now goes back left from where it is attached to the rocket, rather than to the right as in all previous panels.]

:[Megan entangled in the string with the cube in her hand and Cueball hanging below her holding on to the string, are flying through the air, as the string goes up right, and with small lines drawn above it to indicate it is moving to the right. On the ground, Jill holds a hand to her mouth looking up at them, while a guy looking like Cueball runs away with hands over his head.]
:Megan and Cueball (screaming): ''Aaaaaa''

:[A disheveled looking Megan and Cueball both with plaster casts on their arms stand before four people, Hairbun, another Cueball like guy, Ponytail and Hairy. They are the members of an interview panel and are sitting behind a desk like table with a large label on its front:]
:Launch accident investigation board
:Megan: Listen.
:Megan: Space exploration is never going to be completely safe.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Jill]]
[[Category:Comics featuring Hairbun]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Hairy]]
[[Category:Multiple Cueballs]]
[[Category:Accidents]]
[[Category:Drones]]
[[Category:Rockets]]
[[Category:Space]]

3121: Kite Incident

2025-12-03T15:26:09Z

Batbrain55: New category idea, since there are at least three comics with this specific premise and accidents are a recurring theme in general.

{{comic
| number = 3121
| date = July 28, 2025
| title = Kite Incident
| before = [[#Explanation|↓ Skip to explanation ↓]]
| image = kite_incident_2x.png
| imagesize = 740x1610px
| noexpand = true
| titletext = Detectives say the key to tracking down the source of the kites was a large wall map covered in thumbtacks and string. 'It's the first time that method has ever actually worked,' said a spokesperson.
}}

==Explanation==
In this comic [[Megan]] is setting up a kite as [[Cueball]] arrives. Megan sets up the kite using a fishing line, which is unorthodox but not unheard of. Because the connection between the holding point and the lofted kite will form a {{w|catenary}} hanging down, after paying out sufficient line toward a kite increasingly far downwind, the line starts to dip and possibly touch the ground. Cueball suggests adding another kite at that point, after which they can then pay out more line and keep the line raised off the ground for additional distance.

They then get into a loop of adding more line to accommodate a stock of kites, and then more kites to support the line, until the kite chain reaches ludicrous proportions. The kites become so numerous and high-flying that they eventually blow in a circle around a significant part of the planet, following a {{w|jet stream}}. A circle on the surface of the Earth that follows the line of latitude where Randall lives is about 18,500 miles long, though a circumpolar jet-stream would curve into higher and lower latitudes to possibly add a lot more distance (as well as being at a higher altitude, which would add a more predictable fraction to its length). If the kites have been dragged into a much smaller circle as the result of a kite and/or its string getting caught by an airplane, there's no evidence of this to either the comic's characters or to ourselves, and travel purely by extensive (albeit slower) atmospheric movement has been [[2805: Global Atmospheric Circulation|featured before]]. Modelling the line as a straight line stretching 15 degrees above the horizon, Megan has spent over 38km of fishing line by the time the first kite reaches the jet stream at 10km high, but the mean separation of kites is possibly not particularly far, based upon the heights of the figures in wider shots, and Megan has lost count of how many they deployed, anyway. The curve of the hanging tethers would be highly dependant upon the tension between the two points of suspension, as would the ability of any given kite to fly, but there is not enough clear information to discern to what limits these (and the fishing line) might constrain the scenario.

The sirens in the second-to-last panel refer to a visit by some law-enforcement agency. The string of kites circling the Earth has interfered with international air travel. Although the mass of any given kite and the presence of such a relatively light and fragile tether should not cause too much difficulty for the majority of airliners if their wing or body collides with the kite-chain, the danger of a kite being ingested into the engine would ''preferably'' be avoided out of an abundance of caution. This is true even if the presence of kites is known to be not a more solid danger rather than a mystery and/or {{w|2023 Chinese balloon incident|perceived threat}} which can lead to {{w|Air travel disruption after the 2010 Eyjafjallajökull eruption|air travel to be shut down}}. (Of course, with xkcd physics, the pilots may have been concerned that [[2148: Cubesat Launch|snagging on the kite string would pull Megan and Cueball off of their feet]].) Regardless of the actual degree of danger, the authorities react accordingly, and events culminate in Megan and Cueball being forced to issue a formal apology. Having their lawyer there might indicate they won't get away with just an apology, but maybe this is to show they meant no harm, to decrease the penalty they will face.

The title text alludes to an investigation technique seen in many types of media where the investigator {{tvtropes|StringTheory|pins text and photo evidence to a board}}, connecting related evidence with string. This technique is also made fun of in [[2244: Thumbtacks And String]]. Though often good enough for fictional purposes, at least to the extent that the plot demands, the text indicates that real-world uses of 'string on a map' to discover a useful result have not actually been successful. But in this case, the string on the map would be there to indicate the actual extent to the string ''in the air'', probably from various reports received from around the world, and apparently it had successfully led to the discovery of the location from which the string originated on the ground and the subsequent intervention against the duo's excessive kite-deployment activity.

Kites have been a [[:Category:Kites|recurring topic]] on xkcd since the early days. It has been three years since the last comic featuring kites, [[2632: Greatest Scientist]], six years since Cueball put one up, in [[2208: Drone Fishing]], and 10 years since Megan did so, for [[1614: Kites]].

==Transcript==
:[Cueball approaches Megan from the left. Megan is flying a kite, with the line attached to a spool.]
:Cueball: Ooh, flying a kite?
:Megan: Yeah. I found this big spool of fishing line in a closet.

:[In a silent panel, Cueball and Megan are seen from further away, indicating that the kite is flying higher.]

:[Cueball and Megan are seen from yet further away, indicating that the kite is flying still higher.]
:Cueball: Are we allowed to fly a kite this high? Should we Google whether there are rules?
:Megan: Eh, it's probably fine.

:[The line held by Megan leaves her hand almost horizontally before curving up. Cueball stands a little way downwind his hand up to the string, above head-height, as if supporting/stabilising it or testing its tendency to stay up.]
:Megan: The string is really starting to sag.
:Cueball: Maybe we could attach another kite? I'll go get one.

:[A new kite is attached just above the line, supporting it higher in the air, Megan's held end now leading up to the point it is joined.]
:Cueball: It worked!
:Megan: Nice!

:[Megan is feeding out line from a partly depleted spool, via a peg/ground anchor, with a knot visible a short way up the rising cord. Two further empty spoole are seen on the ground. Cueball is approaching with a box.]
:Cueball: I bought another package of string.
:Megan: Oh good, these spools are almost empty.
:Megan: I think we're in the jet stream.

:[Three empty spools, one spool in use and one unused spool surround Megan and Cueball, with one supporting kite visible on the line that Megan is still feeding out.]
:Cueball: How many kites are on there now?
:Megan: I've lost count.

:[Another silent panel, zoomed out to see at least a half self-supporting "kite-length" about ready to have a new kite added at the ground end, and almost the same amount of curve leading off-panel to the next (previously attached) kite, unseen. There are flat items (presumably kites), spools (one being the current one being fed out) and boxes (assumed to contain more kite material and/or spools behind and around the two small figures.]

:[A much larger panel with the same ground details but a wider view. Above the ascending line of kites there is now a second, horizontal line of kites, dangling furves of connecting chord, leading from off-panel left to off-panel right.]
:Cueball: Uhh...

:[Some kites, spools and boxes are around the two figures, now seen again in close-up.]
:Cueball: ...Did it blow in a circle?
:Megan: I don't know. Lemme look at a map of where the jet stream goes.
:Cueball: Hey, do you hear sirens?

:[A CNN logo is at the upper right of the panel. Megan stands at a lectern, with Cueball on one side and Ponytail, holding a briefcase, on the other. An illegible news ticker is shown below them, along with more illegible text on either side of the panel, just above the news ticker.]
:[A banner with white text on a black background:]
:Breaking: Kite Incident Duo Speaks
:CNN
:Megan: On the advice of our lawyer, we would like to apologize for the events that shut down global air travel last week...

{{comic discussion}}<noinclude>
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Accidents]]
[[Category:Aviation]]
[[Category:Kites]]

585: Outreach

2025-12-03T15:25:58Z

Batbrain55: New category idea, since there are at least three comics with this specific premise and accidents are a recurring theme in general.

{{comic
| number =585
| date =May 18, 2009
| title =Outreach
| image =outreach.png
| titletext =Completely implausible? Yes. Nevertheless, worth keeping a can of shark repellent next to the bed.
}}

==Explanation==
Scientific animal tracking is commonly used to learn more about other species, particularly endangered ones, as a way of better understanding their physiology, behavior, and what risks they face in the wild. It's used in a wide variety of sciences, including wildlife biology, conservation, wildlife management and zoology. The scientists in this comic are working on a rather limited budget as [[Ponytail]] explains, say that they can't afford the (relatively minuscule) cost of hiring someone to retrieve a tracking tag from the water. Hence, they devise a plan that would actually cost far more: create one that will pop free, float to the surface, and inflate a giant helium balloon, causing it to gradually drift over land. Eventually, the balloon will slowly deflate and soft-land, and with any luck someone will find it and mail it back to the scientists. The shark is depicted much larger than the humans, and the quantity of helium necessary to lift it (as the later panels show) would be extremely expensive.

The plan has an unintended consequence: the tag fails to pop free from the shark and proceeds to inflate the balloon while the shark is still attached. Although the balloon is shown too small to lift the shark (a helium balloon can only lift approximately one gram per liter in air), the shark miraculously rises right along with the tracker tag, drifts back over land, and goes right after the scientists that had been tracking it. When [[Jill]] (in her first appearance) sees the two scientists running frantically from a flying shark, she figures that if such excitement is a daily part of a scientist's job, ''that's'' a job for her, as she tells [[Cueball]], her father. The title of the comic, '''Outreach''', refers to the type of activities that scientists do in order to motivate kids to become scientists when they grow up, and it clearly worked for Jill who displays keen interest and great knowledge on many subjects in her next appearances.

The title text suggests keeping shark repellent by one's bed to account for the quite-unlikely event of something like this happening. Because you never know. It may be a reference to the {{w|Batman (1966 film)|Adam West Batman film}} where Batman just happens to have some in his helicopter. In reality, a balloon meant for lifting a tracker tag would be much too small to lift the shark, which is portrayed as being larger than person, so there is no danger. In addition, since sharks are fish, and fish cannot survive for an extended period of time above water, the shark would die even if this could happen in real life. This doesn't stop movies like {{w|Sharknado}}, which was filmed after this comic, to portray sharks floating in the air.
The title text of [[1910: Sky Spotters]] seems to be a reference to this comic.

==Transcript==
:[Ponytail faces two Cueball-like guys. All three are wearing goggles and lab-coats. Between them on a shelf stands a microscope and a beaker.]
:Ponytail: The tracking tag will record the shark's movement and habits.

:[The capsule is shown to float upward towards a water surface.]
:Ponytail (narrating): Then, it will pop free and float to the surface.

:[A coast is shown, with arrows directed from water to land. A small white circle on one of the arrows indicate the balloon.]
:Ponytail (narrating): We can't afford a recovery program, so the capsules will inflate helium balloons, drift over land,

:[The capsule is shown in close up. It has a caption on it.]
:Ponytail (narrating): And hopefully be found and mailed to us. Any questions?
:Caption: If found please call

:[Ponytail is standing over a groggy shark on a boat, with water behind her and a coastline in the background. She attaches the tracking tag to the shark.]
:''Chunk''

:[The shark is dropped headfirst off the boat, into the water with a large splash.]
:''Sploosh''
:Shark: !!!

:[The course of the shark is shown, weaving around islands.]

:[The capsule is shown sticking out of the shark at the moment it is ready to pop free.]
:''Click''

:[The capsule remains attached to the shark.]

:[The balloon starts to inflate, still attached to the shark and underwater.]
:''Hissss''

:[As the balloon inflates, it starts to pull the shark to the surface.]
:Shark: ??

:[The balloon breaks the surface, pulling the shark with it.]

:[Jill, eating an ice cream cone is standing together with Cueball to the right in an otherwise empty frame.]

:[Two screaming scientists (A Cueball-like guy and Ponytail) runs past the two, who turns to look after them. The guy is holding the microscope and Ponytail the beaker from the first frame.]
:Scientists: Aaaaaaaa

:[A shark attached to a huge balloon floats past the girl and Cueball, it follows the scientists while snapping its jaws.]
:Shark: ''Chomp chomp''

:[After the shark is gone, Jill turns to Cueball.]
:Jill: Daddy?
:Cueball: Yes?
:Jill: I want to be a scientist.

==Trivia==
* This is the first xkcd comic featuring [[Jill]].
* This comic used to be [https://web.archive.org/web/20220125021918/https://store.xkcd.com/products/shark available as a T-shirt] in the xkcd store before it was [[Store|shut down]].

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Jill]]
[[Category:Multiple Cueballs]]
[[Category:Accidents]]
[[Category:Biology]]
[[Category:Science]]
[[Category:Sharks]]
[[Category:Comics with xkcd store products]]
[[Category:Comics featuring children]]