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The Wrong Stuff
The phantom found Edward Everett Hale a century too early; by the time we invented satellites, the specifics of his 'brick moon' proposal were dismissed as science fiction.
Title text: The phantom found Edward Everett Hale a century too early; by the time we invented satellites, the specifics of his 'brick moon' proposal were dismissed as science fiction.


Ambox notice.png This explanation may be incomplete or incorrect: Created by a TRAIN MADE OF 1977 SOVIET URANIUM - Please change this comment when editing this page. Do NOT delete this tag too soon.

Multiple times in history, there have been incidents where companies, governments, and engineers have proposed or developed plans for large vehicles composed of unconventional materials. One example is Project Habakkuk (mentioned in the comic), an aircraft carrier which was to be composed of pykrete, a mixture of wood pulp and ice. The comic imagines that all of these proposals are linked together by a single "Material Phantom," a ghost which haunts engineers and convinces them to design giant vehicles made of impractical materials.

The three "wrong material vehicles" mentioned in the comic are:

  • The Spruce Goose - An actual flying boat made, in spite of its name, almost entirely out of birch wood. Most modern planes are constructed out of aluminum, some other metal/alloy or (partially) out of carbon / glass fibre composites (CFRC / GFRC). Notably, despite being built out of the "wrong" material (due to wartime restrictions on aluminum usage, the use of birch wood was the next best option) the plane did make a single 26-second flight in 1947 before production halted due to the end of the war. The plane is currently on display at the Evergreen Aviation & Space Museum in McMinnville, Oregon, United States. More notably, other wooden aircraft of that era, such as the De Havilland Mosquito, were wildly successful, strongly indicating that the Goose's problem was not that it was made of wood. Many early planes made use of wood in their construction, and the skills and knowledge to build an airframe of that kind were still readily available in that era, in a way that they might not be today.
  • Project Habakkuk - A proposed aircraft carrier whose hull was to be made out of pykrete (a mixture of wood pulp and ice). It would have had several advantages had it been built when it was supposed to be (1943): it would have been able to guard the vital wartime North Atlantic supply routes between the USA and United Kingdom, as it would have been a base for fighter and reconnaissance missions; it would have been able to be easily camouflaged as an innocuous iceberg, and it was both stronger than steel (which the Mythbusters proved in a 2008 episode) and did not require voids between the structural elements in order to be buoyant (so could absorb a lot of damage and cannot spring leaks). The only reason it was never fully built was because it wasn't much cheaper than traditional steel-alloy hulls, from which ships continue to be built today, given that large quantities of metal were still required for the refrigeration units (although the abandoned prototype itself lasted for several years before it finally melted). There were also now airfields available to use in various Atlantic islands that could close the air-gap in coverage without having to (effectively) build their own floating island from scratch.
  • Trojan Horse - A mythological, giant wooden horse, supposedly used by the Greeks to invade the city of Troy. Actual horses are composed, like any other animal, out of meat, bone, and other tissues and bodily fluids.[citation needed] In addition, the interior of the Trojan Horse was composed of Greek warriors rather than horse innards.

The title text references Edward Everett Hale's science fiction novella The Brick Moon, the first known depiction of an artificial satellite and a scientifically-accurate GPS system in fiction. The novella is, of course, just a sci-fi story,[citation needed] but the title text states that Hale was actually approached by the Material Phantom, and the novella was a serious proposal for a moon made out of bricks.

The title "the Wrong Stuff" is a play on The Right Stuff, a book/movie/TV series about the pilots engaged in U.S. postwar research with experimental rocket-powered, high-speed aircraft and the astronauts of Project Mercury. In that title, "the right stuff" refers to the figurative material that these men were made of which gave them the bravery to embark on these missions.


This comic was uploaded with the "the" in "the Wrong Stuff" being entirely lowercase, breaking the normal title case used for XKCD comic titles. Possibly another word was initially intended to come before "the", in which case lowercasing "the" would be correct. xkcd displays lowercase letters in titles with small caps, making the lowercase "the" less obvious than it is in the true lowercase used on explainxkcd.

However, it's worth noting that the comic title has since been changed to "The Wrong Stuff," with "the" capitalized as per standard title case.


Ambox notice.png This transcript is incomplete. Please help editing it! Thanks.
[A ghost is approaching Cueball in a workshop. They are surrounded by shop equipment, such as a table with a press on it, and a small pile of what appears to be lumber. Cueball is backing away from the ghost, holding his hands up defensively.]
Ghost: oooOOOOOOoooo
[The "ooooo"s of the ghost are written in wavy letters of varying sizes]
Ghost: Build a spaceship out of bricks!
Ghost: oooooOOOOOOOOoo
Cueball: No! Go away!
[Caption below the panel:]
The Spruce Goose, the Project Habakkuk Ice Ship, and the Trojan Horse were all work of the Material Phantom, a ghost that wanders the Earth convincing engineers to make giant vehicles out of the wrong stuff.

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