2804: Marshmallow

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Marshmallow

Title text: The increasing number of graham crackers and chocolate bars in orbit has created a growing risk of Kessler s'mores.

Explanation

This comic shows the atmospheric re-entry process of a capsule similar to that used in the Apollo moon landing program in the late 1960s and early 1970s. This capsule features a fictional Reentry Marshmallow Toasting Module, with a marshmallow on a deployable stick, which is exposed to airflow during reentry.

During reentry, the capsule would presumably be going at orbital speeds, which for Earth are in excess of 8 km/s. This high velocity leads to air in front of the capsule compressing and heating up as it absorbs its kinetic energy (see Atmospheric entry for more details on ways of heating at work). This has the effect of heating the marshmallow. Additionally, reentry heating effects typically look like flames covering the bottom of the reentering object. This is very similar to a common practice on the Earth's surface of holding a marshmallow on a stick over a static fire on the ground, like a campfire, which also heats the marshmallow, improving its taste.

At the start of the panel, the capsule is approaching atmospheric entry, so any aerodynamic forces would not have begun yet. "All systems nominal" is an aerospace phrase that means all systems (including life support, navigation and stability systems) are performing as expected. However, once the atmospheric effects begin then something goes wrong.

Having a long, thin extension to the airflow will disrupt the aerodynamics, as air starts pushing up against the roasting stick, creating an unbalanced torque that pushes the marshmallow further back into the airflow, rotating the entire capsule. This angular acceleration continues until the aerodynamic design of the rest of the capsule plays a significant factor, rotating the capsule back to its original position, and starting the uncontrollable cycle of oscillations anew. Hence, the astronaut on board reports some oscillations to Houston.

This prompts the unnamed astronaut to tell their colleague, Smith, to put away the marshmallow roaster. This would clean up the aerodynamic profile and stop the oscillation. This is met with resistance that the marshmallow is not cooked yet. This may be expected, as due to the design of the module, it appears as though the marshmallow has been on the outside of the capsule for the entire journey, exposed to the vacuum of space. In this situation, it would have radiated all its heat energy away, reaching temperatures near absolute zero (approximately -273.15 degrees Celsius, the absolute coldest temperature physically achievable). A very brief moment of shock heating from atmospheric effects may not have bought the marshmallow up to a consumable temperature, or even affected the internals of the marshmallow at all. The goal of roasting marshmallows is often to melt the inside of a marshmallow completely, so if this is still frozen, that defeats the entire purpose of the module.

"Houston" is the radio callsign for NASA Mission Control, located in Houston, Texas. During reentry, the superheated air forms a plasma phase and disrupts radio signals. Hence, it is doubtful that Mission Control would have received this communication from the capsule, and it is very unlikely Mission Control would have received further updates from the capsule until the reentry process was largely finished. This would make the Mission Control operators very concerned over the success of the reentry. But as orbital mechanic and spaceman extraordinaire Scott Manley has discussed the feasibility of roasting a turkey by dropping it from space (and Randall has himself addressed the issue of cooking steaks), the astronauts featured in this cartoon are not straying too far from accepted marshmallow roasting techniques and should not be reprimanded by NASA.

The caption for the panel muses that maybe the concept of the module was a mistake, which is a fair assessment given the number of flaws in the design. It would indeed be far better to have two such units, set upon opposing sides of the module and operated in conjunction, to balance rotational forces. Or even three of them, set 120° apart from each other, perhaps automatically and independently actuated to tune out all other undesired aerodynamic effects – with the added advantage of simultaneously preparing snacks for all three of the astronauts that typically inhabit an Apollo capsule, not just Smith. However, if there is no way to retrieve the marshmallows without exiting the capsule, they would likely be somewhat salty and waterlogged after the time the capsule splashes down and the astronauts can "enjoy" their cooking.

The title text refers to a popular snack of s'mores, made by placing a marshmallow roasted over a fire with some chocolate between two Graham crackers, similar to a sandwich. It also refers to a problem in rocketry, known as Kessler syndrome. Kessler syndrome is a scenario where the density of space junk in low Earth orbit is so high that pieces of space junk crash into each other, breaking apart into smaller pieces. This increases the amount of space junk in orbit, setting off a cascade that could render low earth orbit unusable. These two concepts are combined in a ridiculous way, whereby instead of space junk, it is Graham crackers and chocolate bars that are polluting space. These, combined with the marshmallow from the toasting module, would create celestial s'mores, a novel and frankly wacky concept, as the United States space program does not primarily consist of chocolate and Graham crackers.^{[citation needed]}

Transcript

[A space capsule beginning reentry into Earth's atmosphere is shown. There are four versions of this as it moves deeper and deeper into the atmosphere, but shown in a single panel.]

[The first version is shown to the left with just a bit air resistance shown with thin dotted lines around and behind it. The capsule looks pretty standard with the broad bottom with the heat shield pointing forwards, and the capsule above it narrowing in a pyramid shape. There are a circular shapes (windows?) and some other lines indicating either doors or access panels. The one special feature is on the left, a stick is held back along the edge of the capsule from a extrusion near the bottom of the capsule. At the top of the stick a white square is located. From inside the capsule one of the unseen astronauts is speaking, possibly with ground control. All speech texts are located in rectangular frames with jagged arrows pointing towards the capsule.]

Astronaut voice: We're approaching atmospheric entry.

Astronaut voice: All systems nominal.

[In the second version air resistance has increased a lot, with many more and thicker lines indicating the air resistance. At this point the arm with the white square turns on its pivot so it is now sticking straight out from the capsule far outside the heat shield below. Two lines indicate the circular movement and the release of the stick makes a loud noise:]

Fwip

[In the third version air resistance continues to increase, but now also the stick and particular the white square at the end begins to heat up, smoke coming of from the white square. Two small lines on either side of the top of the capsule indicates it is shaking.]

[In the forth version the air resistance is about the same, but there are now six larger lines at the top of the capsule, two on either side and two above indicating more violent shaking of the capsule. The white square on the stick seems to be burning.]

Astronaut voice: Houston, we're experiencing some oscillations. Vehicle is becoming difficult to control.

Astronaut voice: Smith, retract that stupid arm.

Astronaut Smith's voice: No! It's not ready yet!

[Caption below the panel:]

In retrospect, the reentry marshmallow toasting module was a mistake.

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Discussion

Made a start, not sure if the heating up science is completely correct though MrCandela (talk) 13:54, 19 July 2023 (UTC)

Because I'm a nitpicker, I kind of want to see some mention in this blurb about how reentry is usually a communications blackout period, due to the plasma sheath blocking all radio waves and so talking with Houston *during* reentry is unrealistic. I strongly suspect Randall knew this, though and ignored it for the sake of the joke. Trimeta (talk) 14:08, 19 July 2023 (UTC)

In the case of the space shuttle it was possible to circumvent the problem of radio blackout by relaying the radio through satellites (the plasma blocks the radio waves downwards, but there was be a window upwards). https://en.wikipedia.org/wiki/Communications_blackout#Spacecraft_reentry Rps (talk) 15:39, 19 July 2023 (UTC)

The current explanation suggests that Mission Control would be concerned by the lack of communication from the capsule, but given that they would be aware of the effects of reentry, there's no particular reason why this should cause them concern.141.101.99.134 15:58, 19 July 2023 (UTC)

Some things that should probably be added: The comic was likely published in anticipation of the 54th anniversary of the first moon landing on the 20th of July 1969 In reality, the marshmallow, exposed to the vaccum of space, would expand due to the internally trapped gasses until its structural integrity failed https://youtu.be/MYAmPRQ4eWo?t=285 The title text should probably direct reference to Kessler syndrome, in which a single collision of orbiting objects causes a chain reaction filling low earth orbit with debris, in this case, tasty stacks 162.158.155.71 14:30, 19 July 2023 (UTC)

The phrase "rapid unplanned disassembly" in the explanation of the Kessler syndrome, however, is inspired! RAGBRAIvet (talk) 11:02, 20 July 2023 (UTC)

IMO, "Reentry Marshmallow Toasting Module" refers only to the Marshmallow arm and any necessary associated parts (covers, actuators, etc.), not the whole spacecraft (as the way it is currently written suggests). That is, as for instance, Apollo had a command module, a service module, etc.(?) in this case, there is this extra module. I think it is not unusual to have experiments or sensors piggy-backing in a existent spacecraft or probe. Rps (talk) 15:55, 19 July 2023 (UTC)

Agreed - I'd just amended the article to that effect before coming down here and reading this. :o) 141.101.99.134 15:59, 19 July 2023 (UTC)

"the marshmallow has been on the outside of the module for the entire journey, exposed to the vacuum of space. In this situation, it would have radiated all its heat energy away, reaching temperatures near absolute zero" I think this is incorrect: the side of the spacecraft in the shadow gets quite cold, although probably not ~3ºK (cosmic background temperature), since in low-earth orbit you have a warm body (the Earth) radiating some heat some (most?) of the time. But the sun side gets quite hot. Apollo used "Passive Thermal Control" (informally, it was called “barbecue roll”) to even out the temperature. Rps (talk) 16:11, 19 July 2023 (UTC)

I wonder if Randall played Outer wilds recently. Fabian42 (talk) 17:00, 19 July 2023 (UTC)

I don't think the specific choice of graham crackers is a reference to anything scientific. That's the usual cracker used to make s'mores. Barmar (talk) 02:35, 20 July 2023 (UTC)

I completely agree. I'm sure that the S'mores Randall is familiar with would have been made with Graham crackers and that's what he's referring to. MAP (talk) 04:46, 20 July 2023 (UTC)

I had to look up s'mores. I don't think they are common in the UK.--172.70.251.40 15:04, 20 July 2023 (UTC)

Also agreed, graham crackers are the normal recipe for s'mores, there's no reason to expect any reference to Graham's number. I'll remove that from the explanation.PotatoGod (talk) 05:05, 20 July 2023 (UTC)

An Apollo capsule returning from a lunar mission would be traveling at approximately escape velocity. If you think about it, how would it lose all the velocity it gained falling from lunar orbit, except by atmospheric friction? (Luna is at approximately infinity in terms of velocity needed to reach L1. Nitpicking (talk) 02:55, 20 July 2023 (UTC)

Space is not zero kelvin, the CBC is some degrees above that. Also as we are close to the Sun and Earth, and the marshmallow might have been exposed to sunlight/Earth light so there is no reason to believe it is frozen. But any water could have evaporated. Furthermore it may have been deployed from inside shortly before reentry. It looks normal in the picture, so it could be presumed it is a fresh marshmallow only just put outside when reentry begins. --Kynde (talk) 13:07, 20 July 2023 (UTC)

And, contrary to current explanation (indicating that it'll end up salty and wet), the de-deployment process might allow the snack ...once 'done'... to be brought back in whilst still undergoing descent (perhaps once they're on 'chutes). But I definitely think there should be three such equidistant modules, for a more fair/timely availability of snacks. ;) 172.71.242.190 14:51, 20 July 2023 (UTC)

AT 8 km/s, once they hit the atmospheric interface, how long would Smith reasonable have before the marshmallow (then the stick) were instantly vapourised? I'm guessing maybe 5-10 seconds. I've always said that good timing is essential to good cooking. 172.68.66.60 01:56, 21 July 2023 (UTC)Beechmere

I have to mention this prior art on atmospheric reentry marshmallow toasting, and I regret to say Randall's idea is inferior, because this one has cats: https://www.youtube.com/shorts/LKb5LjZTEYY 172.71.178.64 07:24, 21 July 2023 (UTC)