What is a Lyrae Anyway?

With the next update to comic still a week away, I thought I might fill the time with a short article about the spacecraft Lyrae-3 and others of its class. Specifically, about the name Lyrae itself.

The name “Lyrae” is a reference to a type of star called a RR Lyrae variable. These stars are one of several star classifications that exhibit a regular, predictable variation in the luminosity. In fact, the luminosity variation is so well understood that astronomers regularly use their apparent luminosity as seen from Earth as a way to measure the distance to distant star clusters containing them.

If this sounds interesting and you would like to know more about RR Lyrae variables in general, this wikipedia page should give a decent overview. The relevant information with regards to this webcomic is simply that the luminosity of an RR Lyrae variable changes over time.

The Lyrae-3 as seen in the comic sports two large radiator “wings” that glow brightly, varying according to the ship’s energy output. It is from these radiators that the name “Lyrae” derives. But why does the spacecraft have these radiators in the first place?

The Lyrae-3 as it appears in the comic.

Space is popularly said to be cold and this is not without justification. The Cosmic Microwave Background reads in the present day as a rather chilly -270°C. Despite this it is still quite hard to actually cool down in space, even without a nearby star beaming sunlight at you, because space is also empty. If you are floating in empty vacuum, you cannot shed heat via conduction or convection as there’s nothing around you to transfer heat to. The only remaining method of heat transfer is by radiation, which happens to be by far the least efficient and slowest method.

In a spaceship with any sort working engines, computers, life support or toasters, overheating is a more likely problems than freezing as the onboar equipment produces heat faster than it can naturally dissipate. Present-day spacecraft therefore come equipped with radiators to radiate waste heat as efficiently as possible. Of course, radiators onboard modern day spacecraft don’t glow nearly as brightly as the Lyrae’s. To the naked eye they don’t seem to glow at all. So why does the Lyrae constantly look as if its wings are about to melt?

The International Space Station. Radiators are arranged perpendicular to the solar panels. Source: NASA.gov
The Space Shuttle Endeavor with its cargo bay doors opened, exposing the radiator panels lining the inner surface. Source: NASA.gov

The answer comes down to the Lyrae’s ability to travel faster-than-light, or more accurately my attempt to avoid explaining its ability to travel faster-than-light. Rather than try to justify how the Lyrae is able to rip holes in the fabric of space to cross the interstellar medium, I elected to simply assume it could and worked backwards from there.

Bending space in any significant is something that is generally only done by really massive objects such as planets, stars and, for the really freaky stuff, black holes. So the Lyrae must have access to some incredibly powerful reactor technology in order to pull off its stunts, which has consequences for determining the limits of its other on-board equipment, including its cooling systems.

As a side note, this same logic leads to the strange realisation that the Lyrae’s maximum possible sublight acceleration, assuming it uses a large ion thruster or similar form of electric propulsion, is limited less by how much power can be pumped into the drive and more by how much stress the ship’s hull can take before the engine just rips itself out.

Thermodynamics basically forbids any sort of engine being 100% efficient and there will always be some percentage of energy lost as waste heat. When dealing with energies large enough to break holes in space itself, this percentage translates into a lot of heat. The fact that the Lyrae’s radiators merely glow rather than explode into vapour after giving everything in the nearby solar system a lethal dose of gamma radiation is probably an extremely optimistic portrayal.

Concept sketch of the Lyrae-class. While the craft’s overall layout is similar to the final design, there are numerous differences in weapon placement and design of the radiator arrays.

All of the above helpfully serves as a convenient in-universe cover for the real reason for the Lyrae’s glowing wings: I kinda just thought it looked awesome.

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