My Very Healthy Obsession with Hexagonal Satellites
Hexagons are the bestagons. Of the many reasons why, a few that matter to me are:
- they stack well (read: honeycomb conjecture)
- bees love them 🐝
- they make for great screw heads (if you prefer Phillips head screws, you might want to consider getting yourself checked)
- snowflakes!
- carbon nanotubes
So it makes absolute sense that as a self-respecting engineer working on satellites (or other spacecraft), you would want your satellites to represent nature's GOAT of shapes and be hexagonal prisms.
And they have much to offer. When circumscribed for the same diameter, they offer better structural integrity than cuboids. More lateral panels mean that the spacecraft load is better distributed along six columns for the vertical axis (perpendicular to the hexagonal face).
They also offer a larger bottom deck and more lateral surface area to hold components, thereby easing the assembly process. This image of the CHEOPS spacecraft shows how clean it can be to assemble a satellite that is a hexagonal prism.
For a circumscribed diameter d and height h, the lateral surface area is
For a cuboid, that area would be 2.82dh. You could of course argue that a cylinder would offer you better odds at 3.14dh, but you lose time and money in machining and assembling a cylinder (apart from the space you waste when you realize your PCBs are still going to be flat).
PCBs (for small satellites at least) are standardized to approximately 10 cm x 10 cm or 10 cm x 20 cm cards. Which means that if you want octagonal prisms or dodecagonal prisms, you need to increase diameter size and make larger satellites to hold your cards on the lateral faces. Your choice really gets limited between cuboids and hexagonal prisms.
It is reasonable to assume that most imaging payloads are cylindrical, which means that the simplest way to provide good thermal environment and better stability can come from placing the payload axis along the vertical axis of the spacecraft (the axis perpendicular to the hexagonal bottom plate). The leftover space is then used to accommodate other satellite bus components (usually PCBs or stacks of PCBs).
Speaking from personal experience, space-optimization for satellite bus components on cuboidal satellites will force you to move your payload to the top deck of the satellite, leading to a top-heavy asymmetrical system which is horrible when you start to analyze for vibration. The hexagonal prism, being closer to a cylinder than a cuboid, does all it can to inscribe payloads of wider diameters along its central vertical axis, while still accommodating the satellite bus components.
Another advantage of hexagonal prisms as satellites is that they offer you more edges for more deployable solar panels, making the panels shorter and thereby keeping a check on the satellite's moment of inertia (less spread-out mass generally means lower moment of inertia).
And when you want to send more satellites together, hexagons stack better (this is not exactly true, you can always make satellites really flat and stack them on top of each other, see Starlink), saving you space as you get to space.
With that said, here are some of my favorite hexagonal satellites:
WorldView-4. Hexagonal perfection.
GeoEye-1. Bonus points for hexagonal secondary mirror (look at the obscuration).
FormoSat-2. A hexagon on top of a hexagon. Love seeing it.
KOMPSAT-5. A hexagonal prism SAR satellite. Now we're getting somewhere. Good job Korea (south)!
TeLEOS-1. Thank you Singapore, very cool.
TeLEOS-2. Another hexagonal SAR satellite! You've got to appreciate Singapore's commitment to the hexagon. Also see: DS-SAR.
Sentinel-5P. Yup, ESA's environment monitoring workhorse is hexagonal. So are Pleiades 1/2 and SPOT 6/7. Airbus knows their hexagons.
The upcoming NASA Roman Space Telescope, our next great space observatory.
Honourable mention:
The TIE series of starfighters. TBH, not exactly what I meant but it's got the spirit.
I will keep adding to this article as and when I get more data points. In the meantime, feel free to correct me if I'm wrong: mail@kshitijkhandelwal.com
Last Updated: 2024-11-01