Mun Farside Surface Relay CHALLENGE!

[Sky Vagrant]

The farside of the Mun is where most of us learn about comms relays - usually the hard way! It's easy enough to send a few sats to orbit the Mun and provide good relay coverage for the farside, but you could also land a network of relays to do the same thing at far greater cost!

So why would you want a series of relays on the surface of the farside of the Mun? Well, as the analogy for the Earth's Moon, let's assume that stable orbits are a problem we want to work around, There's also the station-keeping that all real sats need to do with limited fuel. So there could be a real-world application if it could be done practically (which is doubtful with the cost and difficulty of landing).

Here's my example of one such farside surface relay network:

Spoiler

While I had fun doing these missions, I figured that others could do it better and I want to see that! I want to see your awesome deployers and your crazy comms towers.

The basic challenge is fairly simple: create a Mun farside surface relay network that provides continuous contact (while behind the Mun) between Kerbin and a vessel in Mun orbit with an apoapsis below 15 km. You only need to do an equatorial relay network - i.e. you don't need to cover high inclinations. Land the network, post a pic or vid demonstrating that you are communicating through the surface relays, and claim your patch! One caveat, "Occlusion Modifier, Vac:" must be set to the default (0.90) or higher. (This is a setting from the start new game menu under the advanced game difficulty settings, so if you didn't touch those in your current game then it should be fine.)

Now for some additional competition parameters!

• Most Hops Trophy: awarded for the vessel with a periapsis above 10 km that takes the most Mun surface hops to communicate back to Kerbin. You can set "Occlusion Modifier: Vac:" as high as you want for this challenge, but let us know what you set it to. Your network still needs to meet the criteria for the basic badge (i.e. must cover the entire farside for orbits above 10 km). Given that you will be able to communicate through a significant portion of the Mun's crust, the challenge will be in figuring out how to position the relays and your orbit far enough apart to force more hops. This is about the opposite of efficiency!
• Big Dropper Trophy: awarded for the mission that deliveries the highest number of landed relays deployed by one lander/skycrane (without resupplying the vessel with additional relays)
• LoS Decoration: Build a realistic line-of-sight (LoS) Mun farside network. The game might not make use of all your relays, but show us how they have LoS around the Mun. Set "Occlusion Modifier: Vac:" to 1.0 or higher in the advanced game difficulty settings (new game start) and then create a functioning surface relay network. Anyone that does this gets the basic patch with a special decoration for their achievement.
• Realistic Relay Trophy: Design the most realistic relay station. Stations on the real Moon would have to contend with high and low temps, would need to be low mass but very stable, and would need a realistic power source.
• Extra-Kerbin Decoration: Build a surface relay systems outside of Kerbin's SOI to either communicate back to Kerbin or to the primary body (e.g. Ike farside to Duna). Anyone that does this gets the basic patch with a special decoration for their achievement. For surface relays on bodies with atmospheres, the "Occlusion Modifier, Atm:" must be set to the default (0.75) or higher.

I'll make the trophies and decorations if anyone earns them - or others could make them up if they don't like my patch. (This is the first challenge I've created, so please provide feedback and I'll add and adjust as needed.)

Edited August 24, 2020 by Sky Vagrant
Changed size of patch image, added occlusion rules

[vyznev]

FYI, something I realized while planning a similar challenge on Kerbin (which I really should post one of these days): the occlusion factor in the advanced difficulty settings panel (there are actually two — for the Mun, the one that matters is obviously the one for airless bodies) makes a huge difference — and, due to the way the math works out, it makes the most difference when the value is very close to 1.

Basically, setting the occlusion factor to 1.00 means that you essentially need a line of sight between relay stations. Only it's not actually quite exact, apparently because KSP is using a different (probably a lot coarser) terrain mesh for occlusion testing than for actual rendering. But it's pretty close. In theory, on a perfectly smooth round body (like the polar ice caps of Kerbin or the flats of Minmus) with occlusion at 1.00, surface stations should not be able to connect to each other at all unless they're raised up on towers of some sort. In practice, this mostly seems to indeed be the case, although the location of the stations may also matter (presumably because of the coarseness of the occlusion mesh).

On the other hand, setting the occlusion factor to 0.99 (it goes down in increments of 0.01) on the same perfectly smooth spherical planet will allow connections between stations up to 2 * arccos(0.99) ≈ 16 degrees apart, even if they're both at zero elevation! At 0.98 occlusion, the maximum distance goes up to about 23 degrees.

Also, the slider in the difficulty settings actually goes up to 1.10, and setting it above 1.00 does make it even harder to get ground relay stations to connect with each other. It's still possible in non-flat terrain, but you can often fail to get a connection between two mountain tops even if it looks like they should have line of sight, especially if there's any kind of a hilltop in between.

But in my testing, I never saw any actual difference between occlusion factors 1.01 and 1.10(!). I suspect the actual scaling factor might be capped at 1.01 in the game code, even though the cap in the settings UI is higher.

Edited August 24, 2020 by vyznev

[Sky Vagrant]

3 hours ago, vyznev said:

Basically, setting the occlusion factor to 1.00 means that you essentially need a line of sight between relay stations. Only it's not actually quite exact, apparently because KSP is using a different (probably a lot coarser) terrain mesh for occlusion testing than for actual rendering. But it's pretty close. In theory, on a perfectly smooth round body (like the polar ice caps of Kerbin or the flats of Minmus) with occlusion at 1.00, surface stations should not be able to connect to each other at all unless they're raised up on towers of some sort. In practice, this mostly seems to indeed be the case, although the location of the stations may also matter (presumably because of the coarseness of the occlusion mesh).

Thanks! I was unaware of this setting. This makes it easier to assess the LoS category and I'll add a note about the default settings.

BTW - I've decided that the default settings represent long-wave communications that either follow the surface or travel through it. So the default 0.9 occlusion isn't entirely unrealistic, and there is some evidence of ultra-low frequency waves traveling around the actual Moon.

[Sky Vagrant]

Anyone considering attempting this challenge? Anything I can clarify?

[Kerminator K-100]

Looks interesting. I'm currently in the middle of some stuff but I'll see if I can give this a try in the future.