Building a radio tower to Mun

[suicidejunkie]

I have been building out a surface grid of comm relays, and the southern hemisphere of Kerbin has a distinct lack of convenient mountains with LoS to the northern hemisphere.

But look, I hear a little voice say; the south pole is such a nice place, with a constant view of the sun!  How about a relay there that will be able to reflect signals off the mun and back to a station in the north which would then kindly forward the connection on to KSC!  And hey; it would even be able to mount giant antennas for pointing at planets with constant contact all day and forever as well!

From the mountain closest to the pole, I found it took a mere 5 relays flat on the ice cap to reach the pole (12.5km of radio distance with only 30m of terrain height!).  A good sign surely!

But no, it was not to be.  When I finally sat down to determine how many struts and ladders I would need to assemble the radio tower with KAS, the harsh facts of geometry show their true nature.

 

1) The mun is 11400km away.  The radius of kerbin is 600km.  This means a 0.053 radian angle is needed to get LoS over the horizon.

2) Those 0.053 radians are 31.564km away from Kerbin's spin axis, as the tunnel bores.

3) Said tunnel ends up 869m beneath sea level of the pole, or 899m below the ice cap.

4) 0.053 radians on the LoS, across 31.564km to the axis, leaves a shocking 1.661km of height.

5) 1.661 km, minus the 899m to reach the ice cap, leaves... 800m of tower to build in order to see the equator of mun.

 

Settling for sight of the matching pole of mun (200km higher up, giving 0.035 radians for the LoS angle), drops the tower requirement to 340m.

To me this seems slightly plausible.  It will take a KAS screwdriver, a huge pile of girders, many many ladders, and nerves of steel.  Maybe a bucket of struts as well.

 

However, the relay pairs on the way to the pole managed 12.5 km with only 30m of altitude each...

12.5km around Kerbin is almost 0.021 radians.  If we build a ring of towers 12.5km from the pole, we'd only need 0.014 radians of sight line

to see the pole of Mun.

And that, my friends, works out to just 31m of radio tower above the polar cap.  Hardly monumental, and in fact nearly trivial.

It would require an infinite number of towers forming a circular wall at just 31m, but we can build them a little taller than that, and have 3 evenly spread instead.

 

 

My dream of a single giant tower on the pole with LoS to everything always and forever will be quite Kerbal, and it shall be attempted, but it is still good to know that there is still a practical fallback option remaining.

(And of course, if we neglect Mun, all other planets and moons are easily in LoS to Kerbin's poles thanks to the incredible distances; inclination means they'll only see one pole, but that's fine)

[Allocthonous]

I like the idea of ground stations. They fit in nicely with the whole infrastructure-building gameplay style. And I have to agree, giant rickety radio towers do seem terribly Kerbal.

[KerikBalm]

Well, I guess you are playing with all modifiers set to 1.0?

I do something like 0.95 and o.99 for atmo/non atmo bodies....

Diffraction and atmospheric ducting are a real thing after all

[Snark]

Does building a tower actually work, to improve LOS?

For example, I wouldn't be surprised if the game just uses the ship's CoM as the transmission location, rather than the antenna's. If that's the case, your tower may need to be a lot taller than one might expect.

Does building a tower actually work, to improve LOS?

For example, I wouldn't be surprised if the game just uses the ship's CoM as the transmission location, rather than the antenna's. If that's the case, your tower may need to be a lot taller than one might expect.

[suicidejunkie]

1 hour ago, Snark said:

Does building a tower actually work, to improve LOS?

For example, I wouldn't be surprised if the game just uses the ship's CoM as the transmission location, rather than the antenna's. If that's the case, your tower may need to be a lot taller than one might expect.

I'll be testing that as I work.

For the Munar connection (if I don't get signal earlier), I plan to build the tower and then place an independent probe gently atop it as a separate vessel... then run away quickly and unload the physics while giggling madly and/or evil-laughing.