how to use relays in order to avoid plasma blackout consequences

[antipro]

I've an unmanned lander, connected via relay with 2 Communotron 16-S antennae, aerobraking into the jool atmosphere.
The plasma blackout doesn't work, the lander has always the maximum signal strength. No situational modifier.
Can't figure out why. any help?





The same lander in the kerbin atmosphere: plasma blackout works, the lander loses its signal strength.





Laythe atmosphere: situational modifier partially works, cause the lander once it loses the signal, no longer connect through the closest relay, then the situational modifier stops working.





Duna atmo: plasma blackout works, the lander loses its signal strength.



 

Edited March 15, 2021 by antipro

[Guest]

I'm not sure Jool’s atmosphere counts as the same type as Kerbin/Laythe/Duna/Eve as it's a gas giant (ie ALL atmosphere if you think about it) as opposed to rocky planets with an atmosphere in the classic sense? Might be wrong though but sounds like it's working for other ‘atmosphere’ planets? TBH I never use it so can't confirm.

[antipro]

jool has an atmosphere as the other planets.
https://wiki.kerbalspaceprogram.com/wiki/Jool#Atmosphere
 

anyway here's another similar test probe with no antennae at all.
result: situational modifier works, the probe loses the signal.
can't test other antennae cause they explodes even if they are covered by a shield.

Edited March 14, 2021 by antipro

[OHara]

Maybe your relay was in just the correct spot, when you hit Jool's atmosphere.  The original request for the plasma effect mentioned how the US Space Shuttle worked around it with the  Tracking and Data Relay Satellite System. There are parameters like 'commNetDotForBlackoutMin' in Physics.cfg with comments that indicate the plasma effect fades away for communications directed between 30° and 60° of retrograde, and has no effect at all if the link is within 30° of retrograde to the craft.

 

[antipro]

I already remembered that old thread I started on reentry blackout, but when they started talking about the real life STS relays system,
I thought they were referring to real life only, I never thought it was implemented in the game.
As today for me were valid the following quotes:
 

On 7/2/2017 at 1:39 PM, Tex_NL said:

As far as I know the re-entry interference is not modelled in detail in KSP. It's either on or off. Moving your antenna to a different section of your craft will not make a difference.

 

On 7/2/2017 at 8:16 PM, Vanamonde said:

antenna position is irrelevant.

and they never say nothing about relays position relatively to the retrograde direction in the game.

So now you are saying that if I have a relay within 30° of my retrograde direction the plasma blackout has no effect, exactly like they said about STS, right?
if so, then this could explain several things, especially the strange behavior on laythe test.

anyway excuse me I really can't get it. can you tell me how did you calculate those angles? 30° and 60°..
and btw you said the blackout starts from 30° to 60°, after 60° what happens, how does it behave?

I opened Physics.cfg and found the line you mentioned but I can't understand almost nothing.

// commNetDotForBlackoutMin = -0.86599999999999999 // Minimum dot between velocity and link direction for comms to start blacking out from plasma (if that option is enabled)
// commNetDotForBlackoutMax = -0.5 // Dot between velocity and link direction for full blackout multiplier


This is the angle just before entering the jool atmo, and eyeballing, it could be less than 30°, and certainly decreases, as I brake.
Thx.

Edited March 15, 2021 by antipro

[OHara]

10 hours ago, antipro said:

how did you calculate those angles? 30° and 60°..
and btw you said the blackout starts from 30° to 60°, after 60° what happens, how does it behave?

The word 'Dot' in KSP parameters means the cosine of the angle between the vectors, so I interpreted Physics.cfg as
commNetDotForBlackoutMin = −0.866 = cosine 150°  // between velocity and link direction for comms to start blacking out from plasma
commNetDotForBlackoutMax = −0.5 = cosine 120°  // between velocity and link direction for full blackout multiplier

Then 180° minus those angles give the smaller angles between the link and retrograde.

The word 'Dot' for cosine only makes sense if you have leaned the names of the vector-math operations, because the cosine of the angle between vectors a and b is a·b /|a| /|b| involving the 'dot-product'.

I don't know how blackout works.  I just assumed some things based on those //-comments and the behaviour requested in the original thread.  I assume for any communication links further forward than 60° from retrograde get the maximum blackout effect, because then the 'Dot' would be more than 'commnetDotForBlackoutMax'

[antipro]

wow, ok I suck hard in both math and trigonometry too, but somehow I now got it.
So definitively the plasma blackout in game really works as in real life: relays can help to avoid its consequences.
Is never too late to understand something new.
Thread title edited.

Really thx @OHara

Edited March 15, 2021 by antipro