Strange behavior of the DTS-M1 antenna

[Gurkonier]

Today i sent a probe to Duna to perform some science and send it back to Kerbin.

I had a lot of problems doing this, because i wasn't able to get it work, even though i had the DTS-M1 antenna with me, a connection was established, had a signal strength of about 70%, and Data TX was there and showed me, that i could transmit science.

After some trial and error and tweaking difficulty settings, i discovered, that if i retracted the antenna and then tried to transmit the science, it actually started working. The antenna extends, transmits, and retracts.
But if the antenna is already extended, i get the message, that i have no antenna in range.

Does anyone experienced the same thing? Is this a bug, or do i miss something obvious?

Edit: I have no mods installed, which should change the behavior of CommNet e.g. RemoteTech...

Edited October 25, 2022 by Gurkonier

[Mahnarch]

 

That one?

 

I can't say I've ever had that issue.

And, I'm assuming it's not another issue such that you're running out of battery juice while it's already extended, or that you have a relay that's moving in orbit at an inconvenient timing?

Maybe rotate your lander a scoosh? Half a smidge?

[Gurkonier]

Thanks for your reply.

Yes, that is the antenna i used.

I had more than enough battery charge and checked multiple times, that my connection was good.
Rotating it was one of my last attempts, knowing that shouldn't change anything.

I also never experienced that myself. I have more than 1000 hours, so i'm very confident, that i checked everything that possibly could intervene with transmitting my science.
So i think, that there is a mechanic regarding communication, which i never knew exists, or it's a bug, which also never occured to me...

The one is the actual probe in Duna's orbit, which had this problem:

This one is a test probe, which i cheated into Duna's Orbit:

The were in the orbit at the same time. The first one can only transmit science, when the antenna is retracted. The second one can do this all the time.
For the second one i also included a hinge, because i thought this could be a problem, but this time it worked.

Both have this connection status:

 

[Mahnarch]

Ok. I'd toss it up to a bug.

Maybe the age of your craft in the code has something to do with it?

I'm not a computerologist. I don't know these things.

[K^2]

21 hours ago, Mahnarch said:

Maybe the age of your craft in the code has something to do with it?

Unlikely, but any functional component has some state variables. Antenna being retracted or extended being just one of however many the devs thought they needed for the full intended functionality. Depending on the exact implementation, it is possible for these to end up in an inconsistent state, resulting in a bug that persists, but is hard to replicate.

For a simple illustration, imagine that you have two light switches controlling two lights in a room. Your intention is to have both lights on or both off, so you flip both light switches at the same time. Now imagine that for some reason, at some point, just one switch got flipped, but you continue flipping both switches when you want to turn the lights on/off. From this state, you'll always have one light on and one off - a bad state that you can't exit without a change to the algorithm.

I don't feel like decompiling the game (again) to take a look at exactly how that part of the code works, but my first guess would be that there's a flag saying that the antenna's extended, and a separate one that says it's ready to transmit, and the two don't trip at exactly the same time, because animation takes some time to finish, but both are simple toggles. So we're looking for a possibility that these two flags become inconsistent. If I was trying to reproduce this bug, I would try things that can disrupt the process during the animation. Quick-saving and re-loadng while antenna is extending/retracting, switching vehicles, going into time warp, etc. If that, indeed, reproduces the bug with a newly launched antenna, then repeating the process may fix it. Of course, the bug could be way more convoluted as well, and in either case, the correct fix is going to be in the game's code.

[Gurkonier]

That sounds convincing. Maybe i'll try to replicate the bug in the future. But i think, if there will ever be another hotfix for KSP 1, this is not important enough to be fixed, nor will it be relevant when KSP 2 releases.