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Brikoleur

Probe loses contact with KSC shortly after launch... what gives?

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I'm designing a return probe for Laythe and doing trials on Kerbin. My problem is, shortly after launch, at roughly 50-60k altitude, it loses contact with KSC, going instantly from maximum signal to zero. I have a surface-mounted Mk 16 antenna on it, which has not been destroyed by aero forces. I have a direct line of sight to KSC (level 2 tracking station). Contact isn't re-established once it's out of the atmosphere so it can't be plasma-induced comms blackout either (and I'm not going that fast anyway).

So... what gives? Why am I losing contact?

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Ensure you have the connection lines visible in map view, it's the right-most button on the CommNet display in the upper-left. This happens to me as well, even with all tracking station enabled, because there is a blind-spot over the ocean at low altitudes. Best bet is to put up a relay sat as soon as you can for launches or launch in an inefficient "pop-up" manner where you build the majority of your "horizontal" velocity late in the launch.

Edited by regex

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Thanks. There clearly is, but I don't understand why. 

I even put a command pod with a big relay antenna on the runway, and then set the commlinks display to "vessel links." There are several, and then all of them blink out all of a sudden. Why does it happen?

I would assume this shouldn't be an issue on Laythe as I would be controlling the probe from orbit. It'd just be a bit of a bummer to discover that only when I'm there...

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2 minutes ago, Brikoleur said:

I even put a command pod with a big relay antenna on the runway, and then set the commlinks display to "vessel links." There are several, and then all of them blink out all of a sudden. Why does it happen?

What are your occlusion sliders set to? I have mine at 100% for airless and gas planets and I get the same thing.

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3 hours ago, regex said:

Ensure you have the connection lines visible in map view, it's the right-most button on the CommNet display in the upper-left. This happens to me as well, even with all tracking station enabled, because there is a blind-spot over the ocean at low altitudes. Best bet is to put up a relay sat as soon as you can for launches or launch in an inefficient "pop-up" manner where you build the majority of your "horizontal" velocity late in the launch.

That blind spot is annoying, but I bet that it's intentional. In the same way that the stock craft aren't perfect to encourage you to tweak them, I'd bet that the ground base coverage isn't perfect to encourage you to loft some commsats.

Btw, three commsats each with two Hg-5s or one of the fixed dishes in a 600 km orbit should get rid of the blind spot, assuming roughly equidistant spacing.

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5 minutes ago, Norcalplanner said:

Btw, three commsats each with two Hg-5s or one of the fixed dishes in a 600 km orbit should get rid of the blind spot, assuming roughly equidistant spacing.

Why three? Just launch one into a geosync orbit or, like I do in RSS, just put one up above your normal parking orbit and fast-forward until it comes around for launch.

~least effort into boring tasks~

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1 minute ago, regex said:

Why three? Just launch one into a geosync orbit or, like I do in RSS, just put one up above your normal parking orbit and fast-forward until it comes around for launch.

~least effort into boring tasks~

I use three because the HG-5, the first relay dish that's available, doesn't have enough range to work in geosynchronous orbit. If you wait until the fixed dishes are available, then what you describe works fine. I'm a bit impatient, though. And I only think to check map view prior to launch when I'm rendezvousing with something. :)

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I've not run into this yet, and I've launched plenty of probes. I'll have to pay more attention next launch.

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13 minutes ago, Norcalplanner said:

I use three because the HG-5, the first relay dish that's available, doesn't have enough range to work in geosynchronous orbit. If you wait until the fixed dishes are available, then what you describe works fine. I'm a bit impatient, though. And I only think to check map view prior to launch when I'm rendezvousing with something. :)

Is the HG-5 that "long-arm of the dish" dish? That would still work from a 200km orbit, I think, which is where I'd slap a launch sat. I'm just lazy about putting sats up, i guess, I want as little clutter as possible.

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By the way, if you struggle to get a constant signal whilst launching your relay satellites, send them up all at once in an interstage fairing beneath the command pod of a crewed satellite deployment vehicle.

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3 hours ago, eloquentJane said:

By the way, if you struggle to get a constant signal whilst launching your relay satellites, send them up all at once in an interstage fairing beneath the command pod of a crewed satellite deployment vehicle.

I plan to do that when I reach out (Eve, Duna, etc).

I didn't have much of a problem putting relays up around Mun or Minmus. No fancy math, no MJ, I just put one relay up in a circularized 500km orbit, with two more following it ... set the first one as target for the two following, matched plane off the first, and then just eyeball adjusted the positions in orbit (as one would for docking intercept maneuvers). Worked fine. The antennas for the relays are the HG-5. The probes and ships use the Comm 16-S.

TNvj4Gv.png

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3 hours ago, regex said:

Is the HG-5 that "long-arm of the dish" dish? That would still work from a 200km orbit, I think, which is where I'd slap a launch sat. I'm just lazy about putting sats up, i guess, I want as little clutter as possible.

It is, and it would, but with three up there I can launch at any time without waiting for a sat to come over the horizon.

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4 hours ago, eloquentJane said:

By the way, if you struggle to get a constant signal whilst launching your relay satellites, send them up all at once in an interstage fairing beneath the command pod of a crewed satellite deployment vehicle.


You don't need a crewed vehicle - you just need patience in making your burns when you're in comms.  Back when I used RemoTech, I could put up an entire geosync constellation w/o a crewed vehicle.

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8 hours ago, Brikoleur said:

 I have a direct line of sight to KSC (level 2 tracking station).

Actually, you don't.

That blackspot has caused me to crash or lose a probe a few times now. There's a few other such blackspots around LKO as well.

You need to get some relay satellites up.

8 hours ago, Brikoleur said:

I even put a command pod with a big relay antenna on the runway, and then set the commlinks display to "vessel links." There are several, and then all of them blink out all of a sudden. Why does it happen?

Because you lose LOS. The KSC is behind Kerbin from the craft's POV.

 

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Are you sure you don't have plasma blackouts checked? On my save with groundstations turned on, that blind spot rarely affects me when I'm above 50km.

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I just built a telecommunication network and no problem.

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8 hours ago, Draco T stand-up guy said:

Actually, you don't.

That blackspot has caused me to crash or lose a probe a few times now. There's a few other such blackspots around LKO as well.

You need to get some relay satellites up.

Because you lose LOS. The KSC is behind Kerbin from the craft's POV.

Actually I do. There are multiple connection lines to multiple points around KSC, and they all blink out at once, with nothing occluding them.

3 hours ago, JohnnyPanzer said:

Are you sure you don't have plasma blackouts checked? On my save with groundstations turned on, that blind spot rarely affects me when I'm above 50km.

I do have plasma blackouts checked, but (1) this happens even if I'm going much too slow for it, and (2) contact is not re-established once out of the atmosphere.

13 hours ago, NoMrBond said:

Is the probe core running out of power?

No.

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17 hours ago, Brikoleur said:

I even put a command pod with a big relay antenna on the runway, and then set the commlinks display to "vessel links." There are several, and then all of them blink out all of a sudden. Why does it happen?

 

36 minutes ago, Brikoleur said:

Actually I do. There are multiple connection lines to multiple points around KSC, and they all blink out at once, with nothing occluding them.

Well, I'd say that the runway was at the KSC as well as the KSC so when you lose LOS with the KSC you also lose LOS with the command pod parked on the runway at the KSC. What's occluding them is Kerbin itself.

Not that a command pod can control a probe unless it's got two pilots in it.

 

At a guess I'd say that you're going up at a fairly shallow angle, around 45° or less and you're getting out over the ocean and losing connection with the KSC. That's due to the KSC disappearing over the horizon.

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39 minutes ago, Draco T stand-up guy said:

Not that a command pod can control a probe unless it's got two pilots in it.

Seriously, is this true? Can you control a probe that is out of range of the KSC, as long as you have a command pod with two pilots close to that probe?

My understanding was that it only works when you have craft with the 2.5m probecore on it and a single pilot in the pod...all that, close by to an orphan probe

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1 hour ago, Blaarkies said:

Seriously, is this true? Can you control a probe that is out of range of the KSC, as long as you have a command pod with two pilots close to that probe?

My understanding was that it only works when you have craft with the 2.5m probecore on it and a single pilot in the pod...all that, close by to an orphan probe

If you're using the Mk 2 pod or the Mk 2 lander can, yes. Those have a built-in probe control point. Otherwise you need one of the special probe cores but only need a single pilot. Also "close by" just means "in radio contact," so if both craft have big antennas it's not necessarily all that close. (I'm not 100% sure but I think the controlling craft needs a relay-type antenna.)

2 hours ago, Draco T stand-up guy said:

At a guess I'd say that you're going up at a fairly shallow angle, around 45° or less and you're getting out over the ocean and losing connection with the KSC. That's due to the KSC disappearing over the horizon.

I'll check later today. If I can post a screenshot of the out-of-control probe with KSC visible below, will you believe I still have LOS?

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16 hours ago, regex said:

Why three? Just launch one into a geosync orbit or, like I do in RSS, just put one up above your normal parking orbit and fast-forward until it comes around for launch.

~least effort into boring tasks~

There are other gaps in the low-level coverage.  Only one of them matters for launching, but if you do more on Kerbin itself than just launch into space, complete surface coverage is nice to have.

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32 minutes ago, Brikoleur said:

If you're using the Mk 2 pod or the Mk 2 lander can, yes. Those have a built-in probe control point. Otherwise you need one of the special probe cores but only need a single pilot. Also "close by" just means "in radio contact," so if both craft have big antennas it's not necessarily all that close. (I'm not 100% sure but I think the controlling craft needs a relay-type antenna.)

I'll check later today. If I can post a screenshot of the out-of-control probe with KSC visible below, will you believe I still have LOS?

I'd like a confirmation on the requirement of a relay type antenna.

Also worth noting is that all but one of the the probe control points are single hope only. I *think* single hope means a direct connection, not that you get to use 1 relay between the craft an the probe... I haven't tested this, I'm just basing it on the display setting "first hop"

A pilot with the 2.5m probe core can have an unlimited number of hops, and a piloted base with such a core could basically serve as a 2nd KSC for the purposes of control.

A different control point, even with a big antenna, is going to give you trouble as it can't operate a relay network to control probes on the far side of planets/moons. No control of a probe on the far side of ike if your control point is on/orbiting duna (unless you have a direct connection back to KSC).

In the stock system I think it will probably be very very very biased towards having a relay connect to KSC rather than a local control point... but when OPM and kopernicus are updated for 1.2... I can see the 2.5m probe control points being very useful for being the base of relay networks for Urlum/Neidon/Plock

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1 hour ago, RoboRay said:

There are other gaps in the low-level coverage.  Only one of them matters for launching

Which is what this thread and the context of the conversation you were quoting is about.

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