How to get to Duna without losing probe control?

[AxSirlotl]

I haven't played KSP in a while and I unfortunately discovered that I can't fly to Duna the same way I did before because I keep losing control of my probe when it gets near to Duna. How do I build a communications network that will let me get to Duna?

[Zhetaan]

@AxSirlotl:

There are a few of ways to do this.

You can upgrade the Tracking Station to get a more powerful ground-based antenna that will help you connect to probes that are farther away.

You can get more powerful (and expensive and EC-thirsty) antennas for your ship.

You can set up a series of relays that will let you leapfrog weaker signals to Duna using a number of probes that orbit between Kerbin and Duna.

You can send a pilot and not worry about antennas at all.

You can opt for a less-than-fuel-efficient transfer to Duna that gets you there when Kerbin is close enough to give a good signal.  If you're losing control right before you enter Duna's sphere of influence, then you probably would have control when Kerbin and Duna are near conjunction.

[devikwolf]

My personal recommendation is to follow the same model that early NASA planetary missions used: build a simple relay orbiter along with your probe, and package them both together on the same upper stage transfer vehicle. Once you enter Duna's SoI (or you've captured yourself into Duna orbit), you can separate the probe and the relay into discrete vehicles and use them as needed.

Here's a couple of pointers I've found helpful:

• Use a stock fairing with interstage nodes enabled to be able to more easily package both vehicles into an aeroshell (or connect both together inside the payload fairing via a double-sided decoupler)
• It's usually best to have your relay in a high altitude orbit, and usually on a steep inclination. Both help give the relay a better path with less planetary occlusion -- especially as your commnet grows
• The "small" fixed relay dish (not the folding one) will have enough range to reach from Kerbin to Duna (or Eve) regardless of where those planets are with respect to one another, once you've upgraded your tracking station. Larger dishes will be needed for exploring deeper into the solar system.
• Each upgrade to your tracking station increases the max range of each communication device
• Try building a very compact and inexpensive basic relay that you can bring along with almost any probe mission. You should easily be able to build a dirt cheap and very light relay that can be included in any of your probe missions without a drastic redesign of your launch vehicle
• Since these parts can be heavy, try to set up your encounters so that you can decouple your relay when you've just entered the planet's SoI, and pack it with just enough fuel to park it into your desired orbit. Then, your non-relay probe can carry much lighter radio gear since it only needs to be able to reach the local relay station
• If you're into mods, check out DMagic Orbital Science, which adds a pair of gigantic folding relay dishes. The larger of these, when deployed in Joolian orbit, can reach back to Kerbin with near-100% signal strength.