We have a question that is almost the same as this one…but the question and answer both pertain to an earlier version (< .23), and note that the specific answer was to change with the newer version.
I know that if I do an experiment and recover the data by bringing the ship back to Kerbin and recover the ship, I get 100% of the experiment value. I also know that if I transmit the data back, I get a smaller percentage (which can vary, depending on various things).
Also, experiments can be repeated, but their value decreases with repeated runs.
So the question is: is it fine to transmit science experiment results back, and not have to worry too much about losing potential science gain in the long run?
(The answer to the earlier question was that it was fine; regardless of how you did it, you ended up with the same amount of science in the long run, for the most part, if you ran all experiments until they returned nothing. But, again, the answer also mentions that this was to change in some way with .23+, but it didn’t say in what way.)
You can transmit every experiment around every body at every altitude in every biome and not lose any potential science compared to recovering each experiment. The only difference is how many times those experiments will yield results.
The KSP wiki states that you cannot indeed get ALL science from solely transmitting. There is some threshold beyond which you can only gain more science for recovering the data. However it’s important to note that you do not lose science in transmission, regardless.
The transmission efficiency caps the maximum returnable science with the experiment via antennae. To gather all scientific value experiments needs to be recovered. With the release of 1.0, transmission efficiency drops radically on experiments that have already been performed and transmitted. If an experiment is recovered, transmission efficiency for that experiment drops to zero (situation and biome specific).
In other words for hypothetical Experiment A in a given situation, you may be able to glean 100 units of science from it. A single recovery might yield 70, while transmitting might yield 50, then 10, then nothing. Regardless if you transmit twice, your following recovery will net 40 science to completely exhaust the available research from that situation.
Transmit: 50 -> Transmit: 10 -> Recover: 40 = 100 Transmit: 50 -> Recover: 50 = 100 Recover: 70 -> Recover: 30 = 100 Recover: 70 -> Transmit: 0 = 70 (30 to go from recovery only!)