Hey, quick question.

I'm working on a build for a tournament and put a combo together out of trying to fill a pesky 3 points with a limited collection.

I came to find the combo Seismic Torpedo and R5-X3. Is it possible to discard the Astromech, fire at an obstacle and because of the Droid, skip rolling for splash damage?

No.

R5-X3 must be triggered before you reveal your maneuver. After you discard R5-X3, ignoring obstacles is not optional, which means you shouldn't be able to choose an obstacle with Seismic Torpedo during your perform action step.

If you try to curcumvent the timing problem by using Advanced Sensors, then you have the opposite problem. If you use Advanced Sensors to fire Seismic Torpedo before discarding R5-X3, then your ship is vulnerable to the damage because you can't discard R5-X3 until after Seismic Torpedo resolves.

Thanks for the clarification. I'm glad I asked before I tried to run it

No, but I disagree with jmswood's reasoning why.

R5-X3 allows you to ignore obstacles, but it does not make it so that they simply don't exist from your perspective. You could discard the droid and then fire Seismic Torpedoes just fine. However, the droid will not stop you from taking damage because the damage isn't an effect of the obstacle, but an effect of Seismic Torpedoes. R5-X3 and Seismic Torpedoes have zero interaction.

30 minutes ago, jmswood said:

If you try to curcumvent the timing problem by using Advanced Sensors, then you have the opposite problem. If you use Advanced Sensors to fire Seismic Torpedo before discarding R5-X3, then your ship is vulnerable to the damage because you can't discard R5-X3 until after Seismic Torpedo resolves.

To be clear: you could totally use trigger R5-X3 and Advanced Sensors at the same time and resolve them in that order, but then you're being told (not given the option, told) to ignore obstacles, so you can't use Seismic Torpedoes.

Even if you could get both R5-X3's effect and Seismic Torpedoes's effect at the same time, ignoring obstacles doesn't protect you from Seismic Torpedoes's damage, as discussed in this thread about Dash.