Hi. Collision Detector says - 'While you boost or barrel roll, you can move through and overlap obstacles. ..... After you move through or overlap an obstacle, you may spend 1 charge to ignore its effects until the end of the round.'

When do I have to decide to use the charge?

Can I move onto/over an obstacle and roll a die to see the result before deciding to use a charge?

If I use the boost action and I'm not sure can I move my ship and when it ends up on an obstacle, roll and then decide to use a charge?

Thx.

2 hours ago, Slade said:

Can  I move onto/over an obstacle and roll a die to see the result before deciding to use a charge?

No, as rolling for damage is already part of applying (not-ignoring) the effect of an obstacle, so by then you'd have already committed to suffering these effects.

2 hours ago, Slade said:

If I use    the boost action and I'm not sure  can I  move my ship and when it ends up on an obstacle, roll and then decide to use a charge?  

First of, the "boost / barrel roll through obstacles" clause is independent of spending the charges, so whether you fit or not, you can perform the boost at no additional costs.

If you do overlap an obstacle while boosting however, you ought to now face the consequences, yet you get to decide to spend one charge to ignore any consequences throughout given turn.

As for whether or not you may roll then decide - no, see previous bit of my answer.