Madhavan, the actor has given a stellar performance in this film. Basically, the film revolves around him and his character only is purely fleshed out and he has justified it. Simran, as meena too gives an empathetic performance. The rest of the cast is good.
The foreign actors seem to be good but i am not sure about it because someone took a conscious decision to dub their french and english and russian all into hindi and that takes out the gravity from the dialogues. I can say for me, that many a times i was disconnected becausd of the dubbing. There was no need to dub the foreign languages into hindi.
The writing too is pretty good. The scientific terms about rocket science, the concepts are not oversimplified for the audience which i liked being a science student myself. I like mission mangal too but taking out the scientific approach from a science film does not justify it. Other characters apart from nambi are not really written well. Even we don't get to know much about his family members and that is the exact reason why we can connect with nambi but not with his family members so much. The screenplay is pretty much engaging specially the second half where the drama portion is built well. The first half feels a bit stretched because of the reason of dubbing etc.