And if you took Natural Selection to Ahead Four
“I know,” he said without looking up. “You were wise to keep the entire ship in deep-sea state.”

“It had to be this way. Otherwise, agitated officers and soldiers would have attacked this cabin. _And if you took Natural Selection to Ahead Four at will, you would have killed them all_. That’s also the reason why the pursuers haven’t closed in.”

Excerpt From
The Dark Forest (Remembrance of Earth's Past)
Cixin Liu

Context: the ship called “Natural Selection” is a extremely large spaceship. There are four types of acceleration among which the highest is called “The Ahead Four”, which would allow the spaceship to travel at one-hundredth the speed of light. According to physics, the passengers (in this case, the officers and soldiers) would be dead in a spaceship traveling that fast—only deep-sea state can protect them. And before the quoted conversation, the spaceship has already been taken to Ahead Four.

Question:
Why is “if you took” instead of “if you had taken” used here?

Thank you.

Question

And if you took Natural Selection to Ahead Four
“I know,” he said without looking up. “You were wise to keep the entire ship in deep-sea state.”

“It had to be this way. Otherwise, agitated officers and soldiers would have attacked this cabin. _And if you took Natural Selection to Ahead Four at will, you would have killed them all_. That’s also the reason why the pursuers haven’t closed in.”

Excerpt From
The Dark Forest (Remembrance of Earth's Past)
Cixin Liu

Context: the ship called “Natural Selection” is a extremely large spaceship. There are four types of acceleration among which the highest is called “The Ahead Four”, which would allow the spaceship to travel at one-hundredth the speed of light. According to physics, the passengers (in this case, the officers and soldiers) would be dead in a spaceship traveling that fast—only deep-sea state can protect them. And before the quoted conversation, the spaceship has already been taken to Ahead Four.

Question:
Why is “if you took” instead of “if you had taken” used here?

Thank you.

Answer

"If you had taken" is technically the correct choice.  Even natives will occasionally use conditional 2 when they should have used conditional 3.  The truly important difference in conditionals is between the "real" conditionals (Conditional 0 and conditional 1) and the "unreal conditionals" (conditional 2, conditional 3, and mixed conditional).  If you use conditional 1 when you should use conditional 2, it is a very large mistake, but if you use conditional 2 when you should use conditional 3, or if you use conditional 1 when you should use conditional 0, it is a very small mistake.

Good job!  You found a (small) mistake in the translator's english!