# Vertical acceleration at main deploy

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#### dhkaiser

##### Well-Known Member
Looking at the graph in OpenRocket I see a positive spike in the vertical acceleration at main deploy. I'm thinking a rapid deceleration would have a negative spike. Where am I going wrong?

#### Buckeye

##### Well-Known Member
TRF Supporter
Remember that acceleration is a vector. Positive direction is up. The rocket is descending at the drogue speed, then the acceleration is in the up direction as the rocket reduces to the main parachute speed.

#### dhkaiser

##### Well-Known Member
Remember that acceleration is a vector. Positive direction is up. The rocket is descending at the drogue speed, then the acceleration is in the up direction as the rocket reduces to the main parachute speed.
Thanks Buckeye.