Once a booster get to 70,000M and is travelling at 7700km/hr how fast does the 2nd stage need to accelerate to achieve orbit?

[dv8inpp]

Once a booster get to 70,000M and is travelling at 7700km/hr how fast does the 2nd stage need to accelerate to achieve orbit at?

 

[Helio]

The goal of any launch is to reach orbital velocity, roughly 18,000 mph, though less for higher orbits.

A 2nd stage greatly helps get this speed, requiring less fuel.

 

[dv8inpp]

Sorry the question wasn't clear.

How quickly does the second stage need to accelerate to achieve orbit? Is there a minimum acceleration they need to achieve to prevent re-entry.?

 

[Helio]

Sorry the question wasn't clear.

How quickly does the second stage need to accelerate to achieve orbit? Is there a minimum acceleration they need to achieve to prevent re-entry.?

The rate of acceleration is an engineering balancing act. They must weigh all the variables as necessary to get to that velocity.

A very high acceleration, for instance, will use less fuel but can cause more damage and may require special engines, etc.