What is the primary purpose of the re-entry burn executed by a reusable booster?

Answer

To slow down and protect the structure from excessive aerodynamic stress.

When a booster targets recovery, it relights its engines for a re-entry burn after separation. This burn is crucial for slowing the vehicle down sufficiently to manage the aerodynamic stress experienced upon re-entering the atmosphere.

What is the primary purpose of the re-entry burn executed by a reusable booster?

#Videos

Here's what happens when rockets launch into space - YouTube

What Happens To Discarded Rocket Boosters And Old Satellites?

satelliterocketspacecraftlaunchdeployment