In the atmosphere it do. But if some dumbass hit escape velocity and bounces out of the atmosphere then my '57 turquoise cadillac will go just as fast up yonder. Fins might even make me faster.
Originally Posted by Don T. Lukbak
Actually, from a pure engineering perspective, if you're outside the atmosphere, fins will do nothing except add mass to the vehicle and hence make your acceleration slower, assuming similar thrust between the two vehicles. If you're referring to maximum velocity, again, the fins add nothing but mass, and assuming similar fuel types and supplies, your maximum obtainable velocity will be lower.
Now, inside the atmosphere, many more variables are introduced, and having fins may cause incremental increases in turn rate and/or overall stability, which may increase overall velocity, or shorten the time it takes to get from point A to point B, depending on how much maneuvering is required.
Just sayin'...