Double Rocket Propulsion Speed

[Lazyhound]

But my point still holds that there is no point having a second rocket once your are travelling in deep space, when you could instead have one big one with extra fuel instead of the bulk of the secind engine.

True, but I don't think that was the point you were making.

 

[Mr. Durden]

So, the bottom line is that the second rocket probably would go faster, but its not the most efficient way to achieve the higher speed?

I knew we had some smart folks here. Thanks for the info everyone!

 

[Kobushi]

In answer to the original question, no one has mentioned Newton (the scientist, not the pda). Newtons second law - every action has an equal and opposite reaction. The second rocket will exert a force on the first one equal to its own propulsive force, tending to push it backwards. It would be like pulling yourself up by your own bootlaces.

Actually, that's Newton's third law and it is because of this that rockets even work. Some people think that it is the expelled rocket fuel pushing against the launch pad that propels the rocket. It's actually the force created by nozzling down all that fuel and it sort of pushing itself against the rocket to escape that causes the motion. Hence, thrusters fired in space (with no launchpad around) still propel the spacecraft.

 

[MongoTheGeek]

So, the bottom line is that the second rocket probably would go faster, but its not the most efficient way to achieve the higher speed?

I knew we had some smart folks here. Thanks for the info everyone!

It depends on how heavy the fuel tanks rocket engine combo are. Staging is mostly done because you need a lot of thrust early on and less so later on. Otherwise what you want is drop tanks.

Once you are in "space" it doesn't really matter if the thrust is 1N or 1MN. Just the total impulse really matters.