Thanks, people have already pointed that out.

Can you explain me why, to accelerate a rocket, I only have to consider delta-v and not the initial velocity of the rocket, when calculating the energy I need?

The energy needed is not usually calculated explicitly but is implicit in the

*Tsiolkovsky rocket equation* as described in:

**Tsiolkovsky rocket equation**

The **Tsiolkovsky rocket equation, classical rocket equation**, or **ideal rocket equation**, describes the motion of vehicles that follow the basic principle of a rocket: a device that can apply acceleration to itself using thrust by expelling part of its mass with high velocity and thereby move due to the conservation of momentum.

The equation relates the delta-v (the maximum change of velocity of the rocket if no other external forces act) with the effective exhaust velocity and the initial and final mass of a rocket, or other reaction engine.

For any such maneuver (or journey involving a sequence of such maneuvers):

The equation relates the delta-v (the maximum change of velocity of the rocket if no other external forces act) with the effective exhaust velocity and the initial and final mass of a rocket, or other reaction engine.

For any such maneuver (or journey involving a sequence of such maneuvers):

where:

**Δ***v* is delta-V – the maximum change of velocity of the vehicle (with no external forces acting).

*m*_{0} is the initial total mass, including propellant, also known as wet mass.

*m*_{f} is the final total mass without propellant, also known as dry mass.

*v*_{e} is the effective exhaust velocity relative to the rocket.

**ln** is the natural logarithm function.

The simplest way to explain it is that the initial rocket mass, including fuel (often RP-1 and LOX), is

*m*_{0} but only the final mass,

*m*_{f}, is accelerated to the final velocity,

*v*_{f}.

If the rocket is being accelerated from an initlial velocity, say

*v*_{0}, any fuel in the rocket is already travelling at

*v*_{0}. Hence the energy is in this fuel is its own chemical energy plus its kinetic energy because it is moving at

*v*_{0}.

The SpaceX Falcon Heavy has a launch mass on 1,420,788 kg but puts "only" about 63,800 kg (a lot of that is usually more propellant) into Low Earth Orbit.

I hope this makes sense, because I'm finding it hard to put it simply - probably because i'm no

*Rocket Scientist* so have an imperfect understanding myself.

*<< Fixed a few v's thst were m's >>*