fluid dynamics - Space Rocket Ionizing Its Path To Decrease Fuel Consumption

A beam(maybe multiple beams from ground crossing at, or just some very high alternating potential, something like focused haarp) on tip of rocket targeting at path of it, ionizing just the closest molecules that are about to add friction to rocket.

Rocket having same signed static electrical charge so ionized particles (cores) don't add drag because they don't come close enough before rocket passes, or at least the air pressure at all heights is decreased by a good margin.

Just like rocket traveling in a bubble of vacuum. When vacuum applied only at tip, it could pull the rocket, increasing its velocity?

In other words, could it lessen space launch fuel consumption for friction?

Doable?

Dangerous?

Trivial?

How much energy needed? More than fuel of conventional ways? But ground based ionizators would make a lighter fuel depot for rocket, would it?

Answer

When you're considering hydrodynamic forces there are always two things to consider. One is the viscosity of the fluid, i.e. how much energy it takes to make it flow, and the other is the inertia of the object, i.e. how much energy it takes to make it move out of your way.

At high velocities the drag is dominated by the inertial forces. Air weighs more than you think - it's a bit over a kilogram per cubic metre. To push your way through the air you have to make it move so you have to increase its kinetic energy. It's the work you have to put in to increase the kinetic energy that causes the drag. So ionising the air isn't going to make any difference. It still has the same mass and the rocket still has to push that same mass out of the way.

In principle you could use the lasers to heat a column of air and reduce its density. That would mean there is less mass for the rocket to push out of the way, and it would indeed reduce the drag. The trouble is that it still takes energy to heat the air so all you've done is swap some of the work done by the rocket for work done by the lasers on the ground. Well, the real trouble is that it would be disastrously inefficient because the reduction in fuel needed by the rocket would be far outweighed by the massive amount of energy needed to power your lasers.