Rocket Science!

I have always liked rockets, our best understood way to achieve space travel. I thought I would discuss some of the basics.

Rockets work by flinging something behind them and moving forward in reaction. The general term for the stuff you fling away is "propellant." The scientific principle at work was described by Newton's Third Law of Motion.

Propellant can take the form of any of the phases of matter: solid, liquid, gas, or plasma

Many methods have been studied to power the flinging of propellant. These span our known laws of physics: electrical and magnetic fields, nuclear fission and Fusion, chemical reactions, anti-matter reactions. These have all been studied individually and in combination.

Because the methods of flinging propellant vary considerably, evaluation requires some common measurement of the options. The most common measurement in use is specific impulse. This is defined most simply as "how much propellant I need to push out my engine to change my speed."

If two rockets wish to change their speed by the same amount and one rocket requires twice the propellant for the same change, then it uses an engine with half the specific impulse of the first.

Specific impulse can be evaluated in several ways, typically by the speed of the flung propellant or by the mass flow rate of the propellant through the engine. Either method can be used to calculate how much an engine can change a rocket's speed for a given purpose.

The total change in velocity from a rocket full of fuel to one that has emptied all propellant through the engine is referred to as Delta Velocity or "Delta Vee."

Here is a Delta Vee map of the Solar System, showing how much you need to change your speed to move around the planets.

Here is a good article on the Specific Impulse possible by burning different chemical fuels.

Here is a website that discusses Rockets in real life and fiction. Caution: This may be addictive.