Terms

Here will be a full list of the physical and mathematical terms we’ll be using along with my attempt to put it into terms that can be easily understood. I’ll add them in as we come across them, the last thing we need is an impenetrable wall of maths and physics that will put people off from launching fireworks with pilots!

Rocket Terminology:

Delta-V – This is the amount of change of velocity that a rocket is capable of. For example Delta-V of 1000 m/s means that the rocket can change it’s velocity by 1000 metres per second. It doesn’t give you any idea of how fast it will do it. Higher Delta-V is, most often, better because it is standardised for vehicle mass. I often express this as two numbers XXXX, YYYY m/s. This notation is used because rocket engines have different properties in atmosphere and vacuum. XXXX relates to in atmosphere, YYYY is in vacuum.

Thrust to Weight Ratio (TWR) – This is pretty straight-forward. It’s the ratio of your thrust to your weight, but remember that weight changes, both with gravity and also as the mass of your rocket reduces when it burns fuel. The important thing is that we don’t build any rockets with a TWR of less than 1. If we do this, the rocket will not have enough power to lift off. A TWR of 1.4 usually does well enough, but the higher the better, generally speaking.

Stability Augmentation System (SAS) – This helps keep your rocket flying the way you want by housing several reaction wheels that give a torque to the rocket, hence turning it without control surfaces or any need for an atmosphere.

Orbital Terminology:

Periapsis/Apoapsis – These are the closest (periapsis) and furthest (apoapsis) points of your orbit. A truely circular orbit has equal apoapsis and periapsis. This is generally measured from the average surface level (or sea level) of the planet you’re orbiting.

Ascending/Descending Node – These are the points where your orbit crosses the equator of the planet you’re orbiting. The ascending node is at the point you go from the “Southern” hemisphere to the “Northern” hemisphere, the descending node is the opposite.

Inclination – This is the angle between the equatorial plane of the body you’re orbiting and your orbit. A highly inclined orbit will cover more of the planet’s surface. A polar orbit is an orbit with a inclination of close to +-90 degrees.