# The Naked Scientists Forum

### Author Topic: what is the best way to calculate trajectory?  (Read 1582 times)

#### Dege

• Full Member
• Posts: 67
##### what is the best way to calculate trajectory?
« on: 13/02/2010 22:54:23 »
hey guys! well i am dealing with some model rockets and i wanted to find the trajectory of the rocket that weighed 32.2pounds, but i could not find on the web, a easy explained method. so can anyone help me with a method that is well explained please?

#### Soul Surfer

• Neilep Level Member
• Posts: 3345
• keep banging the rocks together
##### what is the best way to calculate trajectory?
« Reply #1 on: 13/02/2010 23:59:05 »
This depends precisely on how much detail you want to predict things and how accurate you want your predictions to be.

The trajectory of an object launched with a known velocity in a known direction neglecting air resistance is simple and in all physics text books.

Secondly adding in air resistance is quite difficult.

Finally if the object is a rocket, for full accuracy it is vital to know:-

1 The thrust of the rocket throughout the burn period.  This may vary a lot, particularly for simple solid fuelled rockets.

2 The mass change in the rocket as this thrust is produced.

3 The effect of any vectoring of the thrust and steering of the rocket.

This is a vastly complex subject and way beyond the scope of these pages or standard texts.

This can be simplified a bit if your rocket is a commercial product and specified to have a "specific impulse".  This means that the total thrust and mass change is treated as if it happens instantaneously and the spent rocket mass is launched at its final velocity in the direction that you point it.
« Last Edit: 14/02/2010 00:07:17 by Soul Surfer »

#### The Naked Scientists Forum

##### what is the best way to calculate trajectory?
« Reply #1 on: 13/02/2010 23:59:05 »