Rockets Question (Higher Level)

I'm researching techniques for interstellar space propulsion for phys c/w this year, and I want to demonstrate some usage of rocket equations, but I have not the first idea of what to do, having never been taught this tier of mechanics.

The main thing for me is working out the mass of propellant/fuel required, so consider the (offhand) question:

A ship accelerates continuously (not constantly ofc) until it reaches A-Centauri 4 light years away. If it has a useful payload of 500 tonnes (of random scientific garbage), how much fuel will it require (assuming 1 kg of fuel provides 10000 N of force )??

It would be wonderfully useful if you could show me a method/how to approach this sort of question
:biggrin:

Help.
Please.
:biggrin:

Reply 1

EEngWillow

11

Original post by 4Papavera

I'm researching techniques for interstellar space propulsion for phys c/w this year, and I want to demonstrate some usage of rocket equations, but I have not the first idea of what to do, having never been taught this tier of mechanics.

The main thing for me is working out the mass of propellant/fuel required, so consider the (offhand) question:

A ship accelerates continuously (not constantly ofc) until it reaches A-Centauri 4 light years away. If it has a useful payload of 500 tonnes (of random scientific garbage), how much fuel will it require (assuming 1 kg of fuel provides 10000 N of force )??

It would be wonderfully useful if you could show me a method/how to approach this sort of question
:biggrin:

Help.
Please.
:biggrin:

A question you might want to consider first:

Where is your ship accelerating from? Is it on the Earth's surface, or launching from a space station? (Space is a vacuum obviously, so space station doesn't have to contend with friction in atmosphere etc).

Anyway.
Have you learned about momentum and Newton's third law? (Mechanics 1 in OCR Maths, no idea about physics syllabi, they've changed since my A Levels). That's basically all you need for a rough idea of the force needed to get moving. Being a vacuum it'll keep moving in the direction it sets off at once it gets going...if you ignore the gravitational pull of everything else up there. You'll want to do some research on the Tsiolkovsky rocket equation - it considers the idea that an object can apply acceleration to itself by expelling part of its own mass at high velocity in the opposite direction to travel (due to the conservation of momentum)

You could also look at different methods of spacecraft propulsion, we've got pretty advanced these days :wink: