How much fuel do I Need?

Question

Lets say im in a rocket and im flying to somewhere 74799 km from earth. How much rocket fuel is needed?

Answer 1

You would need some massive litres! Seeing as there is a lot used up on departure and getting the rocket moving.

Answer 2

You are in a rocket and you are already flying. You're on your way! Take off took care of all your fuel requirements. You just coast along at 13,000 kilometres per hour and you'll get to your destination in six hours.

You will not be travelling very far, not even halfway to the moon, so you don't intend to go very far. You'll need a canister of fuel to slow you down and another canister to

take off if you intend to return to earth. Once you hit earth's atmosphere you'll slow down abut you'll need a lot of fuel to pilot your space shuttle to a perfect landing. How much? Ask N|ASA. You didn't p;ut anything about getting home in your query. Sounds like you intended to get marooned.

Answer 3

How much do you weigh? How much does the rocket weigh? Which fuel are you using, and how efficient is its engine? You'll need to answer all those before you can answer the main question.

Hmm... the engine's efficiency might vary depending on how hard you're running it and how fast the rocket's going... and how high it is. So actually, you might be better off doing some practical tests.

Is there any way I could convince you to buy an electrically powered car instead?

Answer 4

some liters...

Answer 5

Well, depends on many parameters - what kind of rocket, which kind of trajectory do you fly? What engines does the rocket have? How much does the structure of the rocket weight? what is the payload?

It is just like with cars. A small car as a different fuel consumption as a heavy loaded truck.

You can calculate the maneuver budget required to reach 74799 km distance, and design the mission around that value. The maneuver budget is mostly independent from the rocket you fly, there are only very few correction factors required once you know how the rocket looks like. The maneuver budget tells you effectively, how much velocity changes you need for reaching a trajectory in space. This is also called the "total impulse" or "total velocity change". A typical engineering symbol for it is "Δv*", but this varies from country to country.

Let's say, you already have a rocket which can launch you to 250 km LEO (that requires about 9200 m/s total impulse for a first estimate)

A transfer orbit from 250 km to 74799 km would for example require you to change your velocity from the velocity required to be inside a 250 km parking orbit by additionally 2792.06 m/s.

So, your rocket will have to get you 9200 + 2800 m/s = 12000 m/s total impulse.  No single stage rocket based on current available technology could achieve this change, so you would either need multiple stages or more experimental propulsion systems - for example nuclear thermal propulsion.

If you spacecraft weights 25 tons (like the Orion CEV), a typical nuclearthermal rocket would have the following rough parameters (real values depend on detailed engineering and can be more or less):

If 92% of your rockets mass will be liquid hydrogen fuel, you will have a payload mass fraction of

λ = (e^(-12000/9000)-0.08)/0.92 = 0.19956 or about 20%

That means, 20% of the lift off mass of the rocket will be the 25 tons of the capsule -> The whole rocket will weight a tiny bit more than 125 tons at liftoff.

This means 92 tons of the rocket will be hydrogen fuel, 8 tons will be engines, tanks and structure and 25 tons will be spacecraft.

Not included is the weight of Greenpeace activists chaining themselves on your rocket to prevent you to use an open nuclear reactor for reaching your goal.