Another take on creating gravity in space.

[Willshikabob]

Alright, so, my partner and I are well under way with our science fair project (thanks guys), and we still have some questions. How should we test/replicate/simulate our prior conclusion? Should we equate it? We were thinking of making a graph yet we still need some help. Also, after the fact I realized that no matter where, gravity will always be present. Is this correct? If so, I hear everything creates gravity so it would affect our equations ever so slightly, and fuel requirements would differ based off of that. The question we're tackling is: "How much fuel would it take to sustain standard Earth-like gravity (excluding gradient and launch) for 1000 days in space. It would be fantastic if people can help us. We've given credit to all of www.scienceforums.net, thank you so much! 

[Janus]

If your aim is to maintain a constant 1 g environment for your passengers, external gravity will have no effect on the answer.  External gravity will effect the speed and trajectory of your ship, but not what your occupants feel. It would take just as much fuel to accelerate your ship through empty space far from any galaxy for a 1000 days, as it would to just hover above the surface of the Earth for 1000 days.  The difference is that in the first case you will travel a great distance and the in the second you will go nowhere.

The fuel requirements would rely on the type of propulsion you have.  At 1g for 1000 days ship time you would reach a velocity of 99.3% of the speed of light.

With a typical chemical rocket this would require many, many, many, many, times more matter than contained in the entire known universe as fuel.

An Ion engine would bring this down,  but it would be still more than the known universe's mass.

To maintain this acceleration for that long would require a propulsion system well beyond anything we even have on the drawing boards.

Even a engine capable of an exhaust velocity of 10% of the speed of light would need 1.87e12 kg of fuel per kg of ship to maintain this much acceleration for that long. This is the equivalent of a small asteroid for every kilogram of ship.

The best theoretical drive possible would be a "photon drive", a rocket that pushes itself with light.  With such a drive you could theoretically maintain a 1 g acceleration for 1000 days at the cost of 16 kg of fuel per kg of ship mass.  However, this assumes the ability to convert matter to energy with 100% efficiency and to use all of the converted energy to drive the ship.  Since 100% efficiency is not practically attainable, you would end up needing more than this in reality. A drop to 90% efficiency would increase the fuel needed by 38%

 

[Willshikabob]

3 hours ago, Janus said:

External gravity will effect the speed and trajectory of your ship

Would this also affect fuel if it's changing the trajectory and speed? I mean, there's no destination for the rocket, so changing trajectory wouldn't matter. Although, if some extremely large body in space pulled us into a course that would end up colliding with the ship, there would have to be some major plot changes, neh? Asides from that, it would take more fuel to get back to our set speed.

Edited January 11, 2018 by Willshikabob

[pavelcherepan]

On 1/11/2018 at 5:06 AM, Willshikabob said:

How much fuel would it take to sustain standard Earth-like gravity (excluding gradient and launch) for 1000 days in space

If you want to constantly accelerate in your direction of travel the fuel requirements will be immense, it's not plausible as it will require a significant portion of all matter in Solar System as fuel. On the other hand if you go for the spinning arrangement then in ideal case only energy you'd need to expend is the amount you need to start the spin. After that since you'd be travelling in vacuum, it should keep going for extremely long period of time, and by that I mean millennia.

Edited January 12, 2018 by pavelcherepan