Could we build a starship using current technology?

[generic mook]

Suppose you had limitless resources and political will, and you wanted to build a starship. Your goal is to maintain constant acceleration of 1g for a period of at least 1 year (long enough to travel to a distant station and recharge).
1/ Could we do this using existing technology?
2/ How massive would such a vessel have to be? (Assume a human crew of 6.)

[jeff_wilson]

Originally Posted by generic mook

Suppose you had limitless resources and political will, and you wanted to build a starship. Your goal is to maintain constant acceleration of 1g for a period of at least 1 year (long enough to travel to a distant station and recharge).
1/ Could we do this using existing technology?
2/ How massive would such a vessel have to be? (Assume a human crew of 6.)

1. Not even.
2. There is no way of knowing.

[Humabout]

For what it's worth, accelerating that much for that long would run headlong into relativistic effects that would sap all efficiency. After three or four months, you'll probably be going plenty fast enough to achieve your goal, and without using up nearly so much fuel.

Also, you'll make it far more feasible if you cut back the acceleration and increase the velocity of exhaust. That'll increase efficiency, reducing fuel costs and making year-long constant acceleration more possible.

Of course, fuel for a year's worth of constant acceleration is probably way too much to be doable today. Remember that the more fuel you amass, the more mass you have to move, which requires more fuel. The only real way around that is either refueling or getting a more efficient engine. And the latter requires better tech, and the former typically requires launching fuel out ahead of you, which requires a lot of planning, time, and even more fuel. It gets kinda crazy.

[Dustin]

For comparison, a proposed unmanned interstellar probe design (Project Longshot) using nuclear pulse propulsion and relatively few advances on current technology compared to other designs achieves an acceleration of .001g (.01 m/s2) after 70 years of flight, and twice that after 100 years of flight (when it reaches Alpha Centauri B).

[Humabout]

Why does acceleration increase over time? Usually, that's relatively steady and velocity increases over time - that is, when it isn't instantaneous like most modern rocketry uses.

[Balor Patch]

Originally Posted by Humabout

Why does acceleration increase over time? Usually, that's relatively steady and velocity increases over time - that is, when it isn't instantaneous like most modern rocketry uses.

Presumably mass decreases as fuel is consumed.

[Johnny1A.2]

Originally Posted by generic mook

Suppose you had limitless resources and political will, and you wanted to build a starship. Your goal is to maintain constant acceleration of 1g for a period of at least 1 year (long enough to travel to a distant station and recharge).
1/ Could we do this using existing technology?

The chances are approximately halfway between zero and nil.

One gee for 1 year, I mean that's well into relativistic territory. You're talking about more energy used by the starship than the entire Earth uses. We don't even have a theoretical idea of how to do such a thing. The closest dreamy SFnal concept would be the Bussard ramjet, and we certainly can't build one of those right now (and there's reason to think the concept itself is unworkable).

The most powerful real-world-proposed space drive I know of is Orion. You could use that, in theory, to send very large spacecraft to most of the planets of the Solar System in reasonable time, but it wouldn't even get into the neighborhood of one gee for a year.

[Dustin]

Originally Posted by Balor Patch

Presumably mass decreases as fuel is consumed.

Yes, that's my understanding here. Thrust is fairly constant and the vehicle's mass is decreasing as fuel is consumed.

[Anthony]

Originally Posted by generic mook

1/ Could we do this using existing technology?
2/ How massive would such a vessel have to be? (Assume a human crew of 6.)

No; a chemfuel rocket of the required size would have mass exceeding the mass of the observable universe and wouldn't manage 1g.

[scc]

Originally Posted by Johnny1A.2

The chances are approximately halfway between zero and nil.

One gee for 1 year, I mean that's well into relativistic territory. You're talking about more energy used by the starship than the entire Earth uses. We don't even have a theoretical idea of how to do such a thing. The closest dreamy SFnal concept would be the Bussard ramjet, and we certainly can't build one of those right now (and there's reason to think the concept itself is unworkable).

I calculated how fast a ship would be going after accelerating at 1 G for a year once, without accounting for time dilation, and if I remember correctly you're going at ~.99C