Hard Science Help Wanted for Story

[BolianAuthor]

Hi, all...

I am seeking someone, or a group of people, who can help me out with some hard science aspects for a story I'm writing, that I want to keep as much hard sci-fi as possible. Here is what I need help with...

I want to make mention of human settlements in the Alpha Centauri system, but I need to know how long the trip to the system took, with NO FTL. In my story, the fastest human ship can travel from Earth to Jupiter in two months time. So, with that figure, how long would it take to get to Alpha Centauri?

Also, I want to show the habitable planet in the Alpha Centauri system to be as in-line as possible with what hard science or hard sci-fi would depict. I would like some speculation as to what kind of look the planet would have... what kinds of plants, lifeforms, climate, etc. I'm assuming this world is in the habitable zone.

I would like to go with a lot of what is said in the Wiki article for the Alpha Centauri system, at http://en.wikipedia.org/wiki/Alpha_Centauri , but if there is anything that I might add, such as what a possible time system would be, like what a year would be, or a day, etc, on AC.

I would also like to formulate a true possible speculation on what the AC system might look like, as the possibility of gas giants forming there is not too great. Would there be an asteroid belt? As many planets as our system? Less? If anyone wants to help me, or collaborate on this project with me, let me know. Thanks for any help.

 

[Verteron]

From figures on Wikpedia, Jupiter is between 741 million km and 817 million km from the Sun, and the Earth is between 147 million km and 152 million km and from the Sun.

This means Jupiter is anywhere from 589 million km (same side of the Sun) to 969 million km away from Earth (opposite side of the Sun). Let's assume your space travelers were sensible and took the trip to Jupiter when it was 600 million km away from the Sun.

I'm not going to calculate any fancy shmancy business such as escape velocities or gravitational slingshots or anything because I can't remember how and it's Sunday afternoon and I'm lazy.

So, a question -- does your ship travel at constant velocity (i.e. do all its acceleration at the start, then run there with the engines off), or does it accelerate out halfway, swing around, and decelerate for the other half of the trip?

In the first case, a short burst of rockets followed by coasting followed by braking at journey's end, 600 million km in 2 months would require a speed of 115 km per sec. To get to Alpha, 4.2 light years away, you'd need about 11,000 years (yes, thousand!).

In the second case, 300 million km in a month from a standing start of 0m/s, a simple s = (1/2)at^2 gives a = 2s/t^2 so your acceleration needs to be around 0.02 m/s^2, which is pretty comfortable for Humans (given we're used to 9.8m/s^2 standing on the Earth) and might be somewhat achievable with some kind of Ion drive.

Using this engine for reaching Alpha Centauri, presuming it could operate for the full 4.2 light years, would mean 2.1ly of acceleration, and 2.1ly of deceleration. At your 0.02 m/s^2, this would take 45 years from a standing start, so 90 years for the entire journey. Slightly better, but still not within your average human's lifespan.

 

[BolianAuthor]

Verteron,

The ships used to get to AC use a method kind of like BSG... in the same way that the ragtag fleet jumps every now and then, and then just coasts a while, these ships fire up the engines for some periods, and then coast a while... but the engines are on much of the time.

If I can use ion drives, realistically, I will use them. The 90 year method would work, and the time is of no worry, because the ships going there are large generational ships.

 

[Verteron]

The ships used to get to AC use a method kind of like BSG... in the same way that the ragtag fleet jumps every now and then, and then just coasts a while, these ships fire up the engines for some periods, and then coast a while... but the engines are on much of the time.

If you're definitely going to Alpha Centauri, you should use all your fuel to accelerate as much as possible as early as possible in your trip. This means you'll spend as much time as possible at the highest possible speed. Boosting and coasting is not a good strategy for interstellar travel on the kinds of engines that will take you to Jupiter in two months... the BSG ships are far faster even in sublight.

 

[BolianAuthor]

^

Okay... I'll do that, then. I was just worried that maybe doing a big burn like that initially would use up a lot of the fuel quickly, and thought that a gentler method would be a kind of "leapfrogging" method. But I see your point.

 

[mnop945]

Spam deleted. - Spiff

 

[TerriO]

Had to sort a thing or two on that post, but definitely warning for spamming, comments to PM.