# Realistic Space Travel Situation? [closed]

So, I'm creating this language and culture for these humans, where in the future, technology has allowed them to build orbital factories and they have successfully created one working prototype of an intergalactic star-ship.

Thousands of French (at about 30% of the total ship population), American/English (30%), Spanish (20%), and other Europeans from smaller countries board on a treaty agreed to by the members of a UN council.

Naturally, the language and culture are influenced heavily by the three main categories (and the people leaving for the other planet have studied the common language, which has a phonology and grammar structure based on French, English, Spanish, etc.).

They leave for a pre-agreed planet which would be similar to portions of the Earth, given that they use the Terraforming module installed on the ship. They would reach the planet after a period of 300+ years at maybe 50% c, as near-light-speed travel had not been invented yet (and simply because I hate the idea of things going faster than or at the speed of light; Einstein would have a headache).

Naturally, life-support systems include: a carbon dioxide to oxygen converter, a gigantic farming and ranching system, a water source (maybe from a water-recycling unit that re-uses all shower water, waste water, etc.?), an artificial gravity source (simple enough, just rotate), and etc. Their engine would primarily use matter-antimatter reactions to gain its initial velocity, and thrusters are arranged at three angles to the center engine for turning (however slow it would be) the ship.

My questions are:

1. Is this a realistic situation? Could somebody provide a reasonable answer for why they would agree to go on this mission (maybe as a method to demonstrate mutual peace after a devastating war, or maybe just to explore space)?

2. Is space travel realistic on this scale (as in, millions of people on one spacecraft)? Would a spaceship this size have structural integrity? Would local stars on the journey knock the ship off course enough to cause problems?

3. If, during the travel (a few years before landing), they went through an asteroid belt unexpectedly (which is sketchy at best, maybe they couldn't turn fast enough?), could the structure be damaged enough in a focused impact so that one of the modules would break off?

And, if it did, assuming that this was one of the very specialized modules (maybe full of transportation devices for when they landed, or maybe full of vital electronics), would their technology timeline be sufficiently offset to set them back into a pseudo-Renaissance or Imperial time period, where the people are too busy colonizing the new worlds to advance technologically?

This is all very theoretical and highly improbable, but it is one of the axioms of my world. I want it to be isolated from Earth for centuries, but still have very poor technology so innovations would need to be redone. I'm sure I could rework it if it's implausible.

EDIT: I suppose the size of the spaceship and life-support systems would be a concern given this amount of people, so I'll rework the initial population to be about ~10,000 people. Is that a better estimate?

## closed as too broad by Lostinfrance, kingledion, Zxyrra, James♦, AifyJan 20 '17 at 18:28

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• Please modify your title so that it is descriptive of the situation. This will help people searching in the future with similar questions to find your question if it gets useful answers. Something like "Is my generational-star-ship scenario realistic?" – SRM Jan 14 '17 at 7:09
• Please, one question per, well, question. Once you have something settled, you can ask a follow-up questions. – Mołot Jan 14 '17 at 7:59
• As Molot's comment suggested, this isn't so much a question as a request to critique your whole story premise. For that reason I have voted to close. In order to get better answers please split it up into at least the three numbered questions you list (the cultural/political one, the one about the size of the spaceship, and the one about hitting an asteroid belt), or better yet, four questions because the second part of your question (2) is really a question in its own right. – Lostinfrance Jan 14 '17 at 13:56
• The amount of antimatter needed could power the life support for aeons. It will be the most expensive part of the plan in energy and resources. Expect living in the a spacehabitat of this size orbiting the sun to be commonplace. Why would they even want to teraform? More spacehabs can be built from asteroids if room is needed. – Donald Hobson Jan 14 '17 at 22:27
• You have seen the movie Passengers, right?   :-)   ⁠ – Peregrine Rook Jan 15 '17 at 1:36

TLDR: I think your population is too large to support. A proposed reason for getting thrown back in advancement: The population divides over the centuries and a small faction of scientists sees their in-fighting and decides they won't get the mission done. The small group sets off for the planet first, taking the tech with them. The majority of the population of the planet then has to start from a low-tech level but you would have advanced over-seer people.

Is this a realistic situation? Could somebody provide a reasonable answer for why they would agree to go on this mission (maybe as a method to demonstrate mutual peace after a devastating war, or maybe just to explore space)?

Millions of French (primarily, about 40% of the total ship population), American (maybe ~35%), Spanish (20%), and other Europeans from smaller countries board on a treaty agreed to by the members of a council on the UN.

One thing to consider is who is it that will own this colony once they land? Clearly there are still plenty of separate countries on earth. We can all claim ownership over something purely scientific like the ISS but how would that work for some strategic resource on the planet? Perhaps these separate countries would encourage their citizens to go because it provides them a greater hold over the colony. (Of course nationalism might die down on the way over...or they may build big divides between them).

Another is that clearly the french are way more successful at convincing their citizens. At the moment France has a population ~65 million and the US has ~320 million, assuming no dramatic changes there would probably be a similar difference. The French beating the US in population means there was probably something going on in France at the time (perhaps over population).

An exploration mission probably wouldn't take so many millions. I would assume they have already found something out about the planet that means they want it. Of course it is a massive trip back so I doubt they are thinking about trading it. Perhaps whatever they discover is on the planet is something they can use to boost space travel further.

Is space travel realistic on this scale (as in, millions of people on one spacecraft)? Would a spaceship this size have structural integrity? Would local stars on the journey knock the ship off course enough to cause problems?

They would reach the planet over a period of 300+ years, as light-speed had not been invented yet (and simply because I hate the idea of things going faster than or at the speed of light; Einstein would have a headache).

So the closest star is ~4.4 lightyears away: $$\frac{4.4*c/year}{300 years} \approx 0.15 c$$ Where c is the speed of light so your ship has to go at 15% the speed of light. You will, however, have to deal with accelerating your ship out of our solar-system and decelerating as you go in to theirs. This HUGE ship going at 15% the speed of light would require a lot of energy. You might want to think about the size of ship.

Now we come to population. I'm not entirely sure on numbers but minimally you said 'millions' of french at 40% so lets say 2 million. That makes five million people on this ship as an initial population.

1) That population will increase quickly if you don't have some sort of child restriction. 2) It is difficult to figure out how much space you will need but as a comparison Atlanta has a population ~5 million and is ~320$km^{2}$, you can probably squish people in a bit more but we're looking at a big spaceship once you stick your engines, farms for 5 million AND room for them to grow into.

I would reduce the initial population and let people have more children whilst on the journey.

If, during the travel (a few years before landing), they went through an asteroid belt unexpectedly (which is sketchy at best, maybe they couldn't turn fast enough?), could the structure be damaged enough in a focused impact so that one of the modules would break off? And, if it did, assuming that this was one of the very specialized modules (maybe full of transportation devices for when they landed, or maybe full of vital electronics), would their technology timeline be sufficiently offset to set them back into a psuedo-Renaissance or Imperial time period, where the people are too busy colonizing the new worlds to advance technologically? This is all very theoretical and highly improbable, but it is one of the axioms of my world. I want it to be isolated from Earth by centuries, but still have very poor technology so innovations would need to be redone. I'm sure I could rework it if it's too unfeasible.

As JDlugosz already pointed out, it would have to be badly planned to have you hit the asteroid belt (or perhaps planned that you would hit it, sabotage maybe).

I think perhaps the people would divide over the centuries of travel, French not taking orders from any Americans or whatever factions you choose, that could escalate to whatever level you needed. Then when they get to the planet they don't share as was intended, didn't stick to the education system proposed and so none of them are at the level of technology they were intended to.

You could have one small faction see how the majority won't work together so they make off with all the tech and stay away from the others. Could be a team of scientists who have kept their focus on the actual aim of the journey.

This would give you a world with a large population who don't have the tech and a small minority of people living in a hidden location with very advanced tech.

• The closest star is quite the opposite of “intergalactic”, and changes the problem by 5 or 6 orders of magnitude. – JDługosz Jan 15 '17 at 9:34
• I forgot that, rather important, bit of the question. You're right Andromeda is 2.5 million light years meaning even travelling at the speed of light you take 2.5 million years to get there. Thanks for pointing it out @JDługosz – Lio Elbammalf Jan 15 '17 at 12:36

during the travel (a few years before landing), they went through an asteroid belt unexpectedly

No, that is not realistic. That is a cartoon or a bad sci-fi movie. You need to understand where asteroid belts lie and what the course of an interstellar ship would be.

an intergalactic star-ship … would reach the planet over a period of 300+ years, as light-speed had not been invented yet

Ask yourself, how far away is the nearest other galaxy? Compare that with, how far does light travel in 300 years?

Would local stars on the journey knock the ship off course enough to cause problems?

No, you would stay away from them or plan for their effects.

this scale … use anti-matter

How much energy does this take? Compare that with how much energy humans use today and with the definition of K-I and K-II civilizations.

• Can you expand on your statement about asteroids?  If the ship travels 300 years, maxing out at 0.5 C, it goes somewhere between 75 and 150 light years.  We’re struggling to detect planets orbiting other stars — can we detect asteroid belts at 100+ ly? And how about asteroid/meteoroid/rock clouds that are not near stars?  Sure, it gets easier to detect them as you get closer to them — but it becomes much harder to change course to avoid them when you’re doing 0.5 C. – Peregrine Rook Jan 15 '17 at 1:37
• @PeregrineRook see this answer. It is far, far easier to build observatories than an interstellar ship, so expect the route to be well surveyed. Uncharted rogue worlds and asteroids are not what the OP was asking about; I'm commenting on his mental model of “space” being way off. – JDługosz Jan 15 '17 at 9:29

Just want to point out that Atlanta has a relatively low density (the highest density ever known on Earth was about 110x higher). You can go much higher, certainly for a ship that can fully use 3 dimensions. There would still need to be a lot of space for farming and stuff and I am not disputing that, it's just not quite as much as you would imagine.

• I've never been to Atlanta I just googled to give myself some sort of ball park figure, it was rather naive I suppose. Thanks for keeping me on my toes @Mart – Lio Elbammalf Jan 14 '17 at 21:34
• This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review – James K Jan 15 '17 at 11:22
• @JamesK Yeah sorry was trying to answer the question above but made a whole new comment. By the time I noticed it was too late. Sorry kinda new to this. – Mart Jan 15 '17 at 12:09

If, during the travel (a few years before landing), they went through an asteroid belt unexpectedly (which is sketchy at best, maybe they couldn't turn fast enough?), could the structure be damaged enough in a focused impact so that one of the modules would break off?

At least for our own solar system, it's pretty unlikely that even a small moon sized ship, large enough for "millions," would accidentally encounter anything large enough to cause serious damage. When planning missions to outer planets, NASA doesn't even consider the locations of asteroids because they are so spread out that the chances of hitting one are insignificant, here's a good website that explains why: http://www.universetoday.com/110276/why-the-asteroid-belt-doesnt-threaten-spacecraft/

For other stellar systems, it's hard to say. Around a dimmer star, for example, the habitable planets may be much closer to the star, with shorter, faster orbits. An asteroid belt closer to the star would occupy a smaller volume and might be much denser, more like the rings of saturn. If you want a system in which it's more likely that the spacecraft is struck by an asteroid, you could build one. I would recommend making the system surround a dim star with large mass, so that it is reasonable for the habitable, rocky planets to have small orbits, and an asteroid belt (or 2?) could exist with more asteroids in a smaller area. It looks like the other questions are a little more contentious so I'll just stick to this part.