Sstrhsrtj

This is the first part of a series of questions I'll ask about a self-sustaining colonization ship. I'll keep editing this post as things unfold.

Note: I'm currently reading about some stuff that people called my attention to in the comments. The question will soon be edited with some more information to make it a bit more robust.

Some Context

The setting is kind of a low sci-fi. In this universe there are no FTL drives - in fact, the maximum level of technology is not even close to that. Humans rely on "old fashioned drives" with a little twist. They're more efficient than the ones we have today, but bear in mind that this is a very-near-future-tech scenario.

Humans are in the early stages of the space colonization era. "The Colonists", as they're known, are huge ships equiped with the tools to ensure the crew's safety and to help populate the new worlds.

For the sake of simplicity, assume that the colonized planets are exactly like Earth (but untouched by men). This series focuses on the ships and their trips to the new worlds. In order to estabilish boundaries, these trips might take from 20 to 200 years.

This first question focuses on the building process of a Colonist. The original idea is that the ships are built completely outside of Earth in Space Shipyards located in orbit (kind of like the ISS).

The Question

Is it possible to build such an enormous ship outside of Earth?

Bonus points if you can estimate:

• How much would it cost;


• How long would it take;


• A rough approximation of this thing's dimensions (comparison another ship from fiction, like the Enterprise, is valid).

Here's a list of things to consider for this question:

• The Moon is a fully terraformed colony in this setting. This colony is able to provide 1/5 of a given raw resource, like iron or wood;


• This is a collective effort of humanity, which means that, as long as the Earth and the Moon have the resources to do it, money is of no consequence;


• Each ship has to have enough space for at least 100 people plus whatever they might need, including, at least, accomodations, heavy machinery, fuel and life-support (basically oxygen. Food and other physiological needs are not being taken into account here 'cause they will be object to a subsequent question);


• The Shipyard is already there and it has all the manpower and the tools to assemble the ship - but not the materials. They must come from either the Earth or the Moon;


• The shipyard idea came from the notion that a ship this big would never be able to leave Earth because of its weight. I don't know if that's correct (but I think it is). In any case, if the shipyard is not necessary, feel free to kill it.

First off: passenger space.

(TL;DR: The passenger space would have to be pretty big, but we can cut corners and bring it down to Star Wars size.)

If you want to prevent the 100 or so passengers on the ship from getting claustrophobic and eventually insane, you'd have to provide a good amount of space for each passenger, especially if some of them live together. 10 x 10m might be a nice start, since you could most likely fit every basic house thing in that area.
However, this already means that the ship would have to be at least 1000 x 1000 m in size for passenger space alone.

So, you could instead offer the passengers some form of 'class' system, where the ones who pay more get bigger rooms. Let's say those who opt for smaller rooms get a 6.5 x 6.5 meter space. We'll also say that out of the 100 rooms, 35 are the large ones. So, this takes the ship's total size for passenger space down to at least 772.5 x 772.5 m.

When you consider that such a huge area is just passenger space, it might not be super attractive, but at least all the passengers will have a nice time.

(For reference, that's about the same length as an Acclamator Class Landing Ship in Star Wars.)

Oxygen

(TL;DR: The oxygen storage, if concentrated in one room, would have to be almost as large as the equatorial radius of Ceres. Instead, we'll opt for a life support system spread across the entire ship's roof, which saves lots of space and only adds a few meters to the ship's height.)

Oxygen may or may not be a bit of a problem. Since we, on average, breathe in around 11,000 litres of air a day, over just 100 years all 100 people on board would need about 401,766,420 litres of air. That's about 401,766.4m³. Let's say everyone has personal oxygen systems that don't take up much space and thus we can subtract around 40-50% of the oxygen space. We'd still need 220,972m³ for oxygen space.

As a final caveat to reduce this ridiculous required space, let's say we've invented an alloy from tungsten and iron or something. The alloy is ultra-resistant to leaks and therefore we can remove the 10% of extra oxygen we took (just in case). That's down to 198,875m³. Which is still WAAY too much space.

So, we'll instead have life support systems in each individual room instead of having one big oxygen storage room, and since space stations like the ISS have it installed along the roof, it takes up far less space since it's spread out. We'd probably only need to add 5 or 6 meters to the ship's roof. We're at 772.5 x 777.5 meters now.

Leaving Earth

(TL;DR: This section is pretty short, so there is no TL;DR.)

While the space shipyard idea is presumably more efficient, it adds extra danger since the colonists must take a transport up to the shipyard. The transports could crash and explode. So, let's try to employ some methods to get it to leave Earth from the surface.

-A giant magnetic 'sling' on a huge runway, similar to the system that aircraft carriers use but for a giant spaceship.

-Simply tilting the ship up and attaching some incredibly strong thrusters to it. This might not be very efficient and could have a high chance of failure.

-A runway that leads up to a super-strong launching ramp. With the addition of some medium-strength thrusters, this could get it to escape velocity.

Any of those three are doable, as well as the space shipyard. I say you should pick which one to employ. The problem is, the shipyard might be a bit too futuristic, since you'd somehow have to get the shipyard into a stable orbit, and I can't even start there.

Final Dimensions

So since we've sacrificed around 700 square meters for passenger space, we'll have to keep everything else low. The cockpit will probably be the largest of all the extra rooms, since a large crew would be required to control a spaceship of this magnitude. We'll say 10 people man it. A cockpit of around 15 x 15 meters could comfortably house the people, their positions, and all the crazy machinery.

There should be a few kitchens and living-room type places to cook up simple snacks and relax with friends. These could be around the sides of the ship and would probably take up about 16 x 16 meters, or maybe a bit more.

Since those specific rooms are all we really need, plus maybe an engine room (we'll give all that stuff 50 x 50 meters and put it in the back), we're now at a size of 853.5 x 858.5 meters. Approximately.

That's about the same as a Devore Imperium Warship from Star Trek.

As a few final notes, I'd estimate cost to be around 5,000,000,000,000 dollars, which seems like a lot but would actually be feasible if the entire world came together.

Hope this ridiculously long post helped!

The main issue with long term colony ships of this sort is the mass of supplies and requirement for virtually 100% recycling of everything. This isn't possible with today's technology, but we do know that humans need a certain amount of food, oxygen and water per day, and then try to discover the machinery or mechanism to make up the CLSS (Closed Life Support System). Your ship will then be scaled to carry that amount of mass, plus whatever "backup" materials you think you need (raw materials to "top up" the system, spare parts to keep the system in repair etc.

This is a NASA document which should give you an idea of the order of magnitude masses needed: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19670025254.pdf

And this is a more modern iteration:
https://ttu-ir.tdl.org/bitstream/handle/2346/73083/ICES_2017_311.pdf?sequence=1&isAllowed=y

The next issue is radiation shielding. Any spacecraft going into deep space needs to protect the crew from cosmic radiation and other events, so will require a massive amount of shielding. The "Millenial Project" (my go to book on these maters) suggests that a shield of water 5m in depth is needed. An equivalent amount of rock or metal is likely needed if you don't want to use water. The mass of the spacecraft can then be calculated by using the shape (i.e. a cone or sphere) to calculate the area and working out the mass of a 5m thick shield of water or rock surrounding it.

Since we now have a vessel which is lily the size an mass of an aircraft carrier, conventional rocket technology isn't going to work. The problem is you have to accelerate the mass of the ship, plus the mass of the fuel (including the fuel you are going to use to decelerate at the other end), which means that you are looking at a geometric expansion of mass as you try to increase the ships acceleration or speed.

The best way to get around this is to use some form of external power, like a massive solar sail (at this scale perhaps a series of solar sails tehtered together like a bunch of kites). You could either dive close to the Sun and unfurl the light sail, or use massive banks of lasers to drive the sail.

Paradoxically the way to get out of the Solar System fast is to first arrange that your probes dive towards the Sun with the probes facing edge on to minimize radiation pressure. Then turn almost face on at perihelion(closest to the Sun) and blast away.

If closest approach is 1/10 of an Au, the final velocity is:

420 km/sec

And if the materials(some sort of unobtanium:)) could withstand an approach to 1/100 Au, only 1.5 million km from the center of the Sun, and therefore only 800,000km over the seething surface(!), the final velocity of our interstellar probe would be:

1330 km/sec

Astute readers will notice that just as the escape velocity of a massive body varies inversely as the square root of the starting distance R from the center, so does the final velocity of our Solar Probe.

https://www.quora.com/How-fast-could-a-theoretical-solar-sail-starship-get

Actually, at this scale, you would not really be able to see the ship. Solar sails will have to be unimaginably large

So you will be looking at a very large, very massive ship. Propelling it by diving into the Sun to provide the maximum amount of Solar energy provides the velocity necessary to reach Alpha Centauri in about 1000 years. Presumably the crew at the time of arrival will arrange to "dive" into Alpha Centauri to provide the energy to brake into stellar orbit and then explore the system.