Submitted by bigmikemcbeth756 t3_zxspl1 in Futurology
PercsNBeer t1_j224kyz wrote
Reply to comment by Fraun_Pollen in I have a question about generational ships. by bigmikemcbeth756
Which part of the technology exists? We use gravity to throw shit around the solar system because it becomes exponentially harder to launch a ship with enough fuel to do anything else. The space station is constantly resupplied. I'm curious which part of this is feasible to you.
teachersecret t1_j228n8d wrote
I’m not the OP, but…
I guess it depends on what the “generation ship” is doing, how many people are actually aboard, and how much cash we want to throw at it.
Just hanging around our solar system in a graveyard orbit with a fairly small generational crew? Probably doable with current tech if money was no object. You don’t even have to do much recycling if you don’t care about the cost. A human only needs 700-800kg of oxygen per year. Water can be recycled, but a human “only” needs 30,000 gallons for a lifetime. That’s 250,000 pounds of water… but you could launch that with a single ares V. Food is a challenge (between 70,000 and 80,000 pounds needed for a lifetime), but you can probably put enough raw nutrients up there to make an edible slurry drink that would stay viable for a few centuries… and you’d have plenty of light and water for hydroponic greenhouses for additional variety. Energy isn’t that hard, either. If we didn’t care about the obvious safety risk, we could launch enough nuclear fuel to run a ship for centuries using current tech, with plenty of spare reactors and fuel shot up there just in case. Use the water in the hull as rad shielding and micro meteorite protection (ice makes a decent shell that can be “repaired” with a little heat and a squirt gun). Build a nice sized space station for everyone to live in, put plenty of spare parts up there, and you’re golden.
You can reduce those needs significantly if you do even a bit of work trying to recycle and reuse water/air and focus on things like lab grown foods and growing spaces.
None of that is impossible with current tech. You could lob enough food, air, and water to keep a small crew alive for generations… if you wanted to… and had an insane amount of money to spend.
Going to another star? Forget about it.
incarnuim t1_j22nars wrote
Going to another star would be feasible if you did all of the above to a captured asteroid. A captured asteroid, 10km diameter (which is pretty BIG, and massive) could provide enough space and shielding for an interstellar journey (you could hollow out the inner 9.5km worth of asteroid and still have a radiation/micro-meteroid shield that was 'only' 250m (800ft) thick of solid silica-aluminate. You could is the ablated material of the asteroid as propellant for an electro-propulsive rocket system. Rotate the asteroid for gravity on the inner surface of the shell, etc...
A sustainable generation ship would probably require DD fusion. You just couldn't carry enough fuel to do it with fission or DT fusion...
The problem is coming up with an asteroid that big in a captured orbit (i.e. captured by Earth or possibly the Moon), and then supplying the necessary ∆V to break the capture and start the thing on its way....
mindofdarkness t1_j229tru wrote
The feasible part is the fictional part. Unfortunately real spacefaring has to deal with any problem that could happen, not just the ones the writers researched and thought were interesting enough to include.
gatsby365 t1_j22senw wrote
Like, who has authority over things like breeding & family patterns. Just because you can technically build a generational ship doesn’t guarantee it will last more than 2-3 generations before descending into outright civil war.
Fraun_Pollen t1_j227ykj wrote
The Project Orion is one example of something we could build with todays tech that could reach a decent percentage of the speed of light. It’d still be a crawl compared to scifi, but it’s achievable
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