Here is an old question I answered on Quora. The answer is a bit patchy, but I like the idea of using asteroids as space ships and bases. There are just waiting for us to hollow out. I'm sure the new asteroid mining companies (Deep Space Industries, Planetary Resources etc) are centering their road maps on this. If not, they should.
Image source: Deep Space Industries
What technology would we need to develop to explore the closest 50 stars with manned craft? What plausible timescales would be involved for such exploration.Edit
51 stellar systems lie within a radius of 5 parsecs (16.3 light years) from the sun. The nearest is Alpha Centauri at 4.3 light years. So what is the minimum tech we would need to devise?
Things to consider:
A propulsion drive that would facilitate human time frames. Please stick with non-fantasy tech: warp drives breach the light speed limit, worm holes have unsurvivable gravitational effects (if you could even find one), teleportation via quantum entanglement has no application to macro-scale objects, etc.
Space medicine to halt bone and muscle deterioration
Shielding technology to counter cosmic radiation
Craft shielding for deflecting space debris at high velocities
Fuel and food supply transportation
The short answer is that there is no practical way to achieve interstellar travel without 'fantasy tech', within a human lifetime, but here are a couple things to think about:
- The warp drive is currently in development - Harold White and his team at NASA have started work on a Warp Drive in 2012 based off mathematical variations from Miguel Alcubierre's 1994 paper titled, "The Warp Drive: Hyper-Fast Travel Within General Relativity"
- White's calculations bring the required mass-energy to 1,600lb, down from the mass-energy of Jupiter based off Alcubierre's equations. This is currently the lead tech possibility for interstellar travel.
- Space itself has no super-luminal velocity restriction
- If the warp drive works out, then star travel will just take a couple of weeks. The ultimate game changer.
Existing/not too far off 'non fantasy' fantasy tech - asteroid space bases and space craft
The following concept is far better suited as a interplanetary space cruise ship, but can be adapted to very long term interstellar travel. Note: Voyager one will take 80,000 to achieve this feat with its current velocity.
Stage one: Become independent of earth's resources and hence gravity well, via space mining of asteroids.
Stage two: Construct 'space only' craft at stable gravity liberation points, which can collect, move, harvest and construct with astroid resources.
Stage three: build a low gravity moon base (inside a mountain) for manufacturer of complex industrial parts and assembly and improve low gravity industrial processes.
Stage four: Recycle a Trojan asteroid in resonance, and in a near earth orbit. For example, - a known 300 meter asteroid in a 60 degree preceding orbit to earth at L4 (stable gravity point/spacetime topography).
Image: Earth's Trojan asteroid 2010 TK7
Stage five: Once asteroid space base construction is perfected, move on to replicating the process with a fast moving massive near earth asteroid For example, quasi-satellites of Earth include 2010 SO16, (164207) 2004 GU9,(277810) 2006 FV35 2002 AA29 and 3753 Cruithne.
Stage six: Once the fast moving quasi-satellite/asteroid construction of the ship is completed, external force must then be applied to get the object out of the sun's orbit. The mass of the object would be greatly reduced from being largely hollowed out, but a substantial amount of energy and clever astrophysics would be needed to achieve the feat.
- There are currently no viable hibernation tech, but there is evidence that it is possible. Identifying the genes in our blueprint is probably a step in the right direction. Also, hibernation just lowers metabolic rate, so people would also need to periodically wake up and there is no evidence that hibernation will extend a person's lifespan, so it would be purely a food/water conservation strategy. Extending a human's lifespan may make such long trips more appealing to more people.
- The mean velocity your ship will travel through space will be a function of many factors, including:
- energy source,
- energy storage capability,
- propulsion efficiency,
- journey 'start velocity'
- one-way/return trip fuel utilization,
- risk appetite for catastrophic damage with space objects given craft robustness and planned velocity dynamics.
- the amount of assisted velocity that can be achieved within our solar system, via the interplanetary transport network -
, but also by hitching a ride on a near earth asteroid and constructing your ship from the material mined from this asteroid. This approach requires far less energy/force (as per F=Ma) to accelerate the large ship required for inter-generational travel. The relatively small interceptor craft would require a far smaller amount of energy to get the required velocity of the asteroid and it could catch it at a velocity minimum inflection point.
Further notes on stages as per above:
Stage one: become resource and energy independent of earth's gravitational well. Mine metal, water, fuel (liquid oxygen, hydrogen methane etc) from micro-gravity objects - i.e. asteroids.
Stage two: Mine, hollow out, and build a massive space base inside a near earth stable orbit asteroid. Companies like Planetary Services and Deep Space Industries are currently looking in the very early stages of mining asteroids. If they are successful, then a natural extension is to seal up the mined asteroid and use it as a space base/spaceship. They can be massive bases since they are manufactured in micro-gravity, and can be internally manufactured in stages. They also require no/low natural resources from earth. Large scale 3D printers would be required, as per Deep Space Industries business plan.
Large 3D printers print more 3D printers, mining equipment H2O to Oxygen, etc. There are over one million 1km+ asteroids in the inner asteroid belt.
The asteroid space base/craft solves a number of problems:
- The asteroid would provide ample protection from cosmic rays
- They will be far more robust against very high velocity collision with space objects
- The 'internal fitout' would be a tiny fraction of the cost of building a ship from scratch and this construction methodology does not damage earth's environment.
- Internal construction of later stages of an asteroid ship can be undertaken during the journey, allowing for an earlier departure date
- the asteroid is recycled after it is mined.
- hobby farm sized fields/hydroponic operations can grow food in large internal caverns within the asteroid.
- asteroid can be spun for gravity, which helps avoid health problems associated with the deadly duo of micro-gravity/cosmic radiation, such as muscle wasting, blindness, early onset of dementia etc.
- build substantial manufacturing facilities in stable near earth orbits - ie sun-earth, earth-moon Lagrangian points (near earth stable gravity points in resonance with earth's orbit). 2010 TK7 (300m diameter Trogan asteroid) precedes earth at L4 and should be our leading contender for a large scale space base.
- Propulsion, you would probably need an atomic source of energy to convert water to liquid hydrogen and oxygen. It would depend on resources were available on the selected asteroid, and what would need to be 'imported'. Solar will clearly not work away from the sun, and an energy source is required to produce rocket fuel.
- Propulsion system would need to be independently hinged from the asteroids spin, and supported with stabilizer rockets (a little like the action of a helicopters back rotor).
This is all highly speculative, but this is the best approach I can concoct.