Exactly. A civilisation that has built a Dyson Sphere could command enough energy to send 30 million Venture Stars outwards per year. That’s why it seems a little puzzling that we haven’t noticed any Dyson Spheres in the galaxy yet.
Let’s face it, practically speaking it’s an impossible task to accomplish with our present level of technology. Even if we somehow got there, what then? There may be no planet suitable for human life. In that case, how do the descendants of the original crew get back?
Another consideration is that the rapid advance in technology vis-a-vis the length of their journey makes it very likely that a much faster technology will be invented before they are even half way there. In that case, the sleek modern ship may dock with them, they may be asked to abandon their outdated jalopy of a spaceship and transfer over, and they may finish the trip their dead parents started.
This is a good comparison because it demonstrates that any spaceship capable of high fractions of lightspeed is in fact an extremely deadly weapon.
How were they going to ship the mcguffin back in the first movie, and how did they go home at the end?
First off, building a telescope capable of studying a planet in detail is much easier than building a ship that can actually go there (especially since, once the telescope is built, you can easily re-use it for other planets). There’s no reason why we’d ever go anywhere blind.
Second, if you’ve already got a ship capable of supporting humans for decades or centuries, then every planet is a planet suitable for human life. If nothing else, just build a copy of the ship’s life support system on the planet. But with the advantage that you have a nearby star you can use for energy, and an abundance of raw materials to make stuff from.
We aren’t going to send a physical spacecraft to any star system until we have reached the limits of telescopic astronomy, many generations of telescopes in the future.
First we will catalog all the nearest exoplanets by transit and stellar wobble. We’ll probably need a next-gen telescope like Luvoir to get any details about rocky planets around sun-like stars. So a timeline of maybe 2035-2040 for the next level of observations.
If we find some candidate planets with atmospheres, we may then do detailed observations with interferometers and dedicated scopes like HabEx. 2040-2050
If all that turns up some candidate planets within reasonable distance, the next step would be a Solar Gravitational Lens survey of the planet, which could allow us to see the planet in roughly 1024 x 1024 resolution. We could track weather patterns, vegetation, etc.
Even that last scope requires a trip of about 650 AU to get to the sun’s gravitational lens focal point. That’s a long way, four times farther than we’ve sent anything before. None of us will see this in our lifetime.
If we don’t find planets with habitable atmospheres and temperatures in our local region, humans will likely never leave the solar system. We aren’t going to travel hundreds of light years in any realistic scenario with anything like a civilization we would recognize.
.
Exactly. CJ Cherryh’s Alliance universe suggest just that - that large interstellar ships create large habitations around planets where more often, there are plenty of resources in system to feed that station, but usually no viable biospheres. Better than an interstelllar ship, once in a system there are plenty of new resources to continually feed the space station - more oxygen, water, carbon, metals, etc.
As for 3.6x10^23 Joules, based on a ship mass of 10^7 Kg - the gamma factor is the key - 0.4
If you had perfect capture of mass-to-energy onversion, you would need to add 40% more to the ship mass to be fuel; but then need a bit more to also accelerate the fuel you haven’t used so far. (An integration formula)
If your fuel mass is conveniently hydrogen and deuterium and 0.7% of it is compeletely captured fusion energy, then you would need 1/0.007 more than ship mass for fuel (143 times more). At this point, the extra fuel needed to accelerate the so-far-unused fuel is not trivial.
So less weight? 10^7 Kg is 10,000 metric tonnes.
Each ship will weigh about 20,000 tons, with a length of 690 feet and a beam of 130 feet , the news site reports. USS Lyndon B. Johnson, a Zumwalt class destroyer.
Of course, warships are not designed for weight savings, but it gives you an idea of the scale. How much humans and cargo do you expect to send?
The other solution mentioned is to go slower. For 0.1c I get 1 minus gamma being about .005 a substantially less demanding number. (which for hydrogen fusion, means an additional 72%-plus of fuel) But then, you’re talking 43 years plus to Alpha Centauri, so essentially one way with no backups. You better send a decent sized craft.
As I mentioned earlier, the Venture Star design uses no fuel to accelerate. When it leaves the Solar System, it is entirely propelled by laser beam. Exactly how this works in practice is not described; also how it decelerates when it gets to Alpha Centauri is glossed over, and there is no detailed plan for getting back. But apart from that it is all good.
Much beloved by science fiction.
Even more fun, since IIRC from readings decades ago, the typical laser is at most 10% efficient in terms of energy in vs. light energy out? So whatever math you do, multiply those solar cells by 10; Maybe situate them on Europa to use the moon as a heat sink for that extra 90%. Which means multiply by 100 to get the same energy as you would in Earth orbit.
A good post, @Sam_Stone , but to expand on it:
Only about 1% of Earthlike planets would be detectable by transit, because it depends on the orbit of the planet being oriented right relative to us. The good news, for exoplanet science, is that that fraction is very easy to calculate for any given sort of planet, so once we make a decent number of observations, we can make very good estimates of the numbers of various sorts of planets in the Universe. The bad news is that if we’re interested in specific planets, we’re 99% likely to miss the one we want.
Stellar wobble can detect planets that transits can’t, but that method is still dependant on inclination, so we still couldn’t detect planets in orbits with high inclination relative to us.
The good news, though, is that interferometers can detect any planet, if the interferometer is large enough, and that’s a step we’d be taking anyway in our exoplanet studies. Given enough time and resources, you just take a look at every star within 100 lightyears, or whatever, even the ones you don’t have any a priori reason to suspect of having planets.
That’s the gold standard, of course, but the downside is that you can’t re-use the scope: You’d need a separate mission for every target you want to look at that way (well, you could probably reposition it for different objects in the same system). So that’s a step that we’d only take for the most interesting planets (whatever our criterion for “interesting” is). Still much cheaper than an interstellar mission, of course.
Yup, TANSTTAFL. And it’s also tricky to use orbiting solar collectors with a launch laser: You really want those things braced against something big, like a planet, to handle the recoil (and they will have recoil: Remember, they’re transferring enough momentum to get a ship up to relativistic speeds).
Maybe the Dyson sphere builders leave gaps in the shell (or use shutters, etc.) in any direction where is a star system within detection range. It would only require sacrificing a small fraction of the total output. It would make good camouflage.
I read an article that described the actual difficulties in building a Dyson Sphere. Apparently the mass needed to build one would require dismantling several planets. And this was only one of the problems. As a mental exercise, they seem like a great idea but I doubt they will ever become a reality.
Agree, most people don’t comprehend the scale of large numbers. For example, one million seconds is about 11 days . One billion seconds is roughly 31.5 years. That’s a big order of difference.
One trillion seconds is equal to about 31,710 years. So, yeah, I think it might be hard for your average Joe to wrap their head around the power output of 64 trillion Saturn V rockets.
Pack the entire surface of the earth (including the oceans) with Saturn V rockets. Use hexagonal packing to fit as many as possible. At 33 feet diameter, you can fit about 5.8 trillion Saturn V rockets. Gonna need 10 more earths.
Space is really, really big, and relatively speaking the speed of light is really, really slow but the speed of light seems to be a universal speed limit. The faster you go the more energy it takes to go just a little bit faster, and what you are trying to move that fast gets more massive. Until your mass becomes infinite and requires an infinate amount of energy to get to the speed of light, or C. But you will never get going that fast.
Finding ways to get around the slowness of light, the huge distances involved, and the energy needed, well we have a word fo that. It is called Magic.
An even funnier comment I read once - who really wants to get on the first ship to Alpha Centauri? The first ships will probably be barely capable of maybe a few percent of light speed - 5% (0.05c) would mean 80 years or more to get there. Your children born on board would be old when the ship arrives. And when they get there - they’ll be greeted by the passengers on the newer ship developed a couple of decades later that could go 0.2c - as long as nobody collides en route with the first unmanned probes sent there at 0.01c.
Remember, time dilation is a thing. It doesn’t really become noticeable until close light speed (e.g. a trip to Alpha Centauri at 10% light speed would seem to the travelers to take 43.45 years instead of 43.67 year but, at 70% light speed, the trip would seem to take 4.45 years instead of 6.24 years; at 95% it is 1.44 years instead of 4.6 years). So, if you can get very close to light speed travel times for the people on the ship can be trivial. Crossing the galaxy would be easily done. The only problem is, when you come back home, many tens of thousands of years have passed.
You are describing a Dyson Swarm which was Dyson’s original notion.
Dyson did not detail how such a system could be constructed, simply referring to it in the paper as a ‘shell’ or ‘biosphere’. He later clarified that he did not have in mind a solid structure, saying “A solid shell or ring surrounding a star is mechanically impossible. The form of ‘biosphere’ which I envisaged consists of a loose collection or swarm of objects traveling on independent orbits around the star”.[6] - SOURCE
Not exactly, though my idea would likely be implemented as a swarm.
Even with only partial coverage, a swarm should be detectable, since it would alter the spectrum compared to what theory should predict. But what if the swarm elements went transparent, or altered their orientation, or even generated their own light as they passed between the host star and a likely populated system? They could be made virtually invisible, with little actual energy cost (since stars only occupy a negligible fraction of the night sky).