Richard Smith

@vsz The explorers typically spent at most a few years at sea, while these people will spend 2 decades. And while the explorers had a whole ship to wander around and dozens to hundreds of other sailors to interact with, these will be confined to a tiny spaceship (if the spaceship is even somewhat realistic, it will be tiny, as increasing size by even a little requires increased fuel for acceleration and deceleration, then you need more fuel to carry the fuel, and more fuel to carry the fuel to carry the fuel, and so on (tyranny of the rocket equation)).

Also, why would a crew stay behind, even if the world is a "Garden of Eden"? No matter how beautiful and stuff it is, you can't get any of the benefits of civilization there. So no new entertainment, no company, no support, no healthcare, depending on how good automation is, no good housing, no furniture, no medication, no clothing, etc, etc, etc.

Couldn't the sexual stuff be solved by just chemically castrating the crew?

If you are willing to have fantasy elements, then give your organic pilots precognition or something else that gives them an edge over drones. Although, in that case, you would probably end up with disembodied, augmented brains wired directly into the controls instead of actual pilots.

You could have a skeleton crew. The eggs are just there to prevent inbreeding.

Why do you need AI for frozen eggs?

I think we're just talking past each other at this point.

Why can't you use an immortal crew? Why can't you use frozen eggs?

If you actually traveled interstellar distances, you'd necessarily be able to live pretty much indefinitely in the void, so you'd presumably mine asteroids and moons to build rotating habitats at your destination and not actually live on planets.

That's tidally locked, one half is baked and the other is freezing

And their viruses won't be able to infect you, but their bacteria might, and you wouldn't be able to eat anything there because the biochemistry would be different, and your plants wouldn't grow in the soil and atmosphere.

Even planets with life will have atmosphere you probably can't breathe, and those will be extremely rare.

Almost nothing is going to be habitable in space

Okay, sorry for bothering you

I'm not proposing a specific system

What is your point?

I know about Project Orion'.

I'm saying that with millennia, tens of millennia, etc, of time to there is a real chance that these engineering problems will be solved. And you would need to bring some sort of nuclear reactor anyways, as carrying enough chemical fuel to power your ship there would be impossible, and batteries are even less energy dense than chemical fuel.

The powerpoint provided states that their system will get from Earth to Mars in 115 days. Granted, it might be exaggerated, as it is a sales pitch, but the thrust does not seem to be completely negligible.

I don't understand rocket mechanics well. omnicalculator.com/physics/ideal-rocket-equation When you put in a higher thrust velocity in this, initial mass (propellant + payload) decreases, given constant final mass and delta v.

What do you mean?

Or something like that. Of course, constructing those would require the overcoming of numerous technological and engineering hurdles, and each solved challenge would only reveal many new challenges.

I'm not specifically saying VASIMR is the system in question, just that there are theoretical methods to get extreme exhaust velocities, some into the millions of m/s with antimatter,

web.mit.edu/mars/Conference_Archives/MarsWeek04_April/… Some estimates for VASIMR seem to be much higher, and the company that made this does not seem to be a total fraud.

Sorry for bothering you.

I know you fly out the other side. Proxima Centauri is about 0.2 light years away from the other two, so even if you fly past it at high speed, wouldn't it allow you to slow down by some amount?

And if you build extensive infrastructure in the Oort cloud, you could just start your trip there by constructing your entire colony ship (or fleet) within it.

en.wikipedia.org/wiki/Alpha_Centauri#Confirmed_planets There seems to be at least one planet, and if you time your approach right, you might be able to decelerate with the gravity of one of the three stars in the system, then enter orbit around one of the other two.

Why couldn't you get that far out?

Wait, why can't you slow down with gravity assists? If you fly in the opposite direction as the planet, won't you slow down? Wikipedia even says "Due to the reversibility of orbits, gravitational slingshots can also be used to reduce the speed of a spacecraft" and that it was done by Mariner 10 and MESSENGER. And isn't the interplanetary medium much denser than the interstellar medium, and as you need to carry a sail anyways for the pusher laser, you might as well use it once in-system?

And couldn't you also shave a bit off the delta v needed to slow down using some gravity assists off of planets near the targeting stars, and by braking on interstellar gas using a large sail of some sort?

Also, what do you mean by "the Merlin engine having a mass of 630kg, plus 120 for an astronaut in a space suit"? Also, what do you mean by "Every gram of fuel you spend slowing down at the construction site in the kupiter belt is two grams you could have spent slowing down at Alpha Centauri. Sure, you can leap frog resources out in smaller trips taking more time, but the overall total cost goes up and the biggest problem is slowing down at Alpha Centauri"?

it would need a bit under 100 million tons of initial mass. Am I doing something wrong?

I don't understand physics that well (I only took 1 intro physics course years ago, and it was only about classical physics and some EM, and I forgot all of it), but I plugged some numbers into the rocket equation calculator. If you have a 50 million ton craft which needs 34 km/s delta V and which has 50,000 m/s exhaust velocity (same as NASA's hypothetical VASIMR ion drive, and some antimatter or black hole based systems could be better),

Your answer states "ever," and "ever," is a really long time, considering how resource rich the entire solar system is. Provided we do not kill ourselves off, (and the chances will drop as we spread throughout the solar system and improve technology) we will have literally millions or billions of years to build infrastructure and develop technology, and a settled solar system with even a partial Dyson swarm will have an economy billions or trillions of time larger than our own.

Also, if you launch from the Kuiper Belt or Oort cloud and push yourself out with fusion powered lasers (fuel with water ice from comets), the Sun's gravity will be much weaker and you won't need as much delta V to escape (though that doesn't solve the problem of slowing down).

2. You probably would not be launching an interstellar mission just off of Earth's resources. People would expand off the planet at some point, as if they do not, the heat from industry and such would heat the planet faster than it radiates away, cooking everything directly (not relying on greenhouse effect, so source of energy does not really matter for this). Whether through carbon nanotube space elevators or projects such as launch loops/mass drivers, it is possible to greatly reduce launch costs, which would enable mining of asteroids, dwarf planets, and moons.

And as there are no physical laws prohibiting extreme life extension and biological immortality, you might not need a generation ship, either. People don't really die of old age, they die because their organs fail and their brain degrades. Even now, many scientists are working towards curing cancer, heart disease, Alzheimer's, etc, so unless humanity gets killed by grey goo or an asteroid or something, clinical immortality will probably emerge at some point, whether through genetic engineering or nanotechnology or cyborgization or organ cloning or stem cell therapy or some combination thereof.

If you need animals and plants on arrival, you could keep frozen seeds/embryos, or gametes, or just DNA, depending on how advanced your biotechnology is. This can also be used to deal with population bottleneck issues. You could get away with using a tiny (or AI) crew which grows new humans on site.

1. Just because modern humans cannot maintain a biosphere does not mean that it will not be doable in the future. And you directly took a quote from Wikipedia, but did not mention that "The second closure experiment achieved total food sufficiency and did not require injection of oxygen." In hundreds or thousands years, we will likely have the technology to maintain a biosphere. Also, you do not need to maintain a biosphere anyways, just bring some hydroponically grown plants and algae bioreactors to feed your crew.

Why can't the government make the cars illegal? The government makes stuff illegal all the time. Just now, there is a debate over whether e-cigs should be banned or not. Across the US, automatic weapons are banned (except for some rare old ones which were grandfathered in and such). If the government doesn't like something, that thing will get banned.

And Elon Musk is more likely to invest in his own Hyperloop idea than some cool-sounding but ultimately impractical ground effect cars.

Also, what would the benefit of these cars be over high speed rail, which is faster, safer, and uses mature technology? It is already extensively deployed in Europe, China, and Japan, and mass transit is highly developed in many countries other than the USA.

But developing the roads (even if they are computer systems and not physical roads) will be the responsibility of the government, as businesses do not have the right to force people to keep open ground in certain areas and to not build buildings and such there.

And I know Europe isn't a country.

These cars would also be very dangerous in accidents. In real life, the majority of people in car accidents survive uninjured or with few injuries. However, these cars will probably have to be light to float off the ground, and they will travel at great speeds. If they do crash, any within the car or anyone who gets hit would have a much smaller chance of surviving, and anyone they hit will be turned to paste.

Also, giving people flying cars makes terrorism easier. While many important buildings have large concrete flowerpots or bollards protecting them, it would be much harder to defend against a vehicle moving at 160 kph several meters off the ground, and a fast moving vehicle filled with ANFO would be able to topple most buildings or turn crowds into puddles of gore. Governments would not be happy to give people widespread access to flying vehicles.

If you have the resources to build smart highways in suburban and rural areas for flying cars, you could build high speed rail more easily, and it would be faster to boot.

Also, you say that these cars will travel at 160kph, but modern high speed rail can go at 200-400 kph (and this is just conventional high speed rail, not even counting maglev trains which can go even faster), and has already been built in many countries such as China and Europe (and not just in major metropolitan areas but all across the country).

In the modern world, around 30,000 are killed in car crashes in the US each year, and 2 million are permanently injured. It will be worse with ground effect vehicles, which will probably be harder to operate even if altitude is controlled by a computer, as they will move much faster than ordinary cars and as there will be turbulence and such to deal with. They will also probably be much more mechanically complex and expensive than ordinary cars.