I think “trade winds” is better analogy than “super highway”.

Yes, by far! And to extend it, we're at the "canoes" (or maybe "swimming and surfing") stage regarding our technology for exploring those horizons.

Feels more like we threw someone in and watched to see if they could doggy paddle back.

For interplanetary, I think it’s more like we looked at some flotsam in the water spinning around and wondered if we could make a canoe based on that principle get to the next island, having only just tippy-toed into the water up to our ankles just to prove it wasn’t immediately lethal.

(Scale difference: Uranus is 7800 times further than the moon [0], so if wading to ankle depth is 1m from the shore, then the metaphorical island is 7.8 km away — pretty close of the distance between the closest parts of Portsmouth and the Isle of Wight [1]).

[0] http://www.wolframalpha.com/input/?i=Distance%20to%20Uranus%...

[1] https://goo.gl/maps/rvV5cXeb8i8xbVwr9

Really enjoyed these water and swimming analogies, but I think air and flying analogies would be better, since it's just so damn hard to fly. You see the birds and dream, but to actually take off takes something else, and even then we stay relatively close to the ground (within our atmosphere). From someone who's not seen an airplane, to then keep going into the stars is pretty crazy. There's a saying that to become enlightened you have to be willing to fall upwards. I think there's an ingredient of that in exploring new frontiers.

Surprise place name as example

I came here to complain that the headline is a rickroll. Not all their fault, though ... as they say, the researchers called it "a true celestial autobahn" (bottom of abstract). The article's title? "The arches of chaos in the Solar System". le sigh

https://advances.sciencemag.org/content/6/48/eabd1313

To put that into perspective, it took Voyager 2 8.5 years to reach Uranus, and 12 years to reach Neptune.

That was thanks to a full "Grand Tour" alignment of the outer planets that allowed gravity slingshots at each destination. This unfortunately only lines up once every 175 years.

In-situ resource utilization to mine propellant from the Moon and near-Earth asteroids could bring a dramatic improvement in ∆v budget (and hence travel time), using only conventional rocket propulsion.

If you think about it, your car wouldn't get very far either without being able to refuel. If you wanted to travel across the country, the fuel tank would have to be dramatically larger, and then you'd have something very much like the rocket equation's exponential mass to ∆v relationship (except here it would be mass to distance traveled) as you have to carry more fuel just because the other fuel is weighing you down. As a result, eventually your fuel tank would be close to the entire mass of your car, and you might actually even require a two-stage vehicle, with your car detaching from a large tanker halfway across the country to finish the trip.

And good luck getting back.

Is that entirely true though? Many of our highest impulse engines have fewer problems with the tyranny of the rocket equation, but also have low thrust. The beginnings of trips are going to be slow even if the end is not.

Using these paths for the beginning and end of journeys may make a lot of sense, even if they make no sense at all in the middle.

> The beginnings of trips are going to be slow even if the end is not.

Endings too. You cannot just slow down. No brakes in space. And if your engine is low thrust, you'll need a while to slow down too, unless your goal is kinetic impact unto your target.

> You cannot just slow down.

If you engineer to survive it, aero- and even litho-braking are alternatives where you can “just” slow down, without using onboard reaction mass.

Thank you for introducing me to "lithobraking." What a wonderful euphemism for "crashing into the planet" (albeit a controlled crash, or, as you say, engineered for survival).

Isn't what a plane is doing while landing on the airstrip?

So in the worst case the average speed is half of the maximum speed. Still something attractive.

We can reach Mars in a couple months. Beyond that, the only further places I could imagine humans wanting to go is Europa or Titan, maybe Ceres.

There are lots of gravitationally attractive resoures scattered throughout the asteroid belt.

In a couple months like, what, once every 10 years or something when it's closest to earth? Otherwise iirc it takes much longer

Only 26 months in the Earth/Mars system, in fact. And that's still the fastest way to go, which is the only thing that's relevant for crewed spaceflight. Doesn't matter how much you're saving on gas if you still need to bring enough snacks for the drive.

Dude Hohmann transfer to Mars is less than a year.

Who is "Dude Hohmann" ?

Dude, Hohmann...

All this hype about automation, but we still want to launch meat into the space.

[3] It's called the moon, not Luna.

In many other languages it is Luna. Latin, in particular. https://en.wikipedia.org/wiki/Luna