It's fun to estimate how hot the exhaust of a torch ship must be, and how much mass should it expend on constant 1G sustained for days.

Rockets exchange impulse with the exhaust at a linear rate (mv), but put the kinetic energy into it at a quadratic rate (mv²/2), so increasing mass efficiency by increasing exhaust speed / temperature costs more and more. Realistic with fusion reactors, to the extent to which compact fusion reactors themselves are realistic. Or even with fission reactors, in the form of bombs (see project Orion).

Nothing like the current simple, low-tech chemical rockets.

There's an interesting speculation as to how an Epstein Drive could work in reality. The heat management problem is pretty central:

http://toughsf.blogspot.com/2019/10/the-expanses-epstein-dri...

The discussion at the bottom of the page has also a lot of interesting ideas.

It's a very interesting discussion, thanks!

I can't describe the feelings I feel in the last couple of weeks. It really feels like we are living in a (dystopian) future. Elon Musk is working on a brain-chip, people are wearing robot-arms and legs, space-travel gets faster and easier year by year etc.

Just crazy, I am stoked to see what new technologies and possibilities will arise in the next few decades.

The thing with the prosthetics is that I feel like there's hundreds, if not thousands of companies and individuals working on them, but there doesn't seem to be any convergence, or more importantly, mass production - meaning that prosthetics remain expensive and made-to-measure. This is a thing with a lot of things that look very high-tech or science fiction.

That said, video calling was the realm of exclusive, high-tech / demos for a long time, then without really being aware of, it's been available in everyone's pocket for a long time now. It went from near-sci-fi to mainstream in the blink of an eye.

Prosthetics haven't solved the bandwidth problem i.e. how do you connect them to the nervous system.

Well, Elon Musk's Neuralink is claiming they're close at least, but I could also imagine someone coming from the other direction entirely, and making a robot limb that was autonomous and worked with the wearer instead of being directly controlled (but the failure mode would be no fun...)

Sensory input is the other 50% of the game that remains unsolved. If Neuralink's robot works it will be a game changer for artificial eyes, limbs, everything.

Besides that a robot limb can't be autonomous in it's movement as most movements we do are asymmetrical and thus it needs input from the other limb as well.

I watch with grim satisfaction how well the cyberpunk books predicted our present and near future from 30+ years ago. (Satisfaction, because what's coming looks familiar, we've been warned.)

I only started reading and watching Cyberpunk related things about a month ago, so it's interesting to see how far we already are.