30 years old so a tad dated, but a solid story.
I love the off kilter future tech of making audio recordings on minature CDs
Big fan of the series but hard sci-fi it is definitely not! True, the humans don't break the laws of physics, but Eros certainly does, and if season 3 tracks the books then that gets turned up to 11...
There has been a shot with a screen showing the Nauvoo's trajectory to Eros which was quite ridiculous too, though.
I know it seems dumb but the preposterousness of that scene ruined the episode for me. I've played too much KSP :D
Many assumptions are built into this.
First, that fusion drives don't need much reaction mass. This is part of the F =(d/dt) (m*v) needed for rocket thrust. The mass you throw away at high velocity (dm/dt) has to be sufficient for you to be able to accelerate a several million kg ship to 1-10g.
Second, and related to the first, they are not using energy efficient Hohmann transfer orbits. They are using fast transit orbits to get between sites. Which means that their engines are continuously operating, first accelerating away from the initial site, finally decelerating towards their destination site. You still want to orbitally match on the destination, so your delta V isn't measured in km/s orthogonal to the destination.
Third, a fusion reactor will be massive, if for no other reason, due to the shielding you need for the hard x-rays/gammas coming off. Massive in this case doesn't mean large, rather having lots of high Z mass (lead and other heavy nuclei elements that have a very high cross section to Xray/gammas). You likely will need several 10s of cm of such material. Which means you have to accelerate lots of "inert" mass as well as your reaction mass, as well as your ship.
I don't expect shows/movies to get all the physics/science right. I do expect them to at least make an effort to hint at why we should suspend our disbelief in this. There was a single episode with a side arc on the ships engines. They let that arc go unfinished, which is a shame, as that was potentially very interesting. The protagonist in that arc is assumed to be dead, though somehow, he narrated his experience. The arc was about drive efficiency, and by extension, specific impulse/thrust.
The other slight physical violation is in the instantaneous communication of the protomolecule infected individuals. Maybe they have their own EPR pairs they interact with to ensure instantaneous comms. But its rather hard to exceed C for information transmission as far as we know right now.
So ... yeah ... there are some violations that bug me.
 fixed spelling errors
Engines not existing yet doesn't break any laws of physics, except possibly those governing material science. The main obstacle for the engines would be to find a material that survives the temperatures involved. The reaction part is pretty accurate, except perhaps that it goes way closer to the theoretical optimums than what our current technology in the area can achieve.
> and in S1, transit between Ceres and Eros on a passenger ship doesn't require weeks/months. Transit from earth to Jupiter/Saturn systems are achievable in days.
No, it really isn't, even if the show gloss over the travel times (because it doesn't make good TV). It is very, very clear in the books that the distances involved take weeks, months or even years to travel.
As for the protomolecule, that one DO break the laws of physics as we know them. But there will be more of that shortly.
DOES. But yes this is what I meant, the protomolecule (aka Eros aka Julie) plays all sorts of games with momentum, mass, velocity, all sorts of things. Remote-fusion-damping, later. I'm fine with it. Science fiction after all.
Only if you believe marketing bullshit.
So far, Musk has done everything he's promised: decent electric roadster, electric luxury, SUV and mid-priced cars, powerwalls and roof panels, re-usable light and heavy launchers for obscenely low prices and turnaround times, tunnels under LA. This stuff is all real and working. You can quibble about schedule slips or whatever, but none of this is vapor. In fact there's already an F9H payload overshooting Mars orbit.
So where's the bullshit?
As SpaceX is still recouping the technology research investment, 95% may be a stretch, but 80% reduction is not that far of really, it will probably be very close to that if they are able to reuse fairing.
So 80%-90% has already happened.
SpaceX blames this on NASA. So Orbital ATK didn't have that problem because, reasons?
Unbiased sources on launch costs are really hard to find.
And about the Mars thing, it's not going to happen. SpaceX works for contract work, not for dreams. Nobody's going to pay for that. Why not the moon first anyway? Almost just as cool and way more practical.
I haven't seen any practical unpartial sources for savings from reusable rocket stages.
I expected the hackernews community to be more skeptical.