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Excellent news. If any show deserves to survive it's Expanse. Today with SpaceX pushing us towards Mars it feels like we're living in pre-history of Expanse which is based on the most realistic SciFi I've seen yet. We need this.

Sounds like you’ve not seen StarCops:


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

Actually this is a better fuller link, for the time being:


> based on the most realistic SciFi I've seen yet

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...

Well, there must be some fiction in sci-fi as well :). A small amount of magic is usually allowed. If you ignore the protomolecule, the rest is quite hard.

Not the gravity assist slingshot trajectory.

That was acknowledged by the showrunner and was down to poor planning between shooting and CGI work: http://www.danielabraham.com/2017/04/04/guest-post-losing-sc...

There has been a shot with a screen showing the Nauvoo's trajectory to Eros which was quite ridiculous too, though.

Interesting, thanks for the link.

I know it seems dumb but the preposterousness of that scene ruined the episode for me. I've played too much KSP :D

That part was the biggest break in suspended disbelief for me. I get the protomolecule - that's basically magic - but the grav assist? Yeah, no, the Roci just zipped around Jupiter's orbits like they had some Star Trek sublight drive.

Well ... laws of physics are being broken by their ships. They use fusion drives (which don't quite exist yet), 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.

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.

[edit] fixed spelling errors

> Well ... laws of physics are being broken by their ships. They use fusion drives (which don't quite exist yet),

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.

> As for the protomolecule, that one DO break the laws of physics as we know them

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.

>Today with SpaceX pushing us towards Mars

Only if you believe marketing bullshit.

I believe.

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?

My favorite part - beyond watching SpaceX embarrassing the critics over and over and over again, with reusable rockets, bringing down launch costs by 80-95%, out-launching the rest of the world, and just surviving in general - is that if you can do Falcon Heavy, you can do BFR, which gets you Mars. The engineering keeps proving itself, no need to buy any marketing spin. The only debate left is whether it's going to be closer to 10 years from now or 20.

>with reusable rockets, bringing down launch costs by 80-95%

Nice joke.

SpaceX is supposedly selling F9 flights for $50 million already, while the competition is selling comparable flights for $150/$170 million.

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.

The competition is only selling at $150-$170M today because SpaceX pushed them into it. 10 years ago, F9-class payloads would've cost $400-500M (on Western launchers; Russia and China were always cheaper). Those prices had been pretty stable for decades; the key thing which has changed since then is the presence of a real competitor.

So 80%-90% has already happened.

Would you explain your extreme position instead of making snide comments? We're all here to learn. Educate us.

Let's begin by seeing that SpaceX increased it's launch cost by 50% for 2020 to $228 million while Orbital ATK is launching for $223 million, meanwhile actually being a profitable company. [1]

SpaceX blames this on NASA. So Orbital ATK didn't have that problem because, reasons?[1]

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.


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