sevenperforce

A solar-powered ion thruster is analogous....

The reason you don't see stars during the day is because the Rayleigh scattering is brighter than the starlight behind it. Not quite. It's a function of particle size. Particles within the rings are mostly between 1 cm and 10 m with an exponential size-frequency relationship. The odds of a given photon intersecting a solid particle while traveling through a given path can be calculated if you estimate the size-frequency relationship, but it's not at all "X% of the path is blocked". Also, the ring particles are almost exclusively pure water ice...purer than found in most places in the solar system, actually. Though they are not transparent, so you're correct there. The rings are visible because they scatter sunlight, and so there is enough sunlight being scattered toward you to saturate. But you can definitely see through them. Consider this high-contrast Cassini image: From this vantage point, you can see how much light is blocked by the rings, both in their shadow projected on Saturn, and by the visibility of Saturn's disc through them at the top. The B ring obviously blocks more light than the C or A rings, but even it allows a little light through (the apparently-black portions of the stripes across Saturn are actually lighter than the black background.

Air is dense enough to see when illuminated by sunlight but not so dense that it blocks starlight. Only 3% of the volume occupied by the rings is actually solid material. Starlight can shine through them easily, but stars are washed out by the ring brightness. Photos which show Saturn's rings typically do not show any stars because the dynamic range isn't high enough.

Arguably, you would still see stars shining through. The rings aren't dense enough to actually attenuate starlight.

It's easy to forget just how freaking unprecedented this is.

Yes, they can, and easily. But that is, I believe, a variant of the Long March 2C with the addition of lower fins, a solid interstage, and grid fins. The Long March 2C is powered by four YF-20s in the YF-21C configuration, which has no centrally-mounted engine and cannot downthrottle low enough for even a hoverslam. I am unsure whether the YF-21C config has relight capability. The engine schematics don't show burst discs or anything but that isn't always reliable. The YF-20 also has a very rough fuel-lean start, as shown by the big clouds of N2O4 that puff up around the base of the rocket at ignition, so trying to control the landing in a preferred zone seems hazardous...then again, so is just dumping the whole rocket onto inhabited areas. I would also guess they are testing for another project.

Late to this party, but given that this is clearly a hypergol booster, I don't foresee reignition and landing on it....

Definitely looks like a full-size flaperon. I really wonder what kind of hydraulics they're going to be using.

In theory, you could have an NTR which produces an ionized exhaust stream with an open-cycle coolant loop acting as the charge sink. The coolant loop would generate power, which could be used for an electromagnetic nozzle to accelerate the exhaust stream faster. The big problem with an NTR is temperature: you can only make the propellant move faster by making it hotter, and at some point you melt the reactor. A pure hydrolox rocket burned at stoichiometric ratio produces heat not significantly lower than the temperature of a solid-core NTR; the advantage with an NTR is that you're only pushing hydrogen, not that nasty and heavy oxygen, and so your specific impulse goes up. By accelerating the NTR exhaust products after they leave the chamber, you don't have to worry about overheating the reactor. If you could make it work.

Odds of LOCV for STS-1 was determined retroactively to have been what...1:12? 1:9?

LOCV failure modes for a commercial airliner include loss of control surface authority and catastrophic structural breaches. If the elevators fail, the pilot can't control pitch and the plane crashes. If the wings break up, the plane crashes. SS has the same failure modes; if it has a tank breach or a loss of control fin authority, it crashes.

You can't have a chemical reaction that produces charged exhaust with only two reactants, because you need a charge sink. You can't just delete charge; it has to go somewhere. Any system that produces charged exhaust would accumulate electrostatic charge on itself. What you could do, conceivably, is have a multichamber tripropellant engine that produces two exhaust streams, one positively-charged and one negatively-charged. Maybe do it with an annular thrust chamber, like an aerospike engine inside a de laval. Then your net charge flux is zero and you can use magnetic fields to further accelerate one of the two charged exhaust streams..

why? For an exhaust flow to be ionized in a way that would allow it to be manipulated my magnetic fields, you'd need to rip the electrons away in an organized fashion. You can't just annihilate the electrons, either. You'd almost need to have a tripropellant reaction, with one exhaust flow being net-positive and the other being net-negative. What I really want to see is a Hall Effect thruster (or other electrostatic thruster) which can have a working fluid injected into it to amp up the thrust at the expense of isp.

Getting a reaction with a workably ionized exhaust stream is...tricky.

At some point you create a kugelblitz, at which point, why not just go with a black hole starship? Collimation of the thrust beam is always going to be the challenge.