Bimfred

Because if you launch something from Earth, you inherit the Earth's orbital speed around the Sun. At that point, whatever you launched will just continue to orbit the Sun. It takes less energy to accelerate to a solar system exit trajectory than it does to scrub off all of the excess velocity and end up on a trajectory that intersects the Sun.

Even the Stream version doesn't require Steam. You can just run the executable. A few folks over on Reddit claim they've given the game to their friends just by copying the files from an external drive.

Most of the Falcon 9 launches are for Starlink and are paid for by SpaceX themselves. How is that "the government subsidizing them"? If you want to argue that they're using money they got from NASA to fund those launches, is your plumber feeding their family from you subsidizing their life?

There's two main benefits: faster reuse and more payload to orbit.

A Falcon 9 landing on a drone ship needs to be transported back to shore. That's multiple days before the engineers even get their hands on it to prepare for the next flight. The design goal of Starship is to launch a Ship into orbit, return to the tower, be restacked, refuelled and launched again in the same day. Will they actually get it to the point where that's possible? Remains to be seen. Until now, they had no way to see what real stresses a Starship booster goes through in a flight. They're gonna rip this one apart down to the spacers in its bolts to examine it. With the flight and physical inspection data, they'll make what improvements they can to the already built boosters and design future boosters to be more resilient. SpaceX has, by now, a well proven track record of doing what others think is insane to even attempt. If anyone can launch the same rocket twice in a day, there's no one better to give it a try.

The increased payload comes from not having the mass of the landing legs. The Falcon's landing legs weigh several tons. Starship, being 3x the diameter and 10x the mass, would need titanic landing legs. That's a lot of tonnage you won't be taking to orbit. Catching on the tower means that all but a fraction of the landing hardware's mass isn't on the rocket itself. As an additional benefit, the landing hardware needs to be built only once. Every Falcon has its own landing legs, but every Starship they ever build could land on the one tower they have now. That won't be the case, they're planning to build multiple towers, but the sentiment remains the same.

Well, off the top of my head, the main issues are going to be the sleds, the rails and how much they allow to reduce the mass of the plane itself.

Accelerating the sled with something other than the vehicle's main engines makes the most sense. Otherwise you've just overcomplicated a runway and end up back in the pit of spaceplane-style SSTOs. So assuming they're gonna boost the sled, how? I don't think liquid engines have the yeet to get up to a worthwhile speed on the rather short rail. Solid boosters? They have yeet, but once you've lit them, you can't really turn them off and that leaves you with woefully few abort options between ignition and launch. Electromagnetic? Getting enough yeet is a matter of enough (and big enough) capacitors, but the rail erosion is going to be worse from the sheer waste heat. And any attempt at recovery of the sleds will require the rails to be extended to decelerate them. Cause you'll want to get the vehicle going as fast as possible, within the limits of what the structure and payload (alive or inert) can handle. But once you've done that, you're not gonna hard stop the sled and reasonably expect to recover anything but twisted metal and composites.

The other question is how much is it gonna help in reducing the vehicle's mass? The friction from doing even Mach 1 near sea level means the vehicle has to be reinforced to handle it, maybe even require active cooling of the hull. So that's going to cut into whatever extra payload mass they'd get from the launch speed. And the vehicle's engines will still need to work damn hard to climb up the well, in which case low Mach numbers aren't going to do much and might actually be counterproductive thanks to the high drag.

My most insane, pie in the sky, they'll-never-try-this idea? The rail is angled up a mountainside at about a 45 degree angle. Electromagnetically accelerated, it's basically a huge Gauss cannon and the sled yeets off with a 4g acceleration. By the time it reaches the end, it's going at about Mach 1.5, at an altitude of 2-3km, at which point the vehicle lights its engines and disconnects from the sled (Spinlaunch has shown that fraction of a second precise release is possible). The plane continues to ascend, the sled just fucking runs off the rail and coasts to peak altitude, then deploys parachutes to descend back to the ground. But this is an entirely unreasonable idea. Construction and maintenance would be ludicrously complicated and harried by environmental concerns. The energy required would probably be comparable to that of a small town. There's way too much risk of the sled colliding with the plane at the end of the rail, not to mention the parachute descent. On the other hand, goddamn, it would be awesome!

The skepticism is reasonable. The theoretical principles are sound and there's a lot of math (done by actual scientists and engineers, as well as sci-fi writers) to show that, in some form, it would work. But this is a huge undertaking that's never really been tried before, so no one really knows how difficult (and expensive) building and operating it is going to be. Honestly, I expect this to fall apart before they begin high altitude suborbital tests of the rail launch system. On the other hand, it's such wonderful sci-fi shit that I can't help but root for them. If they can secure the funding to continue developing this, it's gonna be fascinating!

The rail launch is going to be interesting. Presumably, the sled is separately accelerated, to give the vehicle a little kick and save propellant. It won't be much, even a 4g acceleration would only get it up to roughly Mach 1.5 before it runs out of rail, but it's not nothing either. And unless the sleds are single-use, they'll need to decelerate them somehow.

But man, bring it on! The premise of initially accelerating a vehicle on a rail or launch loop, before the vehicle's own engines kick in, is probably the closest we can get to SSTO from Earth. At least without using nuclear propulsion.

Right now, the Earth is losing mass at about 55 000 tons per year. Yes, losing. About 100 000 tons of hydrogen and helium escapes the upper atmosphere, partially offset by roughly 45 000 tons of dust and meteorites getting scooped up along our orbit.

Considering this has been happening for millions of years, I think we're quite safe from affecting the Earth's mass and orbit within the span of even centuries.

But it's much more likely that the majority of material mined and processed in space will not be coming down to Earth. It's much better put to use in orbital construction, or shallower gravity wells like the Moon and Mars.

You're entirely right that getting to the rocks, and getting the mined stuff to where it's actually useful, are gonna be a problem. Maybe we'll finally get some nuclear thermal engines, cause the shite ISP of chemical rockets is really insufficient for these trips and ain't no one wanna wait on the gravity assists.

Fingers crossed this woman doesn't end up with a Zydrate addiction. It comes in a little glass vial, you know.

NASA has the measurements of all their astronauts and Dragon flight suits for Butch and Suni are already made.

Crew Dragon has been solely responsible for the US side of ISS rotations for four years, without incident. 8 successful missions, not counting the privately funded trips. Cargo Dragon has been doing resupply missions since 2012.