This is not the only hurdle. You can have an airport right next to a major city, with hundreds of arrivals and departures each day.
The same cannot be said for a Starship spaceport. Due to very loud launch, sonic booms on landing [0], and the danger of dropping a Starship onto populated areas, it would likely need to be offshore. That requires a boat, so now boarding a Starship involves thinking about sea states, taking a ferry ride on each side, and more.
Starship is super cool, but point to point Starship is a bit of a fantasy when you start to get to the nitty gritty.
110dB 20km from the origin? That is a serious WTF right there if that number is accurate. If my quick estimate is correct that would mean that the sonic boom is deadly to anything within a few 100m around the booster. Even 110dB is skirting the border to permanent hearing damage from a single exposure.
It could be possible for a couple routes where launch and final approaches could be done over water. It'd need some shallow seas, so platforms could be anchored to the bottom, as well as some high-speed rail and some veeeeery long rail bridges connecting the spaceport to land.
A quick look at ocean depth maps points to friendly continental platforms around the East US, China, a lot of Australia and New Zealand, and most of South America.
It'd be a massive effort, but not completely impossible. To get to Brazil to see my family, I'd probably need to first go to Southwest Ireland before boarding a suborbital flight to Rio, so it'd be 2 hours of rail, then 20 or so minutes of suborbital, then another hour flying to São Paulo (which is not on the coast). Still beats flying through Lisbon, Amsterdam or Paris.
Hear, hear. Rapid dragon air-launched Superheavy with two-way radial symmetry switchblade wings for engine-forward horizontal landing. Make it a big-ass glider biplane with big Dragon in its tail for cargos. No sketchy flops or balancing act, Cg forward of CoL all the way from retro burn to touchdown. Capsule escape available down to 500 feet or there abouts.
And that suborbital spaceflight is effectively off the table for anyone with a heart condition. There's a reason why you see all those warnings on rollercoasters even when the dangerous part lasts <1s. Now let's subject someone to minutes of it.
That's akin to saying that it seems fundamentally impossible to make landing rockets safe which, in fact, is exactly what Boeing/Lockheed were saying when SpaceX was first revolutionizing that space as well.
I’m not aware of any rocket landing safe enough for human use. NASA nixed the idea of propulsive landing for Dragon 2 for this reason. It’s extremely difficult to make safe, since just about any reasonable engine configuration means guaranteed death if a single engine fails at a critical moment. Compare with modern airliners where an engine can fail at any point in flight and the plane can land safely.
You're right; I meant to refute the following point:
NASA nixed the idea of propulsive landing for Dragon 2 for this reason (safety)
It wasn't because of safety, but because it would have needed tests, development and certification (for a new type of landing) while already having an established method (splashing into the sea).
> NASA nixed the idea of propulsive landing for Dragon 2 for this reason.
That is completely false. First of all, NASA didn't nix it, they just didn't make it a priority as it had little value from their perspective.
The reason it was not done is that para-shouts have to be in the design anyway for abort situations, so that was fixed.
So for SpaceX, the question was to likely delay the program, and take on a whole lot of extra engineering work that they were not actually getting paid for, remember fixed price contract.
They were only going to work on it if they really thought they needed it for something like Red Dragon. And then they could still add it later.
And one of the primary reason SpaceX thought that its to hard, is that they landing feet would have to have gone threw the heat shield. That would have made the whole heat-shield design massively more complex.
He said it was the difficulty in proving the safety. There's an informative article here. [1]
NASA likes parachutes because they've always used parachutes. SpaceX likes retropulsive landings because Mars is their goal, and Mars' atmosphere isn't dense enough for parachutes. It's also safer for the crew in nominal operation and enables a much higher degree of rapid reuse, relative to NASA's traditional operation of taking a salt water bath in the ocean.
So they could go through the [very reasonable] extensive costs and testing involved in proving the safety of the retropulsive landings, or just go old school, strap a few parachutes on and work on getting crew to the ISS (which was the goal at the time). They chose the latter and with the plan of getting back to retropulsive landings later, which they also did. Parachutes remain the main landing mechanism for the Crew Dragon, but it now also has retropulsive landing capabilities to be used in case of a chute failure.
They had repeated successful demos of it, but NASA kept adding on new requirements while implicitly signaling that they had no interest in approving the system, which would have made Boeing's lander look obsolete before it was ever finished. NASA's judgements are heavily influenced by external factors that make it quite difficult on outsiders, while enabling reckless behaviors for insiders.
For example NASA deemed the Boeing crew vessel safe after its pad abort test resulted in only 2 of 3 parachutes deploying and it suffering a propellant leak - all in beyond optimal conditions. They deemed it not only safe, but safe enough to completely skip the scheduled in-flight abort test. All of this is of course how you ended up with astronauts trapped on the ISS that had to be rescued by SpaceX.
For another contrast there after SpaceX did swap over to a simple parachute system, their pad-abort test went off flawlessly. NASA still required they do an in-flight abort. Granted, that's nothing to complain about, because that's exactly what NASA should do. But they also should have had Boeing completely redo their pad-abort test and damned sure do an in-flight abort as well. Safety culture at NASA is generally completely dysfunctional because of non-safety factors.
This is nothing new either. Both Space Shuttle disasters were 100% preventable, and not only in hindsight. Engineers brought up the exact causes of both explosions well before they happened, but the bureaucratic layer ignored them.
I'm not entirely understanding your point. Are you saying they were able to demonstrate a better than 1-in-N probability of fatal mishap for the appropriate N (I believe about 300 for this case) and NASA just wouldn't accept it? Or they weren't, but ???
Shuttle is an excellent example of the sort of thing I'm talking about. It had no abort capability in the event that something went kaboom, and no realistic abort capability at all for large critical portions of launch. Their test pilot outright refused to test an abort because he didn't think it would be survivable. It never should have been human-rated, and it only was because NASA pretended it had an abort capability that wasn't really there.
Starship is even worse: not only does it have no realistic abort capability for most of the launch, it also has a very delicate landing procedure that requires a substantial amount of propellant to remain on board, no ability for the occupants to escape in the event that those propellants decide to mix in a place where they're not supposed to, and very limited ability to handle engine failures.
There is no exact and objective set of hoops one can jump through to prove a sufficiently complex (let alone novel) technology safe within a certain bounds, short of doing exactly what it will be doing over a large sample, which is often not economically feasible. In fact one of the first things that happened early on in the Apollo program is that mathematical risk modeling was completely scrapped. The results were always so pessimistic that NASA found it impossible to move forward with it!
So this leads to judgement calls from NASA that are opaque and, in practice, are not necessarily grounded in safety, as per your own example as well. NASA clearly did not want SpaceX doing propulsive landings and was making sure to dot all their i's and cross their t's with them, while simultaneously going YOLO with Boeing and actively greenlighting their vessel which clearly was not even remotely safe for a human. In this context, it's highly unlikely SpaceX could have convinced NASA to more forward with the propulsive landings, even if they were the safest thing ever invented.
I don't understand much about aerospace engineering, but adding time, complexity, and expense sure sounds a lot like "extremely difficult to make safe" to me.
I guess people just want to argue. I have three different people replying to me effectively saying, "you're wrong, it's not because it's difficult to make it safe, it's because it was difficult to make it safe because of reasons X Y and Z."
I explained what the issue was in technical terms, as I was following these issues in real time as it was developed and what communication from NASA and SpaceX was at the time. Then you made a smart-ass comment about how I was wrong and it was actually about safety. That wasn't incorrect if you want a one word answer but it also doesn't explain the 'why', and that's what I did.
