Just to confirm: are you using Firefox? I think it was generating a circular history, but an unrelated change I just made seems to have fixed it. Strange! I am merely using location.hash.
This is fascinating to someone working in the open source Web application space. Large (but decreasing, thankfully) pockets of our culture still need convincing about test coverage; clients still can't be sold on its value.
Clients can be sold on bug free features though. Good test coverage is a good way to get those. Past a certain point more tests will probably cost more than fewer bugs will pay, so there is a natural trade-off.
This is very true. To build on it Different domains need to understand that trade off is in different places. A self driving car needs and financial software need to be low on bugs, but will rarely kill hundreds like a bad software in power plant or nuclear missile might.
I feel like space is becoming less of a "let's cross our fingers and hope it works on the first try" culture. See space shuttle landing for a typical example.
I'm not sure I understand what you are saying here? Are you intimating that they are being over cautious?
In any case, I don't thing a supply ship docking rendezvous is comparable to a shuttle landing. As mentioned in the article, the rendezvous can be deferred and reset to another future time fairly easily, and with little consequence.
A shuttle landing however, HAS to work first go - there is no go-around and try again, whatsoever. Hence why the shuttle pilots trained extremely rigorously. Even when they used the specially modified Gulfstream [0] (which was flown with flaps extended, gear down and thrust reversers deployed to emulate the shuttle flight characteristics!!) to shoot practice approaches, the pilots were judged on their very first attempt - all follow up approaches was merely working out the kinks.
I don't think the Shuttle landing was particularly problematic. They had a lot of control over the glideslope and lots and lots of runway to work with. I'm sure it's a lot more challenging than the sailplanes I fly, but I wouldn't have any major safety concerns flying on the Shuttle during landing.
It's true that SpaceX's booster landings are fairly unreliable, but they don't have to be reliable. They make a bit of a mess when they go kerplooie, but it's no big deal. Lives aren't at risk, and the equipment is cheap enough to lose.
The launch was a much better example of brittleness in the Shuttle system. The solid rocket boosters couldn't be shut off or ejected once they lit, so that was about two minutes where there were no options if anything went wrong. Even after booster separation, the abort modes were so difficult that NASA refused to ever test them. The first Shuttle commander said that a return to launch site abort would require "six miracles followed by an act of God" to pull off.
Every other manned spacecraft has the capability of aborting a launch at least semi-reliably, and proves it with testing.
> I don't think the Shuttle landing was particularly problematic. They had a lot of control over the glideslope and lots and lots of runway to work with. I'm sure it's a lot more challenging than the sailplanes I fly, but I wouldn't have any major safety concerns flying on the Shuttle during landing.
Well the shuttle is a big heavy glider with little wings. One try, and down from 30,000 feet to ground in 3 minutes. Not problematic, but very special.
I wouldn't say that the booster landings are fairly unreliable. Technically they are still in the experimental stage. They're also 8 for 14 at this point, with the last landing failure being at least 4 launches ago I believe.
Plus it is a big deal when they go kerplooie. On each coast, they only have 1 ASDS for landings, and if a core explodes on one of those then it's out for like a month of repairs. Failures on land are probably easier to deal with, but we haven't even seen one of those yet.
Plus within the next year they are basically going to stop producing new cores, so loosing one won't be "cheap"
Losing 6 out of 14 is more than enough for me to call it "fairly unreliable." Imagine if NASA had destroyed six Space Shuttles during development.
The genius of SpaceX's approach is that they built a landing system where it's OK to be unreliable for a while. Instead of being a billion-dollar item like the Space Shuttles were, the Falcon 9 boosters are a few tens of millions of dollars apiece, and the launches are priced to cover the entire cost of them plus more.
ASDS repair depends on the nature of the failure. When a low-margin GTO mission miscalculates and craters, that does indeed take some fixing. A JASON-style tip over and kaboom seems to basically involve picking up the pieces and repainting the lines.
I think your last sentence reverses cause and effect. If they substantially cut down on core construction, that will be because the landings became reliable enough for that to happen. That doesn't make failures costly now.
I will also note that their landing approach is inherently unreliable to a degree, because there's little redundancy. If Falcon 9 loses an engine on the way up, it's fine. If it loses an engine during the landing burn, it's going to kerplode. If it loses an engine on the way up, then that will likely wreck the fuel margin needed for landing. I'd be shocked if Falcon 9 can ever achieve anything like the Shuttle's perfect 133 out of 133 landing record. (I'm not counting Columbia since it was ultimately a launch accident that manifested on reentry, and never got anywhere near the actual landing.) But that's fine, they don't need to.
>The genius of SpaceX's approach is that they built a landing system where it's OK to be unreliable for a while.
For booster landings it's probably okay to be unreliable forever as long as the failure rate is estimated properly and the value of recovered boosters exceeds the cost of developing and maintaining recovery capability. Since there are no people or cargo involved it's a straight exercise in accounting.
The landing burn is generally a single engine. The only time they have done three engine landing burns is for very tight margin GTO launches (and even then, it's not three engines all the way to the ground, the two outboard engines shut down about halfway through the landing burn).
In cases where they are using three engines during the landing burn, losing one would be catastrophic. You'd lose a third of the thrust you were counting on, and the remaining thrust would be highly asymmetric. The other outboard engine can't gimbal far enough to keep the thrust vector through the center of mass of the rocket.
The booster landings are all lumped together, but they all have very different parameters. They've never failed a landing on land. and since they succeeded at sea, they've only failed once since then, and that was coming in from GTO, which is borderline not possible by their own admission, they only tried just to get more data points.
The upcoming Echostar 23 mission is flying in expendable mode (no landing attempt) because the mission parameters simply don't allow for a landing. They could try and fail, but they don't really need more data points - especially when people don't realize that these experimental landings are just experimental, and it winds up with bad press.
spacex does walk a fine line between "rapid development causing potential issues" (see AMOS-6) and "abundance of caution" (see CRS-10 delay on saturday)
>Hence why the shuttle pilots trained extremely rigorously.
But even this was kind of a manufactured necessity. Landing was deliberately not done with computer control. Buran was able to autoland back in the 80s and everything else on the Shuttle can be done all under computer control but lowering the landing gear, deploying the drag chute, and landing were all intentionally "off limits" for computer control.
Tens of millions, hundreds of millions, or billions of dollars, maybe, but I can tell you from experience that single digit millions of dollars runs with "fingers crossed" all the time in underwater robotics. Either your threshold for human indiscretion is just set in the wrong place or there's something else going on.
The avionics were multiply redundant, yes. But the Shuttle landed as an unpowered glider. If the first landing approach failed, there was no possibility of another.
Millions of dollars and human lives. I think things like the fact that Nixon had an Apollo failure speech ready is the exact opposite of "cross your fingers" and more proof that they tried to think through everything they could, including unpredictable failure.
I agree. Eisenhower had a similar speech ready had the D-Day invasion failed. It's just part of leading any large project that could fail spectacularly.
I remember their first docking attempt and the excitement of that. What impressed me the most was the fact they had to change the code so the laser spotters focused properly on the right targets (glare? I forget)
cargo runs should never make the news, once things become routine people will trust it more. from that base you build out
Just as an enthusiast I'm finding what they do rather routine now. The first stage's automated landings were REALLY exciting while they were trying to figure it out, EXTRA exciting when they stuck one, then less and less exciting to me. Still make for gorgeous visuals and are no less impressive objectively, but I'm beginning to understand why people had grown board with lunar landings by Apollo 13.
Completely agree. It's also reassuring that they have software capable of detecting deviations like this because who knows if the astronauts would've caught it. They're already busy with a million other things.
