Hacker News Reader

Comment by InTheArena | Hacker News Reader

It's been interesting to see SpaceX shift from hardware-rich to a more traditional process the last year. I suspect a lot of it is due to the sheer cost of what they are doing, but a lot of it is PR management as well... Plus it's obvious that the US government is doing everything in their power to have Musk on as short of a leash as possible.

View on HN

SpaceX moved beyond what they could test without the launch (and catch) tower. They've spent a lot of time and money developing the ground systems - in comparison the early crude Starship prototypes were comparatively cheap and easily replaced - and I would imagine they really would prefer not to accidentally demolish the tower again.

If I recall correctly after this Methan explosion 9 month ago they got more cautious and slower:

https://www.youtube.com/watch?v=PjbjXTomxqI

And they also have previous painful experience of destroying a Falcon 9 pad. https://www.youtube.com/watch?v=_BgJEXQkjNQ Really can't afford to repeat that if they are to make the timeline for using Starship as NASA's next lunar lander.

How much does Mechazilla cost? I read it's 1 billion. Also news is Elon said destroying nearby infrastructure would be a 9 month setback at the least.

Wow that’s like 2.5% of a Twitter.

Almost sounds like a bit chicken/egg, you can't try landing without a certain amount of confidence, you can't build confidence without trying.

Considering the hover capability of the booster (can be throttled to <1G) we might see an unprecedented amount of touch and go testing before the first real attempt?

From the booster's point of view, the catch is a target location and speed. Plus a set of tolerances: however much the arm can swing to catch it, and horizontal speed has to be really low because it needs to drop down vertically into the arms. I would expect that the target on the ocean, even for the first test, is very specific. Once the booster can hit a phantom target, they can change the target to the tower and go for a catch attempt.

I imagine that lack of stable reference points would be an issue on the ocean. Both for the algorithms under test and for validation. (I liberally use "algorithm" here as the superset of both algorithm and the hardware it runs on, I think in reality these tests are mostly for correcting parameters that are hard to determine with sufficient accuracy on paper)

If you want to write off an entire booster, adding a dummy tower somewhere in the desert would not add much to the bill and could well be worth it. Or maybe even a not-quite-so-dummy tower, but off-site, where the booster would be scrapped on location (instead of reflown) even in the best case, no matter how hypothetical?

Good GPS in ideal conditions (no trees or buildings blocking/bouncing signal) has accuracy on the centimeter scale: https://www.gps.gov/systems/gps/performance/accuracy/

But in a real landing, they wouldn't want to be accurate relative to some GPS goalpost, they need to be accurate to whatever physical reality turns out to be. Reconciling expectations about were the landing location was supposed to be and where sensor input says it is must be of major importance.

That link tells us that the signals are intended to be sent with an accuracy better than 200 cm 95% of the time. Using more frequencies only really helps avoiding errors from bad/misleading reception, so it's hardly relevant in "ideal situations".

Long term stationary receivers can resolve to millimeters, but dropping rockets from orbit isn't exactly a thing that would be considered "stationary" in this context.

The slowdown of testing is not a change in their methodology. It was because they succeeded in all suborbital testing. The orbital testing has been held up by bureaucracy, heat tile iterations, and launch tower refinement.

The costs of test articles are pennies on the dollar compared to the launch value of these vehicles once operational.

By now they have 2.5 stacks ready, and surely have enough raptor engines saved up to rapidly launch 5+ starships this year, assuming they have the heat tile stuff figured out to a degree that the tests would be meaningful.

Also, I think the starship crashes and their frequency were really freaking out the authorities and potential customers. I remember Elon saying “we need to stop making craters”.

That’s a very charitable interpretation. Testing slowed because of flaws in the Raptor which required a complete redesign. We’ll see if their chaotic development process produces something safe and reliable.

I hadn't heard that Raptor 2 was a complete redesign as a results of flaws discovered (I hadn't heard anything at all about why they made Raptor 2). Do you have a link where I can read more about this?

Not a complete redesign, but substantial. Even the head of the propulsion department was changed.

From what I observed (reading the normal Reddit fluff, listening to NSF banter, and Tim Dodd the EA's interview with Musk) the issue with Raptor was being able to produce it reliably and rapidly. In the EA interview with Elon you can see how much less plumbing and paraphernalia there is on V2. I think both versions "worked" (they have been running lots of full duration tests at McGregor) for quite a while. One of Elon's many insightful sayings is something like "The best designed part is no part"

It is still a hardware rich process from a Aerospace standpoint. They have three more built at the moment and another three in production. Musk said that they are Manufacturing engines at the rate of 1.8 per day which is absolutely insane

>Plus it's obvious that the US government is doing everything in their power to have Musk on as short of a leash as possible.

What are you referring to?

>Plus it's obvious that the US government is doing everything in their power to have Musk on as short of a leash as possible.

What do you mean by this?

Some people are confused and think the government is against Musk in some way like the public is. The government quite likes SpaceX.

And the parts that might be annoyed at him for Twitter are entirely unrelated to those dealing with space.

Sadly "The government" is hundreds of separate organizations, agendas and politicians all with separate cover their ass agendas, NASA probably want this to succeed, I doubt the others are as enthusiastic.

NASA, the military and security services

“Sadly”? Would the alternative of a monolith be preferable in a pluralistic society?

What reason would the other parts of the govt have to want Musk to fail?

The public isn't though. Most people outside of twitter don't have any opinion on him.

Reply on news.ycombinator.com