atharris · HackerTrans

This is really meat-dependent, ironically - the biggest thing we could do is cut consumption of steak and other prime cuts of beef, since ground beef is made out of what's left after those expensive, sought-after cuts are taken. I would guess that eliminating ground beef consumption doesn't really get us anywhere for the environment.

atharris

6년 전discuss

I've said this elsewhere in the thread, but stabilizing a dynamically unstable system is half of the reason why control theory remains an active research area instead of a mathematical backwater; this kind of set up is extremely common for aerospace systems. Software is hard to get right - which is why aerospace software has traditionally faced much higher bars for verification than 'traditional' software (and is much more expensive as a result!) The same is true of hardware, which I think many HN commentators forget; the cost of a bolt or connector that is aerospace-grade is typically many times that of a conventional or automotive-grade part, due mostly to extensive testing+verification required for safety.

Most of the scenarios you're describing are dealt with in a few ways:

1. Building systems with sufficient margin to account for this kind of uncertainty; even with passively stable aircraft, these margins exist. Feedback control typically increases these margins.

2. Extensive verification under a wide range of input conditions; this is more challenging (how can you enumerate every possible failure condition?), but usually boils down to some kind of Monte-Carlo sampling or worst-case analysis when those cases can be identified. Here's [0] a neat paper that does this in a more sample-efficient way.

[0] https://arxiv.org/abs/1709.06645

atharris

6년 전discuss

A caveat here is that the modern FAA is very different than the FAA of even 20 years ago. In response to decades of stagnant funding, 'the beast' is fundamentally unable to fill the same regulatory role it was intended to do - to all of our detriment [0].

[0] https://www.washingtonpost.com/investigations/how-the-faa-al...

atharris

6년 전discuss

I don't think the flight safety record of the MD-11 bears that out[0] - most crashes of significance were either cargo flights (which are much more prone to dynamical issues than passenger flights) or flights in conditions that exceeded design specs (landing in typhoons). It sounds like most airlines sold it because it missed range/fuel burn targets, not because of safety issues.

[0] https://en.wikipedia.org/wiki/McDonnell_Douglas_MD-11#Accide...

atharris

6년 전discuss

Ah - I didn't say Boeing's ability to write and test that control software was particularly good (in fact, I think their current track record says exactly the opposite.) I just hate when non-domain experts make judgements about things being 'fundamentally flawed.'

Insufficiently tested and documented? Sure. Bad UI/UX? Most definitely. Irredeemable 'because of aerodynamics' according to some private pilot that flew a 737 once in sim? Absolutely not.

atharris

6년 전discuss

Aerospace controls engineer here - while the airframe might not be passively stable (as is common for civilian aircraft), dynamically unstable aircraft have been stabilized with control software since the 70s [0]. If you've flown on an MD-11, you've flown on an 'aerodynamically flawed' aircraft. Most real systems are dynamically unstable without some kind of controller (implying software) in the loop.

[0] https://en.wikipedia.org/wiki/Relaxed_stability

atharris

6년 전discuss

Okay? This sounds like a great trade if your goal is to have a representative government instead of minority rule.

atharris

6년 전discuss

As a corollary - how many people already spread inaccurate or misleading video clips, sound bites, etc without this technology, and how many already refuse to believe real ones produced by the 'lying news media?' I think the hysteria is completely misplaced, and the extremely polarized media landscape is itself to blame.

atharris

6년 전discuss

I like this idea, and I think the research has backed it for decades - I wrote a letter to my Senator, Hillary Clinton, in support of later school starts back in middle school that cited such work. I think it hasn't happened for two reasons:

1. School is childcare for a lot of people; secondary schools let out early so older siblings can take care of younger ones.

2. As COVID has shown - it's difficult to manage multiple hybrid schedules and cohorts in an equitable way, especially if you're not expanding the number of teachers (which most districts can't due to budget constraints)

This is a little US-centric, but I suspect it applies broadly to the rest of the West at least.

Source: Parents worked in primary/secondary ed.

atharris

6년 전discuss

It's been stated elsewhere in this thread, but there really are a lot of practical, well-understood engineering issues with Elon's proposals that he refuses to admit or deal with. Here's a somewhat humorous review of his claims / what's wrong with them and how they stack up to actual civil engineering projects:

https://www.youtube.com/watch?v=4dn6ZVpJLxs

atharris

6년 전discuss

I agree with most of this, except for the unexpected rapid-response examples you list - I would expect an autonomous collision-avoidance system to react faster than a human being when faced with a deer in the road or someone running a light (otherwise - it's not a very good collision avoidance system!)

atharris

6년 전discuss

The rest of the world is rife with small, rural towns that nevertheless have great public transit systems, or at least ones that are more effective than what we see in the US. The major difference is that these places are willing to invest in the public sphere, and they're by and large willing to permit construction that is not car-centric (i.e., no parking minima to subsidize drivers).

atharris

6년 전discuss

To be clear, there are about ~15,000 objects (active + debris) in orbit ranging from small debris chunks to active spacecraft.

Starlink alone is expected to add ~30,000 active satellites with relatively large solar panels/bodies, which by virtue of their area alone can be expected to be more visible from the Earth than most of the small objects that are currently tracked.

atharris

6년 전discuss

This is definitely the largest drawback of Linux in general - support for peripherals and common communication/presentation software is really lacking. If I had a dollar for every time I had to muck around to get my headphones to work on Ubuntu, I wouldn't be posting here.

atharris

6년 전discuss

The core question is, 'what's the use of space anyways?' Orbits have two nice properties - they're high up, so you can see lots of stuff, and they're reasonably stationary with respect to the rotation of the earth, which lets you get global(ish) coverage without needing a huge number of accessors or high system replacement rates like aircraft or ground-based sensors need.

Communications and surveillance are the two largest opportunities, and a variety of companies have already sprung up (Starlink, Kuiper, Planet, Spire...) in addition to traditional players (OrbCom, Iridium, Maxar). There are some esoteric proposals for other uses, like manufacturing or bitcoin mining [0], but I don't think they provide nearly enough benefit compared to Earth-based competitors at this point.

[0]https://www.space.com/25626-bitcoins-satellites-deep-space-i...

atharris

6년 전discuss

This is very pessimistic - basically every space-faring nation now has pretty strict licensing requirements for new spacecraft, a portion of which is a plan to deorbit / move to a 'junkyard orbit.' In the US, this is actually handled by the FCC, because a satellite you can't talk to might as well be debris. [0]

In general, the economics of debris removal are also really unclear, because the actual risk of collisions is still pretty slim and the potential legal risk of touching another nation's spacecraft are high. Many objects are also too small to be tracked. The community is largely shifting towards debris avoidance, rather than mitigation - i.e., tracking and maintaining custody of debris, and maneuvering out of the way when necessary. This is pretty straightforward, since we already do a lot of space object tracking and maneuvering anyways. A variety of commercial companies have already moved into this space, including giants like AGI [1].

[0] https://docs.fcc.gov/public/attachments/DOC-354773A1.pdf [1] https://www.agi.com/missions/space-situational-awareness

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