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Arecibo Observatory Collapsed

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Re: Arecibo Observatory Collapsed

#241

Post by dheera »

kaikai wrote: post #238
dheera wrote: post #229

Earlier quoted context omitted.

> no way of replacing How did they build the cables in the first place? Couldn't they just snip the cables with a helicopter or unmanned drone with a flying chopsaw and string new ones as if it was a brand new construction? Basically I'm not understanding how it is impossible to replace something but it is evidently possible to build that something.

Being unable to fix something you’re able to build isn’t unusual to anyone who has built a large and complicated structure. They had two different engineering firms look at it, and neither of them saw a safe path forward. It’s possible that repairing it was physically possible, but would have put people in harms way while they were, for example, detaching cables on an already unstable structure.

Are there not unmanned solutions to the problem? Drones with flying abrasive chopsaws? Literally strap a Dewalt circular saw onto a big enough drone with the power button taped down? Use a drone to attach a dynamite to the cable? It seems weird to me that the government can figure out how to remotely bomb a town but can't figure out how to remotely do a little snippy snip snip on a cable.

Re: Arecibo Observatory Collapsed

#242

Post by AnimalMuppet »

hedora wrote: post #202
nickff wrote: post #152

Earlier quoted context omitted.

A lot more money is spent on education than on the military in the USA (where education is funded by three levels of government), and most other countries.

US education spending is about 20-30% more than military spending, but the money is not well-allocated. Most funding is from local taxes, which vary greatly from school to school, and sometimes from year to year. https://www.usgovernmentspending.com/year_spending_2021USbn_...

In fairness, the military spending probably is also not well-allocated...

Re: Arecibo Observatory Collapsed

#243

Post by ethbr0 »

javajosh wrote: post #72
ethbr0 wrote: post #65

Earlier quoted context omitted.

> small, passive object in freefall That's probably anomalously hot as it plows back through the atmosphere. I think radar stealth coatings are sufficiently advanced that they swung the balance back in favor of IR for tracking purposes. Historically: it was hard / unknown how to make a flying object that resisted reflecting radar Current: it's hard / unknown how to make a flying object that's resistant to radiating h…

>as it plows back through the atmosphere. I would assume that if you're tracking it on re-entry that's a little too late.

Depends on what you want to do.

Launch - early warning, max time, low certainty of trajectory

Boost - trajectory and impact refinement

Re-entry - terminal maneuvering, impact prediction, terminal interceptor cueing

I'd imagine you'd have ground-based sensors for terminal interception refinement, but having a wide angle view to cover highly maneuverable glide vehicles would be useful too.

Re: Arecibo Observatory Collapsed

#244

Post by alentist »

mumblemumble wrote: post #97
skuhn wrote: post #59

Earlier quoted context omitted.

I agree that the impact of Arecibo and these kinds of installations is actually very outsized relative to the number of FTE employees who directly work on it. The larger scientific community are the ones who booked time on the telescope after all. My point is that politically none of that matters. No one is getting elected because people got to book telescope time for their research. The incentives are not correctly…

> So the F-35 makes jobs... I wonder about that. It's been a while since I studied, but the phrase "deadweight loss" looms large in what I remember of the one economics class I took in college. So I wouldn't be surprised if the program is actually a net negative for job creation. Only that doesn't matter, either, because the point is not to create more jobs; the point is to influence job creation in a way that benefi…

It’s a game-theoretic problem that has a name:

Concentrated benefits and diffused costs.

Re: Arecibo Observatory Collapsed

#245

Post by kzrdude »

dheera wrote: post #229
petschge wrote: post #220

Earlier quoted context omitted.

The cables were (originally) redundant. There are actually replacement cables on the way from Germany right now. But after the one main cable failed earlier this year they noticed that all cables are MUCH weaker than previously thought. So there was (even before the collapse) no way of replacing the existing cables with the replacements. And yes that probably implies that they should have swapped out all cables years…

> no way of replacing How did they build the cables in the first place? Couldn't they just snip the cables with a helicopter or unmanned drone with a flying chopsaw and string new ones as if it was a brand new construction? Basically I'm not understanding how it is impossible to replace something but it is evidently possible to build that something.

The thing that was hanging suspended above the dish was weighing 900 tons. I don't know how it could be that heavy (it's probably pretty big), but that sounds too heavy for any helicopter or drone to lift - even if it only had to hold 1/100th of the weight of it while the cable was being replaced.

Re: Arecibo Observatory Collapsed

#246

Post by briancp »

A shame. Beyond the loss to science, the equipment itself was impressive. A 900-ton observation platform is like a multistory building suspended a few hundred feet in the air, in the middle of the jungle.

An interesting gallery of the telescope being constructed is here: https://www.naic.edu/history_gal/historicgal.html

Re: Arecibo Observatory Collapsed

#247

Post by bigbubba »

dheera wrote: post #241
kaikai wrote: post #238

Earlier quoted context omitted.

Being unable to fix something you’re able to build isn’t unusual to anyone who has built a large and complicated structure. They had two different engineering firms look at it, and neither of them saw a safe path forward. It’s possible that repairing it was physically possible, but would have put people in harms way while they were, for example, detaching cables on an already unstable structure.

Are there not unmanned solutions to the problem? Drones with flying abrasive chopsaws? Literally strap a Dewalt circular saw onto a big enough drone with the power button taped down? Use a drone to attach a dynamite to the cable? It seems weird to me that the government can figure out how to remotely bomb a town but can't figure out how to remotely do a little snippy snip snip on a cable.

Flying buzzsaws seems unlikely to work, but I don't think snipping the old cables would even be the hard[est] part. Installing new cables would almost certainly require workers to be present on the center platform, and it obviously wasn't safe for anybody to be there.

Re: Arecibo Observatory Collapsed

#248

Post by nullc »

superkuh wrote: post #129
ISL wrote: post #40

Earlier quoted context omitted.

The FTE employee-count alone underestimates the impact of national-scale science infrastructure. naic.edu is down right now (I suspect they're busy at the moment), but their data is used by tens to hundreds of institutions, each partially employing faculty, postdocs, and students. For agencies like NSF, the science is sometimes almost secondary. What matters perhaps the most is that qualified and capable students con…

> China's larger modern copy of Arecibo (FAST) come on-line in 2016 China's is not really a copy. It does not have transmit capability. What is really missing now in US, and international science is asteroid radar imaging and ranging.

I think fast is also limited to a much lower frequency than Arecibo due to trading off pointability vs surface consistency-- which it needs in part because its so much further from the equator.

Re: Arecibo Observatory Collapsed

#249

Post by xyzzy123 »

mumblemumble wrote: post #97
skuhn wrote: post #59

Earlier quoted context omitted.

I agree that the impact of Arecibo and these kinds of installations is actually very outsized relative to the number of FTE employees who directly work on it. The larger scientific community are the ones who booked time on the telescope after all. My point is that politically none of that matters. No one is getting elected because people got to book telescope time for their research. The incentives are not correctly…

> So the F-35 makes jobs... I wonder about that. It's been a while since I studied, but the phrase "deadweight loss" looms large in what I remember of the one economics class I took in college. So I wouldn't be surprised if the program is actually a net negative for job creation. Only that doesn't matter, either, because the point is not to create more jobs; the point is to influence job creation in a way that benefi…

It's also to maintain the capability. You need to keep people continuously employed in that area or else you run a high risk of losing the ability to field new aircraft.

It is not so different from subsidising farming (similar pros and cons) to ensure food security.

There is a lot going on in the supply chain that you need to maintain at a baseline level if you ever expect to have to fight.

From a very macro level whatever airframes get shipped may matter less than maintaining all the specialised knowledge and suppliers that you need to produce them. "Looking after the machine that makes the machine".

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