Astronomy/cosmology questions...

[Buster's Uncle]

I wanna talk about orbital tether power and braking, too...

[Geo]

I wanna talk about orbital tether power and braking, too...

From what I read about it, its... flimsy...

[Buster's Uncle]

The only experiment I'm aware of, as discussed previously, melted/broke the tether in a hurry - but that's surely a straightforward engineering problem, probably solved with a simple thicker wire?

Of COURSE they used a flimsy wire - boosting mass costs.

[Metaliturtle]

The only experiment I'm aware of, as discussed previously, melted/broke the tether in a hurry - but that's surely a straightforward engineering problem, probably solved with a simple thicker wire?

Of COURSE they used a flimsy wire - boosting mass costs.

Is there a material that can withstand that amount of rotation? even if it's thick? That material science could make enough of?

[Buster's Uncle]

No rotation need apply - a tidal effect stretches the wire out into higher -and/or lower- orbit, the force pretty slight absent MILES and miles of wire, and passing a wire through a magnetic field -Earth's- generates current, it turns out, a LOT of juice, enough to melt a flimsy wire...

[Geo]

Of COURSE they used a flimsy wire - boosting mass costs.

I was reminded of that when talking to an engineer who works for (one of) the companies that constructed the PROBA3 probe.
Its a twin satellite setup where one probe creates an artificial eclipse of the sun for one flying in formation with it (to observe the corona). Both probes use a propulsion system to align themselves at the apogee part of their orbit.
One of my questions to this speaker was if during the design phase there had been talk about using tethers to keep those probes in permanent alignment, and he told me that wasn't on the table. A bit later I learned there's only 24-25 kg propellant in one probe, and a mere 12 kg in the other one, so it makes sense tethers weren't used in that setup. Those would probably have massed more then the propellant mass plus tank combined. I'm used to thinking of a probe having hundreds of kilo's of propellant onboard, not a mere couple dozen.

[Buster's Uncle]

They could have stayed away from metal for the tethers -maybe- but that tends to get into a bulk tradeoff if it even works, which isn't as inherent an expense, but can be very problematic depending on available space considerations.

[Rusty Edge]

wHAT'S UP with THIS COMET/ASTEROID/NICKLE-PLATED CYLINDER, OR WHATEVER IT IS?


I thought it was supposed to be a rock that would pass between the Earth and Moon sometime soon. I thought cool! Something like a solar eclipse or the space station that I can actually see here in the suburbs with all of the light pollution. But today I see something about NASA is asking for all telescopes to be trained on this thing, and that it might have had an abrupt course/speed correction, or is on a trajectory to make one near the sun. Speculation ensued.

Is this unusual for NASA to want all of the telescopes watching the same thing at the same time? Is it just paranoia that mistrusts the government, and sees alien probes and mother ships every time there' an unexplained light in the sky?

[Buster's Uncle]

Comet 3I/ATLAS?  Probably, somebody's given you a bum steer. 

Check the space news - I've been posting stories about it for weeks, and there's a space scientist, Arvi Loeb, who's been stirring up a bit of woo-woo on the subject for months.  3I/ATLAS is on an interstellar trajectory, and it's big, and it seems to have an unusual composition.  No close approach, but it'll pass sorta close to Jupiter soon on its way out of the solar system.

However, I believe there HAVE been two surprise near-Earth passes by asteroids in the last month - one, for sure, that they didn't know about until it had already zipped by hours before.

Easy to imagine someone conflating the two.  It'll turn up in the science news, which I'm not finished skimming for the day yet, for sure if it's on the level...

[Buster's Uncle]

Telescope reveals a growing tail on the comet that's visiting from another star

Here, Loeb, who is with Harvard, not NASA, calls for more eyes on the object:
Scientist Watching to See If Mysterious Object Visiting Our Solar System Releases Any Probes

Lori thinks he's being a nutter...

[Rusty Edge]

I think you're right, Buncle.

I won't post any links because of pop-up ad junk I got when I tried to back-track, but it would seem I was reading another article with Loeb quotes.

I read something else which offered an organic chemistry explanation. I will paraphrase. There are low density nickel and low density iron chemical solids which can form in the distant comet orbit. They glob onto space rocks. When they dive towards the sun, it melts/turns to gas at a lower temperature than the iron compounds, so it appears first on the spectrograph. It's not Nickle-plated, it's sort of coated and sheds it. The iron will follow at a higher temp as it nears the sun. It's not proof of intelligent design.


Niven taught me to think of a comet as a dirty snowball with gravel in it. This one sounds more like a rock with a frozen coating to me.  Is that a fair approximation?

[Buster's Uncle]

They haven't seen enough to tell much.  It was only spotted this summer, and it'll be gone before the year ends.

[Buster's Uncle]

New images of interstellar object 3I/ATLAS show giant 'jet' shooting toward the sun

[Buster's Uncle]

Astronomer Suspects Mysterious Object Is Up to No Good While It’s Hidden Behind the Sun: “If You Want to Take a Vacation, Take It Before Then”

[Lorizael]

Lori thinks he's being a nutter...

He's an astrophysicist (read: not an expert on comets, solar system astronomy, or observing) who got high on his own supply and refuses to listen to the people who study objects like this all the time (mostly my colleagues). Anyone else who made the claims (and basic mistakes) he has would never make the news, but because he's a tenured professor at Harvard with books to sell, we're forced to pretend he's saying interesting things.