The Curse of Elon Musk: Redirect Satellites to Sun or His Backyard?

[DrStupid]

Too inefficient, especially without a cooling source.

Assuming the same size for collector and radiator I calculated a theoretical maximum of 0.85 % for the efficiency (according to Carnot's theorem). Is that possible? That would be really inefficient.

 

[russ_watters]

It seems to me reflected photons are wasted photons as far as energy generation is concerned. Why should solar panels be reflective?

An ideal solar panel wouldn't reflect anything but an ideal solar panel doesn't exist.

Most solar panels are black and reflect very little; the issue is the satellites themselves, which are mirrored for thermal management. If you made the satellites themselves black (or covered with solar panels), one side would be really hot and the other really cold.

Now, even at low reflectivity (a few percent), you'd get a lot of light from a flat solar panel, but it would be a rare, localized flare, not a continuous, widespread, even brightness reflection people are seeing.

 

[mfb]

The brightness during orbit raising comes mainly from the solar panel. It is very large compared to the main satellite. The brightness in the operational orbit comes from the satellite body.

 

[russ_watters]

The brightness during orbit raising comes mainly from the solar panel. It is very large compared to the main satellite.

But why would that cause it to reflect light toward Earth? Isn't it pointed directly at the sun?

 

[anorlunda]

Is this just a variant of Iridium Flares?

@russ_watters , you're an amateur astronomer, haven't you seen satellite flares before.
On my boat in the keys, the whole harbor watched for ISS flyovers and Iridium Flares, use the heavensabove website as a guide. https://en.wikipedia.org/wiki/Satellite_flare

Iridium flares[edit]
Double flare - Iridium 6 and its replacement, #51, both flare in a 21-second exposure.
If a first-generation Iridium satellite is still controlled, its flares can be predicted.[1] The Iridium communication satellites have three polished door-sized antennas, 120° apart and at 40° angles with the main bus. The forward antenna faces the direction the satellite is traveling. Occasionally, an antenna reflects sunlight directly down at Earth, creating a predictable and quickly moving illuminated spot on the surface below of about 10 km (6.2 mi) diameter. To an observer this looks like a bright flash, or flare in the sky, with a duration of a few seconds.

Ranging up to −9.5 magnitude, some of the flares are so bright that they can be seen in the daytime. This flashing has caused some annoyance to astronomers, as the flares occasionally disturb observations.[2]

The article also says:

Flares may also occur from solar panels, but they are not as bright (up to −3.5 magnitude).

 

[mfb]

But why would that cause it to reflect light toward Earth? Isn't it pointed directly at the sun?

Not while it is raising the orbit, where it flies in a configuration that reduces drag. See my previous post.

 

[trurle]

From this CNN article:
https://www.cnn.com/2020/01/29/tech/spacex-starlink-satellite-internet-launch-scn/index.html

"Astronomers have also raised concerns about the multitudes of Starlink satellites disrupting their view of the night sky. SpaceX says it's working with the science community on ways to address those issues."

The mfb have already mentioned dark coating, and the SpaceX have deployed a prototype of low-reflectance satellite. So called "Darksat", or Starlink-1130. Specifically for astronomers. The measured g-band brightness reduction is 55%.
https://arxiv.org/pdf/2003.07251.pdf

 

[mfb]

7.57 at 976 km is 7.0 at 550 km, below the visibility for the naked eye even under perfect viewing conditions (typically assumed to be 6 to 6.5). This doesn't include geometry corrections, but overall the conclusion is that Darksat-style satellites completely disappear to the naked eye. Good for a prototype. Musk said that future satellites should be even darker, making them easier to remove from pictures for astronomers.

I noted that Starlink-4 (the latest launch) seems to be harder to spot already, but I don't have precise numbers.

The next launch is planned for March 18, 12:21 UTC (in ~25 hours).

 

[lstellaus]

Even painted black the satellite would block a distant star. Trying to average multiple snaps would interfere with precision measurements needed to determine distance, mass, etc. It's about time to do something about these billionaires that think they do whatever they want.

 

[Helena Wells]

Summary:: this guy should be locked up !

Seriously, this guy has destroyed astronomy for amateur and professional alike
His actions are criminal and this is just the start
just one recent example ...

View attachment 256047Maybe he should redirect his satellites in a path that avoids blocking celestial objects that astronomers are interested in?
May I suggest a path directly INTO the sun? If not, how about directly into Elon's back yard? Either would suit me just fine...

All of Musk's satellites are solutions provided by Dr. Sheldon Cooper(when he was a kid) so if there is anyone to blame it is him.

 

[mfb]

Half a year and 6 launches later and astronomy still exists. Satellites now come with a sunshade that prevents the Sun from falling onto the most reflective surfaces. This is mainly relevant for satellites in their final orbit to avoid saturating astronomical sensors. In addition they change the orientation of the orbit-raising satellites when they are close to the terminator, making them much darker - this change largely affects the naked-eye visibility early on.

Even painted black the satellite would block a distant star.

That probability is utterly negligible, and even then it's for less than a millisecond.

Trying to average multiple snaps would interfere with precision measurements needed to determine distance, mass, etc.

Quite the opposite, you need to do that anyway.

It's about time to do something about these billionaires that think they do whatever they want.

Like regulating satellite launches? Great, because that's already being done.

 

[Helena Wells]

Half a year and 6 launches later and astronomy still exists. Satellites now come with a sunshade that prevents the Sun from falling onto the most reflective surfaces. This is mainly relevant for satellites in their final orbit to avoid saturating astronomical sensors. In addition they change the orientation of the orbit-raising satellites when they are close to the terminator, making them much darker - this change largely affects the naked-eye visibility early on.That probability is utterly negligible, and even then it's for less than a millisecond.Quite the opposite, you need to do that anyway.Like regulating satellite launches? Great, because that's already being done.

Maybe we should create stelites with big gravity(high density) so we could see the stars behind them due to gravitational lensing.

 

[Ibix]

Maybe we should create stelites with big gravity(high density) so we could see the stars behind them due to gravitational lensing.

You might want to run some numbers on that. To misquote Chief Brody, you're going to need a bigger rocket.

 

[Helena Wells]

You might want to run some numbers on that. To misquote Chief Brody, you're going to need a bigger rocket.

We would need a denser rocket not bigger. Probably made of lead and some of its oxides and we could see behind the satellite.

Lead has a density 1k times less than a neutron star so the effects are not neglible.

 

[etotheipi]

We would need a denser rocket not bigger. Probably made of lead and some of its oxides and we could see behind the satellite.

But even if you manage to fulfil this requirement, there's still the small issue of getting it off the ground

 

[Helena Wells]

But even if you manage to fulfil this requirement, there's still the small issue of getting it off the ground

Lead is dense not massive. So it won't be hard.

 

[etotheipi]

Lead is dense not massive. So it won't be hard.

but lensing is proportional to mass... it might take up less volume, but you must still do the same amount of work (and in the case of lead - an awful lot!) to bring it away from Earth! I dare say there's a reason that no one has ever tried to build a rocket out of lead...

 

[Helena Wells]

but lensing is proportional to mass... it might take up less volume, but you must still do essentially the same amount of work to bring it away from Earth! I dare say there's a reason that no one has ever tried to build a rocket out of lead...

Lensing is not just proportial to mass it is proportional to the object's density as well.
If that was the case then gravitational lensing of a neutron star could be the same with the gravitational lensing of the sun.

But yes a rocket made of lead will be more massive and we would need extra energy to lift it up.

 

[etotheipi]

Lensing is not just proportial to mass it is proportional to the object's density as well.

Well, mass is proportional to density, at constant volume, though Wikipedia states the dependency of the deflection angle $\theta$ explicitly with mass, as $\theta = \frac{4GM}{rc^2}$ if $r$ is the distance from the mass to the light.

But this is besides the point...

 

[Ibix]

Lead has a density 1k times less than a neutron star so the effects are not neglible.

As I say, you need to run the numbers.

The angle of deflection for light passing a distance $r$ from an object of mass $M$ is $\theta=\frac{4GM}{rc^2}$. The Hubble space telescope has a mass of around 11,000kg and an angular resolution of 1/20 arcsecond. Using Hubble's mass as a guide to what we can put into orbit and its angular resolution as a guide to the deflection we can detect, you would need all of that mass inside a radius of around 10^-26m. Note that the Schwarzschild radius associated with 11,000kg is approximately three orders of magnitude greater than this.

A lump of lead isn't even close to producing detectable deflection of light.

 

[Motore]

Lead has a density 1k times less than a neutron star so the effects are not neglible.

Wait, what? Did you confuse 1k (1000) with 10trillion (10000000000000)?

 

[Helena Wells]

No I am pretty sure it is 1k.

 

[Ibix]

No I am pretty sure it is 1k.

Please cite your sources for this claim.

Edit: While I'm waiting, nuclear diameters are of order 10^-14m and atomic diameters of order 10^-10m. Neutronium will, therefore, be around (10⁴)³ times denser than ordinary matter.

 

[Helena Wells]

Please cite your sources for this claim.

Edit: While I'm waiting, nuclear diameters are of order 10^-14m and atomic diameters of order 10^-10. Neutronium will, therefore, be around (10⁴)³ times denser than ordinary matter.

Ah yes it says white dwarfs not lead! Oups.

 

[Helena Wells]

Please cite your sources for this claim.

Edit: While I'm waiting, nuclear diameters are of order 10^-14m and atomic diameters of order 10^-10m. Neutronium will, therefore, be around (10⁴)³ times denser than ordinary matter.

Well blame Leonard for this.Always blame Leonard.