this post was submitted on 15 Feb 2024
457 points (95.4% liked)

NonCredibleDefense

6670 readers
687 users here now

A community for your defence shitposting needs

Rules

1. Be niceDo not make personal attacks against each other, call for violence against anyone, or intentionally antagonize people in the comment sections.

2. Explain incorrect defense articles and takes

If you want to post a non-credible take, it must be from a "credible" source (news article, politician, or military leader) and must have a comment laying out exactly why it's non-credible. Low-hanging fruit such as random Twitter and YouTube comments belong in the Matrix chat.

3. Content must be relevant

Posts must be about military hardware or international security/defense. This is not the page to fawn over Youtube personalities, simp over political leaders, or discuss other areas of international policy.

4. No racism / hatespeech

No slurs. No advocating for the killing of people or insulting them based on physical, religious, or ideological traits.

5. No politics

We don't care if you're Republican, Democrat, Socialist, Stalinist, Baathist, or some other hot mess. Leave it at the door. This applies to comments as well.

6. No seriousposting

We don't want your uncut war footage, fundraisers, credible news articles, or other such things. The world is already serious enough as it is.

7. No classified material

Classified ‘western’ information is off limits regardless of how "open source" and "easy to find" it is.

8. Source artwork

If you use somebody's art in your post or as your post, the OP must provide a direct link to the art's source in the comment section, or a good reason why this was not possible (such as the artist deleting their account). The source should be a place that the artist themselves uploaded the art. A booru is not a source. A watermark is not a source.

9. No low-effort posts

No egregiously low effort posts. E.g. screenshots, recent reposts, simple reaction & template memes, and images with the punchline in the title. Put these in weekly Matrix chat instead.

10. Don't get us banned

No brigading or harassing other communities. Do not post memes with a "haha people that I hate died… haha" punchline or violating the sh.itjust.works rules (below). This includes content illegal in Canada.

11. No misinformation

NCD exists to make fun of misinformation, not to spread it. Make outlandish claims, but if your take doesn’t show signs of satire or exaggeration it will be removed. Misleading content may result in a ban. Regardless of source, don’t post obvious propaganda or fake news. Double-check facts and don't be an idiot.


Join our Matrix chatroom


Other communities you may be interested in


Banner made by u/Fertility18

founded 1 year ago
MODERATORS
 
you are viewing a single comment's thread
view the rest of the comments
[–] [email protected] 3 points 9 months ago* (last edited 9 months ago) (1 children)

Well but the actual mirrors would not work at all because of any number of reasons (among other reasons they can't track fast enough or precisely enough to actually hit a satellite, and they're going to have little imperfections in their flatness which will distort the reflected beam away from what the laws of optics say would happen for an idealized situation). The whole actually-shooting-down-satellites thing is clearly a joke; my point was more disagreeing with your description of how the laws work in the idealized situation.

Hmm... I am confident that optically, an idealized flat mirror will reflect a patch of sunbeam that's more collimated than any human-produced laser at any price. I'm less sure about the actual Ivanpah mirrors but I would guess that they are flat enough to produce a beam that's more collimated than a standard consumer laser. The thing is that that's more or less impossible to test... we can ask a physicist about the physical laws, but my guess is that they would be as clueless as I am about how precisely flat the mirrors actually are and of course there's a lot of wiggle room in how fancy a laser we want to say you can get.

We could ask one of those Youtubers like the ones I linked to if they want to fly a helicopter into the beam from one mirror at a great distance and do measurements of how much the beam had attenuated in practice, but that seems like a great setup to a "what could go wrong" disaster video in the making...

[–] [email protected] 0 points 9 months ago (1 children)

So bet or not dude? Cus you seem like you are backing out.

[–] [email protected] 3 points 9 months ago (2 children)

I will bet $1,000 (or $100) that this is wrong:

Lets assume each of the mirrors reflects 850 watts. The distance to the ISS is 408,000 meters.

The energy reflected by one mirror as received by the ISS is subject to the inverse square law (because it is incoherent).

E = (850 watts) / (4pi408000m)^2,^, or about 4.06x10 ^−10^ watts/m^2^

A 5 milliwatt, off the shelf laser pointer with a beam divergence of 1.5 millirads would deliver approximately 4.25x10^-9^ watts/m^2^, or about 10x as much energy as the 850 watt mirror.

You can not melt a spy satellite with mirrors. You might be able to with lasers. A laser will be approximately 8.9x10^6^ times as power effecient at getting light from earth to the ISS as a mirror would be.

And this is right:

E = 850 watts / 149,597,971 km^2 * 149,597,871 km^2 = 849.998864 watts

I will also bet on the behavior of an idealized flat mirror. I won't bet on whether you can actually shoot down satellites with the Ivanpah solar plant, because there are real-engineering issues that interfere with it aside from the physics of how mirrors and sunlight work.

If you want to try to chart a middle ground, I think it'd be better to talk about something actually testable than trying to argue about the real-world behavior of the Ivanpah mirrors. I'd be happy to bet $100 that:

Take a mirror and find the sun. Send a reflection to the wall nearest you. Then send the reflection to a wall further away. The reflection on the wall further away is larger and therefore, the energy more spread out.

... is wrong, as long as the mirror is flat. This one is easy to test so this might be a better bet.

[–] [email protected] 3 points 9 months ago (1 children)
[–] [email protected] 4 points 9 months ago

I care so much that I was outside earlier today, messing with my little reflective discs. It's actually really hard to get the angles right and I couldn't find a wall that was at the right type of angle to be able to test it without the reflection skewing from where the sun was, and a couple of people came near me, and clearly looked at me sort of wondering "what the hell is this guy doing."

I made no attempt to explain. Y'all can think I'm insane or whatever. I'm doing science. Get the fuck away.

[–] [email protected] -1 points 5 months ago* (last edited 5 months ago)

… is wrong, as long as the mirror is flat. This one is easy to test so this might be a better bet.

But that was never the bet. The bet was about transmitting light through the atmosphere. This is just some weird little aside you got yourself tangled in. More than happy to take on a bet about the transmission power of mirrors versus lasers from space, which is what were actually discussing.

(Dug this one out of the grave because I'm trying to find another bet I just won, so was searching for "bet")