### Recent Posts

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##### The Hoax Theory / Re: Gardum's thread
« Last post by Zakalwe on September 13, 2017, 03:13:26 PM »
And that, ladies and gents is why I come here. People with expertise in their field can explain concepts that they are intimately familiar with in ways that a pleb like me can understand.

Whereas a hoaxie takes a simple thing and twists it into something complicated (and, generally, totally incorrect).
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##### The Hoax Theory / Re: Gardum's thread
« Last post by JayUtah on September 13, 2017, 12:43:16 PM »
Everything that sees you radiates energy toward you.  Radiative heat transfer is the sum of all the net heat flows between you and everything you see/that sees you.

And that's the fun part to model for thermal analysis purposes.  Imagine you're laying on your back on the ground, and over you is a transparent hemispherical dome.  You have a stick with a Sharpie on it, long enough for you to inscribe the dome from underneath.  So for each object, you draw its outline on the dome from your vantage point, so faraway things have a small outline etc.  You just draw it as you see it from your position on the floor at the center of the dome.  Now hang a plumb-bob from each corner or contour of the image you drew on the dome for each object and mark the projected outline on the floor.  Obviously things directly above you transcribe down to the floor with little if any distortion.  Objects that were essentially on the horizon -- i.e., in a direction perpendicular to your plane of interest (the floor) -- are squished and narrowed.  Now for each object, consider the ratio of the area you outlined on the floor to the area of the whole circle of floor under the dome.  That gives you a rough attenuation factor for the energy you're receiving in radiant fashion from that object.  You can scale the amount of heat you compute it's emitting by that ratio and come up with a reasonable estimate for how much of that energy is arriving at some surface.

The lunar module actually had a problem with this on one of the missions that landed in the highlands.  A particular bit of equipment wasn't radiating away its heat at the expected rate.  Engineers figured out that because of the angle the LM had landed at, the radiator for that equipment actually had a view factor to the top of one of the mountains, and it was radiating enough heat onto the radiator to disrupt the equilibrium.  It had been designed to have a view factor only to empty space.
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##### General Discussion / Re: Falcon 9 Question ...
« Last post by Zakalwe on September 13, 2017, 11:56:27 AM »
I bet it will take a couple launches to get the bugs ironed out, but I also bet they'll get it in time.

Musk has said that the chances of the first being successful are pretty low. I really hope that he's lowballing us!

I'm not worried about landing, although watching two boosters land at the same time will be quite a show.

If it all goes to plan there'll be three boosters landing.

<edit> not all at the same time though!

https://www.instagram.com/p/BXXiVWFgphb/
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##### General Discussion / Re: Falcon 9 Question ...
« Last post by jfb on September 13, 2017, 11:43:08 AM »
Places where things will be "interesting" -

• Ignition - lighting up 27 engines at once will be fun (and probably very loud)
• MaxQ - that's where the fittings holding the boosters to the center core will be under the most stress
• Booster separation - that's where their aero modeling will be put to the test, making sure that the boosters fly away from the core instead of into it

I'm not worried about landing, although watching two boosters land at the same time will be quite a show.
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##### The Hoax Theory / Re: Gardum's thread
« Last post by nomuse on September 13, 2017, 11:08:53 AM »
If you are going to make an argument based on how you are the only one correctly interpreting a statement by our recent guest, the first thing you need to do is to be a hell of a lot clearer than you have been on how your interpretation differs.

I understand you are picking up on something you think is important, and that you believe should not be open to the interpretation given to it by people other than yourself.

If you are going to continue this, then I for one need you to explain explicitly. In your words, in a variety of words, in ways that aren't simply you copying a phrase or two and pointing at them and saying, "It's obvious, just read it!"

Perhaps a careful re-reading of Gardum's posts would be appropriate, (excepting the first, as I don't need a headache;)

I've already read them carefully, and none of them contain a statement that matches what Gillianren claims s/he said.

Here he implies exactly what you are looking for,

No, here s/he states something that is different than what I am looking for.

I've already pointed that out.  Several times.  Gardum did complain that people were picking on his/her errors; s/he did not complain that people were noticing his errors.

But thank you for pointing out that you are not capable of understanding the simple distinction between those two statements, even after having it explained to you several times.

Q.E.D.

More like Q.E.N.D.
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##### The Hoax Theory / Re: Gardum's thread
« Last post by Abaddon on September 13, 2017, 10:31:26 AM »
Being picky and pedantic about who said what gets us nowhere.

I think being intellectually dishonest gets us nowhere, and simply gives people like Gardum an opportunity to accuse the board of hypocrisy.

Bull**** is bull**** no matter who says it.  If everyone wants to pile up on Gardum because s/he posts bull****, then blubber like babies because someone called them on their own bull****, then they might want to get used to being called children, because it's going to happen a lot.

I didn't really want my first post on this forum to be something snarky to the effect of:  "Concern troll is concerned", but what the heck.

What exactly is your complaint?  What exactly do you hope to contribute to the discussion? Somebody wrote "noticed" when you feel they should have written "picked on".  A reasonably charitable reading would suggest that this was at worst a poor choice of words, and if that had actually been your complaint it would have been more constructive to point that out to start with.

It looks to me like what actually happend is that you missed something Gardum wrote and, when that was pointed out to you, you decided to double down and resort to hair-splitting and name-calling in order to save face rather than just admit that you missed it.

I don't buy your self-righteous posturing here, and I wish you'd stop.

I'll post something later (as in, after work) more to the topic of the thread.  Anyway, hi everybody!
Welcome.

Don't worry about that as your first post, I have no idea what burr is under Sandopan's saddle or why. It seems a trivial irrelevancy to me.

The simple fact is that Gardum has three posts. Mostly incoherent rambling with a large dollop of "What I did on my holidays" as though it was somehow relevant to the topic at hand. Clearly, he/she has no intention of engaging in any meaningful way. Typical seagull poster. Fly in, poop over everything and fly away again.

Maybe Gardum will prove me wrong, but I am not holding my breath.
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##### The Hoax Theory / Re: Gardum's thread
« Last post by bknight on September 13, 2017, 09:51:23 AM »
...
I'll post something later (as in, after work) more to the topic of the thread.  Anyway, hi everybody!

Welcome to the board.
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##### The Hoax Theory / Re: Gardum's thread
« Last post by sts60 on September 13, 2017, 09:48:22 AM »
This is kind of nitpicky, but some might get confused by what shade does in the radiative transfer regime.

If I am walking around at high Moon noon, and find myself getting too hot from the Sun, I can duck into the shade of a big rock, but still be heated by the solar energy reflected from the lunar surface (albedo heating), as well as the solar energy absorbed and re-emitted from the surface (infrared heating), even as my suit is radiating heat to deep space.

But I'm also radiating heat toward the lunar surface, and a (very small) amount of heat energy from deep space is impinging on my suit.  There's no one-way switch depending on your view to certain objects.  Your surface radiates energy away, proportional to the fourth power of your absolute surface temperature.  Everything that sees you radiates energy toward you.  Radiative heat transfer is the sum of all the net heat flows between you and everything you see/that sees you.

The deep space background is so "cold" from a radiative perspective that its radiative transfer to you is basically nil.  This is not the case for the Earth as viewed from an orbiting spacecraft, even at orbital night, where the Earth is busily rejecting daytime heat buildup to space.
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##### The Hoax Theory / Re: Gardum's thread
« Last post by Zakalwe on September 13, 2017, 08:02:48 AM »
I didn't really want my first post on this forum to be something snarky to the effect of:  "Concern troll is concerned", but what the heck.

Agreed!

Anyway, hi everybody!

[waves hello  ]
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##### The Hoax Theory / Re: Gardum's thread
« Last post by Zakalwe on September 13, 2017, 07:59:42 AM »

I said the object was in direct sunlight and at thermal equilibrium (therefore hot) and is then moved into the shade. The object can be cooled but NOT by convection the way it could be on Earth, because there is no air on the moon. Is that not correct?

PS:
Yes, it can radiate into space
Yes, any cooler surface in contact can conduct heat away

If an object is moved into direct shade, then it can be cooled by conduction if it is in contact with another object and by radiating it's heat into space. I was confused when you said that " if the object is placed in the shade, the ONLY thing that can cool the object is conduction."

The point I was making is that heat transfer does not work the same way in a vacuum that it does in an atmosphere.
100% this.
Its a common hoax trend to cry foul when things look different and act different to how their "common sense" tells them. Heat transfer and believing that the camera film would melt is a real "tell", along with waving flags and tyre marks!
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