Why is there no dust on the Lunar Lander's footpads?

[Edwardwb1001]

Echnaton and sts60 exhibit good sense and discernment.  I'm certainly going to study the photos of the area under the LM. I'm not here to try and purposefully be difficult, Jay.  So far, much of what you all say makes sense. Unlike the impression some believers are under, not all hoax believers are too stubborn or proud to finally say that they were wrong on certain matters.  To Jason - yes I do concede that 'billowing' would not apply in a vacuum, but I need to study the answers given further before I can accept that no dust at all would have fallen on the footpads.

Thank you for the answers given - I'm one hoax believer who does actually appreciate them!

[Abaddon]

Echnaton and sts60 exhibit good sense and discernment.  I'm certainly going to study the photos of the area under the LM. I'm not here to try and purposefully be difficult, Jay.  So far, much of what you all say makes sense. Unlike the impression some believers are under, not all hoax believers are too stubborn or proud to finally say that they were wrong on certain matters.  To Jason - yes I do concede that 'billowing' would not apply in a vacuum, but I need to study the answers given further before I can accept that no dust at all would have fallen on the footpads.

Thank you for the answers given - I'm one hoax believer who does actually appreciate them!

You have a couple of problems.

1. You have drifted from the OP. The OP was about dust on the pads. You have been provided with the reasons why there wasn't much, but the photographic record shows there was at least some. Try AS14-66-9235 for example.

2. You have diverted to the "crater under the LM" argument, without addressing the substantive issue of the OP. This presents you with a twofold problem:
a: You have moved the goalposts vis a vis the OP.
and
b: You must perforce justify why it is that earthly VTOL craft do not gouge out large craters, yet you expect that lunar craft should. Personally, I attribute this belief to Arthur C. Clarkes novella "A Fall of Moondust" which postulated that in some areas the lunar dust might be 30 meters deep. He wrote it in 1960 before any landings proved the regolith depth was mere inches, yet it remains a meme which HB types glom onto.

Finally, the Mars comparison is right out. Mars has an atmosphere which supports weather, the Moon does not.

[Edwardwb1001]

There is no 'problem' Abaddon, and neither have I moved the goalposts. The 'crater' question was simply an additional point.  As I said, I am looking at the photos and studying the responses.

I did not say that I expected the LM to gouge out a large crater. I referred to a crater - or indentation. The only problem which is evident, is that you are yet another member who possesses an inflated and unjustifiable opinion of your intellectual ability.

[cos]

you are yet another member who possesses an inflated and unjustifiable opinion of your intellectual ability.

From the man who didn't know there was an environmental difference between the moon & mars you might expect a little humility for a while.

[cos]

As I said, I am looking at the photos and studying the responses.

The problem is that without some sort of model to determine just how much soil the engine thrust could have moved, it is just idle speculation. Just what is it that informs your opinion and expectation? Certainly not the Harrier jump jet, which is more powerful and doesn't leave a crater.

On page 2 I posted a link to a couple of members attempt to formulate a model based on the known thrust of the engine and the density of the soil. This provides a figure of how much soil could physically have been shifted and it fits remarkably well with what was observed. I think this is an excellent (only sensible) starting point for how deep or otherwise we think the crater might be. If you have a better model or you can spot a flaw in the methodology, we will be happy to discuss it.

Incidentally, the description of the crater is just about the first thing Neil Armstrong describes after stepping off the LM. Why do that if you want to brush over the fact that 'special effects' have forgotten to dig the damn thing?! Makes no sense.

[Peter B]

Total LM thrust just before touchdown is around 2,500 lbf, of which up to 40% is pressure thrust {my emphasis} and thus quantitatively unconnected to plume impingement.

Apologies for the thread derail, but could you expand on this, please, Jay.

What is pressure thrust?

What does the balance of the thrust consist of?

In what ways do they differ?

Do the proportions change at different levels of thrust? Or for different types of engines?

Thank you.

[Echnaton]

There is no 'problem' Abaddon, and neither have I moved the goalposts. The 'crater' question was simply an additional point.  As I said, I am looking at the photos and studying the responses.

I did not say that I expected the LM to gouge out a large crater. I referred to a crater - or indentation. The only problem which is evident, is that you are yet another member who possesses an inflated and unjustifiable opinion of your intellectual ability.

More confirmation.

[smartcooky]

There is no 'problem' Abaddon, and neither have I moved the goalposts. The 'crater' question was simply an additional point.  As I said, I am looking at the photos and studying the responses.

You may not have moved the goal-posts per se, but you went onto a different subject (crater under the LM) before you acknowledged whether or not you were convinced by the arguments concerning your OP (dust on the lander pads)

The only problem which is evident, is that you are yet another member who possesses an inflated and unjustifiable opinion of your intellectual ability.

And who you are you to judge that? There are a good number of the regular posters in this forum who have clearly been involved in the aerospace industry for many years. I was 20 years in the Air Force involved in the repair, maintenance and refurbishment of Avionics systems, which includes radio, radar, electrical and instrumentation systems.

Incidentally, this constant changing of the subject is typical of HB behaviour, as is "abusing the messenger" when they fail to understand explanations that amount to the most basic principles of high school science.

So far, you have been given a generous benefit of a very large doubt, however, I think I am sense a gradual loss of patience on the part of some.

[ka9q]

C'mon guys, relax. When someone new asks a question, why not simply answer it as best you can without assuming some sort of hidden agenda right off the bat? He'll make his agenda, if he has one, obvious soon enough.

[Tanalia]

But let's compare like with like. How does the thrust of the DPS compare to a Robinson R-22?

Maximum certified (tested and legal) takeoff weight is listed as 1370 lb.  It likely has a safety margin, so maybe a maximum capability around 1500.

[Glom]

C'mon guys, relax. When someone new asks a question, why not simply answer it as best you can without assuming some sort of hidden agenda right off the bat? He'll make his agenda, if he has one, obvious soon enough.

Seconded. Regardless of whether we're dealing with typical HB behaviour, we have it within us to be the better men.

[Jason Thompson]

To Jason - yes I do concede that 'billowing' would not apply in a vacuum, but I need to study the answers given further before I can accept that no dust at all would have fallen on the footpads.

Why is it so hard for you to accept that dust kicked up with a velocity on the order of thousands of miles an hour would not fall on something barely three feet away from the point it was kicked up from, and even if it did it would be going so fast it would simply bounce off it?

Consider also that the engine was either shut down when the contact probes touched the surface, so when the footpads were still about three feet up and therefore above the dust which was entrained in a flow running close to the surface, or else was still running right up to the point the footpads touched the surface, in which case the exhaust flow would blow the dust away from the footpads anyway.

[Jason Thompson]

The only problem which is evident, is that you are yet another member who possesses an inflated and unjustifiable opinion of your intellectual ability.

OK, comments like this are what is unjustified. People on this forum habve been discussing this subject for years, and many of them, as you will have already seen, actually work in related fields professionally.You have a lot of very knowledgeable people here to answer your questions. Don't throw it back in their faces.

[Glom]

The only problem which is evident, is that you are yet another member who possesses an inflated and unjustifiable opinion of your intellectual ability.

OK, comments like this are what is unjustified. People on this forum habve been discussing this subject for years, and many of them, as you will have already seen, actually work in related fields professionally.You have a lot of very knowledgeable people here to answer your questions. Don't throw it back in their faces.

Ooh, I missed that bit. That's a whole new level of obnoxious.

Edward, on what basis do you assume the confidence of members here in their intellectual abilities is not justified? You're the one who struggled to grasp the concept of their being no billowing in a vacuum. You have hardly demonstrated the intellectual ability to pass judgement on others.

I'm sure you'd like to believe you talking with people who are about on your level but you're not.  The history of debate here is like a scrum half raping a dwarf, such is the disparity between the knowledge, intelligence and experience of the people here and the occasional hoax believer.

[Abaddon]

There is no 'problem' Abaddon, and neither have I moved the goalposts. The 'crater' question was simply an additional point.  As I said, I am looking at the photos and studying the responses.

I did not say that I expected the LM to gouge out a large crater. I referred to a crater - or indentation. The only problem which is evident, is that you are yet another member who possesses an inflated and unjustifiable opinion of your intellectual ability.

You have moved the goalposts, and furthermore, have descended into ad hom more rapidly than I would have thought.

I provided you with an example of dust on the pads. Others have provided you with the reasons why there is not much.
Your response is sly insults.