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Landing on asteroids may cause avalanches

asteroids comets avalanches force-chains

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#1    Waspie_Dwarf

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Posted 04 July 2013 - 02:47 PM

Microgravity memory-test for granular materials suggests landing on asteroids may cause long-distance avalanches


Royal Astronomical Society said:

Results from a microgravity experiment suggest that the rubble and dust covering asteroids and comets can feel changes in force-chains between particles over much larger distances than on Earth, making these surfaces less stable than previously imagined.  Dr Ben Rozitis of the Open University will present findings from the AstEx parabolic flight experiment at the National Astronomy Meeting in St Andrews on Thursday, 4 July.

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#2    Crashley

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Posted 05 July 2013 - 04:34 PM

Yeah, not so sure that is a wise idea. Im all for space exploration and discovery, but not to keen on people losing their lives in the process. More research needed. An unmanned mission, perhaps?


#3    danielost

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Posted 05 July 2013 - 06:19 PM

A unmanned mission won't work, the vessel wouldn't have the mass of a manned mission would.  Also, a robot wouln't need to keep making corrections that a man would.  The other problem is the manned ship might have enough mass to pull any loe rocks to it.

As for rock piles we just have to make sure we don't land on one.  That I where your unmanned mission would come into it.

I am a mormon.  If I don't use mormons believe, those my beliefs only.
I do not go to church haven't for thirty years.
There are other mormons on this site. So if I have misspoken about the beliefs. I welcome their input.
I am not perfect and never will be. I do strive to be true to myself. I do my best to stay true to the mormon faith. Thank for careing and if you don't peace be with you.

#4    Waspie_Dwarf

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Posted 05 July 2013 - 11:50 PM

View Postdanielost, on 05 July 2013 - 06:19 PM, said:

A unmanned mission won't work, the vessel wouldn't have the mass of a manned mission would.  Also, a robot wouln't need to keep making corrections that a man would.  The other problem is the manned ship might have enough mass to pull any loe rocks to it.

As for rock piles we just have to make sure we don't land on one.  That I where your unmanned mission would come into it.
Really!

Then you will have no difficulty in backing up your conclusions with the relevant evidence and mathematics. I look forward to it, because there is nothing in the original article that states that the phenomenon is limited to manned spacecraft or even mention of a minimum mass, so clearly you must have data of your own, not in the original article to be able to confidently come to such a conclusion..

In fact mass is only part of the problem, but I'm sure you will enlighten us with your calculations of kinetic energy.

Unless, of course, you are just making stuff up off again.

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#5    danielost

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Posted 06 July 2013 - 12:09 AM

I don't have the math and you know it.

But, we have already soft crashed a probe on one.  It is still there, not broadcasting.

And this is why I have been avoiding your threads.  Your nit picking.

I am a mormon.  If I don't use mormons believe, those my beliefs only.
I do not go to church haven't for thirty years.
There are other mormons on this site. So if I have misspoken about the beliefs. I welcome their input.
I am not perfect and never will be. I do strive to be true to myself. I do my best to stay true to the mormon faith. Thank for careing and if you don't peace be with you.

#6    Bavarian Raven

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Posted 06 July 2013 - 12:09 AM

Quote

Im all for space exploration and discovery, but not to keen on people losing their lives in the process

Exploration has always been a risky business, and lives will be lost. But if we are to survive/expand as a species, we must take those risks. And as of right now, all the people doing these jobs are doing so out of their own free will...


#7    Realm

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Posted 06 July 2013 - 01:24 AM

Japan has already landed on an asteroid, collected rock samples and returned to earth. Seems, humans could do that too.


#8    d e v i c e

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Posted 06 July 2013 - 01:36 AM

Cool.


#9    danielost

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Posted 06 July 2013 - 03:38 AM

Dwarf.  I have decided that I don't need math to answer your challenge.  I have not read any of the posts after my last one.

All I need is observance.  All matter in the universe has gravity from the smallest grain of sand to the galaxies.  Planets orbit the sun because it has the largest gravity field.  Moons orbit planets because their gravity field is closer and strong enough t over ride the suns.  That is why mercury and venus are the only planets to not have moons.

The largest probes we have sent out was the size of an sub.  These probes didn't need to return to earth.  If you send a manned space ship it needs to be large enough to carry enough fuel to get there and back.  The ship also has to be big enough to keep the crew alive.  The ship will need to be bigger than a capsule, depeended on how far the trip is.  I don't think anyone would be able to live in a capsule for more than a week.  

Thus if the ship lands on an asteroid its local gravity  might be sdtrong enough to override the asteriods gravity on small things like dust and small rocks near the landing site.  Of  course we could use as lander like on the moon.

I am a mormon.  If I don't use mormons believe, those my beliefs only.
I do not go to church haven't for thirty years.
There are other mormons on this site. So if I have misspoken about the beliefs. I welcome their input.
I am not perfect and never will be. I do strive to be true to myself. I do my best to stay true to the mormon faith. Thank for careing and if you don't peace be with you.

#10    JesseCuster

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Posted 06 July 2013 - 04:45 PM

View Postdanielost, on 06 July 2013 - 03:38 AM, said:

Thus if the ship lands on an asteroid its local gravity  might be sdtrong enough to override the asteriods gravity on small things like dust and small rocks near the landing site.  Of  course we could use as lander like on the moon.
Do you have any idea how weak the gravitational pull of a spacecraft is?  Gravity is an ridiculously weak force, it's only when massive amounts of matter clump together that it becomes relevant.

A very small asteroid of only a couple of miles in diameter is going to have a mass of billions of tonnes.  For comparison, the Apollo landing modules had a mass of about 10 tonnes.

Even factoring in a much larger lander of 100 tonnes, how is that going to override of the gravitational pull of something with millions of times more mass and attract any matter towards it?  And I'm deliberately choosing a very small asteroid.

Keep in mind that a 3km x 3km x 3km body with the same density of water is already going to have an extremely weak gravitational force, of the order of 1/100,000 g according to a quick calculation (does that qualify as microgravity?).  I'd say that figuring out how to just attach to it without the lander drifting off into space is a major issue as opposed to the non-issue of a spaceship attracting rocks and dust in the presence of a body millions of times larger in mass.

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#11    danielost

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Posted 06 July 2013 - 06:02 PM

Did you watch close encounters.  When the ship comes down on the site te scientist who are working under the ship were warned to be careful, due to gravety fluctuation.  That ship in comparisen to earth would be small rock on the asteroid.  I am sure the rocks and dust won't leave the ground, except for what I thrown up from the engines. But, maybe it will slide toward the ship.  If, as according to the story, the engines of the ship can cause a avolance on the other side of that rock.  Its gravity can't be to strong.

I am a mormon.  If I don't use mormons believe, those my beliefs only.
I do not go to church haven't for thirty years.
There are other mormons on this site. So if I have misspoken about the beliefs. I welcome their input.
I am not perfect and never will be. I do strive to be true to myself. I do my best to stay true to the mormon faith. Thank for careing and if you don't peace be with you.

#12    JesseCuster

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Posted 06 July 2013 - 06:29 PM

View Postdanielost, on 06 July 2013 - 06:02 PM, said:

Did you watch close encounters.  When the ship comes down on the site te scientist who are working under the ship were warned to be careful, due to gravety fluctuation.  That ship in comparisen to earth would be small rock on the asteroid.
Are you talking about the movie Close Encounters of the Third Kind?  Please tell me you're  not.

Quote

I am sure the rocks and dust won't leave the ground, except for what I thrown up from the engines. But, maybe it will slide toward the ship.  If, as according to the story, the engines of the ship can cause a avolance on the other side of that rock.  Its gravity can't be to strong.
Its gravity isn't strong.  It's enormously weak and the gravity of the ship is millions of times weaker than that.  That's why gravity isn't any sort of issue in this scenario.  The other forces causing the integrity of the asteroid (chemical, electromagnetic) and external forces like the engines of the lander are so much more relevant and powerful (by orders of magnitude) that I don't know what issue you think the gravitational pull of the ship is relevant.  Even if a handful of dust got attract toward the ship, what kind of issue could that raise?

"The first principle is that you must not fool yourself and you are the easiest person to fool." - Richard P. Feynman

#13    danielost

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Posted 06 July 2013 - 08:54 PM

There isn' t going to be a rescue, you have to think of everything that can go wrong immagined or real before you go.

I am a mormon.  If I don't use mormons believe, those my beliefs only.
I do not go to church haven't for thirty years.
There are other mormons on this site. So if I have misspoken about the beliefs. I welcome their input.
I am not perfect and never will be. I do strive to be true to myself. I do my best to stay true to the mormon faith. Thank for careing and if you don't peace be with you.

#14    Waspie_Dwarf

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Posted 07 July 2013 - 02:45 AM

View Postdanielost, on 06 July 2013 - 12:09 AM, said:

I don't have the math and you know it.
Yes I do know it. I also know you don't have a working knowledge of basic science. So that leads to the question why (in this thread and all the others where you make totally incorrect statements) do you constantly make statements of fact when you don't know what you are talking about? Claiming knowledge when you don't have it is dishonest behaviour on your part. If you would just point out that the posts were simply your opinion then they would still be wrong, but they would at least be honest.

View Postdanielost, on 06 July 2013 - 12:09 AM, said:

But, we have already soft crashed a probe on one. It is still there, not broadcasting.
And your point is?
You either haven't read the linked article or (more likely) haven't understood it. It says:

Quote

Many smaller asteroids are thought to be entirely granular in nature – piles of rock and gravel held together by gravity.
The probe, which you so vaguely refer to, was the NEAR Shoemaker spacecraft and it didn't make a soft crash (that is an oxymoron) it made a gentle touchdown on asteroid 433 Eros, Despite not having been designed to land it transmitted data from the surface for seven days (see HERE).

Eros is an S-type asteroid (see HERE) and therefore mostly iron in composition. Since it is not an asteroid which is granular in nature NEAR Shoemaker's findings can not be applied to this new research.

View Postdanielost, on 06 July 2013 - 12:09 AM, said:

And this is why I have been avoiding your threads. Your nit picking.
Sadly (as this thread demonstrates) you don't avoid them.

Nit picking would be picking on very small mistakes, not contradicting something which is totally wrong.

The problem is that the difference between what you think you know and what you actually know is huge and hence you make yourself look foolish time and time again. You compound this by never checking things before you post. Have you never heard of Google? You should try it some time. Then you wouldn't post so much rubbish and you would have links to back up your claims (remember links that back up claims? Those pesky things I include every time I rip your nonsense apart).

View Postdanielost, on 06 July 2013 - 03:38 AM, said:

Dwarf. I have decided that I don't need math to answer your challenge.
YOU don't get to decide what is and what isn't science (neither do I). Science requires empirical evidence and maths. As by your own admission you don't have the maths so you can't possibly meet the challenge, plain and simple.

View Postdanielost, on 06 July 2013 - 03:38 AM, said:

I have not read any of the posts after my last one.
Of course not, you wouldn't want to actually learn anything would you?

View Postdanielost, on 06 July 2013 - 03:38 AM, said:

All I need is observance.

By "observance" you mean you are just going to make stuff up again and post more rubbish don't you?

View Postdanielost, on 06 July 2013 - 03:38 AM, said:

All matter in the universe has gravity from the smallest grain of sand to the galaxies. Planets orbit the sun because it has the largest gravity field. Moons orbit planets because their gravity field is closer and strong enough t over ride the suns. That is why mercury and venus are the only planets to not have moons.
You're actually serious aren't you?

Sorry but you are wrong again with your statement on Mercury and Venus. Whilst it is true that Mercury's small size and proximity to the Sun mean that it has a tiny Hill Sphere (the sphere around a planet where the gravitational influence is stronger than that of the Sun's {see HERE}) Venus is more than capable of holding on to satellites. In fact one of the theories to explain it's slow rotation speed and retrograde rotation requires it to have had a large moon in the past (see HERE).

View Postdanielost, on 06 July 2013 - 03:38 AM, said:

The largest probes we have sent out was the size of an sub.
A totally meaningless statement given that a Russian Typhoon class submarine displaces 48,000 tons (see HERE).


View Postdanielost, on 06 July 2013 - 03:38 AM, said:

These probes didn't need to return to earth. If you send a manned space ship it needs to be large enough to carry enough fuel to get there and back. The ship also has to be big enough to keep the crew alive. The ship will need to be bigger than a capsule, depeended on how far the trip is. I don't think anyone would be able to live in a capsule for more than a week.
Really!!!

I think you need to inform NASA of this is they might do something stupid like keep two men in a capsule for 14 days. Opps, too late, they did that with Gemini VII in 1965 (see HERE).


View Postdanielost, on 06 July 2013 - 03:38 AM, said:

Thus if the ship lands on an asteroid its local gravity might be sdtrong enough to override the asteriods gravity on small things like dust and small rocks near the landing site. Of course we could use as lander like on the moon.
Totally meaningless with out the maths to back it up. I gave you a clue that mass was only part of the problem. You could have chosen to do some research, to have learnt something. Instead you fell back on you belief that what ever facts you happen to invent must be true just because you said so.

It is the energy of the landing that is important, in this case kinetic energy.

Ek = ½mv2

Where
Ek = kinetic energy
m = mass
v = velocity

Let's put in some figures. When the Constellation program was still active it was planned that the Altair  Lunar Surface Access Module would have a mass of about 23 tons (21,000 Kg). So let's use a lander of that mass.

Because it would land in a very similar manner to the Apollo Lunar Module it would land with a virtually zero vertical speed, as it would hover and then gently lower itself to the surface. Lets say that it lands at 10 mph (4.47 m/s) (in reality it would be a lot lower than that so I am over estimating the amount of energy).

We can put those figures into the equation and arrive at the amount of kinetic energy transferred from the lander to the surface of the asteroid.

Ek = ½ x 21000 x 4.472
= 10500 x 19.98
=209,799.5J

= 209.8 kJ

Now you claim that it is impossible for an unmanned mission to replicate the effect of a manned spacecraft landing on the surface of the asteroid.

If you understood the maths you would know that was nonsense. The fact that the velocity term in the equation is squared means that increasing the landing (or impact) velocity has a far bigger effect than altering the mass.

We can take the figure I have calculated and work backwards. Lets go with an easy enough velocity to achieve. Let's see what happens if you hit the asteroid with a probe travelling at the relatively low velocity of 1000 mph (447.04 m/s) and aim to impart the same amount of kinetic energy on the asteroid. We can work out what mass is needed.

Since Ek = ½mv2
then 2Ek = mv2
And therefore m = 2Ek/v2

Putting in the figures:

m = 2 x 209,799.5 / 447.042
m = 419599 / 199,844.76

m = 2.10 kg

So to hit the asteroid with the same energy as a 23 ton lander touching down at 10 mph all we need to do is hit it at 1000 mph with an impactor weighing just 4.6 pounds. That means not only is it possible to simulate a manned landing with an unmanned mission, technologically it is relatively easy to simulate a manned landing with an unmanned mission.

And that, danielost is the beauty of understanding very basic mathematics and science, you can work things out scientifically instead of making pure guesses and looking foolish when you are wrong.

Edited by Waspie_Dwarf, 07 July 2013 - 11:23 AM.
typos.

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#15    danielost

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Posted 07 July 2013 - 06:48 PM

Dwarf you need to take a reading class to comprehend what the words if might and maybe mean.  It's ok you have a mphd and a high school dtop out can keep up with you.  My gravity field has over powered the earths several times.  When a feather gets stuck to you thatis gravity not static electricity, unless you ave done something to get a charge.  Somethng with those tiny pellet sized packing bags.I did not make a solid statement about anything except for the gravity keeping earth and moon in their places.

Do you think nasa, had desinged apallo to survive if it blew up. No they didn't, but they did design it incase two things went wrong.  They were not thinking of it blowing up and the crew would be calling for help.  But apallo thirteen blew up.  The only reason they survived was of the triple by pass.


There will be no rescue if something goes wrong in space . Because, it could take a year to send crescue.

I am a mormon.  If I don't use mormons believe, those my beliefs only.
I do not go to church haven't for thirty years.
There are other mormons on this site. So if I have misspoken about the beliefs. I welcome their input.
I am not perfect and never will be. I do strive to be true to myself. I do my best to stay true to the mormon faith. Thank for careing and if you don't peace be with you.




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