Deep Impact Mission Sounds Scary?

[errorist]

Deep Impact Mission Sounds Scary?

I don't like this misson. There are better ways to study this thing. Land on it and do the probing! Just what we need to do. Blow this thing to bits so it can rain down on us,possibly.It ain't worth the chance.

"The impact spacecraft will fly head-on into the comet at 23,000 mph. According to A'Hearn, some scientists think the impact could fracture the comet into several pieces, while others believe the impact will merely compress the cometary materials."

http://www.spacedaily.com/news/launchers-05b.html

 

[russ_watters]

I don't understand what you think the risk is. This comet never even gets within 50 million miles of the Earth (more than half the Earth's distance to the sun).

 

[errorist]

"According to A'Hearn, some scientists think the impact could fracture the comet into several pieces"

So some of those chunks could come this way or collide with an asteroid and send it this way ?? Who knows?

 

[russ_watters]

So some of those chunks could come this way or collide with an asteroid and send it this way ?? Who knows?

Why would you think that? The article is quite specific in saying that's utterly impossible. Orbits contain a lot of energy, and therefore it takes a lot of energy to change them. This comet's orbit is a long way from earth, so the energy required to change it enough to hit Earth - even for a tiny chunk of it - would be enormous.

There is no risk here.

 

[LunchBox]

If you look at the value of the Jacobi integral for the Sol-Earth-'comet of interest' system, that can tell you a lot.

Since this value is quite large for the comet targeted by Deep Impact (being run by UMCP... GO TERPS!), the amount of energy being imparted by the impactor is insufficient to change any meaningful portion of the comet's mass to a Jacobi integral value low enough to come within 1 AU of Sol.

Could a grain of dust be hurled our way? A slim maybe.

FYI:

They were considering several inscriptions for the impactor mass. One of them was...

"This one's for the dinosaurs."

Sweet...

Cheers...

 

[errorist]

Yep, and if they have miscalculated and the comet is broken into pieces like some scientists think it will. Then we may end up just like the dinosaurs.

 

[Janus]

Yep, and if they have miscalculated and the comet is broken into pieces like some scientists think it will. Then we may end up just like the dinosaurs.

Haven't you been reading what has been said above? The probe simply does not have the energy needed to alter the comet's trajectory enough, even if it fractures the comet, to have any of the pieces come anywhere near the Earth. The pieces will still follow the comet's initial course with very little spread.

The margin of error is no way near large enough to allow for the possibility of an Earth collision.
It's like saying that if I mis-judged how hard I threw a ball, I could accidentally throw it into orbit. My arm just does not have the ability to do so, so I don't need to consider the possibility.

 

[errorist]

So what if it hits a methane gas pocket and it explodes. Comets are known to have gas pockets! This would send comet debris all over the place.

 

[Janus]

So what if it hits a methane gas pocket and it explodes. Comets are known to have gas pockets! This would send comet debris all over the place.

The gas pocket would have to have a mass of many times that of the solid part of the Comet in order to cause a course change large enough to cause any sizeable piece Earthwards (not possible). And if it was that big, ( and if there were oxygen for the Methane to ignite with; Methane by itself does not explode), it would pulverize the comet, spreading its remains over a sphere. If that sphere got big enough to engulf the Earth, it would be so big that the comet particles would be so spread out, that it wouldn't be much better than a vacuum. the Earth wouldn't even notice that it was passing through it.

There is no plausible way that the probe can cause any problem for us.

 

[errorist]

The probe is traveling 23,000 mph when it impacts the Ice comet with methane it would cause the H20 to disassociate. Now you have methane,hydrogen and oxygen all mixed up.The only part left for the fire triangle is heat or friction and at those velocities! BOOM! We saw the same effects when the comet Shoemaker,Leavy slammed into Jupiter.Also,the copper projectile will expand into a gas to 10,000 times it original volume.

 

[Janus]

The probe is traveling 23,000 mph when it impacts the Ice comet with methane it would cause the H20 to disassociate. Now you have methane,hydrogen and oxygen all mixed up.The only part left for the fire triangle is heat or friction and at those velocities! BOOM! We saw the same effects when the comet Shoemaker,Leavy slammed into Jupiter.Also,the copper projectile will expand into a gas to 10,000 times it original volume.

That was just a side point to the fact that even if such a pocket exploded, there is no way that the explosion of such a gas pocket could send any piece of the comet larger than maybe a grain of sand on a trajectory where it could hit the Earth.

You just aren't grasping the magnitude of the energy needed to cause such an event when compared to the energy involved with the probe and any type of reaction it could have with the comet, explosive or not.

 

[errorist]

Nope, I don't see anywhere inside the article where it mentions stored energy inside the comet!

 

[Nereid]

Nope, I don't see anywhere inside the article where it mentions stored energy inside the comet!

Would you care to share with us the calculations that you have done which show that there is even a 1 in a billion chance of anything significant happening (wrt a sizable chunk of ex-comet impacting the Earth)?

 

[errorist]

Sounds like something the scientists shoud have considered before slamming a probe into it at 23,000 mph. They should land a probe on it first to research this thing further. I would have no Idea of how to calulate this without first landing a probe to see if any vast quanities of stored energy exist.

 

[Nereid]

Sounds like something the scientists shoud have considered before slamming a probe into it at 23,000 mph. They should land a probe on it first to research this thing further. I would have no Idea of how to calulate this without first landing a probe to see if any vast quanities of stored energy exist.

If you have no idea how to calculate the likelihood of there being any 'vast quantities of stored energy', and several folk have given you very good analyses that show that the possibility of their being a threat to Earth from the space mission are extremely remote, on what do you base your assertion (that scientists didn't consider these possibilities)?

 

[errorist]

Because nothing has been written about the possibility of stored energy within this comet.

 

[chroot]

errorist,

You can learn to do the calculations yourself, as Janus and others have done. You can reassure yourself by understanding the universe better. I know this situation sounds scary to you, but frankly, it's only scary to you because you don't understand it. You don't grasp the enormous distance, you don't grasp the enormous energy that would be required, and you don't grasp how comparitively little energy would be contained even in a nuclear warhead the size of the comet. If you learned to do the calculations yourself, you might believe the results. Until then, you'll have to decide for yourself if you want to side with the scientists, the people who have devoted much of their lives to their education and the advancement of human understanding, or to the crackpots, who rarely deeply understand anything yet all too often have no qualms about spreading false information in effort to attain notoriety.

- Warren

 

[errorist]

In order for me to do the calculations, I would need to land a probe there to search for such gas pockets then calculate the grams per cubic centimeter of mathane within the reservoirs along with the mass volume of such pockets. Until then I would be shooting in the dark.

 

[chroot]

No. You can calculate how much energy would be released by an exploding ball of methane gas, of any size you'd like, quite easily. If you'd like, you can imagine that the methane is pressurized to ten million times the Earth's atmospheric pressure -- a totally unrealistic condition -- just to err on the side of caution. Go ahead, show us how much energy would be released.

- Warren

 

[errorist]

Is it pressurized with 50 percent oxygen? Is the volume 5 cubic miles?

 

[chroot]

Sure, let's use those values.

- Warren

 

[errorist]

Ok go ahead and calculate it then.

 

[chroot]

I asked you to calculate it. I already have my answer, but I'm not going to just give it to you, because I'd like you to actually learn something from this exercise. Please calculate how much energy would be released by your exploding 5 cubic-mile ball of methane and oxygen. Show your work, and we'll see if our figures agree.

- Warren

 

[russ_watters]

Here's all the data you need to do the calculations (high school chemistry should give you all the equations):

The heat of combustion of methane is roughly 55.6 MJ/kg.
The density of methane is roughly 0.68kg/m^3 at 1atm and room temperature - use warren's 10 million atmospheres.

For comparison, a megaton of TNT releases about 4 GJ of energy.

If you need to make other assumptions feel free, just let us know what they are.

Have at it...

 

[errorist]

Very reassuring statement made by JPL! Cool, better get our hard hats on.That will protect us.

"The interesting part of this mission is that we don't really know what to expect," said Don Yeomans, a senior research scientist with the Deep Impact mission at NASA's Jet Propulsion Laboratory (JPL). "But no matter what happens, we'll observe the phenomena."



http://www.space.com/scienceastronomy/scitues_deepimpact_050111.html

 

[enigma]

No, Chicken Little...

He doesn't mean that the sky might fall.

Where were those calculations, again?

 

[russ_watters]

Very reassuring statement made by JPL! Cool, better get our hard hats on.That will protect us.

"The interesting part of this mission is that we don't really know what to expect," said Don Yeomans, a senior research scientist with the Deep Impact mission at NASA's Jet Propulsion Laboratory (JPL). "But no matter what happens, we'll observe the phenomena."

It also doesn't mean that the comet could crack-open and a giant, purple, singing dinosaur could pop out (the horror!). Not only are you not reading what's there, you're reading things that aren't there.

...and how are you coming on those calculations?

 

[errorist]

Actually it appears there are to many small pieces left I'll have to recalculate.

The explosion is at least ten million times to big!