NASA's Deep Impact

NivenMK1 writes "The Seattle Times has an interesting article on NASA's plan to nail the comet Tempel 1 with a chunk of copper the size of a bathtub on July 4 this year. This copper 'bullet' is intended to strike the comet at approximately 23,000 mph and hit with a force equivalent to 4.7 tons of TNT. Scientists hope to discover what exactly the comet is made of and what changes have occurred to the outer layers with reference to the core."

Comments

Re:Expensive launch mass?

[imsabbel]

You want to analyse the comet, which you can do by looking at the emission lines of the cloud forming after the impact, ect.
An explosive is normally composed of chemically very reactive components, that can react with each other and the material of the comet, making it very hard to discern what WAS there and what was created by the blast.

23,000 mph

[ari_j]

The article doesn't state if this velocity is relative to Cape Cod or relative to the comet. It makes a big difference.

Forgot one thing:

[imsabbel]

Look at the numbers:
The impact power of the copper rod is 4+ tonnes of TNT. IF you wanted to double the blast, you would have to send more than 4 tonnes of explosives.
at 30km/s+, the kinetic energy of the material is bigger than the chemical energy of explosives.
The added energy just doesnt matter anymore because it would be difficult to time the blast, plus the softness of the explosives would reduce the impact penetration.

Re:$311 million!!

[XenonDif]

Spending 311 million dollars without knowing what happens next doesnt seem a very nice idea.

Nasa is conducting the experiment precicely BECAUSE nobody know what will happen next. If we knew with certainty what was going to happen, THEN there wouldn't be a very good reason for carrying on with the experiment.

Last year they spent $200 billion blowing up comet Baghdad and we're all still waiting to see how that cliffhanger's going to end! This time it's cheaper and it doens't involve killing anybody.

Uh.... does this strike anybody else as wrong?

[John_Booty]

I've loved astronomy on a casual basis since childhood and I think it's important to mankind. I'm not one of those people who thinks we should abandon NASA spending because there are still underprivilidged marmasets living in a swamp somewhere or whatever.

But isn't this kind of, uh... wrong? Possibily destroying a comet? It seems so destructive to possibly break apart something that's been circling our sun for millions of years.

I understand that comets are more like "dirty snowballs" than things of infinite beauty, and I can definitely understand the scientific reasons for this mission because they're going to get all kinds of data that they couldn't get otherwise.

This seems kind of wrong to me, though.

Re:Uh.... does this strike anybody else as wrong?

[f4llenang3l]

It seems so destructive to possibly break apart something that's been circling our sun for millions of years.
Have you looked out your window recently?

Re:Uh.... does this strike anybody else as wrong?

[JerkBoB]

If you knew anything about the makeup of comets, you'd know that they're basically dirty snowballs.

Actually, we don't really know everything about the makeup of comets. In fact, that's the whole point of this mission: to find out more about what makes up comets. Our best guesses, based on data gathered during previous flybys and deductive reasoning, indicate that comets are mostly frozen water and some rocks mixed in, but we don't really know because we've never seen the inside of one.

Anyhow, it's not as if we're randomly blasting apart any and every comet that comes our way. We're not nuking Halley's Comet or anything.

As far as the mining issue is concerned, Deep Impact doesn't have anything to do with mining, directly. However, it adds to a body of research which could be used in the future. Even if comets typically don't have much more than water and some rocks, what better way to get a heck of a lot of water to Luna than to figure out a way to divert a comet into a lunar orbit? What if we need to figure out a way to divert/destroy a comet that's coming in too close for comfort? Etc. etc. It's empirical data that could be used in the future. It's not just fireworks, as you seem to be implying.

The intent of my post was not to question your intelligence, but I had to address what seemed to me to be a somewhat short-sighted and unimaginative perspective.

Re:Expensive launch mass?

[f4llenang3l]

I don't think the emission lines would actually provide much of a problem, it would be pretty easy to filter out the gaseous emissions of the explosives... I think the greater problem would be the unpredictability of the momentum problem if you added a chemical explosion. With a solid projectile, you can expect to learn a lot about the comet simply by what happens to the path of the intercepting projectile- ie shooting the snowball example. But, if you shoot a snowball with an RPG, or an iceball with an RPG, it's a lot harder to look at the resulting dispersion and tell what the target was made of after the fact.

Re:Expensive launch mass?

[HeghmoH]

The other 5 tons of TNT of explosion comes from the kinetic energy.

Re:$311 million!!

[novakyu]

Spending 311 million dollars without knowing what happens next doesnt seem a very nice idea.

And I quote:
"If we knew what we were doing it wouldn't be research."
- Albert Einstein

Re:$311 million!!

[jrp2]

Spending 311 million dollars without knowing what happens next doesnt seem a very nice idea.

I am sure there is military research aspect in this project too. The ability to hit a comet with a bathtub-sized hunk of metal is probably good practice for hitting an adversary's satellite with a bar of soap-sized hunk of metal.

I highly doubt this is purely civilian science in action.

Re:I don't know about you...

[flyingsquid]

In my opinion, Parisians are assholes. Maybe towards Americans in particular, but I was talking to a Spaniard who'd lived there for years and I got the impression from him that people there weren't particularly friendly towards anybody. However I've also been told that outside Paris, we're still remembered as those guys who got rid of the Germans. And from my very limited experience, they do seem to be much more welcoming towards Americans (or again, perhaps just towards anybody) outside Paris.

A couple years ago, right during the push for the Iraq invasion, I dislocated my shoulder on a train in Northern France(slept on it wrong) and ended up in the E.R. in Nancy-Ville or however the heck it's called. They were sort of amused by my hollering loudly in English ("Americain" one of the guys remarked to his buddy with a chuckle) but my brief stay there dealing with the E.R. doctors and nurses and people around town the next day, they didn't have a huge problem with me being an American who spoke three words of French, and impressed me as being pretty hospitable. Plus, I got a ride to the E.R. in an ambulance, an X-ray, some morphine(weird stuff... you still notice the pain sensations but it doesn't hurt), a relocated shoulder, and a few hours of sleep on a stretcher for, I shit you not, like 100 euros... this would cost easily a couple thousand in the states, without the ambulance ride (I know 'cause I've done this a lot). Socialized medicine, don't knock it till you've tried it.