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

RTFA

[ari_j]

820 pounds, from the first sentence of paragraph 3.

Re:Expensive launch mass?

[HeghmoH]

The lump of copper is 820 pounds, and will be equivalent to 5 tons of TNT. If you sent an 820-pound lump of TNT, you would get an explosion of about 5.4 tons of TNT. An extra .4 tons-TNT increase, in exchange for a vastly more dangerous mission and chemical contamination is not a good trade.

At these speeds, the kinetic energy is so great that chemical explosives are nearly pointless.

Re:Silly question...

[MoonFog]

Nobody's sure what will happen next. There's a small chance the impactor will blow the 2-½-mile-long comet to smithereens, or simply bore through it like a bullet through a snowball. More likely, scientists say, it will blast open a crater the size of a football stadium. It all depends on what Tempel 1 is made of, and how sturdily it is composed. Which is exactly what scientists hope to learn.

In essence it appears they don't know jack shit what it really contains.

NASA Website

[themo0c0w]

This project has been around since 2001; probably a dup /. article somewhere... Anyway, here is the NASA website, which gives more details on the mission.

http://deepimpact.jpl.nasa.gov/

Re:Silly question...

[XenonDif]

to quote NASA:

"The impactor is made primarily of copper (49%) as opposed to aluminum (24%) because it minimizes corruption of spectral emission lines that are used to analyze the nucleus."

http://deepimpact.jpl.nasa.gov/tech/impactor.html

Re:Who Cares?

[Anonymous Coward]

Actually a large sum of that debt is to the people that live in this country.

Re:Consequences of destroying a comet

[r.jimenezz]

I mean, is it possible that important microorganisms or other important/rare/valuable occurences may be destroyed if this comment is blown up?

Nah... No offence intended but this is your run-of-the-mill, typical AC comment :)

Seriously though, you've got an interesting point. Even if no life is up there I wonder how smashing a comet affects things as a whole.

Re:This year

[novakyu]

From TFA: Unfortunately, comet watchers will have to plant themselves somewhere between New Zealand and the southwestern United States to see it.

'Got a nice yacht, perchance?

One more good reason...

[p_trekkie]

Another reason they are doing a kinetic impact is because they want to judge the structure of the comet. Right now, scientists don't really know if the comet's consistency is that of a fluffy snowball or a hard chunk of ice. If you used explosives, you would have melting of the ice, whatever its consistency, and would get less information about the construction of the comet. Once possibility is that the comet might be loosely packed enough that the impactor goes in one side and flies out the other....

Also, I'm surprised the article submitter didn't include a link to the mission website.....

Re:Who Cares?

[Anonymous Coward]

we still manage to keep our poor people fed (our homeless don't starve, they just live outside!)

Perhaps you should read this article

http://abcnews.go.com/US/wireStory?id=286105

"Unfortunately, the blessing of abundant food is not shared by all Americans," Iowa Gov. Tom Vilsack said. "A recent report from our Department of Agriculture documented an increase in hunger in America, particularly among our children."

Re:Expensive launch mass?

[Waffle Iron]

Finding themselves unable to afford chemical or nuclear explosives, NASA employees have spent the last four years collecting stray pennies

Hmmm... their experimental data is going to be skewed when they find out that today's pennies are actually 98% zinc.

Re:Expensive launch mass?

[luna69]

Ok, sorry in advance for being nitpicky but I enjoy this sort of thing. Mea culpa.

A quick calculation shows that the OP figure of 4.7 tons of TNT is high by about 0.12 ton TNT equiv.:

KE = 0.5 * 370kg * (23000mph)^2 = 1.956E17 ergs

1 ton TNT = 4.26E16 ergs (rough, but fairly good approx.)

1.95E17 ergs / (4.26E16 ergs) = 4.58 ton TNT equiv.

I actually work in support of this mission...

[Shag]

One of the 13 co-investigators on the Deep Impact science team is Karen Meech of the Institute for Astronomy at University of Hawaii.

A lot of observing and imaging of comets and their dust comas, and analysis of the resulting images, is being carried out by Jana Pittichova, a postdoctoral fellow (and triathlete!) on Karen's research team, primarily using the University's 88-inch telescope atop Mauna Kea.

Being one of the operators on that telescope, I've worked with Jana on several nights - probably one-third to one-half of the Meech team's total observing this semester.

Although I understand how the observations are carried out from a purely operational and practical standpoint, I haven't seen what the actual analysis looks like... and even if I did, the odds are good that I'd need a lot of explaining, since I'm not a Ph.D. myself!