A good start, then!
Posted on 01/12/2005 11:21:56 AM PST by missyme
objects at the moment of impact -- 23,000 mph -- no explosives are needed for the job. The force of the smashup will be equivalent to 41/2 tons of TNT, creating a flash that just might be visible in the dark sky by the naked eye in one spectacular Fourth of July fireworks display.
Nothing like this has ever been attempted before.
"The most difficult and most challenging part is going to be the actual encounter because we're doing things that nobody has done before," said Jay Melosh, a planetary geologist at the University of Arizona.
Little is known about Comet Tempel 1, other than that it is an icy, rocky body about nine miles long and three miles wide. Scientists do not know whether the crust will be as hard as concrete or as flimsy as corn flakes.
"One of the scary things is that we won't actually know the shape and what it looks like until after we do the encounter," Melosh said.
The comet will be more than 80 million miles from Earth when the collision takes place. The resulting crater is expected to be anywhere from two to 14 stories deep, and perhaps 300 feet in diameter.
A jagged, cratered comet like the one headed for Earth in the 1998 movie "Deep Impact" would be difficult if not impossible to hit because of all the shadows, Melosh said. Comet Tempel 1 is believed to be smoother and easier to hit.
The scientists came up with the Deep Impact name independently of the movie studio, around the same time, neither knowing the other was choosing it, even though some members of NASA's Deep Impact team were consultants on the picture.
Deep Impact is carrying the most powerful telescope ever sent into deep space. It will remain with the mothership when the impactor springs free the day before the comet strike, and will observe the event from a safe 300 miles away. NASA space telescopes like the Hubble will view the collision, along with ground observatories and amateur astronomers.
The entire mission costs $330 million, all the way through the grand finale.
A good start, then!
Sounds like a good Independence Day! Hey, wasn't that a movie too?
I find it amazing that they can come up with a 1 second launch window and have credible hopes of hitting a moving target 80 million miles away.
Too bad Dan Rather isn't along for the ride.
Does anybody know why it had a launch window of only one second?
Probably because the relative speeds are so fast, that if they launched it even seconds later they'd need to plot a whole new course. The comet is moving at a relative speed of something like 23,000 mph.
It's the equivalent of hitting a golf ball 421 miles and making a hole in one.
There maybe a trajectory that uses the gravity of another planetary object to achieve the necessary speed.
Makes sense. Seems impossibly small though. I would think that even the slightest ability to tweak the trajectory early in the flight would make the launch window a bit easier to work with.
But this golf ball has corrective in-flight rockets!
Happy crash landing!
If this works it will be absolutely amazing.
T+plus 55 minutes. NASA says a good signal is being received from Deep Impact. Controllers are analyzing the data to verify the craft's status.
I wonder if they got that feet / meter thing worked out yet?
LVM
0 feet = 0 meters!
Hee hee!
Hey, this mission is being carried out by the same feet/meters crowd, so let's not rule anything out.
The only reason I can think of is that it's a really performance-limited mission, on the part of both the booster (get DI as high as possible, as accurately as possible), and Deep Impact (it takes propellant to account for the orbit plane changes associated with wider launch windows).
Note, BTW, that a "one-second launch window" doesn't really make exist. IIRC, the Delta launch sequencer works on the even second. So basically, they said: launch at exactly this time.
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