Hi Tom,
There's another way to look at this. I'm sure you've heard on the news the occasional item about an asteroid or comet that might strike earth. Often these news items are accompanied with the predictions of scientists of the damage such a strike might cause on earth. Scientists believe that an asteroid or comet with a diameter of about 20 miles would be sufficient to wipe out life as we know it here on earth. The asteroid thought to have been a factor in the extinction of the dinosaurs is thought to have been around that diameter.
A comet of 20 miles diameter would contain about 4000 cubic miles of water. The water you're proposing to cover the earth would be about 400,000,000 cubic miles. That's 400 million cubic miles, about 100,000 times more water, and it corresponds to a comet about 1000 miles in diameter. That's roughly the distance from New York to Miami. Put that image in your mind. 1000 miles is 1/8 the diameter of the earth itself. This is huge, immense, enormous, titantic.
Now that we've established a sense of scale, let's put it in the context of your proposal. You're suggesting that sufficient energy equivalent to sending a comet of 1000 miles in diameter out into space was used to raise all this water above the atmosphere without superheating the atmosphere and wiping out all life on earth.
Have you ever watched a spacelaunch on TV with the tremendous and continuous blast of energy? All that energy is required to launch a payload weighing no more than several tons. Your water to cover the earth to a depth of a couple miles weighs 1.5 million tons. Let me put that in pounds. A spacelaunch payload might weigh 10,000 pounds. Your water weighs over 3,000,000,000 pounds. That's 3 billion pounds. That's the American billion with a "b". You need sufficient energy to launch that payload into space while keeping it from having any effect here on earth. Did you know that a safe distance to watch a spacelaunch at Cape Canaveral is several miles? Just to launch several tons?
And as others have noted, when this water returned to earth it would again wreak destruction with heat and energy.
Walt Brown's proposal was created in order to avoid invoking obvious miracles so that Creationism could seem more scientific, but all that does is change the nature of the miracle. He's chosen not to invoke the miracle of God merely causing rain to form from nothing, but his alternative requires invoking different miracles in order to protect life on earth from being cooked and flayed.
--Percy