The explosives had been designed as shaped charges, with geometry and backing to direct virtually all of their force along the door seam. With incendiary materials—basically thermite, that venerable mix of iron oxide and aluminum which burned at over twenty-five hundred degrees centigrade, and would do so even underwater or in Mars' almost nonexistent atmosphere—to hopefully continue the cutting, burning through anything that remained.
Madeline insisted that Joe cross the cavern first, while she and
A.J. served as his spotters. Then she scurried across herself. By now, crossing the cavern was almost routine. Experience had shown them that the stalactites only dropped pieces on rare occasions. They still maintained the spotting system, but no one had ever actually had to use it to avoid being struck.
They would trigger off the charges from the relative security of the floor of the rock crevice. Hathaway had almost insisted that they return aboveground altogether, but eventually they'd talked him out of it. The climb up the crevice was the slowest and most arduous part of the trip.
Fortunately, Chad Baird had sided with them in the dispute.
"That's all rock, Captain, with no ice or loose material to be shaken down. The charges Madeline set aren't that big—and there's all that empty space in the cavern to absorb what little shock waves get transmitted through the thin air. They'll be safe enough there."
Grudgingly, Hathaway had finally agreed. So, now, everyone was waiting on the crevice floor.
"Ready?" Joe asked. At the acknowledgements, he glanced at his display. "Okay, Madeline. Set it off."
The image of the Vault's sealed door, transmitted down A.J.'s line of bread-crumb transceivers, abruptly fuzzed and vanished in a fog of smoke and dust. Through the veil, five blazingly blue-white smears of light could dimly be made out, the incendiaries continuing their work. Joe imagined he heard a faint thud, but knew it had to be his imagination. The smoke became thick, but the most important thing about the image was that it continued to exist.
"No collapse. None of my sensors are showing any sign of movement, either," A.J. reported with satisfaction. "Let's head on up. By the time we get there, it should be done."
"No, let's wait until it's finished," Helen said. "I don't want to listen to Ken hollering at me afterward."
"There's no point in rushing, anyway," Madeline chimed in. "The wreckage will stay very hot for a while, and these suits were definitely not made to take steel-melting temperatures. Keep an eye on things in IR and make sure you don't touch anything without the right tools."
"Don't teach your grandfather how to use sensors," A.J. retorted. "I can see better in three spectra at once than you can in one. And I understand it all."
"To understand is not to act. I've seen you act without thinking. That was my caution."
"She's right, A.J.," Joe said.
"Well, of course you're on her side."
"I don't recall being the one who decided to run into burning buildings with nothing but balls, a blanket, and a VRD."
"Okay, okay. I get the point. I'll wait until I'm told it's safe before grabbing anything."
Eventually, Helen gave the signal. "Come along, people," said Madeline. "And everyone take your chunk of ice."
Even Bruce was there this time. It had become clear that aside from certain areas—which were now braced—it was reasonably safe to be underground here, and no one wanted to be left out of the chance to enter the Vault for the first time.
The smoke had mostly settled and was flowing away through the base, many of its components being heavier than anything the thin Martian atmosphere could support. By the time they finally reached the Vault, the air was almost clear. The sealed door still smoldered and glowed in places.
Madeline took her block of ice and motioned everyone to the side. Then, very gingerly, holding it only by her fingertips, pressed the ice block into one of the holes.
Steam blasted out, accompanied by high-pitched crackling, hissing noises. Madeline held the ice steady but made no effort to push it harder into the hole.
As her chunk melted away, the others methodically repeated the process, using thermal shock to hopefully finish the job of weakening the door—and, incidentally, cooling it to a workable temperature.
The cautious and methodical approach had been dictated by Joe. To something of his satisfaction, it was A.J. who graphically demonstrated why it was the right method. A.J. pressed his first chunk of ice into its hole with vigor and determination. The chunk of ice was blown out of the hole almost on contact, ripping itself out of the sensor expert's hands and continuing on, a hurtling twenty-kilo missile that could have hurt someone, if it hit the wrong way.