For a cruise to the moon, the capsule could "actually dock in space with the vehicle that's going to the moon," he said. The vehicle to take them there would be carried to orbit by a rocket capable of heavy lifting. "Going back to the moon is going to require pretty heavy payloads," Kahn said, "payloads that are probably upwards of 200,000 pounds. . . . You need a heavy-lift launch vehicle to do that."

Actually, he added, NASA already has such a vehicle: the shuttle assembly. But because the reusable orbiter weighs a great deal itself, it can only carry about 40,000 pounds of cargo.

"So what if you put the shuttle off and you just bolted on a payload carrier?" Kahn asked. Instead of an orbiter carrying people, there would be a shell with cargo inside — a moon lander, fuel, habitats. It could dock with astronauts brought up in the CEV and carry them to the moon.

Another design for a heavy-lift vehicle is to change the twin boosters from their present four-segment configuration to five segments each.

With the five-segment boosters and a larger liquid fuel tank, Kahn said, the payload could go up to 200,000 pounds.

For even more power, the payload could be centered above the tanks. With some redesign, "you could put way more weight — you could probably achieve 300,000 pounds," Kahn said.

That is for the more distant future. For the immediate goal, plans for a vehicle to carry the CEV are on the drawing boards.

To fly the CEV soon, he said, "you really don't have time to invent the new launch vehicle, invent new hardware and build new infrastructure. So the goal would be, how do you leverage what's in place today and use the systems in place, use the infrastructure?"

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