In the past, NASA has led the design process and used what are known as cost-plus contracts. The companies were reimbursed for what they paid to build the spacecraft plus an additional fee for their services. But increasingly, NASA is using a markedly different approach with fixed-price contracts.

In contrast to Apollo, where the giant Saturn 5 rocket carried all of the pieces needed for a moon landing, NASA this time will employ a more complex choreography for the new missions, named Artemis. (In Greek mythology, Artemis is the twin sister of Apollo.)

First, NASA will construct an outpost called Gateway that will orbit the moon. Then the pieces of the landing system will be sent to the Gateway.

The landing system will consist of three pieces — a module that moves the astronauts and the other pieces of the lander from the Gateway to an orbit much closer to the moon; a descent module that guides the lander to the lunar surface; and an ascent module that lifts the astronauts back into space after their stay on the moon.

While the first Artemis moon landing will carry only two astronauts, the same as the Apollo missions, they should have more spacious accommodations. With the ascent stage stacked on top of the lander, the spacecraft will be somewhat heavier, somewhat wider and considerably taller than the Apollo landers.

That will allow a longer stay of about a week on the moon’s surface. During Apollo 11, the first moon landing in 1969, Neil Armstrong and Buzz Aldrin were on the moon for less than a day. During Apollo 17, the last time humans landed, Harrison Schmitt and Eugene Cernan stayed for just over three days.

When all of the pieces are in the place, the astronauts are to launch in an Orion capsule atop a Space Launch System rocket to the Gateway where they will board the lander for the moon. They are expected to land near the moon’s South Pole.