Liftoff was scheduled for early Wednesday morning from the Kennedy Space Center in Florida.  The test flight aims to send an empty crew capsule into distant lunar orbit, 50 years after NASA’s famous moon shots.
The project is years behind schedule and billions over budget.  The price tag for the test flight: more than US$4 billion.
A summary of the new rocket and capsule, part of NASA’s Artemis program, named after Apollo’s mythological twin sister:


ROCKET POWER 
At 322 feet (98 meters), the new rocket is shorter and thinner than the Saturn V rockets that launched 24 Apollo astronauts to the moon half a century ago.  But it’s more powerful, with 8.8 million pounds (4 million kg) of thrust.  It’s called the Space Launch System rocket, SLS for short, although a less heavy-handed name is under discussion.  Unlike the improved Saturn V, the new rocket has a pair of side boosters repurposed from NASA’s space shuttles.  Boosters peel off after two minutes, as do transport boosters.  The main stage continues to fire before crashing into the Pacific.  Less than two hours after liftoff, an upper stage sends the capsule, Orion, hurtling toward the moon.


SELENAKAVIOS 
NASA’s high-tech, automated Orion capsule is named after the constellation, among the brightest in the night sky.  At 11 feet (3 meters) tall, it is more spacious than the Apollo capsule, carrying four astronauts instead of three.  For the test flight, a full-size dummy in an orange flight suit occupies the pilot’s seat, equipped with vibration and acceleration sensors.  Two other mannequins made of material that simulates human tissue — heads and a female torso, but no limbs — measure cosmic radiation, one of the greatest dangers of spaceflight.  Unlike the rocket, Orion has been launched before, completing two orbits of Earth in 2014. For the test flight, the European Space Agency’s service module was attached for propulsion and solar power via four wings.


FLIGHT PLAN 
Orion’s flight is scheduled to last 25 days from landing in Florida to splashdown in the Pacific, about the same as astronaut trips.  It takes almost a week to reach the moon, 240,000 miles (386,000 kilometers) away.  After a close approach to the moon, the capsule enters a distant orbit with a far point of 38,000 miles (61,000 km).  This places Orion 280,000 miles (450,000 kilometers) from Earth, farther than Apollo.  The big test comes at the end of the mission, as Orion hits the atmosphere at 25,000 mph (40,000 km/h) on its way to a crash in the Pacific.  The heat shield uses the same material as the Apollo capsules to withstand re-entry temperatures of 5,000 degrees Fahrenheit (2,750 degrees Celsius).  However, the advanced design predicts faster, warmer returns by future Mars crews.


OITSOTOPUS 
In addition to three test dummies, the test flight includes a series of stowaways for deep space research.  Ten shoebox-sized satellites emerge as Orion races toward the moon.  NASA expects some to fail, given the low-cost, high-risk nature of these minisatellites.  In a salute back to the future, Orion carries some pieces of moon rock collected by Neil Armstrong and Buzz Aldrin of Apollo 11 in 1969, and a bolt from one of their rocket engines, salvaged from the sea a decade ago .


APOLLO VS.  ARTEMIS 
More than 50 years later, Apollo is still NASA’s greatest achievement.  Using technology from the 1960s, it took NASA just eight years from the launch of its first astronaut, Alan Shepard, to the landing of Armstrong and Aldrin on the moon.  By contrast, Artemis has already been delayed for more than a decade, despite being based on the short-lived Constellation lunar exploration program.  Twelve Apollo astronauts walked on the moon from 1969 to 1972, staying no more than three days at a time.  For Artemis, NASA will draw from a variety of astronauts and extend the time crews spend on the moon to at least a week.  The goal is to establish a long-term lunar presence that will grease the skids for sending humans to Mars.


WHAT’S NEXT 
Much remains to be done before astronauts set foot on the moon again.  A second test flight will send four astronauts around the moon and back, perhaps as early as 2024. A year or so later, NASA plans to send four more, with two of them touching down at the lunar south pole.  Orion doesn’t come with its own lunar rover like the Apollo spacecraft, so NASA hired Elon Musk’s SpaceX to provide its Starship spacecraft for the first Artemis landing.  Two other private companies are developing suits for moonwalking.  The sci-fi-looking Starship would dock with Orion on the moon and pick up a pair of astronauts on the surface and return to the capsule for the journey home.  So far, the Starship has only flown six miles (10 kilometers).