The space agency has been fired up for a return to the moon at least since December 2017, when President Donald Trump signed White House Space Policy Directive 1, which urged a renewed focus on lunar missions.
"Beginning with missions beyond low-Earth orbit," the directive states, "the United States will lead the return of humans to the Moon for long-term exploration and utilization, followed by human missions to Mars and other destinations."
On Friday, those plans may have hit some turbulence. Trump tweeted that "NASA should NOT be talking about going to the Moon - We did that 50 years ago."
It was less than a month ago that the Trump administration said it wanted an extra $1.6 billion added to NASA's budget for next year to help pave the way for humans to return to the moon by 2024.
Whatever becomes of US plans to go to the moon -- or not -- we're all ready to celebrate the 50th anniversary of the Apollo 11 mission. It was July 20, 1969, whenand fellow astronaut Buzz Aldrin made cosmic history as they became the first humans ever to stand and walk on a heavenly body not called Earth.
It was a breathtaking engineering and logistical achievement. Humans had only started venturing into space less than a decade earlier -- and even then, just barely outside Earth's atmosphere. Our experience of space, which started with Russian cosmonaut Yuri Gagarin in April 1961, was still quite limited when Apollo 8 made a trip 'round the moon in December 1968, the first time humans had ever broken free of Earth's orbit.
But after a total of six moon landings in less than four years, that was it. Since Apollo 17 in December 1972, no one's been back to the moon. NASA spent the next several decades focused on the space shuttle and on missions to the International Space Station.
Now there are once again plans to put people on the moon. NASA says it expects to make a moon landing again by 2024 through its Artemis program, both for its own sake and as a stepping-stone toward eventual missions to Mars. Amazon founder Jeff Bezos and SpaceX founder Elon Musk have their eyes on lunar adventures as well.
As NASA and others get set to mark the 50th anniversary of the first moon landing, here's a look at that achievement -- and what lies ahead.
Real quick: How far away is the moon, anyway?
The distance from the Earth to the moon varies because of the moon's elliptical orbit, from about 225,000 miles (363,000 kilometers) to 252,000 miles. By comparison, the ISS is only about 250 miles away -- that is, one one-thousandth as far as the moon.
The Apollo missions needed roughly three days' travel time each way -- Apollo 11 got from Earth to lunar orbit at midday on day three of its mission. (For Apollo 15, it was about 4.5 days from Earth liftoff to touchdown on the lunar surface.)
That's an awfully long way to go. Why even bother?
Two words: space race. Starting in the 1950s, the US and the Soviet Union were going at it for bragging rights and military advantage, sending rockets, satellites, dogs and monkeys, and eventually people into the ether. Then, on May 25, 1961, President John F. Kennedy made a brash declaration: "I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to earth. No single space project in this period will be more exciting, or more impressive, or more important for the long-range exploration of space; and none will be so difficult or expensive to accomplish."
How did the astronauts get there?
The lunar missions lifted off atop a Saturn V rocket, to date the most powerful ever.
After separation from the Saturn rocket, the astronauts continued to the moon in the command service module. The CSM had three parts: the command module (CM), with the classic "space capsule" shape and containing the crew's quarters and flight controls; the expendable service module (SM), which provided propulsion and support systems; and the lunar module (LM), which looked like a geometry project with spindly legs and took two astronauts to the lunar surface while the third remained in the CM.
How did the Apollo 11 mission unfold? What exactly did Armstrong and Aldrin do?
First of all, they simply proved it could be done.
The overview: Apollo 11 lifted off from Launch Pad 39A at Kennedy Space Center in Florida on July 16 and returned to Earth on July 24, splashing down in the Pacific Ocean after traveling a total of 953,054 miles in eight days, three hours and 18 minutes.
The LM (nickname: Eagle) touched down in the Sea of Tranquility after a stressful final few minutes. "There were some pretty hairy moments," biographerin an interview. "The onboard computer was taking them down into a site that was not quite what they wanted, and Neil had to take over manually. They maybe had 20 or 30 seconds of fuel left when he actually got it down."
About four hours later, Armstrong stepped out, just before 11 p.m. ET on July 20, a Sunday. He was outside for about 2.5 hours, with Aldrin joining him for about 1.5 hours. They were on the moon for 21 hours, 36 minutes (including seven hours of sleep) before returning to orbit to rejoin the third member of the crew, Michael Collins, who'd been waiting, watching and worrying.
Venturing no more than 300 feet from the LM and working under a 200-degree sun, Armstrong and Aldrin -- like tourists everywhere -- took lots of photos and video, and gathered souvenirs in the form of moon rocks and soil samples. They also set up a couple of rudimentary experiments, one to measure seismic activity and another as a target for Earth-based lasers to measure Earth-moon distance precisely, which returned data for 71 days. They left behind an American flag, some of the most famous footprints in history, a coin-sized silicon disc etched in microscopic detail with messages from world leaders and a small plaque saying "We came in peace for all mankind."
Armstrong may have the most famous lines from the mission, and Collins the best book (Carrying the Fire), but Aldrin nailed the description of the moonscape: "magnificent desolation."
What else was going on in 1969?
It was a crazy time. Airline hijacking was a big thing, especially to Cuba. The Vietnam War was raging, as were protests against it. Honduras and El Salvador fought a "soccer war." The Stonewall Riots in New York took place in late June. Richard Nixon had only just begun his first term as US president.
For about a week as May turned into June, John Lennon and Yoko Ono staged their "bed-in" in Amsterdam, at which Lennon recorded Give Peace a Chance. The Beatles' Get Back was No. 1 for 5 weeks from May into June, and the Fifth Dimension's Aquarius/Let the Sun Shine was No. 2. David Bowie released Space Oddity on July 11. The middle of August would bring the Woodstock festival.
Debuts on TV that September and October would include Scooby-Doo, The Brady Bunch and Monty Python's Flying Circus.
And Turnabout Intruder, the final episode of the original Star Trek series, aired June 3.
How many people have been on the moon?
The Apollo missions put a total of 12 men on the lunar surface over the course of six visits. That's it. Then there were the others who've flown that astonishing distance but never touched down -- six CM pilots on the lunar landing missions, plus the crews of Apollo 8, 10 and 13. Three of those people have made the trip twice, so the grand total of humans who've been as far as the moon is 24.
What else has landed on the moon?
We've put all kinds of unmanned spacecraft on the moon, starting with the hard landing of the Soviet Union's Luna 2 in 1959. The US' first spacecraft on the moon, Ranger 4, arrived in April 1962. Both countries landed a number of other machines there during the 1960s, including five Surveyor spacecraft from the US. Only some of them were soft (or powered) landings.
More recently, other countries have been getting into the game. China put the Chang'e 3 onto the moon in 2013, making the first soft landing since Luna 24 in 1976. In January of this year, China's Chang'e 4 became the first spacecraft to land on the fabled dark side of the moon.
In April, Israel sent the Beresheet spacecraft to the moon, but with an unhappy ending -- it crashed there.
What comes next?
NASA plans to send astronauts back to the surface of the moon by 2024, in what's now known as the Artemis program, with a whole new rocket (the Space Launch System) and crew capsule (Orion). The program will eventually integrate a "gateway" spacecraft that will stay in lunar orbit while missions head down to the surface. Here's the timetable:
- Late 2019 -- First commercial deliveries/landers to the moon
- 2020 -- Launch of SLS/Orion, uncrewed, in Exploration Mission-1
- 2022 -- Crew around the moon in Exploration Mission-2
- 2022 -- By December, setup of the first gateway element (the power and propulsion system) for a one-year demo in space, aboard a private rocket
- 2023 -- Land a rover, with the help of the commercial space industry
- 2024 -- Americans on the moon (including the first woman)
- 2028 -- Sustained presence on moon
NASA also sees these moon missions as preparation for eventual crewed missions to Mars, tentatively in the 2030s.
In May, NASA named some of the companies that'll pitch in with the Artemis effort, including Boeing, Lockheed Martin, Blue Origin and SpaceX.
Also in May, Amazon and Blue Origin chief Jeff Bezos unveiled a design for a Blue Moon lunar lander, which in addition to people could carry rovers to carry out scientific missions and shoot off small satellites.
When can I go?
Soon, maybe, if you have lots of disposable income or the right connections. Elon Musk has plans to send the first commercial customer, Japanese billionaire Yusaku Maezawa, on a flight around the moon in SpaceX's forthcoming BFR rocket. Maezawa plans to invite a handful of artists to join him on that weeklong flight in 2023. (The trip does not include a moon landing.)