Back to the moon, after half a century of absence

After exactly 50 years, a lunar rocket is finally back on the launch pad at Kennedy Space Center, Florida. Next Monday, around 1:30 p.m. Dutch time, the 98-meter high SLS rocket will ascend to the moon.

The Artemis 1 mission is the first in a series to return humans to the moon for the first time since 1972. This time, the seats will still be occupied by test dummies.

The successor Artemis 2, scheduled for launch in 2024, will be manned. The four astronauts – three Americans and one Canadian – will orbit the moon. Only the next mission, Artemis 3, will deliver two astronauts to the moon. It will also include an American woman and the first person of color on the moon.

Last week, NASA announced the possible landing sites: 13 areas around the moon’s south pole. These areas are scientifically and logistically interesting because water ice may be hidden in the eternally shadowed craters: object of research and source of drinking water and rocket fuel.

The launch begins with a 2,500-ton rocket

In the next three planned Artemis flights, more moonwalkers will land and the Lunar Gateway, a space station orbiting the moon, will be built. For the first time, there will also be European astronauts, because the European Space Agency ESA is also participating in the Artemis programme.

“We designed and built the ESM, the European Service Module,” says Philippe Berthe, project manager at ESA. The ESM is the cylindrical module under the Orion capsule that supplies the astronauts with water, air, power, alignment and propulsion.

“On launch day, we will be on review of flight readinessten minutes before final countdown”, says Bertha. Then all teams from all subcomponents of SLS give their go/no-go final verdict. After launch, European engineers accompany their spacecraft on its 42-day flight. There is a two-person team in America, in direct contact with NASA, and a team of dozens of engineers at Estec, ESA’s test and development center in Noordwijk, which is essentially European mission control.

“The design and construction of the ESM is based on the experience we have gained at ATV,” says Berthe. The Automatic Transfer Vehicle was a space freighter that transported goods, food and scientific experiments to the International Space Station. “The ESM design was completely new, but we built on the same team with the same design philosophy. We were also used to working closely with NASA.”

The launch begins with a 2,500-ton rocket. Two minutes after launch, the spent booster side missiles are dropped, and after eight minutes the main stage is also burned out. In orbit, the second rocket stage ignites for 20 minutes, setting the Orion-ESM on course for the moon.

Turn in the opposite direction

Orion’s orbit around the moon has never been seen before, says Berthe. “It is a direct retrograde orbit, with the direction of rotation opposite to that of the moon.” At the moon, Orion gets one gravity assist, a dive that skims 60 miles (97 kilometers) from the surface and provides enough speed for an orbit traveling 40,000 kilometers behind the moon. “From that orbit you have easy access to all points on the moon’s surface and, moreover, the Earth is continuously in sight, so also in radio contact,” says Berthe. There, Orion completes two orbits of the moon and then another gravity assist set course back to Earth.

“There are five milestones during the flight,” says Berthe. “The first is the unfolding of the solar panels. After this, there are four big boosts, where the rocket engines change course. Because the boosts provide a significant shock, the solar panels are temporarily folded forward so that they do not break off.”

“The last lift is the most exciting,” says Berthe. Additionally, after 42 days Orion-ESM will be set on a fiery re-entry into Earth’s atmosphere at mach 32, or 32 times the speed of sound: about 40,000 kilometers per hour. “The shuttle returned at Mach 25, and Apollo at Mach 32. We’re a little over that.”

Burn or jump

The angle of attack must be very precise: too steep downward and the starship burns up. Not steep enough, and Orion could bounce off like a shattered rock, back into the galaxy. Orion disconnects from the ESM, only to fall back. Then the heat shield reaches temperatures of 2,800°C. Orion lands under three parachutes in the Pacific Ocean, not far from San Diego.

The Artemis program has had a long and complicated course. After the crash of the Space Shuttle Columbia in 2003, it became clear that the Space Shuttle was too expensive and too dangerous. US President George W. Bush ordered NASA to develop a new deep space program.

This Constellation program quickly ran into serious problems. After a test launch of the pencil-thin Ares I rocket in 2009, it was shut down. However, the partially developed Orion capsule was spared, making its first test flight in 2014. Shuttle parts such as rocket motors and booster shields were transferred to the Space Launch System (SLS), an old-school jumbo rocket: non-reusable, built with proven (or old-school) technology. SLS also experienced delays and budget overruns.

Not only the missiles, the destinations also changed. The Constellation program envisioned a manned return to the moon, and then possibly bringing humans to Mars. Under Barack Obama, that turned into a manned mission to Mars, followed by a mission to orbit an asteroid. Donald Trump made the moon the ultimate target again.

Transfer of astronauts

After the test flight Artemis 1 and Fly by Artemis 2, things get logistically complicated with Artemis 3, the new moon landing. The Orion capsule takes four astronauts to orbit the moon. Two are transferred to a previously launched Starship HLS (Human Landing System), a rocket to land at the moon’s south pole (and take off again for the return journey). Starship HLS is a manned version of Starship, the reusable rocket developed by the space company SpaceX. The starship has yet to make its first test flight to Earth orbit.

Artemis 3 requires HLS to refuel, so a Starship fuel depot must first be sent into orbit. And it needs to be refilled with the help of a few more Starship flights.

As if that wasn’t complicated enough, NASA, ESA and their Japanese and Canadian counterparts are also working on the Lunar Gateway, a space station orbiting the moon that can be temporarily inhabited as a base for lunar landings. Flights from Artemis 4 serve to further build the Gateway, and from there travel back and forth to the moon.

But then we are talking about 2026 at the earliest, in a sector where postponing and changing plans is more the rule than the exception. First, SLS’s debut flight must be successful. “It’s all been done before, but it’s still a challenge,” says Berthe, “we still have a lot to learn from this flight.”

Leave a Comment