On Wednesday, November 16, NASA successfully launched their most powerful vehicle ever developed: the Space Launch System, from historic Launch Complex 39B at NASA’s Kennedy Space Center in Florida, home to the Apollo and Space Shuttle missions to the Moon and Low Earth Orbit, respectively. Built on the legacy of the space shuttle, the SLS is propelled by four hydrogen-powered RS-25 engines and a pair of five-segment solid rocket boosters. Together they produce over 6.56 million lbs of thrust, propelling the Orion spacecraft to the Moon.

Two minutes into the flight of SLS, the two solid-rocket boosters separated while the core stage continued its journey. Approximately a minute later, the aerodynamic elements protecting the Orion spacecraft from Earth’s atmosphere were safely jettisoned. The 4 RS-25 engines continued to burn for another 6 minutes after which they shut down followed by the separation of the core stage and the Interim Cryogenic Propulsion System (ICPS) second stage.

The core stage is designed to target an unstable orbit which ensures that it safely reenters during its first orbit and breaks apart over a designated area in the Pacific Ocean. ICPS’s onboard RL-10-B-2 engine performed its first of two burns to insert the Orion spacecraft into a stable orbit and avoid the same fate as the Core stage. 

During this phase, Orion’s 4 solar arrays deployed, charging the spacecraft’s onboard batteries and providing it with much-needed power. An hour and 30 minutes after the launch, the second stage engine reignited to place the Orion spacecraft in a Trans-Lunar Injection trajectory. Since Artemis I is a test flight for SLS and Orion, it’ll instead place itself in a Distant Retrograde Orbit, a stable orbit where the spacecraft will orbit in the direction opposite to the direction in which the Moon orbits the Earth.

It is “distant” in the sense that instead of being near the Moon, it’ll pass beyond the Lagrange point of our celestial neighbor. Orion will travel over 386,243 kilometers (240,000 miles) from Earth and over 64,374 kilometers (40,000 miles) beyond the Moon at its farthest point in the orbit, making it the furthest distance a human-rated spacecraft has traveled beyond Earth.

By December 1, Orion will start its return journey back to Earth. When it approaches back to Earth, it’ll be traveling at nearly 40,000 kilometers per hour and experience temperatures up to 2,800 degrees Celsius during atmospheric re-entry, much faster and hotter than a return from Low Earth Orbit. While the heat shield has been extensively tested by Lockheed Martin and NASA, no test facility can recreate the conditions the heat shield will experience returning at lunar return speeds and the Artemis I mission will validate its performance being crews can fly aboard it.

After checking off all the required objectives, NASA will work towards the launch of Artemis II which will launch 3 American and 1 Canadian Astronaut to the Moon onboard the Orion spacecraft and SLS rocket. Orion will perform a lunar flyby test and return back to the Earth and is currently planned to be the first crewed mission beyond low earth orbit since Apollo 17 in 1972.

Artemis II will be followed up by Artemis III, which will be the first crewed lunar landing mission of the Artemis program. The second crewed launch will see 4 astronauts being launched into the NRHO orbit around the Moon. The Orion spacecraft will dock to the Starship Human Landing System (HLS) stationed in the orbit before the launch of SLS. 2 Astronauts will move to the lander while the other two will remain on the Orion.

Starship will descend down to the south pole of the moon where the astronauts will remain on the surface for at least 6.5 days and conduct up to 4 spacewalks to perform scientific observations, including sampling water ice. 

The Lunar Optimized Starship is being developed by SpaceX under NASA’s Option A Human Landing System program. It’ll be launched onboard the Super Heavy booster into low earth orbit from Pad 39A at Kennedy Space Center in Florida. Once stationed in a parking orbit, it’ll be refueled by multiple tanker Starships before boosting itself into a lunar near-rectilinear halo orbit. SpaceX is expected to launch the first orbital test flight of Starship very soon.

While Artemis-1 might be NASA’s first step back to the Moon after the Apollo program, it's not their first attempt. The dwindling space shuttle program called for a need for a new space program, one which can not only call for uninterrupted access to space from American soil but also return the country back to the Moon and ultimately land the first humans on Mars. Named the Constellation Program, it was introduced by President George W. Bush as the country wanted to rehabilitate its superiority in human spaceflight after the Challenger disaster. A key requirement was to retire the space shuttle and use its funding to develop a fleet of launch vehicles and crewed spacecraft.

However, the program — heavily reliant on cost-plus contracts — suffered from major delays and was well over budget. Under a cost-plus contract, a contractor is paid for all their expenses — including the failures — removing the incentive to innovate and complete the project, in contrast to the fixed price contract where the payment is made after achieving a milestone.

After 6 years and over $230 billion spent, the program yielded minimal progress and was canceled by President Barack Obama. America was once again left with no major space program and the morale of the whole industry was at an all-time low. Constellation might’ve not made much progress but it still gave hope that the leadership was still determined to achieve something that was previously made possible in 1969.

Constellation was canceled but one of its remnants still remained in active development: the Orion spacecraft. Originally, multiple versions of the spacecraft were planned for development. Block 1 Orion was planned to rendezvous and dock with the ISS, while the Block II and III variants were designed for deep space exploration. However post-cancellation, Orion underwent a heavy redesign for use in crewed missions to Mars while its LEO version was canceled and was replaced by a highly successful Commercial Crew program.

Orion’s launch vehicle was supposed to be the Ares I which was then replaced with the Space Launch System. Since the shuttle program was retired and the constellation program was canceled, politicians were worried about a huge layoff of contractors and engineers employed by the program. In 2010, Congress passed the “NASA Authorization Act of 2010” which was also signed by President Obama, directing the space agency to develop a new launch system based on the components and supply chain of the Space Shuttle and the Ares program. 

Developing SLS seemed like the fastest and the one with the lowest risk to get back to the Moon. Most of the components were already developed and heavily used during the Shuttle era, which included the two solid rocket boosters and most importantly, the hydrogen-powered RS-25 engines. The newest part of the rocket was the large orange core stage with liquid hydrogen and liquid oxygen tanks to feed into the four main engines and even this component was derived from the Shuttle’s external tank.

In September 2011, NASA had projected the development cost for the SLS to be at $18 billion, out of which $10 billion was for the SLS rocket, $6 billion for the Orion spacecraft, and $2 billion for upgrades to the launch pad and other facilities at the Kennedy Space Center.

A product not of NASA’s leadership but of congressional legislation, SLS is seen as a project designed not by the engineers but by the senators, even jokingly called the “Senate Launch System.” The Artemis program has evolved greatly to integrate commercial partners into the program to make it more sustainable but SLS and Orion are still the only launch systems to launch astronauts to the Moon.

Future rockets like Starship are currently under development and still quite a few years away from supporting deep-space human spaceflight.