The Space Launch System rocket, or SLS, is entering a critical year, with 2020 to see the completion and full-duration test firing of the Core Stage as well as the convergence of all flight elements for the Artemis 1 mission into the Kennedy Space Center.

Exactly when the first SLS mission will launch is still ambiguous. What is clear is there has been about a month of schedule loss in the last half of 2018, and that a Spring 2021 launch of Artemis 1 is “realistic.”

However, most of spring 2021 would result in night launches – which could push the mission into May for daylight launch considerations/needs.

Making progress:

For SLS, 2019 was an interesting year.

The most public occurrence for the program came when the NASA Administrator and current presidential administration threatened to take Boeing to task and look for commercial alternatives to SLS if the aerospace giant could not meet its timeline commitments building the massive core stage of the rocket.

The unusual public chastisement of Boeing was seen largely as a moment of theater designed to light a fire under Boeing to get the project moving along on the schedules the company had set for itself and the newly created “moon by 2024” timelines established by NASA.

The move came with the SLS Core Stage being years behind schedule.

While the merits of what commercial alternatives would actually be available to NASA if they abandoned the SLS program were questionable, the move nonetheless served as intended – with Boeing quickly whipping the SLS program into shape.

Part of this involved setting a deadline to ship the Core Stage from its Michoud Assembly Facility in Louisiana to the Stennis Space Center test site by the middle of December 2019.

That shipment has yet to occur, with the latest schedules indicating a shipment readiness date sometime in January 2020 – though a precise date is currently unknown.

Prior to the end of year holiday break, there had been a work-to date of 27 or 28 December for the pre-shipment readiness review that would formally clear the Core Stage for its move to Stennis.

Those pre-holiday timelines indicated the Core Stage would move No Earlier Than one week after a successful shipment review.

With most of the NASA workforce on leave until Monday, 6 January, it is unlikely the stage will move before mid-January at this point.

This is roughly one month down on the timeline established after NASA lit the fire under Boeing.

It should be noted that a single month of schedule slip in the last six months of 2019 is a far more successful rate of completion for the Core Stage than Boeing had been managing in the years prior.

In the long run, this one month slip will be negligible in terms of completing testing of the Core Stage and integrating it with the rest of the SLS rocket at the Kennedy Space Center.

How much do you know about the four RS-25 engines that will help power the first #Artemis mission to the Moon? TEST YOUR KNOWLEDGE >> https://t.co/haFGDeHj8T pic.twitter.com/lpx18qcjjw — NASA_SLS (@NASA_SLS) December 30, 2019

According to sources, if a “one month schedule loss every six months” pace can be maintained, the SLS should be ready for its first flight in Spring 2021.

Additionally, work on the SLS rocket’s Mobile Launcher, other KSC ground systems, and the software that will fly the vehicle is also not yet complete, with notes from the Kennedy Space Center indicating additional work is needed on the Mobile Launcher now that it is back in the Vehicle Assembly Building.

The Mobile Launcher enjoyed several months outside, perched atop Launch Complex 39B at the Florida Spaceport, and even underwent an unplanned trip back to the Vehicle Assembly Building to ride out Hurricane Dorian as the storm grazed the Spaceport in early September.

During its months at the pad, the Mobile Launcher underwent repeated cryogenic testing to ensure all of its propellant lines and systems functioned as intended.

It also underwent numerous wet flow tests to verify and validate the critical sound suppression system that will dampen a great deal of the acoustical energy unleashed by the SLS rocket’s 4 RS-25 engines and twin 5-segment Solid Rocket Boosters at liftoff.

Numerous NASA releases highlight the incredibly successful test campaign of the Mobile Launcher, noting all of its systems were verified and validated during its multi-month pad flow.

The Mobile Launcher was then rolled back to the VAB on the 19th and 20th of December.

Now that the Mobile Launcher is back in the Vehicle Assembly Building, having been brought back from the pad by Crawler Transporter #2, the other Crawler (#1) is now tasked with lifting and supporting the entire mass of the structure as engineers and technicians work to modify the “T-6 beam” on the platform.

The new year will also see the return of the Orion crew capsule from Ohio’s Plumbrook facility – where it is currently undergoing a series of vacuum, thermal, and acoustic tests to verify its readiness for the mission.

The Northrop Grumman Solid Rocket Booster segments will also ship from Utah in 2020. The booster segments have long since been completed and are in storage awaiting a NASA requested shipment date to the Kennedy Space Center.

All of this work will culminate in the launch of the Artemis 1 mission.

While NASA officially maintains the flight will launch No Earlier Than November 2020 – an appearance largely driven by a political desire to launch the rocket in a U.S. Presidential election year – the realistic schedules and timelines do not support a launch any earlier than “Late Spring 2021.”

What will now become a focus of the conversation surrounding SLS’s maiden launch outside of its technical readiness is whether NASA – as they have in the past – maintains the launch take place during daylight hours.

This has been a NASA mandate for all of its previous maiden flights and test launches as daylight ensures good tracking of the launch vehicle and clear visibility of the rocket during the first few minutes of flight.

This coming conversation revolves around the lunar launch trajectories and times – which just like the International Space Station are driven by where the Moon is in its orbit of Earth in relation to the launch site in Florida.

According to sources, a vast majority of the January to April 2021 launch windows are at night, with day launches becoming more prevalent and prolonged in May 2021.

The question that will be presented to NASA if SLS is ready to launch in early 2021 is whether the agency will maintain their standard for daylight launches of never-flown rockets or change their requirements to allow SLS to launch when the agency desires.