Artemis II Moon mission transitioning from planning to preparation

by Philip Sloss

The first crewed Artemis mission is now the focus of NASA’s beyond-Earth orbit human spaceflight programs. Mission training for the recently-named crew for the Artemis II test flight is expected to begin in June, at just about the time that the mission integration review will be conducted.

The space agency has been planning for the lunar flyby mission for years, back to its origins in the last decade when it was called Exploration Mission-2 (EM-2). The Exploration Ground Systems (EGS), Orion, and Space Launch System (SLS) programs are factoring in the data and their experiences from the Artemis I mission that was completed at the end of last year as preparations for the spacecraft, launch vehicle, and ground launch infrastructure continue toward a launch no earlier than the end of 2024.
Mission Integration Review in June

“[The] first week of June, we’ll have a mission integration review (MIR); that’s a big enterprise level review on where are we with respect to planning for the mission, where are we on our [requirements], our launch commit criteria, where are we on the recovery decision criteria, on the flight rules, and we’re transitioning from kind of a mission design phase to a mission prep phase,” Matt Ramsey, NASA’s Artemis II Mission Manager, said in an April 7 interview with NSF.

Artemis II will be the second launch of the SLS Block 1 rocket, which will send Orion and crew into a couple of very high Earth orbits; the first high Earth orbit will take the spacecraft and crew out to a high point around 70,000 km, almost twice that of geosynchronous spacecraft. The apogee of the second high Earth orbit will go all the way out to the Moon, making a single flyby before returning to the Earth for re-entry, descent, and splashdown in the Pacific Ocean approximately 10 days after liftoff.

“We’ve kind of locked the mission down,” Ramsey said. “You’re trying to hone in on what the mission solution really looks like and we’re to the point now where we can kind of draw line in the sand and say here are the mission requirements and we’re going to start preparing all of these products that we’re going to need for Artemis II, so it’s the mission prep phase.”

“Really the MIR is the point of demarcation between the mission design and the mission prep.”

High-level mission map summary of Artemis II. (Credit: NASA)

Like Artemis I, Artemis II is headed to the Moon, and the overall launch opportunities have a very similar pattern. With essentially the same rocket and the same celestial mechanics, the launch periods for Artemis II will follow the same outline as those for Artemis I.

The SLS Block 1 vehicle can send Orion to the Moon in approximately two-week long, alternating periods; about two weeks of launch opportunities would be followed by about two weeks without opportunities.  Following the successful Artemis I uncrewed test flight, NASA will now have some additional flexibility to go along with the experience and learning gained from the first SLS launch and a second recovery of the Orion Crew Module.

Unlike Artemis I, Artemis II will not have any daylight constraints; Artemis I launched at night but was required to splash down during daylight. For Artemis II, neither launch nor landing and recovery are required during daylight.

“[A daylight launch is] not a requirement and we’ve removed the recovery requirement having to be in daylight, also,” Ramsey said. “That was a requirement for Artemis I, but it is not moving forward.”

NASA will also bring a second, large liquid hydrogen (LH2) storage sphere online at Launch Pad 39B beginning with Artemis II. Construction of the sphere was completed before Artemis I, but integrating the additional storage capability into the ground launch system was always planned for between the first and second SLS launches.

The additional LH2 capacity will give the EGS launch team more opportunities to make SLS launch attempts within a set period of time. “On Artemis I, we had no more than three attempts in seven days and you had to have 48 hours between attempts one and two and then 72 [hours] between [attempts] two and three,” Ramsey explained.

“For Artemis II, we have the ability to [make] four attempts in six days and there’s a 24-hour turnaround between [attempts] one and two and then [a minimum of] 48 hours between [attempts] two and three and [between attempts] three and four. So, if we scrubbed on day one we could turn around the next day; [we] have about 1.4 million gallon [capacity in the new] liquid hydrogen sphere, so that really helps us for launch attempts.

“So, 24 hours between one and two, and then 48 between two and three and three and four. And those are really kind of guidelines, because depending on why you scrub for…in between two and three, if you don’t load hydrogen then you could go the next day.”

Headed into the Artemis II launch campaign, with vehicle integration (“stacking”) currently planned to begin next year in 2024, other constraints and some of the “limited operational life items” that came up during the Artemis I campaign may also be factors in shaping launch availability. Above and beyond the celestial mechanics, the flight termination system (FTS) has time constraints on its operational life; currently, that will have the same 25-day maximum that it had for Artemis I.

“We will be using the same con-ops (concept of operations) that we started with for Artemis I,” Ramsey said. Likewise, for things like the “stack life” of the solid rocket booster (SRB) motor segments, which have a generic, 12-month constraint, Ramsey said there are no changes to those constraints.

NASA is not planning on the SRBs being stacked for over 12 months for Artemis II, but as with Artemis I, they will do extended life analysis for flight-specific waivers if necessary.

(Credit: Thomas Burghardt for NSF)

(Photo Caption: Two large, LH2 storage spheres at KSC Launch Pad 39B are seen in the background of this NSF flyover image from January 2023. The larger sphere on the left is a newly constructed storage tank that is being integrated into the EGS ground launch infrastructure beginning with Artemis II. The second LH2 sphere will give EGS the capability to perform more launch attempts in a shorter period of time, if that becomes necessary for a given launch campaign. Pad 39B’s liquid oxygen sphere is seen in the foreground in the lower left.)

On launch day, boarding the crew on Orion at the launch pad will be new to the countdown. The length of time the crew can be lying on their seats in the Crew Module, will also be a new launch day constraint.

Going in, the plan is for the crew to begin getting into their seats three hours and fifteen minutes before the opening of the launch window, which can be as long as two hours. “The TPM, the technical performance metric, that we’re shooting for is three hours and fifteen minutes,” Ramsey said. “The requirement is we can’t have the astronauts on their backs for more than five hours and 15 minutes.”

Once both of the SLS liquid-propellant stages, the Core Stage and the ICPS are fully loaded with liquid hydrogen and liquid oxygen, and are in stable replenish, then the crew will be allowed to go to the pad to board Orion.

“Once get into stable replenish for the LOX (liquid oxygen) and hydrogen then we start loading the crew and the clock starts when the first crew member is on back,” Ramsey said. “Then you load the rest of the crew members.

“That three hours and 15 [minutes] is targeted to when you load the first crew member, and there are multiple reasons why that requirement is [a total of] 5 hours and 15 minutes.”

Proximity Operations Demonstration added to Flight Plan

Prior to its renaming, Artemis II was called Exploration Mission-2 (EM-2); although the mission was always planned as the first crewed test flight, the concept and planning for the mission went through a few changes in the last decade. It was moved to the still-being-developed SLS Block 1B vehicle when the exploration upper stage officially started in 2016.

Then EM-2 was moved back to the Block 1 vehicle in 2018 after the U.S. Congress started funding a second SLS mobile launcher. By the end of 2018, the mission was re-baselined with a few notable changes from what was EM-1 at the time, soon to be branded Artemis I.

That mission plan included a different sequence of events after core stage main engine cut-off (MECO) and separation, with a short burn of the SLS interim cryogenic propulsion stage (ICPS) occurring a few minutes later before Orion deployed its four solar array wings. A high Earth orbit has long been planned for the mission, but in 2018 the high point, or apogee, was significantly raised to up over 100,000 km for an orbital period of around 42 hours.

(Credit: Mack Crawford for NSF)

(Photo Caption: As a part of the proximity operations and handling qualities demonstration, the Artemis II crew flies Orion in for a close approach to the ICPS, which still has the Orion stage adapter and spacecraft adapter cone attached to its forward end.)

Shortly after that 2018 baseline update, NASA’s lunar plans and strategy changed; in March 2019, the Trump administration made a crewed lunar landing no later than the end of 2024 the agency’s top goal, and NASA subsequently began looking at the rebranded Artemis manifest and ways to reduce risks to the lunar landing schedule. For Artemis II, NASA evaluated moving up rendezvous, proximity operations, and docking capabilities planned for Orion on subsequent flights and eventually decided later that year on a narrower-scope proximity operations demonstration hand-flown by the flight crew.

The current mission plan includes that and other changes to that “pre-Artemis” baseline. The SLS core stage and boosters will insert Orion and ICPS into an initial orbit with an apogee of ~2,220 km and a suborbital perigee of  ~28 km.

The post-MECO sequence of events now follow the one seen for Artemis I, with Orion’s solar arrays deployed first and the ICPS perigee raise maneuver performed at about 50 minutes after liftoff to raise the perigee up to 185 km. About an hour later, around 1 hour, 50 minutes after liftoff, ICPS will make a long apogee raise burn (ARB); the ARB raises apogee to approximately 74,000 km and also decreases perigee to zero, yielding an orbital period of about 24 hours rather than the 42-hour long orbit previously planned.

Even though the perigee of the high Earth orbit is suborbital, the vehicle won’t reach that part of the orbit for almost 24 hours. In the meantime, Orion will separate from ICPS and the crew will begin the proximity operations demonstration.

“It’s not an automated [demonstration],” Ramsey said. “We do have the docking camera [that the crew will use].”

“The intent there is to separate from ICPS, and it’s to establish some rough and fine handling qualities. The commander and the pilot will be doing those maneuvers with the onboard hand controls. Orion separates from the ICPS, it translates to about 300 feet, and then it turns around and it looks back at the ICPS.”

“Then it approaches the ICPS,” Ramsey continued. “Orion is responsible for all of that, it approaches it to about 30 feet and then backs off and then does some coarse handling approaches to ICPS again and this is head-on. It’s coming back and looking at the top of the [Orion Stage Adapter], the diaphragm of the OSA, that’s where the docking target is.”

“Then it backs away, the ICPS does a maneuver, the Orion comes up to its side and does the same type of maneuvers, that docking target is located on one of the X-braces of the ICPS,” Ramsey explained. “Then it starts to back away and then it continues to back away until it leaves the ICPS’s area.”

The Artemis II Service Module is seen in late February during preparations for a direct field acoustic test. (Credit: NASA/Kim Shiflett)

Orion will also perform an upper stage separation burn about five hours after liftoff to put further distance with the ICPS and ICPS will perform a disposal maneuver around the same time to change the perigee of its orbit to -37 km, to target a specific disposal footprint at the end of the long, 24-hour orbital period.

“[ICPS] has batteries and it doesn’t have solar arrays, so it’s got to operate within the constraints of the batteries; [after the disposal burn] it’s spinning up and deploying the secondary payloads, and then it’s [spinning back down],” Ramsey said.

Halfway through the high Earth orbit, about 13 hours after liftoff, Orion will perform a perigee raise burn to once again raise the low point of the orbit back to 185 km. Assuming all the new crew and life support systems on Orion are operating well and everyone is “go,” approximately 25 hours after liftoff Orion would fire its main engine to perform the trans-lunar injection (TLI) burn, sending the spacecraft and crew around the Moon on a “free return” flyby trajectory.

Overview of Mission Planning Milestones

The four-person flight crew for Artemis II is expected to begin mission-specific training in June. Ramsey said that there is a backup crew plan for the mission, but decisions on that will be some time in the future. “The plan as far has been communicated to me is to have a backup crew member, to be named later,” he said.

The crew will begin training around the same time that NASA holds the mission integration review. The review is planned around the launch minus-18-month (L-18) timeframe, which corresponds to the no-earlier-than late November/early December 2024 target date that the EGS, Orion, and SLS programs are working toward.

(Credit: NASA/Michael DeMocker)

(Photo Caption: Core stage-2 is repositioned in the final assembly area at Michoud Assembly Facility on March 17 after the engine section was structurally mated to the rest of the stage. Prime contractor Boeing is working to complete final assembly of the stage in 2023.)

The pre-flight analysis work is going on in parallel with preparation of the spacecraft, launch vehicle, and ground systems hardware and software. “Part of that is this first flight readiness assessment cycle (FRAC), so the first launch period we expect to fly in, we’ll be working that analysis cycle now until probably the fall,” Ramsey said.

“On Artemis I, we had about nine months prior to the mission we would have to start the next launch period. [If the target date moves,] then we would have to start working the next [launch period] and maybe the next one and we would have to be working those as we were progressing towards the launch because of just the time it takes to do the analysis and update all the products.”

“We’ll have that same flow of activities for Artemis II. We’re starting FRAC-0 now, the next set of rolling launch windows will probably start in the winter timeframe, maybe the early spring,” Ramsey added. “We’ll also do the flight [operations] review, that is a transition from the mission prep phase that we’re currently going into, to the mission execution phase.”

The individual launch and flight control teams will be doing training simulations on their own leading into next year; as the launch date gets closer next year, integrated and joint integrated simulations will also be conducted. “We’ll be doing a lot of training and that’s about L-6, L-7 months,” Ramsey said. “We’ll be doing a ton of training around that timeframe, integrated sims.

“The crew will be doing all their training, which is fairly substantial, starting right at the time of MIR and they’ve got a lot of training that they’ve got to do. [As for] the flight control team and the launch control team, they’ll start probably [around] L-9 [months], kind of hot and heavy training for mission integrated sims and then the MMT (Mission Management Team) sims will occur.

“It’s going to be really busy, L-6 to L-7 timeframe,” he added.
The target for Artemis II launch readiness is currently driven by the schedule and progress of spacecraft and launch vehicle assembly. The Orion spacecraft for Artemis II is the first with full support for a crew of astronauts and assembly and test of the crew and service modules is the primary critical path. The last public update in early March projected that standalone integration and testing of the two modules would be completed by June, which is when the two would be mated for launch.

When prime contractor Lockheed Martin completes overall integration and testing of Orion in the operations and checkout building at Kennedy Space Center (KSC), they will officially turn the spacecraft over to EGS for launch processing. The EGS timeline for Orion forecasts about eight months from handover to launch readiness; if Artemis II is going to be ready to fly before the close of 2024, Orion will need to be ready for that handover next spring, about a year from now.F

The elements of the SLS launch vehicle for Artemis II are expected to be delivered to KSC before the end of the year. With the exception of the SRB aft skirts and forward assemblies that are processed at KSC, integration and testing of the rest of the launch hardware occurs at facilities around the U.S.

The 10 solid propellant motor segments for Artemis II were completed a long time ago and have been in storage in Utah; they are expected to be transported by rail from Northrop Grumman’s Promontory facilities in the second half of 2023. United Launch Alliance (ULA) assembled the ICPS for the mission at its Decatur, Alabama, facility and the stage was shipped to Florida in 2021; it is now undergoing final ULA preps before being handed over to EGS.

The SLS interstage adapters, the launch vehicle stage adapter, and the Orion stage adapter are also completed and still in storage at Marshall Space Flight Center; they will also be transported to KSC later this year.

The major piece of SLS hardware still under construction is the core stage; the engine section/boattail assembly was mated to the rest of the stage in mid-March at the Michoud assembly facility in New Orleans. RS-25 engine installation, final outfitting, and integrated functional testing of the stage remain to be completed.

“Engine installation will begin in July,” NASA spokesperson Corinne Beckinger said in an email. “Teams are working toward a late fall delivery date to Kennedy Space Center.”

The Core Stage might not be needed for stacking in Florida until mid-2024, though, so there is still margin in that schedule.

(Lead image: The Earth and the Moon as seen from Orion on Flight Day 13 of the Artemis I mission. Credit: NASA.)

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