Hands-on operations with the Space Launch System (SLS) resumed this week, following a lengthy standdown due to the restrictions relating to COVID-19. This included a return to Green Run preparations at the Stennis Space Center, with “limited crews” preparing the Artemis-1 core stage on the B-2 test stand for what will be one of the most defining tests relating to the launch date. That maiden launch of NASA’s new rocket is awaiting a realigned launch date, which officials cite will be moved to “late 2021”.
The Green Run, which at one point was set to be deleted from the test flow to attempt to protect SLS’ schedule, will involve the Core Stage’s four RS-25 engines firing up on B-2 to provide key validation of the hardware’s readiness ahead of being shipped to the Kennedy Space Center (KSC).
The Green Run was still awaiting a firm date for the milestone firing, although the overall goal was to complete testing “in the summer” in preparation for a trip on the Pegasus Barge to Florida later this year.
However, Stennis moved to “Stage 4” – per the COVID shutdown – on March 16, with only the personnel needed to perform mission-essential activities related to the safety and security of the center allowed on site.
“Though Stennis remains in Stage 4 of NASA’s COVID-19 Response Framework, we assessed state and local conditions and worked with agency leadership to develop a plan to safely and methodically increase critical on-site work toward the launch of the next great era of space exploration,” noted Stennis Center Director Rick Gilbrech.
Work to bring the B-2 Test Stand out of its slumber includes restoring facility power and controls, as well as ensuring pressurized gas systems are at proper levels for SLS operators to proceed with testing activities.
“The test facility has been in standby mode, so we allotted two days to reestablish some facility support of mechanical and electrical systems that will also assist the vehicle contractors in performing their operations,” added Barry Robinson, project manager for the B-2 Test Stand SLS core stage Green Run testing at Stennis.
Following modal testing to validate structural analysis on the vehicle, the Stennis team had connected feed and pressure lines. They had about 10 days worth of integration work to get to “phase one” test activity when the center halted operations due to COVID restrictions.
A handful of workers remained on-site to keep the Core Stage safe and watch for water intrusions during several documented “rain days”.
With more workers returning to the B-2 stand, teams will start the ramp-up to phase one testing, starting with electrical checkouts, working through an avionics checklist and driving the Trust Vector Control (TVC) system for the engines.
With the flagship event of the Green Run being an eight-minute, full-duration hot fire of the core stage with its four RS-25 engines, passing that phase – and being ready to ship the stage to KSC – will provide schedule guidance, which has been fluid throughout the lifetime of SLS.
The Green Run was tracking an August test, which is now expected to occur sometime in mid-autumn – followed by shipping to KSC at the end of the year, or early in 2021.
Ahead of the next schedule realignment, which is set to occur next week, Tom Whitmeyer – NASA assistant deputy associate administrator – provided an overview at the NASA Advisory Council’s Human Exploration and Operations Committee.
Unsurprisingly, the anchor item for the overview was the status of the Green Run.
“The one thing that we’re really in the process of doing right now is that middle item, the core stage, it’s been manufactured and delivered to Stennis. It’s sitting in the test stand at Stennis, the B-2 test stand. We really need to get through what we call the Green Run test,” Mr. Whitmeyer said.
“When we complete the Green Run test, we’ll take that core stage, and literally begin to build up this integrated stack, test it at the Cape, and then fly it. We bring the motors in first, and then we drop the core stage in, and then we actually stack the rest of the vehicle. We’ll do a Wet Dress Rehearsal (WDR) next year, then we’ll get ready to fly.”
When the Core Stage arrives at KSC, it will be greeted in the Vehicle Assembly Building by the Mobile Launcher with the two Solid Rocket Boosters already stacked on its deck. This follows a similar path to during the Shuttle era, where the boosters would be “built-up” on the Mobile Launch Platform, ahead of receiving the External Tank.
The booster segments for Artemis-1 are already built and preparing to make the train journey from Utah. The latest L2 schedule for transportation cites a NET (No Earlier Than) departure date of next week, on a journey that will take around three weeks before arriving into KSC.
“Right now we currently have all the motor segments we need for this flight out in Utah, (stored) there to keep them dry,” added Mr. Whitmeyer. “Then what we will do is we will begin to transport those motor segments towards the KSC, and they’ll be delivered by rail car to KSC in the mid-June timeframe.”
The final element to be stacked in the VAB will be the Orion spacecraft, which is currently in storage at KSC after completing most of its pre-flight assembly.
“We actually have Orion, almost in a completed state, put it in temporary storage at this point – (ready to) begin the flight preparation processes with the completed vehicle, which involves putting high-pressure helium in its tanks and beginning the bi-prop loading operations at the Cape,” Mr. Whitmeyer continued.
“And by the time we have that completed, we should be in a stacked configuration with the core stage, and we’ll actually begin the integration of Orion then, to the vehicle.”
Per the launch date, the latest realignment was tracking a Summer 2021 launch of Artemis-1, before the COVID restrictions halted the bulk of SLS preparations. The SLS schedule has been slipping an average of one year, each year – although recent schedules had begun to slip only by a matter of months.
“We had for a year now maintained our schedule, in terms of getting that work done. We had some earlier delays in the program, but I think (recent schedules were) an indication of things that had really turned around with manufacturing and processing activities,” added Mr. Whitmeyer.
“SLS, the Marshall folks working with the Boeing team, had created a lot of manufacturing practices and really improved how we were going through these operations. And they held schedule for the entire year, and they actually held schedule when we got to Stennis, up to the point when we had temporary hold operations for the virus.”
Although Mr. Whitmeyer wouldn’t commit to an actual launch date, several references to the end of 2021 were made, ahead of next week’s official schedule announcement.
“That’s the reason I started with the mission map. It’s an incredible journey, it’s going to be an incredible flight for this hardware. And we’re going to really take it a step at a time and make sure we’re ready to commit ourselves to a launch later next year.
“We’re feeling fairly comfortable that we will be having the Artemis 1 mission towards the end of next year.”