EGS synchronizing Artemis 1 Orion, SLS Booster preps with Core Stage schedule

by Philip Sloss

“We wanted to [find] a place that we control, and the main area there that is clean is the MPPF. And it eventually needs to go in there anyway to service the reaction control system, [and] there are two tanks for that.” The original plan was for ICPS to move into the MPPF for its RCS hydrazine servicing after Orion had left the building, so the offline operations team had to do some research on putting them in the same building months before they are stacked together in the VAB.

“We did a quick study on cohabitation of the ICPS and CSM (Crew and Service Module) and whether there were any issues with loading one or the other, and we worked with our site safety to make sure that there were no exceedances of what the facilities were rated for as far as explosive safety and shielding barriers. So everybody gave us a thumbs up, and that’s how we ended up where we are today,” Pena noted. “For Artemis 2 we would try to time things such that it’s done more serially, but the good thing is that we have shown that this works if we have to use it as a fallback option.”

A limited life clock will also affect the timing of the ICPS servicing in the MPPF. “Similar to the Orion helium tanks, the ICPS also has a wetted life requirement,” Pena said. “It might be close to 400 days, so that’s another area where we want to do that as late in the flow as possible.”

“Right now the plan is to do the ICPS servicing after we’re done with all the Orion servicing. So the last thing that we’re planning on doing is loading fuel into Orion, so following the hydrazine load around early-May, then we’re going to get into the ICPS servicing. So that’s the game plan right now.”

One other part of the game plan is an exit strategy, because now with ICPS in the MPPF, the upper stage is sitting in the transfer aisle blocking the door. “About mid-May is when we’re going to do that ICPS servicing, and the way that the facility is set up, the ICPS has to depart before Orion can depart,” Pena said.

“We’ll keep an eye on how things are going in the VAB with Core Stage integration and LVSA integration, and once they’re ready for receiving the ICPS, we’ll go ahead and transport it to the VAB. If they’re not ready for it, we are able to just get the ICPS out of the way and get Orion rolling to the LASF. But the intent right now is just in time delivery.”

Credit: NASA/Glenn Benson.

(Photo Caption: With Orion looking on, the Artemis 1 ICPS (background left) arrives in the MPPF on January 28. The upper stage will have its attitude control system tanks filled with hydrazine for flight in the MPPF before being stacked with the rest of the SLS in the VAB.)

Boosters almost Core Stage ready

In the VAB, the five-segment SLS Boosters are assembled on Mobile Launcher-1 in High Bay 3. “At this point we’re doing really well,” Lanham said. “All [ten] motor segments have been stacked, as have the forward assemblies, so from a stacking standpoint we are complete. We’re close to being Core Stage ready.”

“What we’re doing currently is we’re closing out the joints, which includes putting some instrumentation around the joints and then bonding cork around each joint. At this point, we’ve done six of ten joints with the corking, and we are doing another one today. Basically, we’re looking to finish up nine of the ten joints by the end of the week, early next week.”

“The tenth joint is on the left forward assembly,” Lanham added. “We’ll need to wait until after we do a push-pull test on the booster itself, and then we can get in and do that joint; so at that point that’ll kind of close out the joints.

“Then we have systems tunnel work to do, which will include some DFI (Development Flight Instrumentation), as well as putting in those linear shaped charges along that systems tunnel.”

Similar to the process for the overall Artemis 1 vehicle, the elements need more work after the physical hardware connections before they are functional, and they need to be tested to verify they work. For the Boosters, which have avionics in the forward and aft assemblies, they need to wait until the Core Stage arrives as it has the flight computers and software that command and control both elements.

“There’s checkouts once we power up the Boosters later in the flow that we’ll be doing,” Lanham said. “We’ll obviously check out the instrumentation as we’re running it, but the big power-up testing will come later during our Integrated Verification Test.”

Credit: Stephen Marr for NSF.

(Photo Caption: The bottom of the two fully-assembled SLS Boosters are seen stacked from the zero-level deck of the Mobile Launcher in High Bay 3 of the VAB. In this view taken on March 24, the umbilical tower of the ML is behind the camera. The two Tail Service Mast Umbilicals are seen in between the boosters; those will be connected to umbilical plates on the Core Stage engine section when it is finally mated to the Boosters.)

Next in line after the Core Stage is connected to the two Boosters will be the Launch Vehicle Stage Adapter (LVSA) that connects the ICPS with the Core Stage. “From an LVSA standpoint, it’s in High Bay 2 at this point, we’re kind of waiting to bring it over to High Bay 4, at which point we’ll get into our work on that,” Lanham noted.

“There’s not a whole lot we’ve got to do there; I believe we’ve got to remove some instrumentation before we lift it up and over and onto the stack when we’re ready.”

Cubesat preparations impacted by COVID

Thirteen cubesats will fly as secondary payloads on Artemis 1 in the Orion Stage Adapter (OSA) that connects Orion with the ICPS; the adapter will stay with the SLS upper stage, and the payloads will be deployed some time after Orion separates on the way to the Moon. “We have the flight OSA in the SSPF; it’s actually been ready for quite a while,” Pena noted. “It’s just waiting for the payloads to arrive.”

Aside from the Core Stage, the cubesats are the only other Artemis 1 hardware due to arrive at the launch site. “There’s 13 cubesats, and most of them are ready to ship today. If I were to work with the SLS team and poll those payload developer teams, I think a majority of them are ready today,” Pena said.

“But some of them have had challenges, both technical challenges with some of their propulsion or comm (communication) issues, but they’ve also had COVID-related challenges. These cubesats for the most part are developed by small teams on shoestring budgets, so technical impacts and personnel impacts hit them pretty hard.”

Credit: NASA/Glenn Benson.

(Photo Caption: The Orion Stage Adapter for Artemis 1 in the Space Station Processing Facility following arrival at Kennedy Space Center in April, 2018. Parts of the cubesat deployment system can be seen around the top circumference. NASA is looking to install the 13 cubesats manifested for Artemis 1 in the OSA in April or May.)

NASA brought in extra support hardware to provide schedule flexibility during the Artemis 1 stacking and vehicle checkout testing process. An Orion mass simulator – that also mimics the center of gravity of the spacecraft in its launch configuration – will be used during the first phase of testing in the VAB with the fully stacked SLS vehicle, and the agency brought in the OSA structural test article (STA) to KSC as an alternative to be stacked with the Orion simulator on the SLS for an upcoming modal test.

“The intent of using the OSA structural test article is to give those [cubesat] teams who are struggling to make our need date a little more schedule relief,” Pena explained. “If we were to use the OSA STA, that gives them probably over another month, maybe a month and a half before they start to become critical path to our Artemis 1 launch.”

“Right now, we are doing everything we need to do to [work] through that possibility, but we’re not going there yet. So the plan would be that the OSA STA could be used do some of the ITCO (Integrated Testing and Check-Out) testing in the VAB that requires the OSA STA and the Orion Mass Simulator and give those teams a little bit of an extended opportunity.”

Another scheduling factor for installing the cubesats in their dispensers in the flight article OSA is the contractor to do the work. “We’re also trying to have [the cubesats] arrive all around the same time because there’s an integration contractor that takes the cubesats and puts [them] into the dispenser, and that’s a contractor from California,” Pena said.

“We want to limit their time that they have to be here at KSC. We don’t want them sitting here at KSC for three months waiting on the cubesats to trickle in. So right now we’re trying to work towards a plan that has them all arriving at the same time, either in April or in May.”

(Lead image credit: Stephen Marr for NSF)

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