Crewed Orion spacecraft passes critical design review

by Philip Sloss

In early December, NASA’s Orion Program completed a “Delta” Critical Design Review (CDR) of the crewed spacecraft configuration that will first fly on Exploration Mission-2 (EM-2). This CDR focused on the changes between the uncrewed spacecraft configuration that will fly on Exploration Mission-1 (EM-1) and EM-2.

The CDR looked at the progress of designs for new or significantly modified Orion systems for EM-2. CDR Reviews began in September and culminated in a board meeting on December 3.

NASA, the European Space Agency (ESA), and their U.S. and European prime contractors are looking at the Orion EM-2 schedule, which currently targets launch of a four-person crew in the second half of 2022 on a lunar flyby test flight.

Delta CDR board on December 3

“The vehicle came through very well on this CDR,” Kirasich said. “This CDR was focused on the differences between EM-1 and EM-2, which primarily is in two areas. The ECLSS, the Environmental Control and Life Support System, and the crew displays.”

“Those two systems came through very clean, very few problems because predominantly the teams — even though we don’t fly them on EM-1 — we’ve been working them hard offline in labs and risk reduction development testing,” he added.

High-level overview of Orion from a NASA presentation. Credit: NASA.

“The EM-2 CDR was intended to demonstrate the design maturity of EM-2 first use, or substantially modified hardware and software systems since the [EM-1] CDR,” Kirasich said in a follow-up email statement. “Conducted primarily in the fall of 2018, it included eight Subsystem Design Reviews (SSDRs) and four Management Review Team (MRT)/Targeted Review Team (TRT) reviews and a Face-to-Face (F2F) meeting regarding the European Service Module (ESM).”

“This is comparable to the eight SSDRs, six MRT/TRT reviews, and ESM F2F held in support of the [EM-1] CDR in 2015.”

The overall Delta CDR started in September. “The way it works is you will start out with component reviews, ” Kirasich explained.

“I’ll give you an example, there will be a fan, we’ve got to have a critical design review on the fan. Then you have subsystem reviews which is the ECLSS, when you look at the fan with the mixing valve with the diffuser, how does this ECLSS system work?”

“So you have a system-level (review),” he added. “And then we have integrated vehicle reviews that look across systems.”

Kirasich noted that this CDR was not intended to cover systems that haven’t changed. “We didn’t go back and have another CDR on the crew module RCS (Reaction Control System) prop thruster, right? Because we’re flying that on EM-1 and that hasn’t changed,” he said.

“But what we do have to do is, because we’re adding these new systems, they take power, they add mass to the vehicle, they add a heat load to the vehicle,” he explained. “So we have to go across the entire vehicle and we have these integration reviews where we look at, well now that we’ve added these three new fans, ‘[for] the vehicle weight do how much did it go up?’ ‘How much additional power did it consume?'”

“So we do cross-cutting reviews, as well, and then during all these reviews when you find something you will say ‘this does not meet a requirement’ or ‘this does not meet one of the goals of the CDR’ you write something called an RFA (request for action), which then is a piece of paper that the program goes off and works,” Kirasich said.

Orion EM-2 pressure vessel in the “birdcage” tool in the Operations and Checkout Building at KSC in November. The remainder of the crew module structural elements are being added to the pressure vessel in the tool. Credit: NASA/Rad Sinyak.

“We left the review with a total of 206 RFAs, so we accepted 206 RFAs during the review,” he added. “During the process from September until we had our board in early December we closed 37 of the RFAs just while we doing the review itself, so we left the review with 169 RFAs that we’ll then go off [and] work and regroup in late May to make sure we’ve closed all the actions out.”

“To put that into context for you, I don’t have the exact number but when we did our first Critical Design Review for the EM-1 vehicle we had over a thousand RFAs,” Kirasich noted. “So you can see, the statistics kind of bear it out too, that the vehicle is coming together — smaller number of final things we need to work off to be ready to go into final assembly and testing.”

EM-2 configuration changes

The Orion Crew Module flew on the Exploration Flight Test-1 (EFT-1) mission with mass simulators for the rest of the spacecraft and without crew-support systems like ECLSS elements. Exploration Mission-1 (EM-1), currently forecast for launch in the second half of 2020, adds the Crew Module Adapter (CMA) and European Service Module (ESM) elements that provide power, supplies, and propulsion for the spacecraft to fly independently for the first time on a long-duration mission to cislunar space.

EM-2 adds all the equipment and additional supplies to support a four-person crew up to a twenty-one day independent mission. This includes supplies of oxygen and nitrogen gas predominantly stored in the ESM and systems to manage their mixture for the basic cabin atmosphere in the Crew Module (CM).

Presentation figure showing basic layout of fully outfitted crew module, which will fly for the first time on EM-2. Credit: NASA.

Another system in the CM filters carbon dioxide from the crew out of the atmosphere. The EM-2 vehicle design also adds the computer displays and controls to the CM for the crew to be able to monitor and operate the vehicle.

The EM-2 CM will also have a galley for food preparation and a toilet. There will additionally be storage room for food supplies and other crew equipment.

The second ESA Service Module that will fly on EM-2 will be largely the same as the first flight module which is being integrated with the CMA at the Kennedy Space Center (KSC) in Florida for EM-1, but prime contractor Airbus Defence and Space will be making some modifications while shaving down the overall mass of the module.

Kirasich noted one such change is to the solar array drive mechanism. “We’re making a change to it from EM-1 to increase the amount of current that can be applied to the motors essentially to give it a stronger hold and rotational capability,” he said.

“So we’re changing some parameters inside the FPGA (Field Programmable Gate Array) to have more torque and more margins in our solar array operations for EM-2.”

Graphic showing the canting angle extremes of the solar array wings (SAW) on the ESM. The drive electronics for the solar arrays are being upgraded with the EM-2 vehicle for future rendezvous and docking missions. Credit: NASA.

Nujoud Merancy, NASA Exploration Mission Analysis Lead, elaborated further: “You have the inner gimbal, so that is the shoulder joint that moves the array forward and aft, it has enough torque and resistance to handle a lot of what’s going on on EM-1 but then when we looked at EM-3 and beyond really for the rendezvous we end up having to park it a lot because of all the burns,” she said. “To get through a rendezvous there’s a lot of burns as you approach another vehicle.”

“The combination of the need to park it which takes away from power production and then move it so you can get power and then stop it again for burns, it’s a really good improvement to the overall system operability to just make that gimbal a little bit stronger so that you can keep it tracking through more of the burns,” she explained.

Another forward looking change is to repoint of some of the RCS thrusters to help with Orion attitude control when maneuvering while docked with a module that it is delivering to the future cislunar gateway. “Realigning the RCS is not a major change,” Merancy noted.

“But those aft RCS that are out at a ’45’ [degree angle] right now on the pitch and yaw axes if you point them into the pure pitch direction we’ll have more control authority for rendezvous and docking with the co-manifest payload,” she explained.

A third change adds some redundancy to the ESM propellant system, which adds value when crews start flying on Orion. “The prop system has to be pressurized with upstream helium tanks and right now those two helium systems upstream are independent of each other,” Merancy noted.

“The idea is that if you add a crossfeed so you can feed from one helium tank to another, if you have a blockage or a leaky valve downstream from one tank you could still retain the performance of that helium by crossfeeding it into the other one,” she said.

“It’s not something you would nominally use, but it’s something that would improve reliability for a contingency.”

A recently noted change for the EM-2 CMA is incorporating lessons learned from assembly of the EM-1 flight structure.

“There’s an inner ring that is, if you will the inner structural article that essentially provides the inner structural member,” Kirasich explained. “For EM-1, we had designed that out of six different pieces, you might imagine six different sixty-degree pieces.”

“The challenge we had on EM-1 was during assembly in the O&C (Operations and Checkout) Building in Florida. We would hang these parts in the tool, so there’s an inner ring, there’s upper panels, there’s lower panels, and there’s an outer ring and all these things came in pieces.”

“We had alignment issues, not only between the parts that had to mate between [the panels and the rings] but also with each other,” he noted. “So what we did in an attempt to improve manufacturability was instead of these six sixty-degree inner wall panels, we are going to have a single 360-degree inner wall.”

“We start with a single piece of aluminum, it’s a forging and we send it to a machine shop that machines out of a single piece instead of six different pieces.”

EM-2 Orion hardware status

The EM-2 Orion spacecraft elements are largely still in structural assembly. The completed Crew Module pressure vessel was delivered to the O&C Building at KSC in late August, where Orion prime contractor Lockheed Martin assembles the Crew Module and CMA and performs final spacecraft assembly.

The CM pressure vessel is currently being outfitted with other structural elements in the birdcage stand. The inner ring/inner wall of the CMA structure is expected to be shipped to KSC soon.

“It’s being machined for Lockheed Martin by a company called Ingersoll in Rockford, Illinois, and the reason I know this is because whenever we do something like this that is a primary structural component, it’s a pretty big deal and we worry about it so we watch it very closely,” Kirasich said. “We are really close [to completion]. They’ve actually done a tremendous job.”

The partially-outfitted structure for ESM Flight Model-2 (FM-2), which is slated for the EM-2 mission, is moved into the integration stand at the Airbus assembly, integration, and testing facility in Bremen in late November. Credit: Airbus Defence and Space.

“Then when Ingersoll is done it goes to a finishing shop where they put a primer on it and it’ll be at the Cape in January, so we’re about done with that inner ring and then it’ll be down at the Cape installed in that tool and we’re going to see if this did indeed improve our manufacturability.”

Assembly, integration, and testing (AIT) of the second ESM, Flight Model-2 (FM-2), continues at ESM prime contractor Airbus Defence and Space’s AIT facility in Bremen, Germany. With shipment of Flight Model-1 from Bremen in early November, FM-2 took its place in the integration stand in early December.

At the time of the ESM FM-1 arrival in Florida in November, Airbus was forecasting completion of FM-2 in the first quarter of 2020.

Removing iron bars

The overall assessment of the EM-2 launch date target is currently September, 2022, with the different Exploration programs (Exploration Ground Systems, Orion, Space Launch System) looking at schedules for EM-1 and EM-2 dependencies on that first integrated flight.

Funding for a second Mobile Launcher (ML) set in motion a series of updates and changes to the EM-2 mission and its launch date. Prior to the changes, there was a 33-month “iron bar” in the schedule between EM-1 and EM-2 to modify the first ML for a new Space Launch System (SLS) upper stage.

With the EM-2 test flight moved back to the first, interim SLS upper stage, the target launch date could be made somewhat independent of when EM-1 finally launches and forecast date moved from 2023 back into 2022. But there are still some dependencies EM-2 has for when EM-1 launches, such as reuse of Orion avionics boxes.

Long-term Orion program planning chart from early 2018 showing the “avionics refurb” from EM-1 to EM-2 (top middle). With the EM-1 launch date moving into the second half of 2020, the program is buying a second set of core avionics earlier than planned to maintain EM-2 schedule margin. Credit: NASA.

While the forecast date for EM-2 improved with the move back to the SLS Block 1 configuration, the forecast for the EM-1 launch date has continued to slide which has shrunk the estimated time between launches. “So when EM-1 slipped, it reached the point where the time to pull the boxes out of EM-1 and insert them into the EM-2 crew module and test them, that was starting to drive the EM-2 launch date,” Kirasich noted.

NASA is trying to advance the target date for the EM-2 launch closer to the mid-2022, and the Orion Program is looking at ways to optimize the schedule for assembly, integration, and testing of the EM-2 vehicle for launch. To reduce the dependence of EM-2 Orion vehicle processing on when EM-1 flies, they looked at advancing the purchase and assembly of the set of EM-3 avionics.

The original plan was to build the second full set of crew module avionics with construction of the EM-3 spacecraft that will fly after EM-2. “Once we get done with DDT&E (Design, Development, Test and Evaluation) we want to fly once a year and we’re trying to do it very economically and efficient, so we’re trying to reuse as many components from flight to flight as we can,” Kirasich explained.

“Almost like Shuttle did — you know in the Shuttle every orbiter we had one set of avionics, and unless something broke you reflew the avionics all the time,” he continued. “So the intent when we get into routine operations is we’re going to have three primary structures and three sets of avionics that fly together all the time, that’s our goal.”

“We looked at how much funding that would take to accelerate those EM-3 boxes and then we all said ‘boy that would take money away from all other things on EM-2, do I need to buy all [of them] or can I buy a subset?’,” Kirasich said.

It turned out that accelerating only the Orion Core avionics would allow much of the EM-2 Orion integration and checkout to continue independently of EM-1. “The Core consists of the computers, the VMCs (Vehicle Management Computers), and the PDUs (Power Data Units), and actually one or two other boxes which are called media converters,” he explained.

Gary Cox, NASA Orion Avionics Power and Wiring Manager, said in an email that the number of avionics boxes in the core set is 11, leaving 15 boxes that will be re-used from EM-1 to EM-2.

“So we’re able to have new boxes, we’re going to put them in, that allows us to turn the vehicle on for the first time on schedule, if you will, without being affected by EM-1,” Kirasich said. “Now let’s go back to our earlier conversation about ECLSS and crew displays. We have new avionics boxes showing up for the first time, the ECLSS controllers and the crew displays.”

Development version of the Orion crew displays as seen at Johnson Space Center in April, 2018. Credit: Philip Sloss for NSF/L2.

“They will be able to get plugged in early, so we will be able to do the first vehicle power on and we will also be able to do the first vehicle checkouts of the new components, the ECLSS controllers and the crew displays, completely independent of when EM-1 flies,” he noted.

“So for approximately half the price of accelerating the whole EM-3 [avionics set], that allowed us to decouple EM-1 from EM-2, it bought us well over six months of decoupling,” Kirasich added.

In terms of the Orion EM-2 vehicle schedule, Kirasich said his bosses are asking the Exploration programs if they can advance the launch date. “[They] have asked us to try and pull it back to June and we’re working very hard at that action they’ve given us,” he said.

“I am going to be able to pull it back, I’ll be able to do better than September. I don’t know if I’ll be able to get all the way back to June but that’s what I’m working on.”

Related Articles