A top level overview at NASA’s Advisory Council (NAC) has shown most of the Space Launch System (SLS) and Orion spacecraft flows are on track for a 2018 launch of Exploration Mission -1 (EM-1). However, engineers are continuing to battle against critical path issues with the European Service Module and flight software.
Path to EM-1:
The debut launch of SLS is shooting for a window that opens in September and ends in November in 2018.
“We’re not dwelling too much on the schedule (as we’re) still working the analysis effort right now,” noted Exploration Systems Development (ESD) Deputy Associate Administrator Bill Hill in his presentation of the EM-1 current status to the NAC.
“We’re working scenarios on when things may be late, but the preliminary analysis still shows we can make the launch window through November ’18 and we’re still working towards that.”
Multiple program elements, companies and even countries are involved in the complex ballet of flows that will result in the SLS and Orion stack rolling out to Pad 39B in time to make that window.
While most of the hardware and ground systems are making good progress towards that milestone, the brains of the SLS/Orion stack that will depart from the Kennedy Space Center (KSC) are struggling to meet the required schedule.
Notably, the NAC’s schedule chart classes SLS’ software as on schedule, whereas Orion’s software is shown to be the second major critical path threat to the EM-1 launch window. However, the NAC document expands on the issue and classifies the problem as “integrated”.
The NAC was told that the Flight Software has passed through the 26A and 26B loads, with 85 percent of EM-1 software complete after 26B release. A plan for a 26B patch is on schedule for later this month. The 27A load is scheduled for mid-January, to be followed by the 27B load in mid-April.
Eventually, the software will undergo a major “power on” test run in the Integrated Test Lab (ITL) in Denver – which is shown to be the final step in the schedule. The final software release is shown to be March 2018.
SLS’ final software certification is shown to be later that year, right up to the point SLS will be first rolled out for a test roll to Pad 39B, yet this is not shown as a critical path.
“Concern: Integrated avionics and software verification and validation (V&V): Integrated Test Lab capacity, software delivery status, agile software development process productively metrics and cross-program interdependencies for emulators and design functionality,” noted the NAC overview presentation.
“Current Status: Cross-program dependencies are mapped and content migration is being monitored as both Orion and SLS have deferred some content to subsequent builds. Impacts due to late ESM avionics box delivery also being evaluated.”
The reference to the ESM (or European Service Module) is also notable, given that is classed as a red line primary critical path for the entire EM-1 flow to launch.
As previously reported, NASA has set up a working group to try and get the ESM off the critical path, a path that requires the flight unit finish construction in Germany.
The path calls for the ESM to be shipped to the United States and housed in the O&C Building for mating operations with the Orion spacecraft next April.
“ESA post-CDR (Critical Design Review) check point complete with agreement to forward work to prepare for EM-1 and EM-2,” added the NAC overview on the status. “ESM is now been outfitting in Bremen clean room. ESM delivery in April 2017 is the critical path.”
A report from Germany claims both the CDR 2 Closure TIM (Technical Interchange Meeting) and “CDR 2 Board” were completed last month “with forward work”. The latest picture of the flight ESM show it only to be an empty structure.
“We’ve finished the CDR but prop tank installation (is something) we’ll look at again in February. We do have some challenges with the vendor there, but we’re working our way through that,” added Mr. Hill – who mentioned a potential option is to install fewer tanks on the ESM.
The NASA manager added they have a “fighting chance” of making the April delivery date.
The structural test version of the European Service Module – having arrived in the United States for a series of tests at NASA’s Glenn Research Center’s Space Power Facility in Sandusky, Ohio – is currently undergoing pyro shock testing, following the completion of shaker testing.
Early in 2017 will be the rush period, as engineers in the Bremen clean room work to install the propellant tanks in February, followed by Functional Tests in April 2017, before shipping the ESM to KSC later that month.
Mr. Hill admitted they are “struggling” with the propellant tanks on the associated NAC telecon.
The SLS Core Stage is shown to be on a “Tertiary Critical Path”, mainly related to issues found with the friction welds on the test article LOX tank. The huge stage is set to depart the Michoud Assembly Facility (MAF) next Summer for the major event of a Green Run firing at the Stennis Space Center (SSC).
However, the overall SLS schedule is shown to be making good progress towards the launch date.
The Mobile Launcher (ML) is also now making good progress, partly in thanks to engineers working six days a week on the structure and the array of umbilicals that will be used to host SLS in the VAB and on the pad.
Should all the flows come together, SLS will roll to 39B in the June to July timeframe in 2018 for a major rollout test that will include a Wet Dress Rehearsal (WDR) at the pad. However, Mr. Hill added the Flight Readiness Firing has since been deleted from the schedule path.
The stack will then be rolled back into the Vehicle Assembly Building (VAB) prior to the Launch Readiness Review (LRR) for EM-1, which will provide the green light to rollout for the historic launch within the September to November launch window.
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