Road to EM-1: NASA outlines hardware milestones to SLS debut flight

by Chris Gebhardt

With approximately three years to go before the inaugural flight of the Space Launch System rocket, NASA has developed the integrated mission milestone processing flow for the EM-1 flight. The flow, which outlines all the necessary hardware processing milestones to a 2018 inaugural flight of SLS, helps solidify SLS’s path toward launch, including the pad processing timeline once the first SLS rocket is fully integrated.


Over the course of its development, the various components of what will be the SLS launch vehicle have taken shape and undergone testing across the United States and the European community.

But those tests and activities have revolved around single components of the SLS rocket as contractor agencies focused on development of their portion of the SLS vehicle while NASA itself has worked toward and through the Critical Design Review (CDR) – completed this year – to solidify the integrated version of the new Heavy Left Vehicle (HLV).

2015-11-11-163457With the CDR now complete, work to bring the constituent components of SLS together into the first integrated configuration of the vehicle begins in earnest, as flight production kicks into high gear this year with the build of flight hardware toward an aim of launching the first SLS mission – Exploration Mission 1 (EM-1) – in the late 2018 timeframe.

But even as SLS heads toward an integrated configuration, each of the major components of what will eventually be the HLV – as well as the ground hardware needed to support the massive rocket –  still have individual paths toward completion before they all converge at the Kennedy Space Center in Florida, inside the Vehicle Assembly Building (VAB), for stacking operations for EM-1.


According to the Integrated Mission Milestone Summary and associated L2 flow schedule information for EM-1 from the Exploration Systems Development (ESD) office, fabrication of the Launch Abort System (LAS) and ogive began in October 2015.

2015-11-11-152338Build-up of the Jettison Motor (JM) is slated to start in February 2016 followed by the start of production on the Attitude Control Motor (ACM) mass simulator in March 2016.

Construction of the Abort Motor (AM) mass simulator will follow in September 2016 as well.

After more than a year and a half of production, the JM will be delivered to the Kennedy Space Center in May 2017.

This will be followed by the deliveries of the ACM mass simulator to KSC in August 2017 and of the AM mass simulator to KSC in October 2017.

Finally, the LAS and ogive itself will be delivered to the Launch Abort System Facility (LASF) at KSC in February 2018.

Crew Module/Orion:

For the Crew Module (CM), also known as Orion, the first flight weld of the CM for the EM-1 mission occurred in September 2015, with primary structure completion slated for later this month.

By the end of January/beginning of February 2016, the CM structure will be completed at the Michoud Assembly Facility (MAF) in Louisiana.

It will then be delivered to the Operations & Checkout (O&C) building at the Kennedy Space Center (KSC) for outfitting tasks.

Following the CM’s delivery to the O&C, a pressurization proof test will be conducted in April 2016 followed by CM propellant proof leak testing in September 2016.

European Service Module:

Meanwhile, the European Space Agency (ESA) has been constructing the European Service Module (ESM) for the EM-1 flight at its Turino, Italy, facility.

2015-11-11-152711Structural assembly for the ESM was completed in September of this year ahead of transportation of the ESM STA to NASA’s Plum Brook facility in Sandusky, Ohio.

Pre-integration of all ESM components is expected to be completed by March 2016 before the ESM enters a prolonged series of tests, which are slated to wrap in January 2017.

After these tests, the entire ESM will be delivered to the O&C facility at the Kennedy Space Center in March 2017.

Command and Service Module:

Once the CM and ESM are together in the O&C building, the two will be mated together to form the Command and Service Module (CSM).

2015-11-11-152913Once this integration is complete, the CSM will be transported back to Plum Brook in Ohio for T-Vac testing.

Upon completion of that T-Vac testing, the CSM will be returned to the O&C in October 2017 before being handed over to ground operations in January 2018 and moved to the Multi-Payload Processing Facility (MPPF).

Following three months in the MPPF, the CSM will be taken to the LASF at the Kennedy Space Center in March 2018 where it will be mated to the LAS.

The combined LAS and CSM will then be moved to the Vehicle Assembly Building in April 2018 ahead of stacking operations with the SLS Core Stage and Interim Cryogenic Propulsion Stage (ICPS).

Interim Cryogenic Propulsion Stage:

With United Launch Alliance’s (ULA’s) ICPS Structural Test Article (STA) completed, ULA is slated to begin production of the first flight unit ICPS in January 2016.

2015-11-11-153038A new estimated completion date of the flight unit ICPS is January 2017.

Following completion at ULA’s Decatur, Alabama, facility, the ICPS will be shipped to the Kennedy Space Center in Florida where it will be handed off to ground operations in January 2018 and moved into the MPPF.

Following an approximate four month stay in the MPPF, the ICPS will be moved to the Vehicle Assembly Building in April 2018 for stacking and integration operations with the Core Stage of the SLS and the CMS/LAS.

Core Stage and Engines:

As MAF continues to work through acceptance of the Vertical Assembly Center, development testing for the Core Stage engines is slated to be completed by the end of the year, with the four flight engines for the EM-1 mission due for delivery to MAF between April and September 2016.

At MAF, manufacturing of the STA for the Core Stage is set to be completed by December 2016.

2015-09-30-153828This will be followed by assembly of the flight engine section in December 2016 and completion of assembly manufacturing of the flight intertank section of the Core Stage in January 2017.

The entire Core Stage assembly will then be joined together in late-February/early-March 2017 before the Core Stage is finished at MAF by August 2017.

At this point, the Core Stage will be transported in a one day trip by barge to the Stennis Space Center (SSC) in Mississippi where it will be hoisted onto the B2 test stand for a hot fire run at a date that is still to be determined.

Following completion of this hot fire test at SSC, the Core Stage will be loaded back onto the barge for the week-long trip around the Florida peninsula for delivery to the Kennedy Space Center and handoff to ground operations at the spaceport in January 2018.

The Core Stage will then be moved into the VAB where it will undergo acceptance and final checkout operations before mating operations to the twin Solid Rocket Boosters.


With the propellant void issue and the QM-1 (Qualification Motor -1) test behind them, Orbital ATK has begun production on the flight motor segments that will comprise the twin, five-segment Solid Rocket Boosters (SRBs) for SLS’s first mission.

Production on the flight motor segments began in July 2015 and will run through February/March 2017.

2015-10-09-213740While those flight motor segments are in production, Orbital ATK will conduct the final qualification test firing of the five-segment SRB, the QM-2 test, in March 2016.

Once flight motor segment build operations are complete at Orbital ATK’s Utah facility, the 10 propellant segments for SLS’s maiden flight SRBs will ship to the Kennedy Space Center in 2017 and 2018.

Under the current Integrated Mission Milestone Summary, the Forward and Center SRB segments will arrive at the Kennedy Space Center in September and October 2017.

This will be followed by the delivery of the Aft Skirts in November/December 2017 and then the Aft segments of the SRBs in late-January/early-February 2018.

Finally, the Forward segments are currently slated to arrive at the Kennedy Space Center in early March 2018.


But it isn’t just the various hardware elements of the SLS vehicle itself that are still undergoing preparations for the EM-1 mission.

All of the ground support structures at the Kennedy Space Center and Johnson Space Center are also progressing toward readiness for SLS’s inaugural flight.

2015-11-11-162709In October 2015, the Ground System Development and Operations (GSDO) team kicked off their own CDR for all of the ground support equipment and operations that will be needed to support the SLS Program.

That GSDO CDR is expected to run through December 2015.

At the Kennedy Space Center, structural modifications to the Mobile Launcher (ML) were completed in the autumn of 2015.

Moreover, the GSDO team will take the Spaceport Command and Control System (SCCS) version 3.0 for Hazardous Operations Control and Communication through validation operations by April 2016.

Version 4.0 of the SCCS will be verified and completed by March 2017.

2015-11-11-162807Prior to SCCS version 4.0, all VAB platform modification for SLS will be completed by December 2016 with Umbilical installation onto the ML accomplished by January 2017.

Following umbilical installation and VAB platform modification, the ML and VAB integration systems will be verified and validated by April 2017 with the VAB deemed “ready” for SLS operations by May 2017.

Just prior to VAB completion, pad 39B’s flame trench and deflector modifications will be completed in April 2017, with ML/Pad integration verification and validation operations wrapping in late-September/early-October 2017.

Pad 39B will be “ready” in January 2018 with the Mission Control Center at JSC “ready” in February 2018.

SLS stacking, integration, and pad ops:

With all of SLS’s constituent elements ready, NASA will realize something that hasn’t happened for the agency since 1979: the stacking and integration of a completely new launch vehicle inside the VAB.

Following the VAB stacking SAR/ORR (Safety Analysis Report/Operational Readiness Review) in July 2017, the ML will be moved into VAB High Bay 3 for final preparations for the commencement of stacking operations.

2015-11-11-163132Like Shuttle, stacking of the SLS vehicle will begin with the build-up of the SRBs.

In March 2018, approximately six months prior to the targeted lift off date, the SRB segments will begin moving to the VAB transfer aisle where they’ll be connected to cranes and lifted over the transom and stacked onto the ML surface.

This will mark the first time since 2011 that stacking operations for a launch vehicle have occurred inside the VAB.

According to the Integrating Mission Milestone Summary, stacking operations of the twin SRBs will last approximately two months, from the beginning of March to the end of April 2018.

*Grab your 2016 Calendar!*

Following SRB stacking, the HEO (Human Exploration and Operations) and Exploration Systems Development (ESD) divisions will convene their Integration Review to finalize all integration operations of the SLS.

2015-11-11-162855Once the HEO/ESD Integration Review is complete, the massive Core Stage will be lifted over the transom and lowered between the two SRBs – in a manner similar to how the External Tank was lowered between the SRBs during Space Shuttle stacking operations.

Core Stage mate to the SRBs and the ML’s umbilicals will occur in early-May 2018 prior to a late-May/early-June Partial Modal Test of the combined SRB-Core Stage launch vehicle propulsion elements.

This will be followed in mid-June 2018 by the mating of the ICPS and Orion on top of the Core Stage.

Once ICPS and Orion mating operations are complete, a Full Modal Test of the SLS integrated launch vehicle will occur in late-June.

Also occurring in late-June will be the Agency Flight Readiness Review (FRR).

2015-11-11-163214Following this Full Modal Test and the Agency FRR, SLS will spend the entire month of July inside the VAB undergoing integrated vehicle checkouts before conducting the first of two rollouts to launch pad 39B at the beginning of August.

Under the current Integrated Mission Milestone Summary, SLS will spend approximately one month at launch pad 39B undergoing a dry rehearsal test followed by a wet dress rehearsal to allow the launch teams to evaluate their countdown operations and validate pad and vehicle performance parameters prior to committing to the EM-1 launch campaign.

Following the wet dress rehearsal in mid- to late-August, the SLS vehicle will be returned to the VAB in late-August for final closeouts and ordnance installation operations.

2015-11-11-163349The performance of final closeout operations and Ordnance installation inside the VAB is a marked difference from Shuttle operations, where those operations took place during the often month-long stay at the pad.

Once closeout and Ordnance installation is complete, SLS will be rolled back out to pad 39B in September for a final, short volley of pad operations before launch on the EM-1 mission – currently slated “by November 2018”.

Assuming a September 2018 launch, the Post Flight Assessment and Review of the EM-1 mission will occur in December 2018, followed by Post Flight Crew Module Transport and Deservicing in January 2019.

(Images: Via Philip Sloss, NASA and L2 – including SLS renders from L2 artist Nathan Koga – The full gallery of Nathan’s (SpaceX Dragon to MCT, SLS, Commercial Crew and more) L2 images can be *found here*)

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