NASA moves to enforce early switch to EUS for SLS

by Chris Bergin

NASA managers have placed a “stop work order” in relation to the human-rating of the Interim Cryogenic Propulsion Stage (lCPS) for the Space Launch System (SLS). The stage, which was set to ride with a crewed flight on Exploration Mission -2 (EM-2), will be replaced by the early addition of the more powerful Exploration Upper Stage, although NASA recently claimed the proposed FY 2017 funding cuts to SLS place its implementation schedule in doubt.

SLS Trying To Find A Path:

The Space Launch System continues to enjoy a relatively smooth developmental path, especially when compared to its predecessor Constellation Program (CxP).

Schedule slips and technical issues continually plagued the Ares-based architecture, although engineers cite funding issues were also a major impact on their efforts.

2016-02-15-165801The early plan for the Constellation Program involved a Moon First approach, a stepping stone to Mars on the “Vision for Space Exploration” (VSE) path.

The VSE’s “Moon, Mars and Beyond” manifest – produced in 2006 (available in L2) – showed the program that would have already been deep into providing crew rotation mission to the International Space Station (ISS) by 2016 – three years away from a return of crewed missions to the surface of the Moon – via the combination of Ares I, Orion, Ares V and the Altair lunar lander.

As per most rocket development schedules, slips to early manifest plans are almost a certainty – as eventually realized via the aforementioned CxP issues in the years that followed the 2006 plan.

SLS has suffered far less by way of schedule slips. The very early political will was to debut the monster rocket in 2016, prior to solidifying to a 2017 target. EM-1 is currently expected to take place in 2018, a slip that is far less dramatic when compared to CxP’s woes.

The main issue for SLS is her lack of missions. The early CxP plan had a wide range of flights on its planned schedule, whereas SLS lacks any real definition past the soundbites and hashtags provided by NASA.

This has also led to concerns about the rocket’s flight rate, in part due to the lack of confirmed payloads that are yet to make it past the paperwork stage of Design Reference Missions (DRMs).

One element of the rocket that may boost SLS’ range of missions is the powerful Exploration Upper Stage (EUS).

2016-02-15-221911The initial plan was to switch to this new upper stage after the crewed EM-2 mission. However, as previously reported by this site, NASA wishes to advance this plan.

The debut of SLS will be known as the “Block 1”, sporting a Delta Cryogenic Second Stage (DCSS), renamed the Interim Cryogenic Propulsion System (ICPS) for SLS.

As noted in numerous meetings – not least by NASA’s Aerospace Safety Advisory Panel (ASAP) – it would cost around $150m to “human rate” this stage ahead of EM-2, a cost that would be associated with just the single use of the stage ahead of moving to the EUS.

2016-02-15-221200The switch to EUS after the first test flight of SLS would allow for the rocket to enter its workhorse configuration that will be capable of a full mission range envisioned throughout the 2020s.

According to NASA documentation acquired by L2, NASA is eyeing the immediate push to the workhorse Block 1B configuration after EM-1, “a configuration that allows for the use of the Universal Stage Adapter (USA) capable of co-manifesting up to 10 metric tons of payload along with the Orion vehicle on a trans-lunar trajectory.”

The SLS program completed the Systems Requirements Review (SRR) for the EUS in January 2015, which sets forth the Point Of Departure (POD) of the Block 1B configuration to be used starting with EM-2.

Z3Per the EUS POD, the definition calls for the stage to untilize four RL-1OC-3 engines (EUSEs).

The documentation was released internally throughout the SLS Program to call for a stop order on all work associated with the ICPS after EM-1.

“The Deputy Associate Administrator (DAA) for Exploration Systems Development (ESD) directs the
following to all ESD programs and offices: The ESD architecture baseline is changed to implement a human-rated Block 1B crewed configuration of SLS starting with the EM-2 launch.

“Work will continue as planned using SLS Block 1 (with ICPS) for the uncrewed EM-1 flight. Any work associated with human-rating ICPS and using SLS Block 1 with ICPS beyond EM-1 will be stopped. The effort to prepare ICPS for EM-1, and any work to date associated with human rating ICPS, is valuable and will be archived per Agency policy.”

2016-02-15-215756Moving to the EUS for the second flight of the SLS will involve additional challenges, such as large changes to the top of the SLS Mobile Launcher, which will need to cater for the larger EUS in the SLS stack.

“With this change, there will be some interface differences between SLS Block 1B and Orion that will
continue to be worked through normal enterprise integration processes,” added the documentation.

“GSDO (Ground Systems Development and Operations) will be required to make substantial infrastructure and interface updates to accommodate Block 1B requirements; these updates to GSDO are not backwards-compatible to Block 1.”

One potential problem to NASA’s plan was the recent announcement of the NASA FY 2017 Budget Request, which removed a huge amount of funding from SLS and Orion.

2015-06-30-132927The EUS recieved a specific reference from NASA Chief Financial Officer David Radzanowski in comments made to the media after the announcement, citing that the reduced funding could impact on implementing the EUS on the second flight of SLS.

However, as is usual, SLS’ political allies in Congress are likely to return a large amount of funding to SLS and Orion’s budget lines, removing the concern of EUS’ early installation.

As such, NASA will press on with its plan to implement EUS into the second flight of SLS, with a forward plan already outlined.

“ESD will update the Level 1 Requirements, Concept of Operations (ConOps), Integrated Design Definition Document (IDDD), Flight Test, and any other necessary documentation to reflect the above, which will flow to program baselines,” added the documentation associated with the ICPS stop work order.

“Programs will immediately implement any necessary planning and effort in accordance with this decision memo.”

Images: NASA and L2 – including 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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