NASA makes great strides as SLS milestones converge for debut flight

by Chris Gebhardt & Chris Bergin

NASA’s Space Launch System (SLS) rocket is progressing through several critical construction milestones in the final part of 2015.  As various aspects of the SLS Program converge, the massive Heavily Lift Rocket is making impressive strides toward a debut flight in November 2018.

Status of SLS build operations:

Around the country, numerous elements of the SLS Program have produced very public and necessary tests and construction milestones for the rocket that will soon ferry astronauts to beyond Low Earth Orbit destinations.

While a great deal of NASA’s internal progress over the summer focused on the finalization of the rocket’s technical and engineering specifications, the agency’s various centers proceeded toward critical end-of-year build  and test operations on various Structural Test Articles (STAs) and flight hardware elements for SLS.

2015-09-30-153828To this end, at the Michoud Assembly Facility (MAF), work on alignment issues with the Vertical Assembly Center (VAC), which required work to remedy, has all but been completed.

The VAC – the machine that will weld the massive core LH2 and LOX tanks for SLS – is a critical ground processing aspect of SLS production and represents a major advancement in tank welding technique and process than that employed during the Space Shuttle Program.

Presently, SLS Near-Term Look-Ahead schedules show that the VAC will be turned over from the construction contractor ESAB to Boeing at the end of this week on 31 October.

2015-09-30-154210Once Boeing – the company contracted to build the LH2 and LO2 tanks for SLS’s core stage – takes possession of the VAC hardware, the aerospace company will proceed with the build of the LOX tank Confidence Article.

This LOX Confidence Article will provide Boeing and NASA with critical information on how the new welding machine performs against predicted and needed parameters for the LOX tank portion of SLS’s core stage.

While the Confidence Article Build schedule is still currently labeled as “under review”, the SLS Near-Term Look-Ahead from 19 October places the start date of LOX Confidence Article build on 2 December.

The build is slated to take approximately 16 days and is expected to wrap on 18 December if the build goes according to plan.

*Click here for more SLS News Articles*

After that, Boeing will proceed with the LH2 Confidence Article Build on 21 December. Given the year-end holidays, that LH2 Confidence Article Build will wrap on 12 January.

2015-10-26-193657Additionally, United Launch Alliance (ULA) – contracted to build the ICPS (Interim Cryogenic Propulsion System) – has just completed construction of the ICPS Structural Test Article (STA).

ULA will then begin constructing the ICPS Flight Unit 1 LH2 tank on 11 January 2016. Completion of the ICPS Flight Unit 1 is scheduled for 16 July 2016.

Furthermore, the next test firing of the SLS core stage engines is set for no earlier than 27 January 2016 – which will, along with all other work, move SLS toward its debut launch on the EM-1 (Exploration Mission 1) flight in November 2018.

SLS and the long road through Critical Design Review:

This construction follows from the agency’s crucial Critical Design Review (CDR) for SLS.

2015-10-26-193751The CDR – consisting of approximately 60,000 pages of documentation comprising more than 150 GB of data – took place at NASA’s Marshall Space Flight Center (MSFC) after each major element of the rocket passed its own specific review process and the rocket itself passed its Preliminary Design Review (PDR).

For spaceflight, a CDR – especially in the arena of human spaceflight – confirms that a launch vehicle performs within the limits of human flight operations.

In this case, the CDR for SLS took NASA through a multi-disciplined technical review to ensure that SLS could proceed into fabrication, demonstration, and testing and meet all stated performance requirements within cost, schedule, and risk.

SLS’s CDR occurred over 11 weeks and involved the SLS Program as well as a separate review by the Standing Review Board, comprised of experts from NASA and industry who were independent of the SLS Program.

“We’ve nailed down the design of SLS, we’ve successfully completed the first round of testing of the rocket’s engines and boosters, and all the major components for the first flight are now in production,” said Bill Hill, deputy associate administrator of NASA’s Exploration Systems Development Division.

“There have been challenges, and there will be more ahead, but this review gives us confidence that we are on the right track for the first flight of SLS and using it to extend permanent human presence into deep space.”

“This is a major step in the design and readiness of SLS,” said John Honeycutt, SLS program manager.

“Our team has worked extremely hard, and we are moving forward with building this rocket. We are qualifying hardware, building structural test articles, and making real progress.”

SLS: A tale of core stage color

Of particular public relations note for the completion of the CDR came the never-questioned switch of NASA’s public imaging of SLS away from the painted core to what was always understood inside and outside of the agency to be SLS’s true configuration: an unpainted, burnt orange core stage.

When SLS was first unveiled on 14 September 2011, NASA’s public affairs office made a concerted effort to visually distance the vehicle from the proposed Ares rocket architecture of the 2009-canceled Constellation Program.

2015-05-15-202910It was always understood by all involved that SLS would never fly with a painted core stage and that the visual color scheme of the rocket would be drastically different from what NASA was portraying it to be.

In fact, NASA’s own “internal only” documentation prior to the CDR showed SLS in its true, unpainted configuration.

(Image left –Nathan Koga L2 Rendering, based on image right showing official NASA documented SLS).

And this, taken strictly from an engineering standpoint, makes logical sense.

Applying thousands of pounds of white paint to the core stage of SLS would have drastically reduced the vehicle’s payload-to-orbit capability because for every pound of paint applied, a pound of payload delivery ability would have been removed from SLS’s capability.

2015-10-26-195936However, NASA’s official press release announcing the completion of the CDR implies that NASA engineers only decided during the CDR – during discussions about the rocket’s technical and engineering systems – not to paint SLS’s core stage.

Regardless, NASA is finally and publicly showing SLS in her correct configuration and color scheme with which she will launch in just three years time.

The post-CDR design does include more foam on the top end of the rocket after an additional decision included a call for the LVSA (Launch Vehicle to Stage Adaptor) to have foam on the outside, based on the latest thermal analysis.

Given the LVSA has the core stage LOX tank below it, the ICPS LOX tank inside, and the ICPS LH2 tank above it, it is expected this area of the rocket will become cold during the final countdown and form ice on the outside.

(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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