Boeing complete SLS Pathfinder Tank as MAF ET operations end

by Chris Bergin

While the political side of the Space Launch System (SLS) continues to be bogged down by delays and arguments, the engineering side of the vehicle is picking up, most notably on the core stage. With Boeing’s “Pathfinder” tank completed ahead of schedule, External Tank tooling is being unwrapped for checks, ironically as ET operations officially ended at the Michoud Assembly Facility (MAF).

SLS Work:

August has been a relatively busy month for SLS, with NASA centers and contractors almost ignoring the delaying tactics in Washington DC, by pushing on with planning work surrounding the winning configuration of the Heavy Lift Launch Vehicle (HLV) – as much as NASA’s top brass continue to avoid announcing it.

At the Marshall Space Flight Center (MSFC), the new SLS DAC (Design Analysis Cycle) cycle officially started this month, a process which will take the vehicle design to the SRR (System Requirements Review)/Checkpoint Review in October.

Managers have already presented their teams with kickoff charts, showing what is now the well-known Shuttle Derived (SD) HLV, along with pointers towards a forward plan to develop the Upper Stage design simultaneously with the core stage.

While no Upper Stage hardware will be built at this stage, given the lack of funding, the current process of developing the US with the Core will provide an engineering advantage, given the integrated vehicle loads can be developed in a way which will allow the Core Stage to be designed for the appropriate Upper Stage from the outset.

With SLS concept development providing support of the SRR/SDR (System Design Review) and core stage procurement activities, the path is laid out for the SLS to progress to the PDR (Preliminary Design Review) stage. Once the core stage prime contract is awarded, the work will transition to more of an insight and vehicle integration role.

Boeing – who officially class themselves as “pursuing work on NASA’s Space Launch System to provide heavy lift capability for exploration beyond Low Earth Orbit” – have already completed testing their manufacturing processes via a sub-scale tank, known as the “Pathfinder”.

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The Boeing team at MAF in New Orleans, class the Pathfinder as a “major milestone toward the future of space exploration”, adding the tank is a “key demonstration of NASA’s readiness to immediately transition into the Space Launch Systems (SLS) program”.

The Pathfinder Liquid Oxygen tank is a 5.5 meter diameter lightweight aluminum lithium design, demonstrating state of the art manufacturing and welding approaches developed as part of the Upper Stage Production Contract (USPC), allowing engineers to work on a 5.5m tank – per development on Ares I’s Upper Stage – via technologies and techniques will be applied to the 8.4m diameter SLS.

“State of the art production tools, developed by Boeing in partnership with NASA and the University of New Orleans National Center for Advanced Manufacturing, provided efficiencies not previously available at MAF for this type of manufacturing. The pathfinder is also representative of a Liquid Oxygen tank that is extensible to the Space Launch System,” noted a Boeing overview (available on L2).

“The use of a Liquid Oxygen tank originally designed for Upper Stage Production Contract enables an efficient transition of subsystems such as the Main Propulsion System and Thrust Vector Control from USPC to Space Launch Systems.

“Work on the Space Launch Systems enables Boeing to expand into a natural adjacency, leveraging decades of experience in manned space flight into possible future business.”

Interestingly, further evaluations have recently begun into the MPS which will ride with SLS, with the potential for the three retired Shuttle orbiters to donate their MPS’ for the opening three flights. (Another article will follow on this evaluation next week).

The lightweight aluminum-lithium design features a spun-formed dome, a gore panel dome, and a barrel welded together with two circumferential self-reacting welds. The team managed to complete the fabrication six weeks ahead of schedule.

“Preparing the Pathfinder for production (was) a major step toward production of the nation’s next generation human-rated launch systems,” said Steve Ernst, Boeing’s Exploration Launch Systems Manufacturing Development leader on the Boeing information

“The completed work is a balance between safety, reliability and cost forged by an innovative NASA-Boeing partnership that is paving the way for SLS.”

The information also notes how Boeing worked with NASA’s MSFC in developing the manufacturing processes, in order to prepare the Boeing engineers and technicians with the skills and techniques necessary to employ state of the art techniques for safe, reliable, and cost efficient production of future launch vehicles.

“(This was a) significant advancement of MAF activation by completing key training and certifications for task leaders and weld operators; establishing detailed approaches and processes for kitting, staging, and shipping and receiving; and emphasizing a significant focus on a healthy safety culture and process with the completion of job hazard analyses and lift plans.”

Boeing also confirmed that in order “to support Congressional direction to NASA for development of the Space Launch Systems”, Boeing prioritized work in its existing USPC and Instrument Unit Avionics contracts to work on items that advanced the technical baseline of technologies and manufacturing approaches for the new Heavy Lift Launch system.

“We recognized that we needed to identify opportunities to earn value for NASA and reduce risks associated with the transition to SLS,” added Rick Navarro, Boeing Michoud Site director.

“Working with NASA, this vision resulted in developing the concept to manufacture the Pathfinder tank which not only enabled the team to demonstrate technologies extensible to SLS, it also focused the team on establishing the necessary Boeing production infrastructure at Michoud to prepare for SLS production.

“As a result, the team at Michoud found a way to start up operations and begin a functional production system.”

Boeing teams at the Kennedy Space Center also assisted the MAF Boeing team in establishing the necessary stock of production supplies for the production of the Pathfinder, while the the team at Boeing’s Huntington Beach operations played a key role in development and fabrication of tooling that was used for the Pathfinder.

Other Boeing sites such as San Antonio, Heath, and Charleston also assisted in defining and obtaining the necessary infrastructure to monitor production activities. A number of suppliers, stretching from the northeast United States to the west coast, also supported the Pathfinder effort.

The Pathfinder milestone comes at a time of painful transition for MAF, with WARN notices – extended several times in the hope NASA would finally push forward with its SLS contract awards – finally activated, resulting in the official end to ET operations at the facility.

Just a handful of ET engineers will remain at MAF after Friday, with the rest of what is now a small workforce working on Orion and other contracts.

The official end of ET work at MAF has resulted in the spare tanks – such as ET-94 – no longer being serviced by Lockheed Martin. They have been turned over to the ownership of Jacobs Technologies.

It is unknown what Jacobs will do with the ET hardware. However, their MSFOC group has begun unwrapping ET “major weld” tooling, placed into storage after the final ET was constructed.

These tools are the 5018 and 5019 (LO2 Weld and LH2 Weld) machines – which have been in preservation for a couple of years – and are the major weld fixtures for the LO2 tank and LH2 tanks (horizontal). Currently, the 5019 LH2 fixture has been unwrapped, with the LO2 5018 machine set to follow.

Once the tools are back in place, Lockheed and Boeing engineer will take measurements of the tools to evaluate their conversion from arc plasma welding to stir friction welding.

This also appears to be preparation work for the construction of SLS tank hardware.

(Images: Via MSFC, Boeing, MAF and L2 content – driven by L2′s new SLS specific L2 section, which includes, presentations, videos, graphics and internal updates on the SLS and HLV available no where else on the internet).

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