Statement of Work (SOW) for a Payload Adapter Determinant Assembly.pdf

Statement of Work for a Determinant Assembly for the SLS B1B Payload Adapter

1. Scope

This Statement of Work (SOW) defines the effort required to perform the assembly of SLS Block 1B Payload Adapter (PLA) at NASA Marshall Space Flight Center. This SOW will encompass the assembly of the PLA 3100-1020 configuration of the full-scale structural qualification unit (Qual).

2. Background

NASA/MSFC is currently developing and building a Payload Adapter (PLA) in support of the Space Launch System (SLS) rocket. The PLA must be capable of multiple configurations in a cost effective and schedule friendly manner to accommodate varying mission and payload requirements that drive design changes to the adapter. Hard tooling assembly approaches require design, procurement, fabrication, and assembly of components, significantly increasing lead time between a configuration design release and assembly of the structure. Determinant assembly methods are becoming increasingly common across the aerospace industry to reduce design cycle lag and schedule impacts, reduce tooling costs, and increase flexibility. Determinant assembly is a method that uses the individual components geometry and their relationship to each other to control the final state of the assembly.

3. Responsibilities

3.1. Technical Changes

All technical changes during contract performance will require written authorization from the Contracting Officer responsible for the procurement.

3.2. Operations

The Contractor will be responsible for all operations needed to collect the required structure light data, build the Digital Model, drill the matching holes in the composite panels and assist in the actual assembly of the hardware.

3.3. Materials

The Contractor will have access to existing assembly tooling used for assembling the Manufacturing Demonstration Article (MDA). The Contractor is responsible for purchasing or providing any other assembly aids, materials, equipment, or software needed to perform the assembly of these articles.

3.4. Facility Coordination

Flight hardware for another project is housed within the same high bay facility as the PLA assembly area. All planned work in the area must be coordinated with the PLA team for review with the other program to ensure no conflicts in room procedures or activities arise.

4. Requirements

The work required by this contract shall be performed in accordance with this Statement of Work

(SOW).

4.1. Kick-off meeting

The Contractor shall host a kick-off meeting after contract award that includes the following topics:

1. ITAR data handling

2. Planned work briefing and summary (including final deliverables)

3. Schedule

4. Identification of limitations & risks to the PLA point design

4.2. General Description

PLA is composed of 8 aft ring segments, a single piece forged forward ring, and 8 composite sandwich panels. The panel-to-ring joints are mechanically fastened, and the panel-to-panel joints utilize composite bonds (completed after final fastener assembly). There are approximately 1000 fasteners in total between the forward (FWD) and aft (AFT) rings and the composite panels.

The determinant assembly method is a digital tool computer-aided design (CAD) model used to define all critical interfaces and establish the ideal relationship between parts to meet the assembly dimensional requirements and the hierarch between parts. The determinant assembly method herein involves measuring the geometry of all structural components of the Payload Adapter including the composite panels and the FWD and AFT ring components. The locations of the bolt holes in the metal components are transferred to the composite panels through the construction of a Digital Tool.

The corresponding holes in the composite panel will be drilled using structured light guided drill block. The bolt to hole tolerances shall meet the Tight Fit as described in Appendix F of MSFC- STD-3528. The use of temporary fasteners and reaming methods are acceptable if necessary to meet the required bolt to hole tolerances.

4.3. Assembly Tolerances

The PLA shall be assembled to the general tolerances detailed below. Tolerances provided on the PLA assembly drawing shall supersede these values if different.

4.3.1. Height

The assembly method shall be capable of assembling the PLA with a resulting overall height within ±0.060in.

4.3.2. Flatness

The assembly method shall be capable of assembling the PLA aft ring with a resulting flatness of ±0.030in.

4.3.3. Interface Bolt Circle Position

The assembly method shall be capable of assembling the PLA with an interface bolt circle true positional tolerance relative to the aft interface surface and secondary to flange OD of ±0.029in.

4.3.4. Parallelism

The assembly method shall be capable of assembling the PLA with the FWD ring parallel relatively to the AFT ring interface surface within ±0.030in.

4.3.5. True Position

The assembly method shall be capable of assembling the PLA with the FWD ring having a true position relative to the AFT ring OD of ±0.060in.

4.3.6. Panel to Panel Gap

The assembly method shall be capable of assembling the PLA with gaps between composite panels measuring 0.20in +0.05/-0.05in.

4.3.7. Panel to AFT Ring Gap

The assembly method shall be capable of assembling the PLA with gaps between the AFT ring and Composite Panels measuring 0.10in±0.010in.

4.3.8. Hole Location

The assembly method shall be capable of match drilling holes through the metallic rings, and composite panels within a positional tolerance of ±0.090in.

4.4. Geometric Inspection Reports

The contractor shall use structure light scanning to capture the geometry of the individual components and provide geometric inspection reports compared to each components CAD / drawing. The inspection reports shall be provided in a format NASA Quality can use for Quality Assurance purposes. The components that shall be structure light scanned and inspected to their respective drawings are the FWD ring, the eight AFT ring segments and the eight composite panels, before drilling and post drilling operations.

4.5. Communication

The Contractor shall periodically host status meetings to communicate progress, schedule status and problems/issue. The meetings, at minimum, shall be biweekly.

4.6. General Requirements

The Contractor shall meet the following general requirements,

4.6.1. A subject matter expert and 15-plus years’ experience utilizing structured light scanning & photogrammetry methodologies.

4.6.2. A subject matter expert and 15-plus years’ experience in top-down design with Creo Parametric and the associated PTC Product Management Tools.

4.6.3. Extensive experience developing and managing top-down frameworks for other complex space systems.

4.6.4. Extensive experience in model-based design.

4.6.5. Experience in constrained, non-linear design optimization and analysis of complex integrated system assemblies and mechanisms.

4.6.6. Experience manufacturing aerospace hardware that has been derived and designed within a top-down framework.

4.6.7. Experience with determinant assembly methodologies; utilizing component metrology to inform subsequent assembly steps to create high precision hardware for space systems.

4.6.8. Immediate Access to Redstone Arsenal and Marshall Space Flight Center after contract award is required to support technical and programmatic meetings. Participation is required.

5. Safety

The Contractor shall incorporate perform work in a manner consistent with OSHA and NASA MSFC safety standards.

Operators of cranes (mobile cranes, bridge cranes, gantry cranes, truck-mounted booms, and swing-arm shop cranes) shall meet the regulations in OSHA 29 CFR 1910.179. If the government overhead crane is to be used for this operation, the Contractor shall provide verification of the operator’s certification and shall be required to demonstrate proficiency on the government equipment. Prior to use of all the rigging equipment and crane certification, and personnel certifications/licenses must be verified by the government.

The Contractor shall provide written safety instructions identifying potential hazards and the method of which to mitigate the hazard, if applicable.

6. Final Tolerance Evaluation

The Contractor shall evaluate the tolerances achieved during the MDA and verify that the assembly method is capable of meeting the requirements listed in section 4.4.

7. Deliverables

The Contractor shall provide, at minimum, the following products:

- Summary of work completed. This should include, at minimum:

o Documentation of work completed o Individual component geometric comparisons to CAD o Final tolerances achieved during the assembly of the PLA

8. Period of Performance

The period of performance is four months from award.