SOW.pdf

Development, Enhancement, and Validation of Propulsion Dynamic Models for Pogo

Statement of Work

1. Background

The Space Launch System (SLS) Exploration Upper Stage (EUS) uses four RL10C-3 engines.

Previous variants of the RL10 have been tied to pogo. The Centaur stage experienced a “longitudinal event” in 2003. United Launch Alliance (ULA) installed a pogo suppressor as a short-term fix, but later redesigned the RL10 inducer to push the forcing function away from the vehicle axial modes. ER42 worked with ULA to develop this solution. However, as pogo is dependent on the propulsion system and the specific vehicle and stage modes, a fix for Centaur is not necessarily a fix for all vehicles.

SLS vehicle integrated pogo models for Block 1B currently show no stability margin. ER42 is responsible for providing the propulsion dynamic characteristics that are input into the vehicle integrated pogo model. The pogo model and its propulsion dynamic inputs need to be refined to increase accuracy to determine if indeed a pogo instability is predicted. If it is, a pogo suppressor must be designed and implemented in the upper stage. Design, development, implementation, and validation of the pogo suppressor will increase estimated costs substantially and severely impact the schedule of Artemis III. Therefore, SLS would like more accurate models to determine if a pogo suppressor is required.

To achieve a more accurate propulsion dynamic model, higher fidelity terms must be added, validated, and implemented into the model.

2. Scope

The contractor shall implement within the existing ER42 pogo propulsion models high fidelity terms and enhancements to improve the models’ accuracy for SLS. The contractor shall use existing pump dynamic data, including ER42’s recently obtained waterflow data for RL-10 to assist in the development of enhancements to the pump dynamics models. In conjunction with NASA/MSFC personnel, the contractor shall establish a verification/validation test suite for pump models and implement the validation assessment. With NASA/MSFC personnel, the contractor shall apply the enhanced pogo models to the EUS configuration and conditions. The contractor shall document the existing models, the enhancements, and validation assessment.

The contractor shall also evaluate what enhancements would be needed to implement the propulsion models for the Human Lander System Sustainable Lander.

3. Task

The contractor shall:

• Implement within the existing ER42 pogo propulsion models high fidelity terms and enhancements to improve the models accuracy for SLS. The contractor shall use existing pump dynamic data, including ER42’s recently obtained waterflow data for RL-10 to assist in the development of the enhancements to the pump dynamics models. All work will be done on-site at MSFC.

• Establish, in conjunction with NASA/MSFC ER42 personnel, a verification/validation test suite for pump models and implement the validation assessment. All work will be done on-site at MSFC.

• Apply the enhanced pogo models to the EUS configuration and conditions.

• Fully document existing models and any algorithmic alterations and results of any verification and validation efforts in interim and final reports. All work will be done on-site at MSFC.

• Evaluate what enhancements would be needed to implement the propulsion models for the Human Lander System Sustainable Lander and document the assessment. All work will be done on-site at MSFC.

4. Deliverables

The following documentation and reporting will be required: 1) Final and status reports detailing the model assessments, model enhancements, verification/validation assessments, and model application to SLS.

5. Deliverable Products

Item

SOW

Ref.

Due Date (in Weeks

After Award)

Number of

Copies

Format

Distribution

1. Documentation detailing the model assessments, model enhancements, verification/validation assessments, and model application to SLS.

Completion of Effort 1 Electronic

ER and Transmittal Letter to PS

2. Status Reports 4 At 2 months and 4 months 2 Electronic ER and PS

6. Period of Performance

6 months