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By NASA
3 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA’s Stennis Space Center near Bay St. Louis, Mississippi, is helping the Artemis Generation learn how to power space dreams with an interactive exhibit at INFINITY Science Center.
The engine test simulator exhibit at the official visitor center of NASA Stennis provides the chance to experience the thrill of being a NASA test engineer by guiding an RS-25 engine through a simulated hot fire test.
“It is an exhilarating opportunity to feel what it is like to be a NASA engineer, responsible for making sure the engine is safely tested for launch,” said Chris Barnett-Woods, a NASA engineer that helped develop the software for the exhibit.
Sitting at a console mirroring the actual NASA Stennis Test Control Center, users are immersed in the complex process of engine testing. The exhibit uses cutting-edge software and visual displays to teach participants how to manage liquid oxygen and liquid hydrogen propellants, and other essential elements during a hot fire.
A pair of young visitors to INFINITY Science Center carry out the steps of a simulated RS-25 engine hot fire on Dec. 19. The updated engine test simulator exhibit provided by NASA’s Stennis Space Center takes users through the hot fire process just as real engineers do at NASA Stennis.NASA/Danny Nowlin INFINITY Science Center, the official visitor center for NASA’s Stennis Space Center, has unveiled a new interactive simulator exhibit that allows visitors to become the test conductor for an RS-25 engine hot fire. NASA/Danny Nowlin Users follow step-by-step instructions that include pressing buttons, managing propellant tanks, and even closing the flare stack, just as real engineers do at NASA Stennis. Once the test is complete, they are congratulated for successfully conducting their own rocket engine hot fire.
The interactive exhibit is not just about pushing buttons. It is packed with interesting facts about the RS-25 engine, which helps power NASA’s Artemis missions as the agency explores secrets of the universe for the benefit of all. Visitors also can view real hot fires conducted at NASA Stennis from multiple angles, deepening their understanding of rocket propulsion testing and NASA’s journey back to the Moon and beyond.
NASA is currently preparing for the Artemis II mission, the first crewed flight test of the agency’s powerful SLS (Space Launch System) rocket and the Orion spacecraft around the Moon.
The first four Artemis missions are using modified space shuttle main engines tested at NASA Stennis. The center also achieved a testing milestone last April for engines to power future Artemis missions. For each Artemis mission, four RS-25 engines, along with a pair of solid rocket boosters, power NASA’s SLS rocket, producing more than 8.8 million pounds of total combined thrust at liftoff.
The revitalized exhibit, previously used when the visitor center was located onsite, represents a collaborative effort. It started as an intern project in the summer of 2023 before evolving into a full-scale experience. Engineers built on the initial concept, integrating carpentry, audio, and video to create the seamless experience to educate and inspire.
The best part might be that visitors to INFINITY Science Center can repeat the simulation as many times as they like, gaining confidence and learning more with each attempt.
“This exhibit was a favorite in the past, and with its new upgrades, the engine test simulator is poised to capture the imaginations of the Artemis Generation at INFINITY Science Center,” said NASA Public Affairs Specialist Samone Wilson. “This is one exhibit you will not want to miss.” INFINITY Science Center is located at 1 Discovery Circle, Pearlington, Mississippi. For hours of operation and admission information, please visit www.visitinfinity.com.
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Last Updated Dec 20, 2024 EditorNASA Stennis CommunicationsContactC. Lacy Thompsoncalvin.l.thompson@nasa.gov / (228) 688-3333LocationStennis Space Center Related Terms
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By NASA
Download PDF: Statistical Analysis Using Random Forest Algorithm Provides Key Insights into Parachute Energy Modulator System
Energy modulators (EM), also known as energy absorbers, are safety-critical components that are used to control shocks and impulses in a load path. EMs are textile devices typically manufactured out of nylon, Kevlar® and other materials, and control loads by breaking rows of stitches that bind a strong base webbing together as shown in Figure 1. A familiar EM application is a fall-protection harness used by workers to prevent injury from shock loads when the harness arrests a fall. EMs are also widely used in parachute systems to control shock loads experienced during the various stages of parachute system deployment.
Random forest is an innovative algorithm for data classification used in statistics and machine learning. It is an easy to use and highly flexible ensemble learning method. The random forest algorithm is capable of modeling both categorical and continuous data and can handle large datasets, making it applicable in many situations. It also makes it easy to evaluate the relative importance of variables and maintains accuracy even when a dataset has missing values.
Random forests model the relationship between a response variable and a set of predictor or independent variables by creating a collection of decision trees. Each decision tree is built from a random sample of the data. The individual trees are then combined through methods such as averaging or voting to determine the final prediction (Figure 2). A decision tree is a non-parametric supervised learning algorithm that partitions the data using a series of branching binary decisions. Decision trees inherently identify key features of the data and provide a ranking of the contribution of each feature based on when it becomes relevant. This capability can be used to determine the relative importance of the input variables (Figure 3). Decision trees are useful for exploring relationships but can have poor accuracy unless they are combined into random forests or other tree-based models.
The performance of a random forest can be evaluated using out-of-bag error and cross-validation techniques. Random forests often use random sampling with replacement from the original dataset to create each decision tree. This is also known as bootstrap sampling and forms a bootstrap forest. The data included in the bootstrap sample are referred to as in-the-bag, while the data not selected are out-of-bag. Since the out-of-bag data were not used to generate the decision tree, they can be used as an internal measure of the accuracy of the model. Cross-validation can be used to assess how well the results of a random forest model will generalize to an independent dataset. In this approach, the data are split into a training dataset used to generate the decision trees and build the model and a validation dataset used to evaluate the model’s performance. Evaluating the model on the independent validation dataset provides an estimate of how accurately the model will perform in practice and helps avoid problems such as overfitting or sampling bias. A good model performs well on
both the training data and the validation data.
The complex nature of the EM system made it difficult for the team to identify how various parameters influenced EM behavior. A bootstrap forest analysis was applied to the test dataset and was able to identify five key variables associated with higher probability of damage and/or anomalous behavior. The identified key variables provided a basis for further testing and redesign of the EM system. These results also provided essential insight to the investigation and aided in development of flight rationale for future use cases.
For information, contact Dr. Sara R. Wilson. sara.r.wilson@nasa.gov
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By NASA
Download PDF: Contact Dynamics Predictions Utilizing theNESC Parameterless Contact Model
Modeling the capture of the Mars Sample Return (MSR) Orbiting Sample (OS) involves understanding complex dynamic behavior, which includes the OS making contact against the interior of the capture enclosure. The MSR Program required numerical verification of the contact dynamics’ predictions produced using their commercial software tools. This commercial software used “free” parameters to set up the contact modeling. Free parameters (also known as free variables) are not based on contact physics. The commercial contact model used by MSR
required seven free parameters including a Hertzian contact stiffness, surface penetration, stiffening exponent, penetration velocity, contact damping, maximum penetration depth for the contact damping value, and a smoothing function. An example of a parameter that is not free is coefficient of friction, which is a physics-based parameter. Consider the free parameter, contact stiffness. Contact stiffness is already present in the finite element model’s (FEM) stiffness matrix where the bodies come into contact, and surface penetration is disallowed in a physically realizable contact model, as FEM meshes should not penetrate one another during contact (i.e., the zero-contact limit penetration constraint condition).
As such, with each set of selected free parameters generating a different contact force signature, additional numerical verification is required to guide setting these parameters. Contact modeling is nonlinear. This means that the stiffness matrices of contacting bodies are continuously updated as the bodies come into contact, potentially recontact (due to vibrations), and disengage. The modal properties of contacting bodies continuously change with state transitions (e.g., stick-to-slip). Some contact models have been proposed and incorporated in commercial finite element analysis solvers, and most involve static loading. A relatively smaller number involve dynamics, which has historically proven challenging.
In 2005, NASA conducted a study testing several commercial contact solvers in predicting contact forces in transient dynamic environments. This was necessitated by the Space Shuttle Program (SSP)—after the February 2003 Columbia accident— deciding to include contact dynamics in the Space Shuttle transient coupled loads analysis (CLA) to capture the impact of contact nonlinearities. This rendered the entire CLA nonlinear. The study found major difficulties executing nonlinear CLAs in commercial software. A nonlinear solver developed by the NESC and Applied Structural Dynamics (ASD) that was able to produce physically realizable results was numerically verified by NASA and later experimentally validated as well. This nonlinear solver was subsequently utilized to execute all NASA SSP CLAs (i.e., crewed space flights) from 2005 to the final flight in 2011, as well as currently supporting the SLS Program.
The objective of the MSR contact verification work was to provide data that could be used by the MSR team to help define the free parameters listed above for the commercial tool contact model. The NESC/ASD solver was used to model contact between simple cantilever and free beams, deriving contact forces and relative displacements. These resulting data can be used to determine parameter values for more complex structures. Two of the modeled configurations, one for axial contact (Figure 1) and the other for stick/friction (Figure 2), and sample results from the NESC nonlinear dynamic analyses are presented in Figures 1 and 2.
For information, contact:
Dr. Dexter Johnson dexter.johnson@nasa.gov
Dr. Arya Majed arya.majed@nasa.gov
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By European Space Agency
Video: 00:11:10 In 2024, ESA continued to drive Europe’s innovation and excellence in space, equipping the continent with advanced tools and knowledge to address global and local challenges. The year saw pioneering missions, cutting-edge satellites and the pivotal restoration of Europe’s independent access to space.
The first Ariane 6 launch was perhaps ‘the’ highlight of the year but it was only one of many achievements. We saw the last Vega launch and then the return to flight of Vega-C, the more powerful, upgraded version carrying Sentinel-1C.
Far away in our Solar System, the ESA/JAXA BepiColombo spacecraft performed twoMercury flybys in 2024, needed so that it can enter orbit around Mercury in 2026. Juice also performed a crucial gravity assist, this time becoming the first spacecraft to conduct a Moon-Earth double flyby on its way to Jupiter.
Twenty years after ESA’s Rosetta was launched and 10 years since its historic arrival at the comet 67P/Churyumov-Gerasimenko, we launched another spacecraft to a small body, the Hera planetary defence mission to investigate asteroid Dimorphos.
2024 was an important year for Europe’s Galileo constellation which continued to expand with the launch of four new satellites and an updated Galileo ground system. The year also saw the launch of ESA’s Proba-3 mission: two precision formation-flying satellites forming a solar coronagraph to study the Sun’s faint corona.
In human spaceflight, Europe continues to contribute to science from the ISS as Andreas Mogensen’s Huginn mission continued into 2024. Andreas even met up in space with ESA project astronaut Marcus Wandt who was launched on his Muninn mission, making it the first time two Scandinavians were in space together.
Meanwhile the latest class of ESA astronauts completed basic training and graduated in April. Two of them, Sophie and Raphaël, were then assigned to long-duration missions to the ISS in 2026.
We made crucial steps for Europe in gaining access to the Moon: the inauguration of our LUNA facility with DLR, and the delivery of a third European Service Module for NASA’s Orion spacecraft as part of the Artemis programme.
Europe is also contributing to the international Lunar Gateway and developing and ESA lunar lander called Argonaut. These landers will rely on ESA Moonlight, the programme to establish Europe’s first dedicated satellite constellation for lunar communication and navigation.
As 2024 draws to a close, ESA’s achievements this year have reinforced Europe’s role in space. ESA’s journey continues to explore new frontiers, shaping the space landscape for generations to come.
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