SCALPSS Project Overview
An 8-minute presentation on the Stereo CAmeras for Lunar Plume Surface Studies (SCALPSS) project, to the Lunar Surface Science Dust and Regolith Workshop on Aug. 20, 2020
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An 8-minute presentation on the Stereo CAmeras for Lunar Plume Surface Studies (SCALPSS) project, to the Lunar Surface Science Dust and Regolith Workshop on Aug. 20, 2020
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During the rocket-powered landing of a vehicle on a planetary body, the interaction between the rocket plume and the surface material beneath the vehicle plays a significant role in the descent dynamics and the safety of powered descent. However, in-situ data taken to investigate plume-surface interaction has been limited. The upcoming flight and lunar landing of the Intuitive Machines Nova-C will be equipped with the Stereo Cameras for Lunar Plume-Surface Studies (SCALPSS) science package, enabling the direct measurement of plume-induced surface cratering during powered descent. In this work, we present the engineering constraints, design iteration process, and simulation results that drove the design selection for the SCALPSS camera system. The chosen design will provide 3D-imaging coverage of 84 percent of the lunar surface directly under the landed Nova-C, in addition to some coverage of the neighboring surface. SCALPSS will provide a total 3D-imaging coverage area of approximately 13 square meters. With the anticipated Nova-C landing in October of 2021, SCALPSS will provide the first dedicated in-situ measurement of plume-induced surface cratering.
Plume-surface interactions between a rocket plume and the lunar surface will be studied in-situ during two of NASA’s upcoming Commercial Lunar Payload Services Program missions. The payload, Stereo Cameras for Lunar Plume-Surface Studies (SCALPSS), will employ a multiple-camera photogrammetry system to obtain stereo images of the lunar regolith before, during, and after significant erosion and subsequent crater formation. The evaluation of measurement system capabilities and design process of the payload is informed by computational fluid dynamics predictions, accuracy modeling based on experimental data, camera simulation, and lander design, all of which are combined in the Virtual Diagnostic Interface. The second SCALPSS mission, traveling to the moon on Firefly Aerospace’s Blue Ghost lander in early 2023, aims to build on the design and complexity of the first payload, which is launching in early 2022 on Intuitive Machines’ Nova-C lander. The Blue Ghost SCALPSS mission will include two additional cameras and a total of three different lens focal lengths which will target specific points in the vehicle’s descent to obtain quantitative and accurate 3D reconstruction of the lunar surface both prior to and after crater formation.
Laboratory measurements have been made to validate the performance of the Stereo CAmeras for Lunar Plume-Surface Studies (SCALPSS) stereo photogrammetry systems which will be flying to the moon on two of NASA’s upcoming Commercial Lunar Payload Services (CLPS) missions. Until recently, the system’s accuracy had only been studied using idealized geometric shapes as measurement targets. A realistic crater model of representative scale and an idealized ‘staircase’ target have been used to compare measurement accuracy of ideal versus lunar-like objects, with the commercial V-STARS® system being used to provide the known reference values for comparison. In a parametric study, altitude, lens focal length, and camera separation are varied to assess each parameter’s impact on photogrammetric accuracy in relation to the scaling law prediction developed previously. The SCALPSS 1.0 and 1.1 configurations have been validated on the crater model within acceptable accuracy for the missions, performing significantly better than the scaling law prediction in some cases. A semi-automated post-processing routine was developed in MATLAB® and proved successful for the cross-correlation of features between two stereo images. For some cases of extreme convergence angles between a camera pair, manual feature detection and matching was required. By using this manual process, the crater depth map was reconstructed but with worse accuracy than the idealized staircase measurements; refinements to the processing algorithm are expected to improve future results. Also examined in this work is the impact of illumination environments, both natural (e.g., Sun angles) and artificial (diffuse or structured illumination sources), on the camera system’s ability to measure the erosion of the lunar terrain.
Laboratory measurements have been made to validate the performance of the Stereo CAmeras for Lunar Plume-Surface Studies (SCALPSS) stereo photogrammetry systems which will be flying to the moon on two of NASA’s upcoming Commercial Lunar Payload Services (CLPS) missions. Until recently, the system’s accuracy had only been studied using idealized geometric shapes as measurement targets. A realistic crater model of representative scale and an idealized ‘staircase’ target have been used to compare measurement accuracy of ideal versus lunar-like objects, with the commercial V-STARS® system being used to provide the known reference values for comparison. In a parametric study, altitude, lens focal length, and camera separation are varied to assess each parameter’s impact on photogrammetric accuracy in relation to the scaling law prediction developed previously. The SCALPSS 1.0 and 1.1 configurations have been validated on the crater model within acceptable accuracy for the missions, performing significantly better than the scaling law prediction in some cases. A semi-automated post-processing routine was developed in MATLAB® and proved successful for the cross-correlation of features between two stereo images. For some cases of extreme convergence angles between a camera pair, manual feature detection and matching was required. By using this manual process, the crater depth map was reconstructed but with worse accuracy than the idealized staircase measurements; refinements to the processing algorithm are expected to improve future results. Also examined in this work is the impact of illumination environments, both natural (e.g., Sun angles) and artificial (diffuse or structured illumination sources), on the camera system’s ability to measure the erosion of the lunar terrain.
Plume-surface interaction is a critical topic of interest as human spaceflight programs establish a renewed presence on the Moon and push onwards to Mars. The erosion of regolith and high-speed ejection of soil and rocks which occurs during a powered spacecraft landing on lunar or terrestrial bodies can pose serious risks to the vehicle during landing and to existing ground assets. Ground testing campaigns have provided data sets in relevant environments (e.g., low pressure) in tandem with predictive computational model validation. To-date, limited in-situ flight data exists to inform the study of the key phenomena of plume-surface interaction: plume-flow physics, soil erosion, and ejecta dynamics. In two upcoming lunar missions, erosion of the lunar regolith will be measured in-situ using the stereo photogrammetry technique as part of NASA’s Commercial Lunar Payload Services (CLPS) Program. The Stereo Cameras for Lunar Plume Surface Studies (SCALPSS) will use a multiple-camera system to measure the erosion of the lunar regolith due to the vehicles’ rocket engine plumes during descent and after landing. The application of stereo photogrammetry to accurately measure a realistic eroded shape has been validated in laboratory work ahead of the scheduled flights. In preparation for future CLPS, Artemis, or other lunar science missions, recent advancements have been made to measure the ejecta structure and particle dynamics in addition to the erosion of regolith using a SCALPSS-like photogrammetry system. The thickness and ejection angle of entrained soil and dust produced during plume-induced erosion can be used to determine how far debris will travel, and thus how it may impact nearby infrastructure or the landing vehicle itself. The present work highlights the development of this new flight instrumentation capability and its value to advancements in the plume-surface interaction measurement topic for lunar or planetary landings.
With rapidly increased worldwide interest in landing on the moon, the issue of Plume Surface Interactions (PSI) is gaining attention. Hazards posed by lander plume induced dust and debris, as well as landing site deformation can be mitigated when better understood through predictive simulations. As simulation enabling computational power continues to increase, hybrid Computational Fluid Dynamics (CFD)/Engineering models provide the immediate ability to conduct parametric/trade studies driving design decisions for landers. Reduced order erosion engineering models apply correlations of the surface erosion rate to the plume induced surface forces with the correlations anchored to flight observations from Apollo LM landings. The MSFC propulsion fluid dynamics branch has developed such a hybrid model for predicting the plume induced viscous erosive regression of the Lunar surface beneath a landing vehicle. The (Descent Interpolated Gas Granular Erosion Model) DIGGEM was originally implemented as a post processing tool to calculate induced erosion rates through vehicle descent using CFD solutions of the vehicle plume at several fixed altitudes. This capability has since been advanced in the Loci/Chem-DIGGEM model to allow transient, moving vehicle, fully coupled viscous erosion modeling of vehicle descent PSI. This model has recently been used to make preflight predictions of the erosive regression of the ground beneath a Commercial Lunar Payload Services (CLPS) vehicle in support of measurements to be made by the Stereo Cameras for Lunar Plume Surface Studies (SCALPSS) instrument.
With rapidly increased worldwide interest in landing on the moon, the issue of Plume Surface Interactions (PSI) is gaining attention. Hazards posed by lander plume induced dust and debris, as well as landing site deformation can be mitigated when better understood through predictive simulations. As simulation enabling computational power continues to increase, hybrid Computational Fluid Dynamics (CFD)/Engineering models provide the immediate ability to conduct parametric/trade studies driving design decisions for landers. Reduced order erosion engineering models apply correlations of the surface erosion rate to the plume induced surface forces with the correlations anchored to flight observations from Apollo LM landings. The MSFC propulsion fluid dynamics branch has developed such a hybrid model for predicting the plume induced viscous erosive regression of the Lunar surface beneath a landing vehicle. The (Descent Interpolated Gas Granular Erosion Model) DIGGEM was originally implemented as a post processing tool to calculate induced erosion rates through vehicle descent using CFD solutions of the vehicle plume at several fixed altitudes. This capability has since been advanced in the Loci/Chem-DIGGEM model to allow transient, moving vehicle, fully coupled viscous erosion modeling of vehicle descent PSI. This model has recently been used to make preflight predictions of the erosive regression of the ground beneath a Commercial Lunar Payload Services (CLPS) vehicle in support of measurements to be made by the Stereo Cameras for Lunar Plume Surface Studies (SCALPSS) instrument.