Monday, May 15, 2023
12-1pm, Room 31-270
Zoom link: https://mit.zoom.us/j/99313053821
Speakers: Alex Miller, Michael Brown, and Aaron Makikalli
Title: Design Development of Seismo-Geodetic Ice Penetrator: Aerodynamics, Structures, Thermal, Design and Testing
Speaker #1: Alex Miller
- Abstract— Existing measurement tools for ice shelves and other glaciated regions have limited capability to measure dynamic events in remote areas. The Seismo-Geodetic Ice Penetrator (SGIP) offers a method for rapid deployment of a broadband seismometer and Global Navigation Satellite
System (GNSS) positioning system designed to sense resonant forcings between ice shelves, ocean gravity waves and atmospheric waves. Additionally, seismic indications of calving and rifting events can be tracked, facilitating better estimates of sea level rise. In operations, SGIP is dropped from an aerial vehicle at a terminal velocity of 42 m/s and impacts firn at an average acceleration of approximately 500 m/s/s. Upon impact, a fore-body section continues kinetically several meters into the ice shelf while an aft-body "flare" antenna section sheers of and remains at the surface. The SGIP platform is compared to previously envisioned and tested penetrator systems. Impact modeling of SGIP into glacial firn is detailed, with a focus on fast simulation runtimes for design exploration. Designs of snow spikes and a rigid antenna mast are detailed, analyzed and tested. Results from a full-scale prototype hardware test in Juneau, Alaska are discussed.
Speaker #2: Michael Brown
- Abstract— The Seismo-Geodetic Ice Penetrator (SGIP) is an air-dropped kinetic penetrator that will deposit a geophysics-grade seismometer and GPS receiver into Antarctic ice shelves. These instruments will measure vibrations in the infragravity (< 0.1 Hz) range to improve understanding of forces that cause ice shelf calving. The penetrator will impact at its terminal velocity---roughly 40 m/s---to deploy the seismometer at least 2 meters below the ice shelf surface. SGIP will separate into two components, the body and flare, on impact to embed the seismometer into the ice shelf and transmit data from the ice shelf surface, respectively. However, the penetrator's impact can accelerate the primary payload up to 130 g along its central axis, which can damage the delicate seismometer. SGIP uses shock isolation to reduce the seismometer's peak acceleration. A structural response model is used to predict the seismometer's dynamic response to ice shelf impacts with dozens of potential shock isolation designs. This structural response model is used to select a candidate shock isolation design based on SGIP's volume constraints. A shear pin assembly is designed to rigidly connect the body and flare during descent yet deliberately fail on impact to separate the body and flare. Risk reduction tests are conducted to lower the probabilities of the shear pins' four primary failure modes.
Speaker #3: Aaron Makikalli
- Abstract— From an aerodynamic perspective, SGIP’s aft-body must be sized to produce a drag force that results in our target terminal velocity of 42 m/s while remaining aerodynamically stable. A finite element flow simulation in Solidworks and analytical rocket stability calculations are applied to ensure that these requirements are met. Thermally, the penetrator must be insulated so that internal electronics are kept within their operating temperature range without melting the surrounding ice. A Comsol finite element heat transfer model is used to inform the design of thermal insulation for the system that will achieve this.