Mars Urchin

Charlene Cheung, Faviola Loera, Sandra Medina, Taylor Wirth

Fig 1: Prototype hand operated lantern in the open and closed position.

PROJECT BACKGROUND:

Bio-inspired design is an emerging field in mechanical engineering and materials science.  Scientists take inspiration from nature to develop high-performance materials and devices. Researchers inspired by the sea urchin’s chewing organ, Aristotle’s lantern, recently developed a biopsy harvester which combined precise tissue incision with biopsy retrieval in a single device (Jelinek, et al., 2014). The mechanism of Aristotle’s lantern is to open when protruding outwards and close when retracting inwards. This allows sea urchins to simultaneously cut off and enclose their food in a unified and continuous motion. High-resolution micro‐computed tomography (micro-CT) images of the sea urchin and Aristotle’s lantern were obtained via x-rays to create cross sections, then reconstituted and manipulated in 3-D space (Fig 2). 

The Mars rover, Curiosity, landed in August 2012 in order to survey Martian surface geology. Last July at the 8th International Conference on Mars, plans were discussed for NASA’s 2020 Mars rover to collect samples for future return to Earth (Fig 2). Curiosity’s aluminum wheels have incurred significant damage from traversing over wind sharpened rocks. This issue effectively limits the area which any Mars rover can explore using its sophisticated on-board instrumentation. With that complication in mind, Professor Joanna McKittrick and her research group proposed a robust, lightweight, bio-­inspired Mars mini-­rover which can collect samples efficiently and return them to the main rover for further analysis.

Fig 2: (a) A fragile pink sea urchin from the Monterey Bay Aquarium

(b) Micro-CT images of a sea urchin with Aristotle’s lantern visible in the center (ventral view). Close-up of 

(c) the five teeth stacked on top of each other. 

(d) Distal portions of the teeth are removed to show the orthogonally  attached keels underneath. 

(e) A side view shows the outer pyramid structures which support the teeth inside.

Taken from http://www.montereybayaquarium.org/

FINAL DESIGN DESCRIPTION:

The final design for the "Mars Urchin" is composed of three major systems:

1. Lantern System

   • Replicated sea urchin lantern controlled by a linear actuator

2. Screw Drive System

   • Controls the vertical motion of the Lantern system with a 60 RPM gear motor

3. Gear System

   • Controls the rotation of the Screw Drive and Lantern System with a 6 RPM motor driving a slew bearing

The sampling system can hold 3 samples in one deployment.

All the electrical components are controlled with a wireless transmitter that is human operated, thus no interaction is needed to take and store the samples.  The electronics are powered by a rechargeable 12V NiMH battery pack.  

The entire system is mounted onto an RC "Rover" where it can drive to any desired sampling position.  The Rover is controlled separately from the sampling system.  

Fig 3: Mars Urchin final design with major components highlighted.

PERFORMANCE RESULTS:

Initial Lantern Beach Test:

• Determine force necessary for Lantern to penetrate soft and compact sand.

  • minimum of 25 Newtons to penetrate soft sand.

  • minimum of 45 Newtons to penetrate compact sand.

• Solution:

  • Use crank&slider linkage analysis to determine method to fully open Lantern.

  • Redesigned crank link to be in a different location to fully open Lantern so penetration angle is at 90 degrees.

  • Chamfered tooth to create overlap feature and to create a sharper penetration point.

Final Beach Demo Test:

• Mars Urchin rover needed to drive 3 meters in between 3 samples and return to the starting position.

• The system was capable of doing this in both soft and compacted sediment

• 2.5 minute sampling interval

• 2 cm3 sediment retention per holding container                 

Fig 5: Lantern prototype sampling Mars simulant sediment and depositing into another container.