Jackhammer Extraction Tool (JET)

Problem: How to collect water from an Ice deposit that is located half a meter under rock, and is multiple meters thick?

Solution: JET is a jackhammer tool with a detachable heated tip and a cable driving system. The jackhammer penetrates through the Martian overburden to access ice, then employs the Rodwell water extraction method by melting an area of ice and heating the resulting pool of water until it grows into a large subsurface reservoir. As the reservoir becomes larger, the detachable heated tip is lowered into the water by the cable driving system. All water is pumped out of the reservoir when a sufficiently large region has been melted.

Unique Design Feature: JET Tip

Problem: How do we create a tool to melt ice and sink deep into an ice deposit to extract all the water?

Action: I designed a detachable tip for the JET that contained a 200W cartridge heater, and a water inlet port. The tip would detach from the jackhammer and sink into the ice as it melted. The tip took four design iterations and was driven by results from physical testing and from SolidWorks finite element analysis.

The initial concept was predominantly aesthetic for our proposal. It contained all the necessary elements, and was designed to mimic the consumer moil point chisel tool, but was not designed for manufacturability and assembly in mind.

The first iteration was designed for manufacturability. Once it was tested, it became clear that the tip of the tool received such poor heat transfer, that even if the rest of the body was hot, the tip would never descend into the ice. Our proposed fix to this was to machine off excess material on the tip and create external geometry resembling a chisel rather than a spear. Side by side thermal analysis is shown above.

Iteration two was a quick modification of the initial prototype to validate this theory. We made the change in SolidWorks, analyzed heat transfer conditions for both tips with the power from a 200W cartridge heater, and fully submerged each in freezing water. As shown in these images, the new version had a much more uniform distribution of heat, allowing the tip to heat enough to melt the ice holding it in place.

The third and final iteration of the design was to allow for two 150W cartridge heaters, as well as changing the external geometry of the part from a taper with a chisel tip to a cylinder with a chisel tip. In this final iteration, the external surface behaved in the most uniform manner. It also was capable of outputting 50% more power than all the prior versions.

Result: This final design was the one we implemented and sent to Langley Virginia to show off at the challenge.

Unique Design Feature: Cable Clamp

Problem: How to secure the JET tip to the jackhammer while jackhammering, and release the tip into the ice while melting?

Action: To solve this problem, I developed a cable driving system that would spool cable at the top of the jackhammer, then lock that cable in place for the duration of the jackhammering process. Once the jackhammering was complete, the cable would be released, then unspooled to drive the JET tip into the ice.

An additional constraint that added complexity to this problem was that we could not afford to pay for electromechanical actuators that were rated to withstand vibrations and shock from a jackhammer. The entire clamping and spooling mechanism needed to be actuated from off of the jackhammer. To do this, the spool was driven by a stepper motor that was mounted rigidly to the PUDLE frame. When the jackhammer was off, it could raise and lower the JET tip via cables routed through the top of the JET. When the jackhammer was operating, this spool would not keep the tip locked in place. Instead, a pin with a through-hole was firmly clamping the cable in place. This pin was actuated via a linear actuator mounted to the PUDLE frame. The linear clamping actuation was transferred by a bike gear shifting cable to the pin.

Result: This clamping design operated effectively for multiple days of jackhammer testing, as well as through the full 12 hour Mars Ice Challenge competition.