IceBite Blog: Success in University Valley
The IceBreaker 2010 Antarctic team (from left to right): Wayne Pollard of McGill University, Andrew Jackson of Texas Tech, Alfonso Davila of NASA Ames, Margarita Marinova of NASA Ames, Gale Paulsen and Kris Zacny, from Honeybee Robotics. Credit: Kris Zacny
This is my last blog. I’m writing it somewhere over the Antarctic inside a C17 airplane on our way from McMurdo to Christchurch, New Zealand. A C17 is a very impressive airplane. We are sitting along the fuselage facing each other, with cargo in the middle. A C130 airplane propeller is right in front of me – within my arms’ reach. To the left, I see our bags we dropped off last night, and to the right, some people sleeping on the floor. Only now do I realize that the Antarctic adventure is coming to a close.
Our drill team traveled to the Antarctic to test a new generation of a rotary-percussive drill, called the IceBreaker. The drill was designed as a prototype for a drill that one day will fly to Mars and penetrate at least 1 meter into martian ice and permafrost.
We selected University Valley within Antarctica’s Dry Valleys region as an ideal Mars analog and drilling test location for two reasons: (1) temperatures are relatively low, reaching -25°C during the time we stayed there (beginning of summer); and (2) University Valley has a desiccated layer overlaying ice-cemented ground towards the valley’s mouth and massive ice towards the valley’s head. NASA’s Phoenix mission in 2008 landed in the northern polar region of Mars and found ice below a few inches of sandy soil – almost exactly what we see in University Valley.
Our goal was to drill at least 1 meter into ice-cemented ground and another meter into ice. In both cases, we had to acquire samples at 10 cm intervals. This probably seems like a simple task, but there is a catch. All the drilling action had to be performed autonomously, no human intervention was allowed. Since 2004 we have been operating the Rock Abrasion Tools (RATs) on the Mars Exploration Rovers, Spirit and Opportunity, and thus have learned the extent of autonomy that robotic systems can have. We duplicated this kind of autonomy when designing the IceBreaker drill. The drill has only three commands: Seek (it finds the ground), Drill (it performs drilling action), Pull Out (pulls out of the hole and deposits sample into a cup). Although these seem like simple commands, behind each one of them hides an algorithm that analyzes drilling telemetry and makes decisions on how to proceed further.
Honeybee Robotics engineers Kris Zacny (l) and Gale Paulsen with the assembled Icebreaker drill outside the team’s laboratory in McMurdo Station, Antarctica
Our first task was to assemble the drill in the field. Our system was broken down into small subsections that included a drill base, a vertical stage (which had never been tested prior to this field campaign), the drill head, an auger with a bit at the end, a sampling system (which had also never been tested), and electronics. We rushed to meet the shipping deadline for Antarctic and hence didn’t have time to test some of its components. The Antarctic would be the true testing ground.
All the drill components were secured inside robust pelican cases and transported inside a sling (a net suspended under a helicopter) from McMurdo to the Dry Valleys. To assemble the drill, we had to pull all these items out and put them together, just like Lego blocks. Once the drill was put together, Gale Paulsen, Honeybee system engineer and the IceBreaker operator, went inside a warm tent, while I stayed behind to watch the drill in action and to take lots of pictures and movies. For the next few hours, Gale and I were not allowed to communicate. Gale was on Earth (inside the tent), while I was on Mars (outside and next to the drill).
The weather was perfect: very cold, with surface temperatures reaching -25°C (-13°F) and subsurface temperature at around -20°C (-4°F). Fortunately for me, we had no wind.
Gale must have pushed the Seek button, because all of the sudden I saw the drill slowly rotating and moving down. After a few minutes, the drill touched the ground, moved up an inch and stopped. So far all went well. Next, the drill started to rotate faster and moved down at higher speed. Soon the drill bit touched the surface and started to cut into the overlying desiccated layer before hitting rock-hard ice-cemented ground. After reaching 10 cm (4 inches), the drill moved up and deposited cuttings into a small bag. I took the bag, put it aside, and attached a new one in its place. Our next drill upgrade would be to replace this human action of swapping bags with a robotic system (then I could also sit inside a warm tent).
Drilling to 1 meter (40 inches) deep in ice-cemented ground. During the drilling process we met the “1-1-100-100” target: drilling to a depth of 1 meter in 1 hour, using 100 Watts of power and a 100-Newton preload. Credit: Kris Zacny
The drill went down again, but this time to a depth of 20 cm (8 inches), and came up depositing more samples. This process continued until we reach our target of 1 meter (40 inches). During this drilling process, our power was less than 100 Watts (that’s as much as a light bulb needs), the force of the bit pushing against the ground was less than 100 Newtons (around 20 lbs), and it took around 1 hour to reach 1 meter. We call it drilling with 1-1-100-100 (1 hour to 1m with 100 W and 100 N).
At the same time we measured a temperature at the bit, to make sure we didn’t heat it up too much. A warm bit will indicate that we are putting too much heat into the formation, which may cause the ice within the soil or rock to melt. We want to avoid melting by all means, since thaw followed by re-freeze is the main cause of stuck drill bits in the Antarctic and other cold regions. Our maximum bit temperature was always less than -5°C (23ºF) and on average it was more like -10°C (14ºF), that is, only 10°C above the ground temperature and 10°C below melting temperature. We were drilling in a safe regime.
With this demonstration, we have shown that drilling on Mars (and also on the moon, in regions that contain water-ice, for example) is possible. The power, energy and preload are all within the payload capability of a small lander.
Since we still had lots of time, we decided to drill another two holes. We varied drilling procedures and tested other sampling methods and protocols. All worked great and we collected more samples. The goal was just one hole, and we drilled three. We decided to call it a day and prepare the drill for a 600 feet traverse across the boulder field towards the glacier: Our next stop was massive ice.
The following day, our IceBreaker team moved parts of the drill into the new site – in the middle of a boulder field. There was massive ice below. Assembling the drill proved to be quite challenging. Our gloves were bulky and we had to use bare hands to lift and screw parts together. After one minute exposed to cold air and touching very cold metal, our fingers would go numb. We would have to warm them up inside gloves for a few minutes before continuing. We realized how lucky we had been the first time, when assembling the drill inside a tent.
Drilling in ice proved to be relatively easy, as expected. We drilled to 1 meter in no time and collected samples. Upon close inspection of ice-chips, as they were coming up the drill auger, we noticed that some of these ice chips are as large as 0.6 cm (0.25 inch). That meant that our drilling approach doesn’t completely destroy the ice. We can still acquire large ice chunks for either visual or other investigations.
Drilling 2.5 meters (100 inches) deep in massive ice. Kris Zacny (left) holds bags of ice chips collected during the drilling process. Gale Paulsen (right) holds the 2.5 m long drill string. Credit: Kris Zacny
It was only around lunchtime, so we decided to carry on drilling until we reached 2.5 meters (100 inches). The day was cold, and we were very cold. I looked at Gale and could see that he was thinking what I was thinking. Well, we came to drill 1 meter and we drilled to a depth of 2.5 meters. It proves that the IceBreaker drill is capable of going way deeper than required 1 meter. We decided to call it a day.
We moved separate bags of ice chips into a container. These will be transported inside a freezer from the Antarctic and all the way to NASA Ames for analysis.
We reviewed all our goals. Our first goal was to show remote operation of the drill and we demonstrated it in McMurdo when a number of 5th graders operated a drill from California. We then had to drill autonomously to 1 meter in ice cemented volcanic tephra (a lunar analog). We did that outside of McMurdo, which lies on a slope of an active volcano, Mt Erebus. We also had to drill to 1 meter and collect samples of ice-cemented ground and we drilled not one but three holes. And finally, instead of drilling a 1 meter hole in massive ice, we drilled a 2.5 meter hole. All our goals were achieved and we decided to pack up our drill for shipping back home to Pasadena, CA.
Our next field trip will be in the Arctic in 2011, but we will be back here in Dry Valleys in 2012. Till then!