Utilizing regolith on the Moon or Mars, especially to refill propellant for rockets to get back off the surface, is a common theme in the more engineering-minded space exploration community. There have been plenty of proof-of-concept technologies that could move us toward that goal. One of the best supported was the Regolith Advanced Surface Systems Operations Robot (RASSOR). Let’s take a look at what made this project unique.
It was initially conceived at Swamp Works, NASA’s version of Skunk Works, the famous Lockheed Martin development facility that worked on the SR-71 Blackbird and F-117 stealth plane. So far, it has gone through two iterations, known as 1.0 and 2.0, released in 2013 and 2016, respectively.
RASSOR consists of a chassis, a drive train, and two large bucket drum excavators. The excavating elements are on opposing sides of the rover, allowing the system to cancel out any horizontal forces caused by the excavating activity. On Earth, those horizontal forces would be offset by the physical weight of the digging machinery. Since weight is a precious commodity on space missions, this force-canceling technology is arguably the most crucial innovation in the system.
Credit – NASA Video Collection YouTube Channel
The RASSOR 2.0 prototype had several design goals, but it’s probably most helpful to walk through a use-case scenario. According to the soil samples collected by Curiosity and other rovers, around 2% of the regolith on Mars is water, even in the relatively “dry” regions outside the poles. Collecting that water could help refuel rockets and supply settlements with drinking water, radiation shielding, or water for agriculture.
NASA commonly uses a mission structure involving four astronauts on a journey to Mars. In a paper describing the 2.0 version of the robot back in 2016, the authors, including Robert Mueller, the founder of the Swamp Works facility and a doyen of ISRU research, describe a mission structure that would see RASSOR mining 1,000,000 kg of Martian regolith per year and supplying 10,000 kilograms of oxygen to the mission.
To do so, it would utilize a lander with processing capabilities for separating the useful parts from the chaff and would trek from the lander site to the regolith collection site about 35 times a day. With a charging cycle that would take about 8 hours a day, that would leave upwards of 16 hours to continuously mine the surface of Mars for these valuable materials.
The paper goes on to describe the design process for the RASSOR’s various subsystems, including the powerful actuators that make up the majority of the weight of the system. They also used 3D-printed titanium to make the bucket drum excavating tools, which required some ingenious machining by Swamp Work’s machinists.
But in the end, they did make a working prototype. They tested it with improvements like a 50% drop in weight and an autonomous mode that utilizes simple stereo-vision cameras. The team believes this project is ready to move on to the next phase, taking a step closer to making it a reality.
That paper, however, was published eight years ago. A relatively detailed internet search doesn’t produce any results for RASSOR 3.0 other than a brief mention at the end of the 2.0 paper. So, for now, it seems the project is on hold. However, another NASA project, the Lunabotics Challenge, keeps university teams working toward effectively mining regolith for us in ISRU systems. Maybe one of those teams will pick up where the RASSOR team left off – or come up with a completely new design. We’ll have to wait and see.
Learn More:
Mueller et al. – Design of an Excavation Robot: Regolith Advanced Surface Systems Operations Robot (RASSOR) 2.0
UT – Japan Tests Robotic Earth-Moving Equipment in a Simulated Lunar Jobsite
UT – NASA Wants to Learn to Live Off the Land on the Moon
UT – What is ISRU, and How Will it Help Human Space Exploration?
Lead Image:
CAD model of the RASSOR 2.0 excavating robot.
Credit – Mueller et al.
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