By Dr. Gary L. Deel, Ph.D., J.D.
Associate Professor, Wallace E. Boston School of Business
Space exploration science and research is often a highly sophisticated, specialized, and intricate undertaking. In the mind’s eye, one often imagines scientists and engineers at some high-tech NASA facility – working in clean rooms, dressed in full hazmat suits, and carefully assembling super-sensitive, precise instruments on rockets and spacecraft.
Making piles of dirt is not something that necessarily comes to mind when you think of NASA. However, this work is exactly what the Exolith Lab in Orlando, Florida, is doing, and their research is vital to future space exploration missions.
The Exolith Lab is a research institute that manufactures simulants of soils from other celestial bodies. It is a subsidiary of the University of Central Florida (UCF), partially funded and supported by NASA and other private space research ventures.
The Exolith Lab uses the simulants it creates in-house for its own science experimentation. It also sells these simulants in made-to-order quantities to government and private research facilities for various applications.
You might wonder why a research facility would ever want to buy dirt. The answer has to do with the way future space missions plan to land on and explore different celestial bodies in our solar system.
Ground Soil Composition Is a Consideration in Any Spacecraft Landing
Successful entry, descent, and landing (EDL) on any planet or moon requires careful engineering around several factors, including gravity, atmosphere, and other variables. But an important component of a successful landing is consideration of the composition of the ground soil upon which a spacecraft will land.
Ground soil considerations include the type of materials making up the soil, the size of the particles, the density of the soil (how tightly or loosely packed the dirt is), the moisture content (if any), and many other dynamics. Unfortunately, given the distances and expenses involved, we don’t often have the opportunity to test theories on site.
So the best we can do is try to simulate the circumstances of a spacecraft’s landing environment here on Earth. This effort involves the production of simulated dirt – using crushed rocks and other raw materials – that closely resemble the ground soil in target environments.
With lunar soil, for example, we have the benefit of actual regolith samples that astronauts recovered from the Moon during the Apollo missions and brought to Earth. So we can use an analysis of those regolith samples to simulate dirt that is very similar in composition and characteristics, since all of the same elements can be found on Earth.
We Have Yet to Capture Soil from Mars or Other Locations
Unfortunately, we don’t yet have actual samples of soil from other target locations like Mars. There are proposals to retrieve some samples in the future, but they are expensive and speculative at best for now. However, that doesn’t mean we can’t make reasonably accurate simulants of soil from Mars and other celestial bodies from scientific research.
For example, the research rovers on Mars have engaged in intense study of Martian soil, including its composition, density and other measurements. From this data, we can get just about as clear a picture of what Martian dirt is like as we can for the Moon dirt that we have from the Apollo missions. These Martian missions have allowed us to manufacture pretty accurate exolith simulants without having to actually retrieve them.
Why Do We Need This Simulated Dirt?
But why do we need these simulants of dirt? There are multiple applications.
For example, let’s suppose you want to know what kind of impact crater a lander will make upon touchdown and how deeply a spacecraft might sink into the soil after making contact. This information is important for understanding the dynamics around spacecraft weight, footings and stability.
What about dust clouds? If a lander is using retrorockets to assist in the EDL process or if it makes an impact with any kind of significant velocity, dust will inevitably be kicked up off the surface of where the spacecraft lands. This dust can cause substantial harm to a spacecraft by interfering with its sensitive electronics and instruments. So understanding how much dust should be expected during a landing is important, too.
Finally, what about the maneuverability for landers that are intended to move around after landing? These spacecraft are the kinds of “rovers” that rely on wheeled propulsion to navigate the surface topography of a planet such as Mars.
But to properly engineer wheels and propulsion dynamics, researchers must be able to test how different designs will work in situ. For example:
- How loose is the soil?
- How deep will the wheels dig in?
- What is the best shape of tread in order to maximize traction?
With the type of exolith simulants that the Exolith Lab produces, test beds can be built. These test beds allow mockups of landers and rovers to be tested in environments that are about as close to the conditions expected on other planets and moons as can be reasonably simulated here on Earth, at least in terms of surface soil composition and conditions.
Other Factors to Consider in Spacecraft Landing
Of course, there are other factors to consider that are not quite as easy for researchers to simulate. For example, on the Moon, the surface temperatures fluctuate between roughly -280° F (in the shade) and 260° F (in direct sunlight). These temperature variations can be important to EDL conditions, but they cannot be easily replicated in an Earth lab without expensive equipment and controls.
Another factor that is even more difficult to simulate is differences in gravity. For example, the gravity on the Moon is just 17% of the gravity here on Earth. This difference is virtually impossible to simulate on Earth, unless testing is done underwater or in an airplane in perpetual descent – neither of which are ideal or practical for laboratory experimentation.
But of course, gravity affects all kinds of spacecraft characteristics around landing, impact, vehicle weight, traction, dust emission and many other important variables. So this consideration of gravity is important.
Using Simulated Dirt to Increase Space Mission Success Is Worth the Time and Effort
The exolith simulants produced by Exolith Lab allow NASA researchers to get one step closer to actual in situ conditions and to substantially increase their odds of success during spacecraft missions. Given that space missions tend to cost anywhere between millions and billions of dollars, this research work – which is extremely technical and nuanced in its own right – is well worth the time and effort spent on it.
The moral of this story? Never underestimate the value of a pile of dirt.