Inspections of space-flown hardware clearly show evidence of numerous impacts by small, high-speed particles. Thousands of impacts were observed on the Space Shuttle orbiter fleet. Returned hardware from the International Space Station (ISS) as well as pictures of the exterior of ISS show evidence of thousands of these impacts. All spacecraft get impacts, but fortunately, most of these are small.

There are two types of impactors. The first type is the naturally-occurring "micrometeoroid" particle. The second type is the "orbital debris" particle. Collectively, these are known as "MMOD."

While they may seem like the same threat, they are not. The meteoroid particles orbit the Sun, can have higher impact speeds but are also generally less dense than orbital debris. Orbital debris particles orbit the Earth, are slower but generally have higher densities than meteoroid particles and can be very damaging. Also, because they differ in their orbit characteristics, they approach spacecraft from slightly different directions.

To improve crew safety and mission success by designing spacecraft structures that can withstand high-speed impacts of MMOD. These designs are used along with an array of advanced analytical tools to estimate crew and spacecraft MMOD risk. Knowing which spacecraft components drive the MMOD risk can then be used to identify mass-efficient shielding solutions to reduce MMOD risk to an acceptable level.

The NASA Hypervelocity Impact Technology (HVIT) team has analyzed many spacecraft and conducted thousands of hypervelocity impact tests since its inception almost four decades ago.

The HVIT team consists of a small group of dedicated engineers, scientists, technicians, and managers who are experts in the areas of materials science, impact physics, computer science, chemical engineering, structural mechanics, probability and project management.