Planetary penetrometry

In space penetrators have been used for years for scientific and technical purposes. Penetrated objects may be small Solar System bodies - asteroids and comets, and large ones - planets and moons.

The first group of objects is characterized by a lack of atmosphere (vacuum), microgravity conditions, low temperatures and sometimes high-speed rotation of small bodies.

On the planets and moons weather conditions can vary greatly, from vacuum to a dense atmosphere, and the gravity field of these objects is substantial.

For penetration of any of the space bodies, mechanical properties of the soil are essential: its structure, strength, density and porosity.

Space penetrators are particularly useful for carrying out the following under-the-surface studies:

- in situ chemical and mineralogical analyses,

- thermal analyses (temperature profile, thermal conductivity),

- soil mechanics,

- seismographic studies,

- electric and magnetic analyses,

- radar penetration (GPR).

 

Penetrator with capacity measurement is often also referred to as the penetrometer.

The technical tasks of penetrators include:

- sampling the soil at various depths and delivering it to the surface,

- transport capacity – insertion of the other components in the ground (the role of the prime-mover),

- anchoring of the landing objects.

 

The most general classification of penetrators divides them into two groups: very fast impactors (kinetic penetrators) that as bullets have very high initial velocity and use the accumulated kinetic energy to drive themselves in the surface; and stationary penetrators, which use other ways to penetrate the soil.

The term "stationary" is justified by the fact that these kinds of penetrators have their base at the space vehicle - usually in the form of a retractable platform. The base is equipped with starting mechanism, power source, depth gauge measuring, inter alia, the length of cable, and other necessary supporting subsystems. The stationary penetrator even after insertion into the surface is still very close to the base and most often is powered by and communicates through the cable.

Impactors are used during missions that are not equipped with a lander. Undoubtedly, their advantage is a deep and steady penetration, but the main drawback is the huge overload, which specifically endanger the sensors and electronic components. Communication with the orbiter is only wireless.