Planetary Penetrators
What are Penetrators?

What are Planetary Penetrators?

Kinetic micro-penetrators are very light self-contrained spacecraft that impact the surface of other worlds at high speed and bury themselves into the surface a few metres. The advantage is that because of the low mass, they are potentially a low cost way of exploring other worlds.

The UK Penetrator consortium is aiming at launching a Lunar probe that weighs around 13Kg with an additional similar mass to decelerate and align it to survive impact at around 300m/s (equivalent to around Mach 1 on Earth).

Scientific Instrumentation

Although the specific set of scientific instrumentation would be targeted to the planetary body under study, it would very likely contain a subset of the following.

  • Seismometer
    Providing key information about the interior of the planetary body, and geologic/seismic activity using simultaneous measurements of seismic waves that travel through the lunar interior.
  • Chemical Sensors
    Detection of water and organic chemistry in samples of the lunar regolith acquired using a micro-sampling tool.
  • Accelerometer
    Providing information about penetration depth and the mechanical properties of the surface material.
  • Geochemical Analysis
    Provide ground truth for remote sensing XFA and multi-spectral imaging.
  • Thermal Sensing
    Investigation of surface and sub-surfaced temperatures, thermal conductivity of sub-surface material and heat flow determination. Provides clues about the interior differentiation and composition of the target celestial body.
  • Descent Camera
    For determination of impact site morphology and location.
  • Beeping transmitter
    Doppler shift measurements from earth could determine horizontal crustal movements.
  • Ground Camera / Microscope
    For mineralogy and astrobiology, via a camera viewing through a small diamond window in the penetrator and a small LED light source. Astrobiology through detection of UV fluorescence of RNA/DNA biological material and correlated imaging.
  • Magnetometer
    Doppler shift measurements from earth could determine horizontal crustal movements.
  • Radiation Monitor
    To categorise the sub-surface radiation environment for possible future manned bases, or to determine the feasibility of life.

Generic Mission Architecture

Generic mission architecture for penetrating probes is as follows.

  • (A) Cruise Phase
    Penetrators are delivered to the celestial body aboard a mother-craft which provides accommodation, power and data/command facilities. The vehicles are given periodic health and status checks and battery charging.
  • (B) Probe Deployment
    Penetrators are ejected from the mother-craft, which retains the ejection mechanism. Images from the descent imager can provide confirmation of separation.
  • (C) Descent Phase
    If deployed from orbit, a solid rocket motor (SRM) fires to decelerate the vehicle. The probe’s velocity and attitude are controlled by thrusters, which provide a nominal impact velocity of 200-300 m/s and orientation within 8 degrees of the velocity vector. The mother-craft maintains communication with the probe, for uplink of status information, descent imaging and atmospheric data. The SRM and attitude control system are separated just before impact.
  • (D) Impact
    The penetrator strikes the regolith and comes to rest a few meters under the surface. The accelerometer measures the deceleration, allowing the penetration depth and information about mechanical sub-surface structures to be determined.
  • (E) Sub-Surface Operations
    The craft is powered by a battery for its nominal sub-surface mission. Initial observations with chemical sensors are followed by extended observations using the onboard seismometer and heat-flow experiments. The mother-craft provides continued communications support.

Currently, several possible mission architectures are under study that, if successful, would put the UK at the forefront of planetary exploration.

See the website of the penetrator consortium.