NASA Lunar sampling rotating sieve

grabcad

OPERATING PRINCIPLESSince the lunar soil can have variable composition I think that a dedicated device can not meet the technical requirements with a single attempt, but must be flexible and able to repeat the evaluation cycle several times until it reaches the intended goals.(See the attached block diagram)It is unthinkable that with only 500 grams it is possible to build a rover able to move autonomously in safety over the moon, and then the device will be on board the main module and will use its robotic arm to take samples from the ground, load them in the sieve, and close the hermetic container.On he earth the sieving of gravel in its various grain sizes is based on the concept of generating random movements so that gravels can fall by gravity into the holes of the sieving mesh.These random movements can be obtained by centrifugal force, vibrations. mechanical action or overturning.Given the small size of the device I think that the use of centrifugal force is not suitable because the grains can be projected on the wall and simply clog the holes.Vibrations can also fail, because the vibration force impulse would be greater than the reduced action of the lunar gravity acceleration, and the resulting component would not bring the grain to fall into the passage hole.Because of the low power available to electric motors blade rotating devices can lock against a stone that fits into an hole.I therefore think that as an alternative only the concept of overturning remains, which is widely used in rotating sieves. The important thing is that the rotation is fairly slow so as to give stones time to fall into the appropriate hole under the action of reduced lunar gravity.DESCRIPTION OF THE DEVICE The device is built for the most part by laser-cut aluminum sheets bent and connected by bolts .The sieve drum is in aluminum drilled with laser, is driven by a stepper motor and centered in rotation by a Teflon ring.The mass comprehensive of rotating sieve, motor, evaluation bowls, and collecting stool is 490 grams.OPERATIONThe robotic arm then collects a soil sample using the appropriate stool, digging up to a depth of 10 cm and loading it into the rotating sieve.The perforated drum rotates slowly, separating the components in the various grain sizesRocks larger than 2 cm simply fall out of the device, while the other two sampling fall into evaluation bowls.At this point the visual judgment of an expert geologist is decisive.It will be done remotely via the camera mounted on the lunar module.If the evaluation is not satisfactory, the robotic arm will affix the bowl and empty the contents. If it is satisfactory the sample will be poured into the sealed container.The first evaluation will therefore concern the big stones (10-20 pieces size about 1-2 cm) and then the filling will be completed with the remaining powder of the second bowl.The process will be repeated until the required results are obtained.SEALED CONTAINERAlthough it was not requested, I wanted to design the hermetic container that will bring the samples back to the earth.It consists of a vase and a bayonet lid selaed with a Kalrez O-ring coated with a Teflon film.Since the container is closed on the Moon in vacuum conditions, when it returns to the Earth, it will have to withstand the atmospheric pressure acting on the outside.I therefore enclose an FEA evaluation.The lid has four clamping notches with identical dimensions to a SKF ring nut KM29. It can therefore be opened with the appropriate SKF key and closed by te robotic arm.The deep drawing vessel made of aluminium has four ribs that contribute to vacuum stability and are used to hold the container in place when the lid is screwed on.it is then housed in an appropriate hole of the lunar module.The rotating screen can be left on the moon and instead one or more containers will return to the earth.That's all, so I wish NASA good luck for the success of this experiment.Best regards