NASA RASSOR Drum Design

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Human: NOTE: ALL SIMULATIONS WERE CONDUCTED UNDER LUNAR GRAVITY AND 20RPM, BUT HAVE BEEN ACCELERATED 2X FOR ANIMATION PURPOSESSpecifications of the design:Up to 37L fill capacity94% fill efficiency4.98kg with carbon fiberFills up in 4-5 rotations, or 12 - 15 seconds (3.08 ~ 2.46 L/sec)Maximum width of scoops engaged will be under 175mm as long as the drum remains half or less immersed in regolith.The design for the NASA RASSOR bucket drum was created with several key objectives in mind:1. Simplicity (durability, and ease of assembly)2. High fill capacity and efficiency3. Fast pickup process4. Minimal spillage during holding5. Fast unloading processTo achieve simplicity, the first decision made was to eliminate all moving parts inside the design. Since the bucket drums will be operating far away from earth and any maintenance, they cannot be too complicated mechanically. The design is therefore optimized for simplicity with minimal mechanical components (See 5th rendering). In the case of the spikes, a one-piece design was chosen, with added aluminum caps to increase durability. (See 6th rendering). The drum itself is also modular, divided into 4 congruent pieces that are put together.Simplicity played a key role in achieving high fill capacity and efficiency as well, as simple designs without many complicated parts will likely have a larger area dedicated to storing the picked up regolith. To increase fill volume, the baffle size was decreased, and multiple hollowed-out sections were incorporated.When it came to a faster pickup process, a dilemma arose because larger scoops would enable faster digging, but if the drum emptied too quickly, the exit had to be large as well. This meant that the drum would lose regolith during holding. To avoid this issue, very large scoops (half of the diameter of the drum) were included and arranged within 45 degrees on the drum exterior. This allows for faster digging while maintaining extremely low spill rates when holding if the scoops are angled up.To make the unloading process faster, it was ensured that the way out was not a bottleneck. A useful analogy (credits to @Marvin Green) is "A widening passage when filling becomes a narrowing passage when dumping. It would be like filling a bottle with sand and then trying to dump it out without it clogging." So, the way out was made as straight and unobstructed as the way in, leading to a fast dumping rate.More details will be added to the design soon.