Super Galaxy

grabcad

SUPER GALAXYDear everyone, I would like to explain the thought process that went into designing the 'Super Galaxy' bucket drum seen above. The following description and files shall be considered as my participation in the NASA Regolith Advanced Surface Systems Operations Robot (RASSOR) Bucket Drum Design Challenge.1 - Building upon Rassor 2.0Considering the time spent developing the bucket drums on Rassor 2.0 and the overall excellent feedback from the design team, I felt that capitalizing on their acquired knowledge was the way to go. This will save them time modifying (or rebuilding) their existing prototype and will not throw away their former learnings, only expending on them, enabling the team to better assess the feasibility of the proposed designs. Note : This is my point of view and how I tackled the problem, but I saw very promising yet radically different designs among participants :)Therefore, after reading through the team's reports and comments on the original Rassor 2.0 design, I decided to keep the external shape (two semi-ellipses), the configuration (4 sections in one bucket, with 45° angle between them) and the teeth. The latter have been described as efficient grippers once they contact the regolith.From there, I was free to design the interior and tried to minimize complexity and mass.2 - List of parts and RenderingsScoop - A curved sheet of carbon fiber / resin, 2mm thick.Baffle - A curved sheet of carbon fiber / resin, 2mm thick.Stand-Off - A curved sheet of carbon fiber / resin, 1mm thick, OR a 3D printed titanium part considering the location (right in front of the entry). Titanium preferred.ZAG - Set of 4 parts: *two V-shaped folded laser cut sheet of aluminium (or 3D printed out of titanium depending on desire), 1mm thick.*two U shaped folded laser cut sheet of aluminium (or 3D printed out of titanium depending on desire), 1mm thick.Plate - A laser cut sheet of aluminium, 2mm thick.Plate_End - A laser cut sheet of aluminium, 2mm thick.NOT SHOWN in the renderings: Rivets to hold certain parts (holes are however here);Flanges on the carbon parts (in order to fit them into the panels) are also missing;Teeth on the scoops are missing (they are similar to Rassor 2.0). Teeth could be added on the outside (to catch regolith from the Moon) and on the inside (to catch regolith from the interior volume). See why in 'Principle' below;Vertical slicers before the entry need to be added to prevent larger rocks from entering (which would be quite a strong problem since my design follows a strict dust/sand diet).3 - AssemblyCarbon parts (scoop and baffle) are slid into the plates as for Rassor 2.0.The V-shaped holds can be mounted directly to the carbon parts (between scoop and baffle) before these are mounted onto panels.The U-shaped holds are directly mounted onto the panels prior to sliding the carbon parts.NOT SHOWN in the renderings: Individual segments of drum are to be better fixed, just as in the inside of Rassor 2.0. 4 - PrincipleThe regolith enters from the scoop and will exit from the window opening -> The way-in is not similar to the way out.Rotating in one direction, the bucket drum is able to scoop the regolith which is then immediately redirected as the scoop rises in altitude. This allows the scooped regolith to be dumped around an empty volume in the drum (which would be top left if the drum was rotating counter-clockwise). This geometry will allow continued filling toward max capacity when only this region remains to fill in the rotating drum.Before entering the main volume and right after being redirected, the regolith has to go through a region of angled flanges (called ZAG in the step files) which acts as some kind of Tesla Valve. Regolith can easily pass in one direction (filling) but not that easily in the other (regolith trying to escape). Here, the regolith will have to fill the volume behind this succession of angled flanges before exiting, which is hardly possible at the given rotating speed: the regolith simply does not have enough time to escape. Holding a static position also prevent the regolith from falling too much during transfer to dumping site.Looking at the exit, still in the filling rotation, this region cannot be reached by the regolith as the drum rotates. It is simply too narrow and with a strategic position of the internal opening. This has been noticed after prototyping (the prototype is not the final product but helped understand certain design features) -> https://photos.app.goo.gl/BuTbPQbnTmtFPJ4XAAll this allows for a comfortable filling of the bucket drum.Now rotating in the other direction, the former entry point cannot be reached thanks to the ZAG region and the exit channel now can scoop the regolith from the internal volume. It would actually be a good idea to add some teeth here as well ! The efficient scooping of the regolith was noticed also from the prototypes, as the at-the-time not closed ZAG region was letting regolith out crazily... This insane power was reused for unfilling instead :)There you have it ! The regolith gets captured, redirected, passes through a simili Tesla valve with no permission to come back, and is then scooped from the inside in order to be dumped out.Extra note: When going through the ZAG, if the regolith takes too long and not all of the scoop is dumped inside, the ZAG itself has the power to hold the remaining regolith until the following revolution. Every scoop might not make it in the first rotation but surely on the second ! (and the next scoop follows by pushing the previous one).RequirementsMaximum total width of scoops engaged at any given time: 80 mmMaximum bucket drum mass: approx. 3.1 kg (3.5 max with missing elements not shown in renderings)Maximum bucket drum diameter: 450 mmMaximum bucket drum length: 330 mmA minimum volume of regolith captured: approx. 25 liters, filled at 70-75%