Overview of Status of Analysis, Design, Fabrication, Tests, etc.
Some discussion is being had about the simulation dynamics possibly being incorrect; we have had multiple meetings this week to address the issue.
In the meantime we are sourcing as many parts as possible in order to not delay the design process.
Accomplishments from Previous Week
Bucket attachment design completed
Counterweight attachment design completed
Goals for Next Week (list names after each item). Use specific and measurable objectives.
Decide which design to use (swinging bucket vs fixed) (ALL)
Look into simulation of bucket forces on some sample material and FEM in SimScape to validate the stratification shown in the diagram of 3 lab centrifuges (see Pictures.pdf) (Peter)
Source more literature to show precedent for dynamics (David, Labiba, Clara, Nicholas)
Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
From Tuesday 4/28 (morning) meeting:
Not sure if bucket design will really provide a more accurate replication of the actual rocket profile, as it doesn't undergo acceleration strictly normal to box (Twyman)
Fixed arm might be suitable for SpaceTango testing purposes (Twyman)
If no bucket, resultant vector will rotate around instead of being constant, no off-axis acc. wanted bc rocket acceleration is fixed in one direction (Erik)
3 possible solutions (Twyman)
Fixed at end of arm (original design)
Non-controlled bucket at end of arm (free swing)
Actively controlled bucket angle (more difficult to control)
As long as resultant is same magnitude, should be fine? Erik is concerned about the microfluidics because payload does maintain same overall orientation → might not deviate that much as it would with a fixed arm (Erik)
From Friday 5/1 meeting:
can only recreate microgravity (drop towers, drop something in vacuum) or parabolas in an airplane (Twyman)
during rocket flight, as velocity increases, centrifugal force increases until it equals the gravity pulling on you (Twyman)
butt joint could have a lot of stress concentration in an Estop (need to look into stress concentrations under braking loads) (Twyman)
Instructor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
From Monday 4/27 meeting:
Acceleration would have different terms
Spikes in dtheta dt plot is nontrivial
since swing arm length is relatively small wrt arm length, could be pretty similar to fixed case
From Tuesday 4/28 (afternoon) meeting:
we have been assuming that gravity’s effects incorrectly; it’s feeling gravity downwards but not accelerating downwards → can’t compare dynamics and static; i.e. cells will always feel gravity, shouldn’t compare with centrifugal
Acceleration in simulation may have been incorrect? (centrifugal is toward axis, not along swinging arm) → should be fine, see swinging amusement park ride physics problem
Opening of double pendulum with slow opening does not maintain direction of resultant acceleration, is correct
Finding angle (theta) is a different problem, but acceleration is not preserved
From Friday 5/1 meeting:
more literature is needed to establish precedent
Peter will look into simulation of bucket forces to test our assumptions
Comments from Other Students in the Class (indicate date of comments and if via email or in person)
N/A
Risks and Areas of Concern
The simulation used to make the previous weeks' design decisions may have been incomplete/incorrect
Resources or Information Required but not Available
Literature to show precedent for dynamics of the swinging bucket centrifuge design vs a fixed boom.
Schedule
Describe upcoming milestone
Update Gantt chart.
Budget (list amount spent and amount remaining)
N/A
Progress on Report and Webpage
Rough draft due Sunday 5/3/20