Background and Motivation
In 2022 KOTS had some stability and launch rail velocity problems partially caused by not knowing the weight of rocket components until very close to competition (after the fins had been sized). Another cause was uncovering the lack of thrust at the beginning of the Kismet engine burn which decreased off rail velocity by an alarming amount.
In general, further rocket integration and optimization of flight profile has been identified as an area with good potential for growth in the future. Both to reduce likelihood of integration mishaps as well as to improve overall design consistency and focus effort on high reward projects.
Project Description
This project is to create a cycle where:
Subsystems create design concepts and do design work as before
Subsystems and engine team estimate length, mass and engine performance at specific check-in dates (most likely providing high, low, and predicted values). Note engine team would be creating RSE files at each cycle.
This data is fed into various OpenRocket simulations determining apogee, stability, acceleration (for loads), velocity (off launch rail and throughout flight), and any other flight characteristics of interest.
Load simulations run using acceleration data
Resulting simulations are used to write a short digestible report about the results and the highest value design focuses to be disseminated throughout the team and the team leads.
Subsystems are aware of the rocket as a whole and how any changes impact the overall system.
Cycle repeats until design lock with length and mass estimations becoming more and more precise as design is finalized.
A minimum viable product if time/team cooperation is difficult, is to offer case by case simulations to determine how various design changes already under consideration would affect the rocket. This could also be done at the same time as “cycles” however would not be ideal to do alone as it is likely to miss the larger system.
For sure this will be done for fin sizing as in previous years.
Requirements
Must gather information from all rocket subsystems with reasonable confidence that the data is within some accuracy. To ensure this accuracy the method must be easy to understand for both experienced team members and brand new members.
OpenRocket/RSE simulations must predict how changes to rocket length, weight, and engine performance affect rocket performance.
OpenRocket/RSE simulation process must be streamlined enough to be done regularly.
Loads analysis must be done at each cycle
Reports must be written which are extremely digestible and accurately represent the data. (giving effective actionable information to team members)
Regularly scheduled cycles must be implemented without significant schedule slip
Minimum scope of this project is to analyze design decisions using OpenRocket and RSE file generation to help inform team members about high value changes
Maximum scope of this project is to create a project management tool/system to consistently check in on overall key integration parameters (mass, length, engine performance) and disseminate actionable, easy to understand information to drive design decisions while also considering case by case changes to the design.
Required Documentation (Insert links when created)
Instructions for subsystems to submit mass & length information Instructions for Adding Data to Length & Mass Tracking Spreadsheet
Spreadsheet to track information for each cycle. https://docs.google.com/spreadsheets/d/1poRCKzhNSZfQRoP2KN2xZRwuLLkZauFutRtuNmLCAjw/edit#gid=0 https://docs.google.com/spreadsheets/d/1JRF1jpii5KTwKIDkutjp5YCkuJp4Eh8oAxtDvMn6QBs/edit?usp=share_link
Documentation on overall process (design doc) https://uwaterloo.atlassian.net/wiki/spaces/ROCKETRY/pages/edit-v2/43224662139
Mini reports at each cycle. https://docs.google.com/document/d/1llZpvqR2ySNqaO2CX9GxES7BDVpa7x_HQdchj9B6Eb8/edit?usp=share_link
Document/s to track OpenRocket and loading analysis simulation outputs.
Cycle 1 what we are simulating: Cycle 1 what are we simulating:
Cycle 1 simulation data:https://docs.google.com/spreadsheets/d/1O7EI6IzpHXXCWCLqXju4nxJKGlHdr366o6npeITfkjM/edit#gid=0
Cycle 2 what we are simulating What we are simulating in Cycle 2
Deliverables Timeline
Startup work: (starting early sept. ending at end of sept.)
Create document/system to track mass and length and collect input from the subsystems (Sept. 18 tentative)
Get feedback on it and improve it. (until end of sept.)
Get input from the subsystems alongside the first length/mass data about what scenarios they would like to see simulated
Cycle 1: Starting 1st week of October Ending end of October
Predicted 1.5 weeks to gather data from subsystems (with enough advance warning). Data due entered into spreadsheet by Oct. 12
Predicted 1 week to run open rocket simulations.
Predicted 1 week to write mini report.
Total 3.5 weeks
Results influence the detailed design
Cycle 2: Starting 1st week of January, ending end of January
Same schedule as above
Results are used to finalize designs for the CDR, finalize fin size
Fin sizing finalized (Last year January 11th)
Cycle 3: Starting last week of March, ending mid April
Should incorporate all final design masses and some fabricated part masses
Same schedule as above
Results are used for final project report
Cycle 4: Once the rocket has been completed
Represents the as-built results with fabricated masses
CDR: Early February
Design Log:
10-13-2022
Conversations in slack about changing datums and datum use in general occurred recently. See slack for more details. The short is that we should reconsider the datums before the next cycle.
Overall the project is going well. Propulsion didn’t quite meet the deadline for input due to busyness but basically everyone else did. Now on to simulations.
Remember to get the lengths of the sections for the deadline.
10-14-2022
Almost finalized the spreadsheet just waiting on last lengths to be put in by roman now which changes a few CG values
Realizing won’t account for CG changing due to min/max mass scenarios. Determined this should be fine for this cycle.
Created list of what we want to simulate, and excel to track data
Decided to use RSE files from previous simulations (early KOTS 2023 simulations) as new ones were not created for this yet. Trying 100% thrust, 120% and 150% as decided by Joel and Aaron.
01-28-2023
Just realized I haven’t put updates here in forever.
We finished cycle 1 essentially on estimated schedule and published the mini report.
The cycle 2 data took a little bit longer to gather and be confident in because of a lack of work over the holidays and also due to wanting to be very confident in this data but unfortunately a lot of designs on the rocket are not yet at a place where they can give us good estimations. Also the SF got delayed a week until today.
One unfortunate part of this is that the 3d printed metal fill bulkhead design needed to be sent away for printing in January around the 24th. For this they needed fairly good loading calculations so we decided to add a cycle 1.5. This used the data currently gathered alongside some rough estimations of: engine data, airframe weight sections and other sections in general. This was then simulated with two types of fins (clipped delta and trapezoid) based on research about what was the best shapes. This generally showed that clipped delta was better for apogee and also that the fin size of last years rocket is actually a good estimation of what we will need this year. This is new information as previously it was thought it would be able to be smaller than last year. However I think due to a length reduction and possibly other factors the inherent stability of the rocket has decreased. We are currently planning on completing cycle 2 around mid February according to the plan laid out in this document https://docs.google.com/document/d/1JNvpdeczEOeFuUGfQ1QNFMN_b9wIcHwRmjX0BIFrfug/edit#.
A weather review of New Mexico conditions was also completed to analyze the conditions we are using in our simulations and for further use as to weather variation in stability. This is located https://docs.google.com/spreadsheets/d/16RH75F2kThyLBTv0jcvQgWOC8h9-sMPgf0onBELOxmY/edit#gid=0
Sensitivity analysis was done on various nosecone and boattail shapes to determine if they need to be taken into consideration at this point. Neither significantly changed stability. Nosecone shape can be improved by changing to a power series with 1/2 shape parameter. This would improve apogee by around 400ft however this is most likely not going to be done as remaking nosecone moulds is prohibitive in both team member time and manufacturing time. The boattail various shapes had very little effect on flight with a perfectly square extension of the rocket reducing apogee by around 300ft and various curvatures not making a large impact.
A big drop in stability was noticed around the end of the engine burn which makes our lowest stability at a very different time than previously. The cause of this difference is mostly unknown.