Sunday, April 10, 2016

The Noisy Cricket Lifts Off

This past Saturday, I got to finally see our rocket lift off. But before I get into the ultimate performance of our rocket, let me recap the progress.

This project began with the goal of achieving a target altitude of 1,750 feet. We knew we were getting our choice of G38-FB (87 Ns impulse) or G40-W (97.4 Ns impulse) motors. Based on initial OpenRocket designs (not knowing what diameter body tubes, etc. we would receive), we decided we wanted the weaker motors and the largest bodies available. After choosing thusly, the project leads changed the ultimate goal to that of achieving maximum altitude. With little we could do about our parts, we opted to use only one body tube (18") plus our 9" ogive nosecone, plus juuuust enough fin for reasonable stability (1.25 calibers).

It is worth, noting at this point, that the project leads doubted our design and were quite surprised by our demonstrated stability during our swing test. This makes me think we could have gone with smaller fins, but it's too late for that now. After the swing test, I rounded our fins with some sandpaper and made some fillets with wood glue, as suggested by someone I know who has done this before. I can't say if the fillets were ultimately a waste of weight or helpful, but as two of our fins seem to have broken their initial fastening, I can't balk at a touch extra glue holding them in place.

Ultimately, the launch was successful, with our rocket achieving an apogee of 541 meters, as opposed to a predicted 600 meter apogee for a margin of error of about 10%. Most people were surprised that it did as well as it did (it looked like a midget among giants on the launchpad), so I was largely pleased, myself. We didn't get the highest apogee from among the teams, but I'm considering fixing the fins that came dislodged and dropping $20 on a new (and larger) motor to try for some serious altitude next month.

Overall, I have to admit that despite the seemingly constant setbacks and design changes, this was a great experience, and based on what I've heard from friends currently working as engineers, this was pretty typical of a design project. I'm thankful for the chance to do this and am looking forward to next semester's rocket design project.

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