| General > General Technical Chat |
| Starship is now Stacked |
| << < (3/6) > >> |
| David Hess:
--- Quote from: Gyro on August 08, 2021, 06:54:48 pm ---Presumably the engine bells are still susceptible to, err, bell mode resonances, also seen in speaker cones. Are these addressed by damping and reinforcing rings? Although I can't see any, and they look pretty thin. I'm just visualising the closely spaced outer ones clanging together! --- End quote --- I have read various accounts of rocket design and they do all kinds of things to prevent that sort of problem including avoiding power ranges where known resonances are excited. I recently ran across a similar problem with my new workstation. It has 3 x 140mm front fans for filtered positive pressure cooling and from previous experiences, I expected that having all three fans running at the same RPM would cause annoying audible resonances and beat frequencies. So I planned ahead of time to force the fans to spin at slightly different speeds and testing showed that solved the expected problem which did develop. In retrospect I am surprised nobody makes PC fan controllers with this as a feature and it got me dreaming about the best circuit to phase lock multiple fans to slightly different frequencies. |
| rdl:
Rockets do not sit on the engine bells. There is a structure at the base for this purpose and there are hold down clamps attached to keep everything steady. The engines hang from this structure. At launch when the engines ignite, the hold down clamps keep the vehicle in place until the system is confirmed to be working correctly. Only then is it released. |
| Gyro:
--- Quote from: rdl on August 08, 2021, 07:38:08 pm ---Rockets do not sit on the engine bells. There is a structure at the base for this purpose and there are hold down clamps attached to keep everything steady. The engines hang from this structure. At launch when the engines ignite, the hold down clamps keep the vehicle in place until the system is confirmed to be working correctly. Only then is it released. --- End quote --- It would be kind of difficult to get them to light if they did! ;) You could certainly say that the rocket is sitting on the engines when in flight though. |
| Gyro:
--- Quote from: David Hess on August 08, 2021, 07:29:55 pm ---I have read various accounts of rocket design and they do all kinds of things to prevent that sort of problem including avoiding power ranges where known resonances are excited. --- End quote --- That must be a hell of a juggling exercise, there will be various overtone modes, as well as the fundamental. Presumably the combustion is a fairly broadband noise source too. I'm glad it's not my problem! Have they done a test firing with all 29 engines running yet? I think I would have remembered that one. Maybe it's the sort of test that you can only do in the air! |
| mrflibble:
--- Quote from: Gyro on August 08, 2021, 08:17:08 pm ---Have they done a test firing with all 29 engines running yet? I think I would have remembered that one. Maybe it's the sort of test that you can only do in the air! --- End quote --- Nope, not yet. Of the 29 engines currently fitted, 5 have not been subjected to a test firing at all. Booster 4 is expected to be moved back to production site for additional work, somewhere during the coming week. Until those 29 engines perform their simultaneously controlled explosions, here's some Saturn V static firing instead: https://youtu.be/-rP6k18DVdg?t=183 |
| Navigation |
| Message Index |
| Next page |
| Previous page |