One correction to what Drew said: We flew a Raven and an R-DAS over 100k' before there were *Megas. We flew the R-DAS in it's normal accelerometer-based apogee-detect mode, and it worked perfectly despite a significantly off-vertical trajectory. The Raven was configured... strangely (a combination of baro and timer that I explained in a NARCON speech <https://www.youtube.com/watch?v=2f6yomcfi1g&list=PLzAcxg87GnJ0T8JO-W9NFRiPbvDZGAC54&index=4&t=0s>). It also worked perfectly, or at least did exactly what we expected it to do. Not that any of this is especially relevant now. :)
Kip's flight did use a timer, but Keith and I both poured over the data from that flight for a long time. I don't want to speak for Keith, but I'm convinced that the apogee event would have triggered right on time, had it been allowed to. The *Megas use a Kalman filter to fuse both accel and baro data into the model, up to 100k', so I don't think the apogee detect should be all that sensitive to off-vertical flight. Casey On Thu, Jun 20, 2019 at 10:49 PM Plugger Lockett <[email protected]> wrote: > Hi Craig, > > I've done a little bit of work like this with the EasyMega board in > support of a 100k+ foot flight. The issue you'll run into is that the baro > sensor is basically only good to 100k' MSL and above that the atmosphere is > so thin that the baro readings are around the noise floor of the sensor. > You could use Accelerometer based deployment but the *Megas don't do any > integration of the data across the three axis sampling so unless you're > flying perfectly straight up it's most likely not ideal. I could be making > a complete hash of explaining this but in broad brush strokes those are the > things you need to consider. > > IMHO your best bet is to have a timer based primary and backup apogee > event configured on the *Mega board you fly. So you make sure you have a > reasonably accurate simulation and look into the time it takes to make it > to apogee. Then add a few seconds to that to ensure you don't deploy before > apogee. Ideally you'd also include some logic in the timer for added > safety, for instance a config that fires after x seconds and being above > 20,000 feet AGL. As Casey said at 100k a bit of a late (or early) > deployment isn't much of an issue as the atmosphere is so thin there that > there won't be any appreciable drag on the vehicle at that altitude to > cause a zipper or something similar. It's more important to ensure your > event works and separates the rocket so that once it falls back into the > lower thicker atmosphere it will do so without coming in ballistically. > > I know both Kip and Jim have leveraged the EasyMegas in this capacity to > handle their sustainer ignition (including altitude an tilt inhibits) as > well as their apogee events on their two and three stage flights. Before > the *Megas most people seemed to use the Ravens with the high altitude > firmware or R-DAS boards for 100k+ attempts. Both were leveraged in the > same way, as in, timer based apogee event configurations. > > Ideally you'd also configure an event for what I like to describe as an > EFU (Everything's F*cked Up) event. Basically it's nice to have an event > configured for if your flight is off nominal that would still fire your > apogee charge if something goes wrong and you don't meet the criteria for > your planned apogee event. Basically if something goes wrong you still want > an apogee event to fire, and it would make sense to configure your board to > do that if at all possible. > > > Are there any considerations for rockets exceeding Mach 3? > > Not from a *Mega perspective. ;) > > Good luck on your project! Many moons ago I was a MDRA member. Great club > y'all have there. If you have any further questions please feel free to > reach out. I'm sure I could pull up some pyro channel configuration > screenshots and share them with you if that would help. > > Cheers, > > drew > > > > On Fri, Jun 21, 2019 at 1:08 PM Casey Barker <[email protected]> wrote: > >> We've had a successful flight to ~76k' with a combination of TeleMega and >> EasyMega for primary and backup, respectively. I know of at least one >> successful flight to well over 100k' that also used *Mega boards in some >> capacity. The Kalman filter model seems to work quite well. >> >> If you're doing 2-stage, there are definitely some programming tips that >> I think could really help, particularly around the ignition event >> configuration and lock-outs. (Sadly, we've had a few flights where the >> lock-out programming became all too relevant.) I can dig up my notes if >> that would be of use. >> >> Other than that, I think it's fair to summarize the prevailing wisdom as: >> - Make sure you're using the latest firmware, or at least understand the >> errata for whatever version you choose to run. >> - Make sure the accelerometer is reasonably calibrated. >> - But as long as you're over 100k', it turns out that perfectly detecting >> and ejecting at apogee probably isn't all that critical. You just need to >> get the airframe in a good configuration before the atmosphere becomes >> relevant. >> >> Casey >> >> On Thu, Jun 20, 2019 at 7:06 PM Craig Klimczak <[email protected]> wrote: >> >>> Our Maryland MDRA Team is building a high altitude project to fly at >>> BALLS this year. The Avionics suite includes a TeleMega flight computer. >>> The rocket is single stage dual deploy with a research motor. I'm reaching >>> out to this forum for any advice on programming and using the TeleMega for >>> rocket flights above the 100,000 foot mark. >>> >>> Are there any special considerations for setting up the TeleMega for >>> flights to over 100,000 feet? >>> >>> Are there any considerations for rockets exceeding Mach 3? >>> >>> What are the highest altitudes achieved with the TeleMega to date? I've >>> flown this TeleMega to 35,000 feet with no problems. Is there an altitude >>> where the performance of the TeleMega may be limited? Has anyone on this >>> forum flown a TeleMege to 100,000 feet before. If so, how did it perform? >>> Did you have any issues with tracking? Losing GPS lock? Apogee detection? >>> >>> Thanks, >>> Craig Klimczak >>> TRA #13451 >>> _______________________________________________ >>> altusmetrum mailing list >>> [email protected] >>> http://lists.gag.com/mailman/listinfo/altusmetrum >>> >> _______________________________________________ >> altusmetrum mailing list >> [email protected] >> http://lists.gag.com/mailman/listinfo/altusmetrum >> > _______________________________________________ > altusmetrum mailing list > [email protected] > http://lists.gag.com/mailman/listinfo/altusmetrum >
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