Supersonic worries?

I'm getting ready to launch my Loc Norad Pro Maxx on a J340m for my level 2 certification. I have converted it to dual deploy, and lengthened the front body tube to accommodate the main chute. Rocksim is predicting that the rocket will go just above Mach 1. I'm worried that it will cause problems with my Easy Mini Altimeter and cause it to deploy early. Does anyone have experience with this?

Since it is baro only, I too would be concerned. Does the program contain a mach inhibits? Basically it is a sort of delay before arming the charges.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

SinfulDarkLord said:

Since it is baro only, I too would be concerned. Does the program contain a mach inhibits? Basically it is a sort of delay before arming the charges.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

Click to expand...

The EasyMini doesn't get affected by weird transient shocks from flying supersonic. I haven't actually flown mine supersonic, but it is equipped with a Kalman filter and should be immune to such problems.

How good do you feel about the structural integrity and build quality of your rocket? My one [slightly unintended] attempt ended ~1.5 seconds after launch with a bunch of shredded rocket bits raining down over the field and a parachute that's probably still aloft (2 years later...). Taught me a thing or two about materials and construction processes for Mach flight and to pay close attention to max Mach number in the sims when trading out motors.

If built well, that kit will easily go Mach with no issues. It is designed to take the full span of the CTI 38mm's. My Nuke Promaxx flew quite well on a J335 somewhere around 1.3ish. With the transition and the 3" fin can, the Norad should be a bit slower. Cool looking kit, best of luck!

Thanks everyone for the input. I'm not worried about the rocket handling it, it's a pretty durable rocket. The Norad is designed to take J motors. I did extend out the front section, but it is riveted on. While studying for my level 2, I got to worrying about my EasyMini deploying my apogee charge when the rocket goes supersonic. I'll post the flight results. Here's the Rocksim view. If you compare it to the picture in my signature, you'll see that she's a little bit longer with an AVBay.

CarVac said:

The EasyMini doesn't get affected by weird transient shocks from flying supersonic. I haven't actually flown mine supersonic, but it is equipped with a Kalman filter and should be immune to such problems.

Click to expand...

CarVac, I really appreciate your comment! I did look, and all of the Altus Metrum altimeters are built with a Kalman filter meaning they will not be fooled by going supersonic. That was my only worry. I'm sure this bird is going to fly nicely.

Link to where it says it has the filter please.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

SinfulDarkLord said:

Link to where it says it has the filter please.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

Click to expand...

All Altus Metrum products have them, though the only mention that I found in a cursory exploration of their site is here: https://altusmetrum.org/AltOS/ in the changelog for 1.2.1.

It's in the online user manual. I'll shoot a link when I get back to my laptop.

Here's a link to the online User Manual:

https://altusmetrum.org/AltOS/doc/altusmetrum.html#idp49362384

Here's an excerpt:

6.3. Apogee Lockoug

Apogee lockout is the number of seconds after boost where the flight computer will not fire the apogee charge, even if the rocket appears to be at apogee. This is often called 'Mach Delay', as it is intended to prevent a flight computer from unintentionally firing apogee charges due to the pressure spike that occurrs across a mach transition. Altus Metrum flight computers include a Kalman filter which is not fooled by this sharp pressure increase, and so this setting should be left at the default value of zero to disable it.

Works for me, I do plan to use the easymini on my speedy gonzales rocket.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

I think you'd be hard-pressed to find a baro altimeter which requires a Mach delay anymore. Sally forth!


Later!

--Coop

Coop said:

I think you'd be hard-pressed to find a baro altimeter which requires a Mach delay anymore. Sally forth!

Click to expand...

Yep; this was an early work-around from the days of low processing power and technical sophistication.

I flew the baro-only RRC-3 just over Mach 1 (measured) in a Loc EZI-65 last weekend without incident. So, for normal rocket shapes I am comfortable using barometric measurement. Of course, this requires proper pressure ports (I suggest 3 spaced around the circumference).