Staging Electronics

[jmuck78]

I have a two stage project that I've been sort of working on for a while - Madcow Nike Apache. I picked up a Missile Works PET2 timer a year or two ago. I was looking for a second PET2 timer because of the tilt functionality, but it looks like it has been discontinued. Is there another altimeter on the market that can monitor the rocket's tilt before airstarting the upper stage motor? How do others implement the tilt checking functionality for airstarts?

 

[tsmith1315]

Is there another altimeter on the market that can monitor the rocket's tilt before airstarting the upper stage motor? How do others implement the tilt checking functionality for airstarts?

The Eggtimer Proton detects by deviation between barometric altitude and integrated acceleration data. If path length is significantly longer than altitude, then the path is not vertical.

 

[jmuck78]

The Eggtimer Proton detects by deviation between barometric altitude and integrated acceleration data. If path length is significantly longer than altitude, then the path is not vertical.

is that sufficient to meet the tilt detection requirement for airstarts?

 

[JimJarvis50]

I have a two stage project that I've been sort of working on for a while - Madcow Nike Apache. I picked up a Missile Works PET2 timer a year or two ago. I was looking for a second PET2 timer because of the tilt functionality, but it looks like it has been discontinued. Is there another altimeter on the market that can monitor the rocket's tilt before airstarting the upper stage motor? How do others implement the tilt checking functionality for airstarts?

The Missileworks timer does NOT have tilt functionality. That is a common misconception due to the way the features are described.

The Eggtimer does a better at detecting larger tilt angles, but they also allow an altitude check, which should always be used on staged flights. If you really want a tilt measurement (and need to stay with low tilt for whatever reason), there are several vendors that provide products with actual tilt inhibition.

Jim

 

[jmuck78]

The Missileworks timer does NOT have tilt functionality. That is a common misconception due to the way the features are described.

The Eggtimer does a better at detecting larger tilt angles, but they also allow an altitude check, which should always be used on staged flights. If you really want a tilt measurement (and need to stay with low tilt for whatever reason), there are several vendors that provide products with actual tilt inhibition.

Jim

OK, I certainly misperceived the PET2 manual then. The timer description includes a "Inertial Trigger Axis - X-axis / Y-axis / Z-axis / Auto Detect", sounds like I misread that?

 

[WillMarchant]

You might want to look at https://altusmetrum.org/EasyTimer/

 

[jderimig]

You cannot detect subtle tilt (0-30 degrees) by comparing inertial and barometric altitude, the uncertainty of the baro altitude, especially at speed will not allow that. It can detect disastrous off vertical flight however.

 

[cerving]

You cannot detect subtle tilt (0-30 degrees) by comparing inertial and barometric altitude, the uncertainty of the baro altitude, especially at speed will not allow that. It can detect disastrous off vertical flight however.

An that is the purpose... to prevent seriously off-axis ignitions. And yes, sometimes it's too conservative and prevents a sustainer ignition that should have been acceptable, but I'd rather have that than the opposite.

 

[OverTheTop]

I have used the TeleMega for staging, using two channels for the tilt detection. One channel provided ignition if the stage was vertical and the timer had reached the allotted time, as per nominal flight. This channel had a tilt lockout set to 20deg for safe flight within the cylinder. The second channel was set to trigger the burn if the tilt got to 12degrees. That way if the rocket wasn't travelling vertical it would light the sustainer early, for a slightly off-nominal flight, rather than just let the flight continue till the sustainer couldn't be safely lit.

This was accomplished easily by just paralleling the two pyro channels on the altimeter.

 

[JimJarvis50]

OK, I certainly misperceived the PET2 manual then. The timer description includes a "Inertial Trigger Axis - X-axis / Y-axis / Z-axis / Auto Detect", sounds like I misread that?

I believe it is intended to prevent the timer from operating before launch if the rocket is not pointing up. It doesn't have gyros and can't detect angle during flight. The manual is quite confusing on this feature.

Jim

 

[jmuck78]

I believe it is intended to prevent the timer from operating before launch if the rocket is not pointing up. It doesn't have gyros and can't detect angle during flight. The manual is quite confusing on this feature.

Jim

Thanks - glad I asked.

 

[Howitzer]

You need a MARSA33 with the gyro module. Worked like a charm in my terrier sandhawk! Thankfully I had John around to help me verify it was all set up properly.

 

[Cameron Anderson]

You need a MARSA33 with the gyro module. Worked like a charm in my terrier sandhawk! Thankfully I had John around to help me verify it was all set up properly.

John must have his Marsas wired for tracking because when I was setting mine up with the tilt gadget he just happened to be around to assist too.

Also, very user-friendly device for staging - I recommend it.