RC Ejection Electronics?

[PunkRocketScience]

After the ill-fated flight of my team's Y-wing at Plaster Blaster this year, I no longer trust my Missleworks WRC2. I don't like to fly really big rockets without some manual "chicken switch" to backup the automatic altimeters...

I'm not exactly sure what happened with the WRC2, but it definitely fired while the rocket was still under boost, tearing the Y-wing apart. Not sure if the on board portion failed, the hand held controller failed or it was some kind of outside interference.

Does anyone know of any other radio controlled deployment devices? Preferably an encoded transmitter/receiver set that are tuned to each other, thus preventing accidental deployment by outside interferance...

 

[Juerg]

Are you sure it actually was the WRC2 that fired?
While I don't have personal experience with it, I have been looking into it. From an engineering point of view (but without insight in the program) it is looking pretty good.

Is ist excluded that a timer/altimeter fired?

Nice project anyway!

Juerg

 

[PunkRocketScience]

Hard to tell... Both e-matches were in the same black powder charge, and thus both burned. It is possible that the altimeter fired, but I'd put it down as unlikely.

 

[cjl]

If there is any question, you could always call up Jim Amos and ask him some questions about the specific application and any potential for accidental firing. I have seen the WRC2 used many many times without a single problem, and I would be quite surprised if it had fired accidentally. I would put altimeter failure as significantly more likely than the WRC failure. What was(were) the altimeter(s) used?

 

[uncle_vanya]

While I'm also in the camp that thinks the altimeter is more likely to blame - here is an alternative device that you might consider. I'm hesitant because I do not see any encryption or other security but here it is:

https://www.aeroconsystems.com/electronics/radiofire.htm

 

[Juerg]

I'm hesitant because I do not see any encryption or other security but here it is:

https://www.aeroconsystems.com/electronics/radiofire.htm

The security on this device seems to be rather simplistic: It calls for "full signal" on one channel for about 1/4 of a second. So basically just a "timeout".
A digital key code would be much safer.
If you are using the Aerocon device together with a PCM R/C device: Good!
But don't try a cheap AM/FM style R/C, as radio interference from the motor exhaust may disturb it (seen that happening!)
If one has the $, the WRC2 seems to be much more failsafe and have a better range.
The Aerocon system is way cheaper and allowable also outside of the US (where the WRC2's frequency band may not be allowable)

Juerg

 

[sylvie369]

I used the Missileworks WRC roughly 6 times. I had trouble with the first unit that I got - it would only work if I put the transmitter right up next to the receiver. When I explained the problem to him, Jim A. promptly sent me a replacement, which worked reliably and with no accidental firings (which of course could be dangerous). In the process of testing the first one (to make sure I wasn't doing something wrong) and then the second one (needless to say, I'd become concerned about reliability), I played around with them quite a bit, and I'm confident that it works properly and reliably. I never had an accidental firing of any sort, even in the first unit.

If you haven't replicated the unplanned firing problem on the ground in a situation in which the WRC was the only possible culprit, I would be hesitant to conclude that it was at fault. It seems far more likely that the altimeter fired.

 

[paparoof]

I've never flown electronics and this won't help you after the fact, but don't these units have some sort of logging/debugging you can enable before the flight that would include an entry that the unit sent a signal to fire the charge?

Being in the Internet-troubleshooting business, reading logs is very commonly the only way for me to get questions answered.

 

[ben]

I don't want this to turn into a giant locked thread sue to this but I would like to raise this question to the Y wing build team.

Could the placement of the altimeter, and the flight pattern, plus the shape of it, cause the air to not flow "straight" and cause the altimeter to prematurily fire. It is very possible that happened. What altimeter where you using? I would like to see if there was any wacky data.

Ben

 

[sylvie369]

I've never flown electronics and this won't help you after the fact, but don't these units have some sort of logging/debugging you can enable before the flight that would include an entry that the unit sent a signal to fire the charge?

Being in the Internet-troubleshooting business, reading logs is very commonly the only way for me to get questions answered.

In fact there is no logging of any sort on the WRC. Furthermore, the logging altimeters that I've flown merely record the sensor data (barometric readings/accelerometer readings), not the altimeter's output attempts.

 

[cjl]

The R-DAS tiny puts markers in the data for the time it detected liftoff, detected apogee, and fired each output (up to 4).

 

[Juerg]

Could the placement of the altimeter, and the flight pattern, plus the shape of it, cause the air to not flow "straight" and cause the altimeter to prematurily fire.

That's exactly what I am thinking! If it was a "barometric-only" altimeter, then this is the explanation. The y-wing simply doesn't have one place on its airframe where the "at least 4 calibers of clean body tube without diameter change in front of the static ports" is true.

Juerg

 

[falingtrea]

In fact there is no logging of any sort on the WRC. Furthermore, the logging altimeters that I've flown merely record the sensor data (barometric readings/accelerometer readings), not the altimeter's output attempts.

If you have any flight data at all, you can at least see if a pressure or accelerometer incident occured that could have fired the charge prematurely. Never discount any data collected until you have analyzed it. I like the idea of markers put in the data for specific actions, like the R-DAS does. Makes the data easier to analyze. It is not a major software change so I am surprised that more logging altimeters don't do it.

 

[ben]

That's exactly what I am thinking! If it was a "barometric-only" altimeter, then this is the explanation. The y-wing simply doesn't have one place on its airframe where the "at least 4 calibers of clean body tube without diameter change in front of the static ports" is true.

Juerg

I think you can get away with less than 4 on a NORMAL rocket. But when this thing has so many lines its deffinitally a possbility.

Ben

 

[Loki]

Furthermore, the logging altimeters that I've flown merely record the sensor data (barometric readings/accelerometer readings), not the altimeter's output attempts.

Are you sure about that? I don't know which logging units you are referring to, but the ARTS logs output attempts, as well as the "state" (launch detected, burnout detected, apogee detected, etc...).

I know the old BlackSky AltAcc logs the output attempts.

I'm not sure about the G-Wiz and RDAS, but I'd be very surprised if they did not log the output events.

For obvious reasons, this is important information to have and as it is very easy to record this info, I'm surprised if there are units that don't record it.

 

[Komvee]

All the new R/C 2.4Ghz stuff is digitally bound between transmitter and receiver.

I am sure you could use one of these radios (Spektrum etc.) with it's supplied receiver, a servo and a switch to rig an ejection system pretty easily.

Or just link in the AeroCon product mentioned above. I'd stay away from the standard 50, 53 and 72Mhz bands altogether.

I used a similar setup in the early 80's using the servo to release the pins on a spring-loaded nosecone; it worked very well.

I'm a BAR still furiously searching through the internet for all the new technological information, so bear with me if I am repeating well-known standards here.

 

[sylvie369]

Are you sure about that? I don't know which logging units you are referring to, but the ARTS logs output attempts, as well as the "state" (launch detected, burnout detected, apogee detected, etc...).

I know the old BlackSky AltAcc logs the output attempts.

I'm not sure about the G-Wiz and RDAS, but I'd be very surprised if they did not log the output events.

For obvious reasons, this is important information to have and as it is very easy to record this info, I'm surprised if there are units that don't record it.

The only logging altimeters I've flown have been the Perfectflites, and they do not log output events. I'm not that surprised that the higher end ones do, and I agree that it would be a nice feature. Obviously in this situation (the Y-Wing) they'd answer the important question. That'd go a long way towards justifying the additional cost.

The WRC does not log anything.

 

[snowman2]

Not sure if the on board portion failed, the hand held controller failed or it was some kind of outside interference.

The WRC2 is a frequency hopping, digital system. Interference is not an issue.

Was your WRC2 on the flight? If not, then yours is probably okay.

Team Outlander used two WRC2s with the Outlander flown at Midwest Power 3. They provided a means to remotely destabilize the rocket by blowing out the main chute. If the flight went bad and toward people then the rocket would have been brought down.

The best system is a frequency hopping one. A single frequency system can be used if there are no other transmitters that will interfere with your transmitter. 433.92 MHz is an overcrowded space. There are even some rocketry telemetry systems on that frequency.

I hope Jim Amos produces a new RC system. Meanwhile, search for wireless industrial remote control systems.

 

[denverdoc]

There is a new and improved Missile Works WRC in the works. I'm also tempted to do one of those DSS radios, but last I checked they don't have the range of the WRC (2 miles+)