What happened?

Hi, all. If you saw my earlier thread in HPR, you'll know that I went for and achieved my NAR Level 2 on Saturday. But I am left with a big question.

Here's what happened.

Rocket: Giant Leap Vertical Assault

Maiden Flight and 1st DD
Motor: CTI I285CL
Altimeter: MW RRC2+

Launched beautifully. Drogue deployed at apogee, 2465 feet. Mains deployed at 300 feet. Rocket recovered in perfect condition. Success!


Second Flight and Level 2 Attempt
Motor: CTI J240RL
Altimeter: MW RRC2+

Launched beautifully. Drogue deployed at apogee, 4847. No mains deployed. Slight nose cone dent and lots of caked on mud from impact. Inspection revealed that the charge was never ignited.


Question: Why didn't my mains deploy the second time?

Possible culprits:

• Weak battery - NO; tested 9.24v after flight.
• Loose battery - NO; altimeter was on and beeping altitude after flight.
• Blocked pressure-sensor hole - NO; couldn't be, or else drogue would also have not deployed, right?
• No continuity to e-match - NO; tested continuity of e-match and circuit from altimeter to e-match; all good.
• Bad altimeter - NO; first flight deployed drogue and main successfully. No damage was sustained to the altimeter during on between flights.

So, what happened? It seems like the RRC2+ just never detected 300' and never attempted to ignite the charge.

I am concerned, because now that I am Level 2, I want to fly bigger motors at URRF in a few days, but I don't want a descent with no mains from a mile or two up.

Any ideas? Thanks.

If you connect the ematch directly to a battery (ematch only) does it light or is it shorted? What kind of switch do you use to arm the altimeter?

I did not connect the e-match to the battery, but I did continuity test it post-flight and it showed 0 Ohms.

I have a rotary switch like this: https://doghouse.blastzone.org/switches.html

It was on and the altimeter was beeping out the altitude post-flight.

Zero ohms means it is shorted, you should be getting two or three ohms for most ematches. See if it fires when hooked to a battery. Just because it is on at the end of the flight does not mean it cannot loose power at some point during the flight (after the shock of the apogee charge going off for example).

If you don't figure it out I will also be at URRF an I have 2 eggtimer altimeters and an RRC2 that you could use if need be.


Sent from my iPod touch using Rocketry Forum

Bat-mite said:

Hi, all. If you saw my earlier thread in HPR, you'll know that I went for and achieved my NAR Level 2 on Saturday. But I am left with a big question.

Here's what happened.

Rocket: Giant Leap Vertical Assault

Maiden Flight and 1st DD
Motor: CTI I285CL
Altimeter: MW RRC2+

Launched beautifully. Drogue deployed at apogee, 2465 feet. Mains deployed at 300 feet. Rocket recovered in perfect condition. Success!


Second Flight and Level 2 Attempt
Motor: CTI J240RL
Altimeter: MW RRC2+

Launched beautifully. Drogue deployed at apogee, 4847. No mains deployed. Slight nose cone dent and lots of caked on mud from impact. Inspection revealed that the charge was never ignited.


Question: Why didn't my mains deploy the second time?

Possible culprits:

• Weak battery - NO; tested 9.24v after flight.
• Loose battery - NO; altimeter was on and beeping altitude after flight.
• Blocked pressure-sensor hole - NO; couldn't be, or else drogue would also have not deployed, right?
• No continuity to e-match - NO; tested continuity of e-match and circuit from altimeter to e-match; all good.
• Bad altimeter - NO; first flight deployed drogue and main successfully. No damage was sustained to the altimeter during on between flights.

So, what happened? It seems like the RRC2+ just never detected 300' and never attempted to ignite the charge.

I am concerned, because now that I am Level 2, I want to fly bigger motors at URRF in a few days, but I don't want a descent with no mains from a mile or two up.

Any ideas? Thanks.

Click to expand...

Did you try to fire the e-match in question, make sure it fires correctly through the exact wiring set up? (After removing charge)

Any crossed (shorted) wires in the lines from alt to charge (including e-match leads)? This could indicate cont. but prevent ignition.

Have you re-tested (After flight) the altimeter in a vac chamber, or in alt bay with a shop vac, making sure both e-matches fire as planned?

What was your max velocity? Did it break mach? I'm not sure how the RRC2 handles Mach lock out or delay.

Just throwing a few things out there to check. Sounds very frusterating to have a perfect recovery sequence, then the very next one have a failure.
Congrats on the L2 though.
4847 ft - Could you visually see that flight and decent, or did you have a tracker to find it?

JW

Another question - How many vent holes do you have in your alt bay?

Bat-mite said:

I did not connect the e-match to the battery, but I did continuity test it post-flight and it showed 0 Ohms.

Click to expand...

I agree with Terry - it sounds like a short.

-Kevin

Bat-mite said:

I did not connect the e-match to the battery, but I did continuity test it post-flight and it showed 0 Ohms.

Click to expand...

Terry is right, "0Ω" is a short, not indicative of a good match. Post-flight I would expect a burned match to have ∞Ω (open) so my guess is that it was bad pre-flight as well.

Always test your e-matches before flight, once when prepping the charge and once right before connecting them to the flight computer. That vaunted high reliability is only for ones that test within the proper resistance range.

Will try the e-match ignition test tonight and get back to you all. Thanks for the advice.

For Txnrcr, I have two holes. Good enough for the first flight. I don't know if I broke mach; I do not have an accelerometer. But the RRC2+ has built-in mach immunity, and is good up to 40,000 feet MSL.

Yeah, zero ohms is the clue here. Sounds like a shorted igniter. If hooked directly to a battery I expect it will not fire.

I agree with always checking your igniters for resistance pre-flight, with one exception: You really don't wanna be running any electricity thru an igniter that's already installed in a BP charge. Not even for a continuity check. Test them before, when they are out in the open.

Most good igniters will read at least one ohm. The ones Crazy Jim sells are 1 to 1.2 ohms, a Q2G2 is about 3 ohms, and so on. Good luck.

Similar issue with me, different hardware and the altimeter did sense and record a firing but it never fired and the battery and e match were proven to be good, at least 2 min later when I tested them. Here is a link to my thread, even though it's different hardware and symptoms the ohm meter (accurately measuring resistance) and lipo discussion, mainly from Bob, may be helpful.

https://www.rocketryforum.com/showt...to-terminal-blocks-but-do-direct-on-altimeter

mpitfield said:

Similar issue with me, different hardware and the altimeter did sense and record a firing but it never fired and the battery and e match were proven to be good, at least 2 min later when I tested them. Here is a link to my thread, even though it's different hardware and symptoms the ohm meter (accurately measuring resistance) and lipo discussion, mainly from Bob, may be helpful.

https://www.rocketryforum.com/showt...to-terminal-blocks-but-do-direct-on-altimeter

Click to expand...

Thanks.

I retested the resistance of the ematch, and it was not zero. It starts at zero, but then takes a second or so to climb up to 1.2.

So I touched it to the battery, and for sure the ematch lit.

Having read the above thread, the only thing I am left with is that maybe I did not completely strip the wires on the ematch to the terminal block. Considering I had a successful ignition on the first flight, I have to think, what could have been different the second time around?

I guess it's possible that somehow the pressure-sensor holes in the airframe got blocked. Maybe when the drogue charge blew, the AV bay swiveled a little and blocked the holes. But I don't see that as likely.

So I'm thinking I must have left some insulation on the wires at the terminal bock.

I guess I will test fly it at URRF with a smaller motor to see what happens. I don't have time between now and then to buy LEDs and rig up a vacuum test.

So you got the level 2 even though the mains did not deploy? Is that because it successfully deployed some form of recovery at apogee and the rocket was in good enough shape (despite the faster than planned landing) to fly again?

I'm not criticizing - I congratulate you on building a rocket which had a great first flight, and on the second flight a good apogee deployment and survived the mains not deploying - I'm just curious on how the ruling works for the cert.

John,,
I don't think 1.2 ohms is correct for an ematch...
it's too little ohms..
You have more of those matches ???
Put an ohm meter on a half dozen of them...

I believe that match was bad...

Congrats on the level 2 John...

Teddy

probably bad match BUT.....

could be that one of your attachment points from the altimeter to the match failed / wasn't made right. On almost everything I have I wire the match to the altimeter directly (no posts of any type on the bulkheads) because they are failure points. it any of them were loose or failed, well the match will too. Even when you put the match directly to the altimeter, are you making sure the bare wire is crushed by the altimeter connector, and you've given it a tug to make sure it's secure? loose or fault connections, or a connector on the insulator will do the same thing.

see you in a couple of days at urrf. I'll be at the red trailer....

rick

Zebedee said:

So you got the level 2 even though the mains did not deploy? Is that because it successfully deployed some form of recovery at apogee and the rocket was in good enough shape (despite the faster than planned landing) to fly again?

I'm not criticizing - I congratulate you on building a rocket which had a great first flight, and on the second flight a good apogee deployment and survived the mains not deploying - I'm just curious on how the ruling works for the cert.

Click to expand...

According to NAR:

1. The individual will fly his model. The flight must be witnessed by the certification team members. Stability, deployment of the recovery system, and safe recovery should be considered when evaluating safety of the flight. Models experiencing a catastrophic failure of the airframe, rocket motor, and/or recovery system (e.g., shock cord separation) will not be considered as having a safe flight.
2. The model must be returned to the certification team after flight. and be inspected to verify engine retention and for evidence of flight-induced damage. The certification team will initial the blocks indicating that a safe flight was made and that the post-flight inspection was satisfactory. In general, the guideline for acceptable flight damage is that the model could be flown again without repair. It is left to the judgement of the certification team to differentiate between flight damage and "normal" maintenance to assure reliability (e.g., shock cord replacement to prevent future flight problems). "Zippering" of the body tube is another area of flight damage left to certification team judgement for acceptability.

Was the exposed copper wire broken off after the flight? This can happen if you use diagonal cutters to strip solid wire.

Did you give each lead a slight tug after screwing down the terminal block screw? Sometimes the wire is above or beside the plate and you don't have a reliable connection.

No and yes respectively. I think it is possible that insulation was in the way, between the wire and the contact.

Bat-mite said:

No and yes respectively. I think it is possible that insulation was in the way, between the wire and the contact.

Click to expand...

If that was the case, your altimeter would not have given you a positive continuity check as you said it did above.

chadrog said:

If that was the case, your altimeter would not have given you a positive continuity check as you said it did above.

Click to expand...

Ah, crap, you're right. There's always the chance I am confusing my first and second launches. Unless the altimeter suddenly broke between flights, then it has to be some sort of continuity/sufficient current/bad e-match kind of problem.

Has anyone ever heard of an RRC2+ spontaneous breaking after a successful flight?

Bat-mite said:

Ah, crap, you're right. There's always the chance I am confusing my first and second launches. Unless the altimeter suddenly broke between flights, then it has to be some sort of continuity/sufficient current/bad e-match kind of problem.

Has anyone ever heard of an RRC2+ spontaneous breaking after a successful flight?

Click to expand...

I've only flown mine once so far, hopefully not!

I would go with the most likely failure scenarios. The most likely is ematch failure. The second most likely in my opinion is failure of the power switch. I realize these are popular switches and are used a lot for dual deploy flights. This does not mean they cannot fail. I had one go flakey on me and it would cut in and out. These are voltage selector switches and while they can work well for rocketry use it is not what they were designed for.

Since I'm just beginning to venture into DD I have one question.

This incident I assume is the reason some folks I've seen here use a backup altimeter,, is that right?

Thanks and congrats on your L2

Ed

What type of e-match was it?

race 58 said:

Since I'm just beginning to venture into DD I have one question.

This incident I assume is the reason some folks I've seen here use a backup altimeter,, is that right?

Thanks and congrats on your L2

Ed

Click to expand...

Yes, and thanks. That may well be in my future. :wink:

dixontj93060 said:

What type of e-match was it?

Click to expand...

One of the Crazy Jim's.

Well, to bring this thread to a close, I made a foolish and costly mistake. I decided that I must have either had a bad e-match or poor contact, and I decided to go ahead and use it again at URRF.

I put a K650 in my Giant Leap Vertical Assault and went for 10,000'. I checked my RRC2+ carefully while assembling and loading. All beeps as expected. Battery at 9.2V. Continuity to main and drogue.

When I got it vertical on the pad, checked it again. All beeps as expected. No error codes.

Launched. It canted a bit but mostly went straight up. About 3000 feet up, both my charges blew while in full acceleration. Shredded the rocket. Blew the AV bay to pieces. Altimeter never found. Rocket could be cut and reworked into a shorter version, I guess. Very, very disappointing.

So here's my question? Could my Av bay holes have been the problem?

My configuration was this:

O (3/16" hole)

O (switch, not a hole)

o (1/8" hole)

To accommodate the depth of the switch, the sled was facing the opposite side from the holes:



Would that matter? Was this a bad altimeter, or did I screw it up via hole placement or size, or altimeter orientation?

I believe the RRC2+ can be mounted/oriented in any direction, as for the vent holes, I've always seen no less than 3 evenly spaced around the body tube/switch band and usually 3/16" each.

From the Users Manual:

The RRC2+ can be mounted in any direction on the sled.

The RRC2+ should be mounted above the sled a minimum of 1/8" on standoffs or insulated washers. The barometric sensor
mounted on the bottom of the altimeter has tiny holes in it to sample air. They must NOT be blocked by mounting too tight on
the sled. If you can slip a credit card between the bottom of the RRC2+ and sled, you’re good to go!

Vent holes in avionics bay allow the altimeter to sample air pressure. Here are typical some 3-hole example sizes:
A. 38 mm by 6 in. 3 x 1/16” holes
B. 54 mm by 7 in. 3 x 1/8" holes
C. 3 in. by 9 in. 3 x 5/32” holes
D. 4 in. by 12 in. 3 x 3/16” holes
E. 6 in. by 18 in. 3 x 1/4"holes