Failure Analysis of Hyperion

UhClem said:

2 ea 3/16" pressure relief holes is likely not enough. With a 7.5" diameter by 46" main parachute compartment the time constant is about 9 seconds. The altitude wasn't too high so the pressure delta was only about 3psi. With no venting the pressure pushing on the nose would be about 130 pounds. while#4-40 nylon screws shear at about 40 pounds or 120 pounds for 3. The vents helped but there was still a significant preloading on the shear pins at apogee.

I didn't run any pressure data through my filter.

Click to expand...

Where did you find the calculations for this? I've never heard the hard and fast rule.

UhClem said:

2 ea 3/16" pressure relief holes is likely not enough. With a 7.5" diameter by 46" main parachute compartment the time constant is about 9 seconds. The altitude wasn't too high so the pressure delta was only about 3psi. With no venting the pressure pushing on the nose would be about 130 pounds. while#4-40 nylon screws shear at about 40 pounds or 120 pounds for 3. The vents helped but there was still a significant preloading on the shear pins at apogee.

I didn't run any pressure data through my filter.

Click to expand...

Wouldn't the maximum preload on the nosecone happen well prior to apogee? dP/dt (outside the bay) is very small at apogee so the compartment pressure will have started to decrease well before apogee. How much preload would remain depends on how much time the rocket "loiters" around apogee pressures. It would be a cool model that but I have too many other things on my plate.

blackbrandt said:

Where did you find the calculations for this? I've never heard the hard and fast rule.

Click to expand...

I've used this reference chart for vent holes.

https://www.vernk.com/AltimeterPortSizing.htm

jderimig said:

Wouldn't the maximum preload on the nosecone happen well prior to apogee?

Click to expand...

That link I included covers this. Perhaps the highlighting was too subtle: https://home.earthlink.net/~david.schultz/rnd/pressurelag/parachute.html

First of all, pressure relief doesn't really come into effect at 7k. 70k, maybe. His holes were fine.

llickteig1 said:

I can't help you find your rocket, but I hope you can get some help and walk it out until it is found. BTW, it is always windy in Kansas so practically everything is recovered multiple miles down-range. One adage we recognize is "It's always farther than you think." I would keep this in mind as others have suggested during your search.

For future reference ...

Pay attention to Jim Hendrickson. RDF trackers as backup to GPS are a necessity. I spent the weekend at Argonia watching several flyers fiddle with flaky GPS units of various makes. I am certain I would not trust my L3 attempt to GPS alone. All our regular, experienced GPS flyers use RDF trackers, especially on high-altitude flights.

One thing I haven't seen discussed and which may be obvious to some but not to others: Did the rocket have small pressure equalization holes in each airframe section? Forgetting to provide those can cause the main compartment to be pressurized to the ground-level atmosphere which is trying to push things apart at altitude. This is a condition that can't be replicated during ground tests and cause pre-mature separation, especially when the forces of the drogue deployment occur.

Again, good luck.

--Lance.

Click to expand...

One place on earth RDF will let you down. Out west on the playa or salt flats. One does fine in the air but once on the ground the salts and low water table suck up Rf like a sponge and the ground footprint is zilch. GPS does great in the air and with a good receive station and a Yagi for Ham bands or a patch for 900Mhz can get that last important
final packet before touchdown to give one a fair chance of getting very close to recovery. I'd venture a guess that the higher power 900Mhz trackers of 250Mw or 1 watt would would stand a better chance.

I've heard folks post that GPS tracking is mandatory out there if one wants a carefree recovery of sight unseen stuff and RDF isn't as helpful.

Us "flatlanders" and "sodbusters" in the Midwest, Prairielands and the East don't have to
worry about this. Kurt

falingtrea said:

I have to agree with mikec. The eggfinder TX should not be operated under any circumstance from a 1S Li battery pack. Even with the best LDO on the market, it would still be questionable. Because the eggfinder has seperate LDOs for the locator TX and the flight computer, that would explain why you lost lock but still deployed. The drop across the LDO increases as you draw more current, so the TX side could shutdown even though the flight computer side was still running.

Click to expand...

Just about everything on the TRS runs at 3.3V, so with a 1S LiPo at its rated voltage (3.7V) you only have .4V of LDO headroom. Considering that the regulator has to be able to reliably put out at least 400 mA to handle current surges from the GPS & RF module, you're not gonna find one that can handle it. Most of the very low LDO regulators are rated at under 100 mA maximum. The one that we use can source nearly 1A continuously, but the LDO voltage is about 1.1V. That's why we specify a 2S LiPo... you'll run the battery dead before you run out of LDO headroom. That might be bad for the battery, but you're going to get the absolute maximum amount of use out of it to help you find your rocket and get it down on the ground. And yes, the RF side will probably shut off first... the processor doesn't use much current, and most ematches fire in the tens of milliseconds, so it doesn't take much battery capacity to fire one.

Matt, you did a fine job on your L3 attempt. Sure, a few things could have gone better; I'd venture to say that's fairly common with a lot of big rocketry attempts. None of us are perfect. Props to you for looking to dig into things post flight rather than retracting into a cave for hiding. All of this Monday morning quarterbacking is a bit frustrating because we're all speculating; not a single one of us has physically seen your rocket post flight, so none of us really know:eyeroll:. It's all a bunch of guessing; 5 pages of guessing from resident experts. Don't let them drag you down; you'll get it next time and you know you have friends that'll help get you there!

jimzcatz said:

First of all, pressure relief doesn't really come into effect at 7k. 70k, maybe. His holes were fine.

Click to expand...

Absolutely!

UhClem said:

2 ea 3/16" pressure relief holes is likely not enough. With a 7.5" diameter by 46" main parachute compartment the time constant is about 9 seconds. The altitude wasn't too high so the pressure delta was only about 3psi. With no venting the pressure pushing on the nose would be about 130 pounds. while#4-40 nylon screws shear at about 40 pounds or 120 pounds for 3. The vents helped but there was still a significant preloading on the shear pins at apogee.

I didn't run any pressure data through my filter.

Click to expand...

I know a lot of people that have flown a lot of 7.5" rockets like Matt for a long time that have been doing it all wrong then; myself included. Flew two 7.5" rockets at the same LDRS that Matt was at in fact; two 5/32" holes is my norm. No dramas....ever.

mccordmw said:

I've used this reference chart for vent holes.

https://www.vernk.com/AltimeterPortSizing.htm

Click to expand...

Two different discussions. You're referring to the altimeter vent holes; the rest of the crowd is talking about relieving pressure in the airframe chute/cord sections.

.....


Sorry if I appear to be grumpy this morning. Matt has transformed decades of maturity in a few short years. Coming on here admitting *failure* takes balls and a big dose of swallowing ones pride. Yes, he's looking for answers, but none of us really know. Once this thing turns up, and I think it will in due time, then perhaps we might have some real answers, rather than a bunch of speculatory opinions.

blackbrandt said:

Where did you find the calculations for this? I've never heard the hard and fast rule.

Click to expand...

For my level 3, I had the same vent hole configuration you did. I ran the calculations through a program I built. You can see the results in my documentation on my thread. Basically, it works like this:

• Sim the rocket on you motor in Rocksim or OR and export the atmospheric pressure data over time to CSV.
• The program takes the number and size of the holes calculates the pressure differential change rate through the vent holes.
• It then takes the rate of atmo pressure change from the CSV export and calculates the payload bay pressure at each point using the different exchange.
• It takes the pressure differential and the internal area of the nosecone to calculate the force differential.
• It plots atmospheric pressure and force on nosecone from pressure differential for the flight on a graph.

I then size holes and shear pins accordingly. The force differential on my flight was 20lbs and your's is no more than 30lbs max and probably less than 10lbs at deployment. It's not a factor.

cerving said:

Just about everything on the TRS runs at 3.3V, so with a 1S LiPo at its rated voltage (3.7V) you only have .4V of LDO headroom. Considering that the regulator has to be able to reliably put out at least 400 mA to handle current surges from the GPS & RF module, you're not gonna find one that can handle it. Most of the very low LDO regulators are rated at under 100 mA maximum. The one that we use can source nearly 1A continuously, but the LDO voltage is about 1.1V. That's why we specify a 2S LiPo... you'll run the battery dead before you run out of LDO headroom. That might be bad for the battery, but you're going to get the absolute maximum amount of use out of it to help you find your rocket and get it down on the ground. And yes, the RF side will probably shut off first... the processor doesn't use much current, and most ematches fire in the tens of milliseconds, so it doesn't take much battery capacity to fire one.

Click to expand...

Translation: The manufacturer specifies 2s . Only use 2s. ( See manufactures documentation. )

warnerr said:

Translation: The manufacturer specifies 2s . Only use 2s. ( See manufactures documentation. )

Click to expand...

...which was an oversight on my part that won't happen again.

Eric, I don't think anyone made any comment out of spite or "holier than thou" viewpoint. I agree it takes gumption to air one's dirty laundry in a public forum. Without this discussion, the issues with shearpins (that generally apply to any flight)
would not have been aired. The poster who observed the idiosyncratic dual firing of apogee charges on more than one occasion with the chosen hardware would have remained out of mind. This doesn't "prove" anything about the
chosen altimeters as the rocket hasn't been found (yet) and even if found would be hard to determine if simultaneous apogee charges blew, if the main charges blew just after apogee or there was primary shearpin failure. The honest mistake of a 1S battery instead of 2S I'm sure will stick in everyone's mind if they are not well versed with batteries. It could have been surmised that both apogee charges fired or the shearpins were inadequate if the rocket would have been in position to see if debris or smoke came out of the open end of the main chute bay as it descended through the main and backup main deployment altitudes. I presume by that time, the rocket had drifted too far away for that to be observed.

The down and dirty lesson here for the casual observer is the 2S thing with EggFinders, paying attention to the shearpins although I would think if one did some reasonable ground testing that could empirically be arrived at. Of course one wouldn't be able to do anything about simultaneous apogee charge firings with resultant "shock" main deployment when the components reach the end of the apogee harness. Lastly, at least with a certification attempt, the rule about using different deployment electronics among the two devices is prudent. (I always thought this was balderdash with the more modern altimeters but when doing an L3, might be a reasonable idea for a candidate to consider.) I certainly am not suggesting it be made into a hard and fast "rule", that should be left up to the individual flier if they are going to do that or not.

One made the comment about "Go Fever". My reply to that would be unless anyone was able to see that the 1S battery was inadequate after the "postponed" flight, the tracker outcome would have been the same. Last I heard
about TRA rules (and correct me if I am mistaken) is unintended dumping of the main at apogee is not grounds to disqualify the attempt if the rocket is recovered intact within a reasonable time frame. I realize this is "flame bait"
as some feel very strongly against this. My impression is if the rocket is returned that day, it isn't necessarily a DNF. If it's lost to recovery, (not in a tree or inaccessible wires) for a length of time I can see the failure.
Kurt Savegnago

I love threads like these since they help people think about what could go wrong and what possibilities to consider when troubleshooting flight problems. Thanks to Matt for starting it.

Thats the rub on this . . If rocket was recovered he would be able to inspect electronics and see why the main deployed at apogee.. or maybe the bay was perfect and he put a big chute in both chambers .. it will be a mystery ..

What was the culprit on early main deployment on the other flights that happened previously ?

Kenny

ksaves2 said:

Eric, I don't think anyone made any comment out of spite or "holier than thou" viewpoint. I agree it takes gumption to air one's dirty laundry in a public forum. Without this discussion, the issues with shearpins (that generally apply to any flight)
would not have been aired. The poster who observed the idiosyncratic dual firing of apogee charges on more than one occasion with the chosen hardware would have remained out of mind. This doesn't "prove" anything about the
chosen altimeters as the rocket hasn't been found (yet) and even if found would be hard to determine if simultaneous apogee charges blew, if the main charges blew just after apogee or there was primary shearpin failure. The honest mistake of a 1S battery instead of 2S I'm sure will stick in everyone's mind if they are not well versed with batteries. It could have been surmised that both apogee charges fired or the shearpins were inadequate if the rocket would have been in position to see if debris or smoke came out of the open end of the main chute bay as it descended through the main and backup main deployment altitudes. I presume by that time, the rocket had drifted too far away for that to be observed.

The down and dirty lesson here for the casual observer is the 2S thing with EggFinders, paying attention to the shearpins although I would think if one did some reasonable ground testing that could empirically be arrived at. Of course one wouldn't be able to do anything about simultaneous apogee charge firings with resultant "shock" main deployment when the components reach the end of the apogee harness. Lastly, at least with a certification attempt, the rule about using different deployment electronics among the two devices is prudent. (I always thought this was balderdash with the more modern altimeters but when doing an L3, might be a reasonable idea for a candidate to consider.) I certainly am not suggesting it be made into a hard and fast "rule", that should be left up to the individual flier if they are going to do that or not.

One made the comment about "Go Fever". My reply to that would be unless anyone was able to see that the 1S battery was inadequate before the "postponed" flight, the tracker outcome would have been the same. Last I heard
about TRA rules (and correct me if I am mistaken) is unintended dumping of the main at apogee is not grounds to disqualify the attempt if the rocket is recovered intact within a reasonable time frame. I realize this is "flame bait"
as some feel very strongly against this. My impression is if the rocket is returned that day, it isn't necessarily a DNF. If it's lost to recovery, (not in a tree or inaccessible wires) for a length of time I can see the failure.
Kurt Savegnago

Click to expand...

Nicely put. The biggest threat of cert failure from dumping the main is recovering outside of waiver boundaries.

Matt, on the go fever, I instituted a section for hard and fast team checks. It's on my pre-launch packing checklist. The team gets together an talks about each flight. If anyone on the team has reservations any reservations about the launch, we scrub until they are satisfied it's been handled. Saved 2 airframes so far and it seems like it would have saved yours given Jim's reservations about the wind.

ksaves2 said:

Eric, I don't think anyone made any comment out of spite or "holier than thou" viewpoint. I agree it takes gumption to air one's dirty laundry in a public forum. Without this discussion, the issues with shearpins (that generally apply to any flight)
would not have been aired. The poster who observed the idiosyncratic dual firing of apogee charges on more than one occasion with the chosen hardware would have remained out of mind. This doesn't "prove" anything about the
chosen altimeters as the rocket hasn't been found (yet) and even if found would be hard to determine if simultaneous apogee charges blew, if the main charges blew just after apogee or there was primary shearpin failure. The honest mistake of a 1S battery instead of 2S I'm sure will stick in everyone's mind if they are not well versed with batteries. It could have been surmised that both apogee charges fired or the shearpins were inadequate if the rocket would have been in position to see if debris or smoke came out of the open end of the main chute bay as it descended through the main and backup main deployment altitudes. I presume by that time, the rocket had drifted too far away for that to be observed.

The down and dirty lesson here for the casual observer is the 2S thing with EggFinders, paying attention to the shearpins although I would think if one did some reasonable ground testing that could empirically be arrived at. Of course one wouldn't be able to do anything about simultaneous apogee charge firings with resultant "shock" main deployment when the components reach the end of the apogee harness. Lastly, at least with a certification attempt, the rule about using different deployment electronics among the two devices is prudent. (I always thought this was balderdash with the more modern altimeters but when doing an L3, might be a reasonable idea for a candidate to consider.) I certainly am not suggesting it be made into a hard and fast "rule", that should be left up to the individual flier if they are going to do that or not.

One made the comment about "Go Fever". My reply to that would be unless anyone was able to see that the 1S battery was inadequate before the "postponed" flight, the tracker outcome would have been the same. Last I heard
about TRA rules (and correct me if I am mistaken) is unintended dumping of the main at apogee is not grounds to disqualify the attempt if the rocket is recovered intact within a reasonable time frame. I realize this is "flame bait"
as some feel very strongly against this. My impression is if the rocket is returned that day, it isn't necessarily a DNF. If it's lost to recovery, (not in a tree or inaccessible wires) for a length of time I can see the failure.
Kurt Savegnago

Click to expand...

Valid point, Kurt. See, I knew I was posting grumpy this morning!:wink:

I am all for learning; that's what makes a place like TRF great! Learn from others' victories and losses. My main point is that we have 5 pages of replies of speculation without any concrete evidence of what actually went wrong (except for tracker related issue...good content there). Apologies as my opinion is driven by a career that is largely based on problem solving. IE: something *bad* happens, we reflect, determine root cause(s), assign corrective actions, and so on. It's really hard to generate meaningful corrective actions without understanding what actually went wrong. I parallel this thread to that concept.

Creating change without understanding the problem tends to make chaos. Not saying this is chaos, but there's a whole lot of armchair quarterbacking going on...and it frustrates me when people say you can or can't do x based upon computer stuff...some things you just gotta get out in the real world and live and learn through trial and error. Sims and formulas are great, but by actually doing is where true learning is derived.

Rant off. Don't let me be a downer; I'm looking forward to learning as well. Just don't go changing everything without understanding what needs changing!

NateLowrie said:

Nicely put. The biggest threat of cert failure from dumping the main is recovering outside of waiver boundaries.

Click to expand...

Nate, not sure if I understand this statement exactly. If your design calls for dual deploy where the main is deployed at low altitude (1000' agl for example) and the main is dumped at apogee, *I believe* the cert is void. One doesn't need traditional dual deploy for an L3 attempt (or the other levels for that matter), but *I've always been taught* the flight events have to function as intended in order to be a "successful" attempt.

Where are you getting that, Eric? I don't see main at apogee in the list of qualifications:

Certification Flight – Level 3 Certification flight may take place at any insured launch. The TAP member must be present and witness the certification flight. The TAP member must witness the rocket ascend in a stable manner and descend in stabilized manner controlled by the recovery system.

Post-Flight Inspection – The rocket must be presented to the certifying member for inspection. If the rocket cannot be recovered, but can be inspected in place (power lines, tree, etc...) this is acceptable. The certifying member shall inspect the rocket for excessive damage. Excessive damage shall be considered damage to the point that if the flyer were handed another motor, the rocket could not be put on the pad and flown again safely. Damage caused by wind dragging will not cause a disqualification.

Non-certification – Any of the following will result in non-certification for a certification flight:

• Motor Cato
• Excessive Damage
• No recovery system deployment or tangled recovery system deployment
• Rocket drifting outside the specified launch range
• Components coming down not attached to the recovery system.
• Any other violation of TRA safety code associated with this particular flight.
• Any other legitimate reason the TAP member deems merits non-certification.

Click to expand...

Bat-mite said:

Where are you getting that, Eric? I don't see main at apogee in the list of qualifications:

Click to expand...

Hmmm, Hi John,

I need to go into investigative mode. It was what I've been taught for the last 15+ years in HPR....though you're right I can't find the exact verbiage right now. I'll do some digging. In the meantime, a thought to ponder. From the Tripoli website:

The candidate needs build, fly and recover successfully a rocket using a certified HPR motor in the M-O impulse range.

As you know, the pre-flight documentation is to outline the functionality of the rocket's design including recovery. If the recovery system does not function as intended, is it really a "successful recovery"?

I think I'm painting myself as a curmudgeon in this thread.:wink: I'm really not, as I think those that know me will attest. Anyway, as for the L3 attempts I've been fortunate to partake in, we're 100% successful so far (so I'm not really the nit-picky hard-*ss as I might appear).

Cheers, and congrats on the 1 year 1 month anniversary of your L3 today!

ECayemberg said:

Valid point, Kurt. See, I knew I was posting grumpy this morning!:wink:

I am all for learning; that's what makes a place like TRF great! Learn from others' victories and losses. My main point is that we have 5 pages of replies of speculation without any concrete evidence of what actually went wrong (except for tracker related issue...good content there). Apologies as my opinion is driven by a career that is largely based on problem solving. IE: something *bad* happens, we reflect, determine root cause(s), assign corrective actions, and so on. It's really hard to generate meaningful corrective actions without understanding what actually went wrong. I parallel this thread to that concept.

Creating change without understanding the problem tends to make chaos. Not saying this is chaos, but there's a whole lot of armchair quarterbacking going on...and it frustrates me when people say you can or can't do x based upon computer stuff...some things you just gotta get out in the real world and live and learn through trial and error. Sims and formulas are great, but by actually doing is where true learning is derived.

Rant off. Don't let me be a downer; I'm looking forward to learning as well. Just don't go changing everything without understanding what needs changing!



Nate, not sure if I understand this statement exactly. If your design calls for dual deploy where the main is deployed at low altitude (1000' agl for example) and the main is dumped at apogee, the cert is void. One doesn't need traditional dual deploy for an L3 attempt (or the other levels for that matter), but the flight events have to function as intended in order to be a "successful" attempt.

Click to expand...

I thought I had read about the "main at apogee" was discussed at the BOD level at Tripoli and the certification could be allowed if the rocket landed inside the waiver area. I do distinctly remember a post from an irate TAP that strongly disagreed with this.
Firstly, if a main is dumped at apogee up high, especially if the flier is using a large a chute as possible, most likely the rocket is going to drift out of the waiver radius. My local field is 1 mile. QCRS it's 2 mile radius. So as far as I know, that is the hard and fast fact. Heck technically if one has a totally successful DD certification flight, if it drifts out of the waiver radius, it's a failed certification attempt. Good reason to lose that GPS file or be dumb if 10 feet out of bounds on a successful flight!:lol::bangpan::surprised: Secondly, I can appreciate the TRA BOD's view on this of cutting some slack. (I think that is true) If the rocket lands within the waiver under main at apogee in an otherwise DD rocket, it's good as long as it's flyable with no damage. Heck, I've seen plenty of L3 people go off after a successful cert and have some surprisingly less than nominal flights! An unfortunate main at apogee of a flight that is lucky to land within a waiver, the flier is probably going to try their darndest not to repeat that action next time. (Especially since there is a good chance the cause can be found after recovery.)

Me thinks Matt's rocket landed outside of the waiver radius but I don't know what the true number is at that venue. I don't think the waiver is 5 miles though. Probably 2 or 3?

The other thing that speaks to the maturity of the answers here is no one accused the TAPs or said it was "their fault" the tracker battery issue was missed. Taps can't "know" about every bit of tracker technology nor are they
expected to "know" everything there is to know about every deployment device there is out on the market. Their job is to be reasonably certain that the candidate rocket is in a position to have a safe flight. It behooves the
candidate to read all the instructions of all the hardware and practice with it. Certainly if the TAP is familiar with a particular tracking device I'm sure they would have been emphatic about the simple 2S battery fix that would
have improved Matt's chances. As I said, I don't think every TAP can know everything and it shouldn't be expected.

I think the discussion here pretty much narrowed down the possible chain of events that gave the unfortunate attempt. The battery issue is a known given with a great degree of certainty. The electronics and shearpin explanations
carry a bit less weight but instituting cautions to avoid the outcomes postulated will greatly increase Matt's success on a second attempt. (Especially the contention of using two different deployment devices to avoid one of the possibilities another poster mentioned.) I bet Matt pulls it off with no trouble next time. Perhaps builds and flies a few smaller HPR's to accumulate some tracker experience before the next cert attempt. I'm still learning
about that each time I fly a tracker. Kurt

I've tried to stay away from posting in this thread, purely from a "don't clutter it *** point of view, but I have to chime in on the altimeter thing. I use a RRC3 and RRC2+ combination in a bunch of my rockets. Don't ask me how many pairs I have set up, because I have them spread all over the place At least 4 pairs I think. And I definitely used this combination in my L3. I've always observed the delay in the charges. There is however, the possibility that his primary drogue charge set off the backup charge though. I don't think I've seen that mentioned. I apologize if it has been mentioned, but I just wanted to point out the altimeter thing.
OK, now that I've said that, I feel better. I'm sure you guys feel better that I feel better... :eyeroll:
But, seriously...
Matt, I'm sad as all hell that you lost your rocket. That sucks big time. I'm also happy about the attitude you have going forward. I've no doubt that you'll be successful on your next attempt. Why don't you take the weekend off from college this fall (it's not that important, is it? :wink: ) and come fly with us at Midwest Power this fall...
Good luck and keep up the good attitude!

OK why can't I say " don't
clutter it



up "





in a sentence????
WTF???


In my post above, there are no swear words in that sentence. No spaces either and it gets censored???
This is the only way I can post it and not have it censored...
However, later on I say HELL and that's OK????????

NateLowrie said:

For my level 3, I had the same vent hole configuration you did. I ran the calculations through a program I built. You can see the results in my documentation on my thread. Basically, it works like this:

• Sim the rocket on you motor in Rocksim or OR and export the atmospheric pressure data over time to CSV.
• The program takes the number and size of the holes calculates the pressure differential change rate through the vent holes.
• It then takes the rate of atmo pressure change from the CSV export and calculates the payload bay pressure at each point using the different exchange.
• It takes the pressure differential and the internal area of the nosecone to calculate the force differential.
• It plots atmospheric pressure and force on nosecone from pressure differential for the flight on a graph.

I then size holes and shear pins accordingly. The force differential on my flight was 20lbs and your's is no more than 30lbs max and probably less than 10lbs at deployment. It's not a factor.

Click to expand...

Nate , care to share this program? If you do, shoot me a PM. Happy to host it on rocketryfiles.com

jd2cylman said:

There is however, the possibility that his primary drogue charge set off the backup charge though. I don't think I've seen that mentioned. I apologize if it has been mentioned, but I just wanted to point out the altimeter thing.

Click to expand...

I've definitely done this before. both in ground testing and in the air.

jd2cylman said:

come fly with us at Midwest Power this fall...

Click to expand...

+1 on this.. plus you get to visit Princeton, IL- one of the most interesting towns in the country, if not the world.

+2 to this. I'm targeting MWP this fall for my L3 flight. I was at MWP last year. Great place.

The rocket is not lost, it's just not found yet. I have hope that it shows up sooner than later.

blackbrandt said:

I had apogee and apogee +1 sec.

Click to expand...

claytonbirchenough said:

That's good. Still doesn't rule out both going off at the same time though...

Click to expand...

blackbrandt said:

This was one of my theories, except that I was flying the same brand of altimeter (RRC3 and RRC2+), which means that the algorithms for determining air pressure should be either the same or really close to the same. If I was flying 2 different brands of altimeters, this theory would be more pressing.

Click to expand...

Altimeters, even of the same make/model, rarely give the same result. There can be 1 second of apogee error between the two. One altimeter with four deployment channels to handle the primary and backup charges may be a better approach. The single altimeter logic will ensure the firing sequence you want. I am using a Raven for this purpose.

Also, if the charge amount is correctly ground tested or test-flown, are two apogee charges really needed? I've read stories on the forum of one charge igniting the backup next to it, causing havoc. Two ematches are a good idea, but I am not sure about two charges. Methinks redundancy increases the chance for failure.

Buckeye said:

Altimeters, even of the same make/model, rarely give the same result. There can be 1 second of apogee error between the two. One altimeter with four deployment channels to handle the primary and backup charges may be a better approach. The single altimeter logic will ensure the firing sequence you want. I am using a Raven for this purpose.

Also, if the charge amount is correctly ground tested or test-flown, are two apogee charges really needed? I've read stories on the forum of one charge igniting the backup next to it, causing havoc. Two ematches are a good idea, but I am not sure about two charges. Methinks redundancy increases the chance for failure.

Click to expand...

One charge setting off the other is actually a reasonable theory. When I ground tested, I only loaded one charge. This will be a good thing to test in the future on redundant altimeters.

The only reason I was using 2 altimeters was because it was required for the L3 flight.

blackbrandt said:

One charge setting off the other is actually a reasonable theory. When I ground tested, I only loaded one charge. This will be a good thing to test in the future on redundant altimeters.

The only reason I was using 2 altimeters was because it was required for the L3 flight.

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This should not be a problem if the charges are prepped correctly. Best are separate hard wall containers (aluminum or PVC) spaced opposite of each other on the av-bay bulkhead. Problem is many don't secure the charges. If you cover the end with aluminum tape you will be "golden." Similarly with non-contained latex glove ends, balloons or I even do it with my centrifuge vials; put a single wrap of aluminum tape around the backup charge (both charges if you want). You will never get simultaneous ejection (unless you have you have same altimeters that are set the same).

The only reason I was using 2 altimeters was because it was required for the L3 flight.[/QUOTE]

Matt , two altimeters are NOT required for a certification flight . Back in the day , motor ejection with a timer backup was pretty common. There is no reason you cannot use a single altimeter and a single event timer for your drouge back up . This is the exact same way I did my cert three flight. One perfect flight MAWD and a perfect flight single event timer . I used one charge per section.


Eric