Redundant Electronics

[Wiley]

How necessary are redundant altimeters to a successful DD recovery? I know that a lot of people use a redundant altimeter for reliability, and this concept makes sense. Nevertheless, I was wondering how often this redundant altimeter is actually needed; i.e. when the primary one fails in some way to deploy the laundry. How many of you fly with just one altimeter? Success and failure stories are welcome.

[dixontj93060]

I fly in non-redundant mode probably 2/3rds of the time. Larger, more expensive or critical flights will be redundant.

[csoechtig]

I heavily researched this topic when I first got into dual deployment. In fact, you can find 2 or 3 threads in the forum archives with a variety of perspectives.

In general, most flyers use redundancy in large, expensive builds. You should look at it as an insurance policy to protect your investment.

I have 4 rockets with dual deployment and am building my 5th. I set up redundancy in my extended 5.5" Big Nuke and my extended 4" LOC IV. Smaller tubes can be dificult to pack it all in there.

I suggest you ground test all new altimeters with a shop vac on the port hole. Also, make sure you have new batteries for every launch. The combination of these two things will give you a high level of confidence.

I have witnessed very few altimeter failures at club launches. Usually, it is user error (wiring incorrectly).

[JDcluster]

If it's your only means of recovery you probably want some sort of insurance.
Any rocket >4" on up I use 2 altimeters or more. Anything under 4.0" is kind of hard to do. Most of my 4" rockets have flown on one altimeter.

Weight being one of the key elements for redundant systems.


JD

[Wiley]

As I said, redundant altimeters make sense, but I do not understand the replacement of the battery after each launch. I have heard this suggestion before, but throwing a four dollar battery away seems kind of wasteful .

[atxcple]

As I said, redundant altimeters make sense, but I do not understand the replacement of the battery after each launch. I have heard this suggestion before, but throwing a four dollar battery away seems kind of wasteful .

4.00 (battery) versus 600.00 adverage (rocket motor case, parachutes, electronics.) the flow chart that determines this would include,

which altimeter?

power drain at startup / diagnostics?

current needed for ematches / deployment charges?

how long are you sitting on the pad with power to electronics?

how long was it beeping out readings waiting for you to find it and power down?

my answer to this always is new battery / fresh recharge every time!!

[csoechtig]

As I said, redundant altimeters make sense, but I do not understand the replacement of the battery after each launch. I have heard this suggestion before, but throwing a four dollar battery away seems kind of wasteful .

Last month I was prepping for a launch and turned on my Stratologger Altimeter. The last series of beebs gives you the battery voltage. Typically, it beeps 9.2 or 9.3 times. In this case, it beeped 3.5 times. I tried again and got the same thing. When I replaced the battery, it jumped to 9.2. I found that strange considering I only used the battery on 2 launches.

Of course, you can trust the altimeter readings. However, considering that battery is powering your entire recovery system, $4 is cheap peice of mind.

[rocdoc]

As I said, redundant altimeters make sense, but I do not understand the replacement of the battery after each launch. I have heard this suggestion before, but throwing a four dollar battery away seems kind of wasteful .

A few thoughts:

First, I always buy the Duracell Procell batteries. They come bulk packed in 12-packs for only a buck or two each instead of $4 each. Here is a link to some I found with a quick Amazon search:

http://www.amazon.com/gp/product/B00...FYGGNR0MYPZ2PT

Second, I always use new batteries for each flight. As was stated by others, it is cheap insurance for a project that likely cost hundreds or thousands of dollars to launch anyway.

Third, I almost always use redundant electronics. Only reason not to is for super small rockets. You can throw a couple of Ravens in a really small space.

Fourth, if you are concerned about the waste of batteries, you have two options: You can usually power altimeters with rechargeable LiPo batteries which you can then reuse or you can do what I do and pop the "used" 9V batteries into your home smoke detectors to ensure that they always have a relatively fresh battery.

[SMR]

As I said, redundant altimeters make sense, but I do not understand the replacement of the battery after each launch. I have heard this suggestion before, but throwing a four dollar battery away seems kind of wasteful .

I recommend to use fresh batteries, but don't waste them. I rotate them, like rocdoc does... new ones go in rockets, and if they still still test good afterwards, they go into other things... smoke detectors, toys, radios, etc.

As for the redundancy question, if a hypothetical critical subsystem failed once in a hundred attempts (1%), that would still be a high failure rate. But doubling the subsystem doesn't just cut the total system failure rate in half (0.5%). Since the 1% failure would not likely be at the same time in both subsystems, the total system failure rate actually approaches 0.01% (one in ten thousand).

In 70 high power flights, I have had ONE ematch fail to fire. If it had been the only one, the rocket would not have had deployment. A redundant altimeter fired the backup charge, which paid for the extra altimeter four times over.