Dual Deployment for Close Proximity type Recovery

lizardqueen wrote: > Does anyone know of an > altimeter, capable of firing and ejection charge at a given altitude > (on decent would be best : ) ) that doesn't cost a fortune.

PerfectFlite has a new altimeter, the HiAlt45K, for $80. I haven't used this one but I've been quite pleased with their other products.

The Transolve unit is the P6K that was an easy kit to build. I have one. Haven't flown it yet. It is quite a bit larger than the Perfect Flight MAWD unit but in a 3 or 4 inch model shouldn't be a problem. Was $68.00 so might be the most economical dual deploy out there. Feel free to correct me here in case I am wrong. Says on the site that the sensing unit is not available. If it is an end of life issue, John will have to come up with some sort of alternative.

The Perfect Flite MAWD has the computer interface that the HiAlt45K lacks. The HiAlt does do peak reporting.

Kurt

PerfectFlite has made reliable products, so I expect the HiAlt45K should be very reliable.

Frankly, the biggest source of error is the human who builds and preps the rocket and installs the electronics. Forgetting to arm an altimeter is a common failure mode. Using poor-quality arming switches is another.

Assuming you are using motor ejection to pop the drogue parachute, then the penultimate worst-case recovery scenario is the rocket lands on the drogue. (The worst case is the motor ejection charge doesn't work, nor does the altimeter.) Some people argue that you should either use motor ejection or altimeter, not both. I don't agree, but I bet we'll hear opposing opinions shortly. :-)

Redundancy is good, though I'll stop short of calling it necessary for the L1-L2 range of rockets. It becomes more important as your price for the rocket increases. :-) If you do go with redundancy, I'd go with a timer to pop the drogue. Next step up would be a 2nd dual-deploy altimeter.

For your first foray into electronic deployment, I'd stick with motor ejection for the primary deployment and a single altimeter for secondary deployment. Keep the flight low (but a couple hundred feet higher than the main-deploy altitude), and use a large enough drogue to land the rocket fast but safe in case the main fails. Do that a few times successfully and you'll gain valuable experience and confidence.

Loud beepers, i.e. repackaged personal alarms.

Just a thought...

Spend $12 on a Pratt Hobbies Micro Beacon

Or spend a couple hundred on a Garmin Vista (or other model with Site-N-Go) GPS. My wife now says mine has paid for itself since I used it this past Saturday to find my daughters US Record setting 1/2A Helicopter Duration model in the cornfield across the street from the NARAM-49 site.

For HPR, I'd use BOTH if there was corn or soybeans nearby.

Nope... worst case senarios with ANY deployment with altimeters is no deployment at all and the rocket comes in ballistic!!!

I've seen it more than I can count on my hands & feet. Failures are due to such things as dead batteries, batteries falling out under accleration, improper setup of altimeter, bad instructions from the manufactuer, short circuits (in deployment charges), failure to actually arm the altimeter, failure to put BP in charge, use of Pyrodex instead of BP, mixing up primary & secondary charges, altimeter installed upside down, etc, etc, etc.

That's why I always suggest that one does everything they can to reduce failures such as: * Always use a NEW battery that's been tested with a volt meter * Make sure the battery is positively held in place * Test the deployment ON THE GROUND with any new setup * Use a launch time check list.

DSC

I am thinking that if you combine the altimeter with conventional motor ejection that the chance for the rocket coming in ballistic is no greater than any other conventional launch, because the drogue shoot will still be deployed by the motor's ejection charge. Am I missing something? Thanks all, Laura

Hi Laura: Dual-deploy will certainly help you keep landings closer to the launch pad. As others have noted, careful design, testing, and checklists are your friends! 8)

If you can see the rocket land note the exact direction using a distant object as a reference. Or take a compass bearing. Then walk that line until you hear the beeper.

Tracking transmitters are a nice backup. You can find the airborne hardware in the $50 to $800 range. Ham radio receivers are very inexpensive, or you can probably get a free unit by visiting meetings of the local amateur radio clubs. The commercial receivers tend to be a bit more expensive.

I use the

lizardqueen wrote:

When using dual deployment I almost always use the motor ejection as a backup... although sometimes the motor ejection will fire before the altimeter's primary, so in that respect the altimeter is the backup. On one occasion I had the upper stage motor of a 2 stage rocket blow the forward closure and if not for the altimeter the upper stage would have been toast.

DSC

If I use motor ejection for a backup to altimeter drogue deploy, I'll use a longer delay than normal. My theory is, that the altimeter is the "prime" and the motor is the backup things should happen at the correct time.

Without this "plus delay" in the motor eject, the ejection could occur too early, but with it, it "should" occur when the chute is already out. It's truely only a "backup"

In reality, after getting experience with both the altimeter and launch procedures, most times I don't use motor eject, and you can't with larger AT motors anyway!

As far as procedures, one thing I do is tie a ribbon on the bird (1" colored plastic tape sold at Home Depot in rolls - used to mark trees - and can be used as streamers in estes birds, etc) when I'm prepping. The ribbon can be seen from the flight line, and does not come off until the bird in on the pad and armed. It eliminates forgetting to arm, as you can see it from a distance.

Another "procedural" thing is that during prep, power up the electonics before you add the BP, but after the ematch is connected. Be forwarned, that if there is a problem, the ematch will pop, but it's much less than if the BP had been added. When the continuity checks have passed, power off the altimeter, and then add the BP

While I might have missed it, one thing in dual deploy that should be considered are "sheer pins". They're used to hold in the Nose cone until main deploy (assuming the main in in the payload bay). I use small styrene rods, but some folks like #2 nylon screws. When the drogue deploys, the payload section can have a bit of stress, and the main might eject at apogee without the pins.

Also, remember to add vent holes to the altimeter bay!

As far as HW, I've always liked the Missleworks stuff. I think they're still in business. The version with the battery clip on the altimeter is the easiest to use. The "external battery" version can have a problem if the battery is connected improperly (like the ejection charges fire when the unit is powered up!)

The Missleworks manual is also good, even if you don't have a missleworks unit. It goes into different methods of dual deploy, and aides in the calculation of vent holes, and the size of the charge needed.