Air Starts

[davalf]

I am getting ready to start my LOC magnum and I want the capability of air starting the 29's. I was wondering how others have set up there rockets. I was thinking of running a condoit through all 3 centering rings and having a terminal attached to the aft centering ring. Then having a wire attached to the terminal and running up to the altimeter. Has anyone done something similair? During deployment, what happens to the wires? And what have you used for condoit in the past, copper? Thanks.

Dave

 

[ben_ullman]

I am getting ready to start my LOC magnum and I want the capability of air starting the 29's. I was wondering how others have set up there rockets. I was thinking of running a condoit through all 3 centering rings and having a terminal attached to the aft centering ring. Then having a wire attached to the terminal and running up to the altimeter. Has anyone done something similair? During deployment, what happens to the wires? And what have you used for condoit in the past, copper? Thanks.

Dave

#1 Altimeters are not for airstarting timers are*

#2, what you are describing is pretty much the way to do it. There are variations of his but thats basically it

*There are altimeters with airstaring abbilities.

Ben

 

[davalf]

#1 Altimeters are not for airstarting timers are*

*There are altimeters with airstaring abbilities.

I know this.

 

[FredA]

#1 Altimeters are not for airstarting timers are*

BUZZ -- WRONG!!!

Timers are a CRUDE way to do airstarts.
Altimeters are the SMART way to initiate them....use the computer in your flight computer.

Timers are static based on simulations that are loaded with many assumptions....flight profile, motor burn times, etc.... All static and all could be far from the actual flight profile.

Altimeters will fire airstarts based on what is really happening to the rocket.

Sure -- NASA uses timers -- but they also have more more predictable motor performance, guidance and a RSO with a his finger on the self-destruct.

Using an altimeter, especially a single altimeter, requires more creative wiring, but it can be done.
Start by trying to use an altimeter....if you fail you can always retreat and use a timer.......but don't start with a timer.

 

[new2hpr]

Granted, the most elegant solution is a true flight computer including altimeter and airstart control (RDAS, FW Raven, etc.).

However in the spirit of KISS, an easy way that I've used is just as you described. I had a timer bay under a hatch near the rear of the rocket (38mm mount in 4" airframe left lots of room) and internal conduit to the rear centering ring. The bay was close enough to the rear that the ematch leads from the airstarts (Pro38) could reach the timer, thus no terminal blocks needed. Keeping the airstart functionality separate from the dual-deploy altimeter electronics was the only cost effective option at the time. New stuff comes out all the time, and if I were to do it over, I'd probably use a Raven and creative wire disconnects between the altimeter bay and the booster.

:2:
-Ken

 

[ben_ullman]

#1 Altimeters are not for airstarting timers are*

BUZZ -- WRONG!!!

Timers are a CRUDE way to do airstarts.
Altimeters are the SMART way to initiate them....use the computer in your flight computer.

Timers are static based on simulations that are loaded with many assumptions....flight profile, motor burn times, etc.... All static and all could be far from the actual flight profile.

Altimeters will fire airstarts based on what is really happening to the rocket.

Sure -- NASA uses timers -- but they also have more more predictable motor performance, guidance and a RSO with a his finger on the self-destruct.

Using an altimeter, especially a single altimeter, requires more creative wiring, but it can be done.
Start by trying to use an altimeter....if you fail you can always retreat and use a timer.......but don't start with a timer.

Thats what I threw in the that little footnote. Otherwise the way he wordered if i pictured airstarts being hooked up to the apogee terminal on an altimeter :jaw:

Ben

 

[leegscott]

Not sure if it will help but attached is a build thread to a cluster build that my son and I built several years ago. We also posted a upscale THOR build with cluster but I could not find it in the archive. Regardless, hopefully it will help. We like using timers and have not had a problem yet.


https://www.rocketryforumarchive.com/showthread.php?t=41930&highlight=upscale+nike+smoke

 

[5x7]

I am really happy with the way I set mine up for airstarting. I added two 38's (tight squeeze) and 2 24's to the 29s, so it was a bit extreme, but the method worked great. I added a timer bay above the fins with mounts for two timers, and ran wires from the timers to two lower terminal block bays mounted further down. The igniters were wired to the terminal blocks and the igniters ran from the terminal bays through 2 aluminum tubes out the aft centering ring. Once the wires exit the tubes, they were protected with masking tape.

 

[davalf]

First off, Lee that was a beautiful nike. I like the timer mount you made and am considering doing the same. 5x7, do you have any detailed pictures of your rocket? thanks

Dave

 

[leegscott]

Dave

Thanks

I have quite a few pictures but I am not sure what you mean by detailed pictures! Let me know and I would be glad to send you what I have.

 

[Warthog]

I am getting ready to start my LOC magnum and I want the capability of air starting the 29's. I was wondering how others have set up there rockets.

I built an upscale (5.38" body diameter) LOC Starfighter with a central 54mm motor tube and four outboard 38mm tubes. I considered using my dual altimeters to handle the airstarts but that would have required that I run wiring from my altimeter bay to the aft bulkhead. I did not see a good way to do that so I put in a timer bay near the aft end and ran two 1/4" diameter aluminum conduits form the timer bay to the aft bulkhead. Wiring from the timers goes through the conduits and has enough extra length to simply twist my igniter leads on to them. The conduits are terminated at the bulkhead with short pieces of 1/2" PVC pipe with push-on 1/2" PVC caps. I twist the wires and insulate then with electrical tape. Then the connection gets placed into the PVC pipe and the cap is pushed on. After the flight I just cut off the connection.

I have two timers for four outboard 38mm motors. Sometimes I load up all four or I can just use two outboards.

 

[dixontj93060]

Beautiful!

I built an upscale (5.38" body diameter) LOC Starfighter with a central 54mm motor tube and four outboard 38mm tubes.

 

[davalf]

Warthhog, that is a very nice rocket. I think I will be doing the same with a timer bay near the rear. On Lee's Nike smoke he used an extra piece of airframe to make the hatch for is timer bay. Is there any reason you can't use the piece you cut out? Thanks to all for the advice.

Dave

 

[new2hpr]

Here are some build photos of Excess In Moderation (in my avatar) which started out as 38mm + 6x 24mm. Is now 4x 38mm. Airstarts and clusters rule!

https://s424.photobucket.com/albums/pp321/new2hpr/Rocketry/Excess%20In%20Moderation/
-Ken