Staging

[MikeSModerator]

I plan on having a 4″ rocket flying by Oktoberfest.

Based on an Aerobee 350.

Booster will be an H motor. The sustainer 3 29mm.

The booster will be 3″ and the sustainer will be 4″.
PET2 timer. All engine ejection.

I will be glad to see some info on staging come up.

[Sparky2Participant]

With the configuration of the PML kit as is I would have to redesign the electronics bay to make room for the timer in the sustainer. Another question I have is the booster ejection timing. On a Cessaroni I can lengthen the timing so seperation has for sure occured but what if I use an Aerotech motor in the booster?

[James Russell]

Missile works PET is basically two timers in one, I have used it air start to different sets of motors, they work great.

I think you are asking on how do you recover the booster then, I would use electronics but there are different delays and AT has certified delay cutting just like CTI, if you go to their web site you can find the details.

[Warren B. MusselmanModerator]

Sparky, a minor but important point. You cannot lengthen ANY delay, you can only shorten them. If you want a longer delay for an AT motor, you buy the long delay for that motor. If that’s too long, you use the Aerotech tool (just like you would with Cesaroni) and shorten the delay by drilling a small hole in it to the appropriate depth for the length delay you desire.

Warren

[Robby]

I just got a Cosmodrome Aerobee Hi kit and it doesn’t come with instructions for staging electronics. If anyone knows someone or has built and flown this kit themselves I would like to know how you configured the electronics. Being new to high power I thought for sure someone here would have a good set up that they like and trust to use. The booster is separated from the sustainer by three struts connected to an interstage coupler that goes inside the sustainer, definately no Estes gap staging here! That is when you know you have taken that giant leap forward in the hobby and stepped up to a new level of complexity.

How do you then ignite the sustainer? Will a 9v battery ignite an Aerotech First Fire Jr. igniter? What do you use? From what I have read so far in this forum the construction method would look like this: (1) sustainer will house the timer, (2) the booster will have a motor with an ejection charge that will deploy it’s own parachute, (3) the sustainer will blow off the booster. In this configuratiion it looks like the timer needs to be set to ignite the sustainer before the booster motor pops a paracute.

Thanks for any info especially on what battery and igniter to use for the sustainer.

Robby

[James Russell]

Robby,

the way I would try to do it is:

booster lights and burns for …sec.

Timer fires a separation charge
booster is now on its own, motor or electronics will deploy chute

Sustainer will then light at the set delay
(not to long that the sustainer looses to much velocity)
Motor or electronics will deploy chute for recovery of sustainer

The type of igniter and power source will have to be tested and you will need to test each igniter to make sure the ohms are the same every time.

One note though, if you are using motor ejection for recovery of the sustainer you will have a lawn dart if you fail to light the motor so I would recommend electronics as primary recovery of the sustainer.

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