Rocket Electronics

[theman11]

Hey,
I am getting into the hobby of rocketry and so far it has been very fun. I would like to try using some electronics in my rockets but am still somewhat of a newbie. I would like to try placing an altimeter or gps in my rocket and then possibly program it to control the rocket. Are there any electronics available which could read the altimeter data and cut off the engine at an altitude of about 500feet? Also is there a way to deploy the parachute or seperate another section of the rocket electronically without having the ejection charge on the blackpowder engine fire?
Thanks,
theman11

 

[TheAviator]

Cutting off an engine can only be used on an engine where you actually have control one or more of the propellants. Such control is not the case with pretty much any solid rocket motor (including the full size ones.) It may be possible to do this with some high-power hybrids, but only with modification, which puts that topic outside the realm of this forum.

As to not having the ejection charge fire, there are a couple of "plugged" black powder engines out there (Estes D11-P, Quest D5-0 [really a P]) or you could get an Aerotech 18/20, 24/40, 24/60, or 29/40-120 casing and leave out the ejection charge when you load a motor. However, it is wise to get an overly long delay and simply use the motor ejection as a back-up.

If you want a recording altimeter that is very capable, check out the Featherweight Altimeters Raven. As far as I know, it is the smallest altimeter with the level of programmability that the Raven has.

 

[The EGE]

There are altimeters available that can fire charges to eject parachutes, both at apogee and at a preset altitude.

Some altimeters have multiple outputs and can eject a small parachute at apogee and a larger one at a lower altitude; this allows for a soft landing while minimizing drift and is called 'dual deployment'. It's most used for large, high-altitude rockets.

There's no way to have electronics cut off the motor. A solid-fuel motor cannot be extinguished once lit; it just burns out when the fuel is exhausted. Only liquid-fuel rockets can be turned on and off, but we don't use them in hobby rocketry for safety reasons.

Blackpowder motors and single-use composite motors cannot be modified to remove the ejction charge; you would have to buy a plugged motor like the D11-P or E15-P. With a reloadable motor, you simply don't put the ejection charge in while building and simply use the electronics to deploy the parachute(s).

 

[DM1975]

Hey,
I am getting into the hobby of rocketry and so far it has been very fun. I would like to try using some electronics in my rockets but am still somewhat of a newbie. I would like to try placing an altimeter or gps in my rocket and then possibly program it to control the rocket. Are there any electronics available which could read the altimeter data and cut off the engine at an altitude of about 500feet? Also is there a way to deploy the parachute or seperate another section of the rocket electronically without having the ejection charge on the blackpowder engine fire?
Thanks,
theman11

Your best/only bet to cut an engine off at 500 ft would be to use a motor that will only bring the rocket to that altitude. No electronics needed for that one and the motors ejection charge would also work fine to deploy the parachute.

 

[Larry Curcio]

Hey,
I am getting into the hobby of rocketry and so far it has been very fun. I would like to try using some electronics in my rockets but am still somewhat of a newbie. I would like to try placing an altimeter or gps in my rocket and then possibly program it to control the rocket. Are there any electronics available which could read the altimeter data and cut off the engine at an altitude of about 500feet? Also is there a way to deploy the parachute or seperate another section of the rocket electronically without having the ejection charge on the blackpowder engine fire?
Thanks,
theman11

Just wondering why you would want to cut the motor at 500 feet. Is it to make the rocket rise to that altitude and stop?

If so, it won't work. Your rocket will keep going.

 

[theman11]

Since I see that is difficult or impossible to cut off the black powder motor, would it atleast be possible to cut off thrust by allowing for the exiting gases to be spread out evenly on the sides instead of being allowed to exit out of the back at a certain altitude and then deploy the chute? Would I be able to program the Raven GPS to control something like a micro servo to cover the exhaust with some nonflammable material?
I would like to try and get some more control and precision over my rockets when I am launching them and have a few launch and deploy in unison in the air. 500 Feet was just an example, I would like for it to be programable so it could deploy at any altitude I set, 500ft, 1000ft, or higher.

 

[DM1975]

I am sure you could, but it would be easier to just use the proper motor to take the rocket to the altitude you wish in the first place. Occams Razor comes to mind.

 

[troj]

Since I see that is difficult or impossible to cut off the black powder motor, would it atleast be possible to cut off thrust by allowing for the exiting gases to be spread out evenly on the sides instead of being allowed to exit out of the back at a certain altitude and then deploy the chute? Would I be able to program the Raven GPS to control something like a micro servo to cover the exhaust with some nonflammable material?

Anything that would deploy such a mechanism would be heavier than a black powder motor can lift. In addition, without a thorough program of testing on stands, I can't imagine the typical RSO would allow you to fly such a thing.

I would like to try and get some more control and precision over my rockets when I am launching them and have a few launch and deploy in unison in the air. 500 Feet was just an example, I would like for it to be programable so it could deploy at any altitude I set, 500ft, 1000ft, or higher.

That level of precision is difficult with the motors we have available -- too much variation. You're talking a fairly precise goal.

A better choice would be a group of identical rockets on identical motors, each selected to give the altitude you're after. Much more reliable, and much safer.

-Kevin

 

[blackjack2564]

You must also consider that even if you could shut down the motor at 500ft. the momentum attained under thrust would carry the rocket much, much higher.
However by designing a short fat rocket and a little motor matching skill your project is very doable.

A spool rocket or saucer with air brakes come to mind as a first step. You can easily hit predetermined low altitudes with one of these designs. Quite cheaply I might add. Keep in mind that even using the same motor over and over can yield different results due to flying conditions. [wind, temperature, humidity, etc] Even the motors themselves will show some degree of performance variance unless they all come from the same batch.

A little building experience and a good simulating program and you should be able to attain your goal.

One of the fun things about rocketry is stretching the boundaries .

Rocketjunkie designed one that reliably and repeatedly will fly close to a mile[5280ft] within 80-200ft!