"Single" Deployment Rocket. Questions from a newbie.

[BM1993]

Hey all!

I'm new to the forum, as I am to professional rocket building. Although I have a fair bit of experience in motor making and building my own rockets from scratch, I have never yet ventured into the realm of professional electronics controlled high power rocket building.

I have many questions, which I will be posting in the appropriate sections of this forum. For this section, my question is the following:

How should I design my rocket for single deployment at apogee? (no drogue,
only main)

Where would you recommend housing the parachute? Under the nose cone, or under the bulk head (alt bay)? What tips do you have for such a set up to work correctly?

How should I install the shock cord for your proposed configuration?

How do you recommend to set up a RRC3 controller to work for this specific set up?

I would like for the parachute to deploy at apogee. Also, what size chute do you think I should use for a 2.5" diameter rocket?

That is all for now, thanks!

B.

 

[neil_w]

]Also, what size chute do you think I should use for a 2.5" diameter rocket?

Parachute size is based on the weight of the rocket and desired descent speed, not diameter. There are multiple rocket descent calculators available on-line, just search and you'll find them. You can also use a sim program (OR or Rocksim) to do that for you. Of course, you should already be using one of those programs to design your rocket.

 

[boatgeek]

I'm new to the forum, as I am to professional rocket building. Although I have a fair bit of experience in motor making and building my own rockets from scratch, I have never yet ventured into the realm of professional electronics controlled high power rocket building.

Welcome!

Where would you recommend housing the parachute? Under the nose cone, or under the bulk head (alt bay)? What tips do you have for such a set up to work correctly?

Either below the nose cone or below the altimeter bay works. It's up to the rocket design, how much space you have in both places, whether you'd want to use motor eject as a backup, etc. Whichever you choose, you will want the forward section closer to the parachute than the fin can so that the nose section and the fin can can't hit each other in the air. The fin can also hits the ground first.

How should I install the shock cord for your proposed configuration?

I would run the shock cord/recovery harness to the altimeter bay from either the nose cone or the motor mount, depending on where you're putting the parachute. I like to add a short chock cord to the other side in addition to rivets for a backup.

How do you recommend to set up a RRC3 controller to work for this specific set up?

I don't have enough experience with RRC3s to say for sure. If you are able, it would be nice to have one charge at apogee and one charge a second or so later so that you have some redundancy.

 

[dhbarr]

If you're only doing a single event with the RRC3 at apogee, just build it like a normal model rocket more or less. Your electronics can go below the parachute if you're not planning on using any motor ejection charge, or above the parachute if you are planning on using motor eject as backup.

 

[cbrarick]

I'd get a copy of "Modern High Powered Rocketry" by Mark C. Most of the questions you would ask will be answered with words and pictures.

 

[mtnmanak]

https://www.mountainmanrockets.com/index.php/hpr-primer/

 

[BM1993]

I would run the shock cord/recovery harness to the altimeter bay from either the nose cone or the motor mount, depending on where you're putting the parachute. I like to add a short chock cord to the other side in addition to rivets for a backup.

Thank you for answering my questions. As to the "rivets" to hold on to the lower body and altimeter bay together, what should these be? Would you use shear pins or screws, perhaps?

After what you said I decided to go for the chute between the alt bay and nose cone, and also attach the lower portion of the alt bay with shock cord to the motor mount for redundancy.

B.

 

[lakeroadster]

.....

Where would you recommend housing the parachute? Under the nose cone, or under the bulk head (alt bay)? What tips do you have for such a set up to work correctly?

Typically, on rockets that utilize a lot of nose weight, I sometimes have (2) parachutes, one for the nose cone and a separate chute for the fuselage / fin can sub-ass'y.

That way there's virtually no way the heavy nose cone can smash the rocket.

This also allows for different ground hit speeds. Nose cones are typically pretty durable. Fin cans and body tubes, typically not very durable.

.....

How should I install the shock cord for your proposed configuration?

I like to anchor the shock chord to the motor mount, and make it removable, as shown below.

 

[boatgeek]

Thank you for answering my questions. As to the "rivets" to hold on to the lower body and altimeter bay together, what should these be? Would you use shear pins or screws, perhaps?

After what you said I decided to go for the chute between the alt bay and nose cone, and also attach the lower portion of the alt bay with shock cord to the motor mount for redundancy.

B.

Metal screws are fine. Several vendors also have 2-part push rivets where the first part slides into the drilled hole and the second part expands the first part so it can’t come out. I’m on my phone so I don’t have an easy link.

I only use shear pins on joints that I want to separate in flight.

 

[tsmith1315]

As to the "rivets" to hold on to the lower body and altimeter bay together, what should these be?

2-piece plastic rivets. Like a drywall anchor, or automotive plastic trim anchors. Here's an example:

https://www.csrocketry.com/building-supplies/small-parts.html

Like @boatgeek suggested, you can use screws. These are machine screws, coupler was threaded, CA'd and re-threaded. Self-tapping screws also work:

 

[teepot]

The RRC3 has three pyro channels. All you have to do is connect the electric match to the drouge side for apogee deployment. There is an LCD screen attachment {sold separately } that you can use to set the parameters you want. Easy Peezy. Are you going to use a Chute Release to cutdown on drift?

 

[BM1993]

@teepot what do you mean by chute release? Drift I presume means when the chute deploys at apogee and causes the rocket to drift away for miles? .

How would you recommend dealing with the possibility of drogue chute not deploying, and there is only one chute under the nose cone? I devised this system: There are two ignitors in one BP charge well. One attached to the drogue deployment output on the RRC3, the other set to deploy as soon as possible after the drogue. If the drogue doesn't fire for whatever reason then I have the other for backup. Makes sense?

I could always have two charge wells, with two separate ignitors..one drogue one main.

Is there a special formula for determining the hole size and amount when it comes to vent holes? Apparently there is some math you can do. Heard you should use ALWAYS an odd number, 1 or 3 holes etc.

 

[David_Stack]

BM1993;

Member “mtnmanak” has put together an overview of high power rocketry that he linked in post #6 of this thread.

In his chapter on dual deploy he provides links to an online resource for calculating avionics bay vent hole sizes.

You’ll find the answer to your question (and likely others) there…

 

[BM1993]

My bad! The post was so tiny i thought it was an ad!

 

[Titan II]

Is there a special formula for determining the hole size and amount when it comes to vent holes? Apparently there is some math you can do. Heard you should use ALWAYS an odd number, 1 or 3 holes etc.

It is in the RRC3 manual.

 

[teepot]

@teepot what do you mean by chute release? Drift I presume means when the chute deploys at apogee and causes the rocket to drift away for miles? .

How would you recommend dealing with the possibility of drogue chute not deploying, and there is only one chute under the nose cone? I devised this system: There are two ignitors in one BP charge well. One attached to the drogue deployment output on the RRC3, the other set to deploy as soon as possible after the drogue. If the drogue doesn't fire for whatever reason then I have the other for backup. Makes sense?

I could always have two charge wells, with two separate ignitors..one drogue one main.

Is there a special formula for determining the hole size and amount when it comes to vent holes? Apparently there is some math you can do. Heard you should use ALWAYS an odd number, 1 or 3 holes etc.

A chute release is a device by Jolly Logic. It holds the chute so that it doesn't open until the rocket gets to the altitude you want on the way down. Yes, you can set two channels to fire one after the other.