Side Hatch Deployment for Drogue

[Richard Dierking]

I've been developing side deployment hatches to help get rockets down quickly for a couple years. I use small parachutes (9") and deploy from 2 hatches at the aft end. So, the rocket comes down nose first with the small parachutes trailing the rocket. The descent is a lot more "orderly" than traditional drogue deployment, or even just blowing the nose for drag. Descent velocity has ranged 150 to 200 fps and this helps to minimize drift. The bays are small; for depth, I only have the space between a 54mm motor tube and the 3" airframe, but using a small about of BP in a rubber tube works well to shear the 2-54 nylons that hold the hatch door closed. Now, I'm going to try using just the hatch door for drag. Last year I tested a mechanism. Here's a link to the video:
I haven't tried this yet in a rocket and look forward to your comments.

 

[cwbullet]

Interesting idea. Very novel.

 

[MikeyDSlagle]

I've worked on side opening bays off and on for a while now. I'll make progress and then go off working on something else then revisit and so on. I've been looking at servos, stepper motors and screw drive type mechanisms; panels that open outward, slide, or blow off. My prototype-printing-person has fell off the map again, but I may have a new guy willing to print for me.
Trying to learn Arduino to control everything.
You have made much more progress than I have. I like it and would like to see more of your mechanism.

 

[mbeels]

Very nice! Interesting idea, and well tested.

 

[Richard Dierking]

Cool to see that others are interested in this kind of thing.
First, I settled on a pull-pin latch after doing some testing. The pull-pin is a very positive type of latch and can withstand vibration. However, I know there are other types of latches, this is just what I decided to go with. One nice thing about the pull pin is that I could connect a manual pull release which makes adjustment and testing easier (i.e I could determine the pull force). I tried a bunch of different linear actuators, but given the very limited space (the annular space between the 54 mm tube and 3" airframe is only about 9 mm), I went with a micro gearbox motor purchased through Ebay. But, translating the rotational motion to linear was a bit of a challenge. I tested the torque of the micro motors btw and results were favorable. Keeping the bay door tight on the airframe requires a snug fit and linear actuators just didn't have the pull to overcome this.

I tried different types of latches and hinges. The current one that I'm going to test fly has a positive latch at the forward end of the bay. The release at the aft end with the spring brings the bay door back and releases the front, then a wire (I use music wire) lifts the forward end of the bay door to catch the air. The door will open at 0 air speed and presently, I know it will open and hinges will hold up to 100 fps.

A commercial altimeter like the Perfectflite CF or Raven delivers enough current for a long enough duration to pull the actuator pin. I'm working with Arduino for for a couple of other rocket projects, but don't want to go OT. A nice thing about using two side deployment bays with a bp charge is that they can be totally redundant. I use two altimeters usually, and deploy the first bay at apogee and the other a couple seconds later.

Keeping in mind that the goal of this project is getting down from high alt quickly and safely.

 

[MikeyDSlagle]

My plan was to pop a chute (or two) out the side so the rocket would fall flat and allow the main to fire into empty air so there is less chance it would tangle and what not. Was thinking sliding hatches so I could close them, partly just to be doing it. Maybe I'll get back on it when the Mega Magg finally flies...and my Lil Goblin, V2, and Viper IV...eventually.

 

[grouch]

Love it. I have always wanted run a drogue out of the aft centering ring with a main out of the nose. Might have to step up my thinking on this after seeing your great work.

 

[Richard Dierking]

The sliding hatch is a cool idea.
The mechanical release mechanism using the hatch door for drag is actually version D. I'm finishing version C currently (photo of white rocket). There are two deployment bays that use 0.4 g BP. Version B that was very similar tended to spin a lot during descent. I never figured out why. The new version has hatches further aft and the mounting location is at the forward end of the bay. I'll see if this helps. The smaller compartments at the far aft are for roll control, but that's something OT.
Version A (2 photos) had a single bay with the U-bolt for the shock cord located near the CG when the motor was spent. Deployment used a CD3 CO2 system. The idea was to have the rocket come down flat and this itself would slow the descent. However, the problem was that the drogue chute deployed from the bay had to be 24" or greater for the system to be kind-of stable. Otherwise, the descent was really chaotic and I was trying to improve the stability during descent. I abandoned that design.
There are lots of possibilities and I'm interested it what others come up with.