H Hybrid...

So, after a particularly insane phone call about hybrids with a friend, I began to design a DD HPR hybrid. I've been working away at it with OpenRocket, (admittedly my first real attempt at designing a makeable rocket) designing it around the H from Sky Ripper Systems. Now I have a few questions:

1.) How large should both chutes and their shock cords be?
2.) Any cheap DD altimeters you'd recommend?
3.) How viable is this rocket? Any changes you'd make?

and last but not least,

7,003.14159.) Would this be a good L1 cert rocket?

View attachment Hybrid.ork

You don't need the forward motor thrust ring (HPR motors use a ring at the nozzle end).

You don't need the bulkhead at the top of the motor. Your MMT doesn't *need* to be as long as you have it. (keep in mind you need to allow room for attaching the N2O vent tube).

Your effective av-bay is only 1.8" long (Not many DD altimeters will fit in that space). Move those bulkheads to the ends of the av-bay tube. Make the av-bay a single tube with the shorter outside tube a sleeve.

Adept 22 or Perfectflight Stratologger would be good starter recommendations, but search the forums.

I'd be concerned with balsa fins- especially hanging off the rear like these. They're just begging to be broken on a rough landing.

I modified the deployment options on the streamer and chute (apogee & 500') and also made the chute 36". This results in a 13ft/sec. landing. 15-21 is a good range.

I increased the streamer to 4x40", but that still results in a ~159ft/sec main deployment. You probably want to consider a small drogue to reduce these forces.


All that said, ~3500 feet is a nice range for a L1. The relatively slow acceleration of hybrids makes this easily tracked the entire distance.
Depending on your eyesight and spotters, a 42" rocket might get lost
without tracking smoke which hybrids lack. Choose you paint scheme and launch day conditions carefully.

HTH!

Here's the modified ORK file with a few of my changes.

Good luck!

View attachment TRF-Hybrid_v2.ork

brianc said:

You don't need the forward motor thrust ring (HPR motors use a ring at the nozzle end).

You don't need the bulkhead at the top of the motor. Your MMT doesn't *need* to be as long as you have it. (keep in mind you need to allow room for attaching the N2O vent tube).

Your effective av-bay is only 1.8" long (Not many DD altimeters will fit in that space). Move those bulkheads to the ends of the av-bay tube. Make the av-bay a single tube with the shorter outside tube a sleeve.

Adept 22 or Perfectflight Stratologger would be good starter recommendations, but search the forums.

I'd be concerned with balsa fins- especially hanging off the rear like these. They're just begging to be broken on a rough landing.

I modified the deployment options on the streamer and chute (apogee & 500') and also made the chute 36". This results in a 13ft/sec. landing. 15-21 is a good range.

I increased the streamer to 4x40", but that still results in a ~159ft/sec main deployment. You probably want to consider a small drogue to reduce these forces.


All that said, ~3500 feet is a nice range for a L1. The relatively slow acceleration of hybrids makes this easily tracked the entire distance.
Depending on your eyesight and spotters, a 42" rocket might get lost
without tracking smoke which hybrids lack. Choose you paint scheme and launch day conditions carefully.

HTH!

Click to expand...

Thank you! I'll take note of all that. I think I'll have a black-and-yellow test pattern for paint.
How long should the MMT be, and what do you recommend for the fins?

EDIT: Made the adjustments. Fins are still balsa, but that will change for sure. File attached.

View attachment Hybrid.ork

brianc said:

Here's the modified ORK file with a few of my changes.

Good luck!

Click to expand...

Whoops! Posted my last post before I noticed this.
Thanks! No further questions.
L1 time!

(forgot to upload final plans! Whoops!)

View attachment Hybrid.ork

View attachment Hybrid.pdf