Build thread - 24mm supersonic rocket

[Starz]

Hi,
I have always wanted to make a rocket go supersonic. One day, I found some 24mm nosecones sitting around so I decided to attempt to go supersonic for the least amount of money possible. So I started playing around with 24mm diameter rockets on open rocket, and found it can go mach on 24mm reloads and mach 1.03 on an F44 single use motor. I ordered loc tubes instead of estes tubes because they are slightly thicker for only $2, and a coupler for $1. I then bought some 1/4 thick balsa sheets from Hobby Lobby for $5 although I only used a fourth of the sheet. I already have 10 feet of 2 inch mylar streamer and 150 pound strength kevlar line. Total spent on the rocket without the motor is $4.25. Planning on flying on D's and E's until LDRS, when I will shoot it on the F44, and if it doesn't reach mach, I will buy a casing and fly it on a G.

 

[neil_w]

1/4" is very thick for fins on a rocket that size, and will add considerable drag that will make it harder for you to reach desired speed. Then again, I tend to doubt that 1/8" balsa will survive transsonic. Try seeing the affect of changing fin thickness on your sims.

 

[bjphoenix]

See if you can find a single use F72.
Whatever you select for fin material, you should fiberglass them completely.
It will be hard enough to recover on D and E motors, you may only get one flight on an F. A 24mm motor at that speed won't leave visible tracking smoke. IIRC you should get over 3000' altitude. I'd like to hear from other people who have attempted this, in my experience the rocket doesn't launch, it just disappears without a trace.

 

[teepot]

I just finished 4 MD's. Two 29mm and two 38mm. One of the 29mm I built for a G80. It weighs 8.3 ounces with the cutes but not the electronics. It is dual deploy. At that weight Thrustcurve says 6200'. Both the 38mm rockets Thrustcurve again says supersonic with an I500 and 11000'. Both are dual deploy and will have an Eggtimer GPS/altimeter.

 

[Zeta]

....

 

[Starz]

....

I am doing airfoils and will paper the fins. If the thing disappears, it was only 5 bucks. Kind of like a supersonic swift.

 

[Starz]

Cut out the fins today.

 

[dr wogz]

Make a template of the fin profile, at the root & at the tip. this way, you have something to compare each side of the fin to, so you can be assured they are symmetrical, and all the same profile.

If you know what kind of airfoil you are after, you can calculate teh curve based on the NACA formula and entering into a spreadsheet to plot the curve

 

[Starz]

1/4" is very thick for fins on a rocket that size, and will add considerable drag that will make it harder for you to reach desired speed. Then again, I tend to doubt that 1/8" balsa will survive transsonic. Try seeing the affect of changing fin thickness on your sims.

Got 1/4 but sanded down a bit to about 1/32 and it will be papered.

 

[H. Craig Miller]

Mach-Buster by Rocket Vision was designed for that very purpose. 24mm MMT with 1/32” fiberglass fins.


Here is a review with flight statistics: Rocket Reviews -- Mach-Buster

 

[lakeroadster]

Hi,
I have always wanted to make a rocket go supersonic. One day, I found some 24mm nosecones sitting around so I decided to attempt to go supersonic for the least amount of money possible. So I started playing around with 24mm diameter rockets on open rocket, and found it can go mach on 24mm reloads and mach 1.03 on an F44 single use motor. I ordered loc tubes instead of estes tubes because they are slightly thicker for only $2, and a coupler for $1. I then bought some 1/4 thick balsa sheets from Hobby Lobby for $5 although I only used a fourth of the sheet. I already have 10 feet of 2 inch mylar streamer and 150 pound strength kevlar line. Total spent on the rocket without the motor is $4.25. Planning on flying on D's and E's until LDRS, when I will shoot it on the F44, and if it doesn't reach mach, I will buy a casing and fly it on a G.
View attachment 501636

Kudos to you for designing and building this from scratch. Pushing the limits, using wood based components... very cool.

Looking forward to the build and the launch report.

Name? Noah's Spear

 

[mbeels]

Got 1/4 but sanded down a bit to about 1/32 and it will be papered.

Fun project! Very nice, that is a lot of sanding. Papered balsa is surprisingly strong, and with an airfoil, they should be stout and fast.

 

[diyaerospace]

I attempted something similar to your project. A 24mm minimum diameter supersonic rocket. My main advice is to keep your stability margin above 2 as the mach transitions shift the center of pressure forward.
Cool project!

EDIT
After looking at your open rocket design I think you can increase your rocket's speed by shortening the rocket's nosecone to about an inch.

 

[Starz]

I attempted something similar to your project. A 24mm minimum diameter supersonic rocket. My main advice is to keep your stability margin above 2 as the mach transitions shift the center of pressure forward.
Cool project!

EDIT
After looking at your open rocket design I think you can increase your rocket's speed by shortening the rocket's nosecone to about an inch.

While doing research for this project, I believe I read your article on apogee's newsletter. Great job on that btw. Unfortunately, I already found the nosecone I am going to use lying around. Will you be attending LDRS?

 

[ep29030]

I would recommend covering the fins with tissue paper + yellow glue. Better yet: 0.5 oz/yd fiberglass + epoxy. I had a Quest Nike Smoke I modified for 29mm motors. Left out back spacer, installed 29mm MMT with upper, lower centering rings made from a few wraps of 1/2" typing paper and glue. I made the MMT long enough it just touched bottom of nosecone to help with flight stresses. Installed long streamer for visibility. Used to fly it on F20 long delay motors. Painted it fluorescent yellow with fluorescent red spiral stripe. Lost it several times at launches, but someone would always find it and bring it back. Broke one fin-reattached with superglue, then two layers of 0.5 oz/sq yd FG + epoxy fixed it. I got 8 flights out of it before nosecone separated at ejection and took its own flight path.

 

[beeblebrox]

Hi,
I have always wanted to make a rocket go supersonic. One day, I found some 24mm nosecones sitting around so I decided to attempt to go supersonic for the least amount of money possible. So I started playing around with 24mm diameter rockets on open rocket, and found it can go mach on 24mm reloads and mach 1.03 on an F44 single use motor. I ordered loc tubes instead of estes tubes because they are slightly thicker for only $2, and a coupler for $1. I then bought some 1/4 thick balsa sheets from Hobby Lobby for $5 although I only used a fourth of the sheet. I already have 10 feet of 2 inch mylar streamer and 150 pound strength kevlar line. Total spent on the rocket without the motor is $4.25. Planning on flying on D's and E's until LDRS, when I will shoot it on the F44, and if it doesn't reach mach, I will buy a casing and fly it on a G.
View attachment 501636

BIG NOTE: Your fin roots are way too short, you want a very long aspect ratio fin for strength. Trust me, I held the "Model Rocket" (Using that term loosely) Velocity record, documented for years. Mach 2.1, 2408 ft/sec. Flown with a G300 29mm (6 oz rocket) Nose was oak, it caught fire.). At that same launch several other mach busters were flown, including an AeroTech F101 24mm motor, and 18mm F52 and E45 motors. all busted Mach easily. The common thread though was root edge at least four times the chord for strength, use fiberglass or thin plywood (0.063" is perfect for your sized rocket.), balsa will not hold up. Fin flutter will rip then right off. Also for the nose, a straight cone is less drag than an ogive. Think Black Brant...

 

[James Kobel]

I attempted something similar to your project. A 24mm minimum diameter supersonic rocket. My main advice is to keep your stability margin above 2 as the mach transitions shift the center of pressure forward.
Cool project!

EDIT
After looking at your open rocket design I think you can increase your rocket's speed by shortening the rocket's nosecone to about an inch.

I'm curious about what you said about as you go across mach, it causing the center of pressure to move forward. Why is that?

 

[Starz]

BIG NOTE: Your fin roots are way too short, you want a very long aspect ratio fin for strength. Trust me, I held the "Model Rocket" (Using that term loosely) Velocity record, documented for years. Mach 2.1, 2408 ft/sec. Flown with a G300 29mm (6 oz rocket) Nose was oak, it caught fire.). At that same launch several other mach busters were flown, including an AeroTech F101 24mm motor, and 18mm F52 and E45 motors. all busted Mach easily. The common thread though was root edge at least four times the chord for strength, use fiberglass or thin plywood (0.063" is perfect for your sized rocket.), balsa will not hold up. Fin flutter will rip then right off. Also for the nose, a straight cone is less drag than an ogive. Think Black Brant...

Could you please send a picture? That would be very helpful for reference. Thanks!

 

[Starz]

I'm curious about what you said about as you go across mach, it causing the center of pressure to move forward. Why is that?

When a rocket goes supersonic, air builds up which can cause the center of pressure to shift forward causing the rocket to lose stability.

 

[James Kobel]

When a rocket goes supersonic, air builds up which can cause the center of pressure to shift forward causing the rocket to lose stability.

Okay. So is it a good rule of thumb for minimum diameter rockets to have a stability margin of at least 2?

 

[diyaerospace]

Okay. So is it a good rule of thumb for minimum diameter rockets to have a stability margin of at least 2?

Yes, rockets that go transonic and supersonic should have a stability margin of at least 2. I learned this the hard way as shown in the video below.

 

[bjphoenix]

I just finished 4 MD's...
... and will have an Eggtimer GPS/altimeter.

Tracker is a very good idea.

Mach 2.1, 2408 ft/sec. Flown with a G300 29mm (6 oz rocket) Nose was oak, it caught fire.).

I've seen the old WWII movies where the ships are firing 40mm Bofors at aircraft. You are pretty close to that- remove the metal projectile, make a plastic sabot that fits around your rocket, and "fire" it.

 

[Starz]

Sanded an airfoil into 3 out of 4 fins.

 

[diyaerospace]

Looks good!

 

[rokit]

I'm curious about what you said about as you go across mach, it causing the center of pressure to move forward. Why is that?

Some good info in this thread:
https://www.rocketryforum.com/threads/cp-shift-of-supersonic-rocket.163381/
Also, if you don't have it yet, download RASAero:
http://www.rasaero.com/

 

[jqavins]

So I started playing around with 24mm diameter rockets on open rocket, and found it can go mach on 24mm reloads and mach 1.03 on an F44 single use motor.

Keep in mind that 1.03 M is not supersonic. It's transonic. Supersonic is when the shock wave is "shed" from the airframe, and that generally happens around 1.2 to 1.25 M. Subsonic is when there are no shock waves at all, and transonic generally starts somewhere around 0.8 M. The exact speeds depend on the specific shape of the vehicle. The transonic region is really tough on a vehicle; the hardest thing about surviving supersonic flight is surviving transonic flight first.

Got 1/4 but sanded down a bit to about 1/32 and it will be papered.

Yikes! Is that a typo, or did you really sand away 7/8 of the balsa? At 1/32, even papered, I wouldn't want to put a C11 in this rocket.

View attachment 501789
Sanded an airfoil into 3 out of 4 fins.

I can't tell from the angle and lighting in this picture; are those profiled in the common rounded-front-sharp-back airfoil? (What I can tell is that they're thicker than 1/32; whew!) If so, that's a mistake. That shape is good for low drag in subsonic flight, but sharp edges on both ends will give less drag for transonic and supersonic flight. And drag is your ENEMY.

Best of luck. I hope it all goes well, and goes fast.

 

[Starz]

Keep in mind that 1.03 M is not supersonic. It's transonic. Supersonic is when the shock wave is "shed" from the airframe, and that generally happens around 1.2 to 1.25 M. Subsonic is when there are no shock waves at all, and transonic generally starts somewhere around 0.8 M. The exact speeds depend on the specific shape of the vehicle. The transonic region is really tough on a vehicle; the hardest thing about surviving supersonic flight is surviving transonic flight first.

Yikes! Is that a typo, or did you really sand away 7/8 of the balsa? At 1/32, even papered, I wouldn't want to put a C11 in this rocket.

I can't tell from the angle and lighting in this picture; are those profiled in the common rounded-front-sharp-back airfoil? (What I can tell is that they're thicker than 1/32; whew!) If so, that's a mistake. That shape is good for low drag in subsonic flight, but sharp edges on both ends will give less drag for transonic and supersonic flight. And drag is your ENEMY.

Best of luck. I hope it all goes well, and goes fast.

Yes, that was a typo. I would never make my fins 1/32 inch thick. And my airfoil is the rounded front sharp back airfoil. I honestly would be glad to just have my rocket go transonic. Thanks for informing me about my typo.

 

[teepot]

When are you planning to fly your rocket?

Yes, that was a typo. I would never make my fins 1/32 inch thick. And my airfoil is the rounded front sharp back airfoil. I honestly would be glad to just have my rocket go transonic. Thanks for informing me about my typo.

 

[Starz]

When are you planning to fly your rocket?

At LDRS in the summer. I might fly it on some D's before that though.

 

[hball55]

Mach-Buster by Rocket Vision was designed for that very purpose. 24mm MMT with 1/32” fiberglass fins.

View attachment 501669
Here is a review with flight statistics: Rocket Reviews -- Mach-Buster

I have this rocket and have never flown it because I’m afraid of losing it; the Mach Buster is infamous for being lost on its first and only flight.