Road to Three-Stage

[Superza]

I’ve been eyeing a high-powered multi-stage for a while, and after much careful designing and research I’ve settled on this rough design. The goal is to initially make a single-stage rocket, then convert it into a two-stage, and then again into a three-stage. I’m prioritizing reliability and ease of building, not overall performance (i.e. speed/altitude). I’m posting this because I am nearing the end of my designing phase, have parts, and will soon be constructing this rocket. As such, I was hoping for some constructive criticism before I make any massive mistakes. I'll also add regular updates about its progress.

The whole rocket will be 4in diameter and made of fiberglass. I have L2, so the rocket as a whole is limited to a total installed impulse of 5120Ns, and it has been designed accordingly.

Upper Stage:

Upper Stage will be 80in tall and weigh up to 17lbs fully loaded. Drogue is a 24in Crossfire. Main will be a 60in Recon. AV Bay will be held together by two 1/4in threaded rods. I have two 15ft 1/4in Tubular Kevlar Cord from my L2 that I’m planning to reuse for shock cords. The fins are 3/16in G10 Fiberglass. Undoubtedly overkill and sacrifices a ton of performance. But again, reliability first. With good fillets, these things won’t be failing anytime soon.

For its first launch, I’m thinking of either an Aerotech L1000W or an Aerotech K1050W. If it can survive a Mach 0.8-0.95 flight, then I know it will survive any of the future staged flights.

For electronics, I’ll be using the following:

• EggTimer Proton for staging and secondary recovery. It will use two 2S LiPo Batteries, one for regular power and one for deployments/staging.
• Missileworks RRC2+ for primary recovery powered by a 9v battery.
• EggFinder GPS TX for GPS. It will be powered with the same 2S LiPo that powers the Proton’s regular power.
• The switches will be custom pull pin switches. The design is nearly identical to Lab Rat Rocketries, but just in case, I’ll also be adding:
• 10v 5600uF Capacitors that will run in parallel with the batteries/switches. If the switches for some reason temporarily disconnect, the capacitors will hopefully supply power for just long enough to prevent electronics from resetting.

Middle Stage:

After the first successful launch of the sustainer, I’ll build and add the next stage. I’m opting for dual deployment for the booster stages. The plan is an 18in parachute for the drogue that will hopefully deploy on its own out of the interstage. I also have a 50in LOC Precision parachute for main.

For motor selection, The booster will be an Aerotech K1103X. That is around 13Gs and alone can get the rocket 3000ft. For the sustainer, I’ll likely go for the J800T for the first two-stage flight, but maximum performance would be with the K250W.

The electronics will be:

• RRC2+ for primary recovery.
• EggTimer Quark for secondary.
• EggFinder GPS TX Mini.
• More pull pin switches and capacitors!

Lower Stage:
View attachment 619642

Once the lower stage is added, the whole rocket will be just below 12ft tall and weigh nearly 37lbs. The lowest stage is specifically designed for the K1800. Because the rocket is getting so big and my impulse budget is running low, I’m essentially limited to just this motor. Provided my research was done correctly, it will be no lower than 11Gs off the pad and can get the fully loaded rocket up to Mach 0.4 before the next motor ignition. Recovery and electronics will probably be the same as the middle stage, depending on how two-stage recovery goes.

If anyone has concerns or feedback about the design, let me know. I’m looking forward to this project!

 

[markg]

Personally I prefer at least a 20ft harness harness for 4" rockets. I'd leave out the capacitors, I've never heard of anyone doing that. To me you are adding additional complexity and which is another possible point of failure. I fly the Proton on a two stage rocket, I'd also suggest dropping the second battery, it's not necessary. Just use one 450-600mah 2S. Also, I wouldn't share a battery between Proton and Eggfinder, I prefer to keep those separate.

Go drogueless on the boosters to save some weight and complexity down there.

cheers - mark

 

[Superza]

Personally I prefer at least a 20ft harness harness for 4" rockets. I'd leave out the capacitors, I've never heard of anyone doing that. To me you are adding additional complexity and which is another possible point of failure. I fly the Proton on a two stage rocket, I'd also suggest dropping the second battery, it's not necessary. Just use one 450-600mah 2S. Also, I wouldn't share a battery between Proton and Eggfinder, I prefer to keep those separate.

Go drogueless on the boosters to save some weight and complexity down there.

cheers - mark

Thanks for the feedback. The capacitors idea was actually from the Tripoli High-powered Rocketry magazine, specifically the "Spectacle of Staging: Part 3." If you think that complicates things too much, I can definitely leave them out.

 

[FredT]

I think you have a solid plan, but I have some quibbles.

Deploying the drogue on the second stage is questionable. There's significant chance it will not deploy, and if it doesn't, it won't be pretty. The stage will be stable and fall ballistically until the main deploys. The best outcome is a zipper.

When I use redundant deployment, I want what I think is the most reliable unit as the backup and use about 30% more BP than for the primary. If the primary fails, the backup MUST fire. I have never used an RRC2+, but there is a case to be made that it is the more reliable because of it's the simplicity and recovery deployment is its sole function.

You only need one battery for the Proton, and as in the earlier response, something in the 450 to 600 mah will do the job. I think it's OK to share it with the EggFinder. The combination runs for hours.

I get nervous using avionics without an integral capacitor, any power glitch will cause it to default to its power-on state. For the Proton this is unarmed, so its function would be lost for the duration of the flight.

If you use the Proton do not rely on Deviation for staging; go with "This-high-by-when criteria for ignition safety. You may want to look at the Blue Raven for staging; it affords you the option of direct tilt measurement for ignition lockout. It costs more, doesn't need a capacitor, but can't share the battery with an EggFinder.

Thanks for reading my articles. Good luck with your project.

...Fred

 

[markg]

If you use the Proton do not rely on Deviation for staging; go with "This-high-by-when criteria for ignition safety. You may want to look at the Blue Raven for staging; it affords you the option of direct tilt measurement for ignition lockout. It costs more, doesn't need a capacitor, but can't share the battery with an EggFinder.

For my two stage flights I am switching from Proton to Blue Raven specifically for the tilt detection feature. I didn't recommend it as I don't have any experience with it, I'm looking forward to trying it out next year.

cheers - mark

 

[JimJarvis50]

I would agree with the use of a Blue Raven or EasyMega or something that specifically uses tilt as a criteria for staging. I know Fred can execute the this-high-by-when approach, and you should do that too, but for most mortals, this gets very complicated for three-stagers. Make use of tilt to shut things down.

I would also suggest trying to make the stack as stiff as possible. Get rid of switchbands and other unnecessary tube breaks, use motor cases as part of the interstage couplers and reinforce staging couplers that don't use motor tubes.

I'm not sure what "hopefully the drogue will deploy on its own" means, but it sounds a bit iffy.

Jim

 

[robopup]

I would agree with the use of a Blue Raven or EasyMega or something that specifically uses tilt as a criteria for staging. I know Fred can execute the this-high-by-when approach, and you should do that too, but for most mortals, this gets very complicated for three-stagers. Make use of tilt to shut things down.

To add to Jim's comment, I think it's best when the this-high-by-when is used in combination with tilt, because they don't necessarily protect against the same non-nominal scenarios.

For example, I saw a two stager last summer where the booster motor catoed and the second stage coasted out of the tower to ~100 ft. At 100 ft, and with almost no velocity, the second stage lit. The rocket cartwheeled because there hadn't been enough speed for the fins to provide stability. I doubt the second stage tilt was ever >5deg before its motor lit. The second stage motor logic had tilt inhibit but no altitude+velocity check.

Good luck with your project!

 

[bzzh8c]

I’ve been eyeing a high-powered multi-stage for a while, and after much careful designing and research I’ve settled on this rough design. The goal is to initially make a single-stage rocket, then convert it into a two-stage, and then again into a three-stage. I’m prioritizing reliability and ease of building, not overall performance (i.e. speed/altitude). I’m posting this because I am nearing the end of my designing phase, have parts, and will soon be constructing this rocket. As such, I was hoping for some constructive criticism before I make any massive mistakes. I'll also add regular updates about its progress.

The whole rocket will be 4in diameter and made of fiberglass. I have L2, so the rocket as a whole is limited to a total installed impulse of 5120Ns, and it has been designed accordingly.

Upper Stage:

Upper Stage will be 80in tall and weigh up to 17lbs fully loaded. Drogue is a 24in Crossfire. Main will be a 60in Recon. AV Bay will be held together by two 1/4in threaded rods. I have two 15ft 1/4in Tubular Kevlar Cord from my L2 that I’m planning to reuse for shock cords. The fins are 3/16in G10 Fiberglass. Undoubtedly overkill and sacrifices a ton of performance. But again, reliability first. With good fillets, these things won’t be failing anytime soon.

For its first launch, I’m thinking of either an Aerotech L1000W or an Aerotech K1050W. If it can survive a Mach 0.8-0.95 flight, then I know it will survive any of the future staged flights.

For electronics, I’ll be using the following:

• EggTimer Proton for staging and secondary recovery. It will use two 2S LiPo Batteries, one for regular power and one for deployments/staging.
• Missileworks RRC2+ for primary recovery powered by a 9v battery.
• EggFinder GPS TX for GPS. It will be powered with the same 2S LiPo that powers the Proton’s regular power.
• The switches will be custom pull pin switches. The design is nearly identical to Lab Rat Rocketries, but just in case, I’ll also be adding:
• 10v 5600uF Capacitors that will run in parallel with the batteries/switches. If the switches for some reason temporarily disconnect, the capacitors will hopefully supply power for just long enough to prevent electronics from resetting.

Middle Stage:

After the first successful launch of the sustainer, I’ll build and add the next stage. I’m opting for dual deployment for the booster stages. The plan is an 18in parachute for the drogue that will hopefully deploy on its own out of the interstage. I also have a 50in LOC Precision parachute for main.

For motor selection, The booster will be an Aerotech K1103X. That is around 13Gs and alone can get the rocket 3000ft. For the sustainer, I’ll likely go for the J800T for the first two-stage flight, but maximum performance would be with the K250W.

The electronics will be:

• RRC2+ for primary recovery.
• EggTimer Quark for secondary.
• EggFinder GPS TX Mini.
• More pull pin switches and capacitors!

Lower Stage:
View attachment 619642

Once the lower stage is added, the whole rocket will be just below 12ft tall and weigh nearly 37lbs. The lowest stage is specifically designed for the K1800. Because the rocket is getting so big and my impulse budget is running low, I’m essentially limited to just this motor. Provided my research was done correctly, it will be no lower than 11Gs off the pad and can get the fully loaded rocket up to Mach 0.4 before the next motor ignition. Recovery and electronics will probably be the same as the middle stage, depending on how two-stage recovery goes.

If anyone has concerns or feedback about the design, let me know. I’m looking forward to this project!

 

[bzzh8c]

My 3 stage HPR was a lot like this, just a step.down in power.
J570 to J350 to I161. I used an Adept ES 236 stager. 3rd stage ignition was a bit wonky but all 3 parts came back fine!
Here's the video from 20 years ago.

 

[Superza]

My 3 stage HPR was a lot like this, just a step.down in power.
J570 to J350 to I161. I used an Adept ES 236 stager. 3rd stage ignition was a bit wonky but all 3 parts came back fine!
Here's the video from 20 years ago.

That's really cool.

I've made a fair number of changes (unsurprisingly) over the past couple months as I've taken this forums advice, done more research, talked to launch field regulars, and slowly got it built. The sustainer is finally done and should be launching on a K1103X this coming weekend, providing weather permits.

 

[Superza]

Update:

Sustainer test launch was a complete success! It was a decently windy day with multiple rocket weathercocking, but because of both the K1103X's high G's off the pad and a moment of calm with the wind, the rocket flew near perfectly straight. The OpenRocket prediction was 5900ft with a max speed/acceleration of Mach 0.69 and 21G's. According to the Eggtimer Proton and RRC2+, the rocket actually reached 6160ft with a max speed/acceleration of Mach 0.66 and 23G's. The rocket landed about half a mile away and narrowly missed both a ditch and some power lines by just a couple dozen feet. Luckily, the fincan got stuck on a root and prevented the Recon 60in parachute from dragging the rocket any further. I used an Eggfinder TX and the LCD Receiver with the GPS module. The GPS worked perfectly, though I didn't actually end up needing it this time around.

So, what changes do I need to make for the next launch? Welp, the first thing to address is the drifting. I used a 24" Top Flight Standard parachute for drogue, which was too large. Average drogue descent rate was 50ft/s. I'm thinking I'll go for an 18" Top Flight Ultra-X for the next flight. Another minor issue was that my Drogue Terminal blocks/charges. I used floating charges made of vinyl tubing for the separation. When I recovered the rocket, I noticed the spent charges were missing and the terminal blocks were badly damaged. I don't want to litter the field and I want to be certain that both charges go off (I don't remember see both charges going off). I'll have to be more careful to protect the terminal blocks and keep the charges secure next time.

What about the next launch? It will be the two-stage. I am only just now preparing to purchase the parts for the booster. I may have heavy limitations on tools and workspace availability over the summer. As such, it probably won't be until fall when the booster gets finished and the rocket launches. On the upside, I now have more incentive to pre-order the motors, which will lead to significant savings! Speaking of which, I'm dead set on a K1800ST for the booster. The sustainer I am still on the fence about. I fly with a club that lets me borrow their hardware, but we actually do not seem to have any of the higher impulse 54mm hardware. Unless hardware magically appears, I'll probably just buy the 54/1706 casing and the K185W reload. Hopefully I can also get tracking video next time.

Hopefully everything continues to go according to plan. If anyone has more advice to offer, please let me know.

Also, huge thanks to Kurt Hesse, the Prefect of Tripoli East NC, who lent me his 54/1706 hardware after my club and I discovered significant damage with our own casing.

View attachment Timeline 1.mov