Making a Rocket Capable of L1 and L2 Cert

[ConTron44]

Hey yall,

First time posting here, looking to get into rocketry more. Some background, I just graduated from college. I was in my SEDS chapter while I was there and got to design, build, (or oversee) and launch six high power rockets. The rockets ranged from minimum diameter mach busters to 13 foot tall fiberglass monsters we chucked to 10,000 feet. It was a good time and I miss it, so I am going to build my own rockets. No kits probably.

The first one I am attempting to design and build is going to be a Level 1/Level 2 'trainer'. I understand that high power rockets are no joke, so it may be a bit misleading to call it a trainer. But this rocket is meant to minimize flight risk and just get me my certifications before I move into different airframe shapes or custom avionics control. Here is a snip of the rocket design (in its level 1 configuration) from my current OpenRocket. I'll attach the .ork file to this post as well. I'm big on function over form, so everything here should have



The airframe will be LOC cardboard. From past experience, I know that blue tube and fiberglass are both very tough materials from prior rockets, but I don't think I'll need that toughness for this rocket. Cardboard is relatively light and really easy to modify. It's also super cheap, so if something like the upper tube dents, I can replace it. I'll need to be more careful about the lower tube. I am fairly confident in the axial compressive strength of cardboard, but I may purchase some tubes for compressive failure testing to know what I can do with the rocket.

I'll do dual deploy parachutes. Main in the upper airframe, drogue in the lower. Kevlar cord will connect everything together. U-bolts at the coupler, i-bolts for the nosecone and motor mount centering ring. Main will blow out the nosecone. The tubes as I have them are probably a bit long, but parachute packing has always been a huge pain, so I'd like to make it easy on myself for once. As I understand, I need dual deploy for certification as well.

Bulkheads, centering rings, and fins will be birch plywood. It's been good to me and my teams in the past and it's easy to work with. Four fins with simple geometry offer >2 caliber stability at rail exit which has worked well for us in the past.

I'll use the I117FJ motor reload for the L1 attempt and the J90W for the L2 attempt (if things work out). I plan to use the plugged versions or remove the black powder charge and use Stratologgers for chute ejection only. I'll have 2 of them on separate batteries for redundancy.

I plan to 3D print a nosecone and small transition at the bottom of the rocket. I made a 3D printed nosecone for a 6" diameter rocket that we launched this past year, and it was really nice for getting a modular structure with the desired shape. A 1/2 power series apparently has some of the lowest drag subsonic, so I've been using that. The 6" diameter one held up to some pretty rugged testing, so I'll trust PLA for now.

I'd like to make my own custom avionics package that pretty much just collects data and transmits it. I'd like to work up to making my own controller that can handle pyros or more complex controls in the future. I won't be doing that for any L1 or L2 attempts. I'll try to get a commercial tracker, but I'd like to add my own instead. I'll need to get my radio license before using any of those things as well.

That's about all I wanted to cover in this first post. I'll try to add to this as I make progress, but I am sure this is going to take a while. Currently settling into a new job among a bunch of other things that come with being done with school. Let me know your thoughts/recommendations! All of this is still just design work, no solid decisions until I start buying things.

Cheers

 

[PatD]

Welcome! Sounds like you definitely have a plan. Just a note from an old fart, relax and enjoy the journey. There is a ton of stuff on the site that may help inform your design decisions.

 

[Steve Shannon]

I agree; you have a well made plan to knock off your L1 and L2 certifications, and your university experience is great, but I’d like to see you concentrate on L1 without already planning for L2. Personally, I’m in favor of flying the L1, and then flying several more flights in that impulse range just for fun, instead of trying to just get levels out of the way. Fly those fun flights with different thrust and impulse motors and in differing conditions to test your rocket skills and gain experience. Every flight teaches you something, and no amount of book learning can completely replace those lessons. You may even want to make some additional L1 capable rockets to build and test different skills. Then, after flying those flights, figure out what you want to do for your L2. A good many people who do it that way figure out at least a few things they’d like to do differently for L2.

 

[Antares JS]

I'll (...) use Stratologgers for chute ejection only. I'll have 2 of them on separate batteries for redundancy.

Just a note, Stratologgers are good, but they are annoying to get ahold of, with only limited stock appearing on the Perfectflite website every few weeks or so. Also, if you are going to fly redundant altimeters, it's better to use two different ones because if one has some kind of error, the other is a lot less likely to have the same error if it's a completely different make and model.

I also second what Steve Shannon said about focusing on Level 1 and not worrying about Level 2 for now.

 

[Theory]

Every flight teaches you something, and no amount of book learning can completely replace those lessons.

IMHO - one of the best (rocket) statements of 2020

this goes for reloading HP motors. 100% the reason my first Cert 2 attempt ended whit a forward closure failure.

and dont forget to have fun

 

[markjos]

Thanks for sharing your thorough plan and design. This sounds suspiciously familiar! Please do consider Steve’s advice - I have a feeling you’ve heard that somewhere before . I’ll be following this.

Enjoy hanging out at a launch without the pressure of the Flight Readiness Review deadline the next day. Have fun.

Mark

 

[boatgeek]

This looks like a great start! Your college experience will serve you well here.

A few things in random order:
* Your planned motors (I117 and J90) sound like they're a little bit low on thrust. You really want to get a good thump off the pad, especially if you have 2 calibers of stability. I haven't reviewed the thrust curves for these motors, but for a 2.5 kg rocket, I'd like to see 200-250N of initial thrust. Your cardboard tubes can take 8-10G.
* You don't need a Ham license for tracking--there are several options in the Ham-free 900 MHz band.
* For altimeters, it's hard to go wrong with a Stratologger if you can buy them. If you can't, I am partial to Eggtimer if you can/want to learn to solder and Missileworks or Jolly Logic if you can't/don't want to. All of those have options on the cheap to powerful scale. For a backup altimeter, it's hard to beat the price/capability/simplicity combo of the Eggtimer Quark or Missileworks RRC2+.
* It looks like you're planning a 54mm motor mount in a 3" tube. That makes it difficult but not impossible to fit in a U-bolt to attach recovery hardware. If you're headed down that route, you might find it easier to glue the harness to the motor mount instead of using a U-bolt.
* What's the end goal of this rocket? Once you have your certs, do you plan to fly it on L1 motors mostly or L2 motors? That has a lot to do with your rocketry budget and local field size/waivers. If you're planning on mostly flying L1 motors, you might consider a 38mm motor mount. There are still lots of options in that MMT size and you might find them cheaper than small 54mm motors. If you mostly want to fly L2 and maybe go above J impulse, then stick with 54mm.

 

[Glasspack]

Steve,

PERFECT Statement............ "Every flight teaches you something, and no amount of book learning can completely replace those lessons."


On that note ... Contron44, welcome to The Rocketry Forum. Some very wonderful people here with a wealth of knowledge !!

 

[Walter Longburn]

As I understand, I need dual deploy for certification as well.

It's not a requirement.

 

[ConTron44]

Hmmmm I guess I can take advice this ONE time. Some changes I'll make according to your suggestions so far:
- I'll just focus on L1 for now. Make this rocket something I can fly multiple times on multiple motors. I was just worried about cost mostly, but if I can keep the rocket alive and fly on multiple motors, I should get the same enjoyment and knawledge out of it. Should help in developing custom electronics too.
- I think the Eggtimers are actually a really good choice. Way lower cost and I like assembling electronics. I may try to do one Eggtimer Quark and another. I'll need to look more into their reliability (if properly assembled that is). I'm sure it's good.
- Glad to see your comment Mark, I'll do my best to update this thread properly.
- I'll look at some 900 MHz trackers
- I'll look for some higher thrust 38mm motors, I planned on doing an i-bolt near the motor mount due to the lack of space, but this will just make it easier. Also easier for manufacturing and epoxying fins in.

I'll make some updates as soon as I can. Probably order some parts soon as well. Thanks everyone.

 

[Handeman]

As was stated, dual deploy isn't required for L1 or L2. But, if you want to use that, by all means, go for it.

I learned more from my DD scratch build L1 rocket than any other. Not just building and getting the cert, but flying it on L1 motors afterwards. As Steve said, you learn a lot with every flight and I couldn't agree more.

I applied what I learned from my L1 rocket to my L2 cert rocket. I retired the L2 rocket after 50 flights. Today, I would never build a rocket like I built either of those two. But learning with every flight, that's the fun and the journey.

Welcome and good luck.

 

[OverTheTop]

Welcome ConTron44. Congratulations on completing uni and entering the workforce. I agree with what has been previously said, especially Steve's comments. I would also like to suggest you build two rockets. One for each level. You can improve your build techniques and/or try new materials and methods. At the end you have two rockets and more experience. Personally I would be going for dual-deployment for the L2, but the choice is yours alone as to what you fly (within the rules anyway). Once you start using altimeters instead of motor ejection you will love it.

Importantly, have fun .

 

[rewilfert]

I built a fiberglass Super DX3 for my L1 and L2 flights. I planned for and did them back to back. I used motor ejection and a JLCR to get dual deployment. By design, the flights had very similar performance. The highlights of each flight are in my signature block.

 

[StreuB1]

I agree with Steve 1000%. Though, I can understand that these days where people often require immediate gratification and that an L1 is "not enough" or they want to get to the "big stuff" as fast as possible.

I can tell you that there are I motors out there that will challenge any flyer just as much as a J or K. For that matter, there are even H's that can pose challenging.

Building a rocket for L1/L2 is not a bad idea, it saves some money and there are some that fit the bill; one being the Minie Magg.

I would though focus on your L1, fly some other motors even the same day. Wait a little time between the two and fly some of the challenging L1 motors. Go fly an I1299 and report back! ;-)

 

[Bat-mite]

To me, dual deploy is one of the more fun aspects of rocketry. Otherwise, it's drill the delay, stick in the motor, and hope for the best. DD gives you control over your rocket's deployment and descent rates, and it adds another layer of fun. I truly enjoy building AV bays, wiring up the altimeters and wells, calculating the BP, etc.

I guess it adds risk to your certification attempt if you do something incorrectly; but it greatly helps your chance of certification if you do it correctly.

 

[Handeman]

To me, dual deploy is one of the more fun aspects of rocketry. Otherwise, it's drill the delay, stick in the motor, and hope for the best. DD gives you control over your rocket's deployment and descent rates, and it adds another layer of fun. I truly enjoy building AV bays, wiring up the altimeters and wells, calculating the BP, etc.

I guess it adds risk to your certification attempt if you do something incorrectly; but it greatly helps your chance of certification if you do it correctly.

I completely agree with you. I seldom fly anything without DD any longer. I know my L1 cert would have been much harder to recover if it hadn't been a DD flight and my L2 would almost certainly been lost if it wasn't for DD.

I've got 5 rocket in various stages of build right now and 4 of the 5 are all DD. The only one that isn't is an Estes StormCaster I want to fly on E and F motors.

 

[Bat-mite]

I've seen so many L1 attempts drift out of sight over the tree line because the altitude was higher than expected and the chute was too big. At least with DD you aren't deploying the main until closer to the ground.

 

[Ravenex]

I agree with much of what was said with one exception, to each their own. I wanted to get my L2 and didn't want to spend the money on two rockets. I had some experience in rocketry and a good mentor. I spent a long time on my design, including CAD of everything, and carefully built the rocket out of fiberglass. My first L1 attempt failed due to using smokeless powder, which was a mistake, but I built the rocket tough and it survived the ballistic recovery. Some will argue that failing my first attempt is exactly why you should take it slow, but had I built a rocket out of less expensive materials to get my L1 it wouldn't have survived and I may not have had the funds to start over, and I still would have learned the same lesson. So taking what I learned I planned my next attempts and flew a successful L1 flight before lunch, took the L2 test, and flew a successful L2 flight in the afternoon.

I'm not saying don't take your time to learn. Be careful, learn all you can here, think through your design choice carefully, and don't rush to fly something you aren't prepared for. There are mistakes you make in the field that you will learn first hand even after you should have learned them reading the forum. But whether you learn them building an L1 capable dual deploy or an L2 capable dual deploy doesn't make much difference.

 

[MClark]

We had a member do L1 and 2 on same rocket, same day.
Just a basic rocket, single deployment in large field.

https://www.ahpra.org/Next Stop Level Ism.jpg

Another was planning 1,2,3 with same rocket, (don’t start whining about having to to do L2 before starting L3, was ok at time)
He ended up doing L1 with one rocket and 2/3 another. Eventually the original rocket was finished and flown on an I and an M.
M

 

[tsmith1315]

I used a LOC Expediter for L1 on H238 and L2 on J275, both with motor ejection only. Not on the same day. The kit was built stock, slowly and carefully, lots of 30 min epoxy. After a few L1 flights, I did the L2 cert with no changes. No big deal, just be reasonable about the impulse range you're expecting from it. The J275 was upper bound for this rocket, and I only knew that after flying it on a few different thrust curves.

Since there's not a penalty for failing a cert flight, the biggest reason I see to keep a cert flight simple is just respect for the person signing off for you. They want to fly their rockets, too. A straight up and down flight plan is quick and easy to verify, and then you can turn around the same day and fly it with some additional features.

 

[Handeman]

My biggest issue with using one rocket to cert L1 and L2, isn't that it can't be done easily, its that when you are done, you still have one rocket, and that rocket is really only good for one cert range. Usually L1 with a baby J motor capability. If that is where you intend to stay, then fine, go for it.

If you intend to fly the range of L2 motors after your cert, you will need a rocket capable of handling the larger motors. You can say it's cheaper to do both certs on one rocket, but really, what's the point if you want to fly K & L motors. You will need to build a rocket capable of flying those motors anyway. Why not build it for the L2 cert after you have explored and learned the L1 range, and can apply that knowledge and experience to the L2 rocket. Most non-certified people don't have the experience or knowledge to build or modify a kit to make it a decent flyer on H through K motors, much less include L motors in there.

Having said all that, that comes from an east coast perspective where waivers are seldom over 10K and a high waiver is in the 15K-16K range and reasonable altitudes for the field is usually in the 5K - 7K range. It is possible to build a rocket light enough to fly on L1 motors and still use large K and L motors, but probably not on the east coast and probably not for an L1 cert.

 

[Dan Griffing]

Hey yall,

First time posting here, looking to get into rocketry more. Some background, I just graduated from college. I was in my SEDS chapter while I was there and got to design, build, (or oversee) and launch six high power rockets. The rockets ranged from minimum diameter mach busters to 13 foot tall fiberglass monsters we chucked to 10,000 feet. It was a good time and I miss it, so I am going to build my own rockets. No kits probably.

The first one I am attempting to design and build is going to be a Level 1/Level 2 'trainer'. I understand that high power rockets are no joke, so it may be a bit misleading to call it a trainer. But this rocket is meant to minimize flight risk and just get me my certifications before I move into different airframe shapes or custom avionics control. Here is a snip of the rocket design (in its level 1 configuration) from my current OpenRocket. I'll attach the .ork file to this post as well. I'm big on function over form, so everything here should have

View attachment 425247

The airframe will be LOC cardboard. From past experience, I know that blue tube and fiberglass are both very tough materials from prior rockets, but I don't think I'll need that toughness for this rocket. Cardboard is relatively light and really easy to modify. It's also super cheap, so if something like the upper tube dents, I can replace it. I'll need to be more careful about the lower tube. I am fairly confident in the axial compressive strength of cardboard, but I may purchase some tubes for compressive failure testing to know what I can do with the rocket.

I'll do dual deploy parachutes. Main in the upper airframe, drogue in the lower. Kevlar cord will connect everything together. U-bolts at the coupler, i-bolts for the nosecone and motor mount centering ring. Main will blow out the nosecone. The tubes as I have them are probably a bit long, but parachute packing has always been a huge pain, so I'd like to make it easy on myself for once. As I understand, I need dual deploy for certification as well.

Bulkheads, centering rings, and fins will be birch plywood. It's been good to me and my teams in the past and it's easy to work with. Four fins with simple geometry offer >2 caliber stability at rail exit which has worked well for us in the past.

I'll use the I117FJ motor reload for the L1 attempt and the J90W for the L2 attempt (if things work out). I plan to use the plugged versions or remove the black powder charge and use Stratologgers for chute ejection only. I'll have 2 of them on separate batteries for redundancy.

I plan to 3D print a nosecone and small transition at the bottom of the rocket. I made a 3D printed nosecone for a 6" diameter rocket that we launched this past year, and it was really nice for getting a modular structure with the desired shape. A 1/2 power series apparently has some of the lowest drag subsonic, so I've been using that. The 6" diameter one held up to some pretty rugged testing, so I'll trust PLA for now.

I'd like to make my own custom avionics package that pretty much just collects data and transmits it. I'd like to work up to making my own controller that can handle pyros or more complex controls in the future. I won't be doing that for any L1 or L2 attempts. I'll try to get a commercial tracker, but I'd like to add my own instead. I'll need to get my radio license before using any of those things as well.

That's about all I wanted to cover in this first post. I'll try to add to this as I make progress, but I am sure this is going to take a while. Currently settling into a new job among a bunch of other things that come with being done with school. Let me know your thoughts/recommendations! All of this is still just design work, no solid decisions until I start buying things.

Cheers

I sympathize with your desire to knockoff both L1 and L2 with the same rocket to save costs, because that’s what I did — despite the best advice to the contrary — including from my friend Steve Shannon.

But as a reformed sinner, don’t overthink this too much. The challenges of L1 and L2 are quiet different. Optimizing for both is a fool’s errand and it’s far more easy and reliable to focus on each objective individually.

There are many really great L1 “cardboard” rocket kits and out there at a reasonable price but despite the fact that many of their allowable motors may include the L2 range, IMHO, they’re pretty marginal for repeatedly launching with L2 power motors that have four times the acceleration forces as L1 motors. One hard landing or premature chute opening and your cardboard rocket will be nothing but a memory. And things like this happen with a much greater probability with beginning HPR rocketeers. It happens to all of us, so treat each rocket as something expendable to give you the experience to get to the next level.

Personally, my choice of the $89 Apogee Zephyr wouldn’t change if I had to do it again. But of what you spend on rocketry, the cost of the kit is your least expense.

So my “don’t do as I did” advice is to focus on getting your L1 first. What you gain from the experience will make your priorities change on what you focus on for your L2. And if you’re truly smitten by the high power rocketry gods, you won’t be satisfied with getting your L2 with your L1 rocket.

Like the planning before military battles, everything will change after your first launch.

Welcome to high power rocketry and good luck!

 

[Michael Wilson]

As others have pointed out, maybe a little faster off the launch rail, cardboard can take it. (ive flown a LOC nuke pro maxx to mach 1.2 unfiberglassed).
It does seem to me you do have a good plan.
Good Luck!