Project Blackout L1 Cert Build

[R3verb]

Hey All!

So after a long time in the hobby as a kid and getting back into it numerous times over the last 10 years as an adult, I finally decided to make the leap into HPR and get my L1 cert. After going back and forth on what rocket to use for my L1 cert (see this thread) I decided to go with the Madcow Super DX3 4.0 Payloader (https://www.apogeerockets.com/Rocke...et-Kits/Super-DX3-4-0in-Payloader?cPath=1_82&). I'm calling this rocket "Blackout" for reasons that will become clear during the finishing process. I ordered the rocket on Monday and, because I'm in Colorado only about 120 miles from Apogee, I got it delivered on Tuesday!

I'm actually NOT planning on jumping into this one just yet. I have a few MPR rockets that I want to get through first and it's still cold here in Colorado so I'm going to wait to start the build until spring. I figured I'd start this thread to help flush out some of the design decission I still need to make so looking for some good feedback from the community. In the meantime, the rocket will sit in it's back, patiently waiting to get built.



Thanks for stopping by!

Casey Levinger

 

[R3verb]

Alright everyone, after putting this project off for (looks at the date of the original post) oh god has it really been that long??? Yeah. After a year and a half, I finally feel like I'm ready to build this thing! I'm honestly not mad that I waited this long. In the meantime, I've been building MPRs using HPR techniques and I finally feel like I have the skills required to do what I actually WANT to do on this rocket. So, let's talk build.

I'm not building this stock. I know everyone says make your L1 simple but like, really where's the fun in that? Here's the plan for this rocket:

-Fiberglass sleeve the airframe
-Tip to Tip fiberglass fins
-Avionics bay instead/in addition to the payload section for dual sep/dual deploy
-Dual redundant flight computers (Telemetrum and EggTimer Classic)
-3D printed Avionics bay
-Secret pain job

So yeah, I've got my work cut out for me. I got the fiberglass sleeve ordered this week and it should be here in a week or two and I'll start on glassing the airframe. Hope you all come along for the journey!

Casey Levinger

 

[loopy]

Sounds good! Quick question - have you simmed this out with all the weight you're adding? Are you planning on using this for your L2 as well as your L1?

 

[R3verb]

Hey Loopy, nope, have not yet simmed it but I'll for sure do it before the fiberglass gets here. I probably will not use it for my L2 but who knows. This is supposed to be my L1 cert but I honestly might use my super upgraded Estes Star Orbiter for that (https://www.rocketryforum.com/threa...-estes-9716-star-orbiter.181106/#post-2549716).

I'll sim it tonight and let you know what it looks like.

 

[thzero]

4.0" for an L1? Use a big I motor.

 

[Aeva]

4.0" for an L1? Use a big I motor.

second this-- especially since OP wants to glass it too (glassed a 4" EZI-65 for my L1 and the I175 was barely enough to get the needed TWR, luckily it went well anyway; even on a redline I215, it's about 9.1 TWR which still below "ideal" but above "launchable")

 

[conneryc]

The way you are planning to build it will definitely work for doing L2 as well. Since it will be much heavier than "stock", the included parachute will most likely be to small for a good decent rate. Be sure you check the finished weight to calculate the larger parachute you will need.

 

[loopy]

Hey Loopy, nope, have not yet simmed it but I'll for sure do it before the fiberglass gets here. I probably will not use it for my L2 but who knows. This is supposed to be my L1 cert but I honestly might use my super upgraded Estes Star Orbiter for that (https://www.rocketryforum.com/threa...-estes-9716-star-orbiter.181106/#post-2549716).

I'll sim it tonight and let you know what it looks like.

The three comments above are the reason I'm asking...lol...a 4" rocket fully glassed plus tip to tip glass reinforcement is going to be VERY heavy for L1 flights, and is much more suited to L2.

 

[Aeva]

The three comments above are the reason I'm asking...lol...a 4" rocket fully glassed plus tip to tip glass reinforcement is going to be VERY heavy for L1 flights, and is much more suited to L2.

They might be able to leave out the payload portion, but they would likely still need to balance the nosecone in a sim. That might be enough to bring it into a reasonable weight zone. It's really just tall 4" rockets... and the DX3 is within the concerning range of height.

On top of that, I've heard that you really only need glassing if you're planning flights for 300N or higher thrust motors (don't quote me on that, but do look up the actual range because enough people here are smart enough to test it). For anything below that, good fillets on the fins is really the biggest concern so that it accounts for fin flutter. That being said, the DX3 has such a large root chord on its fins that its not likely to get much fin flutter (I'd have to look up the math again, but I've flown similar fins and come to the same conclusion).

 

[R3verb]

Thanks for all the info everyone! With what you guys have said, I do think maybe this is a good idea for my L2. The question is, do you think my Star Orbiter build is strong enough to do my L1? Here's the build thread:

https://www.rocketryforum.com/threa...-estes-9716-star-orbiter.181106/#post-2549716

It seems like a beast but I am in that "I don't know what I don't know" stage. Any suggestions on what motor to use for that rocket? Then I could go big on this one :-D

 

[Aeva]

Thanks for all the info everyone! With what you guys have said, I do think maybe this is a good idea for my L2. The question is, do you think my Star Orbiter build is strong enough to do my L1? Here's the build thread:

https://www.rocketryforum.com/threa...-estes-9716-star-orbiter.181106/#post-2549716

It seems like a beast but I am in that "I don't know what I don't know" stage. Any suggestions on what motor to use for that rocket? Then I could go big on this one :-D

Definitely can handle it, recovery would be concern imo because that's gonna go HIGH. It's good you have DD on it, but make sure you have a checklist to remind you to enable it for your cert flight. Pick the smallest H motor that still gives you 10-15 TWR.

http://thrustcurve.org will give you the option to enter the physical properties of your star orbiter and make suggestions on what motors you can use. For your cert flight, I recommend a DMS type motor so there is less chance of it being assembled wrong.

 

[loopy]

Thanks for all the info everyone! With what you guys have said, I do think maybe this is a good idea for my L2. The question is, do you think my Star Orbiter build is strong enough to do my L1? Here's the build thread:

https://www.rocketryforum.com/threa...-estes-9716-star-orbiter.181106/#post-2549716

It seems like a beast but I am in that "I don't know what I don't know" stage. Any suggestions on what motor to use for that rocket? Then I could go big on this one :-D

A star orbiter would definitely work, but you might want to put a tracker in it. Even with a baby H, it's going to go very high very fast. The other option is to do the L1 on the rocket from this thread...but you'll likely need either a high thrusting full H, or an I motor to have decent altitude out of the flight. Personally, I like to keep my cert flights in visual range, so this might be a case where you build the rocket as you're intending, then once you have the full weight of everything you can run simulations to see what motors would be best. Honestly, it might work out to be a good one for motor deploy on the L1 flight, then do some dual deployment test flights with it on bigger I motors and what not before moving up to L2.

 

[conneryc]

Thanks for all the info everyone! With what you guys have said, I do think maybe this is a good idea for my L2. The question is, do you think my Star Orbiter build is strong enough to do my L1? Here's the build thread:

https://www.rocketryforum.com/threa...-estes-9716-star-orbiter.181106/#post-2549716

It seems like a beast but I am in that "I don't know what I don't know" stage. Any suggestions on what motor to use for that rocket? Then I could go big on this one :-D

Personally I'd stick with the DX3 for both L1 and L2. It is a very simple design and that's what you want for a certification flight. It has three fins that DON'T stick down lower than the end of the airframe....so when it hits the ground, the tube hits first and not a fin tip....that could more easily break and fail the certification.

Build it FOR L2 in mind, but if it gets too heavy for and H or I to get it off the pad safely for L1, remove the payload tube and just put the nose cone on the booster tube and fly it like that. For certification flights, the "safe" thing to do is keep it low with a slow decent. That way it stays in sight the whole time and it won't drift too far away and land safely.

 

[conneryc]

Ok, I downloaded the RockSim file from Apogee and the stock build shows the lowest altitude achieved with a "recommended" motor is 1,639' with an H123W. That's with a as-built weight of 2.75lbs. However, if it were built "heavy", say up to 5lbs, that max altitude would only go just under 800'. Which IMO is more preferable.

 

[Aeva]

Ok, I downloaded the RockSim file from Apogee and the stock build shows the lowest altitude achieved with a "recommended" motor is 1,639' with an H123W. That's with a as-built weight of 2.75lbs. However, if it were built "heavy", say up to 5lbs, that max altitude would only go just under 800'. Which IMO is more preferable.

what's the velocity after leaving the launch rail though? an H123 might be underpowered to lift 5lbs. 123N is ~28lbs. 28/5=5.3TWR. I would not recommend that motor if you build it "heavy". You can use an H with more thrust though. Short burn motors tend to reach a higher velocity, thus more drag, thus lower overall altitude when in atmosphere. It might be better to put something like an H219 or something (219N = 50lbs-f, 50/5=10TWR).

Build your rocket, and once you're 100% done, go to thrustcurve.org and enter the weight, diameter, etc. That's the safest way to pick a motor.

E: Also I'm not sure how a cert would work with a G motor, but you could get a G with more than 100N thrust and that qualifies as a HPR L1 motor. That would reduce the impulse, and altitude range you're dealing with. That would be worth considering if 1600' is too much. Sike-- can't use G motors for cert flights

 

[conneryc]

Yes, in that example the H123 would not be advisable at that weight (speed off of a 6' rail would only be 26mph), but was just used as an example of the difference in altitude using the same motor at different weights.

However, an H130W would take it to 880' with an acceptable speed of 40mph off a 6' rail. But all depends on conditions and actual weight and balance values to be able to accurately determine speed/altitude based on a given motor.

 

[jmasterj]

E: Also I'm not sure how a cert would work with a G motor, but you could get a G with more than 100N thrust and that qualifies as a HPR L1 motor. That would reduce the impulse, and altitude range you're dealing with. That would be worth considering if 1600' is too much.

You can't cert with a G. Has to be an H or I for level 1.

 

[Aeva]

You can't cert with a G. Has to be an H or I for level 1.

Good to know! That makes sense... I thought there might be some extra rules with G motors.

 

[R3verb]

Thanks for all the input everyone! I do have another motor-related question. When I bought the rocket, I also bought the Cesaroni 38mm reloadable starter set:

https://www.apogeerockets.com/Rocke...gs/Cesaroni_38mm_Reloadable_Motor_Starter_Set

From what I'm hearing, it's super hard to find Cesaroni motors right now. Any suggestions or should I just bite the bullet and buy an AeroTech motor casing?

Any way to use the Cesaroni motor casing with another brand grains?

Thanks all!

 

[jmasterj]

From what I'm hearing, it's super hard to find Cesaroni motors right now. Any suggestions or should I just bite the bullet and buy an AeroTech motor casing?

Check with any vendors that visit the field where you fly/are planning to fly.

AMW Pro-X has 38mm motors in stock. 2G/3G White Thunder will handle your needs depending on the built weight.

 

[jmasterj]

Any way to use the Cesaroni motor casing with another brand grains?

Not 38mm, no.

 

[loopy]

Good to know! That makes sense... I thought there might be some extra rules with G motors.

There are some G motors that are considered to be HPR motors and can only be flown at HPR launches (e.g. with a waiver and what not) by flyers with at least an L1 certification due to propellant weight or average impulse. That might be the cause of the confusion.

 

[loopy]

Thanks for all the input everyone! I do have another motor-related question. When I bought the rocket, I also bought the Cesaroni 38mm reloadable starter set:

https://www.apogeerockets.com/Rocke...gs/Cesaroni_38mm_Reloadable_Motor_Starter_Set

From what I'm hearing, it's super hard to find Cesaroni motors right now. Any suggestions or should I just bite the bullet and buy an AeroTech motor casing?

Any way to use the Cesaroni motor casing with another brand grains?

Thanks all!

As was mentioned directly above this one, check to see what you can get at your field, or where the flyers at your club launches get their motors from and see what's available. Generally speaking (especially right now), AT seems to be much easier to find, so probably not a bad idea to invest in some AT hardware, especially since the spacers make it much easier to fly a big array of motors without having to buy a ton of hardware like we had to "back in the day"...lol