Genesis II scratch build

[Velocity Aerospace]

So I attempted my L1 cert flight back in January, but it didn't go that well. Here's a link to my flight report thread if you're interested: https://www.rocketryforum.com/threads/tis-but-a-scratch.177191/ . But I am back in the saddle with my next rocket, the little brother to Genesis, Genesis II. I'm taking the lessons I learned and rebuilding... with some modifications. this is a 3 inch diameter by 63 inch height fiberglass rocket with an easymini dual deploy altimeter. In addition to the altimeter, I am also adding a RunCam split 4 in the coupler. I still need to model a sled for the batteries, but based on what I've read on other threads, I'm thinking of doing a LiPo battery for the camera and a standard 9v for the altimeter. I'm not well versed with electronics, so I would love some input on whether this is a good idea or not. Also, if anyone can recommend good LiPo batteries that will work on this flight, I'd really appreciate it, as well as any other feedback on the design. It's one that I'm extremely proud of, especially with it being one of my first scratch built designs. (I've designed some smaller low power rockets that have gone fairly well)

 

[thzero]

As far as batteries for the altimters, what does the manufacturer recommend?

Otherwise looks like a nice rocket! My L2 bird ended up being very similiar - 3" fiberglass wrapped LOC tubbing, DD but using two Eggtimer Quantums for altimeters.

 

[Velocity Aerospace]

As far as batteries for the altimters, what does the manufacturer recommend?

Otherwise looks like a nice rocket! My L2 bird ended up being very similiar - 3" fiberglass wrapped LOC tubbing, DD but using two Eggtimer Quantums for altimeters.

looking at the user manual, they recommend using a LiPo for the computer. the only issue is most hobby LiPos have reversed polarity which can damage the computer. they also stated that a 9v can be used, and they recommend ground testing to make sure it can light the e-matches, which it did on my last build

 

[Velocity Aerospace]

So I'm just about ready to start ordering parts and assembling, but one issue I have is the nose cone. I want to use a 4:1 ogive nose cone from madcow, but they're out of stock, and don't know when they'll be back. In fact all thir 3" ogive nose cones are unavailable. They do have a von Karman nose cone for twice the price. I know its better suited for super sonic flight, but is there a severe downside for using it subsonic? Should I go with it? Or wait it out?

Edit: I've also had suggestions that I 3d print the nose cone. I have a printer, and a 3d model, but with this being an L1, I'm not sure it's a good idea.

 

[Hobie1dog]

which program do you use for CAD work? looks great

 

[bad_idea]

So I'm just about ready to start ordering parts and assembling, but one issue I have is the nose cone. I want to use a 4:1 ogive nose cone from madcow, but they're out of stock, and don't know when they'll be back. In fact all thir 3" ogive nose cones are unavailable. They do have a von Karman nose cone for twice the price. I know its better suited for super sonic flight, but is there a severe downside for using it subsonic?

Disclaimer: I'm not an aerodynamicist. I have however looked at a ton of drag curves in papers relating to nose cone aerodynamics. Unless you're hunting an altitude record in a minimum diameter rocket, nose cone shape matters relatively little to drag at subsonic speeds. Throw your design in a simulator and see what it says when you sub a VK cone for an ogive one. OpenRocket is fairly accurate for subsonic speeds, and I'm told RockSim is too. My guess is the difference in altitude and maximum velocity will be negligible and will end up dwarfed by factors like surface finish, drag increase if you do tip-to-tip, weight gained in building, etc.

Edit: I've also had suggestions that I 3d print the nose cone. I have a printer, and a 3d model, but with this being an L1, I'm not sure it's a good idea.

You could design and print a few cones and test them on smaller rockets to learn your way around what would work for larger ones, then build a larger cone with confidence.

One thing I'd be careful to test is that your nose cone retention can handle the shock load at deployment. I lost the nose cone (not-3D printed) on my first L1 attempt when thermoset inserts pulled out of a 3D-printed bulkhead that attached a tracker sled to the nose cone shell. I later fiberglassed both sides of a second set of the same parts and fibrglassed nuts onto the back sides of them, and it's flown a few times just fine (though I actually used fiberglassed plywood for my subsequent cert flights).

Kudos on scratch-building your cert rocket, BTW.

 

[Velocity Aerospace]

Thank you, I use onshape for all my designing. Somewhere in there, I believe you can run simulations for drag. However I'm pretty sure you have to get the professional version to do that, and I only have the hobby version.

 

[Velocity Aerospace]

Disclaimer: I'm not an aerodynamicist. I have however looked at a ton of drag curves in papers relating to nose cone aerodynamics. Unless you're hunting an altitude record in a minimum diameter rocket, nose cone shape matters relatively little to drag at subsonic speeds. Throw your design in a simulator and see what it says when you sub a VK cone for an ogive one. OpenRocket is fairly accurate for subsonic speeds, and I'm told RockSim is too. My guess is the difference in altitude and maximum velocity will be negligible and will end up dwarfed by factors like surface finish, drag increase if you do tip-to-tip, weight gained in building, etc.

You could design and print a few cones and test them on smaller rockets to learn your way around what would work for larger ones, then build a larger cone with confidence.

One thing I'd be careful to test is that your nose cone retention can handle the shock load at deployment. I lost the nose cone (not-3D printed) on my first L1 attempt when thermoset inserts pulled out of a 3D-printed bulkhead that attached a tracker sled to the nose cone shell. I later fiberglassed both sides of a second set of the same parts and fibrglassed nuts onto the back sides of them, and it's flown a few times just fine (though I actually used fiberglassed plywood for my subsequent cert flights).

Kudos on scratch-building your cert rocket, BTW.

Yeah. I've already thought about retaining issues. I'm going to attach the shock cord to a bulkhead inside. I want the nisecone to be removable (it won't come off for the parachute, just for maintenance) so I'm going to use threaded inserts similar to the ones used on the rail buttons just inverted

 

[mtnmanak]

So I'm just about ready to start ordering parts and assembling, but one issue I have is the nose cone. I want to use a 4:1 ogive nose cone from madcow, but they're out of stock, and don't know when they'll be back. In fact all thir 3" ogive nose cones are unavailable. They do have a von Karman nose cone for twice the price. I know its better suited for super sonic flight, but is there a severe downside for using it subsonic? Should I go with it? Or wait it out?

Edit: I've also had suggestions that I 3d print the nose cone. I have a printer, and a 3d model, but with this being an L1, I'm not sure it's a good idea.

Considering Madcow gets all their parts from Wildman, you could probably look at Wildman's site to see what is/is not available and get a more accurate picture of availability. You may as well just go to the source and get all your parts from Wildman instead of going through a middle-man. You can also ask Tim to slot your body tube for you if you send him the dimensions/location of the slots.

 

[Velocity Aerospace]

Considering Madcow gets all their parts from Wildman, you could probably look at Wildman's site to see what is/is not available and get a more accurate picture of availability. You may as well just go to the source and get all your parts from Wildman instead of going through a middle-man. You can also ask Tim to slot your body tube for you if you send him the dimensions/location of the slots.

Thank you for the tip. I just looked on their website. The dimensions of their 3" tubes and nosecones are the same as madcow, but it looks like they do still only have a von Karman nosecone rather than an ogive one.

It's not a big deal though, my biggest issue was price. On madcow, the ogive nosecone was $40 while the von Karman one was $80. Missile works splits the difference with $60. If it's my only short term option, I'll take the $20 price cut. Thanks

 

[mtnmanak]

You could email Tim at Wildman ([email protected]) or ask them here (@WILDMANRS) about availability. They are very responsive to questions.

 

[Velocity Aerospace]

So my camera (finally) came in, and I'm officially crawling off the starting line with the build. One question I had, is it ok to cut off the plug on the camera and just run a positive and neutral plug off it(making sure to solder it on the right nodes) or is there another, better way to do it? I have an extra plug that fits the lipo, so if I can just use it, and discard the yellow wire, which I think goes to the transmitter for fpv, that would be great

 

[Velocity Aerospace]

I have my airframe, nosecone, and coupler. Progress is slow because I'm also in the process of moving. (A terrible time to build a rocket, I know) I also 3d printed a guide to make it super easy to mark where I need to cut the airframe for the fins, as well as for the different sections. I'm planning on getting the remaining parts in late September, as I'm going to Colorado to visit family, and I can save on shipping from apogee. I'm super excited to finally be working on the actual rocket part of my rocket. Especially after about a year hiatus

 

[Velocity Aerospace]

Things are coming along great, and ill have pictures soon, but I'm working on the decals now, and I would during how I should align the letters. I'm putting GENESIS II on the side vertically, but should I do it like this?

G
E
N
E
S
I
S

I
I

Or like this?

G
E
N
E
S
I
S

II

 

[bad_idea]

The latter.

 

[loopy]

The latter.

agree

 

[Velocity Aerospace]

So I've been really busy as of late, but I still found time to work on the rocket. I finished the assembly and got everything painted. All I have left are the decals, and recovery system. I'm just waiting on my brother to finish the design for the mission patch that's going on it.

I mounted the fins to the motor mount tube to do through the wall fins with crude fillets. After the epoxy was cured, I slid the assembly into the airframe and spent more time on the fillets for the seam between the fins and airframe. Even with all that effort though, they didn't cone out as smooth as I would have liked (though they were significantly better than last time)
I drilled the vent holes for the altimeter and the hole for the horizon camera. When I was tapping the holes for the shear pins, I broke my tap! So I had a fun time extracting the broken part from the airframe
The bulk plate for the nosecone went pretty easily, although I was short a forged eye bolt, so I went to the local hardware store to pick it up. I almost wasn't able to get it at the time because just as I was checking out, they cut the power for the whole store.

Overall, I'm happy with this build. After I attach the parachutes, I'm ready to test

 

[Velocity Aerospace]

Weather permitting, I'll be launching this Saturday. I've been doing ground tests, but I have a few more to go. I've been staring at the weather app checking the chance of rain, but it's been floating around 24% chance at the launch site. But fingers crossed at L-3 days!
View attachment 20231209_142057_1_1.mp4

 

[thzero]

Good luck. Love the scratch build.

 

[Velocity Aerospace]

I weighed the dry mass of the rocket and updated my simulations. The projected altitude is ~1300 ft with a peak acceleration of 20 g's. I do have the easymini set up for dual deploy, but after last year, I think I'm going to add the powder to the motor for a redundant drogue deployment. The h550 that I'm using has a built in delay of 14 seconds, but the simulation puts the optimal delay at 8.6 seconds. I'm going to keep the 14 second delay just in case the electrical charge doesn't fire so I don't blow up the rocket instead of blowing the section off. But regardless of which one gets it, there will be a separation this year...

The weather is showing the chance of rain is down to 13% chance at the launch site. Fingers crossed it continues to drop

 

[Velocity Aerospace]

So I'm good to launch, but it's been pushed back to Sunday instead. I've finished my ground testing, and everything looks good. I tried to record using the onboard camera, but when I went to review the footage, the card wasn't in it... but I good some good external shots

 

[-Slick-Ice]

Wow looks good! Hope you get it this time!

 

[Velocity Aerospace]

So Sunday was the day. After prepping everything, I was able to launch Genesis II. It reached an altitude of 1,175 feet, just 200 feet shy of the simulated altitude. The drogue and main came out right on time for a slow touchdown right on top of the launch pad! I wish we had a distance from pad contest. I so would have won. But with all that said, I am now level 1 certified!

The only issues that came up was with the av bay. The camera shut off prematurely, before I even left the pad, so that video is no good. I think it was from overheating. I thought that the cold December weather would keep it cool without a heatsink, but I forgot, I live in Texas, the weather always does what is most inconvenient. The other issue was a bit more serious. The rail buttons lined up with one of the screws for the switch cover for the rocket, so once it was on the rail, there was no way to take the cover off or put it on. What we ended up doing was powering on the vehicle, putting the cover on while holding the rocket in roughly the launch position so we could slide the rail over the buttons, instead of the other way around. It worked, but it's been noted for future rockets. I'm going to see if there's a way to fix this so I can launch again without jumping through hoops.

At the end of the day though, I couldn't ask for much better results!

 

[Velocity Aerospace]

View attachment IMG_5713.mp4
View attachment IMG_5714.mp4
View attachment Movie001.mp4

 

[bad_idea]

Congrats! I had hoped to be there to see this but had to skip the launch at the last minute.

 

[Velocity Aerospace]

Congrats! I had hoped to be there to see this but had to skip the launch at the last minute.

Darn. but, with mebeing certified, I'm going to try to launch again soon

 

[aerostadt]

Congratulations on Cert 1 ! Nice project!

 

[kjhambrick]

VERY NICE rocket and flight @Velocity Aerospace !

I really enjoyed your failure analysis of Genisis and this build thread.

Extra credit for your comprehensive report: Tis But a Scratch!

Congratulations on your Level 1 Cert -- I admire your your preserverence !

-- kjh