Does anyone ground test their rockets?
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rocketgeek101
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Pick up your rocket by a fin. If it falls off - back the workbench.
Separate the nose cone/payload section from the airframe; give the shock cord a good, steady pull. If it separates - back to the workbench.
What else did you have in mind jahall4 ?
Separate the nose cone/payload section from the airframe; give the shock cord a good, steady pull. If it separates - back to the workbench.
What else did you have in mind jahall4 ?
On most mid power I don't even test that. Off the bench, into the paintbooth, off to the pads.
If I'm using an altimeter, I'll test deployment on the ground to make sure everything is sized right to separate and break shear pins. (and before anyone asks, I had two charges in cups in these tests...both were going off together. I ditched the cups and put each charge in it's own vial. bingo!)
[video=youtube_share;8JjxD48V_e4]https://youtu.be/8JjxD48V_e4?list=UU3builfBvFxj13D88qCUR5g[/video]
If I'm using an altimeter, I'll test deployment on the ground to make sure everything is sized right to separate and break shear pins. (and before anyone asks, I had two charges in cups in these tests...both were going off together. I ditched the cups and put each charge in it's own vial. bingo!)
[video=youtube_share;8JjxD48V_e4]https://youtu.be/8JjxD48V_e4?list=UU3builfBvFxj13D88qCUR5g[/video]
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rocketgeek101
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Yes.
jmattingly13
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For personal projects, I don't ground test, but I have done extensive ground testing for things like NASA USLI. When you're trying to win a NASA competition, it turns out that structural, aerodynamic, etc. testing are quite in favor.
blackjack2564
Crazy Jim's Gone Banana's
No.
I also test the nose cone fit & payload fit on my motor eject rockets.
Grab the nose cone with rocket in vertical position. Pick it up holding the NC only and shake a bit. The NC should be snug and barely begin to move.
If it comes right off, I put a wrap or so of tape on the shoulder to snug it up.
Same for payload to fin-can fit.
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CzTeacherMan
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okay... might as well ask...
I'm brand new to Dual Deploy. I have an Adept 22, and I'll need to ground test charges before I launch in DD mode. This is a couple months off for me, but I saw this thread and figured I'd start the learning now...
1) How does one ground test an altimeter?
2) How do I test whether the altimeter will properly fire the ejection charges?
3) I've seen people use vacuum pumps (and rigged vacuum pumps using sealed containers and syringes)... How does that all work?
I'm brand new to Dual Deploy. I have an Adept 22, and I'll need to ground test charges before I launch in DD mode. This is a couple months off for me, but I saw this thread and figured I'd start the learning now...
1) How does one ground test an altimeter?
2) How do I test whether the altimeter will properly fire the ejection charges?
3) I've seen people use vacuum pumps (and rigged vacuum pumps using sealed containers and syringes)... How does that all work?
codysmith
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From my basic understanding, the vacuum pump simulates altitude and when attached to a test bulb, shows whether the altimeter will fire at correct times.
To ground test the charges, they are put into the loaded rocket and set off with different things from launch controllers, to 9v batteries. Anything that will fire the charge.
If I am wrong please correct me... I have not done DD yet but that is what I understand...
RecoRocket
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The main testing I'll do is not the rocket, but the altimeter, and then only if something weird happened in the last flight or if I haven't used it in a while. Adept has this "pressure chamber" with a large syringe to suck out air so you can simulate a flight for Baro devices, and using a couple of radio shack lights, you can see that the charges fire when you think they should. As far as the size of the charges for a real flight, I did a few ground tests when I first started with electronics, but stopped when I knew what I needed in general, and the neighbor's dog was getting upset....
As far as the actual design and stability, things like RS and OR can tell you that before you've built anything
As far as the actual design and stability, things like RS and OR can tell you that before you've built anything
rocketgeek101
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You're spot on (at least in my opinion!). I did my first DD flight a little over a week ago and that's exactly how I went about it.
matthewdlaudato
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Testing that charges are properly sized to snap your shear pins - yes, you can do that with a switch, a battery, an ematch, and enough wire to keep yourself a safe distance away. Testing the altimeter itself - the only time I used the shop vac setup was when I was testing my telemetry rig, to make sure that data was being properly transmitted and processed at the ground station. I simulated around 200' of altitude in this way.
That said, I have used the Stratologger in test mode via its software client to test new igniters and/or batteries, to convince myself that the altimeter would fire properly.
That said, I have used the Stratologger in test mode via its software client to test new igniters and/or batteries, to convince myself that the altimeter would fire properly.
[video=youtube_share;qHfL20o2RaU]https://youtu.be/qHfL20o2RaU?list=UU3builfBvFxj13D88qCUR5g[/video]
[video=youtube_share;kQCWM0doCf4]https://youtu.be/kQCWM0doCf4?list=UU3builfBvFxj13D88qCUR5g[/video]
nute
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+1 on what's been said here-I did lots of testing with the altimeter in a vacuum, ematches in altimeter, ematches to battery, charges in rocket, etc. before my first dd flight, and it went off without a hitch, as did subsequent flights. If you test each part of the flight, and are comfortable with the rocket, altimeter, ebay etc, there should be no surprises at the field. So I can only agree with what others have said. To test the altimeter, i washed out a glass spaghetti jar, drilled a hole in the lid stuck a piece of aquarium tube through, sealed it, and viola, a pressure chamber. Just suck air out and release it back in to stimulate a flight for baro altimeters
Nate
Nate
RecoRocket
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1) look at the adept website, they have this little jig with a bottle and a big syringe. (you put the altimeter in the bottle, and pull out air with the syringe - simulating a reduction in air pressure - the way "up", as you push the syringe back in, pressure in the chamber increases, and simulating "down" (to fire the second charge, for example)
Some vendors also have a "test mode" for their devices. Something like an incandescent xmas tree light or a led/resister combo can be used to see when charges get fired.
2) see #1, and use your ematch instead of a light (no BP, only the ignitor) You can also just check with the vendor of your altimeter, as they know if your ematch will work. But make that if you're using something other than 4fg BP, you test with the charge packed abound the ematch in the was you intend (and stand a ways back) (there is a reason vendors send you a bit of BP and not smokeless!)
3) see #1.
IMHO, you should not be even thinking about DD until you have experience with single deploy and your altimeter. It's easy to add a small payload section to fly the altimeter in a bird you already have, and use motor eject as a backup.
I'll give you a hint here about electronics. Others have their own methods, but here is mine.
1) Go to Home Depot, and look for marking tape used for landscaping (bright colors). Plastic, about 1" wide, no glue! (The material is just like Estes streamers, and maybe 1-2$)
2) when you prep a flight with electronics, tear off enough of a tape so it can go around the bird and be tied. Do that! (even if your walk to the pad is short)
3) ONLY take off the tape when the rocket is on the pad and armed. Wait for the beeps/lights!
In this way, you can be back on the flight line, and not fly if you see the ribbon. Trust me, I've seen many bad flights simply because the electronics weren't armed. Get in a habit like this,as all it takes is the person at the next pad asks you a question, and you forget to arm!
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matthewdlaudato
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Pretty sure that simulating the stresses of flight is beyond my budget. Nothing quite like a test flight..
jahall4
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Sounds reasonable, anyone else do this?
blackbrandt
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Yup. I also do a "smart check", namely, I check the rocket for flight worthiness.
On my bigger rockets, I will smack the fins a few times, try and bend them, make sure they aren't coming off.
On my bigger rockets, I will smack the fins a few times, try and bend them, make sure they aren't coming off.
I do it during building. Didn't think to include it as ground testing but it certainly is. Making sure friction is right is important.
RecoRocket
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As a L2, the stress should be something you understand on your own without a stress test, and as a L2, it's quite foolish to not know and use a test flight with an L2 motor. I hope you were joking.
Yes, I'm a hard-azz when it comes to this actually being rocket science, and knowledge you should have at cert levels.. It's not a "badge". It's a journey!
jahall4
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I don't know that it is, that is what I'm asking about. If the structure (motor mounting, fins, etc..) can withstand being fixed for a ground test it seems reasonable it would survive in flight. The question is, could the static test itself tear the rocket apart when it would otherwise fly safely?
rocketgeek101
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Wait... Are you suggesting clamping the rocket to some sort of stand and lighting a motor in it?
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matthewdlaudato
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As a L2, the stress should be something you understand on your own without a stress test, and as a L2, it's quite foolish to not know and use a test flight with an L2 motor. I hope you were joking.
Yes, I'm a hard-azz when it comes to this actually being rocket science, and knowledge you should have at cert levels.. It's not a "badge". It's a journey!
There's a difference between understanding the stresses and simulating them. Once I believe I've built a sound rocket, I always consider that first flight a 'test', that's all I meant.
jahall4
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Sure, no one does this in a controlled environment? It would seem that this type of testing would become more and more critical as one endeavors to build ever lighter air-frames.
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No. There's no way to restrict a rocket, fire off a motor and simulate the stresses it would encounter in flight.
We do look at the forces of the motor, and evaluate the strength of components.... Typically, most people just build rockets much stronger than they need to be.
SpaceManMat
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You should probably try AreoFinSim the fins are the most likely to fail. Other than that I think you are looking at using a FEA application of some sort. BTW it looks like AreoFinSim is now free https://www.aerorocket.com/finsim.html
I test them with a flight. I ground test if they are over 20 lbs
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