Tis But a Scratch

[Velocity Aerospace]

So I attempted my L.1 HPR flight yesterday with my 5 foot rocket Genesis. It was a scratch built rocket designed by me. I flew on a I175-WS motor and reached 1200 feet. however, the flight ended in catastrophic failure when the chutes didn't deploy. overall, it was a very educational flight. Although it was a huge disappointment, my personal motto is "whatever happens, it'll be cool". It went up, and that's enough for my first high power flight. I've attached all my photos in my report if y'all want to check it out.

 

[sharkbait]

So I attempted my L.1 HPR flight yesterday with my 5 foot rocket Genesis. It was a scratch built rocket designed by me. I flew on a I175-WS motor and reached 1200 feet. however, the flight ended in catastrophic failure when the chutes didn't deploy. overall, it was a very educational flight. Although it was a huge disappointment, my personal motto is "whatever happens, it'll be cool". It went up, and that's enough for my first high power flight. I've attached all my photos in my report if y'all want to check it out.

What’s your airframe diameter and what are the length’s if you drogue and main compartments. Guessing charges were too light, never had dog barf cause any issues.

 

[Hobie1dog]

bummer thanks for the report and pictures.

 

[Velocity Aerospace]

What’s your airframe diameter and what are the length’s if you drogue and main compartments. Guessing charges were too light, never had dog barf cause any issues.

The airframe was 4" and the drogue chamber was 10" long while the maimn chamber was 18". That was my original thought, but when I pulled the drogue and main out today, they required much more effort to pull out. It very well could be that the dog barf did nothing to hinder the flight, but it was a last minute addition that I hadn't tested for

 

[Velocity Aerospace]

I tried uploading the launch video, but for some reason, I kept getting errors

 

[sharkbait]

The airframe was 4" and the drogue chamber was 10" long while the maimn chamber was 18". That was my original thought, but when I pulled the drogue and main out today, they required much more effort to pull out. It very well could be that the dog barf did nothing to hinder the flight, but it was a last minute addition that I hadn't tested for

Couple other questions

1. Were you using shear pins and if so how many

2. What was the airframe made of ie cardboard, blue tube, fiberglass ect ect

3. What was the temperature on launch day

4. Did you do a ground test

5. Was your charge well full of BP, if not did you pack the empty space with wadding or something

6. Looked like you had some tape over the top of the well did you have a couple layers and then wrapped around it for a tight seal

7. Looked like your e-match was bent over the top or did you drill a hole towards the bottom of the charge well to insett the e-match

 

[Velocity Aerospace]

Couple other questions

1. Were you using shear pins and if so how many

2. What was the airframe made of ie cardboard, blue tube, fiberglass ect ect

3. What was the temperature on launch day

4. Did you do a ground test

5. Was your charge well full of BP, if not did you pack the empty space with wadding or something

6. Looked like you had some tape over the top of the well did you have a couple layers and then wrapped around it for a tight seal

7. Looked like your e-match was bent over the top or did you drill a hole towards the bottom of the charge well to insett the e-match

1, yes. I had 2 for each charge

2, fiberglass

3, it was in the mid 50s

4, I ran numerous tests for each charge (without the dog barf)
5, no. I calculated the amount of BP I needed and filled the rest with recovery wadding and packed it in

6, no. It was just 1 layer of tape to hold the wadding and BP in

7, no. The hole in the bottom was for the mounting screw. I drilled a separate hole to put wires through and sealed it with hot glue. I had screw terminals to attach the ematches.

On the first drogue ground test. The rocket failed to separate. On the following 2 however, it did. The capsule I used to measure is the one that comes in aerotech motor packs. It's hard to get a precise measurement on them, so I think that I just went too light.

 

[StreuB1]

Wait, you used a nomex blanket, and then added dog barf? If so, stick with one or the other (actually, just use nomex. dog barf is the past).

Also, you want to contain the BP charge with far more than a single cover of tape. You want many layers (I use a minimum of 4 and up to 8 at times depending on the situation). If not, the BP will not be sufficiently compressed and held for enough time to get a gas impulse. Just a suggestion.

What did you use for BP compression material (wadding)? I use very tightly compressed paper towel and it does very very well for decades. Then 3 crosses of tape, an external wrap and fold over of tape, then a piece in the middle to keep the folded over tape in place. This creates a tape "cap" that cannot rip along a seam and it acts like a burst disc. This is what gives you the impulse you need to really blow the N/C off and get the laundry out. The gas pressure is only part of the equation. The shock of the gas pressure wave is what shears the pins and gets things moving, the expanding gas behind it helps carry things out.

Sorry about your misfortune. You will rebuild and re-fly and it will be better than the first time! It always is.


BTW you picked a fantastic L1 motor. Using Super White was a great choice.

 

[StreuB1]

On the first drogue ground test. The rocket failed to separate. On the following 2 however, it did. The capsule I used to measure is the one that comes in aerotech motor packs. It's hard to get a precise measurement on them, so I think that I just went too light.

This points to inadequate confinement of the BP charge.

I would also suggest buying a small gram scale and begin weighing your BP charges. They're really cheap and worth their weight in gold. I had repurposed one of my Hornady GS-1500 reloading scales for rocketry purposes. Its a great scale and stays in my BP/ignitor ammo box that goes with me to all launches.

Hornady no longer makes that scale but there are others just like it. Look around and pick one up. I use small Dixie bathroom cups and a large wooden tongue depressor for doing my powder measuring.

 

[Velocity Aerospace]

Wait, you used a nomex blanket, and then added dog barf? If so, stick with one or the other (actually, just use nomex. dog barf is the past).

Also, you want to contain the BP charge with far more than a single cover of tape. You want many layers (I use a minimum of 4 and up to 8 at times depending on the situation). If not, the BP will not be sufficiently compressed and held for enough time to get a gas impulse. Just a suggestion.

What did you use for BP compression material (wadding)? I use very tightly compressed paper towel and it does very very well for decades. Then 3 crosses of tape, an external wrap and fold over of tape, then a piece in the middle to keep the folded over tape in place. This creates a tape "cap" that cannot rip along a seam and it acts like a burst disc. This is what gives you the impulse you need to really blow the N/C off and get the laundry out. The gas pressure is only part of the equation. The shock of the gas pressure wave is what shears the pins and gets things moving, the expanding gas behind it helps carry things out.

Sorry about your misfortune. You will rebuild and re-fly and it will be better than the first time! It always is.


BTW you picked a fantastic L1 motor. Using Super White was a great choice.

I wasn't aware that the seal was so important. Thank you very much for the advice. I will begin implementing it. As for the dog barf, I didn't want to use it, but my groups president kept pushing for me to use it, and during one of my tests, I actually burnt my drogue. I made xhanges that should have been sufficient, but I got scared.

 

[Antares JS]

@StreuB1 has given you excellent advice on properly sealing your powder charge, but there is one place where I'm going to differ from him: Instead of a scale, get a powder scoop of some kind that measures out a small amount of powder at a time.

I find a scale and paper cups to be too unwieldy to use at a launch (especially if there's a breeze) and even if you measure it out ahead of time, it's a pain to get the powder back into whatever you are going to use to carry it to a launch. With a scoop, you just scoop however many spoonfuls you need from whatever storage (I use a prescription pill bottle) directly into your charge well. I just had a 1 gram scoop for many years, but with the variety of high power rockets I have now that all require different amounts of powder, I upgraded to this recently.

https://www.cabelas.com/shop/en/lee-powder-measure-kit

 

[conneryc]

First, failures always suck. Looks like you are on the right track to determine the cause and correct it.

However, there are several things that you said that are concerning.
1. You said this is your "first" HPR flight.
2. Going for your Level 1 cert on your first HPR flight....
3. Going for your Level 1 cert on your first HPR flight and you jumped straight to using electronics and dual-deploy...

IMHO....Maybe go back and take smaller steps. Build a couple of kits, fly them with motor ejection and get the hang of it. Do your Level 1 on one of those kits. Then start working your way up to dual-deploy.

 

[David Schwantz]

https://www.amazon.com/KitchenAid-U...4479176&sprefix=measure+s,aps,133&sr=8-8&th=1
https://www.amazon.com/Weigh-Gram-D...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==
https://www.midwayusa.com/product/1012948067?pid=755866
I like to use these.

 

[Antares JS]

First, failures always suck. Looks like you are on the right track to determine the cause and correct it.

However, there are several things that you said that are concerning.
1. You said this is your "first" HPR flight.
2. Going for your Level 1 cert on your first HPR flight....
3. Going for your Level 1 cert on your first HPR flight and you jumped straight to using electronics and dual-deploy...

Um... one's level 1 cert attempt is ALWAYS one's first HPR flight. Otherwise, how are you making HPR flights without a cert?

There's also nothing wrong with using electronics on a level 1 or 2 cert flight if you're comfortable with them.

 

[conneryc]

Um... one's level 1 cert attempt is ALWAYS one's first HPR flight. Otherwise, how are you making HPR flights without a cert?

There's also nothing wrong with using electronics on a level 1 or 2 cert flight if you're comfortable with them.

Brain fart! LOL you are absolutely correct! I guess I fired off a few G's testing my Level 1 rocket before I went for my cert flight on an H and thought that was normal.

 

[Antares JS]

Brain fart! LOL you are absolutely correct! I guess I fired off a few G's testing my Level 1 rocket before I went for my cert flight on an H and thought that was normal.

If it's not normal it really should be.

 

[StreuB1]

@StreuB1 has given you excellent advice on properly sealing your powder charge, but there is one place where I'm going to differ from him: Instead of a scale, get a powder scoop of some kind that measures out a small amount of powder at a time.

I find a scale and paper cups to be too unwieldy to use at a launch (especially if there's a breeze) and even if you measure it out ahead of time, it's a pain to get the powder back into whatever you are going to use to carry it to a launch. With a scoop, you just scoop however many spoonfuls you need from whatever storage (I use a prescription pill bottle) directly into your charge well. I just had a 1 gram scoop for many years, but with the variety of high power rockets I have now that all require different amounts of powder, I upgraded to this recently.

https://www.cabelas.com/shop/en/lee-powder-measure-kit

Ahh yes yes, I should have clarified as I always prepare charges (and rockets) in advance for launches. Not always but usually. Yes, using a scale at the launch is a pain and for that I have made a 1g scooper for my 3F and 4F BP. That way I can do 1g and 0.5g 'eyeball' throws with just a scooper if I need to make charges at the launch. I generally try not to though because yes, its indeed a pain.

 

[Handeman]

I wasn't aware that the seal was so important. ------ As for the dog barf, I didn't want to use it, but my groups president kept pushing for me to use it, and during one of my tests, I actually burnt my drogue. I made xhanges that should have been sufficient, but I got scared.

The seal isn't that important, unless you are already marginal with the amount of BP you are using. You can just pour the BP into a piece of duct tape with an ematch which has almost no sealing, and it will work just fine if you have sufficient amounts of BP. The sealing of the charge makes little difference compared to changing the amount BP.

You didn't indicate how much you increased the BP after the failed drogue test. If you use the same amount each time, you were only 66% successful, and only 50% success if the flight is included which should have been a huge red flag. The problem is the amount of BP for the drogue charge, not how it is packed or sealed or that you used dog barf. If you use some dog barf as filler and one piece of tape, or a dozen pieces of tape, the difference will be slight, especially if the ematch is laid on the top of the BP instead of buried near the bottom. I've only used 2 pieces of tape over the well for years and put the ematch on the top of the BP so the flame front burns down and burns all the powder instead of at the bottom where it throws unburnt powder out. Sealing well can help there, but the effects are minimal. The secret is to be consistent, fly it the same way you ground test it.

Consistency is also what you want when measuring your BP. It doesn't matter if you use a scale to weight it to 0.1 gram or a 2cc vial to measure volume to get about the same volume. Just use the same method when you ground test to determine how much you actually need, and then use that same method when you fly. I always use the vials to measure with for ground testing and flights. Also, about 0.25 cc in the vial is about as fine as you need to measure to, except for very small rockets. With 2.6" and larger, 1/4 cc/gram is fine enough granularity. 1/2 cc/gram is good for 4" and above. With the effects of environmental variables and tolerances, trying to get a finer measurement than that, I believe is just a waste of time with no added value.

This is a hobby or in some cases, a class project, don't get lost in the weeds with specialized details trying to get things to tolerances that don't matter. It's like building a house and worrying about getting your 2x4s cut to within 1/64" when 1/16" to 1/8" is sufficient. When you have to build man-rated rockets, things will change.