3D Printed Exploding Bolt for H class side boosters

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TimothyAReed

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As the title states, I am developing exploding 3d printable bolts with the end goal of flying a high power rocket that utilizes actual drop away side boosters.
I plan to build an L-2 capable rocket, in order to receive my L-2 Cert. then fly the same rocket again with the boosters attached for a higher altitude flight. as of right now I have a functioning explosive bolt(4 test firings ), and now I need to test what its shear strength is. the following photos are from the development process to get everyone up to speed.

here is a link to a 120 fps shot of the bolt exploding https://www.youtube.com/watch?v=G8kdLrwFHI8

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BDB

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This is super-interesting. I'm watching intently.
 
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rharshberger

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I have considered similar methods only using nylon bolts drilled and charged. Eventually I would like to build a parallel staged Mercury Atlas.
 

markkoelsch

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I have considered similar methods only using nylon bolts drilled and charged. Eventually I would like to build a parallel staged Mercury Atlas.
Kevin Trojanowski did that some time ago with, if memory serves, a Delta. Worked great as I recall.
 

OverTheTop

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Great idea. At last the z-axis weakness of 3D printing can be used to an advantage!

One of the problems with using nylon is it is a bit stretchy and not brittle enough, so the bolt has potential to not break cleanly and completely. Some other polymers are better suited for that reason.
 

troj

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Mark is correct - we used exploding bolts on our Delta III (twice) as well as several other big projects. All using P motors as the central motor. We didn't use them for the boosters - those were done a little differently.

Our boosters were built where each booster had an aluminum "pin" that stuck out of the side of the booster, near the top. It went into a corresponding block inside the main airframe with a charge at the bottom of the well the "pin" went into. We then used a small nylon bolt through the top of the block and the pin to hold it in place. At separation time, we fired the small charge which sheared the pin and allowed the booster to drop away.

To give you an idea of the loads we were dealing with, each booster contained an L motor and the central motor on the rocket was a P.

-Kevin
 

TimothyAReed

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Great idea. At last the z-axis weakness of 3D printing can be used to an advantage!

One of the problems with using nylon is it is a bit stretchy and not brittle enough, so the bolt has potential to not break cleanly and completely. Some other polymers are better suited for that reason.
not using nylon, using PLA but will switch to ABS. Rharsh was using nylon bolts that can be bought at home depot
 

TimothyAReed

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Mark is correct - we used exploding bolts on our Delta III (twice) as well as several other big projects. All using P motors as the central motor. We didn't use them for the boosters - those were done a little differently.

Our boosters were built where each booster had an aluminum "pin" that stuck out of the side of the booster, near the top. It went into a corresponding block inside the main airframe with a charge at the bottom of the well the "pin" went into. We then used a small nylon bolt through the top of the block and the pin to hold it in place. At separation time, we fired the small charge which sheared the pin and allowed the booster to drop away.

To give you an idea of the loads we were dealing with, each booster contained an L motor and the central motor on the rocket was a P.

-Kevin
wow! that had to be an amazing sight! how high did it go?
 

troj

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wow! that had to be an amazing sight! how high did it go?
3,000ish feet if I remember correctly.

[video=youtube;1L30l-pYtpc]https://www.youtube.com/watch?v=1L30l-pYtpc[/video]

-Kevin
 

troj

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Is this the Delta project? Too bad the website and pics have disappeared...
Yeah, when I decided to get out of rocketry websites, that was a casualty.

The Delta III flight referenced in that first link was our first project; that flight was a failed attempt for a variety of reasons. One of the most critical of which is a key member of the team having suffered severe burns the night before the launch. We should have scrubbed that flight. Hindsight is a glorious thing.

We learned from that, rebuilt things and flew it again quite successfully. That's the LDRS video I linked in a previous reply.

Our second big project was the Redstone, commissioned by the X-Prize foundation. We've flown that twice - because of the weight of the rocket and the fins sticking below the airframe, it tends to suffer landing damage. We had to build a new lower due to fin damage on landing from the first flight.

[video=youtube;JpMjieGOgw0]https://www.youtube.com/watch?v=73BqYu1__5M]You can find video of the first flight here, including some pretty awesome onboard video complements of Art Upton[/url]

Our third big project was a Q-powered Pershing. A minor motor issue revealed a design flaw that caused premature deployment which led to the destruction of that airframe. I don't have video of that handy.

Our fourth big project was the Safety Rocket. It suffered a pretty epic motor CATO. When a P motor lets go, it really does some damage. [video=youtube;Lbk35Jpzdro]https://www.youtube.com/watch?v=Lbk35Jpzdro[/video]

Big projects are not only expensive, they're hard. Things that work well on smaller rockets, even a 50+ pound Level III rocket, don't scale and work on a larger rocket. Logistics of how to get the rocket to the field, how to assemble it at the field, how to get it vertical. And those are the easy parts. Who's going to make the motors? How are you going to recover it? What event are you going to fly it at that has a field with enough room? We typically spend at least one day, if not two, doing prep work at your prep area. Then another 5+ hours out at the pad. We learned a tremendous amount about that when we tied the KLOUDBusters away pads in the knot prepping for the first Delta III flight -- there were some other project teams who weren't happy with us, and we respect that and understand why. We learned from it and worked hard to coordinate with other teams and launch organizers afterwards -- on our second Redstone flight, there were three large projects all prepping within a few hundred feet of each other. All three teams stayed in communication with one another and the launch organizers were heavily involved in the communication, as well. It led to a very positive experience for all involved.

BTW, one major lesson learned from all of this is to never start a big project unless you have a committed team that really gets along well with one another. You're going to spend a lot of time together and if any one individual creates friction it can destroy the entire team and project in a heartbeat. I'm happy to say we had a pretty awesome group and we're all still friends.

-Kevin
 
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