TFS Boosted Dart Project

The TFS boosted dart project has one and one very simple goal, fly over 100km. It begins with the development of a half scale 76mm boosted dart followed by a 152mm boosted dart. I have decided to post my build progress and findings here, and when I'm finished my finalized research paper on the project.

This project was inspired by the Loki, Super Loki and Viper Dart sounding rockets which repeatedly hit 55km-115km reliably. In fact the Super Loki dart hit 90-115km on a mere 38kn in a 98mm case. https://www.dtic.mil/dtic/tr/fulltext/u2/750796.pdf (just cause you probably don't believe me)

I'm of course hoping this project comes into fruition, but it is one thing to talk about and another to actually do. In any case, I plan on posting much of what I do here so others can learn and I can learn from others. After all, that is why I'm planning on doing this in the first place.

-Clay

76mm nozzle and aluminum expansion cone. Everything should be ready in the next few weeks to static test.

In any case, I plan on posting much of what I do here so others can learn and I can learn from others.

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I'm in the first category. Subscribed!

Watching with interest. Good luck mate!

Video of the 75/13,000 test. Didn't go quite as planned, but then again that's why I did a static test. The goal was to fit as much propellant into a 75mm as possible. Going to shorten the case a bit and run a higher port/throat and try again!
[video=youtube;mZDbUy1do_I]https://www.youtube.com/watch?v=mZDbUy1do_I[/video]

Also special thanks to aksrockets for taking amazing video.

Solarover12 said:

Going to shorten the case a bit and run a higher port/throat and try again!

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Can you provide any more information: a pressure curve, a description of the method of retaining the Al cone/nozzle, grain configuration and nozzle throat, or a picture of the case at the failure point?

Other than the massive spit (what was that?) this doesn't seem like an erosive driven failure.

Not sure how much I can post here. I'm planning on posting full details and burnsim file on the EX section soon. Sadly I don't have a test stand so I have no pressure/thrust data from the test.

Haven't updated in awhile. Here are some photos of the boosted dart. Still needs quite a bit of finishing work still. Open Rocket has it around Mach 3.3 and 104K. I don't believe that, I think it'll be closer to 80K, but about that same speed. Overall not bad for just 13kn...

I am very interested in seeing this project unfold!

Would you be willing to give more details on the dart itself and the interstage coupler? I would be very interested in knowing how you plan to recover, dart diameter/materials, coupler materials used, etc. Our university team at SDSU is working on a similar project and there are not a lot of similar projects to compare with.

Are you worried about the dart separating at the first motor chuff, or approximately 1/4-1/3 of the way through your motor's "usable" thrust? Based on the test motor video you posted your dart will surely separate at that point.

patelldp said:

Are you worried about the dart separating at the first motor chuff, or approximately 1/4-1/3 of the way through your motor's "usable" thrust? Based on the test motor video you posted your dart will surely separate at that point.

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Absolutely. The reason for the motor "chuffing" was for two reasons. (Just noticed that it is not he motor above, it was the one posted in the EX section, just realized I hadn't posted a link here)

1. The exit cone of the nozzle broke off. I changed the design in this motor that will hopefully fix this issue.

2. I was using homemade casting tubes in the last motor that were bonded to liner. What happened was as the first few grains burned out they easily spit my casting tubes and a good section of liner. (Since they were bonded to the liner they took the liner with them) I decided to go monolithic. I found the motor has nearly identical KN ranges as the previous motor and I have no risk of spitting casting tubes. I also felt the more progressive profile would help insure dart separation. I am taking a risk gong straight to flight, but I feel my margins are high enough that I should be fine. (This motor runs a max Pc of 700psi. Case yeild strength ~3,300psi)

raptor22 said:

I am very interested in seeing this project unfold!

Would you be willing to give more details on the dart itself and the interstage coupler? I would be very interested in knowing how you plan to recover, dart diameter/materials, coupler materials used, etc. Our university team at SDSU is working on a similar project and there are not a lot of similar projects to compare with.

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Yeah absolutely. I'm not home right now so I can't post more pictures, but feel free to ask questions.

Awesome, I appreciate it.

What diameter is the dart? Steel/aluminum? Dart weight? How are you sending tracking packets back with the mostly-metal body? Are you transferring thrust load to the dart through the walls of the interstage or do you have some internal structure in there supporting it?

raptor22 said:

Awesome, I appreciate it.

What diameter is the dart? Steel/aluminum? Dart weight? How are you sending tracking packets back with the mostly-metal body? Are you transferring thrust load to the dart through the walls of the interstage or do you have some internal structure in there supporting it?

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Dart diameter is the standard 29mm airframe. (1.225") Dart weighs just a tad under 5lbs. I have fiberglass sections for the electronics and recovery. I'm hoping that'll be enough of a "window" for the transmitters. Actually the dart is neither steel or aluminum. It's brass. Brass has a higher density than steel and is allowed by Tripoli. (copper would've been just slightly better, but more expensive and would not have looked as cool.) The thrust load is transferred through the walls of the interstage. Which in this case is just a fiberglass wound nosecone that's been cut down and had a coupler tube epoxied in.

Solarover12 in case you haven't seen this before, here are my boosted darts that I flew last year. They were powered with homemade sugar motors.

[video=youtube;9vcAQPJUqV0]https://www.youtube.com/watch?v=9vcAQPJUqV0[/video]

[video=youtube;AB_TpaJn72k]https://www.youtube.com/watch?v=AB_TpaJn72k[/video]

Andrej said:

Solarover12 in case you haven't seen this before, here are my boosted darts that I flew last year. They were powered with homemade sugar motors.

[video=youtube;9vcAQPJUqV0]https://www.youtube.com/watch?v=9vcAQPJUqV0[/video]

[video=youtube;AB_TpaJn72k]https://www.youtube.com/watch?v=AB_TpaJn72k[/video]

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Actually the 3" boosted dart you posted gave me the idea for this project.

Amazing projects. One thing I had always wondered was how did you do your transition cone for the dart?

Transition cone was turned on a lathe from a solid aluminum bar. It's made from two parts. The cone itself and a base which has a cavity where the dart boattail sits in. The two parts have about 0,1mm interference and are pressed together with a hydraulic press to make a single piece. Four spring roll pins are added, spaced 90° for added retention.

Solarover12 said:

Dart diameter is the standard 29mm airframe. (1.225") Dart weighs just a tad under 5lbs. I have fiberglass sections for the electronics and recovery. I'm hoping that'll be enough of a "window" for the transmitters. Actually the dart is neither steel or aluminum. It's brass. Brass has a higher density than steel and is allowed by Tripoli. (copper would've been just slightly better, but more expensive and would not have looked as cool.) The thrust load is transferred through the walls of the interstage. Which in this case is just a fiberglass wound nosecone that's been cut down and had a coupler tube epoxied in.

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Thanks for the details. Have you range tested the tracking equipment yet while installed in the dart? We were talking about doing something similar, but a buddy of mine convinced me that there would be too much shielding from the metal parts for it to be completely reliable without an external antenna. Right now we are planning on keeping the tracking equipment in a fiberglass canister that is tied to the shock chord.

The brass seems like a great idea. I didn't know it was Tripoli-acceptable. We were planning on launching steel from a private launch site, but it would really expand our options to be able to launch at Tripoli launches. What alloy did you end of going with?

Is the interstage nosecone just an off-the-shelf item?

Thanks again for sharing.

Tripoli rules state ductile metal, which is not a good property to set the rule.
So last year it was limited to aluminum alloys and copper alloys.
If you want to use a metal other than those you must petition the Tripoli BoD. I would suggest WELL in advance
https://www.tripoli.org/Portals/1/Documents/Safety Code/Metal in Rocket Construction v2.0.pdf

M

Great thread as I am working on a similar project. As brass is a copper alloy, it is an approved material. What wall thickness are you using?

Keep up the good work.

Thanks for the responses on the brass.

The other thing that was giving me pause was this quote from the pdf linked above:

"When made of ductile metal, the HP rocket must have a minimum amount of metallic parts
for the purpose of sustaining airframe integrity. Minimal may include whatsoever
percentage of ductile metal NECESSARY TO ACCOMPLISH THAT REQUIREMENT."

It seemed like some people could choose to interpret solid metal parts deliberately chosen for being dense and heavy to violate the spirit of "minimum metal parts", risking not being allowed at tripoli launches. Good to know.

There are also local restrictions, such as no metal airframes, cones, fins.... At Argonia.
At BALLS all metal rockets are common.
Wherever you plan to launch find out what they are cool with before you show up.

M

Andrej said:

Transition cone was turned on a lathe from a solid aluminum bar. It's made from two parts. The cone itself and a base which has a cavity where the dart boattail sits in. The two parts have about 0,1mm interference and are pressed together with a hydraulic press to make a single piece. Four spring roll pins are added, spaced 90° for added retention.

Click to expand...

Thanks for the information!

raptor22 said:

Thanks for the details. Have you range tested the tracking equipment yet while installed in the dart? We were talking about doing something similar, but a buddy of mine convinced me that there would be too much shielding from the metal parts for it to be completely reliable without an external antenna. Right now we are planning on keeping the tracking equipment in a fiberglass canister that is tied to the shock chord.

The brass seems like a great idea. I didn't know it was Tripoli-acceptable. We were planning on launching steel from a private launch site, but it would really expand our options to be able to launch at Tripoli launches. What alloy did you end of going with?

Is the interstage nosecone just an off-the-shelf item?

Thanks again for sharing.

Click to expand...

I have not tested it with the transmitter. I figured it would likely be fine since i've had friends mount trackers on the forward closure of a motor and had no problem getting signal. Still not a bad idea to pop out tracker at apogee either. It's just a standard 1.25" brass rod. Transition is just a standard filament wound fiberglass ogive nosecone. I'm only expecting about 35-40G's max for this flight, it should hold together just fine.

Titan II said:

Great thread as I am working on a similar project. As brass is a copper alloy, it is an approved material. What wall thickness are you using?

Keep up the good work.

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It's a solid 1.25" brass rod. The nosecone and tailcone are also solid brass.

MClark said:

There are also local restrictions, such as no metal airframes, cones, fins.... At Argonia.
At BALLS all metal rockets are common.
Wherever you plan to launch find out what they are cool with before you show up.

M

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Thanks for the information. I didn't know Argonia had special restrictions. I'm planning on flying this at a private launch anyway so I'll be fine.

If you ever decide to fly at Argonia, the following information is correct. I am building a rocket for AIRFest and have confirmed the accuracy of the following information on their website:

Aluminum Rockets at Argonia
Rockets launched at Argonia may not be constructed of all aluminum or any other metals. Aluminum fin cans or nose cones will be permitted only if required to ensure structural integrity of the rocket during a high-performance launch. Absolutely no aluminum airframes or fins attached directly to motor cases will be permitted under any circumstances. Any metal structural components (i.e. nosecones, nosecone tips, fins, or fin cans) must be painted. NO EXCEPTIONS! Screws, rivets, nuts, washers, and other non-structural small components are exempt from this restriction. Please contact the KLOUDBusters prefect for further details.

https://www.kloudbusters.org/

Just needs some paint and the 76mm small scale is ready for a test flight!

It looks fantastic! When are you planning for the test flight?

I'm hoping the 11,12 of June, if the playa is dry by then. If not it may need to wait another month. :/

I wish I could fly sooner, but there just isn't that many places with a 100k waiver.