supersonic boosted dart

[jraice]

My dad fell in love with the idea of a GPS tracker so while he gets all that ready we need a rocket to get it up there... i to fell in love with another idea, a boosted dart. Attached is a rocksim file for just the dart, I will be working on a file for the booster and then a combinded actual file.

The dart will consist of a 36" length of pml 38mm tubing, glassed with a layer of glass and possible a second smoother layer. It will have thin G10 fins with tip to tip glassing or CFing. Nose cone is a conical PML solid nose. Bottom half will contain a GPS transmitter and a PF mini alt... at apogee a long streamer or small parachute will be deployed. The aft of the booster has a conical nose cone with the tip cut off. It will attach to the booster transition using the technique on rocketryonline. Several rings in the booster transition will support it, and a 1/4" thread will go into the 1/4" hole in the back of the dart tailcone for the majority of the strength.

 

[jraice]

I will post more specific booster design info when I make/post the file but I will give some general info. First flight is planned at either BALLS, or the EX monday at XPRS. It will be a baby L... should get near 20K' and pretty decent mach numbers. First commercial flights will be a the TCC october skies. A few motors I am considering to try include the J2135W9, K1100T, K1275R and possibly the 54/852 warp 9 load... this all depends on performance info from the EX baby L flight... TCC commercial motor flights must stay under 16K'...

 

[Stymye]

your not even jr certified, how will this happen ?

 

[jraice]

My dad is L2 and he supervises the build of my (some prefer the term "our") rockets. This is something I have seen many times with teens my age, and a little older... He does all the "custom work" (cut's rings and all that good stuff) and he does the electronics. I/we do the actually assembly...

 

[dbarrym]

Originally posted by stymye
your not even jr certified, how will this happen ?

I gotta say, I have been critical (as have others) of JRaice and his communications 'style' here on TRF, but from what I've heard from some very experienced rocketeers who have seen his work in person, he's actually pretty talented...

good luck with this project! I am adding a GPS tracker and TX (ARTS) to my BALLs project, curious as to what GPS unit and TX you have found that will fit in a 38mm dart? I am having enough challenges fitting a flate plate GPS patch antenna in a 3" upper stage on my BALLs project..?

 

[jraice]

We plan on using a beeline GPS unit... it uses a small flexible antenna like a rocket hunter would use... it sends the signal to a HAM radio, which is connected to a device that translates a code into cordinates (some HAM radio's have it built it, we have to use a seperate box) then you just enter the cordinate into a handheld GPS and follow the little arrow It also functions as a directional tracker, if you attach a yagi to the ham radio.

I like how you use the word, or phrase, communication style. And thanks for the compliment...

I've heard from some very experienced rocketeers who have seen his work in person, he's actually pretty talented

So do you guys think we should go to balls or EX day on XPRS to fly this guy? Last year we went to XPRS and it might be fun to try BALLS... do they support rockets this small (baby L)? I hear there should be some HUGE projects this year! Couldnt get the rocksim file for the booster finished... I am going to have to do a CD override for the dart (and also for the booster...) and use a mass object to simulate the tailcone on the aft of the dart. Rocksim wont let the tailcone slide into the booster transition. We plan to do the flight at black rock (no chance of busting a waiver) and then using the flight data to make a more educated guess as to what the CD is. That way when we fly this at TCC with the 16,500' waiver I will be more confident that we stay well below it.

 

[jraice]

Here is a sketch of the design we plan on using to connect the dart to the booster. I got this from a "tech series" on rocketryonline that someone made of a similar type of rocket, 54mm with a 38mm dart. Only difference on ours... We are going to try to design it so we can use a PML urethane tail cone as the transition that sits on top of the booster. He uses plywood bulkheads. I am thinking just under the PML tailcone/transition we could have a support centering ring, then we would have one in the middle, just like in the sketch. Two support rings and the centering bolt should be very strong but still allow the dart to easily slide out. Another idea i have is to use the centering bolt and only the center plywood ring support. Because the dart's airframe fits into the transition we could make it so the actually BT of the dart slides 1/2" or maybe an inch into the tailcone/transition.

 

[Mark Clark]

Originally posted by jraice
BALLS... do they support rockets this small (baby L)?

At BALLS we have a lower power limit for commercial motors of K, motor must be 1280.1 NS or larger.
For EX, woops Research, motors there is no lower limit. Bring us an Ex 1/4A and I will be proud to launch it.


Mark

 

[smurf]

I think the beeline unit is just the data transfer for the gps data. I think what Barry was asking is what kind of GPS receiver are you planning to use that fits in a 38mm tube...typically the antennas for the actual GPS receiver is not a whip style but something more square (i.e. patch). It would be interesting if there were one small enough to fit a 38mm tube.

Interestingly I am building a boosted dart too. Slightly different approach to the dart/booster interface. Rather than thrust against the tail cone I decided to have a receiver/thrust tube and thrust against the body of the dart....the drawback is the small lip which might add a small amount of drag but I don't have to worry about the tailcone failing under high thrust. Also eliminated all but one centering ring since all it does is provide lateral support (less weight in the booster). Just removed the lip from a conical nosecone so i get a good fit in the receiver tube. Lapped the centering ring to fit the tailcone exactly and it works great. No play whatsoever and good release. Also gives the option for pyrotechnic separation should straight drag separation prove problematic. (54mm booster and 38mm high mass dart should provide enough drag delta to effect separation.)

Here's a little drawing of what I built.

 

[jraice]

Well i will talk it over with my dad, he is supervising the build but also he is very good with these sort of technical ideas. I was thinking use the tailcone bolt idea to keep the parts from being able to flex, but I think I might have some of the body tube (maybe just below the fins) slide in. I am sure with your sketch and the one I posted myself and my dad can come up with something... Could you post a rocksim file? I am trying to figure out how to keep my boosters weight and length down to a minimum, I am most interested in the placement of booster electronics and deployment stuff. The L1200 is about 28"s long so it needs to have atleast that much room, plus sufficient recovery room below the alt bay assembly. About how much weight would you estimate is added to a 54mm and/or a 38mm tube with a layer of two of glass sleeving. Right now I am telling rocksim the tubing is cf (a little heavier then just phenolic) because there is no glassed phenolic tubing in the list. Today I hope to finalize the rocksim file and move on to more specific design needs, and what will be required for this build.

 

[jraice]

The GPS reciever is not onboard the rocket... i will double check but I am pretty sure (from what I have seen in person at XPRS and read on the web) all that is needed on the rocket is the 2 ounce 38mm GPS beeline unit. HAM radio recieves the package...

 

[jraice]

I have decided to have GLR make all the parts for this rocket... that is all of them except the public missiles conical nose cones (for the dart nose and tailcone) and the transition for the booster. I have decided on using FWFG (will it block RF?). Ok, now for the experienced high performance flyers opinion... A few questions on fin strength for the booster and dart... I am going to have GLR make me some custom fins. I plan on doing a tip to tip with 10 ounce glass and then with 3 ounce (overkill?). Should I go with .063" (cant get them beveled) or .093" (beveled)? 10 ounce glass seems pretty beefy so I think the .063" should be fine, atleast for the dart (booster fins are obviously larger). If I do go with .093", how do I tip to tip glass and still preserve the bevel's? Preliminary rocksim file will be sent to teflon rocketry and posted asap, working on it as we speak. Oh, one more thing, does anybody know if GLR can dado slot the FWFG tubes for me?

 

[smurf]

You are right about the Beeline, it has an integrated patch antenna. I guess with the line of sight issue you just take the last GPS packet you received and that should put you within a hundred feet or so of the rocket. Cool, there goes another bundle of money on rockets!!

My booster came out at 58 inches in length although I freely admit it could have been shorter. This is more of a fun rocket so I didn't want to be packing parachutes with a broomstick and I wanted dual deploy on the booster too since with a K700 the booster should fly out to 8k +. Another consideration was the fact I wanted a multi-function booster....add a different receiver tube and fly two stage or put on a nosecone and fly minimum diameter. Also wanted the option of pyrotechnic separation if necessary (or just to play with that for future operations!) so there is some extra lenght built in. I used Hawk Mountain tubing and fabricated the transition from a 54mm conical fg nosecone (seemed like the lightest/strongest/easiest way). Ended up with two electronics bays (one amidships and one in the base of the receiver...could have knocked off a few inches there.) Even with the extra length the booster weighs in at 925 grams with a slimline retainer and .093 fins. Dart weighs in at 610 grams. Both weights are without recovery systems (parachute and TN), electronics or paint. Dart will have provision for weighting for max altitude.

Why are you wanting dado slots in the body tube for the fins?? Personally i don't find them necessary. I've surface mounted fins on minimum diameter rockets that you could use for a baseball bat and they are just fine. I think the dado's just weaken the fiberglass tubing. Make sure you use high temp epoxy, Cotronics 4525 is good (cures at room temp, Tg is around 500F, not too toxic and good strength). I think JB weld is pretty much the same stuff as far as the resin goes (same color, smell, consistancy, and similar physical properties) but uses a slightly different hardener (probably with fillers to make a convenient 1:1 mixing ratio.) Rather than having to deal with Cotronics, who would rather sell in large quantities (although their convenient 2oz "Epoxeez" kits are the same ones that used to be supplied with ShadowAero kits) I've been using JB with success. I then reinforce with three layers of Carbon Tissue (0.5oz carbon veil, available at acp-composites) and believe me, these fins won't come off. 10oz cloth is WAY overkill in my opinion unless you use a design that is prone to flutter....

Are you really going to pay $42 for someone to bevel your fins?? You can do it yourself for the price of a couple sheets of sandpaper and about 30 minutes of work....this is a hobby - craftsmanship is something to be proud of...

If really want to do the tip to tip glassing and preserve the bevels (that you sanded yourself right??), use a lighter cloth and then just sand any cloth off the bevels after the epoxy cures....the cloth doesn't really have to go out to the edge, it's more to stiffen and prevent fin flutter than anything else...if you really want stiff fins then use light carbon cloth if you can find it (lot higher stiffness to weight ration than fg).

 

[jraice]

I guess I will consider hand sanding. So you think .093" for the dart and booster? I would use CF but it is a LOT more expensive isnt it? I believe it may also cause problems on the dart... because the GPS transmitter will be near the fin section.... and CF can mess with RF. Dado slots make the fin attachment straighter and simpler. But ill think a bit more about that. I plan on using JB weld, probably JB quick (fast cure) to attach them and then regular JB weld to fillet. Do you have a rocksim file I could look at of your rocket? To see how everything inside is layed out... I will look at the acp composites for some light weight CF. There are some composite shops around here, can you give me an idea of what sort of thing to look for so I dont spend all my cash on someone that is to heavy, or just not strong enough...

 

[smurf]

I'll see what rocksim file I have that is close to the reality. I generally use rocksim to get the CP and don't worry too much about the details until I get the rocket finished.

Carbon cloth is hard to find these days but it can be had. Depending on how big your fins are you can probably use woven CF tape which comes in widths up to six inches or so and is fairly inexpensive (as those things go). The weave is not that important really. The harness satin weaves generally drape pretty well but plain weave is what i use most of the time since I fill and paint over the cloth. (The HS and other fancy weaves look prettier if you take the time to clearcoat etc.)

Most weaves have tows running in two directions, generally perpendicular to each other (that can vary though, especially with the braided sleeves). You want one of the tow directions to be along the axis you want to stiffen.

Lighter cloths are easier to work with, I like 5.5 oz and lighter since the heavier cloth is kind of stiff.

One thing though, make sure you cover yourself and wear at least a dust mask once you start cutting the carbon....if you think fiberglass is bad, carbon is ten times worse, especially once it has epoxy. You DON'T want to breathe the short stiff fibers that result when you cut or sand carbon composite.

 

[jraice]

Carbon tape... I have seen some of that on the web. So .093" fins for booster and dart? I was thinking my booster fins would be a lot larger then the dart but it seems they may be a bit shorter in span. So I see no reason to make the booster fins stronger if they are not having any more stress. You said .5oz cf, I have seen nothing in that range. What would be a good weight and # of layers for tip to tip glassing on a rocket like this? I will check more on the web, and maybe drop by some local composites shops and talk to them about it. Maybe even bring in the dart, , with fins tacked on, or completly attached with fillets, and see what they think would work well. I could explain the type of forces being applied and get a glass that will strength that joint.

 

[smurf]

Here's the rocksim file for the boosted dart. I don't know how to put the tailcone inside the transition but apparently there is a way. I didn't put in things like the hardware or add for epoxy and paint, etc....

Anyway you can get the idea from this. The front coupler on the booster will house a timer for pyrotechnic separation of the dart. I'll also make an adapter for the thrust tube and then another fincan for the dart so I can launch it as a two stage rocket.....should be able to get serious altitude that way.

 

[smurf]

The 0.5 oz carbon is usually referred to as either tissue or as matting. On the ACP website look under "Mats" and then at the price list...they have it at a decent price. It us typically used to provide a conductive covering for other structures. If you look at the rocksim file i posted you'll see the fins are pretty small on the booster too. Normally i use rocksim to get an approximate minimum size for the fins to get the CP where I want it.

If you have .125 G10 you can use that too without too much of a weight or drag penalty. If you decide to do tip to tip, I personally would use nothing heavier than 5.5 oz plain weave cloth or tape (the tape is just narrow cloth but it's relatively available.) One layer on each side and you could drive nails with it. Some places have tape up to 6 inches in width, try mrfiberglass.com. I don't think it's necessary though if you design them so they won't flutter (short span and low aspect ratio). I've got a Raven EX with surface mounted fins the way I described and I've honked it around on some pretty big motors with no problems on the fins. It gets well over 10K on a J570 and breaks mach. I wouldn't even put a parachute in it except it would smart if it hit someone...

 

[jraice]

So you are saying a layer on each side with 5.5oz or less CF would be a good solid attachment? I am looking into tapes, just have to make sure 6"s is enough to cover the entire fin. So .093" fins it is, I guess... I will post the file after I get it all ready and see what you guys think about the fin design, and whether or not I should tweak them at all for a better, less flutter prone design.

 

[smurf]

What i do is put three one inch wide (depending on the size of the fins) strips of carbon tissue over each fillet. This has proven more than adequate for me so far without the tip to tip reinforcement. If you are going to do tip to tip, i'd still put the CF tissue reinforcements over the fillets since it adds virtually no weight and is quite sturdy. Then lay on the tip to tip reinforcement. Really what you will be doing is stiffening the fins with the tip to tip which probably isn't necessary if you aren't going above mach 2.5 or so. It won't hurt to overbuild but you will be adding weight where you need it least. This will be nothing compared to using that solid urethane tailcone though!!

 

[jraice]

After getting more into this project I realize it isnt what I was looking for, I wanted a more complex build with new techniques (composites) but also a very high speed vehicle, my goal for 2006 is mach 2. I have decided to make a minimum diameter 54mm rocket, I have made beautiful 2.56" CF/FG tubes, but they were not pure (had thing kraft inside). I want to try using a mandrel and making a pure CF tube. Where can I get this tissue? My plan is to use .063" G10 fins and use one layer of 5.8 ounce CF on each side. According to another thread this gives a fin with a thickness of about .88"s. I could vacum bag but I am thinking about just using two flat surfaces sandwiching the fin with the CF in place (flat wood surfaces would have mylar to keep them from sticking) and then putting some weight on top. Then I will fillet (and consider the tissue) and do maybe another layer of tip to tip. I read a thread that did a layer of 5.7 ounce CF on the .063" fin stock, then attached them to the rocket and did 3 tip to tip layers of 5.7oz CF. That seems overkill, but one 5.7oz tip to tip on a 5.7oz CF glassed fin seems about right. Right now I am most excited about the CF tube making, I plan on use some sort of vacume bag and a cure chamber for a very smooth tube... thanks for anybody that helped with this thread, it was a great learning experience... and this CF 54mm rocket could always be converted into the booster for a booster dart ... the questions before the actual build in this thread slowed it down a bit, so I plan on begining construction and taking some pics before I start the 54mm rocket build thread...

 

[dbarrym]

Jraice -

PM me with your Email and I'll send a reply to your recent PM; it's too long to send via PM or to post here.

I have used a lot of the CF mat (or tissue) in my RC models, it's great stuff BUT it is a resin sponge! It is the best thing to use when you want a light layer of carbon reinforcement, given that 2 to 3 oz. CF cloth is ungodly expensive and hard to find these days. You should also plan on using a FG veil layer over the mat as it is a bit 'lumpy' and it is easy to sand through.

Cheers -

 

[jraice]

I know it is very expensive, but for the amount I am doing it shouldnt be to bad, ACP has some for $55 a yard, 5.7oz plain weave CF...

 

[cjl]

What he meant is that 2oz CF is ungodly expensive (and I happen to agree). I needed some recently - payed over $35/foot for it (only bought a tiny bit though). Great stuff though for extreme light weight rockets.