Here's a starter ROCSIM file from http://www.rocketryforum.com/showthread.php?t=8606#1....the rocket kept going UP and UP and UP after 12 hours of simulation! (They ejected the the strap on boosters during sim flight).
Even includes information from Adrian and his Parrot/Raven systems.
Device to make sure upper stage is within safe angle from vertical (i.e. no more than 25 degrees), before firing upper stage.
As I recall from our conversation on Saturday, you spoke of the Delta having an issue becasue you ignited all the motors at the same time. The outboard motors fired and were almost spent before the center engine came up to thrust and the rocket did not really get off the pad until the center one did come up to thrust. That said, will you put a firing delay into the outboard motors so they come up to thrust at the same time as the center motor? Of course if they do that, you will not have the slow lift off, will you? What is the scale of this rocket? 1": 1 foot gives you a rocket that is about 220" or 18'8" tall. Any idea how high it will reach on flight. Are you considering 6 -75mm "M"s and then a 98 or 150mm in the center? Better find some sponsors or volunteers to make a bunch of motors. (How much black powder do you need for an ejection charge, and a separation charge for getting the two stages apart for the air start?)
I believe if the Delta II was flown again there was talk of using the club's system to ignite the center motor. Then use on-board timers with pull wires for the outboards. That way the center motor comes up to pressure, lifts the rocket and then the outboards light.
Another reason the outboards lit first is because they were CTI - and used a simple e-match to light them. The main motor was a 75mm AMW reload and it took a second or two to come up to pressure.
6 75mm M motors is a real challenge to get to light at the same time, and they have enough thrust to do some very serious damage if only a couple of them come up to pressure before the other ones do. If you move up to 98mm or 150mm power then you have to design a rocket with much much more strength for the up part and the down part. 152mm hardware isn't light 🙂 Making a bunch of motors isn't an easy endeavor also - especially in those sizes.
Edward
Thanks Ed. I understand. Just curious what Steve's plan for all of this is, or has it been decided yet? If it is still undecided, which direction is it leaning. From the perspective of someone like me, the questions are how would I build this, how are the owners of the rocket palnning on doing it, what can I learn from their method, and do I think I might have a better idea, and should I be so bold as to propose the idea, and finally, what can I bring to the table to contribute to this organized madness? I am working on the design of my L3 project and so I am working on all these concepts formulas, figuring out stresses, is it strong enough, etc. I guess I am asking the same questions for this project and trying to learn how I can contribute before the first adhesive is applied.
An L3 rocket is a lot simpler than a rocket of this scale. Once you get to this size the up part isn't the hardest, it is the down part. Ask Kevin Trojanowski about big projects. They design them around with recovery first in mind, not last.
If you want to see a larger project done right go no further than Mark Lionberger and John Bixler's 3/4 scale Nike Smoke. Every detail was planned in advance before they built it. After the first flight they rebuilt some aspects because of how it recovered. It is a very, very well thought out project. And everything they used on the project the made sure they weren't testing new concepts and ideas out - because at that scale an 'oops' is generally followed by unpleasant news.
As I've been flying rockets longer, I've been building less and less of them. Mainly because I've distilled my rockets down to simpler designs, and because many times I just can't come up with a design that I like so I'll forgo it until I can get it right.
Edward
As I recall from our conversation on Saturday, you spoke of the Delta having an issue becasue you ignited all the motors at the same time. The outboard motors fired and were almost spent before the center engine came up to thrust and the rocket did not really get off the pad until the center one did come up to thrust. That said, will you put a firing delay into the outboard motors so they come up to thrust at the same time as the center motor? Of course if they do that, you will not have the slow lift off, will you?
Edward answered this perfectly ..
What is the scale of this rocket? 1": 1 foot gives you a rocket that is about 220" or 18'8" tall. Any idea how high it will reach on flight. Are you considering 6 -75mm "M"s and then a 98 or 150mm in the center? Better find some sponsors or volunteers to make a bunch of motors. (How much black powder do you need for an ejection charge, and a separation charge for getting the two stages apart for the air start?)
I am going with 12" sona tube from Home Depot .. that's my budget. So I divided the dia (4.1 meters) by 13.5 and got 12". Using that formula, the height will be 13.5'. The boosters are 4.5" dia and 42" tall plus a 7" nosecone. The trend on my rockets (cardboard tube with fiberglass) is 10' tall is 100 lbs, 16' tall is 160 lbs, etc. The Delta with it's boosters was a little more, 10' tall 125 lbs or so. As Edward can attest, we had to add a #$@Load of weight to the nosecone at the pad as we assembled/loaded the rocket to get the CG right. I may stretch the length a bit to help with that, but I want to keep the scale as close as possible to the original. With the extra structural support for the big motors and boosters, I estimate we'll be around 200 lbs. on this.
I have spoken with my motor builder friend and am looking at a 6" 'O' motor with maybe 'K's in the boosters .. they're more for visual effect in this flight. If I 2-stage it like I want, the 2'nd stage will have a 4 motor cluster .. probably 'K's as well. Of course this configuration could be too much or too little power .. depending on the final assembled weight. BP is a minor issue .. we'll have plenty available.
I'll get Rocksim set up soon and create a model. It usually works well for me and believe I can get a decent ballpark number for accel, velocity and altitude.
This helps me a lot. It may not have been necessary for others, but sometimes I am pretty slow, so thanks. 🙂
Thanks Ed. I understand. Just curious what Steve's plan for all of this is, or has it been decided yet? If it is still undecided, which direction is it leaning. From the perspective of someone like me, the questions are how would I build this, how are the owners of the rocket palnning on doing it, what can I learn from their method, and do I think I might have a better idea, and should I be so bold as to propose the idea, and finally, what can I bring to the table to contribute to this organized madness? I am working on the design of my L3 project and so I am working on all these concepts formulas, figuring out stresses, is it strong enough, etc. I guess I am asking the same questions for this project and trying to learn how I can contribute before the first adhesive is applied.
It's more of a psudo-plan .. hehehe .. the size is firm, as it is what we have, but the specifics in some areas will be more 'fluid'. While real big motors do require a stronger framework, it is less critical in a 'low and slow' rocket like this .. and all the ones I build. It's beyond critical on the fast, min dia, type many of these guys build.
Funny, there are 2 of you guys really up for this project, you and Rich .. one I Parker (WAY South) one in ... uh.. basically Wyoming .. still need that Longmont location!! 🙂
I remember talking to Mark L. and John B. after the Nike Project and after it was done, they said they'd settle into some standard tubing because it eliminates a lot of work and increases consistency. They used concrete form tubing and then they reinforced with fiberglass. They had to overcome warping and it gained a lot of weight. They also built the MOAL (mother of all lathes) so that they could sand the tubes. Would it be practical to scale it down to 7.5" so normal components could be used?
I'm guessing the 6" O motor is 3 grains - probably a 60 pound motor ready to go? I'd say in the 20,000 Ns range? I know a 5 grain motor is ~90 pounds ready to fly. For the K motors I'd almost go to 75mm for them. It reduces the length of the motor and increases the burn time. I'm guessing you aren't looking for something in the K1000 range in a 54-2550 case, but more like a K300-500 range. A 2 grain 75mm case is also less grains to cast and core and assemble and you have to worry less about stepped cores and geometry.
Edward
PROTON SCALE DRAWING FROM ROCKETS OF THE WORLD
I remember talking to Mark L. and John B. after the Nike Project and after it was done, they said they'd settle into some standard tubing because it eliminates a lot of work and increases consistency. They used concrete form tubing and then they reinforced with fiberglass. They had to overcome warping and it gained a lot of weight. They also built the MOAL (mother of all lathes) so that they could sand the tubes. Would it be practical to scale it down to 7.5" so normal components could be used?
I'm guessing the 6" O motor is 3 grains - probably a 60 pound motor ready to go? I'd say in the 20,000 Ns range? I know a 5 grain motor is ~90 pounds ready to fly. For the K motors I'd almost go to 75mm for them. It reduces the length of the motor and increases the burn time. I'm guessing you aren't looking for something in the K1000 range in a 54-2550 case, but more like a K300-500 range. A 2 grain 75mm case is also less grains to cast and core and assemble and you have to worry less about stepped cores and geometry.
Edward
No, I want it big. I've had good results with sona tube and glass. Heavy yes, but I'll have enough motor and want it to finish below 5K ft. I'm going big on all motor mounts and can adapt down if needed .. better to have it there if you need it. Definitely want longer burn boosters for better visual effect. Of course I will need a lot of cases in this 'scenario', 10 K's, which may not be available. I'll be SIM'ing a lot of scenarios as we go. Availability may dictate what I settle on.
PROTON SCALE DRAWING FROM ROCKETS OF THE WORLD
Thanks Greg, I have that same diagram. I'm using it for most dimensions, but don't like the payload area .. doesn't look quite like the images I've seen.
What an awesome book though!! Got my Delta II specs from there as well.
For the nose cones for the six boosters on the first stage, if we had a set of full size drawings, we could then make templates to work with and I could carve the cones out of foam and then we could glass them. That would keep them pretty light, yet very easy to make. The nose cone for the whole rocket could be done the same way. I have made nose cones, prop spinners, reducers, couplers, etc. and learned how to do it when I was using 1/4" plexiglass glued together to make the same sort of shapes for the models of oil refineries that I used to make years ago. I think the refinery models were harder to make because of the plexiglass and because the reducers had offset centerlines as the diameters changed. I know it can be done. I am also wondering what you envision for how to separate the two stages before you airstart the last 4 "K"s
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