what is the Best way to get a small rocket down quickly

[ScrapDaddy]

what is the Best way to get a small rocket down I'm talking 35 or less grams with motor please answer poll and please post tips on thread. I'm trying to get a 35 gram rocket (including motor) down from 4500 feet as fast as possible without damageing the rocket, I have built the rocket to withstand about a 33 mph impact... That being an estemite I have renforced everything and I'm flying in snow covered ground

NEW:AnD Be able to recover it

 

[powderburner]

So you're working with low-power motors? Really doesn't matter that much if they are low- or mid-, if you want a delayed deployment this is going to have to be set up about the same way as high-power dual deploy.

You could use the engine ejection charge to separate the rocket just above the MMT and fins, leaving the two sections tethered by a suitable shock cord. This configuration will tumble/freefall at a decent rate of descent and normally doesn't drift too much. You could even let it fall this way all the way to the ground.

Or, you could configure the forward section with a small electronic timer or altimeter, set to trigger a second deployment at low altitude. The deploy mechanism could be an igniter/BP ejection charge for a conventional approach to getting out a chute or streamer. Definite LEUP territory, for the igniter and maybe also for the BP.

Or you could use a length of pyro fuse (Visco-type) ignited by the motor ejection to burn for a pre-measured time before pyro ignition of a BP ejection charge. (But be warned: this approach using fuse makes some people upset here on TRF) Use of BP for a separate (not located inside the motor) ejection charge might get you in trouble, might require a LEUP. Probably safest to use two redundant lengths of fuse, to increase confidence that at least one will get lit.

Or you could have a mechanical spring (or rubber band) set up to open the side of the upper body tube, with the BT held closed by thread, and use the electronics to power up a small piece of nichrome to burn the thread, let the recovery bay flip open, and release the recovery device. No BP=no LEUP, and plain nichrome (without pryrogen) is not an "igniter"=no LEUP.

 

[ScrapDaddy]

I wouldve done duel deploy but I have only about 5 grams to work with not to mention it's a minimum diamiter 18mm...... And my limited budget:roll:

 

[powderburner]

That's why I suggested that third one.

I think someone makes a little electronics card now that fits inside 18mm. I think it only costs some $20-30-40? If you used a simple nichrome wire to burn a retaining thread, you wouldn't need the weight of a cannister for containing ejection charge combustion. You just might be able to squeeze it all in there.

Nose-blow works just fine too. If you are clever, and design with the fins set slightly forward and the motor sticking out the rear, so the lower portion of the rocket descends butt first (with the NC flopping around above), the motor will hit the ground first and take most of the landing damage.

 

[ScrapDaddy]

Well all in all the guys did warn me about not getting it back : D but I think the tumble and nose blow have alot of potentual though I do think that I should maybe stick with somthing non-electronic related because I'm so confident that I would lose it I even only ordered one motor but I do reall want to get it back.......:2:

 

[Handeman]

I would recommend a 2" by 20" streamer. I would also recommend the streamer be made from silver mylar. Launch it on a bright sunny day and use the flashes coming off the streamer to track it on the way down.

 

[Gillard]

I would recommend a 2" by 20" streamer. I would also recommend the streamer be made from silver mylar. Launch it on a bright sunny day and use the flashes coming off the streamer to track it on the way down.

I've second this, a small rocket from the height needs to be tracked somehow, noseblow and tumblow will bring it down faster, but you may never recover it. you could also try and coat the rocket in very thin mylar to get the flashes

 

[ScrapDaddy]

Ohh how about red Mylar?

 

[NjCo]

Ohh how about red Mylar?

With a small rocket at that altitude you likely won't see anything. A small rocket at half that altitude is hard to see. The only hope is if you have some type of reflective material that will catch the sun and then you could see the flashes. You'd just need a sunny day. The red mylar might work if you coat the rocket with it. Then use silver mylar for the streamer. The silver would be easier to see at high altitude and the red would provide some contrast to make it easier to see at a lower altitude.

 

[MarkII]

Geez, what are you launching and what are you putting it up on? Whatever you use, make sure that it's disposable, since the odds of finding the rocket afterward are not good.

I'm assuming that you have run a simulation of this design in RockSim. If so, please make sure that you adjust the settings in the "Launch Conditions" tab so that they approximate your actual field conditions (including any wind), and that the weight of your design is consistent with the actual weight of the built model. (Not all of the parts or materials in the database have accurate weights.) Also avoid using "Polished" as the surface finish for anything, unless you are a professional auto finisher and have done all of the rocket's finish at work. "Glossy" is usually about the best that a non-professional can do; choosing "glossy" vs. "polished" can have a big impact on how RockSim represents the flight.

Finally, you can "build" a rocket out of tissue paper in RockSim and launch it on an M; the program will dutifully report the acceleration, top speed, maximum altitude, etc. without ever mentioning that such a rocket would shred within a fraction of a second after ignition. Similarly, you could sim a standard, unmodified Alpha on an F or a Big Bertha on an I with it. RockSim won't complain, and it will never catch errors like that. You have to give it realistic data if you want it to give you reliable results. Just a word of caution.

MarkII

 

[ScrapDaddy]

I Think Its time i break out the 1500 grit sandpaper:shock:

 

[ScrapDaddy]

its on a D21 i could go higer on a D10 or when the start producing them again , the D3

 

[MarkII]

I Think Its time i break out the 1500 grit sandpaper:shock:

That won't even get you close to there! :roll:

MarkII

 

[ScrapDaddy]

but it says "polishing' it

 

[The EGE]

Mark II: He's building an 18mm Machbuster for an AT D21-7. You're definitely right about the disposability factor; an 18mm diameter rocket is hard to spot at 300 feet, much less 3000 feet.

If you take out the 18mm motor mount, an Alpha could theoretically survive an F. An F12-5 gives 745 fps (0.67 Mach), and an F24 still only 900 fps (0.81 Mach). (See attached .ork file). If you fillet well enough, a stock Alpha should be able to survive an F motor.

As for the Big Bertha... I offer this...

ScrapDaddy: My personal recommendation is to not use any recovery device, maybe a small (~1" by 12") streamer; just attach the nose cone and body by 24" of shock cord or kevlar thread. Then, when you prep the rocket for flight, put as much flour as weight permits into the rocket. It doesn't take a lot; half an ounce in my 29mm machbuster left an obvious cloud at 4500 feet.

Color your rocket bright red or orange with magic markers (don't waste weight with paint). Launch it only on a very calm day, or a very large field, with others watching. Launch it vertical, or just a few degrees off. When you see the ejection puff, trace the direction down to a object in the distance. Wait and watch the sky; from the altitudes your rocket will achieve, it'll take several minutes to get down to ground level.

If you don't spot it on the way down, then slowly walk in the direction you saw the ejection puff and stop every 50 yards to take a look around. As long as there's little wind, your rocket should be within 50-100 yards of the line.

View attachment Alpha.ork

 

[ScrapDaddy]

hmm loose flour with a flame this is the same :y: as the big london bakery fire

 

[ScrapDaddy]

I'm worryed about doing a first flight on a 1/2 A6 rocksim says 650 feet!!

 

[The EGE]

hmm loose flour with a flame this is the same :y: as the big london bakery fire

Not much of an explosion risk, though; the ejection charge will have completely burned before the flour reaches the right (relatively low) concentration to explode.

Try a 13mm adapter and a 1/4A3-3.

 

[MarkII]

As for the Big Bertha... I offer this...

Gee, LOC tubing, LOC motor mount, G10 fins, fiberglass reinforcement...that doesn't sound like a stock Big Bertha to me. In fact, it doesn't even sound like Skill Level 1...

My point about RockSim is that it won't filter out bad data and you can tweak the settings to show amazing performance in conditions that you will never encounter in upstate NY. And you can specify construction materials and components that don't actually exist in reality. RockSim won't mind a bit. I'm just suggesting that S-D use some common sense, that's all. No one who has responded to this thread has actually seen his design.

At 4500 feet, he'll be extremely lucky to even see the puff of smoke from the ejection. I'm not arguing against the project; in fact, I'd urge him to go for it. It will be a great experience no matter how it turns out.

A few years ago, I lost a 30" long, 29mm minimum diameter rocket on its first flight on an F25. It had simmed to 4500 feet, too. It disappeared from sight at somewhere around 1000 feet. We had several spotters, but none of them saw or heard the ejection charge fire. (It would not have been loud enough to hear from a distance of 4500 feet, anyway.) Despite that, I don't regret the experience one bit. I made some friends during it, actually.

MarkII

 

[ScrapDaddy]

It would be really cool though but the RSO would be really mad

 

[ScrapDaddy]

Ok I just tweeked everything rocksim now says 3200feet much better oh and now it's 375 for a 1/2 A6 MUCH more realistic

 

[ScrapDaddy]

Gee, LOC tubing, LOC motor mount, G10 fins, fiberglass reinforcement...that doesn't sound like a stock Big Bertha to me. In fact, it doesn't even sound like Skill Level 1...

My point about RockSim is that it won't filter out bad data and you can tweak the settings to show amazing performance in conditions that you will never encounter in upstate NY. And you can specify construction materials and components that don't actually exist in reality. RockSim won't mind a bit. I'm just suggesting that S-D use some common sense, that's all. No one who has responded to this thread has actually seen his design.

At 4500 feet, he'll be extremely lucky to even see the puff of smoke from the ejection. I'm not arguing against the project; in fact, I'd urge him to go for it. It will be a great experience no matter how it turns out.

A few years ago, I lost a 30" long, 29mm minimum diameter rocket on its first flight on an F25. It had simmed to 4500 feet, too. It disappeared from sight at somewhere around 1000 feet. We had several spotters, but none of them saw or heard the ejection charge fire. (It would not have been loud enough to hear from a distance of 4500 feet, anyway.) Despite that, I don't regret the experience one bit. I made some friends during it, actually.

MarkII

Sounds like you were flying an apogee aspire there!:y:

 

[MarkII]

You can buy large bottles of powdered tempera paint at Michael's; this is the classic tracking powder that is used in altitude contests. It may even help to mix some glitter into it.

Ok I just tweeked everything rocksim now says 3200feet much better oh and now it's 375 for a 1/2 A6 MUCH more realistic

3200 feet is much lower than the original estimate, but it is still quite an impressive altitude for a rocket powered by an 18mm motor. And 375 feet is pretty good for a 1/2A6, too.

MarkII

 

[MarkII]

Sounds like you were flying an apogee aspire there!:y:

Actually it was a scratch-built upscale of the FlisKits Midnight Express. I used 3 layers of cardstock in the airframe and I made the fins out of basswood. I was intending to just give it a test flight on an E9 with an adapter, but someone from the club offered me an F25 to fly it on, and I simply couldn't pass up the opportunity.

I also lost a 24mm upscale of the same rocket on a D12 at that same launch.

MarkII

 

[ScrapDaddy]

ihows that for size i also have the rocksim file

View attachment rocket asp.bmp

View attachment The All American machbuster.rkt

 

[ScrapDaddy]

You can buy large bottles of powdered tempera paint at Michael's; this is the classic tracking powder that is used in altitude contests. It may even help to mix some glitter into it.

3200 feet is much lower than the original estimate, but it is still quite an impressive altitude for a rocket powered by an 18mm motor. And 375 feet is pretty good for a 1/2A6, too.

MarkII

Don't worry I'll get 4700' when production of the D3 starts up again

 

[NjCo]

You can buy large bottles of powdered tempera paint at Michael's; this is the classic tracking powder that is used in altitude contests. It may even help to mix some glitter into it.

I've gone the glitter route. It looks nice on a sunny day at a relatively low altitude but at 3000+ I can't say it'd do much good. Powdered paint is relatively light weight and is a better choice than flour because of the color. Red is a good choice due to the high contrast. Another option is colored marking chalk which you can get at a home center. Not much difference in weight. The paint is probably cheaper though. But then again make sure you're flying on a dry day!

 

[MarkII]

A folded streamer will cause the rocket to descend more slowly. I'm not sure if you want that or not, since it could increase the drift distance. Folded streamers are commonly used in duration events in contests. If that's what you want, it's fine. It is tough to avoid putting at least some folds into a Mylar streamer, but I suspect that the "Folded" check box in the streamer's property sheet has to do with whether or not the streamer is a competition-type.

Are you planning to reinforce the balsa fins? You may or may not need to, but I suspect that it will be difficult to keep 1/16" balsa together at 1.14 Mach. You also need to watch the deployment velocities. You are fine with the A8, B6 and C6, but you are marginal with the A3 and the D3, and you are well into shred territory with the D10 and D21. There are no longer delays available for either one of these motors, but you might be able to take advantage of some techniques for slowing down the "pay out" of the shock cord, which could give your rocket more time to slow down before the streamer unfurls. I can't remember what the technique is called, but there is a way to coil up the shock cord so that it stretches out more slowly as it exits the rocket. Oh, wait, I just noticed - you don't have a shock cord in the design.

I also noticed that with a D10-7, your stability margin is 0.63 and with a D21-7 it is 0.68; that's dicey in both cases. You could add more nose weight to compensate, but a better solution might be to lengthen the rocket a little bit. But then, the upper "strake" part of the fins is no doubt responsible for this; they bring the CP forward. Eliminating those sections would bring the CP back toward the rear, and would also decrease your rocket's drag. I doubt that your rocket needs those extensions. Here is an example of a Mach buster that uses much smaller fins (smaller fins translate into lower drag).

MarkII

View attachment oop_fsi_mach1dart.rkt

 

[ScrapDaddy]

A folded streamer will cause the rocket to descend more slowly. I'm not sure if you want that or not, since it could increase the drift distance. Folded streamers are commonly used in duration events in contests. If that's what you want, it's fine. It is tough to avoid putting at least some folds into a Mylar streamer, but I suspect that the "Folded" check box in the streamer's property sheet has to do with whether or not the streamer is a competition-type.

Are you planning to reinforce the balsa fins? You may or may not need to, but I suspect that it will be difficult to keep 1/16" balsa together at 1.14 Mach. You also need to watch the deployment velocities. You are fine with the A8, B6 and C6, but you are marginal with the A3 and the D3, and you are well into shred territory with the D10 and D21. There are no longer delays available for either one of these motors, but you might be able to take advantage of some techniques for slowing down the "pay out" of the shock cord, which could give your rocket more time to slow down before the streamer unfurls. I can't remember what the technique is called, but there is a way to coil up the shock cord so that it stretches out more slowly as it exits the rocket. Oh, wait, I just noticed - you don't have a shock cord in the design.

I also noticed that with a D10-7, your stability margin is 0.63 and with a D21-7 it is 0.68; that's dicey in both cases. You could add more nose weight to compensate, but a better solution might be to lengthen the rocket a little bit. But then, the upper "strake" part of the fins is no doubt responsible for this; they bring the CP forward. Eliminating those sections would bring the CP back toward the rear, and would also decrease your rocket's drag. I doubt that your rocket needs those extensions. Here is an example of a Mach buster that uses much smaller fins (smaller fins translate into lower drag).

MarkII

You mean crocheting the shock cord? And my reasoning behind the allowment of the marginal static stability is that about 5 inches of the pad the rocket is at a "safe take off speed" so once that speed is reached that the static stability no longer applys...... I think that's how it works the faster the more stable it is right? Because the fins are more effective?And know do you know why I was asking about an anti zipper design?And to think Velcro was the solution..

 

[ScrapDaddy]

I have filleted the fins with epoxy clay and have added paper skins soaked in CyA and what should the shock cord be? Kevlar?nylon?bungee(hmmm debatable) and what should the legnth be