How do you stage composit rocket engines?

I am building a rocket and i want to use two or so F engines, how do i stage these

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S1L3N7 SWAT8 years ago
It's been a long time since I've launched any rockets, but the way I did it was tape them end to end. So you have one engine with the nozzle side clear, and another taped with the nozzle side to the open end of the first engine. When the first engine burns through the thrust phase and fires off the ejection charge it will light the next engine in the series. You can rig them up to fall off once they light the next one, but that depends on the design of the rocket. Some multi-stage rockets have fin sections that fall off with the engine, so for example a 3 stage rocket would have 3 sets of fins on it, and the last one stays on the rocket. Since the engines burn through completely leaving just a hollow tube, you could probably get away with them staying on, but that may cause balance issues since the thrust is now originating from higher up the rocket. Anyway, hope that helps you some.
If you search for it, you will find software that simulates based purely on mathematics what is possibly going to happen with a rocket design, the type of fuel and the amount of thrust it can produce as well as burn time and the design will also factor in how the rocket will perform. That way, you can test easily and safely and cheaply any number of scenarios before you actually try...
nicelly5 years ago
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nicelly5 years ago
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Prfesser8 years ago
As garmtn says, composite motors are different. First, no one makes "booster" composite motors; all have delays. Second, they must be ignited at the forward end rather than at the nozzle end. Taping the motors together works for blackpowder motors (Estes, etc.) but usually does not work for composites. Which means that there are two general choices: 1. Use an electronic timer with a g-switch, or altimeter, along with a proper igniter, to ignite the second stage some time after the first stage ignites or after liftoff. 2. Use reliable timing fuse to ignite a proper igniter in the upper stage. Usually the timing fuse is ignited at the same time as the lower stage, and provides a fixed delay before it lights the upper-stage igniter. The latter method requires some trial and error. Most of the folks who fly big rockets (H-O power and higher; check out use electronic altimeters. They aren't cheap --- on the order of $100 --- but they are reliable if properly installed.
peoplerstupid (author) 8 years ago
I found the answer to this on the only way to stage composite engines is to use staging electronics
garmtn8 years ago
Hi, If anyone was paying attention he said," composite" motors. The fuel is way inside, hench the long copper igniter. Sooooooooo, don't know if the old "standard" method of staging will work. You can try that with a backup. A piece of "fast burning fuse" in upper motor. As long as 1st motor a booster, don't see why wouldn't work.
westfw8 years ago
Sorry, but the techniques people are listing generally only work for "Black powder" motors (like Estes or Quest A through D motors, although there have been F black powder motors in the past (infamous FSI F-100.) The Black Powder motors are essentially end-burners, and when the forward end of the motor burns through, flying back powder particles fly up and are good for igniting the next stage.

There are several reasons that this doesn't work for "Composite" rocket motors, such as those from Aerotech.
  • First, composite motors are not end-burners, but slot or core burners, and if it weren't for the delay charge in the forward closure, flames would be shooting out both ends throughout the entire burn (you occasionally see this happen when someone fails to properly assemble a reloadable composite motor; it is NOT GOOD for the rocket.) This also means that composite motors are not usually available with the "zero-delay" that you want for igniting the next stage.
  • Second, composite motors are considerably more difficult to ignite than black powder; a few sparks flying up the nozzle are not hot enough, and are not going to make it to the forward part of the grain where you really want to ignition to happen.
  • Third, a F-sized first stage is getting pretty large and heavy for the "tumble" recovery that is frequently used for initial BP stages.
All that said, I haven't actually provided an ANSWER. That's because I haven't ever done it! Most of the successful composite stagings I've seen, heard, or read about have involved electronics - it is relatively easy to recognize first-stage burnout and electrically ignite the second stage in a way similar to ground-based ignition, given either beefy power sources or sensitive ignitors. This is not without peril, of course; such electronics are subject to being "fooled", and second stages have been known to go flying off long before they are supposed to, occasionally causing near-disasters. Also, ignition of composite motors is notoriously finicky, even on the ground, so it's not uncommon for the second stage to fail to ignite. (This isn't good for the rocket either.)

You may want to consider clustering (igniting two F motors at once on the ground) rather than staging. Frankly, staging of model rockets has never made a lot of sense to me; staging is primarily a technique of improving the mass fraction of the overall vehicle, and the mass fraction of model rockets tends to be so sucky in general that staging doesn't help much for all the considerable complexity that it adds. Try some simulations...

If you're interested in "advanced" topics like thism I would urge you to join one of the model rocketry organizations (NAR or Tripoli), or at least peruse some of their magazines. Here are some of the articles on staging that have appeared in the NAR magazine:
DS2 Author:  Celetti, Big Al and Lawton, Rodger  Source:  MR; Apr, 1976, Vol. XVIII, No. 3, page 4. Flashbulb Staging Author:  Dye, William  Source:  MR; Nov, 1975, Vol. XIX, No. 10, page 11. Optimum Delayed Staging Author:  Kuechler, Thomas C.  Source:  MR; Aug, 1975, Vol. XVI, No. 7, page 10-13. Rocket Tek  Multi-Staging Author:  Hellmund, Mark  Source:  SR; Apr, 1994, Vol. 37, No. 2, page 19. Some Notes on Delayed Staging Author:  Apt, Jay  Source:  MR; Feb, 1974, Vol. XVI, No. 1, page 20.76 Staged Fat Boy Author:  O’Donnell, John  Source:  SR; Sept/Oct, 1998, Vol. 41, No.5, page 16-18. Technical Notes on Mercury Switch Staging Author:  Dye, William  Source:  AS; Dec, 1984, Vol. 26, No. 10, page 5-8. Wilcox Staging System, The Author:  Wilcox, G. Allen  Source:  MR; Oct/Nov, 1976, Vol. 18, No. 9, page 4-5.
KentsOkay8 years ago
I know there are some articles their on multi-staging. However, F engines are pretty big, you may have to seek a more technical means to prevent catastrophe
peoplerstupid (author)  KentsOkay8 years ago
yah, i changed the design and now I'm using D's for the first two stages and an E for the last stage
I'd do E > E > D, and reduce the tube diameter on the last stage.
2 F's! That is quite some power. Anyway, the easiest way to stage 2 rocket motors is to stack them on top of each other, in two stages. Build the top like any single stage rocket, then build the lower stage. You'll load this form the top, pushing the engine in to the fuselage in the opposite direction the rocket will be traveling. Put a thrust ring in the bottom of the lower stage, so the engine will but against it. When the engine is ignited, it will push up against the engine above it. To load the rocket, insert the upper motor. Then tape the lower motor two the upper, and slide the lower stage fuselage over.
Tip: Rotate the lower stage to stagger the fins, increasing fin area and stability.
P.S. Remember to use a F-0 motor, you'll blow up rocket! If this is your first multi stage rocket, you might want to start with a kit, such as the "CC Express.":