Gap Staging

[tbzep]

They stopped putting that suff on motor lables in the mid 90's along with most of the different motor type color coding. Used to be Upper stage motors were had purple lettering, lower stage or single stage green, and boosters Red. Currently all but boosters are green or green&blk lettering with boosters remaining red.
But none of this has a thing to do with a delayed/ejection charged motor being used as a booster. There is just no bases for such a suggestion.

It has everything to do with it. The motors were labeled with the manufacturer's intended use for decades. It was also printed in literature. Delayed/ejection motors were not intended to be used as boosters by the manufacturers. That's the same logic you used when saying a booster couldn't be used as a single stage motor.

Not a short memory; Just wanted to see if someone was still carry the same gurdge...as suspected, you are.

You're just killing me, John. Everybody knows that gurdges are way to energetic to be carried around like a pocket knife. They have to be contained in a magnetic bottle.

Really no defense necessary but since you obviously wanted to try again to make some sort of statement, I'll be happy to rebut it.

The Difference my friend, is I wasn't suggesting such a use by inexperienced modelers in your average run of the mill mod-roc. Rather speaking about a semi-common practice used in spacific tiny competition models where the modeler HAS the knowledge to do and has done the research to make such a system work Safely. It's all about WHO we are suggesting a specific technique to and in what context.

And you seem to expect that only experienced modelers will read it. This is a publicly accessed forum and the inexperienced come here all the time. If you don't want me to talk about zero delay motors for single stage, then you shouldn't talk about delayed motors for boosters in the open forum. Plain and simple.

I'd still have to "slam" as you put it, such a discussion in this forum (LPR) if proposed to be done by JohnQ rocketeer. The quote is still just a revelant as it was in TRF 1.0. "Booster motors ARE NOT INTENDED to be used to deploy recovery systems, PEROID."

My point exactly. John Q. Rocketeers read all kinds of posts, including yours justifying use of single stage motors as boosters, which by definition should be just as much against the safety code as Bob Kaplow's zero delay booster used as a single stage motor. Single stage motors are not intended to be used as boosters by the manufacturers, period.

Am I supposed to say I'm sorry I dared address a potentially harmful suggestion to inexperinced folks reading? Nope! it ain't a gonna happen bunkey, we have to Think before we Act or Type
Now lets put this pointless past bickering aside and get back to the subject of gap staging.

I've never asked anyone for an apology. I wouldn't start now. But it's funny that you think nothing is wrong with you talking about a potentially harmful act, but if somebody else does you see it with a different pair of glasses.

Gap staging and staging in general, good idea. Let's discuss the taped vs. gap method. I've never had a failure with either, but I can see where taped method might have a lower success rate. I'd suspect that motors taped together with a slight gap, or became gapped as they were inserted in the airframe might have problems, especially with cellophane. There's almost no volume between the two motors so pressure would build very fast compared with vented gap staging. I could see the tape weakened from heat and pressure causing tape failure, allowing separation before ignition of the upper stage. With radiation traveling fastest, low mass gases next fastest, and burning particles slowest, this could be a clue that burning particles may be the main source of ignition during staging. I wonder if anyone has tested for failure with masking vs. cellophane tape, hairline gaps between motors, etc.

 

[MarkII]

Mark:
Have to disagree with the flash pan analogy as they are notorious for NOT lighting all motors in the clusters while toasting the bottom of the model with a ball of fire. Spider igniters on the other hand are specially made to very closely fit a small tube directly in line with the throat of each clustered motor nozzle seperated by a very thin tiny gap. Observing these in Night operation shows clearly it's not flaming bits but actual Flame shooting directly into each nozzle and yet on larger clusters more often then not some motor or motors still do not light.
Neither of these examples really fit whats going on within the confines of a booster body with a sustainer motor up to 10-12" away. It does sort of fit with taped together booster/sustainer motors but then again we have to remember Tape butted motors have a higher failure rate then gap staged motors???
One thing I forgot to mention in the earlier post was the possible added effect of "Afterburn" as the propellant breaks through creating a pretty hefty length flame as well. I don't claim to know exactly how it works, but accept that it's some combination of these things that come together making the process very helpful for staging motors with some pretty impressive distances between motors.

Nothing that you have said contradicts the standard explanation of motor-to-motor staging, nor is it incompatible with what I previously posted. I have never tried flash-pan ignition of cluster motors myself, but I constantly read testimonials to its effectiveness on this and other forums, and thus I have to take the various posters' word for it. Your characterization of how the spider device works dovetails well with what I was talking about. Thanks for the acknowledgment.

MarkII

 

[MarkII]

They stopped putting that suff on motor lables in the mid 90's along with most of the different motor type color coding. Used to be Upper stage motors were had purple lettering, lower stage or single stage green, and boosters Red. Currently all but boosters are green or green&blk lettering with boosters remaining red.

I just had to check this out for myself. So I opened up my motor box and examined the labels. None of my motors are more than three years old. (I resumed flying model rockets in 2004.) Here is what I found:

Green motor code lettering: Estes 1/4A3-3T; Estes 1/2A3-2T; Estes 1/2A3-4T; Estes A10-3T; Estes 1/2A6-2; Estes A8-3; Estes B4-2; Estes B4-4; Estes B6-2; Estes B6-4; Estes C6-3; Estes C6-5
Purple motor code lettering: Estes A8-5; Estes B6-6; Estes C6-7
Red motor code lettering: Estes B6-0; Estes C6-0

Completely green printed label: Estes C11-3; Estes C11-5; Estes D12-3; Estes D12-5; Estes E9-4; Estes E9-6
Completely purple printed label: Estes C11-7; Estes D12-7
Completely red printed label: Estes D12-0
Completely black printed label: Estes A10-PT; Estes D11-P

Not a short memory; Just wanted to see if someone was still carry the same gurdge...as suspected, you are.

Really no defense necessary but since you obviously wanted to try again to make some sort of statement, I'll be happy to rebut it.

The Difference my friend, is I wasn't suggesting such a use by inexperienced modelers in your average run of the mill mod-roc. Rather speaking about a semi-common practice used in spacific tiny competition models where the modeler HAS the knowledge to do and has done the research to make such a system work Safely. It's all about WHO we are suggesting a specific technique to and in what context.
I'd still have to "slam" as you put it, such a discussion in this forum (LPR) if proposed to be done by JohnQ rocketeer. The quote is still just a revelant as it was in TRF 1.0. "Booster motors ARE NOT INTENDED to be used to deploy recovery systems, PEROID."

My friends call this type of qualification, "slicing the baloney pretty thin."

Am I supposed to say I'm sorry I dared address a potentially harmful suggestion to inexperinced folks reading? Nope! it ain't a gonna happen bunkey, we have to Think before we Act or Type
Now lets put this pointless past bickering aside and get back to the subject of gap staging.

Of course; how dare anyone contradict you?

MarkII

 

[luke strawwalker]

I actually saw this one launcher someone made, that was effectively an air cannon that the rocket slid down, with an electric trigger, that ignited the rocket at the same time as releasing the air. The leads to the igniter were long enough, and the motor took long enough to ignite, that it usually lit 10-15 feet in the air. Wish I still had that link. It was AWESOME!

Yeah, I'd like to see that!

Back when I was in high school, just before I graduated and went to mechanic's school and 'got out of rocketry' for 20 years, I was big into scratchbuilding, mostly using some 3-4 inch Christmas paper wrapping tubes and turned balsa nosecones. I built a model of the SS-17 Soviet ICBM and made a slide-in set of tailfins for it.

I used a screw-type post hole digger to dig a "silo" in the backyard and pushed a launch rod down in the bottom of it, and put the missile in the silo, because I wanted some pictures. I had stepping stone concrete 'silo doors' beside it and I installed a 1/2 A motor in it (bout 2 1/2 foot tall 3 inch diameter+ model) and "fired" it out of the silo just to get some simple photos of it rising out of the silo... it basically just cleared the silo and layed over onto the ground, flight ended.

Made some neat photos but I can't find them anywhere... guess they got lost somewhere along the way in moves... that was about as close to a 'cold launch' as I've gotten... OL JR

 

[Micromeister]

So who pulled your ponytail Mark?
That last comment was completely unnecessary and down right nasty...NO! down right Rude. Watch it bud!
Contradiction or corrections are fine, if they are revelant to the subject being discussed. Sometimes new or more current observations or facts can help further a discussion.

Very interesting Mark:
You are correct. When I got home last evening I looked through my motor boxes also, and found lots of mid to late 90's motors still printed with the colors and "Single Stage","Upper Stage" and red "Booster"lables. 90's Years letter Codes are 90-95= U-Z, 96-2000 A-E. I believe after 2000 they went back to printing the acutal date. Notice most of the newer motors are printed with all three colors on each lable green,blk and red, and the print got much smaller, I did find the words "Single Stage" in small print on a 2008 B6-4 and Booster in red on a 2007 D12-0, but couldn't find a "New" purple lable anything. So I stand corrected on that point, I was misinformed about the lableing change..I should have checked it out personally.

Does the fact the a motor says single stage mean it can't be used as an upper stage motor? Of coarse it does not mean that at all. Could it be used as a booster? Well that's were the water get a little murky... In a cluster its really not even a question YES of coarse it can....as a traditional staging booster...I have to say; Not by most......would it be a violation of the safety code to do so...thats were our discussion gets a bit grey for all the reasons we've already thrown around.


Mark:
Back to Flash pans; I've gotta say if your buying everything your reading on-line your gonna be very disappointed should you ever actually attempt using one. Like most things they can be a help in some instances but they are no were near "quite reliable" with clusters. Just as a single example; Look at the guy who attempted 288 A10's with a flash pan a couple year back...not really all that close. I've seen folks attempt Flashpans with smaller cluster down as far as 6 BP motors with only 4 or 5 motors actually light. Some folks have more "Luck" other far less. While it is true the smaller the cluster the better the percentage ignitions most of the time, that's still not anything to hang your hat on. We have a few folks that use the method on a semi regular basis just for fun. They really don't care how much it tears up the aft end of their rockets as long as they get to play with the powder. Too each their own I guess, when I fly clusters I like to remove as many unknowns as possible preferring a successful flight over the fun of the prangs. I'll hang my hat on my 40+ year cluster success rate over anyones.
Spiders on the other hand are Really KEWL with a pretty high degree of reliability with motors 5-8. Again as the motor count increases the reiability decreases. I get the feeling your only considersing smaller clusters in your comments. While Spiders offer a much better percentage with these motor cluster ignition potentials over most other alternatives, for smaller clusters (2-10 motors) Relay ignition remains my personal #1 choice. That said I am working on a spider for a large micro cluster with stainless tubing and another for a larger clusted LMR model just for fun.
It's my understanding the Meatball racing team is experimenting with a spider for Upper stage cluster scale models. This could be another interesting development.


Gap Staging vs Taped:
TB: don't have any numbers handy but know from lots of year on the field lots of folks suffer unlit upper stages with the instructed cellophane taped method as discribed in most of the kit instructions. Reasons are again unclear some drop the booster while others retain it all the way to the ground.

 

[bobkrech]

The facts are:

1. Gap staging will ignite a black powder sustainer motor. Read all about it in the Handbook of Model Rocketry.
2. Gap staging will not ignite an APCP sustainer motor. They need a lot more energy.
3. You can gap stage a black power motor with either a BP booster motor, or a BP or APCP motor with a short black powder ejection delay.
4. BP motors ignite very easily. You need only to heat the BP propellant to over 500 F for a short time and the motor will ignite. It doesn't matter if you use a pyrogen coated igniter, a nichrome wire igniter, or BP from a booster motor or an ejection charge. The will all work.
5. Gap staging only works if you vent the gap between the motors so that the cold air in the gap is pushed away by the hot gases from the burning BP. If you don't vent, it will not work. Read Stein's Handbook.
6. The use of a booster motor with a delay ejection charge has been used many times in competition. It does not violate any safety policies provided you determine that the length of the delay is short enough so the the rocket is still moving in the original vertical direction when the second stage ignites.

Bob Krech, TRF Propulsion Moderator
Member, NAR S&T

 

[tbzep]

The facts are:

1. Gap staging only works if you vent the gap between the motors so that the cold air in the gap is pushed away by the hot gases from the burning BP. If you don't vent, it will not work. Read Stein's Handbook. [/b]

1. 
   
   I wouldn't say that it will not work, but that it would be less reliable. The Estes Omega was gap staged without any venting.
   
   

   [*]The use of a booster motor with a delay ejection charge has been used many times in competition. It does not violate any safety policies provided you determine that the length of the delay is short enough so the the rocket is still moving in the original vertical direction when the second stage ignites.

   
   Bob, how does it not violate the competition rules when using a D12-0 as a single stage does violate them? IIRC, the booster motor was allowed for a while, but was eventually outlawed in competition. Looks like it would be both or none to me. I'm not asking to be argumentative, but just out of curiosity. I can't see how either motor could be used for the other purpose and be within the "manufacturer's intentions" part of the code. As for me personally, I actually like the idea of manipulating the rules as far as you can in competition as long as it's been tested out privately first.

 

[tbzep]

Gap Staging vs Taped:
TB: don't have any numbers handy but know from lots of year on the field lots of folks suffer unlit upper stages with the instructed cellophane taped method as discribed in most of the kit instructions. Reasons are again unclear some drop the booster while others retain it all the way to the ground.

With cellophane, it's easy for me to digest a failure mode when it melts the tape and drops away, but it's hard to fathom very many failures with the motors still taped together....unless somebody puts the sustainer in upside down. :eyepop:

 

[bobkrech]

Bob, how does it not violate the competition rules when using a D12-0 as a single stage does violate them? IIRC, the booster motor was allowed for a while, but was eventually outlawed in competition. Looks like it would be both or none to me. I'm not asking to be argumentative, but just out of curiosity. I can't see how either motor could be used for the other purpose and be within the "manufacturer's intentions" part of the code. As for me personally, I actually like the idea of manipulating the rules as far as you can in competition as long as it's been tested out privately first.

You can use a D12-0 in a saucer and it doesn't violate any safety codes.

The safety codes are for safety. You need to have a recovery system with your rocket. A -0 booster without a delay would initiate recovery at a velocity that is too high for a parachute to deploy safely if it would deploy at all without the extra gas generated by a conventional BP ejection charge.

Bob

 

[tbzep]

You can use a D12-0 in a saucer and it doesn't violate any safety codes.

The safety codes are for safety. You need to have a recovery system with your rocket. A -0 booster without a delay would initiate recovery at a velocity that is too high for a parachute to deploy safely if it would deploy at all without the extra gas generated by a conventional BP ejection charge.

Bob

I understand that, and have for decades. I even cited Centuri/Estes using the booster motors for single stage rockets in a "discussion" with Micro a year or two ago when he said a booster is never to be used as a single stage motor. It also was allowed in Superroc for a while, then outlawed because of MRSC #2, but it is still allowed in saucers.

Since the manufacturers specified a booster as a single stage motor in the saucer kits, why did they eventually disqualify the Superroc folks for doing the same thing? Their rockets were ejecting at near zero velocities, safely, just like saucers.

It seems to be a double standard in competition, allowing single stage motors (as per manufacturer labeling) to be used as boosters, but not allowing boosters as a single stage. Either, when used correctly, are safe and effective. Both, when used incorrectly, can lead to a disastrous flight with a delayed booster potentially causing power prangs. A booster for single stage purposes would at worst cause separation/stripping/zipper, so at least the return to earth wouldn't be at warp speed.

 

[HappyMeal]

I realize this is an old thread, but...

1) Estes, Centuri, and other rocket companies have sold single stage rockets that were to be flown with booster motors. (Centuri UFO, Estes Snitch & Cato just to mention a few) So there is plenty of precedence for using booster motors in single stage rockets not being a violation of the safety code.

2) Back in the day the NAR had an event where you were REQUIRED to use a booster motor to fly a single stage rocket. It really destroyed the creativity in that event (and Tom Hoelle's absolutely brilliant strategy) when this rule was eliminated.

3) The NARAM-22 flights were passed by checkin, and range safety. Motor choice was not questioned at the time, as using a B motor in an A event would have been. They were not DQed until 2 days AFTER the flights. The same models could have just as easily flown on an A10-3T instead of an A10-0T if this silly rule had been declared before flight instead of 2 days after the flying. There were multiple contestants DQed by this ruling (3-5?). Requests for reflights with "legal" motors were refused.

4) Those that actually filed the stupid NARAM-22 protest were allowed to be standing less than TWO FEET from their rockets when they were launched, a direct violation of the safety code that was totally ignored. Nothing was ever done about THIS clear rules violation.

 

[MarkII]

Very interesting angle, Happy Meal. But may I request that any further discussion be moved to a new thread? You are right - this thread is very old. I, for one, don't want to keep coming back to the war of words that Micro and I had two years ago; we have long since buried the hatchet.

 

[luke strawwalker]

Pretty sure he meant that the concept of gap staging will work for 1/2A through D engines, not a 1/2A lifting a D...

Still, an interesting concept. If I could get my hands on a few A10-0 or A8-0, it could make for a seriously awesome flight with a D on top. Lifting up 10-20 feet, dropping the booster, and then shooting off for the stars.


On a similar note, is the ejection charge from a motor with a standard delay sufficient to ignite a second stage, or the ejection charge different in motors intended to be used as boosters?
I would of course make sure that the rocket would still be traveling at a high enough velocity when the second stage lights, but it could make for an awesome effect, looking like an air-start.

At that point, it's almost like the "cold launch" methods used on Russian ICBMs (and later adopted by the Peacekeeper ICBM in the US-- adapted from the same "cold launch" technology used to blow SLBM's out of subs and above the surface where they then ignite their solid rocket motors).

The Soviets used to use a platform that the ICBM was mounted on, and a gas generator to pressurize the silo and physically blow the missile up and out of the silo. Once the missile and platform were safely above the silo surface, the platform would detach and ignite a pair of sideways-firing rocket motors that would push the platform to the side and out from under the missile, which would then fire up it's main propulsion rocket engines and take off... The addition of cold launch technology actually added a few hundred miles to the range of the missile, because the missile was already up and moving when the main rocket engines ignited, instead of firing up and coming up to pressure in the silo standing still, and having to accelerate from that standing start. Another benefit was that it caused FAR less damage to the silo, meaning that it could be reloaded faster with less repair...

Of course that's when they still used silos... all the new stuff is going road/rail mobile...

"Staging on the rod" is pretty close to this...

Later! OL JR

 

[luke strawwalker]

Black powder booster motors do not have ejection charges or even delays. A booster motor just contains the very hard slug of highly compressed propellant and a clay nozzle.

Although a single-stage motor that has a delay grain and an ejection charge can certainly be used in a booster stage, it cannot be used to ignite the upper stage motor. First of all, the upper stage, or sustainer, motor should be lit while the rocket is still carrying considerable momentum and speed from the boost; otherwise, the boost has been wasted, and the whole effort has been for naught. But this is exactly what would happen if you used a single-stage motor to light the sustainer. Remember that the whole purpose of the delay grain in a single-stage motor is to allow the rocket to coast to a stop at apogee, so that the ejection charge (which is designed specifically to generate gas to pressurize the airframe, which then ejects the recovery system) fires and pushes out the laundry when the rocket is nearly motionless. So having the booster motor burn a delay grain and allow the rocket to coast to a stop before igniting the sustainer would be counterproductive. It would be a total waste of the booster's energy; you would be better off not using a booster at all in that case.

I alluded above to the other big reason why you can't use a single-stage motor to ignite a sustainer: the ejection charge doesn't work that way. The purpose of the ejection charge is to produce gas (a great deal in a very short interval of time) and is not to produce flame. But flame is what you need to ignite the upper motor, and ejection charges are not well-suited for producing it. The ejection charge is set up to blow everything in front of it out of the rocket; it will do that to a sustainer just as well as it does to the recovery system. So when it fires, it will simply blow off the sustainer without igniting it.

There are plenty of multi-staged rockets that use single-stage motors in the booster, but these all use some other means (an electronic timer or flight computer) to ignite the upper stage. They do this after the booster burns out, while the entire rocket is still climbing at a good clip. Then the delay and ejection charge in the booster motor is used to deploy a recovery system for the booster stage, and it fires well after the booster has separated. This is how rockets that use composite propellant (APCP) motors are staged.

MarkII

Plus, by the time you coast to a stop, it's quite likely that your sustainer (upper stage) will be flipping over horizontal or in an unintended direction, perhaps even pointing DOWNWARD... IF the ejection charge manages to ignite the upper stage, you'll either have at best a "cruise missile" flight or at worst, a "re-entry flight" where the rocket comes down under thrust AND gravity! :y:

Don't want to be in the neighborhood when THAT is going on! OL JR

 

[luke strawwalker]

I realize that the rocket would have slowed down considerably after the delay. The idea would be to pick the shortest delay possible, so that it would only coast for a short period of time. Strap on boosters would be used to help it get enough initial speed so that it could still be going at a considerable clip by the end of the coast. Then, the 2nd stage would ignite, and go on its way.

The boost would not be wasted at all. The boost would have taken it up a fair ways, and given it a fair bit of speed. In fact, the sugar rocket to the moon group has a planned delay in between "stages" (really just grains) so as to let the rocket coast for a while, to keep the speed (and thus air resistance) down, so that they get higher.

Anywho, the point would be for an awesome flight show.

Still, I get your point of the difference between booster and sustainer "ejections" (or lack thereof.) Thanks for that info.

This requires careful modeling and simulations... it isn't to be left to the vagaries of BP propellant burn durations or time delays, or the ignition probabilities or delays caused by attempting to ignite an upper stage motor with an ejection charge. I'm not saying it CAN'T work, but the odds are against it, and the odds of something HIGHLY undesirable happening is high.

If one wants coast times between the burnout of the booster and ignition of the sustainer, use a staging timer and a regular ignitor to ensure that 1) the staging delay is accurately timed) and 2) the upper stage has a high probability of proper ignition...

A booster is inevitably heavier than a single-stage rocket, and using a single-stage engine in it and relying on even "the shortest delay possible" to ignite the upper stage is very risky... even if one say used a B4-2, it's quite possible the delay might be closer to three seconds than two, which can make all the difference on a heavy booster between "still moving upward at a good clip" and having stopped entirely and started to tailslide, or even arced over and pointed at the ground. In addition, as Mark said, the odds of ignition are not good... burning bits of BP are expelled with the ejection charge, but usually not as substantial as a booster motor at staging "propellant breakthrough". Another thing is, the ejection charge also sends out a blast of particles from the clay cap, which will likely help block the upper stage nozzle and propellant face from being hit by burning BP particles or flames capable of igniting the upper stage motor. Either way, you've got a staging failure. Even the more energetic blast of BP fragments from propellant burn-through in a booster motor occassionally fails to ignite the upper stage, even with NO clay cap or junk from it in the way...

Later! OL JR

 

[luke strawwalker]

As someone else has said before... "HOLY THREAD NECROMANCY, BATMAN!!" :y:

This thing is so old I forgot I'd even replied to it!!! Geez...

Interesting to see though that my mind works the same now as it did then... LOL (IE cold launch!)

Later! OL JR

PS. Yeah, we don't need no more peeing matches over this topic... LOL

 

[JStarStar]

I realize this is an old thread, but...

1) Estes, Centuri, and other rocket companies have sold single stage rockets that were to be flown with booster motors. (Centuri UFO, Estes Snitch & Cato just to mention a few) So there is plenty of precedence for using booster motors in single stage rockets not being a violation of the safety code.

2) Back in the day the NAR had an event where you were REQUIRED to use a booster motor to fly a single stage rocket. It really destroyed the creativity in that event (and Tom Hoelle's absolutely brilliant strategy) when this rule was eliminated.

3) The NARAM-22 flights were passed by checkin, and range safety. Motor choice was not questioned at the time, as using a B motor in an A event would have been. They were not DQed until 2 days AFTER the flights. The same models could have just as easily flown on an A10-3T instead of an A10-0T if this silly rule had been declared before flight instead of 2 days after the flying. There were multiple contestants DQed by this ruling (3-5?). Requests for reflights with "legal" motors were refused.

4) Those that actually filed the stupid NARAM-22 protest were allowed to be standing less than TWO FEET from their rockets when they were launched, a direct violation of the safety code that was totally ignored. Nothing was ever done about THIS clear rules violation.

I wasn't actually there, although I was less than five miles away (this was during my 20-some-year "retirement" from rocketry), but pretty much every reference I have ever seen to NARAM-22 seems to indicate it was a complete disaster on just about every level.