# Gap/Tube Staging..revisited

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#### Silverleaf

##### Well-Known Member
Howdy,

I just recieved my Quest Nike-K kit from the Ebay auction, and it got me to thinking about my Nike-Sandhawk project.

The current planned design is:

A single C or D Estes powered Nike booster, igniting a 2nd stage C or D Estes Sandhawk.

The Nike-Booster will have an inner-airframe tube to contain the ejection gases as much as possible - sealed on both ends by centering rings and will have a small side tube that contains the shock/kevlar chord recovery system.

The upper stage Sandhawk will have a small side stuffer-tube at the rear of the rocket that houses the Nike-Booster parachute till seperation happens. (See attached image)

This whole design is based on my desire to make a gap-staged Nike-Sandhawk a reality, without using any electronics.

Why?

I personally see no reason to pay out substansial amounts of money for electronics when normal staging methods may work. If this falls through, well maybe..lol

Honestly, as it stands, I have no experience with staging timers and the like, and don't want to mess with trying to figure out payload bays, and everytthing else for a fairly simple design. If this was a mid or hight power design... well I'll leave that to the experts. 8)

So... I've come across a few questions that I didn't find the answers to when I searched the archives on Gap-Staging. So I thought I'd ask here.

1) What is the maximum length in inches that a booster engine could be from the upper stage, and successfully ignite ?

In the archives, one person mentions success with a 6 inch gap...but is that the max?

Would I be wrong to assume that a D engine booster should have more lighting power than a C engine booster for such gap-staged events?

In regards to the vent hole, I have 3 questions:

A) I understand that a vent hole needs to be added somewhere between the booster and upper stage engine - but is there a minimum distance that the vent hole should be above the booster?

B) Will a single Hole Punched hole be sufficient, or would 4 holes equally spaced round the airframe be better?

C) In reference to my design, the inner airframe is sealed, so a vent hole placed in this inner-tube might not function properly, in this case, should I make this venthole extend to AND through the outer airframe for proper pressure balance?

Sorry for all the questions..

#### Missileman

##### Well-Known Member
If I am figuring what you are doing with the chute correctly, I would be concerned about pullimg the deploying chute past a freshly lit motor?
As for the vent holes, they should be as close as possible to the motor being lit. It is the dead air space that will stop hot chunks of buring BP from getting to the motor.
A simple low cost electrical means of staging is $2 microswitch and battery. Airdrag or lower stage motor separates stages which closes the microswitch completing the circuit and firing the ignitor for the upper stage motor. Caution must be taken not to connect battery until on the pad so no accidental motor ignition occurs during handling. Best of luck #### Silverleaf ##### Well-Known Member Missile, Well, originally, I was going to wrap the chute in a piece of flame-retardent kevlar, but after a conversation on mylar chutes, it seems mylar should hold up to the flame. If you think a kevlar shield protector would work better, I can always add it back into the design. As to the vent holes - as close to the upper-stage as possible. Cool..thanks ! #### shockwaveriderz ##### Well-Known Member silverleaf: consider doing a review by searching on "gap staging" at groups.google.com on rec.models rockets..... One major point they make is to use an upper stage engine with a large diameter nozzle as opposed to one with a smaller nozzle so the ejection charge particulate can get into the upper stage nozzle... Secondly they seem to indicate that 2 opposing 1/4" holes would be sufficient I would use techniques similar to what the FAI flyers use: 1. fill a small diameter paper straw with bp........ this is stuck up into the motor nozzle of the upper stage engine..i believe this is called black match? https://www.unitednuclear.com/crossmatch.htm 2. use a fuse...... with a known timing.... 3. make your own fuse from a saltpeter/hot water mixture and the roll in bp and 100% cotton cord and place inside a paper tube and use as in #1... see groups.google.com and rec.pyrotechnics....... 4. get some or make some "flash paper" and stick in the upper stage nozzle to enhance ignition Don't want to sound pessimistic here but if you rely 100% on gap staging relying on just the exhaust gases without using something from above, gap staging will probably fail you at some time.... From RMR : "These are vent holes designed to allow hot gasses to escape and prevent premature staging. Here's the theory. As the booster motor burns, hot gases are released from the top end of the booster. These hot gases are not suficient to light the upper stage. However, they can build up enough pressure to pop the booster off too early, hence the vent holes. Shortly after the hot gasses start to be released, hot particulate matter starts being thrown up from the booster to the sustainer motor. These hot particles are what cause the sustainer motor to ignite." hope this helps #### sandman ##### Well-Known Member Ya know....with all the talk on all the forums, not just this one, about on board ejection electronics, black powder or pyrodex, I was wondering why I've never heard of someone using a "low tech" method. A mousetrap type ejection system with the stage seperation tripping an internal spring loaded arrangement just for the booster. A spring and a catch may wind up being lighter than electronics and a battery. Anybody ever tried it? I think the old vashon and Estes Cold Power motors may have used something like that...Not sure really. Anyone?? sandman #### Micromeister ##### Micro Craftman/ClusterNut TRF Lifetime Supporter TRF Supporter I think your right sandman! I know i've seen a spring loaded seperation system in the past.. I've only used springs to seperate glider pods and such. It should work Silverleaf: Hasn't it been settled that there never was a Nike-Sandhawk? I seem to remember reading somewhere..maybe in one of G Harry Stine's old books " sounding rockets" maybe.... really foggy, I seem to recall this configuration while thought about never came to pass because of the introduction of the more powerful Terrier booster???? I've always like the Sandhawk, a Nike-Sandhawk would be a neat sport model. Maybe I'll add it the my 1/36.8715 scale 10.5mm set #### powderburner ##### Well-Known Member The idea of mechanical devices is interesting, but how do you ignite an upper stage motor with one? #### sandman ##### Well-Known Member but how do you ignite an upper stage motor with one? LOL!...maybe I misspoke. This might work but only for BP staging. Here is my senario. 1. First stage BP booster fires. 2. At burnout The BP booster motor would ignite the BP upper stage motor. 3. After the upper stage ignite it seperates and the seperation releases the spring catch. 4 . The spring pushes out the recovery device (chute, streamer or just break-up) for the booster. This would be for say a Terrier/Sandhawk booster. Otherwise the Terrier booster with the large fins and the transition would still be stable. It would need a recovery devise or it would come in like a lawn dart. The spring loaded devise would only be for booster recovery deployment. sandman #### Micromeister ##### Micro Craftman/ClusterNut TRF Lifetime Supporter TRF Supporter Yeap! That's what I thought you were talking about sandman, recovery deployment for a gap staged booster. Spring load seperation would also aid in seperation of the stages as well as deployment, which is sometimes a problem with gap staged models. Activated by an upper stage burn string or pull out pin. #### prowlerguy ##### Well-Known Member Originally posted by sandman Ya know....with all the talk on all the forums, not just this one, about on board ejection electronics, black powder or pyrodex, I was wondering why I've never heard of someone using a "low tech" method. A mousetrap type ejection system with the stage seperation tripping an internal spring loaded arrangement just for the booster. A spring and a catch may wind up being lighter than electronics and a battery. Anybody ever tried it? I think the old vashon and Estes Cold Power motors may have used something like that...Not sure really. Anyone?? sandman I posted this in another thread, but I think it is similar to what you are talking about. Of course, you may need to change orientation, but the no BP, no battery, no electronics advantage for such a system may make it worth a try. https://www.rocketryforum.com/showthread.php?s=&postid=77301#post77301 #### shockwaveriderz ##### Well-Known Member silver: consider using a mercury switch....perhaps a G-switch might work here too... at booster engine burnout the mercury switch/battery ignites the igniter in the upper stage and it fires and separates.... you could then use a motor in the booster that has a delay and ejection charge to push out the chute after the upper stage has already fired and moved away from the falling booster .... just don't arm the circuit until the model is already on the pad..... I found this on RMR: You don't need a flashbulb/thermalite fuse to do this...a large enough cap will fire a ematch To do electronic staging you will need the following: 1. A flash bulb (see stuff following this section) 2. Thermalite fuse (fast) 3. A 50-100 uf capacitor (see below) 4. A mercury switch (see below) The theory goes like this. When your 1st stage engine burns out, the rocket experiences negative Gs due to drag. If you place a mercury switch in the stage coupler, the mercury will jump to the top of the switch at burnout. Thus, you want to put the contacts at the top. Put the mercury switch between one lead of the capacitor and one lead of the flash bulb. Connect the other lead of the flash bulb directly to the capacitory. Insert one end of the fuse in the upper stage engine and tape the other end to the flash bulb in the stage coupler. Just prior to launch (like when the rocket is sitting on the pad) put a charge across the capacitor (6 volts worked fine for me, 12 volts is even better). Now, when the first stage burns out, the mercury will move to the top of the mercury switch completing the cicuit between the flash bulb and the capacitor. The flash bulb will fire igniting the fuse and thus the upper stage. There are a couple of things you might want to consider in your implementation. One is a connector in the side of the stage coupler for charging. Use something like an audio jack. Another thing is an arming switch. Leave it off when charging and turn it on just before launch. Last is a another arming switch that is activated by motion of the rocket. This might be something like a ribbon between two contacts that is withdrawn as the rocket leaves the pad. This second arming switch is to prevent the second stage from igniting in the event the rocket is accidentally knocked over while it is still on the pad. You can get SUPER Capacitors : https://www.cooperet.com/products_supercapacitors.asp Mercury glass/metal bulb tilt switches: https://www.mouser.com/catalog/617/963.pdf #### Habu ##### Well-Known Member Originally posted by Silverleaf Howdy, I just recieved my Quest Nike-K kit from the Ebay auction, and it got me to thinking about my Nike-Sandhawk project. The current planned design is: A single C or D Estes powered Nike booster, igniting a 2nd stage C or D Estes Sandhawk. The Nike-Booster will have an inner-airframe tube to contain the ejection gases as much as possible - sealed on both ends by centering rings and will have a small side tube that contains the shock/kevlar chord recovery system. I'm actually in the middle of a similar project with a couple of Quest Nike-K's that I picked up at the HL 50% off feeding frenzy. Estes powered 24mm Nike booster to 18mm sustainer. I hadn't planned on any recovery system for the booster, which appears to be unstable according to SpaceCAD. But I'll pay close attention to Sandman and watch for a booster core sample. I'll be very interested to see how yours works out, Silverleaf. #### Silverleaf ##### Well-Known Member Guys many thanks for all of the tips, hints and advice. Wow, so much advice - this is EXACTLY why TRF is the best place online for our hobby - bar none. *wink* I'm totally unsure about trying any BP, electronics, or other combinations other than gap-staging at this point. But I do understand that there is an inherent risk with a larger gap than say 6 inches between motors. So, i'm going to look at some of these suggestions and see what is optimal for me and the tiny wallet. One major point they make is to use an upper stage engine with a large diameter nozzle as opposed to one with a smaller nozzle so the ejection charge particulate can get into the upper stage nozzle... So, a D or E upper engine would be a "safer" bet than a C for possible ignition. Dang, didn't think of that, ok..so it looks like its become a Double D - or *gulp* Double E rocket..tasty ! fill a small diameter paper straw with bp........ this is stuck up into the motor nozzle of the upper stage engine..i believe this is called black match? Sweet link. 8) This sounds doable. So I take it that no ejection charge/electronics is needed with this black match style fuse - that the ejection gases "should" ignite it. Correct ? Hasn't it been settled that there never was a Nike-Sandhawk? It was a question that many thought COULD have happened - given the style of Nike/Sandhawk configurations. No official word was brought forth on the subject from Sandia until a few weeks ago. During my second email communication with Richard Hay at Sandia National Laboratories, he made an official proposal from 1967 available to me, which shows the Nike-Sandhawk was proposed, but never flown. My other thread on "Just in case..." in the Techniques section has a note on this very subject. See the Scale Data section on my site for the info: https://scale-rocketry.tripod.com/index.htm Shock, Wow, excellent stuff there on a mercury switch. I've no clue about these, so a ton of research would need to be done. Do you know of anyone whom uses these mercury switches that might have an tutorial showing how to create them ? Habu, Right now, I'm staying with the original drawing attached above as my recovery system. IF I can solve the gap-staging problem, I see no reason to change what I "believe" is a safe method of recovering the booster. Missile brought up a valid point as the 1st reply in this thread - that the chute might be damaged by the motor. I'm still leaning towards my original design of a Mylar chute rolled inside a Kevlar Heat Shield to protect it for this very reason. In the long run, this simple "addition" is something I will do, simply to add one more precaution in the design. I've got a nice digital camera on the way ... again ...so we'll see if it works for up-close images. Once thats solved, then I can start documenting my work on all of my projects including this one. 8) Thanks again guys - this is a fantastic read ! Cheers, #### shockwaveriderz ##### Well-Known Member Sweet link. 8) This sounds doable. So I take it that no ejection charge/electronics is needed with this black match style fuse - that the ejection gases "should" ignite it. Correct ? Shock, Wow, excellent stuff there on a mercury switch. I've no clue about these, so a ton of research would need to be done. Do you know of anyone whom uses these mercury switches that might have an tutorial showing how to create them ? Yes Silverleaf, the ejection charge particulate will ignite the BP/flash paper... Back in the mid-80's I was playing around with mercury switch staging technique with minimum diameter estes Bp motors and it does work very well... For more information and howto go here: https://nar.org/backissues.html Pay$0.75 cents for the following :
American Spacemodeling Magazine (get a photocopy of the article)
Dec 1984 12/84 Vol.26 N10
pg 5-8

Technical Notes on Mercury Switch Staging
by William Dye

That is where I learned the technique along with electrical schematics

I will dust off (from memory) my circuit setup and post it later

#### Missileman

##### Well-Known Member
Ok now I am a bit confused.
I can see how BP in a small tube as a fuse would work as BP lights easily but How do you get the BP to stay in the tube/straw?
It would seem that taping the end would defeat the purpose and under thrust the open end would face aft.

#### shockwaveriderz

##### Well-Known Member
blackmatch is a BP fuse that is enclose with a paper tube....it is not taped on either end......

or if you just filled a paper tube with bp powder, you can plug the neds with flash paper....the heat from the ejection charge particulates will ignite the flash paper which in turn ignites the BP....

#### teflonrocketry1

##### Well-Known Member
If you look on page 172 of the Sixth Edition of G. Harry Stines Handbook of Model Rocketry it says: "So I vented the lower stage body tube by punching two 1/4-inch diameter holes on opposite sides of the tube just below where the nozzle of the upper stage motor would be."..." I flew over 100 two-staged flights with 100 percent sucess in the upper stage ignition. Motors were separted by as much as 12 inches."

In the second edition of Model Rocket Design and Construction by Tim Van Milligan on page 120 "If the engines in your design are separated by a short distance, less than 12.7 cm (5"), you can still get reliable ignition of the upper stage motor if you alllow some of the gases in front of the lower booster engine to vent to the outside air."

In The Art of Scale Model Rocketry by Peter Alway (1994) on page 35 " I have sucessfully staged Aerobee models across 6" air gaps with no special ignition system with 90% reliability."

Bruce S. Levison, NAR #69055

#### Zippy

This is such an interesting thread I thought I would throw in another $0.02. Here's a cutaway diagram of how I built a gap staged booster. It's had a few flights now and ignited the second stage and seperated flawlessly everytime. One of only two problems I've had with it is erosion of the uncoated balsa around the vents. This area definatly needs to be treated somehow (epoxy maybe) to slow that down. You'll notice the vents are quite large yet never a problem with second stage ignition or seperation. The other problem I've had is it doesn't allways want to tumble, sometimes it tries to glide for awhile and sometimes it just comes in tail first. It actually hit a concrete sidewalk last time but it's still repairable. Not a problem if your using a parachute. Scorpion Booster Cutaway The sides of the booster are allways coated with a light grey film after flying. Most of it just wipes off. #### prowlerguy ##### Well-Known Member Why not use a few feet of kevlar attached to the apex of your chute to pull it out? The distance should negate the need to shield your parachute, making packing simpler. The thread wouldn't weigh enough to hurt the parachute performance once inflated, I would think. #### shockwaveriderz ##### Well-Known Member zippy: https://www.mcmaster.com sells both an aluminum and a stainless steel adhesive backed super thin "tape"...on the order of 2-3 mils, .002-.003..... do a search on stainless steel tape #### Zippy ##### Well-Known Member shockie B) I actually have something like that laying around somewhere. I should have used it when I built the thing but I never thought about it. Next time it's up on the blocks I'll work it in somehow. #### shockwaveriderz ##### Well-Known Member #### Silverleaf ##### Well-Known Member My apologies for missing this thread and all the replies. Dang, you guys are a veritable encyclopedia of info..*vbs* Shockie, Got your email my friend, many thanks for all of the details and posting a new thread. I'll be looking at this closely to see if i can figure out all of the details and weigh how beneficial chad staging is. First up is saving for Sandman's project, then its onto the Nike-Sandhawk. 8) Cheers, #### qMaxx ##### Well-Known Member Just to add my$0.02...I have built several gap-staged models and flown all of them with a 100% successful upper stage igniton rate. This includes 8 flights on two versions of staged/clustered Fat Boys (4x18mm booster to a single D12 upper, and a 3x18mmm and single D12 booster to a single D12 upper - plans were published in a '98 or '99 issue of Sport Rocketry - need to dig out my copies and check), a scale Aeolus with a single 18mm/6x13mm booster to a D12 upper, and a scale Super Chief II with single 18mm motors in both stages.

The Aeolus has the longest gap - about 8" or so.

There was an article in an old issue of SpRocketry regarding recovery of gap-staged boosters. I think it was written by Buzz Nau, but I'm not sure. I know it was an issue or two before or after my staged/clustered Fat Boy plans showed up.