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Model Forum / General / Rockets / September 2004Protecting a lower stage from 2nd stage ignition
The one rocket I'm working on is a 2 stage. One of the things I'm concerned about is protecting the lower stage from the heat of ignition, I don't need it frying the lower stage and couplings. I was told that it shouldn't be a concern as the two stages should blow right apart......but by that same way of thinking we can dispense with blast deflectors on launchpads too. Right now I'm looking to attach a removeable metal plate, such as a fender washer, on the bulkhead below the 2nd stage motor. Likely I'll augment that with some Nomex in between and pack as much wadding as possible above. That still leaves the coupling vulnerable in my mind. As I haven't yet figured out a means of providing protection for it (leastwise a workable idea) I'm thinking of making it removeable/not gluing it in place. If it gets burned up, pull it out and replace it. If it goes along for the ride with the 2 stage, replace it as needed there too. BTW, the idea of separation through drag to protect the lower stage isn't an option in this rocket. The staging timer is in the lower stage so the two must remain joined until ignition. Any other thoughts? Chuck, L1 NAR#82306 What size rocket is this, and what size motors will you be using? How is your interstage coupler constructed? On mine, the interstage coupler is usually made from a regular coupler with a bulkhead in the aft end. I reinforce the tube with a bit of fiberglass, applied to the interior. Never had one get overly burnt yet. I mean, yeah it gets pretty sooty on the inside but you have to expect that. No real damage though. The bigger problem is damage to the exterior finish of the booster. Even so, this is usually just a little cosmetic damage. Mostly soot, but sometimes the paint can get scorched a bit -- especially if you've got a White Lightning motor in the sustainer. Only real way to avoid this is to blow the booster off before igniting the sustainer. >What size rocket is this, and what size motors will you be using? How is your interstage coupler constructed? 38mm minimum diameter. Booster is set up for 38mm motors and the 2nd stage 29mm (so there's room for the coupler slide in). All relevent parts are LOC's >On mine, the interstage coupler is usually made from a regular coupler with a bulkhead in the aft end. I reinforce the tube with a bit of fiberglass, applied to the interior. Never had one get overly burnt yet. I mean, yeah it gets pretty sooty on the inside but you have to expect that. No real damage though. That's certainly a better idea than my trying to line the thing with metal. But then I haven't started playing with fiberglass just yet either and lack the insights. Guess a bit of that fireblanket I have here is about to get a good home :-) >The bigger problem is damage to the exterior finish of the booster. Even so, this is usually just a little cosmetic damage. Mostly soot, but sometimes the paint can get scorched a bit -- especially if you've got a White Lightning motor in the sustainer. Only real way to avoid this is to blow the booster off before igniting the sustainer. External damage seems a lesser concern since by then the stages are being blown apart by the exhaust, but the insights are noted. I guess the next beastie will be designed to allow for separation and then ignition. I suppose a single stage with airstarts would also fulfill the learning curve here too. This one is just too teeny tiny to squeeze everything in, which is one of the reasons the staging electronics are in the booster. First attempts are rarely elegant. Chuck > >What size rocket is this, and what size motors will you be using? How is your interstage coupler constructed? > > > 38mm minimum diameter. Booster is set up for 38mm motors and the 2nd > stage 29mm (so there's room for the coupler slide in). All relevent > parts are LOC's Is it not at all possible to house the staging electronics in the upper stage then? How about if you made the sustainer 'male', so the rear of the rocket is coupler, that might make it possible to run an ignition wire from a timer mounted above the motor. Of course this might get in the way of motor ejection, but I'm guessing that with a 38mm min-dia booster and 29/38 second stage this thing will be going a looooong way (dual deployment). Also, if you get accidental drag sep, and your electronics are in the sustainer, its not such a problem. If they're in the booster, it might be (but then again your sustainer will probably have electronic deployment).... Just my thoughs... -- Niall Oswald ========= UKRA 1345 L0 EARS 1151 MARS CURS http://www.cranfield.ac.uk/socs/rocket http://www.oswald.ndo.co.uk/earsjuly "When finished this kit stands about 17 inches tall and is highly detailed. When crashed like a lawn harpoon, it stands somewhat shorter and is still highly detailed." -Saturn 1B eBay listing >Is it not at all possible to house the staging electronics in the upper stage then? How about if you made the sustainer 'male', so the rear of the rocket is coupler, that might make it possible to run an ignition wire from a timer mounted above the motor. Of course this might get in the way of motor ejection, but I'm guessing that with a 38mm min-dia booster and 29/38 second stage this thing will be going a looooong way (dual deployment). The basic idea for this rocket was to point towards an altitude record, and something else similar. So yes, it's supposed to go a loooong way. However I've downgraded this one to the prototype I'll test things in, the sims say this one won't get anywhere near the altitude I need. Too heavy and clunky. Given the size of the timing electronics and body tube's diameter I had three choices for where to place things. Mount it in the electronics package with the altimeter, which I saw as a potential for a bad connection where the rocket separates and would need a break-away connection. Place it in the main body, where it would block the ejection gases from the motor being used as a redundancy for initial deployment. The third idea was to place it in the booster, where it gets a straight run to the igniter and lightens the upper stage abit more. Of the three that seemed the best way to go with present equiptment and skills. >Also, if you get accidental drag sep, and your electronics are in the sustainer, its not such a problem. If they're in the booster, it might be (but then again your sustainer will probably have electronic deployment).... > >Just my thoughts... >-- >Niall Oswald Drag separation is the only thing I can't (yet) fully account for. The timer will be set for firing the next motor before the booster fully burns out, so that it will be coming up to power when burnout occurs, eliminating any lapse that might cause a separation. However the sequence of events if there's a 2nd stage misfire would be to make sure the booster motor is powerful enough to carry the whole rocket to where the altimeter both arms and exceeds the second deployment altitude. Also the booster's recovery system, which is the ejection charge on the motor, would deploy to slow down the decent. If things separate at the payload section things are yet tethered together by the shock cord (kevlar). If the stages separate, then it should (hopefully) still reach an apogee where the altimeter can take over and deploy the main. Good thoughts you have, thanks! Chuck > The basic idea for this rocket was to point towards an altitude > record, and something else similar. So yes, it's supposed to go a > loooong way. However I've downgraded this one to the prototype I'll test > things in, the sims say this one won't get anywhere near the altitude I > need. Too heavy and clunky. If you're going for an altitude record, remember that drag increases with the square of the velocity. So 2x velocity produces 4x drag. A two stage rocket with the sustainer ignited at booster burnout gives maximum sustainer velocity, but because of drag the resultant altitude is lower. Maximum altitude can be achieved by separating the booster at burn-out, and then allowing the sustainer to coast up and reduce speed before igniting its motor. But if you let it coast too long, ..... :( I know from these posts that requires re-design, so now you can play with the prototype and various options. How about doing a series of sims and you may discover that even with the weight of a small timer (PerfectFlight, etc) in the sustainer, the final altitude will still be greater. For these kind of calculations for my 2-stage, I wouldn't trade RockSim for anything. The extra time to sim flights has prevented me from doing bad things to the rocket. :) It's worth the extra time even for smaller motor rockets. Larry Lobdell Jr. > If you're going for an altitude record, remember that drag increases with the square of the velocity. So 2x velocity produces 4x drag. A two stage rocket with the sustainer ignited at booster burnout gives maximum sustainer velocity, but because of drag the resultant altitude is lower. Been procrastinating and haven't gotten around to answering this one. Hmmm, I know kenetic energy is the square, but isn't drag the cube? Doubling the velocity does quadruple the energy, but you're also dealing with twice as much air impacting on the rocket to produce drag: (2 x 2) x 2 = 8. I recall that from that ancient Estes booklet on altitude prediction (hope to unearth it again when we assault, er....clean, the attic, quite the cutting edge data for the time) > Maximum altitude can be achieved by separating the booster at burn-out, and then allowing the sustainer to coast up and reduce speed before igniting its motor. But if you let it coast too long, ..... :( Interesting. When the project was begun that was one of the discussions, keeping velocity/drag lower for greater total altitude. The rough calcs I did said that was iffy and the idea was tabled. Might need to be brought to the fore again as we work out the bugs on the prototype. >I know from these posts that requires re-design, so now you can play with the prototype and various options. There's a redign in process to correct some logistical bugs, but the basic design will remain intact. There was an on-line program that would allow for varying the upper stage firing time to experiment with the idea, right handly it was, but it's non-exanct now. Guess I do it the old fashioned way. Darn, I have to fly more rockets, oh darn! ;-) >How about doing a series of sims and you may discover that even with the weight of a small timer (PerfectFlight, etc) in the sustainer, the final altitude will still be greater. For these kind of calculations for my 2-stage, I wouldn't trade RockSim for anything. The extra time to sim flights has prevented me from doing bad things to the rocket. :) It's worth the extra time even for smaller motor rockets. >Larry Lobdell Jr. At the moment monetary constraints require I run with what I got, and what I got was acquired through what was found with my limited knowledge of who offers what. But these all are ideas that are being considered, whether thought up independantly or found here. Thanks! Chuck Take a look at ceramic putty, part number 7551A23 from McMaster-Carr (http://mcmaster.com). I've used it to protect the aft end of rockets. "Withstands continuous temperatures up to 2300° F" Dean << 38mm minimum diameter. Booster is set up for 38mm motors and the 2nd stage 29mm (so there's room for the coupler slide in). All relevent parts are LOC's I don't think you'll have much of a problem. I've used un-glassed LOC coupler tubes for interstages before, they can wear out after a while but with 29mm in the sustainer you'll get plenty of use out of it before then. << But then I haven't started playing with fiberglass just yet either and lack the insights.>> The main reason I started glassing them was to get more rigidity on part of the coupler that fits between the fins of the sustainer. (The coupler is slotted for this.) << Guess a bit of that fireblanket I have here is about to get a good home >> That'll work. > Any other thoughts? I've heard of using two e-matches in series - one (dipped as needed) in the upper stage motor, and one firing a little BP "baggie" charge between the stages... this pops the stages apart at the same moment as the upper stage pyrogen initiates, which allows them to separate before the upper stage actually gets properly ignited. -dave w > > Any other thoughts? What I do is line the coupler with aluminum tape. Works great. -- Erik Chuck, First, the staging electronics belong in the sustainer. Booster recovery electronics belong in the interstage coupler. Allows drag separation for staging, which can be desirable. But too late for that. To protect the coupler, use either the ceramic putty from McMaster/Carr, or smear the inside with Dow/Corning Hi-temp silicone rubber (the orange stuff). Hell of a lot lighter than metal, and it will take the heat. Available at any auto parts store for a couple of bucks. You can also pack the coupler with dog barf (cellulose insulation). A little soot in the coupler won't kill it. In the event that a drag-sep kills the sustainer, when you re-build it, install the staging electronics in the sustainer, and run the wires down along side the motor mount through a 1/8" brass tube conduit. Then you can twist the wires to the igniter, wrap them with a bit of tape, and stuff them in along side the motor mount. That way only the igniter gets roasted. Use a Dean's connector to attach the wires to the electronics bay. When the apogee charge goes off, it pulls apart easily. Just a bit of masking tape will prevent it from pulling apart under booster G's. Consider getting a G-Wiz Deluxe for it. Handles staging very well, and will do dual-deployment recovery. It will also perform recovery in the event of non-ignition of the sustainer motor. (Everyone is afraid of the G-Wiz, because of the recommended dual-battery set-up. One 9 volt for the pyro channel, and one of those little 1/3N, 12 volt lighter batteries for the computer works very well, and doesn't weigh anything. Just modify the battery holder with a spring on each end, and watch the polarity when you install the battery. Prevents reset under booster acceleration.) I use a magnetic apogee detector in my interstage coupler for booster recovery, and install a long delay in the booster motor for back-up. Works well, and prevents a booster chute strip. 8^) (BTW, I have no interest in the G-Wiz Partners, other than that of a satisfied customer.)  SignatureJames L. Marino SAS, LUNAR, TCC, AEROPAC, NAR #75764 L3 TRA #9489 L3 "Ban light pollution, not rocket motors." > The one rocket I'm working on is a 2 stage. One of the things I'm > concerned about is protecting the lower stage from the heat of ignition, [quoted text clipped - 17 lines] > Chuck, L1 > NAR#82306 "James L. Marino" <jmar1371@DONTSPAMhotmail.com> wrote in message news:Vgi0d.18421 > in along side the motor mount. That way only the igniter gets roasted. Use > a Dean's connector to attach the wires to the electronics bay. When the > apogee charge goes off, it pulls apart easily. Just a bit of masking tape > will prevent it from pulling apart under booster G's. Lots of good information! One question: What is a Dean's connector, and where can we find them? I've tried searching a couple of electronics catalogs without success. > "James L. Marino" <jmar1371@DONTSPAMhotmail.com> wrote in message > news:Vgi0d.18421 [quoted text clipped - 8 lines] > where can we find them? > I've tried searching a couple of electronics catalogs without success. I think they're the high-current low-insertion-force connectors used on motors and batteries in electric-powered RC models... these may be sought at hobby shops that have a selection of RC-related stuff. -dave w >> "James L. Marino" <jmar1371@DONTSPAMhotmail.com> wrote in message >> news:Vgi0d.18421 [quoted text clipped - 14 lines] > >-dave w Would that be the connector on those 9.6v batteries used in RC Cars? Those are not even close to ZIF (Zero Insertion Force) >>> "James L. Marino" <jmar1371@DONTSPAMhotmail.com> wrote in message >>> news:Vgi0d.18421 [quoted text clipped - 19 lines] > Would that be the connector on those 9.6v batteries used in RC Cars? > Those are not even close to ZIF (Zero Insertion Force) Deans are NOT ZIF. They are designed to hold in high vibration environments. I used them as power connectors on my altimeter. John >>>> "James L. Marino" <jmar1371@DONTSPAMhotmail.com> wrote in message >>>> news:Vgi0d.18421 [quoted text clipped - 24 lines] > >John Do you have a link or a Digikey part#? Sorry for the delay...been cleaning up after Ivan. Had to pull a 40 hour shift at the radio station from 4:00 AM Wednesday till Thursday night when it quieted down. It took my wife and me a day and a half to clean up around my mom's house (she was without power for 72 hours) and the other half day to clean up around our house. Luckily, no damage. http://www2.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=Deans+connectors&FVPROFIL=++ The =++ should be included in the link. There are other online vendors that carry them, and the company (W.S. Deans) has a website, too. http://www.wsdeans.com John >>>>> "James L. Marino" <jmar1371@DONTSPAMhotmail.com> wrote in message >>>>> news:Vgi0d.18421 [quoted text clipped - 28 lines] > > Do you have a link or a Digikey part#? Thanks John. Hope everyone down there recovers quickly. Phil >Sorry for the delay...been cleaning up after Ivan. Had to pull a 40 hour >shift at the radio station from 4:00 AM Wednesday till Thursday night when [quoted text clipped - 45 lines] >> >> Do you have a link or a Digikey part#? snip Glad to hear you're all ok. : ) Randy Phil and Randy, Thanks for the kind thoughts. If you can, say a prayer for the folks in Southwest Alabama and Northwest Florida. The headlines from the Pensacola newspaper say it all..."WE NEED HELP". There are a few rocketeers that fly with our club that we have not heard from...but there is no phone service in those areas yet. Cellular service is so congested that you frequently get overload messages when you try to call. Power may not be restored for about one month for some residents. Our area was VERY lucky. John > Phil and Randy, > [quoted text clipped - 5 lines] > overload messages when you try to call. Power may not be restored for about > one month for some residents. Amatuer radio operators can send radiograms (free) if you need to contact somewone. I know the hams there are working overtime providing emergency communication, so if you do send one, just have it be brief 73 SignatureTater President of MARS Club (NAR #660) www.mars-rocketry.com KC9ESF NAR #79654 L1 AMA #747769 EAA #703312 remove spam spelled backwards to reply Yep, I'm aware (KC4RLL). The hams are very busy, another club member was able to reach them by cell phone. The are OK, had some damage, but are well. John >> Phil and Randy, >> [quoted text clipped - 16 lines] > > 73 > If you can, say a prayer for the folks in > Southwest Alabama and Northwest Florida. Been doing that. ; ) Randy << If you can, say a prayer for the folks in Southwest Alabama and Northwest Florida. The headlines from the Pensacola newspaper say it all..."WE NEED HELP". >> Three hurricanes in a row, and the third hits the same area _twice_. Did someone stick a giant "kick me" sign on Florida's back or what?? > Three hurricanes in a row, and the third hits the same area _twice_. Did > someone stick a giant "kick me" sign on Florida's back or what?? Maybe, God is following the religious thread. Moses saw his hinder parts in a cloud on the mountain. Could it be that He's traveling around in that hurricane? There are those that wanted proof, well how many times has a hurricane come around twice? MAYBE... His first name is Ivan. ; ) Randy (Sorry, I couldn't resist.) ><< If you can, say a prayer for the folks in Southwest Alabama and Northwest >Florida. The headlines from the Pensacola newspaper say it all..."WE NEED >HELP". >> > >Three hurricanes in a row, and the third hits the same area _twice_. Did >someone stick a giant "kick me" sign on Florida's back or what?? http://packetstormsecurity.org/unix-humor/GODvsBUSH.gif Eldred Signaturehttp://www.umich.edu/~epickett Screamers League IICC League GPLRank -6.0 MoGPL rank +267.80 Ch.Rank +52.58 MoC +741.71 Hist. +82.34 MoH:na N2k3 rank:in progress Slayer Spektera lvl 79 assassin Slayer Spectral_K lvl 44 Necro US East > There are other online vendors that carry them, and the company (W.S. Deans) > has a website, too. > > http://www.wsdeans.com I've used Deans plugs for many years now, and use them for the charge / fire connections on my relay launch systems. But with any connector, be sure to note the rated current capacity. Deans doesn't list their numbers on their web site. One really nice poer connector is the Anderson PowerPole, sold for RC use under the Sermos brand name. These connectors are much larger, and stackable so you can build whatever number of poles you need. Self cleaning, no exposed pins to short, they are gender less, so you rotate one pin 90 degrees to prevent plugging in the wrong way. Small RC ones are rated at 15A. I've seen bigger versions in computer UPS systems that are rated at several hundred amps. Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle: http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org 26-October, 2001: A day that will live in infamy Support Freedom: http://www.indefenseoffreedom.org/ ... One nation under survielence, divisive, with liberty and justice for none. I also use Molex connectors for my launch controllers: http://www.molex.com but Radio Scrap, er, Shack has started to drop all pieces parts...go figure. John >> There are other online vendors that carry them, and the company (W.S. >> Deans) [quoted text clipped - 30 lines] > ... One nation under survielence, divisive, with liberty and justice for > none. > I also use Molex connectors for my launch controllers: http://www.molex.com > but Radio Scrap, er, Shack has started to drop all pieces parts...go figure. No loss. We just got our first Fry's in the Chicago area. Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle: http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org 26-October, 2001: A day that will live in infamy Support Freedom: http://www.indefenseoffreedom.org/ ... One nation under survielence, divisive, with liberty and justice for none. > One really nice power connector is the Anderson PowerPole, sold for RC use > under the Sermos brand name. These connectors are much larger, and stackable > so you can build whatever number of poles you need. Self cleaning, no > exposed pins to short, they are gender less, so you rotate one pin 90 > degrees to prevent plugging in the wrong way. Small RC ones are rated at > 15A. also used by amatuer radio operators (like me) for emergency equipment. All our battery systems use them, and am re-building launch controllers for them too (banana plugs just DON'T work) > I've seen bigger versions in computer UPS systems that are rated at > several hundred amps. also used in electric forklifts. big suckers SignatureTater President of MARS Club (NAR #660) www.mars-rocketry.com KC9ESF NAR #79654 L1 AMA #747769 EAA #703312 remove spam spelled backwards to reply > also used by amatuer radio operators (like me) for emergency equipment. All > our battery systems use them, and am re-building launch controllers for them > too (banana plugs just DON'T work) Banana plugs work fine for clips. I've never tried them any where else. >> I've seen bigger versions in computer UPS systems that are rated at >> several hundred amps. > > also used in electric forklifts. big suckers Yea, our warehouse forklifts use them too. Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle: http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org 26-October, 2001: A day that will live in infamy Support Freedom: http://www.indefenseoffreedom.org/ ... One nation under survielence, divisive, with liberty and justice for none. > "James L. Marino" <jmar1371@DONTSPAMhotmail.com> wrote in message > news:Vgi0d.18421 [quoted text clipped - 8 lines] > where can we find them? > I've tried searching a couple of electronics catalogs without success. Look at hobby shops or online (Tower Hobbies). They are the connectors used for battery and servos for radio control airplanes, helicopters, boats and cars. John > The one rocket I'm working on is a 2 stage. One of the things I'm > concerned about is protecting the lower stage from the heat of ignition, > I don't need it frying the lower stage and couplings. I was told that it > shouldn't be a concern as the two stages should blow right > apart......but by that same way of thinking we can dispense with blast > deflectors on launchpads too. <SNIP> One key difference between the launch pad/rocket and lower stage/upper rocket separation scenario is that the launch pad doesn't move. A lower stage will, and it will separate from the upper engine MUCH more quickly than a rocket separates from the launch pad. This is mainly because the lower stage is lighter and is decelerated away from the rocket as the upper stage exhaust blast applies force to it (while the upper stage also accelerates away). You're right in that it still may cause some charring or other effects. Maybe spring-loading it with some sort of electromechanical trigger...? Dave |
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