Two Staging a 10in. distance?

[Slickwilly]

I'm a scratch builder and love military rockets. I scaled a terrier aim 2 using 2in. mailing tubes in rocksim. The distance from booster engine to main engine was 14in. I read on the apogee site that anything over 10in. span would be a problem igniting upper stage and I would need to gap stage booster. So I decreased the booster distance to 10in. Does anyone have any experience with this amount of distance working reliably?:confused2:

 

[redsox15]

Are you talking about Estes engines or the bigger (G, H, I etc) engines that require electronics to ignite it?

In the case of Estes engines, I built a two-stage rocket (D12-0 to D12-7) where the distance between the motors was between 4 and 5in and the sustainer did not light. After the first launch I figured that the booster section was coming off before the sustainer was able to ignite so I drilled holes so that some of the pressure had somewhere to go. Launched it again...sustainer still didn't light. and now I have a rocket with the nose cone shoved halfway down the body tube. For the best shot of the booster engine lighting the sustainer is to have them as close together as possible (2-3in).

Good Luck hope this helped

Matt

 

[Verna]

I'm a scratch builder and love military rockets. I scaled a terrier aim 2 using 2in. mailing tubes in rocksim. The distance from booster engine to main engine was 14in. I read on the apogee site that anything over 10in. span would be a problem igniting upper stage and I would need to gap stage booster. So I decreased the booster distance to 10in. Does anyone have any experience with this amount of distance working reliably?:confused2:

If you are talking BP motors, yes many people have designs that are 10" apart. It's easiest with a single engine to another single engine but can be done with clusters too.

When we stage other than end to end we like to use a vented stuffer tube for each engine (at least 2 1/4" holes anywhere past half way up the tubes)and vent the main bt too in the same manner.

When staging over longer distances it helps to use engines with the largest nozzle openings possible for the upper stages too. For example, it's easier to get hot particles into the nozzle of a B4 than a B6 or D12 than a C6.

For some photos and tips that may give you some ideas for your design go here: https://www.sears572.com/supersaturnv.htm and scan the build article. It might help you if you are using BP engines.

Verna
vernarockets.com

 

[Slickwilly]

I had planned on using an Estes D booster with the option of a D12 or E9 upper engine. If you have rocksim I am attaching the file.

View attachment Scratch-Rim-2 Terrier (2 stage).rkt

 

[maricopasem]

I turned a Quest Terrier-Orion into a two-stage rocket. The distance between the booster and upper stage motors is about 9 inches. I flew it a week ago Saturday on a C6-0 to C6-7 combo and it staged perfectly. I didn't have a stuffer tube or vent holes or anything and it worked flawlessly. YMMV though.

 

[luke strawwalker]

Are you talking about Estes engines or the bigger (G, H, I etc) engines that require electronics to ignite it?

In the case of Estes engines, I built a two-stage rocket (D12-0 to D12-7) where the distance between the motors was between 4 and 5in and the sustainer did not light. After the first launch I figured that the booster section was coming off before the sustainer was able to ignite so I drilled holes so that some of the pressure had somewhere to go. Launched it again...sustainer still didn't light. and now I have a rocket with the nose cone shoved halfway down the body tube. For the best shot of the booster engine lighting the sustainer is to have them as close together as possible (2-3in).

Good Luck hope this helped

Matt

Did you extend the motor tube (BT-50) up to the nozzle of the upperstage engine, if this rocket used a larger size body tube than BT-50?? With gap staging, you really need to have a stuffer tube to contain all the burning particles of propellant and hot gases (there is a HUGE debate as to which actually does the ignition part of the upperstage, or infrared radiation from some combination of the two) so that the blow-through of the lower stage engine is 'aimed' down the 'barrel' right at the upperstage engine nozzle.

You did the right thing with the ports to relieve the pressure, but if the engine tube in the booster is short while the booster is larger than the motor, there's a lot of space for the heat/particles from the booster engine to get 'lost' in and dissipate to the point the upperstage won't ignite...

Also, it's always a good idea to check the nozzle end of your upperstage motor to make sure that NOTHING is blocking the nozzle... sometimes a spare bit of clay from the nozzle forming process when the engines are made will be partially embedded or covering the end of the propellant grain (the "dimple" that the ignitor goes in) and anything that gets between the propellant and the blow-through from the lower stage motor will greatly reduce your chances of upperstage ignition.

Hope this helps! Good luck! OL JR

 

[rokitflite]

Did you extend the motor tube (BT-50) up to the nozzle of the upperstage engine, if this rocket used a larger size body tube than BT-50?? With gap staging, you really need to have a stuffer tube to contain all the burning particles of propellant and hot gases (there is a HUGE debate as to which actually does the ignition part of the upperstage, or infrared radiation from some combination of the two) so that the blow-through of the lower stage engine is 'aimed' down the 'barrel' right at the upperstage engine nozzle.

You did the right thing with the ports to relieve the pressure, but if the engine tube in the booster is short while the booster is larger than the motor, there's a lot of space for the heat/particles from the booster engine to get 'lost' in and dissipate to the point the upperstage won't ignite...

Also, it's always a good idea to check the nozzle end of your upperstage motor to make sure that NOTHING is blocking the nozzle... sometimes a spare bit of clay from the nozzle forming process when the engines are made will be partially embedded or covering the end of the propellant grain (the "dimple" that the ignitor goes in) and anything that gets between the propellant and the blow-through from the lower stage motor will greatly reduce your chances of upperstage ignition.

Hope this helps! Good luck! OL JR

I second this!

 

[New Ocean]

Wow I had no idea these kinds of distances were possible. I would have assumed only electronics or fuse would work.

This is why I joined up here.

 

[adrian]

One other thing to note with a long booster is that it may come down ballistic - I've seen this happen more than once. Unless it's a cluster, there won't be an ejection charge in the booster, and anyway you need clear passage right through the booster for the burning particles of fuel to reach the upper stage motor.

So I usually put something like this at the top of the booster. The core tube has inside diameter is slightly larger than the outer diameter of the upper stage motor tube and is made by using a piece of the same tube, cut lengthwise to expand, then sealed with a piece of heavy paper. Centring rings match the inside diameter of the upper stage body tube. The streamer is Nomex, not long enough to be a proper streamer but enough to destabilise the booster.

 

[Slickwilly]

If I use a BT-80 tube as a booster I would have room for a BT-5 parachute tube that goes between and is cut through the front and rear booster centering rings along side the main booster engine tube. Since I will vent the stuffer tube the ejection would push a small 6 in. paracute and 8 in. shock cord out of the parachute tube. Attaching the shock cord to the rear centering ring. I could then put a small strip of masking tape over the end of the paracute tube to hold back the chute. Would this work or would it destabilize the rocket?

 

[luke strawwalker]

It's worth a shot, but you're going to have a VERY hard opening!!! You'd probably do better with a streamer...

Additionally, if the BT-5 'chute compartment' is your only vent, it's possible that the stage could blow free of the upperstage before the upperstage engine ignited... because (assuming your upperstage is the same diameter as your first stage) the surface area of the upper stage centering rings above the stage coupler is significantly larger than the 'blocked' (chute and tape) BT-5 tube at the rear of the lower stage. Same principles as basic hydraulics-- pressure put on a larger surface area creates more force than the same pressure put on a small area...

In other words, it MAY act like there's no vent at all, and blow the stages apart before the upperstage ignites...

Good luck! OL JR

 

[adrian]

If I use a BT-80 tube as a booster I would have room for a BT-5 parachute tube that goes between and is cut through the front and rear booster centering rings along side the main booster engine tube.

A BT-80 tube has enough room for a cluster, which opens up all sorts of possibilities but the basic idea is the same for all of them. The core motor tube leads to the upper stage, is loaded with a booster motor, and will ignite the upper stage motor. Other motor tubes, isolated from the core tube, are loaded with regular motors with the shortest available delay charge and will deploy your choice of recovery system. For example, fit two of those BT-5 tubes, put an A10-3T in each, and let those eject parachutes or streamers.

 

[SwingWing]

The Edmonds 2-stage glider "Stage 2 Thunder" uses a 15" motor tube, of which the motor casings take up 2.75" leaving a gap stage length of 12.25".
I have launched mine several times, never having trouble staging D12-0 to D12-3. Getting both gliders to fly properly, thats another conversation:shock:

https://www.edmondsaerospace.com/TheThunder.html