Some AP 2-stager questions

Hello All,

Although I am in Budapest and cannot build any rockets at the moment,I'm resting my legs and in the process, designing my summer project. Plain and simple, I want to build a 2-stager with the following:

Sustainer:
2.6in Blue tube airframe
38mm mount big enough for 6gXL (cause it sucks being limited!)

Booster:
3in Blue tube Airframe
38mm mount big enough for a 6gXL (once again, why limit myself!)

to convert from 3in to 2.6in I will use the "feathering" method in which you cut out little triangles from the end of the BT, then strap them down and apply epoxy generously. I may just stick with 2.6in, as this does increase complexity.

I have MANY questions, however, and I hope that I can get them answered. Here they are:

1. Do I put the staging electronics in the interstage coupler, or in the sustainer? Does it matter?

2. How do I ensure that the igniter remains in the motor at liftoff?

3. Does the Booster need Dual Deployment?

4. if the staging electronics is in the interstage coupler, has anyone ever figured out a way to put the DD electronics in there too? I can't see how it can pop open at the interstage coupler AND midsection and have the electronics in the coupler. It's like putting your AV bay in the nosecone.

5. Should I have a BP charge that performs separation, or should I rely on drag separation? Is it very damaging to the booster to rely on the sustainer motor exhaust to push it off? Do I risk a mid-air CATO by doing this?

6. If I use BP to seperate the sustainer and booster, I'm assuming I need to ensure BP residue does not get up in the sustainer motor... correct?

I know that alot of these questions are merely personal preference, but I would like to know the benefits/drawbacks to each before I start planning.
And if this seems like I'm biting off more than I can chew, let me know!

As they say over here... köszönöm!
Alex

For most of your questions, there are multiple answers!

1. Either... it's been done both ways, many times. If you put them in the interstage, you'll need to spend some time making
sure they're flame proof, unless you use a separation charge.

2. I used a couple of pieces of nichrome wire wrapped around the ignitor, with the ends of the wire splayed out and 'mashed'
between the bulkhead and top fuel grain.

3. Boosters very rarely need dual deployment. Probably much more trouble than it's worth as well.

4. In most of the 2-stages I've worked with or seen, the interstage coupler is essentially the 'nosecone' for the booster.
The DD deployment for the sustainer needs to be in an Av-Bay in the sustainer. I'm sure there are really creative ways
of doing this differently, but why?

5. A lot of people do a separation charge, some do not. If you don't use a Sep charge, you'll need to vent the Interstage so the sustainer
motor doesn't overpressurize. Also more work to make sure your staging electronics don't get toasted, depending on how you handle
Question #1.

6. BP residue won't effect the sustainer motor. It's not something I've worried about or seen anyone else worry much about either.

Hope this helps you out a bit Alex!

Best of luck!

R

I've been simming out a "test rocket", and I'm getting suprising altitudes from the combonation of 2 H's! With 2 I motors I totally bust my Club's waiver.... Woha. 2-stagers are awesome!

I've decided a few things:

1. Booster will drop away at booster burnout (drag separation)

2. Booster will be Dual-Deploy (because through my sims, I've seen the booster end up at 3000 feet or so, too far for me to risk it drifting to the trees) using a DDC22 (who cares how high the booster goes!)

3. Staging/DD of the sustainer will be done Via a raven mounted in an AV bay fixed to the fin can. A single DDC22 in the nose will activate the Main chute charge.

I'm still confused about how to hold the igniter into the motor until it is ignited.

As of now, I'm planning an H400Vmax to an H100CL. Attached is a rocksim file of my planned rocket.

View attachment 2stager.rkt

Two-stagers are fun. A few of my opinions below. I can't see your file, so I'll probably miss some of your design features.

Jim

Sustainer:
2.6in Blue tube airframe
38mm mount big enough for 6gXL (cause it sucks being limited!)

Booster:
3in Blue tube Airframe
38mm mount big enough for a 6gXL (once again, why limit myself!)

--- Shorter 54mm motors might be easier. Two-stagers get pretty long as it is.

to convert from 3in to 2.6in I will use the "feathering" method in which you cut out little triangles from the end of the BT, then strap them down and apply epoxy generously. I may just stick with 2.6in, as this does increase complexity.

--- Feathering sounds a bit crude. Staying with the same diameter would make the staging coupler easier (just a coupler tube).

1. Do I put the staging electronics in the interstage coupler, or in the sustainer? Does it matter?

--- The main disadvantage of putting electronics in the interstage coupler is that the parts have to stay together through the ignition of the sustainer. I like to separate the stages and then light the sustainer. I do this from above. The electronics can be at the top of the sustainer fin can or in a conventional electronics bay. I use the convensional bay with breakwires for the separation charge and sustainer igniter.

2. How do I ensure that the igniter remains in the motor at liftoff?

--- I don't think this is a problem for 38 mm motors. If you secure the igniter at the bottom of the motor, it won't have enough room within the motor to fall down.

3. Does the Booster need Dual Deployment?

--- Obviously depends on the field. Due to extra drag, the booster apogee might be lower than you think. This might allow motor deploy, which would simplify your design.

4. if the staging electronics is in the interstage coupler, has anyone ever figured out a way to put the DD electronics in there too? I can't see how it can pop open at the interstage coupler AND midsection and have the electronics in the coupler. It's like putting your AV bay in the nosecone.

--- If you are willing to use breakwires, you can do this (but I wouldn't recommend dual deploy or electronics in the interstage).

5. Should I have a BP charge that performs separation, or should I rely on drag separation? Is it very damaging to the booster to rely on the sustainer motor exhaust to push it off? Do I risk a mid-air CATO by doing this?

--- I always use a separation charge. If you go with a larger diameter booster, you probably won't need it.

6. If I use BP to seperate the sustainer and booster, I'm assuming I need to ensure BP residue does not get up in the sustainer motor... correct?

--- This probably isn't a problem, but I normally cover the nozzle with something anyway. For a 38 mm CTI, the red plastic cover would work fine, and would hold the igniter in place too.

1. Booster will drop away at booster burnout (drag separation)

--- Don't count on drag separation is the two sections are the same size.

2. Booster will be Dual-Deploy (because through my sims, I've seen the booster end up at 3000 feet or so, too far for me to risk it drifting to the trees) using a DDC22 (who cares how high the booster goes!)

--- Again, don't over-predict the booster apogee. A smaller chute with motor deploy perhaps? If you decide motor deploy for the booster, white thunder motors would be better than vmax motors.

3. Staging/DD of the sustainer will be done Via a raven mounted in an AV bay fixed to the fin can. A single DDC22 in the nose will activate the Main chute charge.

--- One recommendation I would provide, whatever the design, is to minimize your tube breaks wherever possible. Your approach should allow that.

awseiger said:

Hello All,

Although I am in Budapest and cannot build any rockets at the moment,I'm resting my legs and in the process, designing my summer project. Plain and simple, I want to build a 2-stager with the following:

Sustainer:
2.6in Blue tube airframe
38mm mount big enough for 6gXL (cause it sucks being limited!)

Booster:
3in Blue tube Airframe
38mm mount big enough for a 6gXL (once again, why limit myself!)

to convert from 3in to 2.6in I will use the "feathering" method in which you cut out little triangles from the end of the BT, then strap them down and apply epoxy generously. I may just stick with 2.6in, as this does increase complexity.

I have MANY questions, however, and I hope that I can get them answered. Here they are:

1. Do I put the staging electronics in the interstage coupler, or in the sustainer? Does it matter?

2. How do I ensure that the igniter remains in the motor at liftoff?

3. Does the Booster need Dual Deployment?

4. if the staging electronics is in the interstage coupler, has anyone ever figured out a way to put the DD electronics in there too? I can't see how it can pop open at the interstage coupler AND midsection and have the electronics in the coupler. It's like putting your AV bay in the nosecone.

5. Should I have a BP charge that performs separation, or should I rely on drag separation? Is it very damaging to the booster to rely on the sustainer motor exhaust to push it off? Do I risk a mid-air CATO by doing this?

6. If I use BP to seperate the sustainer and booster, I'm assuming I need to ensure BP residue does not get up in the sustainer motor... correct?

I know that alot of these questions are merely personal preference, but I would like to know the benefits/drawbacks to each before I start planning.
And if this seems like I'm biting off more than I can chew, let me know!

As they say over here... köszönöm!
Alex

Click to expand...

Subscribed, Ya lets not bust the waiver.... But nothing says we cant call in for a window, and deploy Recon/Recovery teams ahead of time. With a call for winds aloft, and three helium balloons with some foil and a sunny day so we can see where it is headed (yes naughty and littering)

How is Hungary? That is the birth place of beer? or at least Pilsner, no? hope you are warm and well fed.

Scott

SAC of MMMSClub said:

Subscribed, Ya lets not bust the waiver.... But nothing says we cant call in for a window, and deploy Recon/Recovery teams ahead of time. With a call for winds aloft, and three helium balloons with some foil and a sunny day so we can see where it is headed (yes naughty and littering)

How is Hungary? That is the birth place of beer? or at least Pilsner, no? hope you are warm and well fed.

Scott

Click to expand...

Not the birthplace of beer, Depressingly. They do like their wines over here, as well as Goulash soup. Yum.

I've been thinking about the use of breakwires. It would be *very* cool to only need a single Raven Altimeter for the sustainer. I'm spending some idle down time between things looking up various connector styles that could couple a central AV bay to the bottom motor. Something along the lines of Banana jacks seems like it would work.

There's also running the wire through the tubular kevlar I plan to use as the apogee cord. I've never done this, but I know where to get some super-flexi large-guage Automotive zip cord (some of my friends have those silly subwoofers ). This with some slack at each end would work. Plus, I don't really care if the wire fails at apogee ejection, just during boost which is unlikely.

Seems like my fears of the igniter falling out are not warranted. Even if it does, and the motor fails to ignite, the DD electronics should still save the sustainer just fine.

Another thing I thought of: When the sustainer ignites, and the igniter is thus thrown out the rear end of the motor, is it going to be bad having it dangle from it's electrical points on the rear of the rocket?

Thanks everyone for all the help! I really want to think this one through before I begin implementing things.

Alex,

well rest assured you are not missing any flying at MMMSC. Snow snow and more ^%$# snow as far as the eye can see.

S.

Here's how I do breakwires (although I normally use 24 gauge, multi-strand speaker wire). One thing that is important about using them it to make sure they are secured on both ends. You don't want the wire pulling on your Raven. I usually have a couple of extra feet of wire so that nothing will impede the sections from coming apart. I would guess I've done this about 50 times with no problems.

Jim

JimJarvis50 said:

Here's how I do breakwires (although I normally use 24 gauge, multi-strand speaker wire). One thing that is important about using them it to make sure they are secured on both ends. You don't want the wire pulling on your Raven. I usually have a couple of extra feet of wire so that nothing will impede the sections from coming apart. I would guess I've done this about 50 times with no problems.

Jim

Click to expand...

Now that's way simpler... Great Idea. This simplifies quite a bit. I seem to be forgetting my KISS principle teachings!

SAC of MMMSClub said:

Alex,

well rest assured you are not missing any flying at MMMSC. Snow snow and more ^%$# snow as far as the eye can see.

S.

Click to expand...

So I heard... At least it will be warm by the time flying starts picking up!