2 stage considerations

[khabuda]

I just finished building a 2 stage rocket that I ripped off from U.S. Rocket's Two The Limit. All of the stability and everything works out, and I'm aware that I have maybe a 50/50 shot at getting this thing back when I send it on a C6 combo, but I'm curious if there are any other multi-stage considerations for a rocket of this size. There's no recovery listed in the model, but the weight and balance was all taken with the recovery in place. The only thing not accounted for is some amount of tracking powder. I haven't consulted any literature or anything for this, so I want to make sure it's a safe design. I'll post a pic shortly.

 

[khabuda]

I wanted to document it in case I never see it again.

 

[tsmith1315]

Mylar recovery device?

We got my son’s HiFlier back after a D16 flight, only because the Mylar streamer was visibly reflective on the ground.

 

[SolarYellow]

It appears to be gap staged. I don't see any vents in the booster to prevent separation prior to ignition of the sustainer.

I haven't played with your .ork, but I bet if you shortened the booster to only the length needed to directly butt the motors (not gap staged) and then trimmed the booster fins from the existing trailing edge tip to the new end of the BT, it would both be more stable and fly to a higher apogee.

 

[khabuda]

It appears to be gap staged. I don't see any vents in the booster to prevent separation prior to ignition of the sustainer.

I haven't played with your .ork, but I bet if you shortened the booster to only the length needed to directly butt the motors (not gap staged) and then trimmed the booster fins from the existing trailing edge tip to the new end of the BT, it would both be more stable and fly to a higher apogee.

They're directly butted. The sustainer motor extends about 2cm into the booster.

 

[Joekeyo]

Wrap engine joint with 1 layer of cellophane tape.

 

[bjphoenix]

I'm aware that I have maybe a 50/50 shot at getting this thing back when I send it on a C6 combo

I'm not brave enough for such a combo so I don't have direct experience but I'm thinking the odds are very much less than this. I would suggest the smallest motors you can get. A single stage minimum diameter rocket is hard enough to track on just a B motor.
Some years ago I built a clone of the Estes Apogee II but without the payload section. It is setting on my table loaded with motors right now, I've never gotten the courage to launch it.

 

[khabuda]

I'm not brave enough for such a combo so I don't have direct experience but I'm thinking the odds are very much less than this. I would suggest the smallest motors you can get. A single stage minimum diameter rocket is hard enough to track on just a B motor.
Some years ago I built a clone of the Estes Apogee II but without the payload section. It is setting on my table loaded with motors right now, I've never gotten the courage to launch it

I'm really not too worried about getting it back. I'm launching with Northern Colorado Rocketry, and my field is wide open, so it's a non zero chance of getting it back. I bought all these parts in bulk though, so one and done isn't going to break my heart. I guess I feel a little bad about the litter maybe, but it's not going to ruin that environment.

 

[BABAR]

Looks like a nice bird.

It’s your rocket to do whatever you like, obviously. I am unclear on your decision to do maiden flight on a C to C combo.

For such a small rocket, as you have said will make recovery of both booster and sustainer challenging.

It eyeballs stable, so I don’t see any major safety issues.

I may be in minority, but I feel that every rocket launched should be with intention of safe and undamaged recovery. If those conditions aren’t met, the rocket shouldn’t be launched.

A B6-0 has same max lift off weight as a C, just stages lower. I also believe in using lowest practical sustainer motor for first flight.

Rationale? Staging is cool. I like to see it stage and recover both parts and fly it again. If I succeed I can always fly it again with larger motors.

From a safety issue, priority 1 for motors is getting stack up to speed off the rod or rail. As said, B and C are both adequate, B might be a bit BETTER as it is slightly lighter, so less tail weight, better stability, and with lower mass slightly better acceleration. Anything above this requirement just stages higher, possibly nearly out of sight, which seems pointless to me.

As for sustainer motors, my main excitement is the staging event. Nice to see the sustainer light, make a short trail, after that any extra altitude is wasted on me, just means a longer walk.

For me, if I want altitude I will do a minimum diameter single stage with a bigger motor. Easier, cheaper, and more reliable.

I can see going larger if I am lifting a camera (in which case however I DEFINITELY want it back!). Even then I’d probably start with smaller motors and work up once rocket is “proven.”

Regarding vent holes, aside from taped motors, I always use vents for any gap over say 1.5 inches. But I rarely gap less than 15.0 inches, maxed successfully at around 53 inches. For what looks like your short gap you can probably get away with no vents.

As I said, your rocket, if goal is to lose it then C to C is a good bet.

Straight at trails!

 

[BABAR]

Oh, also absolutely agree with @tsmith1315 on streamer. Go with longest streamer you can easily pack. I know, increasing length to diameter over 10 does NOT slow rocket descent any more, but a long fluttering streamer is much easier to see in the sky and on the ground.

Also recommend painting both parts bright colors to make spotting them easier, especially the booster since it has no chute or streamer.

 

[khabuda]

Looks like a nice bird.

It’s your rocket to do whatever you like, obviously. I am unclear on your decision to do maiden flight on a C to C combo.

For such a small rocket, as you have said will make recovery of both booster and sustainer challenging.

It eyeballs stable, so I don’t see any major safety issues.

I may be in minority, but I feel that every rocket launched should be with intention of safe and undamaged recovery. If those conditions aren’t met, the rocket shouldn’t be launched.

A B6-0 has same max lift off weight as a C, just stages lower. I also believe in using lowest practical sustainer motor for first flight.

Rationale? Staging is cool. I like to see it stage and recover both parts and fly it again. If I succeed I can always fly it again with larger motors.

From a safety issue, priority 1 for motors is getting stack up to speed off the rod or rail. As said, B and C are both adequate, B might be a bit BETTER as it is slightly lighter, so less tail weight, better stability, and with lower mass slightly better acceleration. Anything above this requirement just stages higher, possibly nearly out of sight, which seems pointless to me.

As for sustainer motors, my main excitement is the staging event. Nice to see the sustainer light, make a short trail, after that any extra altitude is wasted on me, just means a longer walk.

For me, if I want altitude I will do a minimum diameter single stage with a bigger motor. Easier, cheaper, and more reliable.

I can see going larger if I am lifting a camera (in which case however I DEFINITELY want it back!). Even then I’d probably start with smaller motors and work up once rocket is “proven.”

Regarding vent holes, aside from taped motors, I always use vents for any gap over say 1.5 inches. But I rarely gap less than 15.0 inches, maxed successfully at around 53 inches. For what looks like your short gap you can probably get away with no vents.

As I said, your rocket, if goal is to lose it then C to C is a good bet.

Straight at trails!

I respect your assessment. I have another min dia 18mm that I'm planning to launch as well. I've been able to spot other small rockets at 2k feet as long as it's not high noon, so I have some degree of confidence that I'll retrieve them. If Hobby Lobby sells a B6-0 then I'll give a B combo a shot first. Part of my motivation for these small projects was being able to get the motors super cheap at the store. I'm working on a new HPR project with dual deploy and GPS now, and it's been nice to have smaller things to work on with less consideration for how it all plays out, and for considerably less money. Modeling in open rocket and seeing the design come to life has been the payoff for me with the small ones. Like I said, I'm going to be launching with a mess of tracking powder in the 2 stager, and will make a genuine attempt at recovery. Launching early in the day so the sun is low. If RigExpert still made these beacons I would definitely be shoving one in the payload wrapped in tape. All of the other tracking options seem overly bulky or expensive for what I'm doing. Wildman sells what looks to be a similar beacon, but it wouldn't even fit inside a BT-50.

 

[khabuda]

Quick follow up. I flew this down in Pueblo on Saturday, and I did recover it. It was definitely 100% luck though. The first stage burnout was at a pretty good angle, and she took off at an angle and I completely lost sight of it. I just stared at the horizon looking for any movement at all, and saw it out of the corner of my eye. I would bet it was a third to a half mile walk to get it. The booster came right back to the pad though.

I'm probably going to to build a stand for it and leave it on a shelf. I'm glad it survived, but I didn't get much out of it compared to the minimum dia 18mm build I did. It's easier to get those to fly a little straighter.