Looking for advice on a Star Orbiter build

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HandsomeRob

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I am (at a glacial pace) putting together a Star Orbiter and, since it's inception, have not been able to decide exactly how I want this to all go together so I thought I'd turn to the group and pick y'alls brains about it.

The build is ever-so-slightly hot rodded and will mainly be flown on composite motors. I plan on using a chute release and a Missile Works T3 GPS tracker using the shock cord mount for easy swappability. (Sidenote: while the chute release has some merit, I totally get that the T3 may be overkill. It is my intent to get comfortable with both products on this smaller rocket so I am confident in using them in larger, more expensive rockets)

I have the lower half completed with a baffle and shock cord mount and here's where I can't decide what to do. Do I just glue the upper tube to the lower half and run everything like normal? (Nose cone pops, pulls everything out, bobs you're uncle) OR could I friction fit the nose cone very tightly, and separate the rocket at the baffle? The benefit is a zipperless design but that upper body tube is long and I'm worried about the chute not pulling out. There will be no av bay and if I simply friction fit the nose cone, that allows me easy access to every point on the rocket for the entire length of shock cord BUT if that cone pops instead of the body tube, again, I worry about the chute pulling out. Obviously, I could also glue the nose in place, I just like the idea of being able to access everything once the build is done. And I do suppose I could just fly it and see what happens...

So, long story short:

Keep it traditional with A:
Starorbiter2.jpg

or

Try something different with B:
Starorbiter1.jpg

I will not be launching the cat.....unless she continues to get into rocket parts...

Thanks for any input!
 
I typically go with the first option. If you want to go with the second one, just secure the nose cone with a single shear pin to make sure it doesn't come off. Tie the chute to a loop close to the baffle to make sure it doesn't get hung up in the BT (looks like you are already doing this in the second pic). You can probably drop that quick link and connect the chute directly to your swivel to save some weight.

I've had a Star Orbiter on my build pile for awhile now. One day I'll get around to it. Looks like a good flier for F22Js.

cheers - mark
 
When I have chutes that I want to be sure are pulled out of the tube, I loosely wrap some shockcord around the bundle so the separation starts to tug the chute towards the opening. Don't wrap it in the shroud lines though, I've been chastised enough not to recommend doing that.
 
AH! I hadn't received any notification of replies, so It's taken me a little bit to circle back.

Great advice, both of y'all! Thanks!

Mark, the idea of a shear pin had actually crossed my mind. Good to know I wasn't too far off track! Looks like the club launch this month is going to get rained out so this buys me more time to buy stuff (and paint) so I may go down that road. For what this rocket costs, as long as I test it without electronics first, I should experiment a little....buut I'm still not 100% sure which way I want to go.

My intent with the quick link was to move this chute around between different, similarly weighted, mid power rockets but this one and the swivel it's on are awfully heavy. I may look for alternatives and stick these in the parts bin until I fly some heavier stuff. Fishing line swivels have always served me well.
 
I built mine with a nose block where the tubes join to create a long payload section and mounted the shock cord in the lower half. I used a Kevlar leader with a long elastic cord. It has worked well so far. Splitting the rocket in the middle does make the it easier to transport to and from the field.
 
My intent with the quick link was to move this chute around between different, similarly weighted, mid power rockets but this one and the swivel it's on are awfully heavy. I may look for alternatives and stick these in the parts bin until I fly some heavier stuff. Fishing line swivels have always served me well.

In large sporting goods stores that sell fishing tackle you can get coast-lock type snap swivels with ratings up to a couple hundred pounds that will be MUCH lighter than that quick link and more than adequate to the task....

My Star Orbiters are all configured with the upper six inches of body tube as a payload compartment and a baffle at the join as you are doing. Sort of halfway between the two configurations you're considering.
 
I built mine with a nose block where the tubes join to create a long payload section and mounted the shock cord in the lower half. I used a Kevlar leader with a long elastic cord. It has worked well so far. Splitting the rocket in the middle does make the it easier to transport to and from the field.
Built mine the same way and added a couple of removable plastic rivets (shear pins) to secure the nose cone. The only electronics I currently own is a simple beeping read out altimeter and it works perfectly in the Orbiter’s payload bay.
 
My Star Orbiters are all configured with the upper six inches of body tube as a payload compartment and a baffle at the join as you are doing. Sort of halfway between the two configurations you're considering.

I did a scratch built rocket with my son using parts from the shop that he picked out from the pile and fins from his design that I cut out for him. Once it was complete and I had it next to my star orbiter, I realized that aside from the fins, its exactly what we built. (no wonder I liked it so much). Anyway, it was also exactly as you did yours here: a baffle a the tube joint with one end of the shock cord attached, then a small av bay at the top for a tracker, JL alt 3 etc. Upper attachment point for the shock cord is in the payload bay bulkhead. I use a single plastic rivet to hold the NC on.

I built my Star Orbiter completely stock and I love it. By far my favorite Estes Kit.
 
Thought I'd give an update. I did end up splitting it in the middle and I'm really glad I did. I tried something new (to me), planned it out, looked for potential hazards and addressed them, and successfully flew and recovered the rocket. Another step towards high power rocketry and a nice bit of experience.

I ditched the heavy quick link for a much lighter snap swivel for fishing line, but still kept the swivel mounted on the chute because it seemed the easiest way to attach things. I also used a shear pin to make extra sure the nose cone wouldn't pop. I panicked at the last moment and decided to put a 6in square of nomex above the baffle since the parachute would essentially be sitting directly on top of it. This proved to maybe not be necessary as not any piece of the rocket above the baffle showed any sign of charring. I assume this is due to the distance between the baffle and the ejection charge. On other LPR rockets I have, the baffle is much closer to the end of the motor and the shock cord tends to get pretty sooty. I decided to not fly the GPS tracker this past weekend because I just hadn't had a chance to play with it. It is also a pretty heavy setup compared to the rocket, so I'm sort of nervous to fly with it. It sims just fine but becomes a LOT of weight towards the nose of the rocket.

I put it up on an Aerotech E23 in a 29 40-120 case and it flew beautifully. Nearly perfect straight up flight. At apogee, the charge popped, the cute unfurled. I also brought a chute release that I was going to fly on the 2nd flight if all went well on the first, but this ended up being the only flight of the day as it was just so damn hot and I didn't want to walk around the field anymore.

Thanks to everyone for their input!! I am so excited to fly this again and on much bigger motors!

IMG_20180604_134622.jpg

IMG_20180601_082734.jpg

IMG_20180602_133806.jpg

IMG_20180602_133753.jpg

IMG_20180602_133742.jpg
 
Nice build thread!

What baffle design did you use?

I am also building a Star Orbiter. Going with a baffle built into the tube coupler. Trying to decide if 7 x 3/16" holes are enough on the bottom of the baffle, or whether I want to go half-moon instead. Don't think I can get bigger holes in the 1/8" ply without buying a drill press... I had to paper the sides just to keep holes this big from cracking!
IMG_2107.jpg

BTW, is that a black micro rail button hidden on the black checkerboard decal?
 
Nah, it's just a shear pin. I built this thing with the stock lugs but I do kinda wish I had used rail buttons...

As for the baffle, I bought the Apogee baffle found here: https://www.apogeerockets.com/Build...h=42_312_316&zenid=5t8dkie8199uogs7rtj9idahp4

On the bottom side of the upper portion of the baffle, I epoxied a bulkhead, this one: https://www.apogeerockets.com/Build...24mm_Plywood?zenid=jo65vsjoftp4ai2rhh4u286fq7
and drilled a hole so that the screw eye would go through the upper part of the baffle, then into the bulkead so that there was plenty of surface area to hold everything. ENTIRELY possible that all I really needed to do was run a screw eye through the baffle but I wanted to make sure it had enough bite to never come undone. I hope that explanation makes sense haha

I also epoxied the blast side of everything in the baffle to protect it from the ejection charge.
 
Also, because I knew no matter where I split the rocket, I was mounting the shock cord to the end of the baffle, I sunk the end of the baffle slightly into the tube coupler and added more epoxy to the top so that there was ZERO chance of it ripping out during ejection
 
Thanks for the advice!

I ended up designing a variation on a half-moon baffle built with 1/8 ply around a 3/8 hardwood dowel with an eye screw through the top plate.

IMG_2108.jpgIMG_2109.jpg

Next time, $6 for an Apogee baffle sounds a LOT better.
 
Nice build thread!What baffle design did you use?I am also building a Star Orbiter. Going with a baffle built into the tube coupler. Trying to decide if 7 x 3/16" holes are enough on the bottom of the baffle, or whether I want to go half-moon instead. Don't think I can get bigger holes in the 1/8" ply without buying a drill press... I had to paper the sides just to keep holes this big from cracking!View attachment 345852
OK, I know it's water under the bridge, but I can't help myself.

  1. You've easily got room around the ring of six holes for another ring with 12, totaling 19 × 3/16" holes.
  2. There are relatively inexpensive drill presses easily had that are not of machine shop quality, but plentygood enough for this.
  3. You don't need one if you take these steps:
A. Secure the bulkhead to a piece of scrap using masking tape. Make sure it can't move.
B. Lay out the hole pattern on the tape.
C. Make sure your drill bit is really sharp and fresh. Dull tools only cause:​
i. messy projects
ii. injuries​
 
  1. You've easily got room around the ring of six holes for another ring with 12, totaling 19 × 3/16" holes.

Wouldn't drilling holes around the whole plate defeat the purpose of the offset-holes design? The idea was to have center holes on this plate, and outer holes on another.
 
BlastoffDFW your design will work just fine, I use similar baffles often, the dowel through the center helps the baffle resist damage from AeroTech red caps ( ejection charge covers on reloadable motors).
 
Thanks for the advice!

I ended up designing a variation on a half-moon baffle built with 1/8 ply around a 3/8 hardwood dowel with an eye screw through the top plate.

View attachment 345896View attachment 345895

Next time, $6 for an Apogee baffle sounds a LOT better.

A $6 Apogee baffle is definitely time saved but that's a really cool design! And, as Rich points out, that dowel will provide resistance to the Aerotech red caps. (I put a layer of epoxy on the bottom side of my baffle for the same effect but I like this idea better!)
 
A $6 Apogee baffle is definitely time saved but that's a really cool design! And, as Rich points out, that dowel will provide resistance to the Aerotech red caps. (I put a layer of epoxy on the bottom side of my baffle for the same effect but I like this idea better!)

Not only does the dowel strengthen the baffle but since its hardwood and long the screw eye gets full grip instead of just a few threads in 1/8" plywood, always make sure and pre-drill the dowel for the screw eye so it does not split.
 
Wouldn't drilling holes around the whole plate defeat the purpose of the offset-holes design? The idea was to have center holes on this plate, and outer holes on another.
Yeah, forget it. As others have said, what you've got is fine.

(You'd mentioned concern over capacity for gas flow, and that you wished for more area drilled out, but I wasn't thinking of the inside-to-outside geometry as the functional part. It's done now anyway, so never mind.)
 
I thought for sure I had posted that I did the mid-split and flew it exactly one time at the launch last month and it performed beautifully. Maybe I just imagined I posted that haha!

Anyway, it was an absolutely perfect flight but it was late in the day and I was hot and tired and didn't want to pop in the F motor and try it with the chute release. That I saved for yesterday but unfortunately, our launch got rained out....so I continue to wait to fly it some more...

In the meantime, that blue thing in the pics above is the 3D printed housing from Missileworks for the T3 GPS tracker (again, I don't necessarily intend to fly this rocket so high I lose it, I just want to get comfortable with electronics.) I have a spot for it along the shock cord just below the nose cone for attachment and it all goes together nicely. My concern is, however, that it's too nose heavy and, therefore, way overstable. It sims perfectly fine with it in Open Rocket, but it does have a stability cal of, like 8, so I'm nervous about actually using it on this rocket.

While I will most likely save the tracker for a larger rocket (or one not as long as a Star Orbiter, like a Super Big Bertha) what are the dangers of flying an over stable rocket?
 
Overstable means highly susceptible to weathercocking. It is probably OK even at 8 calibers on a windless day (as if "windless" ever happens). And high launch speed helps reduce weathercocking, so it's good to launch an overstable rocket with a high thrust motor. Also, I recently read an article (I'll have to see if I can dig it up) explaining how, because Barrowman left out body lift, long skinny rockets actually need the high static stability numbers they tend to end up with. (Because body lift causes the CP to migrate backward with angle of attack, not by enough to be a big deal with "normal" rockets, but when there's lots of body it becomes important.)

I'm not experienced or confident enough to say you shouldn't be concerned. But on a calm day with a kicky motor, I think you probably would be.
 
1: At the end of the previous post I should have added a long, stiff launch guide as another good mitigating factor. That's good for both low and high static margins, since speed at the end of the guide is always good.

2: The paper is by Robert Galejs of MIT. You can find it here, or reprinted in Apogee's Peak of Flight # 470. The paper's concluding summary states:
An extension to the Barrowman equations was presented that includes the effects of body lift. This extension fits Bob Dahlquist’s experimental results quite well and explains an unstable flight of a long/skinny rocket. This extension increases the ability to predict CP out to about 15° angle of attack. For “normal” rockets, the one caliber stability rule of thumb appears to be a good rule of thumb. However, for long/skinny rockets, upwards of ten calibers may be called for and for short/fat rockets less than half a caliber may be sufficient.

Please forgive a little bragging; it was I who brought the paper and Mr. Galejs's contact information to Mr. Van Milligan's attention after I read it thanks to a link in another thread here.
 
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I thought for sure I had posted that I did the mid-split and flew it exactly one time at the launch last month and it performed beautifully. Maybe I just imagined I posted that haha!

Anyway, it was an absolutely perfect flight but it was late in the day and I was hot and tired and didn't want to pop in the F motor and try it with the chute release. That I saved for yesterday but unfortunately, our launch got rained out....so I continue to wait to fly it some more...

In the meantime, that blue thing in the pics above is the 3D printed housing from Missileworks for the T3 GPS tracker (again, I don't necessarily intend to fly this rocket so high I lose it, I just want to get comfortable with electronics.) I have a spot for it along the shock cord just below the nose cone for attachment and it all goes together nicely. My concern is, however, that it's too nose heavy and, therefore, way overstable. It sims perfectly fine with it in Open Rocket, but it does have a stability cal of, like 8, so I'm nervous about actually using it on this rocket.

While I will most likely save the tracker for a larger rocket (or one not as long as a Star Orbiter, like a Super Big Bertha) what are the dangers of flying an over stable rocket?

Over stable rockets in my experience have a tendency to weathercock into the wind a bit more. Pump up the wind a bit in your simulation and you’ll likely see this represented by an altitude decrease as the horizontal velocity increase and the vertical velocity decreases.
 
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