"Finless" Rocket Design - Ram Air Intake Stabilization?

KenECoyote said:

Ah! Got it now! Thanks! :smile: Unfortunately the sale is a bit late. :wink:

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I bought a pack of 6 for goofing around and for the grandrocketeers. Since I bought so little, the outrageous shipping raised the cost to about 5 bucks a pop. One has to get a 29mm mount...

rstaff3 said:

I bought a pack of 6 for goofing around and for the grandrocketeers. Since I bought so little, the outrageous shipping raised the cost to
about 5 bucks a pop. One has to get a 29mm mount...

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I had actually purchased a 12-pack (?) set off Ebay early in the year; however almost every tube had shipping damage which was not noted in the listing, so the seller refunded me all the money. While very nice (and maybe the full refund was more on Ebay's part), I thought the seller shouldn't lose out completely, so I sent back about 30 bucks figuring I could still use the parts and decals.

I forgot to add these...

The left is an early version of the RAIStone (hand lettered!), Middle is PolaRAIS (flew well on B6) and finally PolaRAIS II (didn't fly well and crashed/smashed).



PolaRAIS on B6:



Video View #1:
[video=youtube;bEcwm552J04]https://www.youtube.com/watch?v=bEcwm552J04&feature=youtu.be[/video]

Video View #2:
[video=youtube;hzvYpvg7-1o]https://www.youtube.com/watch?v=hzvYpvg7-1o&feature=youtu.be[/video]

Also note I've updated the earlier WhatSideDown post with another video.

I really like the Polaris!

rstaff3 said:

I really like the Polaris!

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I really like it too! :wink: Unfortunately it took a LOT of custom/labor intensive work to make and ended up having some damage on one of the landings (heavy rocket on streamer over ice isn't really forgiving). I'll revisit once I get the minis and more standard designs in good shape.

Here's a video of the PolaRAIS on a C6...it went cruise missile shortly after leaving the rod; however it does look stable (pretty darn straight...just not vertical!). I believe I need higher speed off the rod by way of a bigger motor (without adding extra weight if possible). I may need to test it on a D10.
Turn up the sound and tell me what you think of it...best sounding C6 I've heard so far! :w:


[video=youtube;5UqQ9jt2mQA]https://www.youtube.com/watch?v=5UqQ9jt2mQA[/video]

That did seem to be a loud C6. Finless rockets, from my meager experience, like to go fast. That was the same profile as the third flight of my Estes SS1 (the small one). Was it windy?

rstaff3 said:

That did seem to be a loud C6. Finless rockets, from my meager experience, like to go fast. That was the same profile as the third flight of my Estes SS1 (the small one). Was it windy?

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I don't recall it being windy, but there may have been upper shear winds since I live next to some small mountains.

I believe there were a few factors involved with the loud sounding motor and one of them includes the design itself...it appears to amplify the exhaust sound. I'll do sound metering tests if I ever get it up to 29mm and higher.

very cool designs, I was thinking you could also do a Gemini-Titan version, that would be pretty cool.

GlenP said:

very cool designs, I was thinking you could also do a Gemini-Titan version, that would be pretty cool.

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Thanks!

I actually had considered the GT (since it's one of my favorite rockets) as well as the Titan III - the boosters also having RAIS should add to stability.

Actually, come to think of it, I had started on a Gemini Titan, but didn't get too far...too many designs to build and rockets to test! :caffeine:

KenECoyote said:

What would be really cool is that if I could get it to work reasonably well, perhaps it can almost look like one of these (I know...daydreaming ):

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I forgot to note that I actually did start on one test prototype for this design...


First two flights weren't so good...way too heavy and draggy for the motors I used and there was significant damage on the second crash, so I've shelved for now; however I have another idea to make this one work and I may revisit one day.

My gut says finless rockets that are longer and skinnier will do better. But that one would be helped out by base drag. If you keep this up, I may be motivated to build something this winter.

rstaff3 said:

My gut says finless rockets that are longer and skinnier will do better. But that one would be helped out by base drag. If you keep this up, I may be motivated to build something this winter.

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IMO this still blurs the lines since the bottom is closed and air funneled out sideways...plus the large frontal area has a lot of drag as well. If I do get it working ("finless" or not), I may work on a Lunar Lander after that.

Feel free to build something this winter! It'd be great to have your input and experience on this design!

KenECoyote said:

I forgot to note that I actually did start on one test prototype for this design...

First two flights weren't so good...way too heavy and draggy for the motors I used and there was significant damage on the second crash, so I've shelved for now; however I have another idea to make this one work and I may revisit one day.

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Hey Ken, I have a few questions. Diameter? Length? Motor?

rstaff3 said:

Hey Ken, I have a few questions. Diameter? Length? Motor?

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4" Diameter, 9" long and 24mm motor mount. This was actually one of the very early versions I tried experimenting with on the side (circa Feb) before I got the finless version I had sent you to test, so it was really a long shot. I just took it out and had forgotten about how it was built...actually quite cool if I can say so myself! :grin:

I'll try to update with some pics. I think I can make it work with some mods and I've gotta try to enter this into Rocksim for some base stability (or instability) figures. I think adjusting the intake and vents and also making it spin may do it.

Pics as promised! Note that I used an oatmeal container with a ridged plastic ring on the lid...this allowed the nosecone I made (from cardstock and coated with epoxy) to sit into the channel for a nice fit.



















[video=youtube;QQRm_WXNrtI]https://www.youtube.com/watch?v=QQRm_WXNrtI&feature=youtu.be[/video]

I'm surprised that Incongruent hasn't taken a spin on this thread too...

https://www.rocketryforum.com/showthread.php?134445-TRF-Summer-Build-Off-SSC-Spiral-Spin-Can

KenECoyote said:

I forgot to note that I actually did start on one test prototype for this design...

First two flights weren't so good...way too heavy and draggy for the motors I used and there was significant damage on the second crash, so I've shelved for now; however I have another idea to make this one work and I may revisit one day.

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Very Cool!

Thanks Jim!

Here's one more pic showing the interior...fun little project! Except for the launches maybe. :wink:

I printed a scale paper model that I'm going to adapt to a 3" mailing tube. It should have been more like 3.25" but I am too lazy to scale the print or make a custome tube. I was thinking of having the lower 'capsule' merely be the angled strakes, kind of like the kit I tested. Or, I may just punt and fin it up.

rstaff3 said:

I printed a scale paper model that I'm going to adapt to a 3" mailing tube. It should have been more like 3.25" but I am too lazy to scale the print or make a custome tube. I was thinking of having the lower 'capsule' merely be the angled strakes, kind of like the kit I tested. Or, I may just punt and fin it up.

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Sounds good! Got any sketches? I'm having a bit of trouble visualizing.

I thought of trying this as a finned version with fins all the way to the top and the bottom open...would still be tricky, but should be better (and much easier) than the finless version.

For the finless version I'm now thinking upside-down "T" shaped vents to allow more airflow as well as add more base drag...plus have it spin...that along with bigger intakes may do it...hmmm...

KenECoyote said:

Sounds good! Got any sketches? I'm having a bit of trouble visualizing.

I thought of trying this as a finned version with fins all the way to the top and the bottom open...would still be tricky, but should be better (and much easier) than the finless version.

For the finless version I'm now thinking upside-down "T" shaped vents to allow more airflow as well as add more base drag...plus have it spin...that along with bigger intakes may do it...hmmm...

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This is 100% real-time design. The only idea that is off the table is a true GDS design. That nozzle looks to cool to get rid of. For a few minutes I considered a motor in the top and a metal cone suspended on the bottom so the exhaust streams over it.

rstaff3 said:

This is 100% real-time design. The only idea that is off the table is a true GDS design. That nozzle looks to cool to get rid of. For a few minutes I considered a motor in the top and a metal cone suspended on the bottom so the exhaust streams over it.

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Wow! That sounds really cool!

BTW - Upon further thought, the CSM model above likely has too big of a central tube...that by itself being so short and wide would be very difficult to get stable without giant fins extending out/down and the finless design isn't very efficient at stabilization.

Well, here is what I stuffed into Rocksim. Some dimensions are not that accurate and the mass distribution is fubar. There will be lead in the nose, yes, there will be lead. Basically 6 strakes with the bottom 1/2" open. I may add angled pieces inside the holes. Fins are TBD. Ack, the grandrocketeers just came over so no time to say more.

That looks awesome! I was thinking the same with the strakes (great minds...you know ); however I still think short & stubby needs a lot of fixing to fly stable...the CP is just too far forward to easily overcome, plus space for a chute (which a lead nose rocket should have) is wanting.

Still, I think one of us can do it!

I agree. Not much lever arm action there. Still, good base drag. Sooooo...I think I'll upgrade to a 24mm mount, add some nose weight, and see where I stand. 24mm or 18mm with adapter. Fins as a fall back.

rstaff3 said:

I agree. Not much lever arm action there. Still, good base drag. Sooooo...I think I'll upgrade to a 24mm mount, add some nose weight, and see where I stand. 24mm or 18mm with adapter. Fins as a fall back.

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I'm starting to think perhaps I'm approaching this in the wrong way...maybe I should add on fins (maybe half-size) and ensure it is stable and then slowly scale back the fins and adjust the intake/venting. Thinking of it in this way, the finned CSM would need honking big fins. :lol:

I admire you for approaching these designs so scientifically. I neither have the launch site availability, or the patience, to try multiple iterations. If I don't get something going in 2 tries, it seems to get on the permanent back burner.

I like KenEC's work on the finless design. It looks like the RAIStone has long slots in the side and flies well.

I also tried an Apollo capsule design about 6 years ago for a Club Christmas oddroc contest. It had clear base fins, but did not do as well as KenC's model. It had AA batteries in the nose cone to light up Rudolph's nose. The large model went up only about 10 feet and did cartwheels. The smaller model did a little better. Rocksim said that it was stable, but it was not. I did not check the Rocksim simulation to see if there was a minimum velocity for leaving the rail.

aerostadt said:

I like KenEC's work on the finless design. It looks like the RAIStone has long slots in the side and flies well.

I also tried an Apollo capsule design about 6 years ago for a Club Christmas oddroc contest. It had clear base fins, but did not do as well as KenC's model. It had AA batteries in the nose cone to light up Rudolph's nose. The large model went up only about 10 feet and did cartwheels. The smaller model did a little better. Rocksim said that it was stable, but it was not. I did not check the Rocksim simulation to see if there was a minimum velocity for leaving the rail.

View attachment 306046 View attachment 306051

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What was the diameter, weight and motors used?