"Finless" Rocket Design - Ram Air Intake Stabilization?

rstaff3 said:

...I hope there is more progress this weekend...

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Nope, sorry. Checked the ice and it's way too thin. I may be able to launch next weekend at a club launch (maybe after everyone else leaves); however the long range forecast is saying a low of 5F and a high of 20F that day, so that may be too cold for me to go for an all day launch.

Knock, knock...

Who's there?

Sorry...I'll update in about a few weeks to a month...been really, really busy.

Okay, here's an update...

Key points:

• I've done many designs and tests since the initial idea.
• The design is an amalgamation of things including weighted nose, cone base/annular base, tube fin, etc.
• Given all these "ingredients", it becomes much like a recipe...too much salt or too little sugar and it's a tough bite to swallow.
• Additionally, with each element added, the variations to test become an incredibly high number. You can test 10 fins on one rocket and it's 10 variations...test 10 fins each on 10 different rocket lengths and it becomes 100...add a third variable of 10 different nose weights and it becomes 1000 possible combinations...a lot of stuff to test!
• Nose weight will be significant...how much? Well, that's still being tested. I'd like less if possible, but then it becomes less stable. Additionally, due to the small main body tube and heavy nose, recovery space is a premium. I doubt Estes would be interested in this oddroc design given that and the unpredictability of how a builder will build it.
• Testing is a real pain since there's likely 9+ failures for every success*.
• I've still got a bunch of ideas and designs to test; however at this point I may have to scale back since I've been putting aside a lot of other fun things (and I'd like to work on my L3 and will participate in a local club drag race special) in exchange for a project with ~10% success; However I do have a design which is promising, so I've already recruited a few friends to help me test. I'm trying to work on final testing of how much nose weight...I'd like to get it down, but it's been really tough.

*For those times it has worked, it's been great...almost amazing. I recently launched at my local club and it's amusing to see well-experienced rocketry veterans exclaim "WOW...it's stable!". However following that up with a cruise missile/sky-writing test rocket kind of resets things again. :wink:

Well, keep at it. I am always impressed with people who spend the time to try a range of options to determine what the range of parameters result in a working design.

rstaff3 said:

Well, keep at it. I am always impressed with people who spend the time to try a range of options to determine what the range of parameters result in a working design.

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Thanks Dick! Very much appreciated!

wow . nice jop

MostafaAwad said:

wow . nice jop

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Thanks! However I'm hoping you meant "job" since I've just looked up "jop" on the urban dictionary and it's not good... :wink:

Quick update:

My best test results came from heavily weighted nose cones (think full of bb's and epoxy). Prior to that, I had a lot of unstable versions and the heavier weight seemed to give the design a very nice straight flight. RStaff3 suggested to me to try the design with the vents closed to see if the rocket was stable with just the weighted nose. I didn't think it would be considering my experience with the design; however I tried it and it was stable! In fact, more so that I had expected after reading and researching it a lot. Go figure.

This is a tricky situation and I would've preferred to give it less nose weight, but doing so means less stable/predictable flights, so right now this design doesn't look so good since it is also aerodynamically inefficient. For now I'll put this on the back burner since I have a few more ideas going on and want to focus on other things right now (TRF Summer Build Off and L3!).

To be continued...

Was great to watch through this thread, turned me onto some interesting research. Kudos for trying something!

dhbarr said:

Was great to watch through this thread, turned me onto some interesting research. Kudos for trying something!

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Thanks! I'm hoping to revisit this one later; however there seems to be even more variables than I initially considered...even the nose cone shape and distance from the intakes can cause a change of airflow into the shroud. Gonna take a lot more testing to get this one working well.

Also you got my thinking...I may try a design with some fins on the outer shroud, but a spinning turbine inside the shroud and flow out the back...the turbine if weighted may actually act like a gyro stabilizer (at least my mindsim says so). :wink:

This is a very nice idea, I am doing millitary scale rocket building, would like to have fin or even finless rocket design.

KenECoyote said:

Thanks! I'm hoping to revisit this one later; however there seems to be even more variables than I initially considered...even the nose cone shape and distance from the intakes can cause a change of airflow into the shroud. Gonna take a lot more testing to get this one working well.

Also you got my thinking...I may try a design with some fins on the outer shroud, but a spinning turbine inside the shroud and flow out the back...the turbine if weighted may actually act like a gyro stabilizer (at least my mindsim says so). :wink:

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Either the turbine will have to have a solid amount if mass (as you said) or be spinning really fast to be an effective gyroscope. Or both. Says mindsim. Mindsim also says: Fast spinning heavy turbines tend to break!

But the gyro will not re-adjust the rocket, it'll only slow down change and give the skywriting interesting properties.

Weighted turbine? At the back? That's no good.

Why not a spinning fin can? Same thing, really...
Ogive or parabolic should be best for directing airflow.

modeler said:

This is a very nice idea, I am doing millitary scale rocket building, would like to have fin or even finless rocket design.

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Start out with fins, it's a lot easier and looks better, in my opinion. But as you advance in rocketry, you can try finless designs. Also start out on a launch pad. Much less damage in case of a mishap and much more stable base.

Incongruent said:

Start out with fins, it's a lot easier and looks better, in my opinion. But as you advance in rocketry, you can try finless designs. Also start out on a launch pad. Much less damage in case of a mishap and much more stable base.

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I agree. Too much to be done and learned with so many types of rockets. Always test your crazy ideas so as not to damage people or property.

modeler said:

This is a very nice idea, I am doing millitary scale rocket building, would like to have fin or even finless rocket design.

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Incongruent said:

Start out with fins, it's a lot easier and looks better, in my opinion. But as you advance in rocketry, you can try finless designs. Also start out on a launch pad. Much less damage in case of a mishap and much more stable base.

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rstaff3 said:

I agree. Too much to be done and learned with so many types of rockets. Always test your crazy ideas so as not to damage people or property.

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I agree 100%. This project has proven to be many, many times harder than I thought it'd be! :bang:

Incongruent said:

Either the turbine will have to have a solid amount if mass (as you said) or be spinning really fast to be an effective gyroscope. Or both. Says mindsim. Mindsim also says: Fast spinning heavy turbines tend to break!

But the gyro will not re-adjust the rocket, it'll only slow down change and give the skywriting interesting properties.

Weighted turbine? At the back? That's no good.

Why not a spinning fin can? Same thing, really...
Ogive or parabolic should be best for directing airflow.

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Actually, the mindsim was for a weighted turbine forward at the front of the shroud (just aft of the nose cone) and the air vented out through outlets at the bottom of the bt.

Funny you should mention "spinning fin can"...check out my Summer build-off project (still ongoing and will be revisited & updated by spring).

KenECoyote said:

Actually, the mindsim was for a weighted turbine forward at the front of the shroud (just aft of the nose cone) and the air vented out through outlets at the bottom of the bt.

Funny you should mention "spinning fin can"...check out my Summer build-off project (still ongoing and will be revisited & updated by spring).

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Have you heard of rollerons? They're like waterwheels (but for air) mounted on fin flaps and work as gyroscopes to passively turn the fin flaps if the rocket rotates to keep a rocket from spinning. It's used in addition to active guidance, e.g. canards.

Incongruent said:

Have you heard of rollerons? They're like waterwheels (but for air) mounted on fin flaps and work as gyroscopes to passively turn the fin flaps if the rocket rotates to keep a rocket from spinning. It's used in addition to active guidance, e.g. canards.

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Ken, you better look out for this kid... He knows about rollerons. I had to go work on AIM-9 missiles to find out about those. Then again, we're separated in age by decades, and information sharing has gotten a lot better in the intervening years.

Tony, that's a very good description of them. I can tell, you're going to go far in this hobby. Keep It Up!

K'Tesh said:

you're going to go far in this hobby.

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Well, until the funds dry up. Which is hopefully not soon, still got a really big Nike Smoke to build. I think I'll adapt the Estes PS II or 1/10 scale one first, once I get to high school when I'll be able to maybe use a real chemistry lab where the fume cupboard isn't just an extra storage cabinet (seriously... )

The high school that I plan on attending is has a machine shop too. You know what that means...


Before I found TRF I binge read Wikipedia pages.

Now instead on just knowing trivia I can talk about it to other addicts!

Agree on information availability.

Now I'm paranoid that I'll forget about rollerons... with all this other information


Thanks for the word of encouragement,
-Tony

K tesh. In another couple of months he is gonna have more posts than you!

Lowpuller said:

K tesh. In another couple of months he is gonna have more posts than you!

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I spend way too much time on TRF. But I spend too much of that typing out long replies. If I do short ones such as this, I'll get post count up much faster.

-Tony

Incongruent said:

I spend way too much time on TRF. But I spend too much of that typing out long replies. If I do short ones such as this, I'll get post count up much faster.

-Tony

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The downside is that you can tell I am a blathering idiot.

-Tony

Incongruent said:

Have you heard of rollerons? They're like waterwheels (but for air) mounted on fin flaps and work as gyroscopes to passively turn the fin flaps if the rocket rotates to keep a rocket from spinning. It's used in addition to active guidance, e.g. canards.

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Actually, I was aware of rollerons...I studied Aeronautical engineering in HS and also built a lot of military models and used to wonder what the funny wheels at the end of some missile fins were, so I looked it up one day.

Incongruent said:

The downside is that you can tell I am a blathering idiot.

-Tony

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Speaking from personal blathering experience, that makes you fit right in with TRF :wink:

K'Tesh said:

Ken, you better look out for this kid... He knows about rollerons. I had to go work on AIM-9 missiles to find out about those. Then again, we're separated in age by decades, and information sharing has gotten a lot better in the intervening years.

Tony, that's a very good description of them. I can tell, you're going to go far in this hobby. Keep It Up!

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I agree! Very impressive posts! :clap:

Incongruent said:

The high school that I plan on attending is has a machine shop too. You know what that means...
..
Now I'm paranoid that I'll forget about rollerons... with all this other information

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Capitalize on the machine shop as much as you are allowed to. Its a great resource that can save you a lot of money if you know how to mill/lathe/weld.
I regret not pursuing Hi-power while I had access to the shop during college (engineering research asst. job ftw). Although in college I couldn't afford to get fancy anyway. Lessons learned..

I saw an IREC team try rollers on spring-flexed fins in UT this year. They wanted to compare that flight to a flight with conventional fins, but that became impossible when their launch vehicle went down nosefirst in a rock canyon.

KenECoyote said:

I agree! Very impressive posts! :clap:

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Thank you.

Nytrunner said:

Capitalize on the machine shop as much as you are allowed to. Its a great resource that can save you a lot of money if you know how to mill/lathe/weld.
I regret not pursuing Hi-power while I had access to the shop during college (engineering research asst. job ftw). Although in college I couldn't afford to get fancy anyway. Lessons learned..

I saw an IREC team try rollers on spring-flexed fins in UT this year. They wanted to compare that flight to a flight with conventional fins, but that became impossible when their launch vehicle went down nosefirst in a rock canyon.

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Agree on the machine shop use. I am actually quite lucky- in the public high school in my town has, there's a solar car team, I'm not sure whether because of that or in addition to that, they have a machine shop. I've heard that they have a laser cutter, CNc, lathe, 3D printers... basically everything I need for machining. And near me, there's a Makerspace which probably has as much if not more. The high school has classes on the machinery too.

I'm not sure about a welder.

Too bad the IREC rocket crashed, but my understanding is that without active guidance, rollerons are detrimental to altitude gain. They constantly change the rotation of the rocket, and without the spin (which is much less draggy once it gains enough angular momentum), the rocket leans over easier and that cuts down on altitude as well, especially for smaller rockets.

That at being said, I would like to experiment with rollerons, though problably in a wind tunnel.


-Tony

Other than the Sidewinder, I don't know of where else they have been used. Like forward mounted fins, I suspect their purpose is tied to the need for the rocket to change directions quickly.

rstaff3 said:

Other than the Sidewinder, I don't know of where else they have been used. Like forward mounted fins, I suspect their purpose is tied to the need for the rocket to change directions quickly.

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The Sidewinder was where rollerons were first used, but I believe they've been used in other places too. The purpose is to counteract spin to active guidance can function properly. If you imagine tracking an object from a spinning rocket, you can see how the spin would be problematic, and trying to turn the rocket and factor in the fluctuating spin rates is very read impossible. If you can't, get a launch video where the fins aren't perfectly straight and keep your eyes on one item.

Incongruent said:

That at being said, I would like to experiment with rollerons, though problably in a wind tunnel.

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For a model rocket, I would think that it would be very difficult to do since you need significant mass for a noticeable gyro effect and mass on the rear end is bad mojo. Additionally, there are so many other factors affecting the flight of a model rocket which likely have much more effect that it would be hard (and $) to make a precise enough rocket that goes fast enough for those gyros to have any significant effect.

...so says my mindsim. :wink:

However, I think having "spinning wind paddles" in place of fins on a rocket would be mad-fun and likely would be a cool sounding flight, but landing damage may be an issue there (rear chute ejection?). Dang...you guys keep popping ideas into my head faster than I can build them! :tongue: