Helix: Tractor Motor - Helical Finned - Rear Eject

[lakeroadster]

Here's a rocket that uses a helix for a fin, has tractor motors up top, and uses rear eject for the laundry.

It's similar to George Gassaways Tractor Helix rocket (front engine rocket that spins) project, except it has the helix for a fin.

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[BABAR]

its interesting your occupation’s effect on your interpretation.

I’d end up calling this one Cancer. Or Chemotherapy. The helical stuff looks like DNA. The tractor motor motors (unless canted out, @Daddyisabar -style) will break the DNA strands, which interestingly enough can either cause or cure cancer.

the physics of the helical fins is probably not all that different from the three staged rocket with the spaced out multiple thin rings. Waaaay to complicated for me, but confident predictions as follows:

draggy as heck.

looks like plenty of surface area Even for a rear motor job, with tractors I suspect nearly infinitesimal fins would be enough.

less Likely to weathercock (i think this is a common plus For ring and tube finned birds.)

 

[kuririn]

Are you going to slightly cant the helical fin supports to induce a mild corkscrew going up?
That would be cool.

 

[lakeroadster]

Are you going to slightly cant the helical fin supports to induce a mild corkscrew going up?
That would be cool.

Cool indeed.... The motors will be canted and offset so it will indeed corkscrew on the way up. Think "Deuces Wild"... but tractor motor style.

And I forgot to mention the center mounted launch lug...

 

[lakeroadster]

its interesting your occupation’s effect on your interpretation.

I’d end up calling this one Cancer. Or Chemotherapy. The helical stuff looks like DNA. The tractor motor motors ... will break the DNA strands, which interestingly enough can either cause or cure cancer.

Cancers a bitch... I wouldn't call anything "cancer", or "chemotherapy"... simply out of respect to all those who have lost their fight with it.

Much Respect

 

[Daddyisabar]

Tractor motors pulling up a long strand of DNA. Pull up multiple spiraling coils of self replicating DNA. Would have to be yucky front deploy though, if you didn't want the ducted rear eject motor mount to blow through the coils. Could the tail or coils be considered streamer recovery?

What's that Mr.RSO? The Polybasic Furin Cleavage Site has been lab modified? You want to see the kit face card to determine country of origin...OPPSIE, gotta skedadle before the big black unmarked SUV's show up!

Tractor motor oddroc "Gain of function research" is no excuse. No funding for such dangerous endeavors.

 

[lakeroadster]

Helix Day 01

Cut the helix using a cut off wheel and a die grinder...

 

[teepot]

I wondered how you were going to make the helix. Kind of like a Slinky. Yours flew didn't it? I haven't flown mine yet. I keep forgetting I have it.

 

[lakeroadster]

I wondered how you were going to make the helix. Kind of like a Slinky. Yours flew didn't it? I haven't flown mine yet. I keep forgetting I have it.

Not yet... just started on it yesterday.

But if you're talking about The Cygnus Probe... it's flown twice, semi-successful both times. It has a stability problem except when it is under power.

I added an upper body section, and it's slated to be launched once again.

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[lakeroadster]

Nose Cone

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[techrat]

I hate when this happens.... but you've got me thinking now...
With a tractor motor, how high could you put fins and get away with it? I'm thinking of a rocket in reverse, with the motor near the "nose", fins way up high near the motor, a long body tube which ends in a rear-facing nosecone with rear eject. So during launch, the rocket looks like it's going backwards because from the point of the viewer, the nosecone is pointing down.

 

[BABAR]

I hate when this happens.... but you've got me thinking now...
With a tractor motor, how high could you put fins and get away with it? I'm thinking of a rocket in reverse, with the motor near the "nose", fins way up high near the motor, a long body tube which ends in a rear-facing nosecone with rear eject. So during launch, the rocket looks like it's going backwards because from the point of the viewer, the nosecone is pointing down.

Not sure where I saw it, maybe rocketreviews, maybe here. Was a rocket with clear nearly invisible fins on the tail, small fins on the nose, built to look like a rocket upside down. I think it did have a normal rear motor mount, however.

 

[BABAR]

Cool indeed.... The motors will be canted and offset so it will indeed corkscrew on the way up. Think "Deuces Wild"... but tractor motor style.

And I forgot to mention the center mounted launch lug...

Ahhh, that explains the hole in the nose cone!

 

[Daddyisabar]

I hate when this happens.... but you've got me thinking now...
With a tractor motor, how high could you put fins and get away with it? I'm thinking of a rocket in reverse, with the motor near the "nose", fins way up high near the motor, a long body tube which ends in a rear-facing nosecone with rear eject. So during launch, the rocket looks like it's going backwards because from the point of the viewer, the nosecone is pointing down.

Clear your mind to avoid the temptations and pitfalls of the dark side.

As a relative newbie I put me fins on top of the tractor motors because it looked really cool.

I then took the tape worm to a prestigious national event. The RSO was a local prefect and had seen it fly several times, so I "hooked" him into a pad assignment.

Went out to the six foot, quarter inch rod pad with a totally newbie mom and her kids who were very interested in a silly rocket, this being their first big launch. Came back behind to the two guys at the LCO table and seeing another friend I joked "Look what the kids are flying these days! Parasitic Worm flying fun for the whole family!" He was very amused but seemed a bit nervous.

After a successful flight I later learned of the preflight conversation at the launch table between the Highly experienced LCO and a TOP MAN who had come over to check out the sport range. I should not have joked about any canted tractor motors with forward mounted fins at that particular time.

Such impure thoughts of tractor motored abominations can draw the attention of the though police and can lead you astray. Rockets are not meant to fly backwards. A wise man once told me to keep the motors and fins at the back of the rocket...WHERE THEY SHOULD BE! Stay on the straight and narrow path and learn the ways of the Jedi.

Though the dark side is really fun and you can fly the rockets you love.

 

[Daddyisabar]

Not sure where I saw it, maybe rocketreviews, maybe here. Was a rocket with clear nearly invisible fins on the tail, small fins on the nose, built to look like a rocket upside down. I think it did have a normal rear motor mount, however.

I have a drawing of a "Which way is up?" rocket in a box on the shelf behind the shame curtains. Utilizes spent 29mm single use composite motors to look like traditional 3-4FNC but with integrated canted tractor BP motors. No lexan. Afraid to build and fly it. Fear is the mind killer. Maybe another of Lakeroadster's successes will give me the confidence to once again fall off the reformed Jedi wagon and get back into dabbling in the dark arts.

 

[Daddyisabar]

Helix Day 01

Cut the helix using a cut off wheel and a die grinder...

View attachment 593470View attachment 593471

Will the mount allow any spring or variable geometry? Will the helix be stiffened? So much fun with tractors when you don't need any fins and they can just be good looking Greebles.

 

[Steve Shannon]

I hate when this happens.... but you've got me thinking now...
With a tractor motor, how high could you put fins and get away with it? I'm thinking of a rocket in reverse, with the motor near the "nose", fins way up high near the motor, a long body tube which ends in a rear-facing nosecone with rear eject. So during launch, the rocket looks like it's going backwards because from the point of the viewer, the nosecone is pointing down.

No matter where the motors are your Center of Gravity must be ahead of the center of Pressure.

 

[lakeroadster]

No matter where the motors are your Center of Gravity must be ahead of the center of Pressure.

Not for a tractor motor powered odd roc... it flies in the face of conventional rocketry protocol.

 

[lakeroadster]

Will the mount allow any spring or variable geometry? Will the helix be stiffened? So much fun with tractors when you don't need any fins and they can just be good looking Greebles.

We'll see. The fins mount to the fuselage with 3/16" dia. dowels, every 90 degrees, for it full length. The helix portion is 1/16" th, but it is pretty flimsy. I thought about doubling up the thickness, which I can still do afterwards.

 

[BABAR]

Not for a tractor motor powered odd roc... it flies in the face of conventional rocketry protocol.

I dunno, I think I am with @Steve Shannon on this. The tractors definitely help by putting more weight (namely the motor casing and propellant) forwards to advance the CG. .

I believe @Daddyisabar ‘s rockets have long and draggy tails that generate a lot of drag and CP force.

You can come up with extremely unconventional ways to MEET the physics requirements, but you can’t successfully violate them.

 

[Steve Shannon]

Not for a tractor motor powered odd roc... it flies in the face of conventional rocketry protocol.

Not really. Everything obeys physics. For rockets, the motor is frequently a significant mass. Mounting the rocket motor forward moves the center of mass forward and everything works just fine. A stick rocket is that way.
But if the center of pressure is ahead of the center of mass, lift, operating through the center of pressure, will attempt to rotate the rocket around the center of mass (AKA center of gravity) until the center of mass is ahead of the center of pressure. Even if the force of a tractor motor can overcome that rotational force, as soon as the thrust ceases the rocket is back to simply being an object with a Cp and a Cg.

 

[BDB]

I hate when this happens.... but you've got me thinking now...
With a tractor motor, how high could you put fins and get away with it? I'm thinking of a rocket in reverse, with the motor near the "nose", fins way up high near the motor, a long body tube which ends in a rear-facing nosecone with rear eject. So during launch, the rocket looks like it's going backwards because from the point of the viewer, the nosecone is pointing down.

My daughter and I tried something like this. We make a "reversible" rocket that could be flown conventionally or in reverse using with canted tractor motors that were mounted on the fins. We made it with a long airframe and a nosecone at the "bottom" when flown in the reverse orientation. OR and Rocksim both hated it, but we were able to get CP behind CG due to the length of the rocket. (We had to use the cardboard cutout method to approximate CP.) My logic was that it would behave like a bottle rocket with a motor at the top and a long stick protruding aft.

Well....my logic was wrong. But it was an "interesting" flight! It was stable-ish as it left the rail, but as the propellant burned, CG moved in the wrong direction, and the rocket started to skywrite.

Here's a thread about the design and build of the reversible rocket. It looks like I didn't finish the thread with a flight report. I need to find the video of the ill-fated flight to post it: https://www.rocketryforum.com/threads/esthers-awesome-reversible-rocket.158544/

 

[lakeroadster]

Not really. Everything obeys physics. For rockets, the motor is frequently a significant mass. Mounting the rocket motor forward moves the center of mass forward and everything works just fine. A stick rocket is that way.
But if the center of pressure is ahead of the center of mass, lift, operating through the center of pressure, will attempt to rotate the rocket around the center of mass (AKA center of gravity) until the center of mass is ahead of the center of pressure. Even if the force of a tractor motor can overcome that rotational force, as soon as the thrust ceases the rocket is back to simply being an object with a Cp and a Cg.

I have built a rocket, Thunk! , that used Gas Dynamic Stabilization. At launch the Cp was ahead of the Cg, and it flew just fine.

I get your point, but there are ways around the standard 3/4FNC configurations, and that's what I find interesting.

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[Steve Shannon]

I have built a rocket, Thunk! , that used Gas Dynamic Stabilization. At launch the Cp was ahead of the Cg, and it flew just fine.

I get your point, but there are ways around the standard 3/4FNC configurations, and that's what I find interesting.

View attachment 593900View attachment 593901
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I absolutely agree; spinning a rocket is one way to achieve stability and other techniques can be used to counteract lift rotating the rocket if Cg is behind Cp. Gyroscopic stability overcomes the ability of lift rotating the rocket about the center of mass. But it still must follow physics. And it may be that this helix will result in that same kind of spinning. Of course spinning can bring with it other problems. I built a rocket and added excess spin to it and the polycarbonate body tube folded on the way up. It was an interesting flight.

 

[Bruce]

 

[BABAR]

View attachment 593912

Okay, that’s just teasing’!

Details please!

We’re there Lexan fins?

Also, anything can be made to fly straight to the end of the rail. It’s what happens in the NEXT few seconds that matters.

Thanks!

 

[Bruce]

No Lexan fins.

It has flown successfully 3 times now. Flight profile is not perfectly straight, but parachute always deploys while it is still above ground.

 

[lakeroadster]

No Lexan fins.

It has flown successfully 3 times now. Flight profile is not perfectly straight, but parachute always deploys while it is still above ground.

That's impressive... straight up while guided by the launch rail, less than 10 ft above the ground....

Got any more photo's of straight up while not on a rail?

 

[BABAR]

That's impressive... straight up while guided by the launch rail, less than 10 ft above the ground....

Got any more photo's of straight up while not on a rail?

Inertia?

 

[Bruce]