The Finless Rocket Flies Again

I was just thinking about this again. I have always heard that at high enough speeds, that ring fins act like they are solid. So, uber high rod speed may not be optimal. If my statement is correct, a mostly plugged tube would act solid a lot faster. But, is this bad? I'm sure I don't have a clue about this and would just continue with testing. I think my mindsim just crashed and requires a reboot.

rstaff3 said:

Nice. As for the gas in GDS being exhaust, air is still a gas.

Click to expand...

Agreed! (",,,I don't know if that is correct either since "gas" in GDS also refers to exhaust gases. This design has more to do with airflow alone") :wink:

rstaff3 said:

I was just thinking about this again. I have always heard that at high enough speeds, that ring fins act like they are solid. So, uber high rod speed may not be optimal. If my statement is correct, a mostly plugged tube would act solid a lot faster. But, is this bad? I'm sure I don't have a clue about this and would just continue with testing. I think my mindsim just crashed and requires a reboot.

Click to expand...

Although I haven't read about that, I've been thinking almost along the same lines since at high enough speed, there would likely be enough pressure within the open tube to cause the top to deflect more air away from the inlet and then the front behaves almost like a solid cone; however I thought this was a good thing since it then allows the rocket some additional stabilization much like a large nose cone or like the finless rocket in the OP, but air would still be flowing through to the bottom outlets...in fact, I think with the slots at the bottom exhausting air, at higher speed there would be some venturi effect too and the lower pressure towards the bottom would also help to pull more air out through the slots. Besides, I wouldn't even consider high speed until I do some silly-fun LP tests...and I don't think my $1.65 Estes rocket will survive Mach.

Of course this is all just theoretical at this point for me, but until someone proves me wrong, I'll pretend I know what I'm mindsimming about.

You don't have a clue? I'm shocked since I think you're one of the most experienced rocketeers I know here! In fact, I visited your Rocket Dungeon (online website folks!) even before finding TRF. I think you need a Mindsim upgrade stat! Time to pull into BestBrain and trade in those Pentium chips. LOL

BTW - Anyone should feel free to try this design themselves. I currently don't have too many areas around me locally I know I can launch from, so I have to wait for the monthly launches and even then I don't know how many "experimental" launches I can do (plus they're weather dependent). Also I want to work on my scratch SpongeBob Fry Cook rocket. :grin:

If I wasn't similarly constrained about available launch days (I generally don't fly unless the ground temps will get into the 50's.) I would plagiarize your idea and build something myself. I still might...but not for a while. Do you have a build thread on Spongebob?

rstaff3 said:

If I wasn't similarly constrained about available launch days (I generally don't fly unless the ground temps will get into the 50's.) I would plagiarize your idea and build something myself. I still might...but not for a while. Do you have a build thread on Spongebob?

Click to expand...

Feel free to partake in design and testing! I'd be flattered! I don't have a build thread on SpongeBob, but will eventually (have the parts but have been putting off for half a year now).

BTW - I may start a separate thread on my finless design...I've probably stolen this thread for a bit too long. :wink:

I think my hijack of Daddyisabar's thread on GDS holds the record for the biggest hijack.

My latest though is the air gap section should be segmented so as it tilts the side opposite the tilt gets a bit more air. If the area is pressurized the same it might make less difference?

rstaff3 said:

My latest though is the air gap section should be segmented so as it tilts the side opposite the tilt gets a bit more air. If the area is pressurized the same it might make less difference?

Click to expand...

Yup, that was in my original design drawing!

The sketch shows it segmented into 3 sections...the dotted line represents the dividers going down through the shroud.

KenECoyote said:

Click to expand...

I've actually started building the Estes Converter today (have to leave now, but boy, this plan is looking really cool and at least the building is coming along even better than planned...you'll see). :grin:

So it was

rstaff3 said:

So it was

Click to expand...

No problem Dick...I do the same all the time. Shows you have a busy mind with lots of things going on...well, at least that's my excuse!

Hope all goes well on test day, we are expecting a video.

KenECoyote said:

Good question! I initially considered recessing the motor mount to allow for GDS (Gas Dynamic Stabilization - as noted in Apogee newsletter on finless rockets); however now I think I'll have the motor flush with the bottom so I can see the results of the design separate from other stabilization factors.

Still thinking of names...I think you have an upper hand on this one! Candle would be an amusing possible design, but I'm thinking more like the front end of this :

Click to expand...

The MIG 21 will make a great rocket, a lot like the F-104.

KenECoyote said:

Still thinking of names...I think you have an upper hand on this one! Candle would be an amusing possible design, but I'm thinking more like the front end of this :

Click to expand...

"Scram"

Click to expand...

Nice.

I might want to watch its maiden flight from an armored bunker, but nice. (my mindsim has started crashing whenever I open up this design)

Silverbrewer said:

Hope all goes well on test day, we are expecting a video.

Click to expand...

Will do! However it may be a while and likely will be a grainy phone video.

neil_w said:

"Scram"
Nice.
I might want to watch its maiden flight from an armored bunker, but nice. (my mindsim has started crashing whenever I open up this design)

Click to expand...

LOL! You shouldn't be too worried...my triple threat of traits helps to limit the risk. I hate errors, I like methodical testing* and I have some pride in having a lot of successful flights. In fact, each time I make an error, I punish myself repeatedly by replaying the scenario in my mind and determining how I can avoid the same again. Self-deprecation is a good motivation for not repeating errors. Now watch that since I've said this I'll be doing power-prangs left and right (on the opposite side I have a wacky sense of humor). :wink:

*There's a reason I've chosen the Estes Converter to use as a base for testing. I can have it full length with all 4 sections and just the bottom with the mod first. If that works, I can then modify it so that I have 3 sections with bottom shroud, then 2 sections with bottom shroud, then 3 sections with 2 bottom shrouds, then 2 sections with both shrouds (assuming all flights are sequentially successful). The first test shouldn't be too worrisome since the CP should be well behind CG and it looks like a rocket with a ring-like rear fin.

Just an update that since I'll be doing a build thread for this, I've started a new one here: https://www.rocketryforum.com/showt...n-Ram-Air-Stabilization&p=1540939#post1540939