FINLESS ROCKET DEBATE why does the Aries1-x have no fins?

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Very... VERY early models reflect the finless no LES designs. These were only illustrations of the yet-to-be completed thinking pattern however. Most were made prior to the STG's concept of launch escape that led to the Mercury tower. In the very early planning stages, believe it or not, no one actually considered escape.

You'll also see some early drawings of the Saturn C-5 (later renamed Saturn V) that show the S-I-C stage without fins and still others with the fins on the S-I-C body between the engine fairings rather than on the fairings. In the NASA publication to Congress titled "Manned Space Flight -1963" that accompanied Holmes' testimony before Congress in March and April 1963, there are a large number of these drawings- all dated 1963 (indicating that they were drawn and published in great haste in order to have them ready for Congress.)
Cool! That's great info Doc!!!

I always wondered why the Saturn I Block I didn't have fins, and had that weird aft structure.

Of course those early Saturns looked kinda weird in flight too, with all that turbopump exhaust just dumped overboard belching flame everywhere like the old Atlas used to...

The later Saturn I's with the aspirators on the nozzles to get rid of the turbopump exhaust look SO much nicer lifting off...

Later! OL JR :)
You were all wrong!! I copied a Aries 1 x design and by movin th engine really far forward it was stable in flight!!!
You were all wrong!! I copied a Aries 1 x design and by movin th engine really far forward it was stable in flight!!!
More information? Post pictures??? I'm not clear on what you did, and whether what you did was consistent with the scenario that you originally asked about.

You were all wrong!! I copied a Aries 1 x design and by movin th engine really far forward it was stable in flight!!!

One problem... having the motor far forward inside the body tube will mean that the thrust is forced through the long aft section of the tube. That means you'll roast the tube and cause structural failure within a few flights, and also that the thrust will be reduced to a very small amount - prolly less than 10% - of its nominal value.
That was the test flight and I accounted for the reduction in thrust by using a d21-4 and I aslo kept it as a minimum diamiter design I plan on flying on more time before retiring it. And the ege I found a double delta wing is the most effective for supersonic flight and adding a boattail will increase speed by about 12 miles per hour!
Does anyone know where I can get a rocket locater that beeps? Oh and it has to be under 9 grams with battery. I have a supersonic rocket and weight is key

Note: that the individual posting that opinion is only mostly right but does not cite a source for his Boeing opinion. I've done a lot of digging on this subject and never found ANY documentation to support his, and other's, opinion about thoughts of deletion of the Saturn V fins- it is, as far as I have found, just a popular myth.

To find what I said you can look in NASA publication MPR-M-SAT-61-5 (NASA-TM-X-69174) p.208, section 13.1 paragraph 2. There are no "I heards" involved.
The problem is that when you fly a cylinder with a nosecone, the airflow separates from the body near the nose even at a small angle of attack, so the center of pressure moves a lot farther forward than you would expect. It's nowhere near the geometric center of the rocket. A friend of mine demonstrated this (unintentionally) by flying a long, skinny, finless rocket with a very heavy nosecone. The result was a 90 degree turn shortly after leaving the pad. Unless you're using spin stabilization or active thrust vector control, there's really no amount of noseweight that will make a purely cylindrical rocket safe. The simulated solid strap-on boosters in the above examples are effective enough at acting like fins, that the rockets fly o.k.

As usual- Adrian A has this question correctly answered in full. AOA is the key here and any type of sideload at all sets the chain in motion.

This was how I solved the issue of first stage instability with my drop off SRBs in the Mark II Stage Zero. I tried everything from huge fins to almost no fins to weights in the nosecones of the SRBs and still the first stage boost was unstable- it required some thought.

Then, while watching some slow motion Saturn launch videos, I recalled a discussion I'd had back in college with one of the Aeronautical Engineering students concerning airflow along cylinders- which included those with nosecones. He had told me how in the wind tunnel, subsonic flow was very hard to get going straight down the cylinder. Any outside forces or the slightest AOA would cause the airflow to spiral around the cylinder. Sure enough, the airflow going over those big Saturns as the lifted off were spiral. So, I concluded that this same force was upsetting my first stage boostes- and since there was a 3/16 gap between the SRBs and the main tube, that flow may be the cause of the instability. I added a simple fence between the bodies and bingo- problem solved.
So basicly the only reason the dr zooch
model of Aries 1-x flys Is beacause of the flame fins in the rear?
So basicly the only reason the dr zooch
model of Aries 1-x flys Is beacause of the flame fins in the rear?


In fact I developed FlameFins for the Atlas, but they are best applied to Ares I-X/I as those two kits get the best boost using them. The original Ares I had small fins in its proposal, and I originally applied them to the model, but had to increase the size by 31% to get any stability and 38% to get an envelope that would allow me to sell the kits.
So it's a very bad idea to fly them even with a super heavy nose weight?
Yes it is bad to fly any rocket without some sort of control surfaces. Another option other than fins is drag stabilization like a cone attached to the base or the airframe shaped as a cone like the Semroc Point. I'm building a model of the N-1 that has no fins but is basically a narrow cone. I wonder how big the aft skirt on the SRB would need to be to provide stability.
Longitudinal features like strakes and wiring tunnels also provide some directional stability but not much. I recently found a design on EMRR in an old descon that used 2x18mm as main boost and 2x13mm set at an angle to rotate the airframe. According to the designer it flew relatively straight for 150-200 feet and then went unstable. It's likely that as soon as the mini motors burned out, the rotation slowed causing the rocket to go unstable.
I've recently built but not yet flown a rocket with a hollow nosecone and being unsure of the NC's effect on stability I opted to spin stabilize the rocket using heavily airfoiled fins. I also built a rocket with an asymmetrical cluster and spin stabilize it to ensure safe flights. I wish I'd known about spin stabilization before I wrecked my SRX.
Really you can stuff a rocket motor in anything but the question is can you predict what will occur? That's why they call it rocket science not rocket art. Ted
Actually, you won't be "flying" the Ares I-X without the FlameFins- you'll instead be setting off and single use cartwheeling firework... Chinese New Year is today I believe. Do not celebrate in this manner.

Keep in mind that there are may elements in the dynamics of rocket flight stability- and CG ahead of CP is only one- static- element. Once things go into motion- all best change as a lot of other factors come into ply in the dynamics of that motion in the airmass.
check this out with a 4 oz nose weight the rocket will fly soundly i have rocksim file to prove it
You cannot "prove" a design with RockSim, or even with a wind tunnel. You have to actually build one and fly it to "prove" that it works.

There are simply too many ways to "trick" RockSim to be able to rely on it as "proof." Plus once in awhile it is just plain wrong. See if you can find out what's wrong with this popular design that has been on the market for years. (Hint: watch the 2D flight profile.)

There is nothing actually wrong with the actual kit, BTW.


View attachment quest_totallytubular Rocksimmed.rkt
And they expect us to pay $120 dollars? Or $1000 for the RS-pro?:jaw:

Rocksim and its ilk are designed for conventionally finned rockets, and that's where they are most accurate. They can handle transitions, multiple fin sets, staging, and clustering very well.

When you start adding more fins, or side pods, things get complicated. When you add tube fins, or have no fins at all, things get very very weird. The mathematical equations are only approximations, and the programs don't always get them right. Rocksim does a very good job, even with some very complex models, so it's well worth the price.

Simulation programs also model perfect rockets. They assume that you are skilled enough to have the fins canted 0.000 degrees, that the nose cone fins straight on the axis, that the fins are the exact same shape down to the thousandth of an inch, and that the motor's nozzle is mathematically perfect. Except for the best scale modelers, that doesn't happen, and even then they have tiny imperfections. Those imperfections don't matter much with stable finned rockets, which have nice corrective forces. But with something like your Ares I-X model, with no fins, the tiniest imperfection in building or uneven thrust, or a tiny bump that breaks the laminar flow, could easily send it unstable no matter how good your simulation program is.

That's where personal experience comes in; my simulations show that my 24mm saucer is unstable, and yet I know it flies straight, and will trust it to always fly straight. (Base drag, which stabilizes saucers, pyramids, and stools, is rather difficult to simulate). The RSO knows better than the sim program, in many cases.

As someone who has written their own program, I can tell you that it takes a lot of work. Mine is just a basic RASP-style program that calculates based on weight, diameter, and drag coefficient, with a few other minor functions; it has maybe a hundredth the functionality of Rocksim or even Openrocket. It's written in TI-Basic, quite possibly the easiest programming language on the planet. It's taken me some 80+ hours writing and improving it and another 10-20 hours making the motor data files. These simulation programs are incredible pieces of work, and it's amazing that they cost as little as they do.
+1 to what EGE said. RockSim is a great program; no doubt about it. But it is based on mathematical modeling; it is not a database of real-world design elements and real-world flight events. (It would be many, many times more expensive it it was.) It has had so many updates because the programmers are continuing to tweak the algorithms to better match reality as well as adding more algorithms to model more and more features of actual rocket designs. RockSim 9, for instance, just added the ability to model side pods. It can be quite accurate, but you still need to verify what it predicts by using real-world tests of the design. The program is excellent, and RS-Pro is even more so, but even Apogee Components would never claim that it is infallible. The things that I was trying to emphasize are that the quality and accuracy of its predictions are largely dependent upon how well the settings you give it match up with your actual situation (e.g., your actual field conditions) and how accurately your design matches the rocket that you will actually build. Yes, RockSim has some features that are not yet fully implemented or perfected, but these play a minor role in its usefulness and generally only apply to very specific (and unusual) circumstances. But in no case can it give you good predictions unless you feed it with good data. And even with that, no mathematical modeling system can completely take the place of real-world testing. After all, the real world is where you will be flying your rockets, not inside a mathematical equation.

*In my best french accent
*ends accent
i see your point these programs run it under IdEAL conditions that nothing in the real world would have, and rocksim is for designing rockets NOT a cart of fireworks :) i guess sometimes you have to put some logical sense in them:eek:
Second to what EGE and Mark II said...

There is also the "garbage in, garbage out" syndrome...

You have to be careful in Rocksim or you can 'fool' it into giving you the results you WANT to see, instead of the REAL results you'll see on the flying field. There are a few 'gotchas' that can make you think you're really 'on the money' and then when you load her up and fly her you end up getting caught with your pants down! Check out the "Mercury Joe" site about their "M" powered (IIRC) flight that pranged in the desert-- RS showed it stable, but that was because of a mistake that RS "defaults" to on capsule/tower type rockets-- showing the stability margin in 'calibers' of the TINY escape tower tube, instead of the main body tube calibers-- unless you ALWAYS go in and reselect to "use maximum frontal diameter" for stability caliber calculations.

No shame, it happens to the best of us... another trick is, try switching from the "RockSim Method" of determining stability to the "Barrowman Method" or "Cardboard Cutout" method, and look at the differences.

Richard Feynman said it best in the Challenger Investigation: "physics cannot be fooled" (or words to that effect).

Later and good luck! OL JR :)
*In my best french accent
*ends accent
i see your point these programs run it under IdEAL conditions that nothing in the real world would have, and rocksim is for designing rockets NOT a cart of fireworks :) i guess sometimes you have to put some logical sense in them:eek:
Yes but they are really designed to mimic real world situations. They can only do that if you use the settings to create real world conditions and actually verify that the components in your RockSim design have the characteristics of the real articles (for example by weighing the real ones, and then making sure that the components in the design also have those weights). It is very easy to design rockets that could only exist in some idealized world. You can also design rockets that have totally nonsensical parts and get away with it in RockSim. But these last type either could never be built in reality, or if they were built, could never actually fly. The bottom line: use common sense when you design with RockSim.

Also, don't endow RockSim with abilities that it doesn't actually have. On the various forums, we share RS design files and talk about them as if they were real rockets, and discuss the simulated flights as if they had taken place in real life. We all regard the simulations as good indicators of what would happen if the designs were built and flown IRL, but none of us think that the simulations, by themselves, can definitively prove how any of the designs will actually perform.

BTW, the file for the Quest Totally Tubular that I attached in an earlier post is an example of one of RockSim's "not yet fully implemented" features, or blind spots as I call them. In one of its most recent iterations, RockSim gained the ability to add tube fins to a design, but it did not gain the ability to accurately calculate the contribution of the tube fins to the design's stability. The RockSim design that I attached accurately reflects the Totally Tubular's construction, yet the rocket does cartwheels in the simulations. (The real Totally Tubular is stable.) In order to get RockSim to accurately simulate the performance of the real rocket, some elaborate work-arounds are needed (in the form of "phantom fins"). I deleted those work-arounds from the design that I attached in order to demonstrate my point. There is nothing wrong with that version of the design, but RockSim cannot accurately simulate its flight.

check this out with a 4 oz nose weight the rocket will fly soundly i have rocksim file to prove it

One cannot PROVE anything with a "Simulation" and that is ALL that Rocsim is ...a simulation. There are a ton of other factors these flight simulation programs ignor or average that in real Open air flight act on the vehicle that can cause instability regardless of how much Nose weight is used. Moreover its the lack of a Predictable flightpath that makes flying such models unwise.
While I guess we should never say "can't" because all things are possible... the more purdent questions is Should We? To that questions the Safety First Always flying answer is always "NO". Use some sort of flight control surfaces on your models.

As Doc knows I'm not a big fan of those flame fins but I'd much rather see them on a model then no fins at all! Clear polycarbonate plastic or other options have always been the BEST answer to models of finless flight vehicles.
Ooooohhh clear fins thanks alot for the idea! I can live with clear fins