A possible design solution to the new Aerodynamics Issue. Unsure where to put this.

[Moonfrog]

As you can see from this image, I have used structural fuselage to try and move the heavier fuel tank upwards on the rocket towards the nose cone area. According to a thing i googled on rockets, this should make the rocket far more stable. It said add extra weights, but i couldn't think of how to do that, so I did what i'm showing you now. Please ignore the delta V of the rocket, i just wanted to test it out, and see how it flies.

I would like feedback on this kind of design and would appreciate people trying ot build something similar, maybe you can find an easier way to design this. Also designing a rocket with this in mind, does it make it easier for you to fly?

I apolgise for this being in genreal discussion, but this is not meant to be a spacecraft showcase, but a design idea, which i think may lead to helping people with new aerodynamics. Feedback appreciated.

[Gaarst]

This would actually be extremely unstable due to the CoM being way too high in the rocket. There's a reason why real rocket boosters are down the rocket; in doubt always look at stuff that works.

It would be interesting to see how this behaves though

[NecroBones]

It's OK to have the CoM high on a rocket. You want the center of mass to always be in front of the center of drag. So this will probably fly OK in that regard.

Now, without the fins, that might be a different story. You can't rely on thrust alone to keep you stable if all you're doing is placing it ahead of the CoM. There's something called the Pendulum Fallacy, which Goddard himself was guilty of.

Edited May 10, 2015 by NecroBones

[Moonfrog]

It actually flies quite well, don't need the boosters, main thing is to stick fuel tanks at the top. Makes the fins far more powerful than the drag forces effecting the nose cone. Its very stable. guide i got was for building rockets, granted small bottle rockets, but, i'm sure the principles are the same. Idea is just too have a high centre of mass. was able to make designs go past 300m/s without spinning out of control, at low altitudes.

[Wjolcz]

Wasn't Von Braun thinking about something like this but with liquid fuel rockets instead?

[cybersol]

This is how I would build it:

The small central stage has enough command pod torque to go wherever it wants to go. It can even spin itself out an regain control instantly. The delta winglets are great for the boosters because they add a lot of stability and just a little control, which is great for small-medium rocket applications.

[Moonfrog]

interesting, guess the centre of mass on yours would be dead centre. One thing i've certainly learnt is that you don't want centre of mass near the bottom of the rocket. Thx for all that replied.

[problemecium]

I did something sort of similar on one of my lift rockets shortly before unlocking the Mainsail.

[EtherDragon]

interesting, guess the centre of mass on yours would be dead centre. One thing i've certainly learnt is that you don't want centre of mass near the bottom of the rocket. Thx for all that replied.

Really the main thing is you want your center of mass ahead of (i.e. higher than, for rockets) your center of lift (or drag, depending on how you think about it).

[Pink Munn]

I was doing some experimentation with high CoM rockets, and was looking for some advice.

I'm led to believe an early gravity turn is efficient:

Asparagus staging is also efficient. Asparagus staging generally requires radial attachment, and if you want to retain control, these tanks need to be high up on the rocket, like moonfrog posted pictures of. Even more generally than asparagus staging, I have problems with every type of radial decoupling but bi-radial decoupling, as the stage collides with the rocket when it detaches. It's just above the rocket, and falls into it. One of the stages is inevitably on top of the rocket, and gets pulled into the rocket by gravity.

Fancy piloting and staging (spinning and decoupling the radial attachments on top of and below the rocket when they're sidways, then spinning back), or building a rocket as wide as the Atlantic Ocean solves the problem (causes lots of drag), but I was wondering if anyone could come up with an elegant solution.

Cheers

[cybersol]

I was doing some experimentation with high CoM rockets, and was looking for some advice. I'm led to believe an early gravity turn is efficient:

High CoM in more stable. Early gravity turn is generally more efficient, unless its too early or too fast.

if you want to retain control, these tanks need to be high up on the rocket, like moonfrog posted pictures of.

Actually, you are likely better off with those tanks lower, especially if they have fins attached to they are shown in my example above.

as the stage collides with the rocket when it detaches.

Balancing ejection force with discarded stage CoM can get the outer stages to leave in the correct direction, for example in your bi-radial cases. If you want something more complex or need to overcome gravity or aero, you are going to need more force... sepratrons.