What a propeller driven "rocket" might look like.

[Senior Space Cadet]

I didn't know how to add propellers, in Open Rocket. Probably not possible.
There would be a pull propeller at the top and a push propeller at the bottom so, theoretically, the tendency for the rocket to spin would be balanced out.
Why a propeller driven rocket? A lot less restrictions on where and when you can launch. Theoretically, some very high altitudes.

 

[Bill S]

I have never heard of such a thing. Hmm... neat concept. Does this mean no rocket motor?

 

[NateB]

Are you thinking battery powered or something else? Helicopters with coaxial rotors are around in full scale and RC models, so the idea could work.

 

[Antares JS]

It's an interesting idea, but I question whether it's really a "rocket" anymore.

"Any of various simple or complex tubelike devices containing combustibles that on being ignited liberate gases whose action propels the tube through the air: used for pyrotechnic effect, signaling, carrying a lifeline, hurling explosives at an enemy, putting a space vehicle into orbit, etc."

https://www.dictionary.com/browse/rocket?s=t

 

[Zeus-cat]

I think you just reinvented the Dornier DO 335

 

[Mugs914]

This guy used capacitors...



...these guys used rubber bands.

 

[neil_w]

This guy used capacitors...

That's a really good video, thanks for that. It shows some of the issues involved; I liked his deployment strategy. One thing he could have done differently was build *lighter* so he could get more altitude, but then again it looks like maximizing altitude wasn't really his goal.

Using small LiPos would probably be optimal... although much slower to charge. Easy-to-swap batteries would be a good idea.

You could also see that having only one motor didn't cause any excessive amount of roll on the rocket. I would tend to guess the pusher propeller in back isn't necessary, and adds a lot of complication in terms of both internal construction and other issues such as deployment and how to even set it up for launch.

It would be an interesting project that no doubt would require some experimentation.

 

[dr wogz]

or this:

https://www.rocketryforum.com/threads/a-rocket-for-a-smurf.159959/

 

[dhbarr]

https://www.airhogs.com/en-us/detail/p30262

 

[neil_w]

https://www.airhogs.com/en-us/detail/p30262

Ah well, foam construction solved the deployment issue.

 

[MClark]

in the late 60’s there was an article in I believe America Modeler with an 049 engine on a short stick and a parachute.
Chute was twisted around stick in a manner the torque from engine would keep it wrapped. Stick acted as a handle to start engine and keep chute aligned for stability.
Start engine and reeasel straight up. When it ran out of fuel parachute deployed by unwrapping.
The one I saw was mostly stable and had about a minute of fuel.
Remember it’s the 60’s, safety was not Number One.

M

 

[kuririn]

If it uses propellers instead of propulsion then wouldn't it be an aircraft, not a rocket?

 

[dr wogz]

https://www.merriam-webster.com/dictionary/rocket
https://dictionary.cambridge.org/dictionary/english/rocket
https://en.wikipedia.org/wiki/Rocket
https://www.yourdictionary.com/rocket
I would agree, that a propeller driven device would not be considered a rocket.


disclaimer:
While I may have come across as being 'snotty', I was genuinely curious myself...

 

[BBowmaster]

Well, call it a “propeller-driven model of a rocket.” Still semantically a “model rocket.”

What went through my head was a propeller launch, then an air start rocket. Though you could reverse that also.

 

[Senior Space Cadet]

It's an interesting idea, but I question whether it's really a "rocket" anymore.

"Any of various simple or complex tubelike devices containing combustibles that on being ignited liberate gases whose action propels the tube through the air: used for pyrotechnic effect, signaling, carrying a lifeline, hurling explosives at an enemy, putting a space vehicle into orbit, etc."

https://www.dictionary.com/browse/rocket?s=t

No, it probably isn't a rocket, which is why I put rocket in parentheses. But I don' think there is a forum for such a vehicle.

 

[Senior Space Cadet]

As an alternative, it would be simpler and cheaper to make a single pulling propeller and cant the fins to counteract spin.
I'm thinking plane propeller, but I'd have to look into helicopter units. Here is how a single propeller "rocket" might look. You have to imagine the front cone having a propeller.

 

[o1d_dude]

Nazi WWII scientists were way ahead of you.

The Dornier Pfeil (Arrow) was totally propeller driven.

This one however was a rocket driven helicopter(?)

Focke Wolfe experimental Focke-Wulf Triebflügeljäger

 

[neil_w]

FYI that tail cone is what's causing CP to move waaaay forward like that.

 

[kuririn]

This one however was a rocket driven helicopter(?)

Ram jet driven, though they were jump started by rockets.

 

[Mugs914]

Nazi WWII scientists were way ahead of you.

The Dornier Pfeil (Arrow) was totally propeller driven.

This one however was a rocket driven helicopter(?)

Focke Wolfe experimental Focke-Wulf Triebflügeljäger

Every time I see that thing I can't help but think two things:

1. What a spectacular demonstration of angular momentum would result from a hairline crack in a wing root.

2. How much fun the resulting disassembly would be to watch!

 

[kuririn]

Reminds me, I really should work on cutting down my plastic model build pile.

 

[Cape Byron]

Reminds me, I really should work on cutting down my plastic model build pile.

Isn't that your PMC pile?

 

[Senior Space Cadet]

FYI that tail cone is what's causing CP to move waaaay forward like that.

I'm thinking the dynamics are more like a helicopter than a rocket. If you were designing a helicopter, you wouldn't be worrying about it turning upside down. With the propeller pulling up and the weight and drag underneath, it's going to stay vertical. It's going to take quite a bit of force to turn it over. I'm thinking about children's toys I've seen and played with myself. You take a dowel and put a propeller on top and spin it, it will go up. It won't turn upside down or something weird. This is all stuff that would need to be looked at.

 

[Senior Space Cadet]

One question I have is recovery.
If a helicopter loses power, it's rotors will lower it relatively slowly.
If I use a large propeller, will the same sort of thing happen with my rocket?
Might be better if the CG is behind CP.

 

[Senior Space Cadet]

I'm not concerned about whether I'm the first human on the planet to come up with this idea.
I was bothered by the fact that I put a lot of thought, effort, and money into designing and building conventional rockets, but can't launch them.
The problem with conventional rockets is they spit fire and travel fast enough to do real damage. This means the authorities are worried about them.
I pondered the alternatives. There are water rockets. Yawn! There are CO2 rockets, which I mentioned in a previous post. Half yawn! Then I thought of a propeller driven "rocket". Quarter yawn!
Apparently, the battery on a prop driven RC plane, will last about eight minutes. Let's assume that isn't at full power, but it does have to power a bunch of servos and I'd need only one in my rocket. So let's say the battery lasts six minutes. Even at the much slower accent of a prop driven "rocket" vs. a propellant driven rocket, in six minutes, it should be able to get pretty darn high. A camera pointing out the bottom might be possible.
Technically, it isn't a rocket, but it's purpose would be the same or similar. It would just keep going up till it either ran out of juice or I shut it off remotely.

 

[Funkworks]

No, it probably isn't a rocket, which is why I put rocket in parentheses. But I don' think there is a forum for such a vehicle.

Don't shoot the messenger. Just trying to patch up gaps here.

Heli = helix
Copter = wing

It's a helicopter. But without stabilization and manoeuvrability.

For stability, a helicopter needs the tail rotor to counteract the HUGE torque generated by the fast-spinning main rotor. Otherwise, the cabin will spin too. Alternatively, you might want 2 rotors on the nose tip, spinning in opposite directions, i.e. https://en.wikipedia.org/wiki/Contra-rotating

Another issue is the body shape. It's not obvious what a vertical cylinder provides that a generally horizontal one doesn't. Maybe upward speed.

Incidentally, aerobatic aircrafts, and jets, commonly do a move called "vertical up", which is flying straight up, acting essentially the same as your design would. In these cases, the torque from the single propellor or turbine is counter-acted by ailerons: fins (wings) with a profile that can be adjusted to be more or less asymmetric.

Would you want manoeuvrability? Since it's not a rocket, NAR rules may not apply. So adding fins with ailerons might be an interesting variation. Rules or not, this does bring about safety concerns. But there's an interesting design challenge here in: What size and shape are suitable for fins and ailerons, to stabilize a rocket-shaped helicopter?

 

[neil_w]

I'm thinking the dynamics are more like a helicopter than a rocket. If you were designing a helicopter, you wouldn't be worrying about it turning upside down. With the propeller pulling up and the weight and drag underneath, it's going to stay vertical. It's going to take quite a bit of force to turn it over. I'm thinking about children's toys I've seen and played with myself. You take a dowel and put a propeller on top and spin it, it will go up. It won't turn upside down or something weird. This is all stuff that would need to be looked at.

Go look up the pendulum rocket fallacy.

 

[Mugs914]

We're sneaking up on these guys! Awesomely cool, if you ask me, though practicality wise a bit suspect (Imagine trying to back down on to a pitching ship deck while looking over your shoulder at night in bad weather. Pass...).

 

[neil_w]

For stability, a helicopter needs the tail rotor to counteract the HUGE torque generated by the fast-spinning main rotor. Otherwise, the cabin will spin too. Alternatively, you might want 2 rotors on the nose tip, spinning in opposite directions, i.e. https://en.wikipedia.org/wiki/Contra-rotating

Go look at the super-capacitor rocket video linked above. He didn't seem to have much issue with body rotation, probably because the mass of the propeller was extremely small compared to that of the rocket. I suspect that a slight fin cant, as the OP proposed, should take care of it if the movement of the rocket is primarily vertical and achieves any sort of decent velocity. Guessing the proper fin cant, though, is probably impossible, might be good to make it adjustable so it can be trimmed if necessary. I'm thinking small adjustable flaps or extensions on the bottom of the fins, rather than canting the whole fins. Experimentation would be key here.

 

[mbeels]

Something like this is only neutrally stable at best:



If you launch it an angle, it will stay flying at that angle, it acts like a flying gyro. Unfortunately helicopters of any type don't tend to have any positive aerodynamic stability, they are a real handful to fly. Real helicopter pilots are constantly concerned with the helicopter flipping upside down.