Launch without rails.

I was just watching a documentary on the German V2 rocket. They launched it without any rails or platform guidance. It had very large fins helping achieve aerodynamic stability earlier. They also could just have been taking a greater risk. Does anyone have any experience with a method to calculate if a launch without a rail could be safe?


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Hal8472 said:

I was just watching a documentary on the German V2 rocket. They launched it without any rails or platform guidance. It had very large fins helping achieve aerodynamic stability earlier. They also could just have been taking a greater risk. Does anyone have any experience with a method to calculate if a launch without a rail could be safe?


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Click to expand...

Not for hobby rocketry... the safety code requires a rod or rail and specifies the length depending on the motor size.

The V-2 DID have ACTIVE GUIDANCE-- it used a gyroscopic guidance system and had both control surfaces on the back of the fins, and carbon "vanes" that stuck out into the exhaust flow coming out of the engine, both controlled by the guidance platform. So, when the V-2 lifted off, and the airspeed over the fins was too slow for the steering tabs on the back of the fins to be effective at correcting the trajectory, the carbon vanes in the exhaust would divert the exhaust from the rocket engine sideways to correct the trajectory. As the rocket picked up speed, the fin tabs would generate more corrective force. As the rocket left the lower atmosphere, the vanes under the engine again generated most of the stabilizing forces until the engine shut down, at which point the rocket simply coasted much like our rockets do.

The difference is, that our model rockets DO NOT have an ACTIVE GUIDANCE SYSTEM like the V-2. Our rockets rely on a PASSIVE guidance system, (although there are a VERY few exceptions, where folks have designed and engineered various active guidance systems and installed them in their rockets), that being the fins, and the proper CG/CP relationship to ensure stability. A model rocket launching off a "platform" without a guidance rail or rod *might* fly straight, but then again, it might not... it will take a certain amount of time to get enough airspeed for the fins to stabilize the rocket... if it has tipped over partway before that airspeed is achieved, it will continue to fly whatever weird angle it happens to be at when that airspeed is achieved.

THAT is why we use rods or rails...

Later! OL JR

None exists w/o aid of a 30fps guidence off the pad, unless you use the "gimble" effect and a quick take off. For what's it's worth, without it, dissaster entertains a funny videos?

there was a 3rd way. it was an hybrid system, working mechanically but actively interfering with the rocket trajectory. it was extremly successfull and many times tested by the frenchs. Of course it seems to be another German idea developed by the famous VERNOM group in the 50s. this has never been tested in amateur rocketry before but i am sure it would work great. another funny thing to try in the coming years



https://libraries.mit.edu/150books/files/2011/03/1956-lift-off-531x1024.jpg


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Very interesting. Two good examples of options to control stability until aerodynamic stability is achieved. A control rod or rail is still the easiest but clearly not the only option. Gyroscope stabilization and jet flow adjustments are within the capabilities of hobbyists. Probably gimbeled mortars as well. Interesting.


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legranddudu said:

there was a 3rd way. it was an hybrid system, working mechanically but actively interfering with the rocket trajectory. it was extremly successfull and many times tested by the frenchs. Of course it seems to be another German idea developed by the famous VERNOM group in the 50s. this has never been tested in amateur rocketry before but i am sure it would work great. another funny thing to try in the coming years



https://libraries.mit.edu/150books/files/2011/03/1956-lift-off-531x1024.jpg


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One of these flew at FAR this year.

Basically 4 cables are attached to the large fins. As the rocket ascends the 4 cables unspool at the same rate, keeping the rocket oriented correctly.


[video=youtube;FZC3cHNtER4]https://www.youtube.com/watch?v=FZC3cHNtER4[/video]

--MCS

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thats cool man! australian project? Hugly rocket but a great direction to work on. I love this rail free systems. guess what, I could use a smaller car to the launches...or get more birds inside... nevertheless it would be a lovely little project for smaller birds to try....


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MCS said:

One of these flew at FAR this year.

Basically 4 cables are attached to the large fins. As the rocket ascends the 4 cables unspool at the same rate, keeping the rocket oriented correctly.


[video=youtube;FZC3cHNtER4]https://www.youtube.com/watch?v=FZC3cHNtER4[/video]

--MCS

.

Click to expand...

Don't try this with any kind of storm around, the trailing wires can guide lightning back to earth and down your launch system wires. You would probably glow in the dark....until the embers burn out...

Would you?

dave carver said:

Don't try this with any kind of storm around, the trailing wires can guide lightning back to earth and down your launch system wires. You would probably glow in the dark....until the embers burn out...

Click to expand...

I suspect the ionized exhaust trail terminating at a large metal tower would act as a lightning rod by itself... no need for spooled wire.

--MCS

.

All the kool kids like playing with induced lightning.

Launching without a rod can be done, just not at a regular event.
Best done in the middle of a playa and the car you need to get home parked far away.
I will not say what we did but we ended up with a system near 100% successful.

M

luke strawwalker said:

The V-2 DID have ACTIVE GUIDANCE...

Click to expand...

I find it AMAZING how far along the Germans were... and specifically Von Braun and a few others. In just two, three or four decades we (humans) went from looking up at birds, to flying with birds to outflying birds to the edge of space. How the hell do you go from 6000+ years on the ground to the moon in just a few decades? How do you go from a biplane to Saturn V so rapidly? The closest thing I can think of in my time is a room-full of computers in the 60's to the Internet to the iPhone in about the same amount of time.

My minimum diameter 54 sim says it'll be at a stable a velocity in just about 12 inches... Maybe 18 inches of 1010 rail? Lol

Good on Werner Von Braun for saying "Screw the Stability Nazis" and ditching the Rail and Rod in favor of Active Guidance.
Too bad he did'nt overbuild at first, because his first Models failed due to being built too light to withstand Supersonic Flight without a reinforced Steel Superstructure beneath the Skin of the Missile. Once he realized that and started building Heavy he was successful.
I watched a Documentary too about the V2, I believe it was called "Nazi Mega-Weapons"?
I've launched C powered Rockets without a Rod when I was a Kid from a Baseball Field. We purposefully set the Rockets on their Fins on top of the Ant Hills so that the initial Blast of Exhaust Gasses would shoot down the Tunnel and then the Smoke would rise throughout the rest of the Tunnel Entrances within a few Feet.
Probably one of the main reasons the Universe has chosen to be particularly cruel to me in my Future Life.
Oh well, I now try to have good Karma, even if I can never atone for my time as a Moronic Child.
Oh, but yeah, the Rockets flew fine every time. They were Alphas and one other that had three Fins and perfect natural Stability.

majordude said:

I find it AMAZING how far along the Germans were... and specifically Von Braun and a few others. In just two, three or four decades we (humans) went from looking up at birds, to flying with birds to outflying birds to the edge of space. How the hell do you go from 6000+ years on the ground to the moon in just a few decades? How do you go from a biplane to Saturn V so rapidly? The closest thing I can think of in my time is a room-full of computers in the 60's to the Internet to the iPhone in about the same amount of time.

Click to expand...

Access to advanced alien technology. I saw it on the History Channel, so it must be history.

TopRamen said:

Good on Werner Von Braun for saying "Screw the Stability Nazis" and ditching the Rail and Rod in favor of Active Guidance.
Too bad he did'nt overbuild at first, because his first Models failed due to being built too light to withstand Supersonic Flight without a reinforced Steel Superstructure beneath the Skin of the Missile. Once he realized that and started building Heavy he was successful.
I watched a Documentary too about the V2, I believe it was called "Nazi Mega-Weapons"?
I've launched C powered Rockets without a Rod when I was a Kid from a Baseball Field. We purposefully set the Rockets on their Fins on top of the Ant Hills so that the initial Blast of Exhaust Gasses would shoot down the Tunnel and then the Smoke would rise throughout the rest of the Tunnel Entrances within a few Feet.
Probably one of the main reasons the Universe has chosen to be particularly cruel to me in my Future Life.
Oh well, I now try to have good Karma, even if I can never atone for my time as a Moronic Child.
Oh, but yeah, the Rockets flew fine every time. They were Alphas and one other that had three Fins and perfect natural Stability.

Click to expand...

You might come back as an ant. I might return as a snail.

The Alpha design is very stable. I'm pretty sure I remember a thread where another member mentioned launching his Maxi Alpha straight off the ground with no rod or launch pad when he was a kid. I wouldn't do it, but it's fun to imagine it.

ThirstyBarbarian said:

Access to advanced alien technology. I saw it on the History Channel, so it must be history.

Click to expand...

+1 for sure

In the apogee peak of flight newsletter today, they talk about stabilizing a rocket "Using Engine-Driven Gas-Dynamic Stabilization", which actually looks simpler than it sounds.. having air vents that pull in outside air to help balance the rocket with no fins and no rail/rod
info here: https://www.apogeerockets.com/Education/Downloads/Newsletter379.pdf

ThirstyBarbarian said:

You might come back as an ant. I might return as a snail.

The Alpha design is very stable. I'm pretty sure I remember a thread where another member mentioned launching his Maxi Alpha straight off the ground with no rod or launch pad when he was a kid. I wouldn't do it, but it's fun to imagine it.

Click to expand...

And get captured by some kid and put into a model rocket...

Cool... Come full circle!!

Later! OL JR

luke strawwalker said:

And get captured by some kid and put into a model rocket...

Cool... Come full circle!!

Later! OL JR

Click to expand...

I'll take the rocket ride! Just, please! No salt or magnifying glass! NOOOOoooooo....!

ThirstyBarbarian said:

I'll take the rocket ride! Just, please! No salt or magnifying glass! NOOOOoooooo....!

Click to expand...

It's amazing how fast ants can get when you use the magnifying glass on them...

Ants seem to move at one "pre-programmed" speed and pretty much stick to it... they either "stop to investigate", tentatively moving about while "reconnoitering" some point of interest in their environment, or "move along" at pretty much a steady speed, and switch back and forth between the two modes...

BUT, when you focus a solar energy beam on them with a magnifying glass, once their temperature starts to elevate, they go into "double time" and will start moving at a high speed that they NEVER seem to go into at any other time naturally. It can be pretty challenging to keep the beam on them-- if the beam "goes away", they rather quickly revert to their "normal" pre-programmed "move along" speed... but if the beam stays on them, they stay in "double time" until they fry...

Fascinating... OL JR

djs said:

In the apogee peak of flight newsletter today, they talk about stabilizing a rocket "Using Engine-Driven Gas-Dynamic Stabilization", which actually looks simpler than it sounds.. having air vents that pull in outside air to help balance the rocket with no fins and no rail/rod
info here: https://www.apogeerockets.com/Education/Downloads/Newsletter379.pdf

Click to expand...

What a great Article.
As I started reading it I was thinking that maybe it would explain why TLP Kits have the MMT shoved so deep inside the BT.
By the time I was done reading it, it had me thinking of ways to incoporate the concepts into Rockets I build that DO have Fins, but need all the Stability help they can get.

I'm curious since these methods require the motor exhaust do they assume that the cg will move far enough forward from the burn to be stable on the coast phase?

TopRamen said:

What a great Article.
As I started reading it I was thinking that maybe it would explain why TLP Kits have the MMT shoved so deep inside the BT.
By the time I was done reading it, it had me thinking of ways to incoporate the concepts into Rockets I build that DO have Fins, but need all the Stability help they can get.

Click to expand...

The motor mounts are shoved up inside the tubes so far because it's a tradeoff-- moving the mass of the motor(s) up the tube moves the CG forward, while at the same time if you put the motors TOO FAR FORWARD you start getting the "Krushnik Effect" reducing the thrust to nothing...

Later! OL JR

luke strawwalker said:

The motor mounts are shoved up inside the tubes so far because it's a tradeoff-- moving the mass of the motor(s) up the tube moves the CG forward, while at the same time if you put the motors TOO FAR FORWARD you start getting the "Krushnik Effect" reducing the thrust to nothing...

Later! OL JR

Click to expand...

But the Article explains the Krushnik Effect, and why it does not apply to what is writen about in the Article.

TopRamen said:

But the Article explains the Krushnik Effect, and why it does not apply to what is writen about in the Article.

Click to expand...

Yes... but if the motors are put TOO far forward, it WOULD create the Krushnik effect...

Later! OL JR

luke strawwalker said:

Yes... but if the motors are put TOO far forward, it WOULD create the Krushnik effect...

Later! OL JR

Click to expand...

Indeed, Point taken.

I was thinking along the lines of what is represented in this illustration from the Article.

Back to the topic: launch with no rails.

As I mentioned in the trail, a German invention broadly used by the frenches in the 50s during the Veronique Program. This program again was vastly populated by German scientists now suddenly french *lol*...
Please check also the painting nr on the rocket and the tail form. This shall make you smile too. Oder as we say: alles klar?

[video=youtube_share;Sux7xikOWic]https://youtu.be/Sux7xikOWic[/video]

The first rocket fired in Kourou in French Guyana, where today Ariane starts, was also a Veronique rocket (this time the advanced AGI version)... with is good old German wire-stabilization system in 1969.

I am sure this would be a great idea to re-test the principles for our amateur rockets of larger diameter, where launch towers appear to be a a critical parameter... I will try to get the original drawings & functionality description from my french sources...