shutting down a solid rocket.

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mrwalsh85 said:
A lathe.

In all seriousness, I'd be leery of providing any insight to the inquiry because anything that is offered and utilized in the final solution, that results in damage, or worse, loss of life, could theoretically be used against you in a court of law...
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......... different with me jack........ i tell all.
 
enjoy.............. not many people have ever seen the GOODYEAR WING FOOT EXPRESS !

585 mph...... jato solid rocket engines....... a whole bank of them......
 

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Steve Shannon said:
We don’t cool nozzles for solid propellant. We use nozzles that withstand the heat for the short time they’re needed.
Test it unmanned first. At the moment you open the nozzle you have much more area at a high pressure and a greater mass of gases will be released. I think you’ll experience a spike in thrust followed quickly by a precipitous drop off in thrust.
Ejecting the nozzle would result in an even greater spike in thrust and quicker drop.

Blowing out a side panel will result in sideways thrust.
Action = reaction is unforgiving.
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with metals like tantalum.....that will withstand 7000 degrees...... who need to cool anything ?
 
sorry thats for popular science........besides that wing foot express is my car...... from 1961.

jack.
 
So you plan on using your fancy unobtanium to built a 2 peice nozzle that will slam shut in a emergency and stop the thrust . How do you plan to contain the massive explosion that follows once you seal the nozzle of a solid rocket motor that already has been ignited ? Now your saying the "wing foot express" is your car ? You where how old in the early 60's when you built this car ?
 
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3stoogesrocketry said:
So you plan on using your fancy unobtanium to built a 2 peice nozzle that will slam shut in a emergency and stop the thrust . How do you plan to contain the massive explosion that follows once you seal the nozzle of a solid rocket motor that already has been ignited ? Now your saying the "wing foot express" is your car ? You where how old in the early 60's when you built this car ?
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I take it that he wants to slam it shut to produce thrust and open it up to reduce thrust. With it shut the nozzle still has an exit throat. Either way guy needs to take his meds.
 
For "Thrust Termination" on solids you typically have a shaped charge on the forward bulkhead of the motor. Which fires, ejects the bulkhead and vents the pressure inside the motor. The alternative is they put a linear shaped charged on the weld seam of the case, which splits the case open. Which flavor they use depends on the design on the motor case. This does indeed stop the motor from thrusting, and prevents the rocket from flying anywhere else. Which is the intended goal, keeping it in your safety area.

It does not however, stop it from burning (notice I called it "thrust termination"). They tend to burn quite violently after a termination, but they at least aren't going to fly very far off course. If you did this on a car, you would likely burn the car to the ground. Especially if you had a wreck. Even if you had a way overbuilt fire suppression on the car, it wouldn't even make a dent into putting out a propellant fire like that.

You also probably don't want to be driving a car that has a fairly sizable shaped charge on a rocket motor. Every once in a while in the wrong conditions it has been known to cause the motor to detonate instead of split open.

If you need to extinguish a rocket motor for safety reasons you don't use a solid. Most propellants will happily burn underwater. If you are really lucky on a small motor, you can get them to extinguish occasionally from a rapid pressure drop. Large motors are a lot less likely to do this.
 
LARRY A ROSA said:
the nozzle is machined to end up in 2 parts, like a clam shell, the nozzle is hydraulically actuated , it opens and closes powerfully...... it has metal strip lines that ...... when it hydraulically closes it seals the nozzle so only the circle is used to pass fuel through.

that hydraulic system is only used in the event of an EMERGENCY......... when it is nessasary to stop propulsion.

the hydraulic system is super powerful............ it smashes those 2 movable pieces together .
Click to expand...

If I understand this correctly, you intend to have the nozzle CLOSE while the motor is burning as a way to stop it? If that's the case, you're going to have a devastating explosion and almost certainly destroy your car and kill anyone who is in it! The whole reason burning rocket propellant creates thrust is because it burns just slow enough and is allowed to vent the pressure to not completely overpressurize and explode. If you close up a rocket nozzle like closing a faucet valve, the propellant will continue to burn, the pressure will ACCELERATE that burning, and within a fraction of a second go off like a bomb!

No. If you want to stop a rocket by making it suddenly lose thrust, you'll have to REDUCE the pressure by opening the nozzle so the expanding gasses can flow out freely without having to build pressure and speed through the nozzle. Doing so will not extinguish the burning propellant, in fact it will allow the propellant to burn for much longer than if it were under pressure, but your rocket will have no thrust.

Again, I think you're pressing on with an idea that doesn't bode well with the laws of physics and is extremely dangerous. The best way to stop a rocket is to starve it of propellant, and that is easily facilitated in liquid and hybrid rocket engines by simply closing off a valve between the fuel or oxidizer source and the combustion chamber.

Another way to think about it is like this: when you mix baking soda and vinegar, you get a sloppy expansion of foam and carbon dioxide gas, right? So, how do you stop that reaction once you've mixed the components and started the reaction? The answer is, you can't. Nothing can be done to stop it. All you can do is either only allow a little bit of the mixture to react and stop the supply (valving off the fuel) or allowing the reaction to expand naturally and finish reacting. Now suppose your baking soda and vinegar is reacting inside a plastic bottle. The neck of the bottle is a nozzle and will cause the foam to increase in pressure and speed as it exits the bottle just like a rocket nozzle. What happens if you suddenly decide to stop the foam from coming out by screwing the cap on (closing the nozzle)? The reaction WILL NOT STOP! It will continue inside the sealed bottle until all the baking soda and vinegar have reacted. The question now is will that reaction stop before the plastic bottle bursts open? If you didn't use very much of the mix, then maybe so. But most likely the bottle will overpressurize to the point that it can't hold together any more. Since you're talking about a rocket that can accelerate a car to over 500mph, the pressure inside that combustion chamber will be greater than any material on earth can withstand if you seal it off.
 
LARRY A ROSA said:
with metals like tantalum.....that will withstand 7000 degrees...... who need to cool anything ?
Click to expand...
Tantalum is not new, by any means. And its melting point is 5463F or 3000C. Surely it will lose its strength far below its melting point. At 7000F tantalum is liquid. At 7000C it's vapor.
 
the company i contacted at their site states that the tantulim that they have is new......& "IS" good for 7000 degrees.

i also thought that 5400 degrees was the max........... they state this is a new tantalum ?
 

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3stoogesrocketry said:
Can you show us your design for your car ? I am intetested how you designed and built a 48 foot rocket car . What kind of materials do you use ? Does the cage or chassie need to be certified ? What is your end speed goal . You mentiond our hobby rocket motors . What size motor are you thinking of using ?
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1600 mph.
 
LARRY A ROSA said:
the company i contacted at their site states that the tantulim that they have is new......& "IS" good for 7000 degrees.

i also thought that 5400 degrees was the max........... they state this is a new tantalum ?
Click to expand...
Tantalum is an element. They can't make "new tantalum" with a different melting point any more than they can make "new gold" that's purple.

Now if it's a compound containing tantalum, that's a different thing.
 
mach 4.0
used a liquid rocket, 100 mile range.
 

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here is that rocket engine...... it will push this drone to mach 4.0 !!

like is said i seen one one time in person..... the combustion chamber is little bigger that your fist !

unbelievable power....... i am now looking for the complete file on this rocket engine.
 

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I see multiple obvious problems here.

-This clamshell nozzle that you're so jazzed about is overly complex. Just jettison the nozzle if you have an emergency. That will release all the chamber pressure and result in the loss of thrust. Such a system will be a lot simpler and, more importantly, more reliable. Hydraulics fail much more often than ordnance does. You also won't have the problem of holding that nozzle closed against hundreds of PSI of chamber pressure, and a clamshell nozzle, if built, would have to be 100% totally sealed when closed, with nothing leaking through the seam between the halves while the motor operates. Leakage would, at best, result in significant efficiency losses or, at worst, wreck the nozzle and anything near it. Preventing this leakage against the chamber pressure of a rocket motor/engine presents a significant problem.

-The melting point of a substance is not the point at which it will fail due to heating. Materials can lose their strength when heated excessively even if they are not close to melting.

-The RL64 engine is fueled by hazardous hypergolic chemicals that you don't want anywhere near a driver or spectators, namely hydrazine and red fuming nitric acid. The Jayhawk also achieves its range and speed flying at a high altitude and being a small, light drone vehicle that weighs only a few hundred pounds. You can't just strap the same engine to a different vehicle and expect similar performance.

-You have a lot of other problems besides propulsion - aerodynamic drag being a major one, and also how you're going to prevent the whole thing from flipping over as you create shock waves between the car and the ground. 1600 mph is above Mach 2. There's a reason why supersonic aircraft typically also fly very high - the air is thinner and produces a lot less drag. Supersonic driving has been done once. This was back in October 1997, using a pair of Rolls-Royce jet engines that produce much more thrust than any motor we're going to be talking about here, and that barely broke Mach 1. You're talking about doing something that is going to require professional engineers and a huge amount of funding. It is well beyond the scope of a hobby forum.
 
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