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View Full Version : OT: Will the rocket take off?

12-12-2005, 05:59 AM
A rocket is layed on a runway that can move (some sort of band conveyor). The rocket moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the rockets speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

The question is:

Will the rocket take off or not?

Ian B
12-12-2005, 06:00 AM
Not if it's epoxied down...

ian

Yaker
12-12-2005, 06:58 AM
I think it will - the thrust of the rocket is "pushing" against the air that is behind it - not the conveyor.

A system that does what you say - with a wheeled vehicle, the vehicle would not move compared to where you were standing (like a car on a dynomometer or a cyclist that is "riding" on a set of rollers.

The rocket - I believe would indeed move

torker
12-12-2005, 07:39 AM
No....it will not take off!
A seal in the fuel cell will rupture and it will blow up http://bbs.homeshopmachinist.net//biggrin.gif

phil burman
12-12-2005, 07:43 AM
<font face="Verdana, Arial" size="2">the thrust of the rocket is "pushing" against the air that is behind it - not the conveyor.[/B]</font>

Not true. How does a rocket work in space, in a vacuum. To every action there is an equal and opposite reaction is the principle of rocket propulsion.

Regards
Phil

12-12-2005, 08:16 AM
Gee, I wasn't actually expecting answers to this burning question http://bbs.homeshopmachinist.net//biggrin.gif

Ernest Kerr
12-12-2005, 08:17 AM
No, it will not fly.
The weight of the rocket is resting on the conveyor belt. As the rocket thrust pushes against this weight the conveyor, moving in the opposite direction with precisely the same rearward force will cancel any forward movement. Assuming of course there is no fricitonal loss between the rocket and belt.
Ernie

Kdahm
12-12-2005, 08:18 AM
<font face="Verdana, Arial" size="2">Originally posted by Yaker:
I think it will - the thrust of the rocket is "pushing" against the air that is behind it - not the conveyor.

The rocket - I believe would indeed move </font>

The rocket would definitely move. The thrust is not produced by pushing against the air behind it, though. It is produced by accelerating some material from zero velocity (relative to the rocket) toward the rear and accelerating the rocket by way of the third law. A squid jet is a good example of rocket thrust, as is the results of a large meal of beans and cabbage.

The difference between a rocket and a jet is that the jet takes material from in front of itself and accelerates that, while the rocket stores the accelerating material inside itself.

The rocket may or may not take off, though. If it is a rocket plane, then it will. If it's designed for the land speed record, then it won't (unless something goes wrong).

Karl

[This message has been edited by Kdahm (edited 12-12-2005).]

phil burman
12-12-2005, 08:24 AM
This is a nonsense question.

It depends on how the rocket is connected to the conveyor. Is it frictionless, is there a co-efficient of friction or rolling resistance. It depends on what the rocket trust is versus what forces can be transmitted to the rocket via the conveyor.

Regards
Phil

<font face="Verdana, Arial" size="2">Originally posted by Your Old Dog:
A rocket is layed on a runway that can move (some sort of band conveyor). The rocket moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the rockets speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

The question is:

Will the rocket take off or not?

</font>

Wirecutter
12-12-2005, 08:54 AM
If it's anything like the early "experimental" home-made rockets of my youth, it will lift off to about 1 foot, then corkscrew out of control, leaving soot marks on anyone within 100 feet. The flight will continue in this manner until said rocket collides with the most valuable object within range of the craft.

Really, YOD. That was an easy one.

Evan
12-12-2005, 09:53 AM
"Will the rocket take off?"

Why yes, yes it will...

http://vts.bc.ca/pics/missile1.jpg

http://vts.bc.ca/pics/missile2.jpg

torker
12-12-2005, 10:13 AM
Oh My....someone pushed the wrong button didn't they?
Red faces all around please! http://bbs.homeshopmachinist.net//biggrin.gif

John Stevenson
12-12-2005, 10:29 AM
Not if it's this rocket.

Sir John.

BillH
12-12-2005, 10:42 AM
Rockets dont fly.
I heard that sidewinder fell off as the F/A 18 landed, its mount broke.

[This message has been edited by BillH (edited 12-12-2005).]

BillH
12-12-2005, 10:43 AM
<font face="Verdana, Arial" size="2">Originally posted by Wirecutter:
If it's anything like the early "experimental" home-made rockets of my youth, it will lift off to about 1 foot, then corkscrew out of control, leaving soot marks on anyone within 100 feet. The flight will continue in this manner until said rocket collides with the most valuable object within range of the craft.

Really, YOD. That was an easy one.

</font>

Atleast your rocket didnt set the woods on fire and you had to call the fire department :/

IOWOLF
12-12-2005, 10:53 AM
I aint fallin for it again,Keeping MY mouth shut this time. http://bbs.homeshopmachinist.net//wink.gif

------------------
The tame Wolf !

Tinkerer
12-12-2005, 11:05 AM
No... it will CRASH and be the end of us all. http://bbs.homeshopmachinist.net//eek.gif Here my theory.... the nose cone will ketch and dig into the conveyor belt. Then the rocket will be transported at break neck speed to the other end and get wedge between the roller and guide the resulting shock wave will open a rift in the fabric of space and time. Just at that moment a Volcan science ship scanning the parsec picks up the disturbance in force and comes closer to investigate. Upon viewing our historical records deems us a danger to the universe and post a CAUTION beacon warning others to stay away and leave to continue the scans. The beacon draws the attention of a Corillian Saber on the weapons test it targets the 747 on the conveyor because of the high heat signature from it's failing bearing. They fire and destroys it.... however the rift caused by the rocket has developed into a temporal lope and to the Corillian's it appears as if we're lunching and counter strike... and unleash the Omega1. http://bbs.homeshopmachinist.net//wink.gif

BillH
12-12-2005, 12:03 PM
<font face="Verdana, Arial" size="2">Originally posted by Tinkerer:
No... it will CRASH and be the end of us all. http://bbs.homeshopmachinist.net//eek.gif Here my theory.... the nose cone will ketch and dig into the conveyor belt. Then the rocket will be transported at break neck speed to the other end and get wedge between the roller and guide the resulting shock wave will open a rift in the fabric of space and time. Just at that moment a Volcan science ship scanning the parsec picks up the disturbance in force and comes closer to investigate. Upon viewing our historical records deems us a danger to the universe and post a CAUTION beacon warning others to stay away and leave to continue the scans. The beacon draws the attention of a Corillian Saber on the weapons test it targets the 747 on the conveyor because of the high heat signature from it's failing bearing. They fire and destroys it.... however the rift caused by the rocket has developed into a temporal lope and to the Corillian's it appears as if we're lunching and counter strike... and unleash the Omega1. http://bbs.homeshopmachinist.net//wink.gif</font>

You've been listening to Tom Cruise a little too much.

12-12-2005, 12:10 PM
Maybe I did it wrong. Try it this way:

OT: Will the meatball fly?

A meatball is layed on a runway that can move (some sort of band conveyor). The meatball moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the meatballs speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).
The question is:

Will the meatball take off or not?

Sorry for any confusion http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

topct
12-12-2005, 12:18 PM
I don't know. Will you? http://bbs.homeshopmachinist.net//smile.gif

Dawai
12-12-2005, 12:22 PM
Years ago, My older brother gave this Polish lady friend a slip of paper..

One side said "how to keep a dumb polock busy, turn over" She turned it over, other side said "how to keep a dumb polock busy, turn over"

After turning it over and over for about two minutes she got red in the face.

She was not dumb.

torker
12-12-2005, 12:23 PM
<font face="Verdana, Arial" size="2">Originally posted by Your Old Dog:
Maybe I did it wrong. Try it this way:

OT: Will the meatball fly?

A meatball is layed on a runway that can move (some sort of band conveyor). The meatball moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the meatballs speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).
The question is:

Will the meatball take off or not?

Sorry for any confusion http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

</font>
No...the meatball won't have a chance!
Jared will fall off his Subway diet, skip lightly on his feet across the conveyor and will devour the meatball!
It's simple physics you see....
The formula for this is in Machinery's Handbook Edition #19 http://bbs.homeshopmachinist.net//biggrin.gif

12-12-2005, 12:25 PM
So thats why we lost the mount contract. I thought we had been underbid again.

Boomer
12-12-2005, 02:22 PM
stinger???

nheng
12-12-2005, 08:41 PM
The rocket will not take off because there is a plane in front of it parked on the belt, out of fuel ... been there for almost a week http://bbs.homeshopmachinist.net//biggrin.gif

speedy
12-12-2005, 09:41 PM
I could care less, and I am not taking the plane either. I`m getting into my car and driving.
Will it start??

Merry Christmas.
Ken

BillH
12-12-2005, 09:43 PM
Did I say Stinger?? **** I ment sidewinder! my bad. Guess it proves only a few people read my posts, http://bbs.homeshopmachinist.net//smile.gif

[This message has been edited by BillH (edited 12-12-2005).]

hsmike
12-12-2005, 09:44 PM
If I'm going the speed of light in my car and turn the headlights on--what happens?

BillH
12-12-2005, 09:47 PM
<font face="Verdana, Arial" size="2">Originally posted by hsmike:
If I'm going the speed of light in my car and turn the headlights on--what happens?</font>
Well, if you go 30,000 km per second(somewhere in that ball park) All the red lights will look green. If your car can go the speed of light, I would love to know what your power source is and how you did it. to go just a fraction, say .25 of the speed of light for a space ship would require enough energy to power the USA for the next 600 years.

hsmike
12-12-2005, 09:53 PM
BillH
My headlights are clear (other than a few bugs). You still didn't tell me what's going to happen?

BillH
12-12-2005, 10:06 PM
well, You accelerate to the speed of light, so before you get to the speed of light the light from the headlights are already in front of you, so once you hit speed of light, your going to be seeing the light thats ahead of you from before. Now will the outside of the car look like your not moving because your moving at the same speed as that light? I dunno, probably not.
Hmm, now thats only if your going in a straight line, say if you turn a little bit, your headlights will depart away from your car, now that would be cool. HMM, You know, I bet the light will doppler shift enough too, the head lights will look RED if not totally invisible since it will be at a wavelength below visible, hmmm.

[This message has been edited by BillH (edited 12-12-2005).]

[This message has been edited by BillH (edited 12-12-2005).]

darryl
12-12-2005, 10:26 PM
The rocket laying on it's side on the conveyor- ok, how much force would it take to overcome friction and begin to push the rocket along the conveyor belt? If that force is equal to or less than the weight of the rocket, then assuming the motors work properly, the rocket will have enough force behind it to make it skid along the belt. If the force required to make it skid is more than the motors can provide, then the whole thing sits motionless with the motors burning up everything behind it within singeing distance.

Ok, so now let's say the notors are powerful enough to make it skid. Once you have it skidding, it won't ever require more force to keep it skidding, no matter how fast it might get going. It's probably fair for the sake of the arguement to say that it won't weld itself to the conveyor belt.

We're going to make another asumption here that if the rocket actually moves down the belt, that it will skid in a straight line down the center of the belt. Fair enough? Ok.

So the motors are powerful enough to begin skidding the rocket down the belt. It will travel down the belt picking up speed continually until the thrust from the motors drops off below a certain level. It won't take off though, cause it's not pointed the right way.

As long as the belt is moving, the rocket will have to track perfectly straight down the belt, otherwise if it goes off angle even a small anount, it will experience a sideways force on it's bottom side. It will begin to roll and to move sideways at the same time. It will probably begin to lose heading fairly quickly, then it will perform a series of summersalts, triple axles, and sow cows, culminating in a major fireball and scattering of debris (probably because of those darn uncertified welds this time). It's forward speed will slow abruptly because of it's suddenly vastly increased surface area, then so must the belt be braked suddenly. Because the belt has just been blown apart, the braking system will have been damaged and the return length of the belt, presumably underground, will still be moving at great speed and will pile up at the forward roller. This will cause the ground to explode at that point. There will also be a bit of a problem at the rearward roller as the loose belt end whips around and smacks the ground before disappearing into the earth. If Mr Kite were there, he would be guaranteeing a splendid time for all.

phil burman
12-12-2005, 10:32 PM
If you are tavelling in your car faster than the speed of light then your headlights will be shining at you from behind this will provide you with all the light you need to stick your head where the sun doesn't shine, but your headlights do!!!!.

<font face="Verdana, Arial" size="2">Originally posted by BillH:
well, You accelerate to the speed of light, so before you get to the speed of light the light from the headlights are already in front of you, so once you hit speed of light, your going to be seeing the light thats ahead of you from before. Now will the outside of the car look like your not moving because your moving at the same speed as that light? I dunno, probably not.
Hmm, now thats only if your going in a straight line, say if you turn a little bit, your headlights will depart away from your car, now that would be cool. HMM, You know, I bet the light will doppler shift enough too, the head lights will look RED if not totally invisible since it will be at a wavelength below visible, hmmm.

[This message has been edited by BillH (edited 12-12-2005).]

[This message has been edited by BillH (edited 12-12-2005).]</font>

sauer38h
12-12-2005, 10:33 PM
<font face="Verdana, Arial" size="2">Originally posted by BillH:
to go just a fraction, say .25 of the speed of light for a space ship would require enough energy to power the USA for the next 600 years.</font>

I get about 1 year's American energy use to push a car-sized vehicle to a quarter c.

US uses 4.25E11 watts in a year, or 4.25E11 J/sec for a year. Year is 3.15E7 seconds, so a year's energy consumption is 1.34E19 J.

Kinetic energy of a 2000 pound (4400 kg) vehicle, moving at 1/4 C, is (1/2)(4400)(75E6)**2=1.23E19 J, or just about a year's energy use of the US.

darryl
12-12-2005, 10:34 PM
The headlights? They won't come on , or they will go out because the electricity that powers them can't go fast enough to flow in the wires. You will begin to go backwards in time because as you go faster than the speed of light, you will be catching up with light that's getting older and older.

Carl
12-12-2005, 11:19 PM
Damn meatball, ain't moved yet!

http://img.photobucket.com/albums/v35/lathefan/5acfc0e3.jpg

Tinkerer
12-12-2005, 11:28 PM
Carl that look serious you should see a doctor about that. http://bbs.homeshopmachinist.net//eek.gif

torker
12-13-2005, 07:04 AM
Carl....lol!
Geez, I always wondered what you looked like. I was sorta thinking a little less metalic.
So is that the "Real" aluminum pot syndrome?
Russ(just plain ol' skin)

12-13-2005, 07:35 AM
Carl great job! Meatballs are hard to find on the web. Is that a turd with the Morse taper milled off or a real meatball? LOL http://bbs.homeshopmachinist.net//biggrin.gif

Kansas_Farmer
12-13-2005, 07:46 AM
Carl, Nice pickup! Nice shop.

I gotta quit this forum...all I ever do is get another dose of shop envy.

Sorry for the OT, I'd hate to hijack just a productive thread :P

Speaking of shop envy, where's the "My shop pics" thread?

debequem
12-13-2005, 08:37 AM
That was the same story I heard. The pilot just snagged the wire and the AIM 9 decided to go for a swim. The pilot never hit the "Pickle" button and you can't pickle a weapon with weight-on-wheels anyway. So the missile was not hot, but I wouldn't stand it its way, either!

<font face="Verdana, Arial" size="2">Originally posted by BillH:
Rockets dont fly.
I heard that sidewinder fell off as the F/A 18 landed, its mount broke.

[This message has been edited by BillH (edited 12-12-2005).]</font>

Evan
12-13-2005, 08:43 AM
"The pilot never hit the "Pickle" button and you can't pickle a weapon with weight-on-wheels anyway."

Well, not since the USS Forest Fire.

Carl
12-13-2005, 01:10 PM
<font face="Verdana, Arial" size="2">Carl that look serious you should see a doctor about that.</font>

<font face="Verdana, Arial" size="2">Carl....lol!
Geez, I always wondered what you looked like. I was sorta thinking a little less metalic.
So is that the "Real" aluminum pot syndrome?
Russ(just plain ol' skin</font>

<font face="Verdana, Arial" size="2">Carl great job! Meatballs are hard to find on the web. Is that a turd with the Morse taper milled off or a real meatball? LOL</font>

<font face="Verdana, Arial" size="2">Carl, Nice pickup! Nice shop.
I gotta quit this forum...all I ever do is get another dose of shop envy.

Sorry for the OT, I'd hate to hijack just a productive thread :P

Speaking of shop envy, where's the "My shop pics" thread?</font>

Sorry guys, that's not me or my shop. Just a bunch of photos combined for a little humor http://bbs.homeshopmachinist.net//biggrin.gif

All photos and parts of photos were found on the 'net and combined using Microsoft Picture It Publishing.

P.S. yes, that's a real meatball, found on Google Image search as were the rest of the photos.

andy_b
12-13-2005, 07:05 PM
<font face="Verdana, Arial" size="2">Originally posted by hsmike:
If I'm going the speed of light in my car and turn the headlights on--what happens?</font>

if you're going the speed of light will you actually fit in your car? (due to length contraction)

andy b.

Boomer
12-13-2005, 07:36 PM
I didn't see the meatball or the treadmill, thought the guy was having difficulty passing a meatball. Sure looks like it.

spope14
12-13-2005, 09:43 PM
Keep these coming, reason why later - might surprise all of you.

This is a kind of "six degrees of seperation" type of thing. A motor car will not move on an equal speed conveyor because the mode of power is the wheels, and this lays directly on the conveyor - 0 degrees of seperation. The said aircraft in yet another example has one degree of seperation, or it this, the wheels act only as a spacer to keep the aircraft off the runway, it is the item atop the wheels that is actually under power, the treadmill has no effect upon the actual item moving. The rocket again has 0 steps / degrees of seperation, or the item on the conveyor itself is directly powered. It will not move in the situation mentioned. THIS is assuming the treadmill also makes up not only for speed, but the force generated by the rocket. If it were on a gantry moving backwards, it would indeed move forward and in short time pick up its normal speed it would reach with no back movement. Would take 47 extra feet as I recall - terminal velocity.

Now, if there is a seperation the rocket by fins on the rocket between the treadmill and the rocket....the rocket body is isolated out in even just that way, it moves. This gets real tricky, for does the rocket body itself actually create a "seperation" of forces? Even in just the rocket motor shell body?

In the car example, the power drive is exactly direct - I used the term "Tangential forces", in a strange way after a student came up with this in a bit of an awkward way. In the rocket and plane examples, any seperation of the main direct force from the treadmill creates the isolation enough to move forward.

The topic also mentioned in another post may fly a bit.

Actually, these are a bit fun for my students to condsider, especially when almost all of them take Physics. Brings it a bit alive for them. I actually look at the real answers from people to discuss this with my class (not the flaming answers).

One persons meaningless trivia is actually a way to make the world come alive for meaningful and spirited debate for a few real interested kids, and does in fact create a few lab examples for me to try to teach. As you all know, a bit of Physics is actually important to us home shop designing machinists.

keep these things coming.

[This message has been edited by spope14 (edited 12-13-2005).]

12-14-2005, 05:51 AM
I don't think it's a trick question but one that needs to be simplified before attempting to answer it! I don't think this is a question of relativity so much as "how" these items fly in there medium of air as in lift or propulsion.

I plane flys (takes off) by passing enough air over the wings to develop lift. All the frictionless bearings in the wheels and high speed conveyor belts in the world won't affect the air enough to cause lift. What air turbulance created by the high speed conveyor in motion is miniscule compated to whats needed to lift an aircraft and then the air would be on the wrong side of the wing anyway.

The rocket flys by propulsion much like a bullett. It's irrelavant to the rocket what the conveyor is doing once someone lights it up! Get out of the way if you're standing in the same air mass the rockets in. If the earth were a pimple on a knats arse than we wouldn't be standing in the same air mass and we'd be free to scratch it.

Meatballs fly only in the presence of fools not bright enough to eat them. You won't see any Italian food flying in my home!

I think Scopes right. You can learn a lot from all the frivolity here! It's also a good exercise in learning to think outside the frig.

[This message has been edited by Your Old Dog (edited 12-14-2005).]

bob308
12-14-2005, 06:01 AM
if a man is alone in the woods will he still hear a woman bitch at him?????

12-14-2005, 06:08 AM
<font face="Verdana, Arial" size="2">Originally posted by bob308:
if a man is alone in the woods will he still hear a woman bitch at him?????</font>

One could use that question to counter the old line "The silence was deafening". It would now have to read "The silence was nearly deafening" http://bbs.homeshopmachinist.net//biggrin.gif

andy_b
12-14-2005, 08:18 PM
<font face="Verdana, Arial" size="2">Originally posted by Your Old Dog:

The rocket flys by propulsion much like a bullett. It's irrelavant to the rocket what the conveyor is doing once someone lights it up! Get out of the way if you're standing in the same air mass the rockets in.
</font>

a rocket isn't propelled in the same manner as a bullet unless the "bullet" is fired from a Gyrojet.

andy b.