Intercontinental ballistic missile

The arrow obviously accelerates from zero to maximum velocity, but it's is extreme short order.

To have max thrust on a vertical will not produce acceleration after initial standing start to acceleration to reach constant velocity.

You're going to have to find something better than that. It shows nothing against what I've been saying.

It just means that nobody is proving them to be wrong

otherwise I wouldn't still bother to argue my side.

Quote from: sceptimatic on January 03, 2019, 09:24:40 AM

Quote from: MicroBeta on January 03, 2019, 08:50:05 AM

Lack of constant energy applied???  What the hell are you talking about?  What about the part where I say there “is still a constant applied force”. 

And, the cats will impart a force when they “push/springboard” off.  Really?  You know what I meant.

What are you, ten years old?  I was trying to lighten the discussion with my cats but since you want to play those childish games I’ll spell it out for you.

You have two skateboards.  One with a thirty pound weight and the second with no additional weight.  They’re both on the same level and smooth surface.  They both have the same applied constant force.  I’m saying the lighter board will reach a higher constant speed than the heavier one.  Clear enough for you or do I need my niece to get her crayons and draw you some pictures?

Mike

Let me get this right.
Are you saying that you push both boards with the same force an d let them freely roll away until they both stop but in the meantime the heavier board will be much slower than the lighter board or are you applying constant force to both boards so they're always under your apllied energy and not freely rolling along on their own.
Maybe those crayons aren't a bad idea.
Summon your niece.

Okay, that was funny.

It is a constant applied force.  The applied force remains after a constant speed is reached.  Assume each is driven by identical battery operated motors that you turn on with a wireless remote so there is no physical interactions with either board.

Mike

Quote from: sceptimatic on January 03, 2019, 04:40:46 AM

The arrow obviously accelerates from zero to maximum velocity, but it's is extreme short order.

Yes, due to the short time the bow is stretched. But the entire time the bow is bushing the arrow forward, the arrow is being accelerated.

After that, it slows down, but quite slowly.

Again, for the comparison to rockets: The entire time the engine is running the rocket is being accelerated.

Quote from: sceptimatic on January 03, 2019, 05:07:04 AM

You're going to have to find something better than that. It shows nothing against what I've been saying.

No, it quite clearly does.
Even without being able to tell what the acceleration is, we can easily tell that it doesn't' stop dead when the first stage finishes and instead continues moving upwards even before the second stage kicks in.

Yep, the springboard start.

Yep, as I've been saying.

Not vertically it isn't, at max thrust.

If it continued moving upwards the second stage would not be able to kick in.

The first stage stops dead and falls as the second stage immediately kicks in.

Quote from: MicroBeta on January 03, 2019, 09:35:31 AM

Quote from: sceptimatic on January 03, 2019, 09:24:40 AM

Quote from: MicroBeta on January 03, 2019, 08:50:05 AM

Lack of constant energy applied???  What the hell are you talking about?  What about the part where I say there “is still a constant applied force”. 

And, the cats will impart a force when they “push/springboard” off.  Really?  You know what I meant.

What are you, ten years old?  I was trying to lighten the discussion with my cats but since you want to play those childish games I’ll spell it out for you.

You have two skateboards.  One with a thirty pound weight and the second with no additional weight.  They’re both on the same level and smooth surface.  They both have the same applied constant force.  I’m saying the lighter board will reach a higher constant speed than the heavier one.  Clear enough for you or do I need my niece to get her crayons and draw you some pictures?

Mike

Let me get this right.
Are you saying that you push both boards with the same force an d let them freely roll away until they both stop but in the meantime the heavier board will be much slower than the lighter board or are you applying constant force to both boards so they're always under your apllied energy and not freely rolling along on their own.
Maybe those crayons aren't a bad idea.
Summon your niece.

Okay, that was funny.

It is a constant applied force.  The applied force remains after a constant speed is reached.  Assume each is driven by identical battery operated motors that you turn on with a wireless remote so there is no physical interactions with either board.

Mike

One will have a slower speed than the other.
What does this have to do with what I'm saying?

Quote from: Lonegranger on January 02, 2019, 02:44:30 PM

Every thing you say on this subject is wrong. Go watch a video of any rocket launch and maximum velocity is not achieved instantaneously, that would be impossible. Even in the case of a simple projectile maximum velocity is not achieved instantaneously. Watch this.....the arrow is clearly seen accelerating. 

Quote from: sceptimatic on January 03, 2019, 02:11:51 PM

Yep, the springboard start.

And for a rocket, the entire time the engine is on counts as a "springboard start"

Quote from: sceptimatic on January 03, 2019, 02:11:51 PM

Yep, as I've been saying.

No, it is literally the opposite.
You claim it stops dead instantly rather than continuing to go up.

There is literally nothing supporting your nonsensical claim that it magically stops dead.
it is refuted by countless videos and simple experiments.

Scepti is a living pricness bride meme.

Please define thrust!!!!


My car is running at constant 100km/s velocity.
I am using gas power to maintain my thrust against the wind drag and frictional forces that want me to slow down.
Lets say these negative forces add up to decell of 10km/s/s.
I suddenly throw my car into neutral = 0thrust.
Do I stop instantly?
Or do i stop 10seconds later?

Just a full thrust launch and then it's constant velocity under full thrust.

When your car is doing all this vertically then we can discuss it.

Just a full thrust launch and then it's constant velocity under full thrust.

Quote from: sceptimatic on January 03, 2019, 03:12:21 PM

Just a full thrust launch and then it's constant velocity under full thrust.

Again, all available evidence, including that from model rockets, refutes you.
You refusing to accept that and you refusing to do the experiments yourself does not change that.

Quote from: sceptimatic on January 03, 2019, 03:21:59 PM

When your car is doing all this vertically then we can discuss it.

No need to wait for it to be vertical. The only difference is weight causing acceleration.
You have provided no justification as to why it should be magically different or why it should magically mean that things magically stop dead when they are no longer being pushed upwards instead of continuing upwards and slowing down as all experiments ever conducted have shown.

Ok
My car is driving up a vertical ramp.
Direction dowsnt matter.

Also
Please defien thrust for us

Quote from: sceptimatic on January 03, 2019, 03:21:59 PM

When your car is doing all this vertically then we can discuss it.

No need to wait for it to be vertical. The only difference is weight causing acceleration.
You have provided no justification as to why it should be magically different or why it should magically mean that things magically stop dead when they are no longer being pushed upwards instead of continuing upwards and slowing down as all experiments ever conducted have shown.

Direction does matter.

We are dealing with vertical flight not horizontal movement and road/ground friction and also uniform atmosphere which we wouldn't be dealing with on a vertical flight.

If you think driving a car up a wall is the same as driving it on a flat surface then I can't help you.

Quote from: sceptimatic on January 03, 2019, 03:12:21 PM

Just a full thrust launch and then it's constant velocity under full thrust.

So at full thrust, the rocket/missile rises up, let's say, at 1 foot above the ground, it has already reached it's maximum constant velocity and goes no faster? If I have that right, what is this based on?

Quote from: JackBlack on January 03, 2019, 04:42:08 PM

Quote from: sceptimatic on January 03, 2019, 03:12:21 PM

Just a full thrust launch and then it's constant velocity under full thrust.

Again, all available evidence, including that from model rockets, refutes you.
You refusing to accept that and you refusing to do the experiments yourself does not change that.

Quote from: sceptimatic on January 03, 2019, 03:21:59 PM

When your car is doing all this vertically then we can discuss it.

No need to wait for it to be vertical. The only difference is weight causing acceleration.
You have provided no justification as to why it should be magically different or why it should magically mean that things magically stop dead when they are no longer being pushed upwards instead of continuing upwards and slowing down as all experiments ever conducted have shown.

Did you have a chance to see the video I attached earlier?  IMHO, it's a clear example of how a two stage rocket works and a very clear example of what happens when it reaches engine cutoff. 

Quote from: sceptimatic on January 03, 2019, 11:04:01 PM

If you think driving a car up a wall is the same as driving it on a flat surface then I can't help you.

Good thing I never said they were the same.
Yes, I should have clarified, the only significant difference.
If you have a car attached to a vertical wall such that the contact between the tires and the wall can hold and move the car, you have basically the same thing, with the main distinction being weight.
A car in horizontal motion only needs to combat air resistance to keep a constant speed, but a car going vertically (or up an incline) also needs to combat its weight.

There is no reason for it to magically stop dead.

Quote from: Stash on January 03, 2019, 05:35:10 PM

Quote from: sceptimatic on January 03, 2019, 03:12:21 PM

Just a full thrust launch and then it's constant velocity under full thrust.

So at full thrust, the rocket/missile rises up, let's say, at 1 foot above the ground, it has already reached it's maximum constant velocity and goes no faster? If I have that right, what is this based on?

If full thrust gets you 1 foot off the ground then you will have a thrusting rocket, unbalanced at 1 foot before it topples over and turns into a fireball.

A rocket is designed to create max thrust to mass ration to propel that rocket from zero to constant velocity is super short order to give it stability in flight and also to arc to a target.

Quote from: Stash on January 03, 2019, 05:35:10 PM

Quote from: sceptimatic on January 03, 2019, 03:12:21 PM

Just a full thrust launch and then it's constant velocity under full thrust.

So at full thrust, the rocket/missile rises up, let's say, at 1 foot above the ground, it has already reached it's maximum constant velocity and goes no faster? If I have that right, what is this based on?

If full thrust gets you 1 foot off the ground then you will have a thrusting rocket, unbalanced at 1 foot before it topples over and turns into a fireball.

A rocket is designed to create max thrust to mass ration to propel that rocket from zero to constant velocity is super short order to give it stability in flight and also to arc to a target.

Quote from: sceptimatic on January 03, 2019, 11:11:07 PM

Quote from: Stash on January 03, 2019, 05:35:10 PM

Quote from: sceptimatic on January 03, 2019, 03:12:21 PM

Just a full thrust launch and then it's constant velocity under full thrust.

So at full thrust, the rocket/missile rises up, let's say, at 1 foot above the ground, it has already reached it's maximum constant velocity and goes no faster? If I have that right, what is this based on?

If full thrust gets you 1 foot off the ground then you will have a thrusting rocket, unbalanced at 1 foot before it topples over and turns into a fireball.

That is why large rockets usually have gimbaled engines an automatic stability control that uses their inbuilt gyroscopes for a direction reference.

Quote from: sceptimatic

A rocket is designed to create max thrust to mass ration to propel that rocket from zero to constant velocity is super short order to give it stability in flight and also to arc to a target.

Small rockets can accelerate very fast and are usually launched on a rail to provide stability until they have enough velocity for aerodynamic and/or spin stabilisation.

But a large rocket cannot accelerate "from zero to constant velocity is super short" time - it simply does not have enough thrust.

Solid fuel rockets like most ICBMs have a high initial thrust and accelerate rapidly but certainly not in a "super short time".

The LGM-30G Minuteman ICBM has a launch mass of 79,432 pounds and first stage thrust of 203,158 pounds force, so it accelerates at 2.56 x g.
But with a maximum velocity of approximately 15,000 mph (after 3 stages) it still takes a lot of seconds to reach that velocity.

The missile's stability is provided by a quick-reacting, inertially guided control system.

Quote from: JackBlack

There is no reason for it to magically stop dead.

It doesn't magically stop dead. If it cannot accelerate then it has to stop dead, because there is no added momentum for a car going up a vertical at a constant velocity.

You didn't answer the question, I'll phrase it another way. At full thrust at takeoff, when does the rocket stop accelerating?

But if a rocket or even a ball throw vertically stops accelerating it has gravity (or whatever you call the force pulling things down) slowing it down - a negative acceleration.

A ball vertically does not stop climbing immediately.
You could probably launch a base-ball vertically at 15 m/s. This ball would take over 1.5 seconds to stop and start falling.

If a rocket were travelling vertically at 1528 m/s (the maximum for one Go-Fast rocket flight ) it would take about 160 seconds to stop and start falling.