#### fisherman

• 217
##### Re: Question about the Vomit Comet
« Reply #20 on: April 29, 2021, 10:22:06 PM »
Quote
In UA/FE theory, UA doesn't act upon the plane and passenger.

Yes it does.

Quote
When the acceleration of the falling object is equal to the acceleration of the Earth, the object has reached terminal velocity relative to the Earth.

https://wiki.tfes.org/Universal_Acceleration#Terminal_Velocity
There are two kinds of people in the world.  Those that can infer logical conclusions from given information

#### WTF_Seriously

• 562
• When I grow up I wanna be like Pete
##### Re: Question about the Vomit Comet
« Reply #21 on: April 30, 2021, 02:16:41 AM »
Quote
In UA/FE theory, UA doesn't act upon the plane and passenger.

Yes it does.

Quote
When the acceleration of the falling object is equal to the acceleration of the Earth, the object has reached terminal velocity relative to the Earth.

https://wiki.tfes.org/Universal_Acceleration#Terminal_Velocity

If UA acted on the passenger, when a parachutist steps out of a plane they would float under UA.  Even FEers know a parachutist 'falls'.  The only way this happens is if the parachutist isn't acted upon by UA.  It's really not that difficult a concept.
« Last Edit: April 30, 2021, 02:19:11 AM by WTF_Seriously »
Distance from Sydney to Perth - We don't know.
There's a mirror floating in the sky - Yup.

#### fisherman

• 217
##### Re: Question about the Vomit Comet
« Reply #22 on: April 30, 2021, 03:05:59 AM »
Quote
If UA acted on the passenger, when a parachutist steps out of a plane they would float under UA.  Even FEers know a parachutist 'falls'.  The only way this happens is if the parachutist isn't acted upon by UA.  It's really not that difficult a concept.

Then maybe DuncanDoenitz can clear it up for us.

Quote
Aerodynamic lift is maintaining the aircraft at a constant altitude, so it (and its occupants) are supported by the atmosphere (atmosplane - yuk!), which is supported by the Earth.  Thus, the aircraft and its occupants, by implication, have identical acceleration and instantaneous velocity as the Earth, so are accelerating upward at 9.81 m/s/s due to UA (also yuk!).

When you leave the aircraft you have the same instantaneous velocity as Earth and atmosphere, hence feel no windrush.  However, as you are now not being accelerated, the earth continues to accelerate towards you at 9.81m/s/s.  In a vacuum, you would remain at constant velocity until the Earth (because it is still accelerating) hits you.

In practice because you are in the, still accelerating, atmosphere you start to accelerate upwards again and begin to feel windrush as aerodynamic drag takes effect, until you reach terminal velocity. (And that's terminal velocity downwards in RE, but terminal velocity upwards in FE!).

At this point your body's acceleration is identical to Earth's but, because of the period when you had reduced acceleration, your velocity is less than Earth's so it still hits you.

https://forum.tfes.org/index.php?topic=17742.msg237132#msg237132

He seems to be interpreting the what the wiki says the same as I am.  The falling object is accelerated up by the atmosphere.  If that causes a contradiction with anything else that FE proposes, is that really a surprise?  The whole theory is full of contradictions.

But actually, it doesn't contradict it. The parachutist does "float", for awhile anyway. He accelerates up at a slower rate than the earth because of drag.  Since the parachutist is accelerating up at a slower rate than the earth is accelerating up, the earth eventually closes the gap.

There are two kinds of people in the world.  Those that can infer logical conclusions from given information

#### DuncanDoenitz

• 179
##### Re: Question about the Vomit Comet
« Reply #23 on: April 30, 2021, 07:15:59 AM »
@ Fisherman; Yes.

Putting aside the "celestial" objects (who's various FE philosophies I completely fail to understand), all "worldly" matter only feels the effects of UA either directly, or indirectly, from the acceleration of Earth.  If you sit on a chair, you are accelerated second-hand by the chair, which is being accelerated by the floor, which is being accelerated by Earth.  A plane in flight, by the atmosphere, because that it is supported by the Earth.

The other thing that baffles me is this;

Everything on Earth is ultimately made from Earth.  You, me, the chair (wood is a biological product of Earth-bound elements, carbon, nitrogen and so on), the house the chair is in (sand, rock), the plane is made of aluminium (smelted from bauxite, mined from the Earth).  Why does all this crap stop feeling the direct effect of UA once we give it a name?

Maybe the only things to feel UA directly are the turtle and the elephants.

#### WTF_Seriously

• 562
• When I grow up I wanna be like Pete
##### Re: Question about the Vomit Comet
« Reply #24 on: April 30, 2021, 01:08:01 PM »
@Fisherman, @DuncanDoenitz

I finally think I see my confusion on your side of the discussion.  Admittedly, I've never took the time to actually try to understand the details of FE terminal velocity.  The majority of what you've both been saying is correct.

Back to the vomit comet.  I'm going to coin two new FE terms for purpose of discussion: Aerodynamic pull and Terminal Acceleration.

Aerodynamic pull is simply the ability of the air passing by you to impact your velocity and acceleration.  Aerodynamic pull is a verifiable 'force' witnessed everyday in skydiving simulators across the world.  Terminal acceleration is simply the acceleration reached due to the effects or aerodynamic pull and has a value of g.

For the vomit comet to work it must place itself and the passenger in a state of zero acceleration.  To do this, it simply has to be able to overcome aerodynamic pull in order to overcome terminal acceleration.  Voila, the FE vomit comet.  Simple as that.

Distance from Sydney to Perth - We don't know.
There's a mirror floating in the sky - Yup.

#### WTF_Seriously

• 562
• When I grow up I wanna be like Pete
##### Re: Question about the Vomit Comet
« Reply #25 on: April 30, 2021, 02:08:52 PM »

The other thing that baffles me is this;

Everything on Earth is ultimately made from Earth.  You, me, the chair (wood is a biological product of Earth-bound elements, carbon, nitrogen and so on), the house the chair is in (sand, rock), the plane is made of aluminium (smelted from bauxite, mined from the Earth).  Why does all this crap stop feeling the direct effect of UA once we give it a name?

Maybe the only things to feel UA directly are the turtle and the elephants.

Just thinking out loud I would say that the reason is that the earth acts as a UA shield.  Someday, as the plethora of evidence becomes overwhelming, FEers are going to have to admit that satellites exist.  When this happens, they'll have to come up with another ridiculous Parsifal like equation to determine how UA comes back into play the further an object is from the surface of the earth.
Distance from Sydney to Perth - We don't know.
There's a mirror floating in the sky - Yup.

#### fisherman

• 217
##### Re: Question about the Vomit Comet
« Reply #26 on: April 30, 2021, 03:24:51 PM »
Quote
Everything on Earth is ultimately made from Earth.  You, me, the chair (wood is a biological product of Earth-bound elements, carbon, nitrogen and so on), the house the chair is in (sand, rock), the plane is made of aluminium (smelted from bauxite, mined from the Earth).  Why does all this crap stop feeling the direct effect of UA once we give it a name?

It doesn't stop feeling the direct effect of UA. They use what amounts to a “reverse normal force” to explain that.  With gravity, we are always being pulled down.  If the surface of the earth wasn’t in the way, it pull us down to the center of the earth.  In response to force of gravity pulling us down to the surface, the surface pushes back up on us and equalizes the force and keeps us from being pulled down.  That’s the normal force.  FE claims it works in reverse with UA. The surface of the earth pushes objects up, and in response the object pushes down.  Equal force means we don’t fly off.

Seems like there is a flaw in that somewhere, but can’t quite put my finger on it.  With gravity, a surface can only respond with so much normal force before it breaks. With the differences in mass between the earth and individual objects on the earth, it seems like at some point an object wouldn’t physically be able to push back. Haven’t really thought it through, though.

Quote
For the vomit comet to work it must place itself and the passenger in a state of zero acceleration.  To do this, it simply has to be able to overcome aerodynamic pull in order to overcome terminal acceleration.  Voila, the FE vomit comet.  Simple as that.

There’s no forces on the plane that would account for overcoming the acceleration. That was the whole point of my question.  Thrust and drag cancel each other out and lift is eliminated by the angle.  The only force on the plane is the acceleration caused by UA.
There are two kinds of people in the world.  Those that can infer logical conclusions from given information

#### WTF_Seriously

• 562
• When I grow up I wanna be like Pete
##### Re: Question about the Vomit Comet
« Reply #27 on: April 30, 2021, 04:08:07 PM »

Quote
For the vomit comet to work it must place itself and the passenger in a state of zero acceleration.  To do this, it simply has to be able to overcome aerodynamic pull in order to overcome terminal acceleration.  Voila, the FE vomit comet.  Simple as that.

There’s no forces on the plane that would account for overcoming the acceleration. That was the whole point of my question.  Thrust and drag cancel each other out and lift is eliminated by the angle.  The only force on the plane is the acceleration caused by UA.

There is no force on the plane due to UA.  That's the point you continue to not see.  The force on the plane is aerodynamic pull.  Duncan's explanation you just quoted applies to the plane no different than a skydiver.  Turn off a planes engine and it ceases producing lift.  It's upward acceleraction begins to slow.  This can only happen because UA is not acting on the plane.  Eventually, aerodynamic pull begins to accelerate the plane upward but at a slower velocity than the earth.  Terminal acceleration will eventually be reached even with a plane but the plane now has a slower velocity so it eventually crashes.  IF the plane was being accelerated by UA you could turn off the engines and it would maintain altitude.

Even in RE you have to fly the plane downward in order to overcome terminal velocity.  Thrust must be provided to cause the plane to exceed terminal velocity.  FE is not different.  Thrust cancels drag means that enough thrust is provided to cancel the pulling force of the atmosphere to achieve zero acceleration of passenger and plane.  That's the only force that needs to be canceled.
Distance from Sydney to Perth - We don't know.
There's a mirror floating in the sky - Yup.

#### fisherman

• 217
##### Re: Question about the Vomit Comet
« Reply #28 on: April 30, 2021, 04:19:07 PM »
Quote
There is no force on the plane due to UA.

Then why does the plane need to overcome "terminal acceleration"?  If it isn't being accelerated, there is nothing to overcome.

Again, I point you back to the wiki definition of TV.  It PLAINLY says that the falling object is accelerated.  Gravity isn't accelerating it so what is?

Quote
IF the plane was being accelerated by UA you could turn off the engines and it would maintain altitude.

It would continue to accelerate, but at a slower rate than the earth because of drag.  Eventually, the earth closes the gap.

EDIT:  Curious as to your resistance to the idea that UA would effect an object that is not on the surface of the earth.  Gravity effects things that aren't on the surface, and if gravity=UA, why wouldn't UA effect things not on the surface?
« Last Edit: April 30, 2021, 04:33:24 PM by fisherman »
There are two kinds of people in the world.  Those that can infer logical conclusions from given information

#### WTF_Seriously

• 562
• When I grow up I wanna be like Pete
##### Re: Question about the Vomit Comet
« Reply #29 on: April 30, 2021, 04:32:16 PM »
Quote
There is no force on the plane due to UA.

Then why does the plane need to overcome "terminal acceleration"?  If it isn't being accelerated, there is nothing to overcome.

Again, I point you back to the wiki definition of TV.  It PLAINLY says that the falling object is accelerated.  Gravity isn't accelerating it so what is?

I just told you.  Objects are accelerated upward by aerodynamic pull.  In the case of the plane, it not only maintains equal upward acceleration due to aerodynamic pull, but lift allows it to also maintain equal velocity with the earth.

Quote

Quote
IF the plane was being accelerated by UA you could turn off the engines and it would maintain altitude.

It would continue to accelerate, but at a slower rate than the earth because of drag.  Eventually, the earth closes the gap.

If the plane was being accelerated by UA there would be no drag.  The plane would be traveling vertically at the same rate as the air around it.  It would never begin to 'fall'.
Distance from Sydney to Perth - We don't know.
There's a mirror floating in the sky - Yup.

#### fisherman

• 217
##### Re: Question about the Vomit Comet
« Reply #30 on: April 30, 2021, 05:30:50 PM »
Quote
I just told you.  Objects are accelerated upward by aerodynamic pull.  In the case of the plane, it not only maintains equal upward acceleration due to aerodynamic pull, but lift allows it to also maintain equal velocity with the earth.

There is no lift in parabolic flight.  It disappears because of the angle.

Quote
If the plane was being accelerated by UA there would be no drag.

Unless it's in a vacuum, acceleration always causes drag.

It just dawned on me what point I am failing to make clear and why we are talking past each other.  The question isn't whether or not it would be possible for the Vomit Comet to be a thing in a UA environment.  The question is "would it be possible according to how the Vomit Comet actually operates?"

The way I understand, the vomit comet could work with UA if the pilot allowed for more drag than thrust and thereby "cancel" the UA effect.

I don't know this for 100% certainty, which is why I asked, but my sense is that if you asked a pilot of the Vomit Comet whether or not they allow for more drag than thrust in parabolic flight, the answer would be no.  They would tell you that drag and thrust are equal.
There are two kinds of people in the world.  Those that can infer logical conclusions from given information

#### WTF_Seriously

• 562
• When I grow up I wanna be like Pete
##### Re: Question about the Vomit Comet
« Reply #31 on: April 30, 2021, 06:12:30 PM »
Unless it's in a vacuum, acceleration always causes drag.

Yes, but UA provides enough force to overcome it.  The plane and air around it are feeling the same drag due to acceleration.  If UA acts on the plane, there is no net drag between air and plane.

Quote

It just dawned on me what point I am failing to make clear and why we are talking past each other.  The question isn't whether or not it would be possible for the Vomit Comet to be a thing in a UA environment.  The question is "would it be possible according to how the Vomit Comet actually operates?"

The way I understand, the vomit comet could work with UA if the pilot allowed for more drag than thrust and thereby "cancel" the UA effect.

I don't know this for 100% certainty, which is why I asked, but my sense is that if you asked a pilot of the Vomit Comet whether or not they allow for more drag than thrust in parabolic flight, the answer would be no.  They would tell you that drag and thrust are equal.

OK.. Definitely something to think about.

Just thinking out loud here.  In RE, the amount of thrust required is that which pushes the plane through terminal velocity and achieves acceleration at the rate of gravity, no?

In FE, the amount of thrust required is that which pushes the plane through terminal acceleration to reach zero acceleration.  Wouldn't those two quantities be equal?

In other words, drag to TV = drag to TA and drag to get to g = drag to get to 0 in the two different systems. This yields overall drag in both cases to be equal.
Distance from Sydney to Perth - We don't know.
There's a mirror floating in the sky - Yup.

#### DuncanDoenitz

• 179
##### Re: Question about the Vomit Comet
« Reply #32 on: April 30, 2021, 11:41:16 PM »
A couple of posts ago I thought we were getting somewhere, but now I'm not so sure.  Part of the problem here, and I say this with the greatest respect, is that the whole FE/RE thing deals with many concepts which, in isolation, can take a career to get your head around, and you can't expect to get the same level of understanding from a few hours or days on the interweb.  I'm happy to concede that Einstein, relativity and bendy space are completely outside my comfort zone, so I don't even go there.  I do, however, have a background in aviation.

First of all, what's the obsession with Terminal Velocity?  Its just a speed (downwards or upwards, depending on your take) at which the force of aerodynamic drag equals the accelerating force of gravity or UA.  (And please stop referring to gravity and suchlike as "drag"; drag is a specific force only caused by aerodynamics).  There is no single "Terminal Velocity", it is dependent on the mass, size, shape and orientation of the object, and upon air density.  So, for instance, in air;

TV of a one Metre sphere of styrofoam is less than a one metre sphere of iron (mass)
TV of a one kilogram sphere of styrofoam is less than a one kilogram sphere of iron (size)
TV of a one kilogram cube of iron is less than a one kilogram sphere of iron (shape)
TV of a 500lb Mk 82 bomb minus its fins, is less than that of one fitted with fins (orientation)
TV of anything dropped from 1000 metres above the sea is less than the same object dropped from 1000 metres above Mount Everest (air density).

So our typical human has a TV of around 300 kmph at typical skydiving heights, due to sea-level air density.  Felix Baumgartner on the other hand achieved over 1300 kmph on his dive from 39 km, due to the reduced air density at altitude.  The WW2 Tallboy bomb achieved a TV of around 1200 kmph, due to its shape and orientation.  So; TV is just a number.

Lets look at the Wiki on TV;

"In the Round Earth model, terminal velocity happens when the acceleration due to gravity is equal to the acceleration due to drag. In the Flat Earth model, however, there are no balanced forces: terminal velocity happens when the upward acceleration of the falling object is equal to the upward acceleration of the Earth".

OK, happy with the RE bit.  FE part; why are the forces not balanced?  What is causing the "upward acceleration of the falling object"?   Wouldn't it make more sense to say that aerodynamic drag of the rising atmosphere is accelerating the falling object?  Therefore the forces are balanced.

Everyone happy with the concept of a windtunnel?  You stick aerodynamic models in it and switch it on, and you can see how they will react in flight.  In other words, static-object, moving-air, gives identical results to moving-object, static-air.  Surely this is analogous to falling object-static air, and static-object, rising-air.

Finally, lift, drag, thrust and weight.  Don't run away with the idea that all these forces are working at 90 degrees to each other; they aren't.

Thrust is always aligned along the axis of the engine so, in conventional aeroplanes, can be considered (more or less) to be along the longitudinal axis of the aircraft, regardless of its orientation.
Weight is always vertically down, regardless of orientation of the aircraft.
Drag is always in line with the relative airflow on the wings.  If the aircraft has an angle of, say, 15 degrees nose-up to the relative airflow, drag will not be aligned with thrust.
Lift is always at 90 degrees to the relative airflow, so is only ever directly opposing weight if the aircraft is in straight and level flight, and almost never when flying a parabolic zero-g flight.

The flight of a Vomit-Comet (and there are several), requires a complex balance of entry speed and orientation (typically at 45 degrees nose-up), thrust and lift-management by the use of flying controls to ensure that the aircraft follows the exact free-fall trajectory of its occupants.

Terminal Velocity has nothing to do with it.

(Oh yes, and acceleration does not cause drag.  Velocity causes drag).
« Last Edit: April 30, 2021, 11:43:45 PM by DuncanDoenitz »

#### fisherman

• 217
##### Re: Question about the Vomit Comet
« Reply #33 on: May 01, 2021, 12:11:14 AM »
A couple of posts ago I thought we were getting somewhere, but now I'm not so sure.  Part of the problem here, and I say this with the greatest respect, is that the whole FE/RE thing deals with many concepts which, in isolation, can take a career to get your head around, and you can't expect to get the same level of understanding from a few hours or days on the interweb.  I'm happy to concede that Einstein, relativity and bendy space are completely outside my comfort zone, so I don't even go there.  I do, however, have a background in aviation.

First of all, what's the obsession with Terminal Velocity?  Its just a speed (downwards or upwards, depending on your take) at which the force of aerodynamic drag equals the accelerating force of gravity or UA.  (And please stop referring to gravity and suchlike as "drag"; drag is a specific force only caused by aerodynamics).  There is no single "Terminal Velocity", it is dependent on the mass, size, shape and orientation of the object, and upon air density.  So, for instance, in air;

TV of a one Metre sphere of styrofoam is less than a one metre sphere of iron (mass)
TV of a one kilogram sphere of styrofoam is less than a one kilogram sphere of iron (size)
TV of a one kilogram cube of iron is less than a one kilogram sphere of iron (shape)
TV of a 500lb Mk 82 bomb minus its fins, is less than that of one fitted with fins (orientation)
TV of anything dropped from 1000 metres above the sea is less than the same object dropped from 1000 metres above Mount Everest (air density).

So our typical human has a TV of around 300 kmph at typical skydiving heights, due to sea-level air density.  Felix Baumgartner on the other hand achieved over 1300 kmph on his dive from 39 km, due to the reduced air density at altitude.  The WW2 Tallboy bomb achieved a TV of around 1200 kmph, due to its shape and orientation.  So; TV is just a number.

Lets look at the Wiki on TV;

"In the Round Earth model, terminal velocity happens when the acceleration due to gravity is equal to the acceleration due to drag. In the Flat Earth model, however, there are no balanced forces: terminal velocity happens when the upward acceleration of the falling object is equal to the upward acceleration of the Earth".

OK, happy with the RE bit.  FE part; why are the forces not balanced?  What is causing the "upward acceleration of the falling object"?   Wouldn't it make more sense to say that aerodynamic drag of the rising atmosphere is accelerating the falling object?  Therefore the forces are balanced.

Everyone happy with the concept of a windtunnel?  You stick aerodynamic models in it and switch it on, and you can see how they will react in flight.  In other words, static-object, moving-air, gives identical results to moving-object, static-air.  Surely this is analogous to falling object-static air, and static-object, rising-air.

Finally, lift, drag, thrust and weight.  Don't run away with the idea that all these forces are working at 90 degrees to each other; they aren't.

Thrust is always aligned along the axis of the engine so, in conventional aeroplanes, can be considered (more or less) to be along the longitudinal axis of the aircraft, regardless of its orientation.
Weight is always vertically down, regardless of orientation of the aircraft.
Drag is always in line with the relative airflow on the wings.  If the aircraft has an angle of, say, 15 degrees nose-up to the relative airflow, drag will not be aligned with thrust.
Lift is always at 90 degrees to the relative airflow, so is only ever directly opposing weight if the aircraft is in straight and level flight, and almost never when flying a parabolic zero-g flight.

The flight of a Vomit-Comet (and there are several), requires a complex balance of entry speed and orientation (typically at 45 degrees nose-up), thrust and lift-management by the use of flying controls to ensure that the aircraft follows the exact free-fall trajectory of its occupants.

Terminal Velocity has nothing to do with it.

(Oh yes, and acceleration does not cause drag.  Velocity causes drag).

Thank you for this...its the kind of input I was looking for.  The only reason I brought up the concept of TV is to demonstrate that UA does in fact effect a "falling object" in FE.  Having to detour around that issue took us down a rabbit hole.

I'm not aeronautical engineer, obviously but intuitively, it seems to me if during the free fall stage only gravity is effecting the plane, then with UA, only UA would be effecting the plane.  And if UA is effecting the plane during "freefall", then the occupants would be pinned to the floor.

Could the vomit comet work with UA?  Maybe, maybe not, but as I tried to clarify the question really isn't whether or not it could work, but could it work the same way.
There are two kinds of people in the world.  Those that can infer logical conclusions from given information

#### DuncanDoenitz

• 179
##### Re: Question about the Vomit Comet
« Reply #34 on: May 01, 2021, 02:01:30 PM »
This is important; the plane is not in free-fall, although its occupants are.  The plane is in aerodynamic flight.

Of the 4 forces, gravity is trying to pull the aircraft in free-fall, but it still has drag, so the pilot has to balance controls (ie lift), thrust and starting trajectory such that drag can be compensated for as if the aircraft was in free fall.  As I see it, the same would occur if the aircraft was in a rising mass of air in FE; the Earth/atmosphere's 1g acceleration would appear identical to RE gravity.

Couple of other things to point out.  The algebraic multiple of time/g-force during the flight has to remain at 1g.  In very simple terms, for 1 minute at zero-g, you might need another minute at 2g, starting and ending the manoever.  Due to structural and aerodynamic limits on the size of aircraft needed for a workable weightless environment (eg an airliner), the zero-g duration is normally less than a minute.

Remember the parachutist-guy leaving the plane and feeling zero-g for an instant?  He then immediately started feeling g due to drag as his airspeed increased.  All the Vomit Comet does is to provide him with that starting altitude, and then a cocoon of still air so that he is only affected by gravity, not drag.

#### stevecanuck

• 322
##### Re: Question about the Vomit Comet
« Reply #35 on: May 01, 2021, 02:26:17 PM »
So our typical human has a TV of around 300 kmph at typical skydiving heights, due to sea-level air density.

Clarification: Skydiver TV is about 195 kmph (120 mph) when falling in the "frog" position belly to earth. Greater speeds occur when diving head first.

#### fisherman

• 217
##### Re: Question about the Vomit Comet
« Reply #36 on: May 01, 2021, 02:53:08 PM »

Quote
Of the 4 forces, gravity is trying to pull the aircraft in free-fall, but it still has drag, so the pilot has to balance controls (ie lift), thrust and starting trajectory such that drag can be compensated for as if the aircraft was in free fall.  As I see it, the same would occur if the aircraft was in a rising mass of air in FE; the Earth/atmosphere's 1g acceleration would appear identical to RE gravity

Would those adjustments be the same in UA? Again, intuitively...thrust on RE would only be whatever the engine provides, but on FE, thrust would be whatever the engine provides plus the "thrust" that UA provides.  So it seems like adjustments to make thrust=drag would be different for FE and RE.
There are two kinds of people in the world.  Those that can infer logical conclusions from given information

#### DuncanDoenitz

• 179
##### Re: Question about the Vomit Comet
« Reply #37 on: May 01, 2021, 05:00:32 PM »
Not sure why you would think that UA would augment thrust.

Thrust always acts along the longitudinal axis of the aircraft so, as the aircraft climbs it would have a vertical component driving the aircraft up.  Conversely, in the dive phase, thrust has a downward component.  A vertical force of some kind from UA could not augment both phases.

On top of that, and I'm 100% not an advocate for FE here (perhaps someone from that camp could chime in), I don't think UA directly acts on any worldly matter apart from the planet (disc?) itself.  I think the only effect of UA on flight is that the atmosphere is supposed to be accelerating upwards at a rate equivalent to (what everyone else calls) gravity.

#### fisherman

• 217
##### Re: Question about the Vomit Comet
« Reply #38 on: May 02, 2021, 03:38:09 AM »
Quote
Not sure why you would think that UA would augment thrust.

LOL, I just realized the mental image I have been carrying in my head is a rocket, going straight up...not a plane.

So I guess what I meant was “lift” not “thrust”.  The accelerating atmosphere creates “lift” in that it accelerates the plane vertically, independent of any lift created by how the pilot manipulates the controls.

I found a good article linked below. One of the points that stood out to me was this.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2598414/

Quote
Contrary to popular misconception, the 0 g freefall phase of flight begins as the aircraft climbs, and does not occur solely as the aircraft descends. Although the aircraft has upward velocity during the initial 0 g phase, its acceleration is downward: the upward velocity is decreasing.

Seems to me that at that point, the upward velocity would be decreasing at a different rate in UA than with gravity alone.

Quote
This is important; the plane is not in free-fall, although its occupants are.  The plane is in aerodynamic flight.

The article I linked above seems to contradict that.

Quote
Essentially, if the aircraft and its occupants "fall" together at 9.81 m/s2, "0 g" is achieved, where there is no reaction force on the occupants by the aircraft.

Also here...

Quote
At this point, the only unbalanced force acting on the plane is weight, so the plane and its passengers are in free fall. This is what creates the zero-g experience.

https://sitn.hms.harvard.edu/flash/2018/free-falling-the-science-of-weightlessness/

EDIT:

Quote
On top of that, and I'm 100% not an advocate for FE here (perhaps someone from that camp could chime in), I don't think UA directly acts on any worldly matter apart from the planet (disc?) itself.

That really seems to be the heart of the matter.  To me, the way TV is explained, UA does effect a "falling object".  Perhaps not directly, but in some what that it causes a falling object to accelerate.  And one must assume that is accelerate up and not down.

But you're right, it would be nice for an FE advocate to chime in.  Seems like it would be an easy enough clarification to make.
« Last Edit: May 02, 2021, 03:46:23 AM by fisherman »
There are two kinds of people in the world.  Those that can infer logical conclusions from given information

#### fisherman

• 217
##### Re: Question about the Vomit Comet
« Reply #39 on: May 02, 2021, 04:35:42 PM »
I was thinking about the issue of whether or not UA force effects objects on the surface and the penny dropped.  (or maybe be the earth rose up to meet it). The whole question about how the Vomit Comet would work on UA is answered by how the weight force works.

Unless UA does effect objects on the surface, there would be no way to perceive weight.  When we step on the bathroom scale, it isn’t measuring the gravitational force.  It is measuring the reaction force, the normal force. Gravity causes us to produce a downward pull on the surface of the scale, and the surface of the scale pushes back up.  That “push up” reaction is what the scale measures.  UA would have to work the same, except in reverse.  The scale would be measuring the reaction force of your feet pushing down on the scale, as UA pushes the scale up.  Without contact with a solid surface, we can’t perceive or measure weight.

But here is the whole key...weight is a force with both magnitude and direction.  On a RE, a 200 lb. Person would generate 1962N of weight force.  On an FE, that same person would generate -1962N of weight force.

The article I linked shows the formula for the amount of acceleration necessary to generate 0g is

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2598414/#:~:text=During%20such%20parabolic%20flight%20an,aircraft%20vertical%20(z)%20axis.

You don't have to look at that formula very long to realize that if you reverse the direction of the weight force, you are going to get a very different result.  The vertical acceleration would have to be in the opposite direction on FE with UA, than what it is on RE with gravity.
« Last Edit: May 02, 2021, 04:39:10 PM by fisherman »
There are two kinds of people in the world.  Those that can infer logical conclusions from given information