1g Ships and Size:7 worlds...

[AnotherDilbert]

And it is an error - we are plotting displacement not velocity.

Sigh. Did you read LBB2? Did you think, before you reflexively said LBB2 is wrong?

What is constant displacement per turn, displacement per time?

 

[AnotherDilbert]

Your 1g band between the planet surface and the first gravity circle is the error.

Which is irrelevant as the ship never leaves the surface, it's vector is never upward.

Read the section of LBB2 I quoted again.

 

[mike wightman]

There is a huge difference between plotting displacement per turn and plotting velocity per turn

 

[AnotherDilbert]

If its any consolation I don't think this can be correct - a 1g ship can not lift off like a rocket from a 1.25g world,

I'm glad we agree about something.

but the rules say otherwise.

Not even LBB2 is that simplified, read LBB2 again:

LBB2'77, p26:
In a player’s movement phase, he will indicate the acceleration (new vector) he wishes to apply, and note any gravitational influence vector he is required to apply, and then add them to his ship’s present vector. His ship then moves in the direction of its new vector, for the length of the vector. The vector then remains on the playing surface for reference during the next applicable movement phase.

First plot all the vector changes, then apply them to the vector at the same time.

LBB2 actually get the result we agree it should get.

 

[AnotherDilbert]

There is a huge difference between plotting displacement per turn and plotting velocity per turn

No, there isn't.

Just think it through, with the vector in mm/turn, a velocity.

It's just Newtonian mechanics, turn-based.

 

[mike wightman]

Displacement per turn is velocity, velocity per turn is acceleration. We are plotting displacement.

Now the bit you appear to keep missing

When the vector of a ship passes through the gravity bands of a world, the
gravity may alter that vector*. During the movement phase, lay out the vector of the
ship to determine where it will move**. If the exact midpoint of the vector lies
in a gravity band, a gravity vector will be added to the course vector to create a new
vector.***

*A ship sitting on the ground has no vector it is not moving. The rule is that the ship must pass through the gravity band - so unless the ship decides to tunnel into the ground it never passes through the 1.25 band

During the movement phase we lay out the vector of where it will move - in this case 100mm upwards

50mm is in the 0.25g band so that is the value we modify the vector by and the 25mm reduction due to drag

So the final vector that we actually draw is 50mm.

Now technically you would have to fly in a gravity band for 1000s for its full effect but that way lies madness and the need to start doing calculus. And we are already breaking the laws of physics by plotting a 100mm vector, but the rules say we can.

I think this is broken, but then the whole vector movement system is a simplification of Newtonian movement.

 

[AnotherDilbert]

Now the bit you appear to keep missing

When the vector of a ship passes through the gravity bands of a world, the
gravity may alter that vector*. During the movement phase, lay out the vector of the
ship to determine where it will move**. If the exact midpoint of the vector lies
in a gravity band, a gravity vector will be added to the course vector to create a new
vector.***

*A ship sitting on the ground has no vector it is not moving. The rule is that the ship must pass through the gravity band - so unless the ship decides to tunnel into the ground it never passes through the 1.25 band

I have read and grasped that. Have you read and grasped this:

LBB2'77, p26:
In a player’s movement phase, he will indicate the acceleration (new vector) he wishes to apply, and note any gravitational influence vector he is required to apply, and then add them to his ship’s present vector. His ship then moves in the direction of its new vector, for the length of the vector.

You apply both drive acceleration and gravity before changing the ship's vector.

The gravity is not applied to the drive acceleration, but the ships vector at the start of the turn, in this case the null vector.

The ship never moves, as we agree it shouldn't.

 

[Captain_Ahab]

Not quite.

How do planes fly upside down? (intended as rhetorical for the pedantic)

If you intended this to be a serious question, then you understand flight less than you think

 

[Condottiere]

All things being equal, or neutralized, how much minimum external sustained boost does our factor/one manoeuvre drive need to reach orbit?

I was thinking of a ski ramp.

 

[mike wightman]

I have read and grasped that. Have you read and grasped this:

You apply both drive acceleration and gravity before changing the ship's vector.

The gravity is not applied to the drive acceleration, but the ships vector at the start of the turn, in this case the null vector.

The ship never moves, as we agree it shouldn't.

Yes, you add the drive acceleration which is 10mm vertically and subtract the gravity of the band at the midpoint of that 100mm, which is the 0.25 band, and then you subtract drag.
As you have oft quoted
You apply both drive acceleration and gravity before changing the ship's vector.
So the vector starts at zero, you apply 100-25-25=50mm those are the rules, that is what it says.
You then say
The gravity is not applied to the drive acceleration, but the ships vector at the start of the turn, which is a direct contradiction of your first quote.

Your starting vector is 0
You apply drive acceleration and gravity (for the band the ships midpoint is in)
If the exact midpoint of the vector lies in a gravity band, a gravity vector will be added to the course vector to create a new vector
adjust for atmosphere
draw the vector.

Now I agree that this is broken and wrong but it is what the rules as written say.

 

[mike wightman]

If you intended this to be a serious question, then you understand flight less than you think

Hence the edit for the pedantic...

 

[AnotherDilbert]

As you have oft quoted
You apply both drive acceleration and gravity before changing the ship's vector.

Not just before changing the ship's position, before changing the ship's vector. When you calculate gravity the ship's vector hasn't been changed, so remains null = [0,0].

I don't think you see what I mean, would it help it I change the word "apply" to the exact word used in the rule "indicate"? (I meant apply as in draw on the playing surface, not change the ship's vector.)

LBB2'77, p26, ¶1:
In a player’s movement phase, [1] he will indicate the [1a] acceleration (new vector) he wishes to apply, and note any [1b] gravitational influence vector he is required to apply, and then [2] add them to his ship’s present vector. His ship then [3] moves in the direction of its new vector, for the length of the vector.

1: Indicate all accelerations (without changing the ships vector).
_ _ 1a: Indicate desired drive acceleration, e.g. 100 mm up (the ship's vector is unchanged [0,0]).
_ _ 1b: Indicate gravitational influence (ship's vector is still [0,0]), so 125 mm down.
_ _ 1c: Indicate any other accelerations, e.g. Atmospheric Braking (ship's vector is still [0,0]).
2: Change the ship's vector, with all the indicated accelerations.
_ _ 2a: Update ship's vector with all changes = [0,0] + [+100,0] + [-125,0] = [-25,0], i.e. 25 mm down.
3: Change the ship's position.
_ _ 3a: Update the ship's position with the new vector [0,0] + [-25,0].

Your starting vector is 0

Agreed.

You apply drive acceleration and gravity (for the band the ships midpoint is in)

We indicate the accelerations, ship's vector is unchanged (step 1a and 1b above).

If the exact midpoint of the vector lies in a gravity band, a gravity vector will be added to the course vector to create a new vector

Ship's vector is unchanged [0,0], so gravity is surface gravity (step 1b).

adjust for atmosphere

Agreed, ship's vector is still unchanged at [0,0] (step 1c).

draw the vector.

Now we change the vector with all the indicated accelerations (step 2).

And then we can move the ship (step 3).



The system isn't broken, and we get the result we both agree we should get. The people who wrote the system presumably thought it through.

 

[Captain_Ahab]

Hence the edit for the pedantic...

Then you understand why this...

mike wightman said:
Aircraft fly because their overall lift cancels their weight. 1-1=0, now add 1g of thrust 0+1=1 understand yet?

is wrong

 

[mike wightman]

Yes because some of the thrust is lost to drag and generating lift but I wanted to keep the maths simple, fractions and decimals often frighten some.

 

[mike wightman]

Not just before changing the ship's position, before changing the ship's vector. When you calculate gravity the ship's vector hasn't been changed, so remains null = [0,0].

I don't think you see what I mean, would it help it I change the word "apply" to the exact word used in the rule "indicate"? (I meant apply as in draw on the playing surface, not change the ship's vector.)



1: Indicate all accelerations (without changing the ships vector).
_ _ 1a: Indicate desired drive acceleration, e.g. 100 mm up (the ship's vector is unchanged [0,0]).

The initial vector is unchanged, the future vector, the one we draw when we have applied m-drive accelerartion, gravity and air resistaqnce. It is no longer 0
You directly quoted it yourself
"In a player’s movement phase, he will indicate the acceleration (new vector) he wishes to apply,"
This new vector is the one generated by the m-drive and is 100mm vertically.

_ _ 1b: Indicate gravitational influence (ship's vector is still [0,0]), so 125 mm down.

No, this is where you are wrong. You do not apply the surface gravity force because the rules state you have to pass through the gravity band, the only way to pass through the 1.25 band is to fly through the planet. You use the gravity band of the midpoint of the new acceleration imaginary vector.
"When the vector of a ship passes through the gravity bands of a world, the gravity may alter that vector. During the movement phase, lay out the vector of the ship to determine where it will move."
"In a player’s movement phase, he will indicate the acceleration (new vector) he wishes to apply, and note any gravitational influence vector he is required to apply, and then add them to his ship’s present vector.
New vector plus gravitation etc, not present vector, not starting vector, new vector - the one being applied this turn.

Physically possible? No.
Rules as written? Yes.

 

[AnotherDilbert]

The initial vector is unchanged, the future vector, the one we draw when we have applied m-drive accelerartion, gravity and air resistaqnce. It is no longer 0
You directly quoted it yourself
"In a player’s movement phase, he will indicate the acceleration (new vector) he wishes to apply,"
This new vector is the one generated by the m-drive and is 100mm vertically.

The new vector is an acceleration vector, it's not the ship's velocity vector. Gravity does not act on the drive acceleration, but the ship.

So, this:

In a player’s movement phase, he will indicate the acceleration (new vector) he wishes to apply, and note any gravitational influence vector he is required to apply, and then add them to his ship’s present vector. His ship then moves in the direction of its new vector, for the length of the vector. The vector then remains on the playing surface for reference during the next applicable movement phase.

means nothing?

Or is just a case of "the rules are wrong because they don't agree with me" again:

Each ship has a vector, which expresses that ship's velocity as a line (arrow) of a specific direction.

And it is an error - we are plotting displacement not velocity.

Then Striker is wrong.

You do realise that this means you are wrong?

LBB2'77, p37:
_ _ Optional Acceleration Effects: The vector movement system used in this game assumes, for simplicity, that all acceleration is instantaneous, and occurs at the beginning of the movement phase of the turn.

Drive acceleration and gravity acceleration happens at the same time, before any movement has taken place. Before the ship has left the surface.

No, this is where you are wrong. You do not apply the surface gravity force because the rules state you have to pass through the gravity band, the only way to pass through the 1.25 band is to fly through the planet. You use the gravity band of the midpoint of the new acceleration imaginary vector.

You only quoted part of the rule and left out an important part:

LBB2'77, p29:
When the vector of a ship passes through the gravity bands of a world, the gravity may alter that vector. During the movement phase, lay out the vector of the ship to determine where it will move. If the exact midpoint of the vector lies in a gravity band, a gravity vector will be added to the course vector to create a new vector.

Position [0,0] and vector [0,0].
The exact midpoint of the vector is P + V/2 = [0,0] + [0,0]/2 = [0,0].
Is the midpoint [0,0] in a gravity band? Yes, it is. On the surface of the planet.



This isn't complicated, we both agree it's just a model of Newtonian mechanics.
We both agree what the result should be.
The rules are, as far as I can see, pretty clear and what they have to be to be a model of Newtonian physics.
But you are insisting on a farfetched interpretation that are producing results you agree are broken?
Are you deliberately trying to misconstrue the rules?

 

[mike wightman]

The new vector is an acceleration vector, it's not the ship's velocity vector. Gravity does not act on the drive acceleration, but the ship.

So now we are tracking two different vectors? the vector shows future displacement, not velocity, not acceleration not force.

Or is just a case of "the rules are wrong because they don't agree with me" again:

There is not need for the snark, up to now it has been a civil discussion with respect to out conflicting rules interpretations.

The rules say
"he will indicate the acceleration (new vector) he wishes to apply, "
the 100mm upwards
"and note any gravitational influence vector he is required to apply",
which by the rules as written are those at the midpoint of the new acceleration vector
"and then add them to his ship’s present vector."
which is 0
"His ship then moves in the direction of its new vector"
which is 100-25-25=50mm upwards.
Those are the rules you keep quoting. applied as you quote them

Drive acceleration and gravity acceleration happens at the same time, before any movement has taken place. Before the ship has left the surface.

The "construction" vectors are penciled in and then the resultant vector is drawn and takes place at the start of the turn for the sake of simplicity rather than the much more complicated displacement due to acceleration (the optional rule)

The exact midpoint of the vector is P + V/2 = [0,0] + [0,0]/2 = [0,0].
Is the midpoint [0,0] in a gravity band? Yes, it is. On the surface of the planet.

The ship has a construction vector 100mm upwards which puts it in the 0.25g band, the construction vector is not on the surface.

This isn't complicated, we both agree it's just a model of Newtonian mechanics.
We both agree what the result should be.

Yes, the ship should not be able to take off in the first place.

The rules are, as far as I can see, pretty clear and what they have to be to be a model of Newtonian physics.
But you are insisting on a farfetched interpretation that are producing results you agree are broken?

I consider my interpretation to be correct and yours to be the farfetched interpretation based on a misapplication or misunderstanding of the sequence as the rules are written. But this is Traveller and this discussion goes back over forty years.

Are you deliberately trying to misconstrue the rules?

I could level the same accusation, my interpretation is in good faith and I assume yours is, we just disagree. No malitious intent, not trying score interweb points, just a frank discussion.

I enjoy these back and forth discussions with you because you are always thorough.

 

[AnotherDilbert]

I could level the same accusation, my interpretation is in good faith and I assume yours is, we just disagree. No malitious intent, not trying score interweb points, just a frank discussion.

OK, sorry if I sounded harsh, I was having a "wonder if we are even reading the same book" moment.

There is not need for the snark, up to now it has been a civil discussion with respect to out conflicting rules interpretations.

Sorry, I was not trying to be snarky. I was trying to find out if there were any house rules lurking in the shadows? When you say the rules are wrong, something's going on? It's an extraordinary statement when discussing RAW.



There is some very fundamental misunderstanding between us, so I will try be extremely thorough:

So now we are tracking two different vectors? the vector shows future displacement, not velocity, not acceleration not force.

Yes, of course we are tracking several vectors, the velocity vector and potentially many acceleration vectors.

It is very explicitly velocity and acceleration vectors:

LBB2'77, p25:
Each ship has a vector, which expresses that ship's velocity as a line (arrow) of a specific direction. For example, a ship might have a vector of 6 inches at 90°, or of 41⁄2 inches at 277°. It is possible to have a vector of 0 inches, whereupon the direction becomes irrelevant (in this case, the ship is stationary). Vectors are marked on the playing surface using string or soft wire. On some playing surfaces chalk can be used.

A ship's vector is the velocity vector. This is what we always have marked on the playing surface. It starts at the ship's current position and points in the direction of travel.


Changing the velocity vector is an acceleration:

LBB2'77, p25:
Acceleration involves altering a ship's vector by adding another to it; this new vector can come from thrust using the M-Drive, or from gravity. In either case, the method is the same. Vectors are added by placing them in a chain, head to tail, and drawing a new vector from the tail of the first to the head of the last.

Examples (LBB2'77. p25):

LBB2'77, p25:
Maneuver drive uses thrust to accelerate a ship in a specific direction for a specified distance. This direction and distance is expressed as an arrow (a line in one direction) called a vector.

An acceleration is a vector.
Drive acceleration and gravity acceleration vectors are temporary, they are removed when added to the ship's [velocity] vector.


So far basic Newtonian mechanics quantified into turns, I would call that pretty straightforward.
We have a position and a velocity vector. Changes in the velocity is acceleration, plotted as acceleration vectors.
Vectors are not just "displacement" vectors, they have a direct and explicit physical meaning.



How is this done?

LBB2'77, p26:
_ _ In a player’s movement phase, [1] he will indicate the acceleration (new vector) he wishes to apply, and note any gravitational influence vector he is required to apply, and then [2] add them to his ship’s present vector. His ship then [3] moves in the direction of its new vector, for the length of the vector. The vector then remains on the playing surface for reference during the next applicable movement phase.

Numbers in brackets added by me.
[0] We have a ship with a position and a [velocity] vector.
[1] We plot all the acceleration vectors. The velocity vector is unchanged. We have several vectors plotted.
[2] We add the acceleration vectors to the old velocity vector to form new the velocity vector. (The old vectors are removed.)
[3] We move the ship according to the updated velocity vector.

The rules say
"he will indicate the acceleration (new vector) he wishes to apply, "
the 100mm upwards
"and note any gravitational influence vector he is required to apply",
which by the rules as written are those at the midpoint of the new acceleration vector

No, it's the ship's vector = the velocity vector. The acceleration isn't added to the velocity vector yet.

LBB2'77, p29:
When the vector of a ship [ship's vector = velocity vector] passes through the gravity bands of a world, the gravity may alter that vector. During the movement phase, lay out the vector of the ship [ship's vector = velocity vector] to determine where it will move. If the exact midpoint of the vector lies in a gravity band, a gravity vector will be added to the course vector to create a new vector.

Gravity does not act on the drive acceleration vector, but the ship's vector = the velocity vector.
It's presumably an attempt to average the effect of gravity over the turn.

Take this simplified example of a ship passing a planet moving briskly:

It would make no sense to use the green acceleration vector to determine the effect of gravity?

The "construction" vectors are penciled in and then the resultant vector is drawn and takes place at the start of the turn for the sake of simplicity rather than the much more complicated displacement due to acceleration (the optional rule)

What you call "construction" vectors is what I (and LBB2) calls acceleration vectors?

The ship has a construction vector 100mm upwards which puts it in the 0.25g band, the construction vector is not on the surface.

The construction vector isn't added to the ship's vector = the velocity vector yet.
First you plot all the construction vectors, then you add them to the old ship's vector to form the new ship's vector.
You do not update the ship's vector until all the accelerations are plotted.



Like this, different example of a ship with a velocity close to a planet, no numbers:

 

[Spinward Flow]

The ship has a construction vector 100mm upwards which puts it in the 0.25g band

You do realize that what you just said is the equivalent of ... "gravity gets put on hold while the ship accelerates freely as far as it wants ... and only after the ship finishes moving does gravity turn back on again to have any effect at all" ... when launching from a planetary surface.

I consider my interpretation to be correct and yours to be the farfetched interpretation based on a misapplication or misunderstanding of the sequence as the rules are written.

I can't.

I can't even ...

I just ... can't.

 

[Grav_Moped]

You do realize that what you just said is the equivalent of ... "gravity gets put on hold while the ship accelerates freely as far as it wants ... and only after the ship finishes moving does gravity turn back on again to have any effect at all" ... when launching from a planetary surface.

He's discussing the rules as written in LBB2, rather than actual physics.