More Gravity silliness

[infojunky]

Been pondering the various treatment of Gravity drives and their limits. In that they all have a point measured in diameters where the effectiveness drops off.

Couple this with what the standard orbit is implied which is somewhere near a single diameter of the world in question.

Looking at the need for a gravitational field to operate it occurs the the ratio of performance would drop with the decline in the local strength of gravity.

With this the traditional hour to orbit per planet size rating looks a lot more reasonable.

 

[mike wightman]

Why does the sun orbit the galactic core?

In the whole Traveller corpus there are several retcons that I consider to be ill thought out, stupid, setting changing, and just plain wrong.

Top of the list is limiting the range of the m-drive.

 

[AnotherDilbert]

Looking at the need for a gravitational field to operate it occurs the the ratio of performance would drop with the decline in the local strength of gravity.

Yes, presumably the "real" physics is a bit more complicated than the highly simplified game rules.

As it must be, to make the game playable...

 

[whulorigan]

I am sure the rationale behind limiting the range of the M-Drive was to deal with the problem of creating the proverbial unlimited-maximum-momentum based WMD phenomenon inherent in drives that do not need to carry their own propulsive reaction mass with them. The "Works at 100% efficiency to 1000-D and then drops to 0.01 efficiency beyond that" was probably just to keep the math simple for game play, rather than requiring players to interact with differential calculus derived travel formulas. (It also makes reaction drives such as HEPlaR still "a thing" even at higher TLs).

Now having said that (and keeping in mind that we do not know either the theory or the mathematics of the physics behind the engineering that makes the M-Drive work), it does not necessarily follow that just because gravity drops off as an inverse square (from a spherical and/or point source) in 4-D Normal Spacetime, that the interaction between the M-Drive mechanism and the manner in which it perceives the gravitational field (and/or other dimensional fields) in the regime in which they interact will also necessarily be in an inverse square relationship. For example, does the M-Drive perhaps touch on the interaction between gravity and J-Space in some way without entering it (or perceive other extra-dimensional spaces that interact with gravity such as in some String Theories) ? Mass/Gravity (i.e. Spacetime) and J-Space do relate to each other in some fashion, albeit non-linearly. Are there quantum-fields involved that are mediated by non-zero rest mass mediator virtual particles (like the Weak-Nuclear Interaction) and therefore have a limited range that drops off statistically based on both the random velocities and half-lives of the mediator particle type or types ? (Note that Marc's explanation of the sudden drop in efficiency to 0.01 @ 1000-D is due to quantum-fluctuations).

Just thoughts.

 

[Baroun Tardis]

I looked at the 1000D for M-drives (or 100D for G-drive, or 1D for Z-drives) as sort of like trying to drive a truck uphill
Up to a certain angle of inclination, you still have traction and continue to move along
At 90 degrees, though, you just hit the wall.

 

[Krikkitone]

I looked at the 1000D for M-drives (or 100D for G-drive, or 1D for Z-drives) as sort of like trying to drive a truck uphill
Up to a certain angle of inclination, you still have traction and continue to move along
At 90 degrees, though, you just hit the wall.

I like the “traction” metaphor… the drives need to “grip” onto the gravitational field, and if the field is to weak they can’t provide any push.

IMTU I modify them significantly (Z+G drives need more power/less thrust as they get greater speed with respect to the mass in 10 Ds… and M drives act like ‘field drive’ where they accelerate a field the ship is in rather than the ship itself..the field collapses as it gets close to another mass… this avoids the c speed WMD at least to a degree)

 

[whulorigan]

I looked at the 1000D for M-drives (or 100D 10D for G-drive, or 1D for Z-drives) as sort of like trying to drive a truck uphill
Up to a certain angle of inclination, you still have traction and continue to move along
At 90 degrees, though, you just hit the wall.

Perhaps this is why (in T5) the M-Drive needs a P-Plant with the ability to overclock like it does for a J-Drive: The farther you get from the gravity source, the more power gets drawn operating the drive until you hit a wall beyond which the power requirements blow up exponentially.

 

[Condottiere]

Push, pull, thrust, and lift.

Maybe manual gear shift?


edit: Eddaized it.

 

[whulorigan]

Maybe manual gear shift?

"Free Trader Beowulf needs assistance ... we have a busted clutch . . . "

 

[Grav_Moped]

Maybe manual gear shift?

"Free Trader Beowulf needs assistance ... we have a busted clutch . . . "

Some folks are just naturally shiftless.

Spoiler: This was a SF story's punchline

It involved uplifted apes trained as taxi drivers. In the end the apes qualified for welfare on a technicality after the project was shut down -- because they couldn't be trained to drive cars with manual transmissions.

Pretty sure it was published in Analog. Don't remember the author or year though.

 

[Baroun Tardis]

"Free Trader Beowulf needs assistance ... we have a busted clutch . . . "

I have this mental image of a thing sort of like a grav-chute but a little more powerful
It won't raise you, but you can "slip the clutch" to descend at a desired rate, or "take you foot off the pedal" and come to a stop

 

[Condottiere]

 

[whartung]

Ha ha! Not many going to get that "A Card" reference nowadays.

80(!!) years old. Wow.

 

[gchuck]

One of the best ones ever made!

 

[infojunky]

I have this mental image of a thing sort of like a grav-chute but a little more powerful
It won't raise you, but you can "slip the clutch" to descend at a desired rate, or "take you foot off the pedal" and come to a stop

Note that is in an issue of Journal....