1G ship on a 10G world....

[Spinward Flow]

They just cancel out most of the gravitational acceleration, somehow.

COSTCO had a clearance sale on Magic Carpets™ ... so ...

 

[bookwyrm]

Without knowing either the mass or the mean density of the world, the question is unanswerable.

If the world’s mass is known, then g = GM ⁄ (r ²), where g is the surface gravity, G is the gravitational constant, M is the world’s mass, and r is the world’s radius.

If the world’s mean density is known, then g = (4π ⁄ 3) Gρr, where g, G, and r are as above, and ρ is the world’s mean density.

A 10 G world means g = 98.0665 m ⁄ s². The gravitational constant G = 6.67430(15)×10⁻¹¹ m³ ⁄ (s² kg). Fill in your choice of M kg (world mass) or ρ kg ⁄ m³ (world mean density), solve for the radius r, and the diameter will be 2r.

I mean in Traveller Terms. We know the radius of worlds from size 1 to A with their 'gravity', and some Traveller rule sets have higher sized worlds.

Well, using my T20 World Builder, a 10G world would have a diameter of 128,000 km? Umm, about 19.88 hours to get from the 100 radius to the planet, and 19.88 hours to reach jump at 1G? 19.88 hours seems like a lot of time to consider the effects of a 10G world on the delicate ship you're thinking of landing with and the more delicate 'things' inside that delicate ship. Hope nothing important breaks down...

 

[aramis]

What happens if you have a 1G acceleration ship and it lands on a 10G world?

My answer:

You just take off. Once Contra-grav is there, the field surrounding your ship is whatever gravity you want and so therefore you can take off and land without issues since you have nullified the local gravity. Escape velocity and mass become irrelevant with Contra-grav technology.

Reference: H. Beam Piper
either Cosmic Computer, Space Viking, or Four Day Planet.

In TNE, you can do that to about 18G... at ever increasingly slow accelerations.
In MT, with SSOM, you can get off a world up to 4G with a 1g drive... if you've a good engineer... and up to 2 g fairly reliably.

IMTU, I use the MT paradigm. Exceed that, and you first aerobrake and then hydrobrake &/or lithobrake.

 

[kilemall]

So, basically ...

LBB2 put Sir Isaac Newton in the pilot's acceleration couch for maneuvering around.

MT told Sir Isaac Newton to "take a hike" and locked him outside the airlock as soon as he left.
TNE told Sir Isaac Newton "we don't serve your kind here" before making it rather obvious there was guillotine waiting for him if he lingered for being a public nuisance.

Makes perfect sense.

Story/game engineering not SCIENCE fiction.

 

[Dragoner]

We had a shuttle launch simulator in school that was a trigonometry teaching tool, it would be hilarious for a moment to hand the player a trig problem, only a moment though, I'm sure they would say no.

 

[infojunky]

From Adventure 12, page 19.

Explorers: The added strength required to move and function in greater than 1G is easily understood by most people, and it is formidable.
It is also manageable with sufficiently advanced technology. Technology easily overcomes the problem through the use of grav modules. Heavy duty grav modules
neutralize the pull of gravity, making it possible for an individual to function normally. A standard grav belt is available at TL 12, costs Cr100,000, and can lift 200
kilograms against 1.5 gravities.

This section seems to imply that Grav Modules screen a given mass up to a given gravity.

I must note as per Book5 the max amount of gravity/thrust is limited to 6g. As thrust is limited by compensation.

Looking at Book3, an air/raft uses 4 modules that appear to cancel 8 tons of mass (Nominally more, but note a number to quibble about). These 4 modules provide the nominal thrust for maneuver.

 

[AnotherDilbert]

Looking at Book3, an air/raft uses 4 modules that appear to cancel 8 tons of mass (Nominally more, but note a number to quibble about). These 4 modules provide the nominal thrust for maneuver.

There's no magic mass manipulation, just thrust in CT:

LBB3'77, p17:
Air/Raft (8) CR 6,000,000. Also known as a flier, the air/raft relies on solid state null gravity modules for lift and propulsion. Four independent, individually replaceable modules (CR 1,000,000 each) insure a maximum of safety. Loss of one module reduces lift by one-quarter.

Lift & propulsion is force, thrust.

 

[infojunky]

There's no magic mass manipulation, just thrust in CT:

Go back and read the quote. Page 16 not 19... sorry typo. (actually read the page from the tiled pages of the PDF and not the actual books page number)

Lift & propulsion is force, thrust.

Well that is a simplistic why to look at it. In that there is the function of negating the gravity arrow, and a function of providing an external arrow of thrust. One does not necessarily mean the other . Also note the reduction of felt gravity in the example from Adventure 12.

It helps it you draw out the relative force arrows.

To be clear I get your point.

 

[AnotherDilbert]

Well that is a simplistic why to look at it.

It's the definition?

CT A12, p17:
A standard grav belt is available at TL 12, costs Cr100,000, and can lift 200 kilograms against 1.5 gravities.

CT A12, p17:
The best source of heavy duty grav modules is an airlraft. An available air/raft can be cannibalized to provide four modules, or replacement parts can be bought from a supplier. Each module costs Cr110,000, weighs 30kg, and can lift 200 kg against 2Gs.

It's lift, a force. No mass manipulation or decoupling from the geometry of curved space-time.

To be clear I get your point.

I think I get your point too, I just don't see any support for it in CT.

If that's how you want it to work, that's of course how it works IYTU, it just wasn't in the LBBs.

 

[Kakistocrat]

I mean [the diameter of a 10 G world] in Traveller Terms. […] using my T20 World Builder, a 10G world would have a diameter of 128,000 km?

For a world with the same mean density as Earth, I calculated a diameter of 127,243.86 km, or 79,065.669 mi, so your T20 World Builder must be presuming a world with approximately the same mean density as Earth.

In Traveller terms, 1977 Book 2, p. 26 has planetary formulae, the first two of of which are R = D ⁄ 2 and G = K (R ⁄ 4). Since 1 D = a diameter of 1,000 mi, 1 G = Earth gravity, and 1 K = mean Earth density, combine these two formulae to make G = K (D ⁄ 8), which leads to D = 8 G ⁄ K, or D = 8 × 10 ⁄ 1 (for a world with the same mean density as Earth) = 80 = a diameter of 80,000 mi, or 128,747.52 km. Since D typically comes from the size digit of a UWP, a D of 80 is literally off of the Book 6, p. 26 size table. To get the D of a 10 G world back onto the size table, increase K accordingly.

 

[infojunky]

Page 18....
Grav Modules: Two airlraft grav mod- ules effectively negate local gravity of 3Gs. If one module fails, each action by a character expends one endurance point (regained by resting) and endur- ance or less must be thrown first, and the wearer drops at the rate of 15 meters per second per second. If both fail, the wearer is immobilized and drops at 30 meters per second per second.

Which does imply my supossion...

Though I must remind you, this is Traveller, as such both of our opinions can be correct.

 

[infojunky]

It's lift, a force. No mass manipulation or decoupling from the geometry of curved space-time.

Actually both of our suppositions do alter the geometry of Space-Time. Difference is how it does.

 

[Spinward Flow]

Which does imply my suppossion...

Let me tell you a joke.
Somebody apparently once went up to the great philosopher Wittgenstein and said:

• "What a lot of morons people back in the Middle Ages must have been to have looked every morning at what's going on behind me now, the dawn, and to have thought that what they were seeing was the Sun going round the Earth. When as every school kid knows the Earth goes round the Sun, and it doesn't take too many brains to understand that!"

To which Wittgenstein replied:

• "Yeah. But I wonder what it would have looked like if the Sun HAD been going round the earth?"

Point being, of course, it would have looked exactly the same.
You SEE what your knowledge TELLS YOU you're seeing.



Credit to James Burke for the anecdote that opens Episode 1 of The Day The Universe Changed series ... which explains, so succinctly, how depending on your assumptions and what you "know" two different people can come to entirely opposite conclusions based on the same observations of reality.

as such both of our opinions can be correct.

"The customer is ALWAYS RIGHT ... until computers are involved."
- Me, reeling off yet another one of my personal catchphrases

 

[aramis]

Actually both of our suppositions do alter the geometry of Space-Time. Difference is how it does.

Or assumes an outscale reaction mass.

If gravitics work by accelerating oppositely the plate and the massive object whose well it is most affected by, there's no alteration in the geometry, but a definite alteration of methodology of traversing it.

This is implied in later editions by the the limits on use of various grade gravitics. IIRC, the first gravitic drives have a 1 diameter AMSL (above mean surface limit). the first gravitic space drives have an explict in errata 10D AMSL limit; the full up M drive drops at 1000 diameters (which puts Sol's at just shy of Jupiter's orbit... and Jupiter's own big enough that it's hard to miss.)...

There are hints of this in several adventures, most especially A12... but CT is maddeningly vague on operational means of the black box technologies.

 

[infojunky]

There are hints of this in several adventures, most especially A12... but CT is maddeningly vague on operational means of the black box technologies.

Honestly this is my point. CT implied several different methods.

MT/TNE listed at least 4.

T5 has 3ish... In a lot of ways it goes back to the CT model.

I will argue the differences, but still this is Traveller, what works at your table might work differently at mine.

 

[kilemall]

Honestly this is my point. CT implied several different methods.

MT/TNE listed at least 4.

T5 has 3ish... In a lot of ways it goes back to the CT model.

I will argue the differences, but still this is Traveller, what works at your table might work differently at mine.

I expect that’s the point of the vagueness.

 

[Enoki]

If the hull of your ship is only rated for 8G there might be a problem...

 

[AnotherDilbert]

Actually both of our suppositions do alter the geometry of Space-Time. Difference is how it does.

Not as far as I can see: Agrav as thrust does not alter or decouple from the geometry of curved space-time anymore than a jet engine or helicopter rotor.

 

[AnotherDilbert]

Grav Modules: Two air/raft grav modules effectively negate local gravity of 3Gs.

Which does imply my supossion...

I do not see it: "effectively negate" means not really negate, but with the same effect, e.g. by opposing the downwards gravitational acceleration with an upward acceleration.

If it did negate the gravity, the object would become buoyant and rise in the thick atmosphere deep in the gas giant.

Though I must remind you, this is Traveller, as such both of our opinions can be correct.

Agreed, and both our opinions could be incorrect.

I have no special knowledge or insight, but can only read the books...


I case of uncertainty I would look at the basics, such as:

CT LBB3'77, p17:
Air/Raft (8) CR 6,000,000. Also known as a flier, the air/raft relies on solid state null gravity modules for lift and propulsion.

CT Striker, B3, p8:
K. Grav Generators: A grav vehicle requires grav generators installed in its chassis. Each .02 m³ of grav generators produces 1 ton of thrust and requires .1 megawatts of power from the power plant. They weigh 2 tons and cost Cr100,000 per m³.

If you do not like that, by all means change it IYTU.

 

[aramis]

I do not see it: "effectively negate" means not really negate, but with the same effect, e.g. by opposing the downwards gravitational acceleration with an upward acceleration.

TTNE's Contragrav Field (CGF) creates an interesting physics divergence that there's no current way to check: a difference in Inertial mass and gravitic mass.
AS in, the field reduces only the gravitic mass, but the thrust to accelerate by other means than flotation is not reduced by CGFs (and noting that MSL STP is SG=0.001225, and a typical TNE nonwarship ship is SG=(0.5 ... 0.75) - multiplying that by FF&S' "over 99%" ¹ ... gives SG=(0.005...0.00714) - about 5 to 6.5 times the displaced volume. It won't float, but it can allow you to crash surface a boomer as fast as the hull can slip water...
If that "over 99%" is pused to 99.5%, lighter CGF enabled ships (mostly tankers or passenger liners) can get one to about 5.5 km on Earth by atmospheric displacement flotation - a safe enough level to turn on the HEPlaR.

---

1: FF&S 1, p23, §"Step 2: Suspension":

Contra-gm negates the gravitational force of over 99% of the vehicle's weight This allows light lift vehicles to actually be buoyant on worlds with sufficiently dense atmospheres.