Form follows function.

Discuss the Traveller RPG and its many settings
AnotherDilbert
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Re: Form follows function.

steve98052 wrote:
Mon Oct 29, 2018 6:35 pm
[*]The largest airliner, the Airbus 380, is about 50 dtons.
I get the fuselage to be about 200 Dt?

Height: 8.41 m
Width: 7.14 m
Length: ~60 m?
https://en.wikipedia.org/wiki/Airbus_A3 ... ifications

Volume roughly ≈ π × 8.41/2 × 7.14/2 × 60 ≈ 2 800 m³ ≈ 200 Dt.
Old School
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Re: Form follows function.

Steve, Something's definitely off. 747 is bigger than the space shuttle it carried, and the 380 is definitely bigger than the boeing.

As far as gravitation force at altitude, if I remember correctly, (and that's pretty iffy), it is a factor of inverse square of the radius (i.e. the distant from the gravitational center of the planet).

For example, from the center of the earth to the surface is roughly 6400 km. 6400 squared is 40,960,000. Double that and you get 819,200,000. Take the square root of that, and you are back to about 9,050 km. That means at an orbital altitude of 2,650 km (9,050 - 6,400), the gravitational force of the earth is halved.

If you want to do these calculations, just remember that the distance you are calculating from is the center of mass, not the surface. Or better yet, look it up, because I might be talking out of my rear end.
AnotherDilbert
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Re: Form follows function.

Sigtrygg wrote:
AnotherDilbert wrote: That is the only description of how M-drives work we have.
No it's not. HG79 fusion rockets, TNE HEPlaR, T4 reactionless with wording closer to T5 rather than MT.
HG'79 did not describe M-drives, just noted that they can be used as weapons. Nivenesque fusion rockets might be a natural assumption, but is not specified. Given that they consume a lot of power, but negligible fuel, they might more likely be some form of ion drive? Either way it was retconned away in 1980.
HEPlaR is explicitly not a traditional M-Drive, but something new. TNE Thruster Plates are classical M-drives.
I haven't seen T4, so I have no idea what it says...

Sigtrygg wrote: Handwaving 'gravitics' is a lot better than armshaking 'dampers, gravitics, brand new subatomic forces'
Handwave as handwave... Since we already handwave anti-grav ("manipulating sub-atomic forces") and dampers, the extra handwaving for thruster plates is minimal.

Sigtrygg wrote:
It might imply that the drive push against the local gravity field, and hence as a reaction the grav field pushes on the drive?
I can live with that
As far as I can see that might well describe M-drives in CT(1980+), MT, MgT and T5 alike.

I assume, perhaps a bit conveniently, that MTs reference to reactionless drive simply means "A reactionless drive is a device producing motion without the exhaust of a propellant" (wiki), not a strictly Physics definition.

Sigtrygg wrote: Only the 'canon' that contradicts all other canon and is needlessly complicated.
I do not see that the technical descriptions are detailed enough to actually be contradictionary.
Sigtrygg
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Re: Form follows function.

HG 79 'fusion drives as weapons' = fusion rocket
MT reactionless thrusters - only available at TL13+ with more handwavium than you can shake a stick at
Gravitic maneuver drives - a much better explanation for turning energy into momentum (GT, MgT))

hmm... E^2=m^2.c^4 + p^2.c^2

so we want to make momentum the subject
p^2.c^2=E^2 - m^2.c^4

That's the physics now go do the engineering
AnotherDilbert
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Re: Form follows function.

Sigtrygg wrote: HG 79 'fusion drives as weapons' = fusion rocket
Any drive that eject propellant is dangerous and can be used as a weapon. Try standing behind the business end of a current chemical rocket...

The problem is that HG'79 M-drives uses no fuel or propellant, so can't be rockets.

Quite possible, but that was abandoned in '79 or '80. At least for me, that started with CT'80, HEPlaR and M-drives that used propellant was new in TNE.

HEPlaR uses vastly more propellant than LBB2'77 M-drives, so can't be exactly the same thing.

Sigtrygg wrote: MT reactionless thrusters - only available at TL13+ with more handwavium than you can shake a stick at
Gravitic maneuver drives - a much better explanation for turning energy into momentum (GT, MgT))
TL13 is of course incorrect.

In what way exactly is MT M-drives different from CT'80, MgT, or T5 M-drives?
They all produce magical thrust without using fuel, and are based on gravitic (and possibly some more) technology.

I'm not familiar with GT, but:
A maneuver drive (M-Drive) is a reactionless thruster that produces thrust without fuel or reaction mass. Each module has a vectored reactionless thruster and a power-plant slice to run it.
In what way is that different from MT?

Nothing in MgT or T5 contradicts the explanations in MT, as far as I can see. Other editions just avoid details when discussing M-drives.
steve98052
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Re: Form follows function.

AnotherDilbert wrote:
Mon Oct 29, 2018 8:41 pm
steve98052 wrote:
Mon Oct 29, 2018 6:35 pm
• The largest airliner, the Airbus 380, is about 50 dtons.
I get the fuselage to be about 200 Dt?

Height: 8.41 m
Width: 7.14 m
Length: ~60 m?
https://en.wikipedia.org/wiki/Airbus_A3 ... ifications

Volume roughly ≈ π × 8.41/2 × 7.14/2 × 60 ≈ 2 800 m³ ≈ 200 Dt.
Oops! And . . .
Old School wrote:
Mon Oct 29, 2018 8:49 pm
Steve, Something's definitely off. 747 is bigger than the space shuttle it carried, and the 380 is definitely bigger than the boeing.
. . . Another oops!

It looks like I had a critical failure on my mental arithmetic roll. I probably used fuselage radius (or half-axis, in cases where fuselages are ellipses instead of circles) instead of diameter. I recall that I intended to just multiply height by width by length, instead of half-height by half-width by pi by length, to allow some extra for the wing volume. But maybe I did half-height by half-width by length. That seems consistent with my numbers compared to both of yours.
As far as gravitation force at altitude, if I remember correctly, (and that's pretty iffy), it is a factor of inverse square of the radius (i.e. the distant from the gravitational center of the planet). . . .
If you want to do these calculations, just remember that the distance you are calculating from is the center of mass, not the surface. Or better yet, look it up, because I might be talking out of my rear end.
The gravity formula is mass1 × mass2 × gravitational constant / distance^2.

But that only works for point masses, or at great enough distances that point mass is anacceptable approximation. Otherwise you have to integrate by mass/volume.

For example, imagine a spherical cloud of interstellar gas, 1 parsec in diameter, 100 solar masses. (Never mind whether that's a realistic size.) If you treat the cloud as a point mass, it's OK if you are calculating its gravitational pull on a star 20 parsecs away. But what if you're 1 AU from its center? Treating it as a point mass gives it 100 times the gravitational pull of the Sun at 1 AU. At 0.1 AU, it's 10k times the pull of the Sun at 1 AU. That doesn't make sense.

The problem is that the cloud is an extended object, and the mass in the direction of the center of mass is very nearly balanced by the mass in the opposite direction and any other direction.

So consider Jupiter at edge-of-space altitude. A volume of Jupiter gas at cloud-top altitude at the nearest point within Jupiter is quite a few times closer than an equal volume of Jupiter-gas at cloud-top altitude at the farthest point.So the nearest part of Jupiter exerts more gravitational force than the farthest point, and every part in between is different.

Making matters more complicated, Jupiter's density is not constant. At cloud-top altitude, it's low-density gas, but its overall density is more than that of water, because the core is so dense.

I don't know the density curve of Jupiter, but Earth has an average density of about five times water. The oceans are slightly more dense than pure water (because of the salts), surface rocks are typically 2.5 to 3 times water, and the mostly-iron core is about 12 times water. (Normally iron is about 7.9 times water, but Earth core iron is under extreme pressure.) Whatever is at the center of Jupiter is under much greater pressure, so iron there might be even more dense than 12 times water.
Sigtrygg
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Re: Form follows function.

The fuel use rate was mentioned in LBB2 77 edition, it even gives numbers from which you can extrapolate.
288 accelerations - divided by the turn length of 10 minutes means 48 hours of continuous thrust on a full fuel load
Note it also specifically states that smallcraft burn fuel when maneuvering at the rate of 10kg for each g of acceleration per 10 minutes.

My long time objection to the MT definition of how the m drive works is that it is complete cobblers and requires too many magic technologies and a brand new subatomic force that is not mentioned ever again - eat your heart out Star Trek technology of the week. Nuclear damper technology is TL12, so any drive application should be TL13+, and yet the magic maneuver drive of MT is TL11, a whole TL before damper technology is discovered. That sort of basic error is indicative of DGP getting ships wrong.

GT ISW says this:
Fortunately a better alternative is possible. At late TL8, new drives use power to generate forward thrust without needing to burn fuel or eject reaction mass. Such reactionless thrusters violate the laws of physics as understood in the early 21st century, but they make cheap, convenient space travel possible. Reactionless thrusters are the standard maneuver drive used by the Imperium, Terrans, and all other known spacefaring civilizations.
which I don't mind because it doesn't use pseudo scientific, setting contradictory technobabble to try and explain how it works.

I quite like that MgT says the m drive works on gravitic principles and leaves it at that.

But the MT definition? No, just no.
baithammer
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Re: Form follows function.

With the recent proof of gravity waves, it's not as far fetched as it once seen.
AnotherDilbert
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Re: Form follows function.

Sigtrygg wrote: The fuel use rate was mentioned in LBB2 77 edition, it even gives numbers from which you can extrapolate.
Yes, but that is changed in HG'79; M-drives use no fuel.

Sigtrygg wrote: My long time objection to the MT definition of how the m drive works is that it is complete cobblers and requires too many magic technologies and a brand new subatomic force that is not mentioned ever again - eat your heart out Star Trek technology of the week.
What is so exotic about the strong force (https://en.wikipedia.org/wiki/Strong_interaction), the basis of the Damper?
Old School
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Re: Form follows function.

Man, if people were as passoinate about playing Traveller as they were about arguing over what is Canon and what is valid science fiction vs magic, this would be the biggest rpg of all time.
AnotherDilbert
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Re: Form follows function.

If you want to see decades of heated arguments over petty details of canon head over to CotI...

Here, I hope I only occasionally fall into the trap:

https://xkcd.com/386/
Old School
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Re: Form follows function.

I know. COTI has a large following but not much activity, unfortunately. Traveller really is a small niche in the gaming universe.
Sigtrygg
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Re: Form follows function.

baithammer wrote:
Wed Oct 31, 2018 8:55 am
With the recent proof of gravity waves, it's not as far fetched as it once seen.
Gravity waves are a prediction from general relativity - proving yet again it is the best theory we have.

In general relativity gravity is not a force.

A handwavium drive that works by bending spacetime - not a full on warp drive but certainly similar - is 'plausible' technobabble for the workings of a reactionless drive that converts energy into motion.
Last edited by Sigtrygg on Wed Oct 31, 2018 6:46 pm, edited 1 time in total.
Sigtrygg
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Re: Form follows function.

AnotherDilbert wrote:
Wed Oct 31, 2018 9:38 am
Yes, but that is changed in HG'79; M-drives use no fuel.
Really? I must have missed the bit where it says ignore LBB2. LBB2 fuel use rates still apply for Hg79, it could be argued they still apply for Hg80 since there is nothing to contradict them. By CT81 the fuel use rate of ships and smallcraft have disappeared.
What is so exotic about the strong force (https://en.wikipedia.org/wiki/Strong_interaction), the basis of the Damper?
nothing, it's just not a TL11 development, it is at minimum a TL12 breakthrough. And there is no mention of the brand new subatomic force mentioned in the MT m-drive anywhere else in canon ever, not in MT or any other version.
Linwood
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Re: Form follows function.

Old School wrote:
Wed Oct 31, 2018 12:45 pm
Man, if people were as passoinate about playing Traveller as they were about arguing over what is Canon and what is valid science fiction vs magic, this would be the biggest rpg of all time.
Agreed!!!

I find many of the discussions interesting because they highlight elements of the game that I can use. But in the end I think more about whether the subject of the discussion fits in my campaign than whether it it is or is not canon.
AnotherDilbert
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Re: Form follows function.

Sigtrygg wrote: Really? I must have missed the bit where it says ignore LBB2.
HG'79 wrote:Fuel consumption for starships is inconsequential, and assumed to be part of the power plant consumption, regardless of the degree of maneuver undertaken.
So, the LBB2 fuel consumption is overridden, as far as I can see.

Sigtrygg wrote: nothing, it's just not a TL11 development, it is at minimum a TL12 breakthrough.
We don't know when the theory of Dampers were discovered. We only know that practical, small, reliable Dampers are available at TL12. Possibly the theory, or even prototypes, were known earlier, just as we know about fusion power but can't build a practical reactor.

Sigtrygg wrote: And there is no mention of the brand new subatomic force mentioned in the MT m-drive anywhere else in canon ever, not in MT or any other version.
There is no new unknown force, it's the strong and weak forces, as discussed in the SSOM, which is, I believe, canon.

There is no reason to believe that "sub-atomic force-based technology" implies a new unknown sub-atomic force.
Sigtrygg
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Re: Form follows function.

Inconsequential and no fuel at all are different - the first means it is used so little you can ignore it at the scale of starship operations, which is how it works in LBB2 too, the only difference being LBB2 gives a number from which you can calculate fuel use,
A fully fuelled power plant will enable a starship an effectively unlimited number of accelerations (at least 288)
288 10 minute burns or 48 hours of continuous use is pretty inconsequential to me.

We know dampers are a TL12 breakthrough, ship mounted dampers start at TL12, battlefield nuclear dampers are TL13. And yet the magical maneuver drive is developed from damper technology at TL11?
Artificial gravity and damper technology led to yet another sub-atomic force-based technology.
A technology based on yet another sub=atomic force - one that would never be mentioned or used for anything else ever again.
AnotherDilbert
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Re: Form follows function.

I apologise to sensitive readers, a non-native attempt at untangling English grammar will follow. I will try not to depend on the meaning of the word 'is'.
Sigtrygg wrote:
Artificial gravity and damper technology led to yet another sub-atomic force-based technology.
A technology based on yet another sub=atomic force - one that would never be mentioned or used for anything else ever again.
I'm not a native English-speaker, but I read it as "yet another { sub-atomic force-based } technology" meaning 'yet another technology based on one or several sub-atomic forces'.

When we stack a series of adjectives they all refer to the following noun, technology in this case. I assume "sub-atomic force" is used as a single phrase, so "sub-atomic force-based" is a single compound adjective (properly sub-atomic-force-based?), otherwise it would be a 'force-based, sub-atomic technology'? I see no reason to assume all the adjectives form a single compound cumulative adjective (yet-another-sub-atomic-force-based?), if there even is such a thing?

The context is list of breakthrough technologies, so 'yet another' makes more sense referring to technology.

It is confirmed later (in SSOM) that thrusters are based on known sub-atomic forces.

If I say "yet another oil-based paint" do I refer to another paint or another, hitherto unknown, oil?
Old School
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Re: Form follows function.

Ya’ll just need to stop. JMISBEST’s post are better than this.
AnotherDilbert
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Re: Form follows function.

Sigtrygg wrote: Inconsequential and no fuel at all are different - the first means it is used so little you can ignore it at the scale of starship operations, which is how it works in LBB2 too, the only difference being LBB2 gives a number from which you can calculate fuel use,
A single burn is inconsequential, but accelerating for a few days means that something runs out which is hardly inconsequential.

LBB2'77 says we can accelerate for a few days.
HG'77 says we can accelerate for a few weeks, regardless how much we burn.
It is not the same.

Either case the propellant consumption is much too small to support a fusion rocket, which, I believe, was the point we discussed?

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