far-trader
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Thanks
Escaping gravity in Traveller
- Thread starter Michael Taylor
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Michael Taylor
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Quote: "How do those power to weight ratios convert to anything meaningful in Trav? (eg what's the power to weight ratio of a Suleiman, or a Far Trader)?"
They dont convert to anything meaningful Traveller. I was just looking at it from the perspective of how much thrust is equired to lift a rocket off.
They dont convert to anything meaningful Traveller. I was just looking at it from the perspective of how much thrust is equired to lift a rocket off.
M
Malenfant
Guest
Oh. Fair enough then 
. I just wondered if that P:W ratio told you how much acceleration something could have.
. I just wondered if that P:W ratio told you how much acceleration something could have.TheEngineer
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Well, for a given moment
acceleration = Power / (mass * velocity)
Thats the basic relation.
Michael posted:
Regards,
Mert
acceleration = Power / (mass * velocity)
Thats the basic relation.
Michael posted:
@Michael: What units are given here ?
Regards,
Mert
Michael Taylor
SOC-13
The units above are simply the ratio of thrust in Kg divided by weight at takeoff in kg. ie: Saturn V:
weight 2,912,925 kg at takeoff.
Thrust: 3,469,390 kg at takeoff.
weight 2,912,925 kg at takeoff.
Thrust: 3,469,390 kg at takeoff.
Just to have the pleasure to add something to this discussion:
The US spaceshuttle with the launch rocket can accelerate up to 5g.
Most humans can barely tolerate accelerations beyond 4g, and only for short times.
In hard sci-fi settings (without antigrav stuff), an acceleration of 1g in space could be sustained for extended durations (provided there is enough combustible for the thrusters), if the thrusters actually are "under the feet" of the crew rather than behind their back. This would provide effective Earth gravity. Accelerating at 2g or 3g for long periods would probably be unbearable in the long term.
Now a last guess: we are all used to thrusters in sci-fi, but this is hindering considering acceleration that people and material must endure, especially when you want to reach the speed of light quickly (okay, I know that most Traveller use space jumps). So lets invent a new propulsion system, probably based on gravity manipulation, that affects the whole starship instead of applying thrust to it. As such, everything would accelerate, and not being subject to the effects of thrust while in the starship (and so could sustain 4g, 5g, 10g, or more for any period of time).
Just my 2 g, ahem, I mean my 2 cents.
The US spaceshuttle with the launch rocket can accelerate up to 5g.
Most humans can barely tolerate accelerations beyond 4g, and only for short times.
In hard sci-fi settings (without antigrav stuff), an acceleration of 1g in space could be sustained for extended durations (provided there is enough combustible for the thrusters), if the thrusters actually are "under the feet" of the crew rather than behind their back. This would provide effective Earth gravity. Accelerating at 2g or 3g for long periods would probably be unbearable in the long term.
Now a last guess: we are all used to thrusters in sci-fi, but this is hindering considering acceleration that people and material must endure, especially when you want to reach the speed of light quickly (okay, I know that most Traveller use space jumps). So lets invent a new propulsion system, probably based on gravity manipulation, that affects the whole starship instead of applying thrust to it. As such, everything would accelerate, and not being subject to the effects of thrust while in the starship (and so could sustain 4g, 5g, 10g, or more for any period of time).
Just my 2 g, ahem, I mean my 2 cents.
TheEngineer
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Hi !
Thats an interesting comment.
Taking Megatraveller thrusters it might be completely logical, that they work just the way You described, especially because they ignore ships mass.
Any drive, which uses thrust in a classical way would also have to consider mass.
So we might call this version "freefall drive" as it results in zero-g conditions during collective acceleration.... cool
Thats an interesting comment.
Taking Megatraveller thrusters it might be completely logical, that they work just the way You described, especially because they ignore ships mass.
Any drive, which uses thrust in a classical way would also have to consider mass.
So we might call this version "freefall drive" as it results in zero-g conditions during collective acceleration.... cool
There is a RL physicist Alcubierre who describes the sort of "freefall drive" you describe, he wants to create asort of pocket around the ship, using an artificial singularity field, fore and aft, to destroy space ahead, create it behind, and the little pocket gets sort of sucked along, falling forward in the gap, quite scary to me.
It has some serious drawbacks, primum being the creation of this fake singularity field, but the math is fun, anyway, and serious minds are at least discussing alt space travel.
Sojourner
It has some serious drawbacks, primum being the creation of this fake singularity field, but the math is fun, anyway, and serious minds are at least discussing alt space travel.
Sojourner
BetterThanLife
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OK Stupid question time. I was under the impression that KG was a unit of mass. How do you have KG of thrust? And since KG is a unit of mass how do you have a weight in KG? Shouldn't both of those be in either pounds (for those of backwards Yanks) or newtons (for most of the rest of the world).
Let me guess. Massive Thrust?
The Drives needed on Any given ship when you design it requires you to install a certian amount of Drive units(2 units per every 100 Tons).
Remember the Mass measurement of the ship is weighted in displacement of hydrogen. If you was to weight the ship in Theory it will become lighter than its displacement (Weighted at 1G of gravity) therefor the drive is allready powerful enough to gain enought acceleration to reach the velocity to take of.
In theory the ship will take of at the equivelent of two times its own weight. The first will eqeal the Gravity (Based on Earths) the second will begin acceleration.
So a Ship with a 1-G Drive taking off on a planet of 3-G's will be accelerating at 1-G in 6 Starship Rounds and then begin launching.
Most of this looks complicated and it does. Any qeustions please ask.
Remember the Mass measurement of the ship is weighted in displacement of hydrogen. If you was to weight the ship in Theory it will become lighter than its displacement (Weighted at 1G of gravity) therefor the drive is allready powerful enough to gain enought acceleration to reach the velocity to take of.
In theory the ship will take of at the equivelent of two times its own weight. The first will eqeal the Gravity (Based on Earths) the second will begin acceleration.
So a Ship with a 1-G Drive taking off on a planet of 3-G's will be accelerating at 1-G in 6 Starship Rounds and then begin launching.
Most of this looks complicated and it does. Any qeustions please ask.
BetterThanLife
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I suppose he divided figures given in pounds (for us SI-impaired Yanks) by 2.2, yes?
I'm pretty sure the maximum thrust for Shuttle takeoff is 2G. There is a transient dynamic (including aerodynamic effects) stress peak of about 5G. </font>[/QUOTE]Well if it is pounds of thrust and pounds of loaded shuttle then the numbers work. Most people misuse kg for weight instead of mass. (Why, because it is convient since we are only measuring mass in the Earth's Gravity field at this time anyway. (So much for Mal's "The SI system is more accurate.") ) However there is no way to measure thrust in Kilograms. Thrust is force, not mass. (The other way to use pounds.) The only SI measure of thrust is Newtons. (Kilonewtons?) You are also dealing with Newton-Meters etc. But Kilos, and they say the Imperial system and those of us who use it are backwards.
BetterThanLife
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Pardon me while I poke a hole or two in your theory.
Doesn't Force = Mass times Accelleration. So Accelleration would therefore equal Force divided by mass. Weight doesn't enter into it. And in that case once you left the gravitational influence of the body you are leaving your accelleration would then be higher than the 1G of a minimum drive. Further an air/raft with an accelleration of .4g would never get off the ground. The same would hold true for overstressing the Maneuver Drive.
I suggest that a form of antigravity or contragravity exists and nullifies, at least partially, the starship's mass so it can get off the ground even with a lowly 1G accelleration. Remember that the 1G thrust can be fully applied on the horizontal (or perpendicular to the ground) so something else must be keeping the starship, or Grav Vehicle above the ground. And not many of the Canon ships are lifting bodies or have sufficeint lifting surfaces to work in an atmosphere. And many of the worlds in Traveller are atmosphere 0-1, so lifting surfaces wouldn't work anyway.
If your only source of lift was your engines than to get airborne you would need a thrust to weight ratio of greater than 1:1 or an accelleration of greater than 1 g-local. 1g-local may be greater than, less than or equal to 1G.
chrome_gnome
SOC-7
My impression on the contragrav theory is that the technology that fuels it is some kind of induction system. Almost like inducing a current in an electromagnet. I envision the anti grav "black box" takes the "pull" it feels and is able to tranfer most of it (~90%) to an opposite reaction. This allows even a 1G drive to pull away at nearly its full value.
This is one of the reasons I'm leaning towards not allowing any sort of "tractor beam" equipment to function againt grav vehicles or starships with grav technology. IMTU the harder the tractor pulls the more the grav units would turn the energy around and "push" it back towards the source. I may, after thinking it through, work on a kind of sliding scale, or ratio, of how much gravity a given unit can resist. Perhaps something like units that can conteract 1g-6g, so that you can specify the amount of grav power you want to pay for. If you are up against a planet with a 10g pull you just need a maneuver drive + grav rating that is equal or better than the 10g amount.
This is one of the reasons I'm leaning towards not allowing any sort of "tractor beam" equipment to function againt grav vehicles or starships with grav technology. IMTU the harder the tractor pulls the more the grav units would turn the energy around and "push" it back towards the source. I may, after thinking it through, work on a kind of sliding scale, or ratio, of how much gravity a given unit can resist. Perhaps something like units that can conteract 1g-6g, so that you can specify the amount of grav power you want to pay for. If you are up against a planet with a 10g pull you just need a maneuver drive + grav rating that is equal or better than the 10g amount.
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