Maneuver Drive - How does it work?

[mctesla]

Originally posted by Anthony:
There are other issues with the alcubierre warp drive, such as the planetary masses of exotic matter and boundary conditions that will rip nuclei apart.

Interesting-- based on my reading, the exotic matter was only necessary when the FTL geometry was involved, and similarly the boundry deformation lessened the "slower" the ship went. Where did you get your info? (Truly curious)

 

[archhealer]

IMTU, they are not actually reactionless. The energy from the power plant is used to create a reaction (This is deliberately vague, as different technologis, worlds, races use different types of reactions) that is pushed out behind the plates and allowed to 'explode'. The plates mainly just prevent the explosion from damaging the ship, allowing it instead to be pushed forward.

Yes, there are MANY problems with this.

But, it explains glowing thrusters on the back of the ship, and makes standing right behind them dangerous.

 

[boomslang]

Originally posted by Bromgrev:
One thing which continues to bug me ... why do all Traveller ships have great big glowing engine nozzles?

It's probably the heat dump off of that 1-million-degree hot fusion powerplant. It'll need to be diffused and radiated away as efficiently as possible, or else the vessel will be way too easy to track via infrared from light-hours away...

 

[boomslang]

Originally posted by Valarian:

Drive fields manipulate relative local gravitational balances. The ship is moved in relation to local gravitational sources. If the drive field goes down, there is no momentum to conserve as the ship is just stuck in its current relational position. [God help you if you have drive plates and misjump to deep space - the maneuver drive won't work as there's not enough local gravity to manipulate]

I too subscribe to the "gravitic m-drive creates an encompassing field around the ship and then accelerates everything within that field bubble uniformly" model, but I have the drive field push against the inertial mass of the rest of the Universe. The vessel, being the relatively less-massive object, is then the one that gets moved.

I'm simply using a broader definition of "local" gravitation than you...

 

[Uncle Bob]

I use this myself, sometimes called a Mach's principle or Impulse drive. Dr James Woodward was working on a drive on those principles, i.e. pushing against the background mass of the Universe. Dr John Cramer was looking into it for NASA's Breakthough Physics office.
http://chaos.fullerton.edu/~jimw/nasa-pap/

It seems more plausable given the new "Process physics", but the energy costs will be enormous.

And the glowing exhaust? White-hot, highly efficient radiators getting rid of waste heat from the power plant.

 

[boomslang]

Originally posted by Uncle Bob:
It seems more plausable given the new "Process physics", but the energy costs will be enormous.

I expect that this is where the real breakthrough lies: devising an efficient engineering solution... or "relatively" efficient, given the required fusion powerplant to make it go.

In addition, I am inclined to preserve the traditional "contragravity" model as an alternative, lower-thrust higher-efficiency model of gravitics operations to explain the perfomance envelope and high endurancee of vehicles like the air/raft. Rather than externalizing the Mach Principle (used in interplanetary flight), a grav unit operating in contragravity mode simply creates an internal field which opposes the gradient of the local gravity field, thus "neutralizing" it and even creating a certain "bouyancy" within the module to lift (and by introducing a modulated assymetry into the field, propel) the module and whatever it's attached to. The tradeoff would be much lower performance (say, -2Gs max), in exchange for much lower energy input requirements (air/rafts run on fuel cells or somesuch), but only in the presence of a significant external grav field (such a planet generates)...

But I'm still mulling that detail over...

 

[Uncle Bob]

Even simpler, IMTU the Airraft has an engine that generates an artificial mass of -4 tons. For propulsion and maneuver this can be adjusted up and down, energy cost depends on movement resulting.

Dr Robert Forward has described a mechanism for doing this by "dragging the metric" with a toroidal mass rapidly rotating inside-out "like a smoke-ring", but at relatavistic speeds. This would generate an apparent mass of x tons from one direction and -x tons from the other.

 

[Laryssa]

A traveller maneuver drive pushes a volume rather than a mass. 1 unit per 50 tons, and they come in 6 types, 1-G to 6-G, they don't produce units of thrust, the mass of their payload doesn't matter, just as long as it fits withint the required volume. It is space dragging.

 

[Straybow]

Originally posted by Valarian:
Does anyone use the "drive field" concept (Honor Harington / Starfire series) where, if the drive field is lost, the ship is dead in space? The drive seems to work by "riding" the ship on a gravity wave (similar I suppose to MagLev).

Which do people think is most plausible for a reactionless drive technology?

Which do people think has most possibilities in game terms?

Errrmm, the sub-light propulsion system in the Honorverse is projected regions of intense gravitational warping. Between the "grav bands" or "grav walls" the grav effects cancel out, or nearly so as the bands are oriented at a slight converging angle towards the stern. Outside the bands the canted angle produces a net acceleration on the order of thousands of Gs.

If disabled momentum is conserved, but compared to a ship maneuvering at 1000 G the driveless ship is indeed dead in space.

Mach's Principle is that the universe is pulling on everything all the time, that inertia itself is the "drag" of the mass of the universe. The application of Mach to maneuver drive is the idea of blocking the pull of one part of the universe. The result is a net acceleration in the opposite direction that is proportional to the efficiency of the screen.

The vessel is effectively in free-fall, so no stresses are introduced to the structure or occupants. Perhaps the screen can be implimented with a gradient for deck grav and i-comp.

 

[Ptah]

Originally posted by boomslang:
I too subscribe to the "gravitic m-drive creates an encompassing field around the ship and then accelerates everything within that field bubble uniformly" model, but I have the drive field push against the inertial mass of the rest of the Universe. The vessel, being the relatively less-massive object, is then the one that gets moved.

I'm simply using a broader definition of "local" gravitation than you...

If I udnerstand this correctly, pretty much how I view it as well.

 

[mike wightman]

One of the other things a Traveller maneuver drive does is to project a field that protects the ship from radiation. This is mentioned in Beltstrike.

This article, and this article I've posted before have got me thinking about the maneuver drive again.

I stick by my inertial mass reduction field component (needed to allow multiple Gs of acceleration), but now have the ship surrounded by a plasma field.
This explains why the power plant/maneuver drive combo needs so much hydrogen.

Next thought, the plasma shield article has me thinking that stealthy ships could be introduced into Traveller, and that perhaps plasma armour could be used to defend against lasers, energy weapons, and particle beams...

I may have to start a new thread on all this

 

[boomslang]

Originally posted by Sigg Oddra:
Next thought, the plasma shield article has me thinking that stealthy ships could be introduced into Traveller, and that perhaps plasma armour could be used to defend against lasers, energy weapons, and particle beams...

The idea of plasma armour sounds interesting, but as for stealth, it won't matter -- you'll still have to dump heat like a black body, and therefore you'll have an IR signature. Arguably, an easier-seen one than if you could nominally radiate heat unidirectionally, such as via directed exhaust ports astern. Stealth in Traveller pretty much requires either a flickering Black Globe or cold coasting while pulling a Dishkili Maneuver... it's those darned Thermodynamics Laws, they betray your presence every time against the icy black background.

(Also note that densitometers can detect grav drives in operation, so there's another headache to deal with.)

But the defensive "plasma screen" notion holds promise, especially against PAWs and missiles, I'd expect. Probably about the same as sand versus lasers...

 

[mike wightman]

A directed plasma exhaust to stern... could a giant chill can be used to cool it down

I was thinking of the cold coasting maneuver, surrounded by the plasma to mimic background heat. Any use of the maneuver drive within a couple of light seconds of a sentry ship is an instant give away...

 

[Pickles]

Depending on the amount of heat to be dumped, it could be pumped into a heat sink (like a big coil or something - don't bring me down with physics now), which could be ejected at an opportune moment. The idea stems from Kim Stanley Robinson's Mars books, although there it was used for stealth ATVs.

 

[mike wightman]

Attack Vector: Tactical has sodium and/or lithium heat sinks...

 

[boomslang]

Originally posted by Sigg Oddra:
A directed plasma exhaust to stern... could a giant chill can be used to cool it down

Ah, yes... a giant can of Freon; cheaply and easily come by, no doubt...

I was thinking about some sort of radiator array using a baffle system to emit a broad, semi-coherent IR beam (with the modest helium exhaust dumped in too, simply because it has to go overboard somewhere) in more-or-less one controlled direction.

Ideally, this directed-radiation beam would be both as diffuse as possible and hard to detect off-axis... focussing it to an intensity suitable for weapon applications would be discouraged since it would consequently make the radiator baffles hot enough to detect off-axis (as well as cutting into their efficiency, and therefore reducing the output available).

But, being mostly unidirectional, it then becomes trivial to simply keep it pointing away from one's opponent -- and thereby hide one's heat signature, by and large.

 

[mike wightman]

I like it

 

[boomslang]

Originally posted by boomslang:
But, being mostly unidirectional, it then becomes trivial to simply keep it pointing away from one's opponent -- and thereby hide one's heat signature, by and large.

And when operating in an atmosphere which the radiated heat would be absorbed by (thus increasing one's heat signature), one would simply open the fuel scoops (standard on all BT streamlined designs, optional on CT High Guard streamlined designs, YMMV in other Trav editions) and instead of running them in "compress" mode, operate them in "bypass" mode, blowing a nice fresh exhaust breeze over the aforementioned radiator array for more diffusive cooling...

 

[sarahnewton]

Hi all,

I've been thinking about manoeuvre drive and its relationship to contragrav, specifically with reference to streamlining on ships for takeoff and landing. Apologies if this has been done to death already - please point me to a good answer if there is one!

Here's the conundrum: the OTU says that non-streamlined ships can't land or takeoff on worlds with an atmosphere. However, the OTU also says that airrafts and other grav vehicles (and by implication grav-floating cities too - my assumption) can reach orbit "in a few hours" on worlds with an atmosphere. Is there a good reason why non-streamlined ships can't use contragrav to lift off from a planet with an atmosphere and then switch to their m-drives when in orbit?

I thought to start with that maybe the contragrav modules are huge & won't "fit" in a hull together with a powerplant, mdrive, jdrive, etc - however, looking at pretty much any Traveller version (I'm quoting T20), the contragrav modules are pretty small - in T20 about 5% of overall mass.

Any thoughts? Handwavery required, or is there a proper reason Out There?

Happy travelling!

Sarah

 

[boomslang]

Originally posted by Shaira:
Any thoughts? Handwavery required, or is there a proper reason Out There?

IMTU, I have a scheme which tries to minimize the handwaving.

I figure grav drives have two different modes of operation available: direct thrust and contragrav. Contragrav is the simpler and more fuel-efficient mode, and is the one used by air/rafts and other low-performance flying machines (with their ten-week operational durations). Contragrav requires the presence of an external gravity field to "counter", and has a maximum lift/thrust of 2Gs total (as floor plates). Note that the higher one lifts in altitude, the less-efficient contragrav becomes; it's effectively useless in deep space.

IMTU, unstreamlined ships (other than dispersed structures) may use contragrav to perform as air/rafts within planetary atmospheres. Perhaps more importantly, vessels with m-drive ratings of 1G can use contragrav mode to make air/raft-style takeoffs and landings at worlds with greater than 1G surface gravity (up to the 2G limit of contragrav mode).

Direct thrust mode operates as a proper "reactionless drive" and is used to propel a ship at its rated drive performance regardless of local gravity fields, but at a higher power cost. I also hypothesize that grav tech is somehow associated with jump tech -- that one breakthrough led to the other. For ships displacing greater than 100 dtons and mounting computers, it is possible to create a "bubble" or "pocket" with the m-drive that is stable enough to provide acceleration compensation to everything within it -- the gravitics accelerate everything with the field encompassing the ship smoothly. Smaller vessels (small craft), even if they mount computers, aren't big enough to form a stable field, and so rely upon "acceleration couches" for safety. Regardless of whether the ship is big enough to form an acceleration compensation effect, any spaceship m-drive produces enough of a field to give the radiation and micrometeroid protection noted in Beltstrike.

That's the simplest, yet most comprehensive, explanation I've cooked up... and it has the side benefit of suggesting a reason that j-drives need a minimum 100 dtons of displacement and don't work well in external gravity fields...