Reentry and landing.

[Grav_Moped]

I guess you'll have to spell it out for me as it's not so clear to me that turning gravity 'off and on' would translate to an effective drive.


Only thing that comes to mind is that the ship generates gravity forward of the ship and the ship 'falls' towards the artificial gravity. The classic 6G limit then becomes whatever the limit is to generate that much gravity, indeed it starts sounding awfully Alcubierre.


If one had a drive capable of that, then that would make for quite a potential for defending against missiles and possibly creating confusing signal returns for enemy sensors.

First pass at the problem:

Assume a box containing a 1-ton mass mostly loose within it, with a large compression spring between it and the top of the box.

Turn on artificial gravity in the "upward" direction until the spring compresses. Turn it off, let the spring expand and apply its force to the top of the box and drive the 1-ton mass downward. Turn artificial gravity back on again, and repeat.

This is a reactionless thruster.

 

[kilemall]

First pass at the problem:

Assume a box containing a 1-ton mass mostly loose within it, with a large compression spring between it and the top of the box.

Turn on artificial gravity in the "upward" direction until the spring compresses. Turn it off, let the spring expand and apply its force to the top of the box and drive the 1-ton mass downward. Turn artificial gravity back on again, and repeat.

This is a reactionless thruster.

Er.


Feels kind of perpetual motion to me.



You have the input of the gravitic hoohaw 'winding up the spring' which I gather is metaphorical for stored/released energy (at least I hope so), and sounds like 'thruster plates', I suppose a high cycling gravitic compression/release.

 

[Grav_Moped]

Pretty much, yes. You could probably make something like the Dean Drive work with that, too (which otherwise, it won't, due to conservation of energy).

And a canon air/raft is a perpetual motion machine (or at the very least you could build one around it): 10 days of being able to lift 4 tons? 4000L water tank in the back, fill at ground level, lift to the top of a water tower and pour it in, land, refill, repeat for a week. Put a turbine-driven generator at the base of the tower and Bob's your uncle.

The canon maneuver drives have the same issue.

 

[Ulsyus]

Pretty much, yes. You could probably make something like the Dean Drive work with that, too (which otherwise, it won't, due to conservation of energy).

And a canon air/raft is a perpetual motion machine (or at the very least you could build one around it): 10 days of being able to lift 4 tons? 4000L water tank in the back, fill at ground level, lift to the top of a water tower and pour it in, land, refill, repeat for a week. Put a turbine-driven generator at the base of the tower and Bob's your uncle.

The canon maneuver drives have the same issue.

But what's the energy equation in all that? If the water, via the turbine, generates less power than was used to lift the water with an AG vehicle, it's not perpetual. Has anyone got the power plant specs on an air raft?

 

[whartung]

Turn on artificial gravity in the "upward" direction until the spring compresses. Turn it off, let the spring expand and apply its force to the top of the box and drive the 1-ton mass downward. Turn artificial gravity back on again, and repeat.

"Full power!", barked the Captain.

The pilot shoved the thrust level forward, and the ship began to resonate with the comforting "thump thump thump" of the reaction less gravity drive...

 

[Grav_Moped]

"Full power!", barked the Captain.

The pilot shoved the thrust level forward, and the ship began to resonate with the comforting "thump thump thump" of the reaction less gravity drive...

Maps pretty well into A. Bertram Chandler's Rim Worlds / John Grimes universe, if I remember correctly. ("Inertial drive"?)

 

[Grav_Moped]

But what's the energy equation in all that? If the water, via the turbine, generates less power than was used to lift the water with an AG vehicle, it's not perpetual. Has anyone got the power plant specs on an air raft?

I mis-remembered, endurance is 10 weeks, not 10 days.

"Range in time or distance is effectively unlimited, requiring refueling from a ship's power plant every ten weeks or so" -- LBB3 ('81) p. 23.

Ok, it "refuels" from a ship's power plant. This makes sense from the standpoint of a starship-oriented game universe but raises the questions of what form of refueling is involved, how one refuels if one lacks access to a ship, and how long such refueling takes.

Did later editions or rules cover this in greater detail? I suppose you could replicate it under Striker's design sequence to get some sense of what the energy requirements should be, but the LBBs don't cover it. Might be worth checking against LBB2('77) small craft fuel consumption rates as well.

I'm starting to think this air/raft (and grav-vehicle in general) discussion warrants its own thread, as it's a side-track from the original topic.

 

[JimMarn]

Maps pretty well into A. Bertram Chandler's Rim Worlds / John Grimes universe, if I remember correctly. ("Inertial drive"?)

Some of my fave stories. Mr. Chandler was a tramp freighter captain in the Southeast Pacific area. ( North of Australia)

 

[Straybow]

Neat, take it up with the render artist. My objective was to clarify the classic rendering of the form factors in question between his description of what sounded like a Type R vs. a Type A.

Actually, my first point was about making the pic a link in a thumbnail so it doesn't break the thread format for those who don't have 1920 display. Please do...


It seems to me that the scale of the person would very much dictate the scale of the ship.

 

[aramis]

Actually, my first point was about making the pic a link in a thumbnail so it doesn't break the thread format for those who don't have 1920 display. Please do...


It seems to me that the scale of the person would very much dictate the scale of the ship.

Or at least use the [IMGW=800]url[/IMGW] instead of the [IMG]url[/IMG] one.

 

[BlackBat242]

Maps pretty well into A. Bertram Chandler's Rim Worlds / John Grimes universe, if I remember correctly. ("Inertial drive"?)

His primary FTL drive...

"Mannschenn Drive-off!" Down in the Mannschenn Drive room the spinning, precessing gyroscopes slowed to a halt, their thin, high whine dropped to a low humming, a rumble, then was silenced.

Manschenn Drive, a time and space distorting gyroscopic affair made with a purely mechanical (as in, gears and wheels and spinning moebius strip gyroscope rotors) realspace FTL that works because it's a reactionless drive and a time machine. The drive ‘moves ahead in space while moving backwards in time’. You travel at sublight velocities, but you’re pushed steadily back in time so that you have a faster-than-light pseudovelocity.*

He created two more for his Grimes universe:
Ehrenhaft Drive – took mankind on its initial expansion to the stars. The ED essentially turns itself and the vessel to which it is attached into a charged magnetic particle, which then travels along the ‘force lines’ between stars.
This drive often failed, stranding its crew and passengers, who then – if they were lucky – managed to crawl to a nearby habitable world and set up a ‘lost colony’. The drive was powered by a "micropile", but the malfunction would drain that, requiring the drive to be powered by an alternate energy source (he used diesel generators with atmosphere scrubbers). This only powered the drive for a short time at a slow speed - enough to find the closest marginally-habitable planet. This gave Chandler a reason for plenty of "lost world" human colonies.*

Erikson Drive – only works on the outer edges of our galaxy where the fabric of space and time run thin. The Erikson Drive is hokey, involving an extra kick with a reaction drive when a ship is already at .9999 c. But it performs the trick of going FTL not by adding this extra push (a physical impossibility) but by pushing the drive and its ship into an alternate dimension.
This drive has the added virtue of ‘reversing its sign’ and allowing trade and relations with the beings that inhabit anti-matter worlds.



*

"Mphm," grunted Grimes again. He shot a dirty look at Maggie Lazenby as he heard her whispered "Keep it short!" He carefully lit his pipe. He said, "The majority of the so-called Lost Colonies date from the days of the Second Expansion, of the gaussjammers. The gaussjammers were interstellar ships that used the Ehrenhaft Drive. Cutting a long and involved story short, the Ehrenhaft generators produced a magnetic current—a current, not a field—and the ship in which they were mounted became, in effect, a huge magnetic particle, proceeding at a speed which could be regulated from a mere crawl to FTL along the 'tramlines,' the lines of magnetic force. This was all very well—but a severe magnetic storm could throw a gaussjammer light-years off course, very often into an unexplored and uncharted sector of the galaxy . . . ."

"FTL?" demanded Forsby in a pained voice. "FTL?"

"A matter of semantics," Grimes told him airily. "You know, and I know, that faster-than-light speeds are impossible. With our Mannschenn Drive, for example, we cheat—by going astern in time as we're going ahead in space. The gaussjammers cheated too—by coexisting with themselves all along the lines of magnetic force that they were on. The main thing was—it worked. Anyhow, visualize a gaussjammer after a magnetic storm has tangled the lines of force like so much spaghetti and drained the micro-pile of all energy. The captain doesn't know where he is. But he has got power for his main engines."

"You said that the micro-pile was dead."

"Sure. But those ships ran to emergency generators—diesel generators. They churned out the electricity to drive the Ehrenhaft generators. The ship's biochemist knew the techniques for producing diesel fuel from whatever was available—even though it meant that all hands would be on short rations. So, for as long as she could, the ship either tried to make her way back to some known sector or to find a planet capable of being settled . . . ."

In the Mannschenn Drive Room the complexity of spinning gyroscopes precessed, tumbled, quivered on the very edge of invisibility, pulling the ship and all her people with them down the dark dimensions, through the warped continuum, down and along the empty immensities of the rim of space.

.....

Mannschenn Drive unit precessed and tumbled, falling down and through the warped continuum, pulling the structure of the ship with them.

.....

The thin, high whine of the Mannschenn Drive Unit deepened as the spinning, precessing gyroscopes slowed to a halt, and as they did so there came the nauseating dizziness of temporal disorientation.

.....

Drive as the precessing gyroscopes slowed to a stop, experienced the inevitable sense of temporal disorientation.

.....

It was the governor, that comfortingly stable rotor at which he always looked after too long a time spent staring at the precessing gyroscopes.

.....

He could imagine those shining rotors starting to turn, spinning faster and faster, spinning, precessing at right angles to all the dimensions of normal space, tumbling through the dark infinities, dragging the ship and all aboard her with them as the temporal precession field built up.

 

[Grav_Moped]

Yep. I remembered the diesel-powered starship bit but not that they were associated with the gaussjammer drives -- it's been a long time since I read those books. Really ought to look them up again; excellent writing.

The time-machine drives seemed to be a nifty "cheat" to get FTL, with some useful story-drivng implications (in-flight boarding operations impossible unless you could synchronize the time-machine rate, malfunctions resulting in time travel, plus the distressing consequences of falling into the drive -- eww.)