(semi)hard sci-fi propulsion

[Slartibartfast]

Ok, I think we all know how propulsion in space works: Reaction mass is ejected towards the opposite direction you want to go (duh). Currently, we use rocket fuel, which is expelled thanks to its own energy (you burn the fuel and it just shoots thru the thrusters).

We know that in soft Sci-Fi a lot of "reactionless" thrusters are used. These require no reaction mass or such a small amount it could just as well be unlimited. They directly convert energy to thrust with unknown methods.

I suppose that the amount of reaction mass expelled, along with its velocity determine the amount of thrust (so if I can just expel it faster instead of expelling more, I should be able to go faster).

Is there a point where we could almost turn energy directly into thrust, by using electric energy to somehow shoot our reaction mass (ex: like a gauss cannon/mass driver) much faster than rocket fuel, so that we use a really really tiny amount of reaction mass and lots of energy, from a nuclear reactor or such? And that the more we increase the energy output, the higher velocities we can achieve?

What do you think?

[Knife]

If I follow you right, then an Ion engine even though right now we can't make one with the acceleration to be practical for manned flight.

[NecronLord]

Ok, I think we all know how propulsion in space works: Reaction mass is ejected towards the opposite direction you want to go (duh). Currently, we use rocket fuel, which is expelled thanks to its own energy (you burn the fuel and it just shoots thru the thrusters).

We know that in soft Sci-Fi a lot of "reactionless" thrusters are used. These require no reaction mass or such a small amount it could just as well be unlimited. They directly convert energy to thrust with unknown methods.

I suppose that the amount of reaction mass expelled, along with its velocity determine the amount of thrust (so if I can just expel it faster instead of expelling more, I should be able to go faster).

Is there a point where we could almost turn energy directly into thrust, by using electric energy to somehow shoot our reaction mass (ex: like a gauss cannon/mass driver) much faster than rocket fuel, so that we use a really really tiny amount of reaction mass and lots of energy, from a nuclear reactor or such? And that the more we increase the energy output, the higher velocities we can achieve?

What do you think?

Your talking about "space drives" there are numerous hypothetical ways of doing it, they are on the Nasa website

[Slartibartfast]

Ok thanks I'll look them up.

[Slartibartfast]

WTF are these 'reactionless space drives' and do they make any sense??

http://www.geocities.com/CapeCanaveral/Hall/1358/

[Vejut]

Dude...thats not NASA, thats some guys personal site...

[Darth Wong]

Reactionless drives don't make sense from a "Conservation of Momentum" perspective.

[greenmm]

Yep, the electrical drives are just another name for a type of ion drive system.

From the articles I've seen, though, NASA's apparantly having 2 problems:

1. Size and power of the drive units. Despite their efficiency (10x that of chemical rockets), and their long range (Deep Space 1 probe apparantly had its thrusters burning for over a year continuously), the actual thrust output of the current units is very low -- Deep Space 1 took a full year to reach 300,000 mph (about 4.474E-04 c). That works out to about 4E-04 g's of acceleration, and a powered flight range one-way of about 14.15 AU's. That could be due, however, to either the size of the thruster or the speed they eject the ions at (currently 60,000 mph, or about 8.947E-05 c). If they could boost the exit speed of the ions by a factor of even just 100, that would mean a probe could reach 300,000 mph in about 88 hours (3.6525 days); in 1 year of constant thrust, it would reach 30 million mph (about 0.04474 c), fast enough to travel from Earth to the Sun in a little over 3 hours, albeit still a little slow for interstellar travel.

2. Degradation of the thrust chamber. The negatively charged open plate which allows the ions to exit and produce thrust apparantly gets very degraded very quickly. They likened it to sandblasting a wall. Obviously, the more resistant the plate is to degradation, the longer you can maintain thrust, and the more velocity you can build up.

I doubt they'll solve it anytime soon -- maybe within our lifetimes, but I wouldn't count on it. However, the fact that they've gone from theorizing about ion drives to actually building small-scale working drives shows definite progress.

[greenmm]

Reactionless drives don't make sense from a "Conservation of Momentum" perspective.

Nope, they don't. Even a gravitic-based system is going to either push against your point of origin or pull against your point of destination. Sure, planets have extremely large masses, and a force that can accelerate a 100 megaton ship at 500g's will barely shift a 6 trillion teraton planet (it's what, 8.36E-15g's?). But, get a few thousand ships here and there pushing over a few decades or so, and we could be talking about some slight orbital shifts here.

I guess that's why we need things like warp drive and hyperspace in sci-fi for interstellar travel, since they can fudge around conservation of momentum a bit (albeit hyperspace more so than warp drive...)

[Typhonis 1]

hmm the only practicl large mass driv we have is an Orion engin and that would be best used in space *L* whos going to notice the extra radiation?

[Typhonis 1]

Or you work against the momentum of the universe since its already expanding outwards

[Knife]

One option you can look at even though I'm sure it won't fit your topic exactly is the various types of solar sails. The M2P2 system has huge potential.

[NecronLord]

WTF are these 'reactionless space drives' and do they make any sense??

http://www.geocities.com/CapeCanaveral/Hall/1358/

no he's an idiot.

I meant these.

here.

http://www.grc.nasa.gov/WWW/PAO/html/wa ... htm#millis

They work by creating a scalar difference inf the gravitational potential of the surrounding space. Instead of crawling along the sheet it creates the equivalent of a traverse wave anchored to the ship. Somewhat like surfing. Another analogy would be creating a pressure gradient in a fluid to force an object forward.

[HRogge]

Reactionless drives don't make sense from a "Conservation of Momentum" perspective.

What's about a "photon" drive... on that use light to produce thrust ?

[SirNitram]

WTF are these 'reactionless space drives' and do they make any sense??

http://www.geocities.com/CapeCanaveral/Hall/1358/

no he's an idiot.

I meant these.

here.

http://www.grc.nasa.gov/WWW/PAO/html/wa ... htm#millis

They work by creating a scalar difference inf the gravitational potential of the surrounding space. Instead of crawling along the sheet it creates the equivalent of a traverse wave anchored to the ship. Somewhat like surfing. Another analogy would be creating a pressure gradient in a fluid to force an object forward.

These seem about as likely as the Resetter, partly because they seem to rely on the same idea, altering some sort of basic property of reality.

[NecronLord]

WTF are these 'reactionless space drives' and do they make any sense??

http://www.geocities.com/CapeCanaveral/Hall/1358/

no he's an idiot.

I meant these.

here.

http://www.grc.nasa.gov/WWW/PAO/html/wa ... htm#millis

They work by creating a scalar difference inf the gravitational potential of the surrounding space. Instead of crawling along the sheet it creates the equivalent of a traverse wave anchored to the ship. Somewhat like surfing. Another analogy would be creating a pressure gradient in a fluid to force an object forward.

These seem about as likely as the Resetter, partly because they seem to rely on the same idea, altering some sort of basic property of reality.

Humm it's more localised, and it's only really the gravitational gradient. I make extensive use of a combination of three of them.

and photondrives as backups

http://www.angelfire.com/scifi2/iimperi ... ravel.html

Please note, I have only spent under an hour doing that site.

[greenmm]

Not to burst your bubble... but did you even notice that those were hypothetical drive systems? Or that it was pointed on the very same page that they'd have to even develop working theories to create the science that would allow such a drive to be designed? Heck, for that one drive system, they don't even know for sure if "negative energy" exists.
Not to mention that there is no theory, let alone science or technology, that allows us to even generate artificial gravity in space, so expecting us to be able to change the gravitational properties of local spacetime are sheer fantasy.

The closest thing we have to a working interplanetary/interstellar drive system right now is the electric/ion drive systems that NASA has been testing, and even that isn't ready for manned space travel.

[NecronLord]

Not to burst your bubble... but did you even notice that those were hypothetical drive systems? Or that it was pointed on the very same page that they'd have to even develop working theories to create the science that would allow such a drive to be designed? Heck, for that one drive system, they don't even know for sure if "negative energy" exists.
Not to mention that there is no theory, let alone science or technology, that allows us to even generate artificial gravity in space, so expecting us to be able to change the gravitational properties of local spacetime are sheer fantasy.

The closest thing we have to a working interplanetary/interstellar drive system right now is the electric/ion drive systems that NASA has been testing, and even that isn't ready for manned space travel.

Sorry to burst your bubble but did you notice the (semi) before hard science? Or the fact that this is a SCI FI forum? what are you? stupid? of course they're fucking hypothetical, if it were in SLM then it that would be an issue. This is Other sci-fi. idiot.

[Darth Wong]

I guess the point is that you might as well just call them "magic vroom-vroom technology" and be done with it, for all the realism they have. The worst thing sci-fi writers can do is explain exactly how everything works.

[NecronLord]

humm a mechanism without an implementaton. What do you want? schematics?

It should be noted that the nutroniom stargate does work in theory, puty it is about an au in diameter.

[SirNitram]

What's wrong with ion drives? I like them. And the backwash from a sufficiently large ship is a weapon in and of itself.

Necron, if you want something realistic, don't look to those 'hypothetical' systems. They are, as I said, as likely as the Resetter, because they are it, applied in another manner.

[Slartibartfast]

hmm the only practicl large mass driv we have is an Orion engin and that would be best used in space *L* whos going to notice the extra radiation?

That's not a mass drive. You don't use the force exerted by launching the bomb, you use the force of the explosion to propel you forward.

[Slartibartfast]

Reactionless drives don't make sense from a "Conservation of Momentum" perspective.

Yeah but what were these guys smoking when they made their blueprints for gyroscopic engines and uncontrolled spin and whatever? I mean these pieces of crap are even patented...

[NecronLord]

What's wrong with ion drives? I like them. And the backwash from a sufficiently large ship is a weapon in and of itself.

Necron, if you want something realistic, don't look to those 'hypothetical' systems. They are, as I said, as likely as the Resetter, because they are it, applied in another manner.

I am not after anything particularly realistic, hell this ain't even my thread. Internal self consistency and no flagrant breaches of known science does me fine. For explaining away FTL and other stuff i use "exotic science" i.e. working on different principles e.g. 'quantum mechancs' I also don't want technology like the resetter, because it makes everything far too mundane.

[kojikun]

Ahh "reactionless drives". Love them.

And while they obviously have to work by some unknown but reactionbased method, theyre wonderful things.

There are a few bits of research on "reactionless drives". http://jnaudin.free.fr is a site that works on numerous things (tho, some are quite bullshit filled). However, the so called "Lifters" are serious and NASA even has a patent on them.

The Army research lab has its eyes on the lifters as well.

I suspect, and rightly so, that the power put into them required to lift an object would be equal to or somewhat higher then that of an equally powerful helicopter engine. But even so, no moving parts and cheap construction is a benefit.