Problem of math

[Slife]

So, riffing on the pseudoscience - what happens if you introduce heavier elements than hydrogen to the ramjet? Say, iron?

Iron is unique in that you lose energy when you fuse it or fiss it. Anything higher than iron takes energy to combine, and anything lower than iron takes energy to split.

Basically, you'd lose some power, and you might get something clogged up.

 

[Pbartender]

So, riffing on the pseudoscience - what happens if you introduce heavier elements than hydrogen to the ramjet? Say, iron?

The same thing that happens to iron in a main sequence star... not much.

The iron will get very, very hot, and likely be ionized. Then it gets spit out the back with all the other exhaust. Anything on the hydrogen side of iron will either get fused or spit out, depending on how hot the fusion reaction is. Anything on the heavy side of iron will likely be spit out, but there's an outside chance it could split in a fission reaction.

In other words, the farther you get away from hydrogen, the less efficient the fuel mix will be... But go watch Back to the Future 2 again. A good sci-fi fusion reactor can run on anything.

 

[Jim Hague]

The same thing that happens to iron in a main sequence star... not much.

The iron will get very, very hot, and likely be ionized. Then it gets spit out the back with all the other exhaust. Anything on the hydrogen side of iron will either get fused or spit out, depending on how hot the fusion reaction is. Anything on the heavy side of iron will likely be spit out, but there's an outside chance it could split in a fission reaction.

In other words, the farther you get away from hydrogen, the less efficient the fuel mix will be... But go watch Back to the Future 2 again. A good sci-fi fusion reactor can run on anything.

Curses! And here I was hoping for something along the lines of a sandcaster, purposed for disabling the SHARC Drive.

 

[DJCupboard]

Stepping outside the bounds even of pseudoscience and moving straight into technobable, if you wanted a ramjet jammer, just say the "ionized/plasma exhaust," if fed back into the ramjet scooper is alligned in such a manner that that it overloads the Rhindtfeld-Turgen Intake Manifold causing at best a failed reaction that leads to a stall and at worst something quite catastophic that the service desk at R/T Intergalactic isn't authorized to comment on.

Then you could have a black market capitalizing on the sale of "exhaust pellets," pirates who specialize on the collection of the exhaust, and terrorists who utilize the pellets for political or monetary purposes.

The longer your individual trip takes (i.e. the farther out you have to go) the more likely you are to attract these terrorsists at some point, as a matter of probability, making loooong distance travel quite dangerous.

DJC

edited for clarity.

 

[Umbran]

In other words, the farther you get away from hydrogen, the less efficient the fuel mix will be... But go watch Back to the Future 2 again. A good sci-fi fusion reactor can run on anything.

I think there's far more subtlty to the possibilities than that.

A good real-world fusion reactor won't eat just anything. In the real world, details of temperature, density, and the presence of trace amounts of other materials (to act like nuclear catalysts) matter to the reaction. Just because a given setup will fuse hydrogen into helium, does not mean it'll also fuse lithium into something else. Even in a standard star, "hydrogen to helium" isn't the whole story. Hydrogen has dueterium and tritium as isotopes, and they don't all have the same reaction pathway to helium.

And we are talking about an engine, not a star - engines are finely tuned. And while both gasoline and sugar will burn, you only put one of them into your car, right? What you throw into it will at least change the efficiency of the result

So, what happens if you throw iron into the works? Well, to a degree, this is fantasy, and what you want to happen matters most. In the real world, it is mostly a question of engineering. If you throw too much of anything the system isn't designed to fuse into the works, it'll choke on it. And the results of choking may not be good for your engine.

The classic Bussard ramjet is only designed to pick up gases as fuel. Solid chunks of matter won't be deflected enough by the magnetic funnel to make it to the intake. And if you were to toss, say, a Volkswagon directly into the intake, I believe something breaking or going *boom!* would be in order.

 

[Pbartender]

I think there's far more subtlty to the possibilities than that.

Oh, there probably is... I just didn't think we were interested in them for this particular discussion.

A good real-world fusion reactor won't eat just anything.

That's why I specified "a good sci-fi fusion reactor"...

And we are talking about an engine, not a star - engines are finely tuned. And while both gasoline and sugar will burn, you only put one of them into your car, right? What you throw into it will at least change the efficiency of the result

Which is what I was saying above, with the simple stimpulation that this particular brand of fusion engine could be designed to be a bit more tolerant than you r typical engine. After all, with a fusion ramjet, it'd be very difficult to be discerning about what kind of fuel you toss in... You have to take whatever you're traveling through.

So, what happens if you throw iron into the works? Well, to a degree, this is fantasy, and what you want to happen matters most. In the real world, it is mostly a question of engineering. If you throw too much of anything the system isn't designed to fuse into the works, it'll choke on it. And the results of choking may not be good for your engine.

Right... I was thinking more along the lines of tiny dust particles or stray solitary molecules. Those aren't likely to harm much of anything. You'd get a brief fraction of a percent dip in your efficency, and then it goes away.

The classic Bussard ramjet is only designed to pick up gases as fuel.

Aha! That's the name I was trying to remember... I knew I picked up the idea from a Niven or Heinlein novel, but I couldn't remember which ones or what they called it. Thanks.

Solid chunks of matter won't be deflected enough by the magnetic funnel to make it to the intake. And if you were to toss, say, a Volkswagon directly into the intake, I believe something breaking or going *boom!* would be in order.

Of course... A collision's still a collision.

This situation would be roughly the equivalent of sucking a Canada Goose into the intake of a jet engine... rather than sucking up a bit of Canada Goose dander.

 

[Jim Hague]

Ok, so a sandcaster type weapon shooting clouds of ferrous oxide is out...what about ionized particles? Again, my science is about what you'd expect from public schooling and bolstered by a bit of college and reading a lot...but could you use charged particles to possibly overload the fusion reactor's magnetic 'pinch', or disrupt it?

 

[Umbran]

Ok, so a sandcaster type weapon shooting clouds of ferrous oxide is out...what about ionized particles?

The sandcaster might not be out - if you have enough sand. It'd be better as a focused weapon than a minelayer in space.

In general, there's already lots of charged stuff out in space near a star, like the solar wind, so if the thing is goign to function at all, it can't be particularly vulnerable.

but could you use charged particles to possibly overload the fusion reactor's magnetic 'pinch', or disrupt it?

You want to disrupt the magnetics of the thing, use more magnetics - a simple EMP weapon will do the trick.

 

[Jim Hague]

The sandcaster might not be out - if you have enough sand. It'd be better as a focused weapon than a minelayer in space.

In general, there's already lots of charged stuff out in space near a star, like the solar wind, so if the thing is goign to function at all, it can't be particularly vulnerable.

You want to disrupt the magnetics of the thing, use more magnetics - a simple EMP weapon will do the trick.

Hah, so we're back to the good ol' EMP. I swear, it's almost as useful as nanotech...

 

[helium3]

Why don't you play the campaign out on a ring world? They're so large that you can have as many different "planets" as you like, which are really just different regions on the same immense structure. Then you can just wave your hands and say it's possible to fly from one side of the ring to the other in a single day, which still won't be fast enough to make interstellar travel possible. Besides, ringworlds are cool.