Ringworld Engineers Question [Spoilers]

[Bick]

Ok, here's one for the Known Space experts out there.

I just read Ringworld Engineers, and I thought I understood it (it helps if you've read Protector, as well as Ringworld), but there is one element I cannot fathom:

[SPOILER FOLLOWS]
If the Ringworld's meteor defense system, which they use to increase the energy to the Bussard ram jets on the ring to move it back into position, comes from the sun itself (sun-flares), produced by magnetic flux generated in the ring, then how can it be used to hit meteors or fast-moving spaceships? A solar flare (or even a solar flare-generated laser from the shadow squares), would take several minutes to reach the ring, as it would limited by c. Niven seems to suggest that it strikes more or less instantaneously (else how could be of any use). Clearly, I cannot have understood it as well as I thought, as this is such a glaring problem? Any ideas?

 

[Bick]

Bump... 189 views and no ideas! I've clearly set quite a poser...

 

[avalonimperium]

Well ill take the plunge. Im guessing here that since Niven only allows plus c movement in hyperspace then a solar flare pumped laser works at c and even if a ship had the outsider reactionless drive their reclexes cannot beat something moving at c therefore they cannot dodge incoming fire so no mater how fast their ship is moving. Dont forget that the distance from the star to the ring is approx one AU the same distance as earth to sol so even vessels or asteroids with high velocity are going to take a while to travel any great distance say earth orbit to venus orbit so plenty of time for laser to swat them. As to Niven implying its instant what page isxthat on ill have to check. I seem to recall that he indicates some passage of time. Anyway hope this helps or have I shown myself to be a great big eally through not understanding anything.

 

[chrispenycate]

Oops, missed this one.

It's worse than that. The main part of the protection is a directed solar flare – particles, not photons. I doubt if it would exceed .9c (aiming a blowtorch onto inhabited territory). And it would be emitting electro-magnetic energy (at the very least in the infra red, probably in the visible spectrum). So, whatever it was aimed at would get advance warning, and could dodge.

But comets and asteroids and such junk wouldn't dodge and, unless they were coming directly in the plane of the disc (in which case powee! Fist of God.) a Pak protector would be able to project their trajectory accurately enough (even without computers) to take care of the problem.

Which leaves ships. Ships that don't really want to damage the ringworld, just depopulate it for their own populations (highest probability, competing protectors).

But, by the time it gets to a couple of AU from the star, however well collimated that beam started out electrostatic forces have spread it to a couple of square kilometres. Ships big enough to do any real damage are not going to be able to make sharp turns, and, as far as we can tell, Pak ships can't just slip into hyperspace, so they'll need shielding.

Can we shield them from a considerable mass of encroaching plasma? Yes, either by physical barriers; a kilometre thickness of water ice would probably suffice, even if it did tend to cut the acceleration, a ramfield, although this would involve the ship, or at least the generator structure accelerating toward the star, rather than slowing down, which is really what you want to do – but you could keep the ship in its shadow, and write off the superconducting mesh. Or a slaver stasis field, assuming the Pak have discovered it. There, of course the problem is turning it off, as anything outside it tends to be vaporised, and no time passes inside.

If I can come up with three, like that, there are doubtless others. But the main point is that a Pak protector will always improvise. Puppeteers are planners, strategists, Pak are tacticians, using their immense powers of calculation to think on their feet, create solutions to specific problems, not prepare for general situations.

They'll make it.

 

[Bick]

Nice thoughtful replies, guys. I appreciate your comment about Pak tactician abilities, Chris. I think the system must depend on the trajectory of any asteroid or ship being predictable for the 5-10 minutes it would take for the solar flare to reach the moving body. If you are in a small vessel travelling at speed across the surface of the ring world you would only need to change vector randomly every 30 seconds or so to bamboozle the system, I'd have thought.

 

[chrispenycate]

You really wouldn't want to use it on anything that had attained the surface of the discworld; that would be like using a tactical nuclear weapon against a speeder on a freeway. Certainly, he would get no more points on his license (unless he was a Hollywood hero), but a number of other drivers, nearby towns and people wanting to use the road in the future would be severely miffed. Worse, so would insurance companies.

Obviously, there could be circumstances – say where the driver was carrying stocks of a newly developed disease, wind-borne and 100% lethal to all mammalian life forms, and should the vehicle crash rather than burn there's a strong risk of it escaping – where the atomic sterilisation was the optimum choice, and a protector would calculate like this, but mostly less extreme measures would suffice – a squadron of rocket-armed fighter jets would do less collateral damage, even if they'd be a trifle slower than an orbit-launched nuke.

The paths of celestial objects tend to be predictable months or even years in advance, and even space craft, if you know their original trajectory and where they intend to turn up (and at what relative velocity) don't have that many choices.

You could fly through the system at two thirds of the speed of light (having previously convinced the local protector you were dropping in for tea) releasing packages of that aforementioned virus, some of which are bound to hit the discworld's inner surface and spread; but the discworld is big. It would take hundreds of thousands of years to infect the entire surface, in which time the protector is bound to find a solution, even if it's only to plasma sterilise infected regions. More likely to breed up a counter organism, or confer immunity on chosen inhabitants; they're bright.

 

[TJP]

Just a quick reply here, but I just read through the whole series this last week. There were a couple of places where this was laid out but if you need proof, I got the books from the library so I can't cite it unfortunately. Anyway:
The defense creates an actual light based beam. I'm not sure the workings, but at one point Niven even goes on to say that it excites the atmosphere and releases light where the otherwise invisible beam passes through said atmosphere.
When they used the defense to fuel the ramjets, they didn't actually generate the beam so much as pull out the solar flare. That's why they couldn't target any specific part precisely. Hindmost pulled plasma from the star in the direction of the ramjets in giant solar flares.

If this was a matter based attack, rather than energy, it would travel much slower than the speed of light. Several times he sited the time it would take for the beam to reach it's mark and I remember checking the math and seeing that it was indeed traveling at the speed of light. Now I checked on the fly and in my head so I suppose I could be mistaken (I admit math isn't my strong suit so I encourage you to check my work), but the nature of this tool was pretty clear to me from all the descriptions of it in use. It's a manipulation of plasma pulled into the corona that somehow effectively creates a beam of high energy rf. It takes time to set up the fields and manipulate the plasma, but once the beam is generated, it travels at the speed of light.

Or at least that's what I took from the books.

 

[Bick]

Thanks TJP - I'm very willing to accept your maths and I accept the speed of c for the beams. I guess that, if it travels at c, then you get no warning its coming and therefore cannot evade voluntarily. If you happened to change direction by chance in the 8 minutes it takes for the beam to get to you, I guess it would miss, but several beams may be sent out at once for dangerous targets I suppose.

Welcome to Chrons, by the way - this sort of daft debate of made up stuff is what we're about, so if you have more for us, please share!