Reply to thread

Message: <blockquote data-quote="Nobby-W" data-source="post: 8092785" data-attributes="member: 7017291">That's wrong to begin with.  The term doesn't make any representation about the technology used; you can do a burn with <a href="https://www2.l3t.com/edd/products/electric_propulsion.htm" target="_blank">ion thrusters, for example. </a> You're still pulling up straw man arguments and trying to put words in my mouth.  I've never stated any assumption of using chemical rockets.  A reaction drive is anything that generates thrust by accelerating reaction mass out the back in some way.Please don't argue semantics, and please don't pull in unstated assumptions.  Why would such a large expenditure of energy not be noticed?   If the tech exists to hide something, why shouldn't better sensor tech exist as well?  It's down to what you want to handwave; we're in the business of designing setting canon.  You can decide whether you want it to be possible or not.That is actually wrong.  Orbital mechanics doesn't work like that at all; objects don't just drop out of orbit.  You need just as much energy to move something into a lower orbit as higher.  3km/sec delta-V is 3km/sec delta-v no matter which way you want to apply the thrust.Still not stating your assumptions.  A solar sail isn't going to be small, and it isn't flat, so it reflects light over a more or less conical region.  The rock is still in orbit, so the aspect of the sail will of necessity change to keep the thrust - it will sweep the solar system like a lighthouse.  It's a very big handwave that something many kilometres across, curved and highly reflective would go unnoticed for years, especially in the case of a setting where this attack is known to be possible. There are programmes to monitor and keep track of asteroids today by doing regular sweeps of the sky with telescopes and automatically comparing the scans for changes; there's no inherent reason that similar programmes couldn't be implemented in your setting of choice.  Even a small asteroid changing course or suddenly disappearing is something we can detect with today's tech.  Netpune was discovered by measuring unexpected perturbations in the orbit of Uranus - in 1846.   At the very least, if such an attack was considered likely, one could establish a sensor network of satellites in a suitable stellar orbit to pick up the reflections of a solar sail.Plus,  You've still got to lug a major piece of engineering to your rock and deploy it without being noticed in the first place.  You've got to manufacture it without being noticed, and if the attack is known to be a possibility then universe+dog will have their spook services keep a weather eye out for signs of folks manufacturing such a big light sail.Again, this is wrong.  Weight is not the same thing as mass.  A 1kg object might weigh 1kg (9.8N to be specific) on the earth, but the same object has different weights in different gravity.  Diddling with gravity doesn't affect the mass or energy needed to accelerate an object.  You still need the same amount of thrust to accelerate it relative to its orbit.It's just he-said, she-said now.  If you're in the business of designing setting canon then you need to work out what you want to be possible in your setting and deal with the consequences.  If we don't want artificial dinosaur killers in our universe then it's straightforward to handwave them out of existence.  I don't need to carry your burden of proof to do that.  This argument was stale on the TML 20 years ago and these days its presence in the context of any given sci-fi 'verse is a sign that the designers haven't been thinking through their mcguffinite properly.</blockquote>

Verification