(SPOILERS) The reasons for the Archangel's return

Keith_w wrote:

Joat42 wrote:It's not that difficult, the OBS accelerates the rock first to ~1 km/s (or 1 mile/s). At that speed there will be very little drift and it can be aimed quite precisely for the intended effect even though it doesn't hit dead center.

If you want even more accuracy just stick fins on it, no need for thrusters. The other option is to increase its initial velocity which means that the area of effect will be bigger.

Why not put thrusters on them? This will allow trajectory adjustments while in motion. If it was good enough for Mike Holmes, it's good enough for Safehold!

Because you don't gain anything from it and only add a lot of complexity. If you need thrusters to hit something you are not aiming correctly from the beginning.

Keith_w wrote:

SWM wrote:I think you are misunderstanding how the KEW works. The KEW doesn't have rocket engines or anything like that. The kinetic energy of the weapon comes from falling. The gravitational potential energy is changed into kinetic energy. A weapon like that only works when dropped downward. It doesn't have rockets to fling it outward. There will be some kind of launcher to make the KEW go down instead of continue in orbit, but the launcher won't be very powerful. If you did launch the KEW outward, it would lose kinetic energy instead of gaining it. It would be useless as a weapon aimed outward.

I have been aware of how kinetic energy weapons work since I first read about Mike* guiding rocks on their trajectories to earth. They transfer gravitational energy to kinetic energy. There is nothing in that description that says that that the energy has to be accumulated on a direct line between the source and the destination. Missions to other solar system objects accumulate speed by passing near other solar objects such as planets or even the sun and transferring gravitational energy to themselves as velocity. This also slows down the visited object very slightly. The energy available at the termination of a voyage, whether one inch, one foot, one hundred miles or one billion miles is, if I recall correctly, one half mass times velocity, so yes, I do know how kinetic energy weapons work. They move fast, they hit hard.

Edited to add a comma
*second edit. Mike is a reference the supercomputer and practical joker in Robert Anson Heinlein's "The Moon is a Harsh Mistress". TANSTAFL gospodin.

Yes, I know how gravity assist works. I am a planetary scientist. My point is that the orbital KEW devices won't be able to launch a weapon out of Earth orbit. You won't be able to get the KEW to those other planets you want to get gravity assist from.

Even if you did manage to get one of these weapons launched toward another planet, the KEWs have rockets to help guide them or alter course. You would be firing blind. It would take years for the KEW to get out to the planet. How are you going to target an enemy ship after that? You are basically suggesting trying to kill someone by firing a bullet to ricochet off a distant wall and hit where you think your victim will be standing several years from now. That doesn't sound like a viable method of defending against the Gbaba.

n7axw wrote:The thing I struggle picturing in my own mind is how precisely they can be aimed. As Nynian tells it, the rakurai was accurate enough to score a direct hit on the SSK's first abbey. I suppose if it were just dropping a rock into the gravity well at exactly the right time, you could figure out mathematically exactly where and when the rock would have to be released. But the precision would have to be to so many significant figures that I've wondered if rocks have thrusters attached for course correction.

Don

It is not nearly as hard as you seem to think. It is a very straightforward mathematical calculation. Accounting for the non-spherical shape of the planet adds some complexity, but the calculation is still simple enough that the clunky computer aboard the Lunar Lander could have done it.

SWM wrote:

n7axw wrote:The thing I struggle picturing in my own mind is how precisely they can be aimed. As Nynian tells it, the rakurai was accurate enough to score a direct hit on the SSK's first abbey. I suppose if it were just dropping a rock into the gravity well at exactly the right time, you could figure out mathematically exactly where and when the rock would have to be released. But the precision would have to be to so many significant figures that I've wondered if rocks have thrusters attached for course correction.

Don

It is not nearly as hard as you seem to think. It is a very straightforward mathematical calculation. Accounting for the non-spherical shape of the planet adds some complexity, but the calculation is still simple enough that the clunky computer aboard the Lunar Lander could have done it.

Plus considering the shape of the rock would have to add complexity unless you are grinding it round before you use it. That wouldn't matter in space, but in the atmosphere, you have resistance and a deviation in course of a few fractions of an inch too far out would amount to a miss by tens of yards upon impact.

Don

n7axw wrote:Plus considering the shape of the rock would have to add complexity unless you are grinding it round before you use it. That wouldn't matter in space, but in the atmosphere, you have resistance and a deviation in course of a few fractions of an inch too far out would amount to a miss by tens of yards upon impact.

Don

With the energies involved, tens of yards doesn't really matter.

evilauthor wrote:What I don't get though is why, with all the clearly well thought out consideration here is why no one pointed out what seemed to me to be the most obvious flaw of an outward pointing OBS, where does it get the energy?

Considering that 99% of the time the OBS is just sitting there doing nothing but (presumably) passively watching the planet, it's energy requirements and that of its defenses isn't all that high.

So several possibilities:
1) It's solar powered. Or at least uses solar power to reduce any consumption of fuel required to power everything. That should be enough to reduce fuel consumption to zero and top off the batteries if all it's doing is watching the planet. It may even be enough if weapons fire is infrequent enough.

2) Its builders gave it plenty of fuel and it's not going to run out any time soon, especially if it's using solar power for most routine power consumption. It only needs to start up the fusion reactors or whatever when the batteries start getting low. If the batteries never get low, then the fusion reactors never start up and no fuel ever gets consumed.

3) In addition to self repair systems, its builders also put in some means of refueling itself. Which it only uses if fuel stocks get low.

4) None of the above. The OBS is actually low on power, fuel, ammo, and is about to die, although that's not evident from the outsider's perspective. It only has enough resources for one more Armageddon Reef style bombardment and then it's done, hence why the Key can only be used ONCE. The whole threat of repeated Rakurai strikes is a bluff.[/quote]

I'm sorry, I thought I was clear enough but perhaps I wasn't. When I am talking about energy issues, I am talking about the energy involved with the primary weapon, the KEW, not the defensive net that protects the platforms themselves. I cannot understand how anyone might think an OBS KEW system could be turned outwards and used as a defensive weapon because without the gravitational energy where does the needed energy to be a weapon come from in that scenario?

What caused me to get brainlocked on this point was a line from a post by Larry at Thu Mar 26, 2015 11:49 pm where he asks :" What if the OBS actually points, not inward but outward." The obvious interpretation of that question is that it is intended to be seen as possibly used to shoot away from the planet, but given this is a KEW system how can that work given the energy that makes KEWs work comes from gravitational acceleration?

I'd raised my question because in all the other very good arguments used to dispute the idea of the system in such a manner I never saw this particular point raised, and I wondered why given how obvious it seemed to me, that perhaps I had missed something in either textev, RFC notes, or worked out in long debates here that I hadn't read.

SWM wrote:I think the reason no one has discussed this is that no one has seriously suggested that the OBS is intended to fire upon incoming ships. The subject simply has not come up. You are right--the orbital kinetic weapons cannot be used on incoming ships or other ships in orbit. But no one has said that it could.

[/quote]


I do not entirely agree, as I said the question did come up, if not in detail, but it is clearly there in that sentence Larry wrote that I mentioned in the above reply. It was addressed by Kakai at Fri Mar 27, 2015 4:47 am, you yourself quoted the relevant sentence within the paragraph quote of Larry's at Fri Mar 27, 2015 10:50 am, and OrlandoNative did and continued the discussion at Fri Mar 27, 2015 2:41 pm. I cited those to make the point that while the initial idea was not apparently discussed seriously it was raised and repeatedly as a part of the following quotes yet no one pointed out the most basic refuting point to it, namely the nature of how KEWs work. That was why I had raised my question as I did, because I really was wondering if I had missed something important somewhere, because when my eyes read that sentence I literally went "Huh?!?!". That was what gave me the brainlock I mentioned and why I wondered no one pointed out why that was clearly incompatible with how KEWs work.


Thanks for the reply though, it is good to know I hadn't missed something important regarding that system, given its silent yet still looming Sword of Damocles role within the series.

BTW, I hope I managed the multiquote formatting properly, I'm not much practiced with it here at this site, forgive any errors please.

n7axw wrote:Plus considering the shape of the rock would have to add complexity unless you are grinding it round before you use it. That wouldn't matter in space, but in the atmosphere, you have resistance and a deviation in course of a few fractions of an inch too far out would amount to a miss by tens of yards upon impact.

Don

The weapon is almost certainly not a mere rock. It is probably a shaped dense metallic projectile. With the tech the Federation had, and the amount of time available, it would be silly to use an unshaped rock when you can get far greater accuracy and several times as much energy from a metallic projectile.

SWM wrote:

OrlandoNative wrote:On the subject of the Return, there really aren't all that many logical options. Either they're on Safehold, somewhere, or not. However, if they are not using some sort of stasis, which the only available noted form is the cryonic suspension, then they'd almost have to be on some craft moving at relativistic velocities in order to make up the "time difference". That poses a couple of problems. (1) An object like that wouldn't likely be considered "natural" if detected, so it would stand out like a sore thumb to any Ghaba scouts. (2) It would have to be screened in some way, since even hitting *dust* at relativistic velocities would create havoc with any possible "battle steel" hull.

If they are on Safehold, where is the most logical place? They would want somewhere where they are not likely to be found in 1000 years. That could only mean somewhere people wouldn't go; or, if they did, wouldn't dig or build at themselves. The only real place for that is either under the Temple, or possibly perhaps some sort of undersea habitat, though I doubt anyone in stasis would really consider the latter. Too much could go wrong.

Here is a somewhat longer list of possible mechanisms for The Return:
cryogenics
PICA
virtual reality avatar
AI
relativistic time dilation
a purely recorded message (a la Hari Seldon in the Foundation trilogy)
Imposters--a secret cabal passing down the knowledge across generations, with orders (which they may not even have read yet) to present themselves as Archangels at some future time

As for an alternative location for where they would be coming from, how about the Hamilcar? All we know about the fate of the Hamilcar is that it still existed at the end of the War of the Fallen, and it is not visible in orbit now. It could be hidden elsewhere in the Safehold star system. The Hamilcar is as logical a place to keep the Archangels safe as the Temple.

Now, I'm not saying that any of these alternatives are more likely than your assumption of cryogenics under the Temple. All I'm saying is that you are focusing too much on that one possibility, based on a mere assumption. You stated that the archangels were in cryogenic suspension and that they were under the temple, as if this was established fact. You need to keep other possibilities open.

Actually, I listed *several* possibilities. You even mentioned them in the beginning. Cryo units under the Temple was only one, and, I noted, not the best - given the known limitations of the technology.

That said, lets be a bit logical about this. The *entire* reason for Project Ark was to *hide* from the Ghaba, or, for that matter, from *any* advanced, star faring race that might be able to detect the human colony that the Ghaba might later encounter.

Given that, additionally hiding Archangels for a Return 1000 years later isn't likely to utilize *anything* that might look "unnatural" to any possible scouting party combing "local space" for any trace of sentient beings. That means no spaceships, no bases on moons, nothing moving at velocities much above a relatively small fraction of 'c'. And certainly nothing giving off non-random electronic, magnetic, or gravitic signatures.

Even the bombardment platform is an anomaly. Which is why I suggested that the staff that remained *after* Commodore Pei's nuclear revenge might not have known how, or had the remaining capability to, destroy it. That's certainly more reasonable than leaving it in orbit to possibly attract the notice of a Ghaba scout. It's not like orbital bombardment platforms are naturally occurring phenomena, after all

That doesn't suggest that those remaining Arch or minor angels didn't have *some* remaining technology. But it was probably construction and terraforming related, since that was still ongoing at the time. Space capable units were more likely to have been based at headquarters, and gone up in the blast

Thus, as far as where any Return might come from, that logically leaves somewhere "on planet". If so, the least likely to be disturbed place is under the Temple, since that's considered "Holy Ground". It's not like anyone is going to (or could) rebuild or add on to it. True, it could mean the return is then an avatar, a AI, a PICA, or a holovision, but whatever it is it makes sense for it to be in that location more than any others.

SWM wrote:

n7axw wrote:Plus considering the shape of the rock would have to add complexity unless you are grinding it round before you use it. That wouldn't matter in space, but in the atmosphere, you have resistance and a deviation in course of a few fractions of an inch too far out would amount to a miss by tens of yards upon impact.

Don

The weapon is almost certainly not a mere rock. It is probably a shaped dense metallic projectile. With the tech the Federation had, and the amount of time available, it would be silly to use an unshaped rock when you can get far greater accuracy and several times as much energy from a metallic projectile.

Mmm... That was more or less my thought. But would that mean that they would fetch small asteroids and render them down and reconstitute them until they had the wanted end product for reloading? If so the complexity of the OBS goes up by several orders. The more complex, the more likely something breaks down over time.

Don

Joat42 wrote:

n7axw wrote:Plus considering the shape of the rock would have to add complexity unless you are grinding it round before you use it. That wouldn't matter in space, but in the atmosphere, you have resistance and a deviation in course of a few fractions of an inch too far out would amount to a miss by tens of yards upon impact.

Don

With the energies involved, tens of yards doesn't really matter.

This does make sense, but what are the limits? You are not going to want to pulverize half a continent to knock out an abbey. All of this implies some fairly precise control with not only precision, but amount of energy neded to do the job.

Don