Author Topic: Newtonian Stealth  (Read 4195 times)

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Offline byron

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Re: Newtonian Stealth
« Reply #30 on: October 14, 2011, 07:58:02 PM »
That is true though.  A computer run probe could do this run much better than a crewed ship. 

But then, after some examination, I was approaching the conclusion that anything not a commercial ship is probably better computer run.  Stealth or no. 
We're in complete agreement on this one, though the conclusion depends a lot on how much maintainence the systems require.

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Although your comment about in-system transit times probably won't apply to Newtonian Aurora.  You can always use normal engines to get incredibly high speeds and simply jump to your target system with whatever speed you need.  I would say it could even make relativistic missiles possible.  (although there is no point in Aurora since nukes are super-effective and the advantage of relativistic missiles is that you can't see where they are since you can't get the information in time.  Aurora having FTL sensors kinda kills that. 

Then again, you can get much higher yield per ton with relativistic rocks than nukes. 
EDIT: also that kilo-ton range "missiles" do more damage than a nuke.  It's like a small asteroid impact.)
This is true, but relativistic rocks are also really expensive.  After you go so fast (somewhere on the order of 2x exhaust velocity) kinetic energy starts to fall off.  Unless you have antimatter drives, those aren't in the cards.  The entire device was an answer in search of a solution.

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Radar absorption is already present in original Aurora though.  The original "cloaking device" only works on actives and makes the mounting ship appear much smaller.  Which could end up (with alot of RP investment) with kiloton range ships that need an anti-missile sensor to find.  (bigger resolution sensors don't even generate a contact)
-- Also to note that covering a system with anti-missile level of active sensor coverage is basically impossible

Hopefully, by the time they spot your "stealth" missile with high-res sensors on the planet, it'll be too late to try shooting it down.  Especially in Newtonian Aurora where missile flight times have increased alot. 
I am aware of that.  However, the best cloaking devices are (IIRC) about .5%.  A 10,000 ton ship would look like a 50 ton missile.  However, if your opponent is of a reasonably comparable techlevel (and if he isn't, why are you doing this?) he can detect you at several hundred million kilometers if he has a reasonably-sized sensor available.  And he then shoots you full of missiles.  Your vessel can't take a stand-up fight, so you lose.

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The point is to hope to conceal what your current position and velocity is so that even if they try looking, they'll have to scan large portions of the system before they can find you.  They know where you *were*, but can't tell how fast you were going. 
EDIT: if you were aiming at a planet, and they knew that, then they'ld have to scan a cone leading from your current position to plausible intersections with the orbit of the planet.  That's too much to scan even with Aurora active sensors.  At least if they need anti-missile resolution.  Anti-ship resolutions can scan out to Mars orbit pretty easily. 
That doesn't really work.  If they know about where you are, and approximately how fast you're going, they will be able to find you.  They know your current position just by seeing you, and Aurora ships are fast enough that they can get to your location before you can move, particularly when you're using a slow drive.

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Nope.  The 2.4GJ example railgun fires a 1ton shell with a momentum of 2 ton km/s.  It also looks like a low tech railgun. 

The way it looks like is that multiple small railguns would the way to go in designing a railgun-drive. 

They're still better than the drives we have in RL. 
You're confusing momentum and acceleration.  My number was 1 km/s/day, which is the acceleration the ship can put on.  Yours was a change in momentum.  To get from yours to mine, we have to divide by the mass of the launching ship, then multiply by the number per day.  Let's take a look at a ship of 10,000 tons (for a nice round number). 
2 tonkm/s / 10,0000 tons = 2e-4 km/s or .2 m/s per shot.
1000 m/s/day / .2 m/s/shot = 5000 shot/day or 3.47 shot/min
2.4 GJ/shot * 5000 shot/day = 12 TJ/day or 138.9 MW.
139 MW is the power of the drive.  While that's rather low, the problem is that, particularly if you're using a thermal reactor (which is pretty much a given, as all the reactors in Aurora are thermal) you have to get rid of waste heat.  For a thermal reactor, 416.7 MW of it.  That's a lot, and it assumes all other components are 100% efficient.  Which they won't be.
You now have to get rid of all that heat.  Heat sinks won't work for an significant length of time, which leaves you having to radiate quite a bit, which makes it you easy to detect.
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Offline jseah

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Re: Newtonian Stealth
« Reply #31 on: October 15, 2011, 03:27:51 AM »
This is true, but relativistic rocks are also really expensive.  After you go so fast (somewhere on the order of 2x exhaust velocity) kinetic energy starts to fall off.  Unless you have antimatter drives, those aren't in the cards.  The entire device was an answer in search of a solution.
Antimatter drives are in late game. 

But then it is late game. 

That doesn't really work.  If they know about where you are, and approximately how fast you're going, they will be able to find you.  They know your current position just by seeing you, and Aurora ships are fast enough that they can get to your location before you can move, particularly when you're using a slow drive.
They know your original velocity (say 10 kkm/s) and they know you vented weapons grade levels of heat on the order of GW at a certain point.  They don't know what happened to you after that since they can't see the mass driver packets. 

Which ends up with them needing to search a big cone in order to find you. 

Anti-missile sensors don't cover that much area.  In normal Aurora, I had a dedicated fleet scout at TL5 active sensors.  It had a max range of around 180mkm.  Which is about where I'd see my own cloaked design at TL4. 

To get from yours to mine, we have to divide by the mass of the launching ship, then multiply by the number per day. 
Here's a proposed *low tech* mass driver engine: (this looks like TL 2 or 3 to me from Steve's numbers)
2500 tons of engine for a 10 000ton ship.  25x 100 ton mass drivers firing 10 ton mass packets.  Fuel takes up 5000 tons of the ship.  This gives you 20 shots. 

MJ per ton = 12
Total energy per salvo = 12 x 25 x 100 = 30,000
Energy efficiency = 35%
Heat dissipation = 0.6 MJ/s
Railgun surface area = 78
Heat venting per second per railgun = 46.8
Firing rate = 25 seconds
Maximum thrust time = 500 seconds

Each packet contains 1200 MJ and 4.9 x 10^3 kg km/s momentum.  500 packets contains 2.4 x 10^9 kg km/s momentum. 
Final ship weight is 5000 tons.  Net delta-v is 490 km /s. 

So about 12x less efficient than similar tech drives. 
 

Offline UnLimiTeD

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Re: Newtonian Stealth
« Reply #32 on: October 15, 2011, 03:33:22 AM »
Is this still about normal aurora?
Given that Steve dislikes GFFP and purposefully doesn't allow player ships to perform ram actions, I don't think this would ever apply to Aurora.
And if your using Railguns to accelerate your ship, why can't you just turn them on the planet instead?
You'll even be able to get away afterwards.
 

Offline jseah

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Re: Newtonian Stealth
« Reply #33 on: October 15, 2011, 08:43:06 AM »
Its newtonian aurora. 

The GFFP problem is the same with planetary bombardment.  A relativistic ramming ship would make a planet uninhabitable in the same way as a salvo of nukes. 

A big ship would survive re-entry better than a bunch of small mass driver packets.  Even if they are 10 tons each. 
 

Offline Dutchling

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Re: Newtonian Stealth
« Reply #34 on: October 15, 2011, 09:09:21 AM »
What does gffp stand for?
 

Offline Hawkeye

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Re: Newtonian Stealth
« Reply #35 on: October 15, 2011, 10:05:27 AM »
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Offline byron

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Re: Newtonian Stealth
« Reply #36 on: October 15, 2011, 10:58:18 AM »
They know your original velocity (say 10 kkm/s) and they know you vented weapons grade levels of heat on the order of GW at a certain point.  They don't know what happened to you after that since they can't see the mass driver packets. 
That makes sense in isolation, and it might even work, but only until you fire again.  They have a couple of ships go to where you might be, and wait for the next shot.

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Which ends up with them needing to search a big cone in order to find you. 
Not as big as you'd think.  They have a decent localization, and they just need to fine-tune it.  Also, how do you deal with the fact that venting the heat will give away your position after you fire.  You could sink it, and vent last shots heat, but that's sort of rube goldberg.

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Here's a proposed *low tech* mass driver engine: (this looks like TL 2 or 3 to me from Steve's numbers)
2500 tons of engine for a 10 000ton ship.  25x 100 ton mass drivers firing 10 ton mass packets.  Fuel takes up 5000 tons of the ship.  This gives you 20 shots. 

MJ per ton = 12
Total energy per salvo = 12 x 25 x 100 = 30,000
Energy efficiency = 35%
Heat dissipation = 0.6 MJ/s
Railgun surface area = 78
Heat venting per second per railgun = 46.8
Firing rate = 25 seconds
Maximum thrust time = 500 seconds

Each packet contains 1200 MJ and 4.9 x 10^3 kg km/s momentum.  500 packets contains 2.4 x 10^9 kg km/s momentum. 
Final ship weight is 5000 tons.  Net delta-v is 490 km /s. 

So about 12x less efficient than similar tech drives. 
Actually, even less so.  That would only hold if you could fire them all at once.
4.9E3 kgkm/s / 10E3 kg = .49 km/s
4.9E3 * 500 = 2.45E6 kgkm/s
Each packet is traveling at .49 km/s, which makes the entire drive less efficient then using cold gas, which is equally stealthy.  The actual delta-V available is more on the order of .34 km/s.  No, that number is not an error.  Your final momentum is, as you seem to have given it in kg m/s.  However, I'll try that number as correct, too.
2.45E9 kgkm/s / 500 = 4.9E6 kgkm/s
4.9E6 kgkm/s / 10E3 kg = 490 km/s
In this case, the delta-V is a much more reasonable 340 km/s.  However, the energy for each packet is 1200 TJ.  I leave you to draw your own conclusions.
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Offline jseah

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Re: Newtonian Stealth
« Reply #37 on: October 15, 2011, 11:36:11 AM »
Oh, whoops.  I seem to have made a calculation error.  Must have dropped 3 zeros somewhere. 

Yeah, it's not feasible.  The railgun isn't powerful enough.  You need something on the order of 99.5% of your mass in "fuel". 

What is this "cold gas" you speak of?  Helium at 4 kelvin?  Don't think that's going to be useful other than an attitude thruster. 

We're going to need to have crew modules shed heat though (which was a suggestion I made about revamping sensors).  Perhaps take the ideal temperature of the race crewing the ship and calculate a thermal signature per crew member. 
And have thermal signatures drop off by the square of distance and require two things that can see it to triangulate a position. 

FTL thermal sensors... who the heck knows how they work anyway?


There is another idea however, building on the idea of completely computer run ships. 

Computer run ships might be able to get away with hiding their thermal signature (but not their drive signature) due to being able to tolerate very low running temperatures.  Could this be used to gain a "first strike" on fixed defences / populations / infrastructure?  (where fixed means anything in a predictable orbit)

Sort of like a steathy FTL-capable missile bus.  Expendable too. 
 

Offline byron

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Re: Newtonian Stealth
« Reply #38 on: October 15, 2011, 12:02:00 PM »
What is this "cold gas" you speak of?  Helium at 4 kelvin?  Don't think that's going to be useful other than an attitude thruster. 
No, it's generally something (helium, nitrogen, whatever) at about room temperature.  It is mostly used for attitude thrusters due to low mass and simplicity, as well as low Ve.  However, it is also the only system I know of that has undetectable exhaust.

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We're going to need to have crew modules shed heat though (which was a suggestion I made about revamping sensors).  Perhaps take the ideal temperature of the race crewing the ship and calculate a thermal signature per crew member. 
And have thermal signatures drop off by the square of distance and require two things that can see it to triangulate a position. 

FTL thermal sensors... who the heck knows how they work anyway?


There is another idea however, building on the idea of completely computer run ships. 

Computer run ships might be able to get away with hiding their thermal signature (but not their drive signature) due to being able to tolerate very low running temperatures.  Could this be used to gain a "first strike" on fixed defences / populations / infrastructure?  (where fixed means anything in a predictable orbit)

Sort of like a steathy FTL-capable missile bus.  Expendable too. 
That's pretty much my conclusion.  One caveat, though.  Computers don't work that much colder than humans.  They do, however, require a much smaller amount of heat, which means that they have a low, but not zero, thermal signature.  (A base thermal of one should work fine.  It's not completely invisible, but is is very difficult to see.)
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Offline jseah

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Re: Newtonian Stealth
« Reply #39 on: October 15, 2011, 12:18:10 PM »
Can't you build circuits that use little energy?  Most of the circuits can be superconducting, only the logical junctions need to have any form of resistance. 

The ultimate goal of course is to run a ship at ~2.7 kelvin, which has zero thermal signature.  (temperature equals CMB means you look like blank space)  Although something running at around liquid helium temperatures would hard enough to spot. 
 

Offline UnLimiTeD

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Re: Newtonian Stealth
« Reply #40 on: October 15, 2011, 01:44:49 PM »
A Graphene Chip should be working at a 100 K...  Sure, we can't yet make computers out of that stuff, but we're getting closer every day.
Theres also Insulations available that should be able to keep a Thermal difference of 250K for several Weeks.

What I've found, though, is that Light from a nearby star will already heat up your ship, not like an Engine, but certainly enough that you're not background anymore. We can expect there to be a star in most systems.
 

Offline byron

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Re: Newtonian Stealth
« Reply #41 on: October 15, 2011, 04:11:30 PM »
The star is the problem.  However, you really don't have to get to background, just enough to reduce the detection range.  The best use for stealth drones is probably recon, and if you can cool it to around 100K, then it's going to be detectable at only 12% of the range of the same vessel at 290K (all numbers are approximate).  Space is quite large, and scanning for stuff at 100K will take time, luck, close targets, or large targets.  Also, something on an intercept course for a planet is more likely to be detected because it will appear in the same region of the sky over multiple exposures.
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Offline wedgebert

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Re: Newtonian Stealth
« Reply #42 on: October 15, 2011, 04:51:34 PM »
A quick point about the mass driver engines.  The mass of the projectile is a few orders of mangitude larger than what Steve gives in his examples.  Steve talks about 400 ton rail guns that fire 2kg shells.  For a 10,000 ton ship, this is going to only impart an acceleration of a few mm/sec per railgun.
 

Offline Steve Walmsley

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Re: Newtonian Stealth
« Reply #43 on: October 18, 2011, 03:46:43 PM »
The made up materials are another thorn in my eye, I think we should reduce it to two or three kinds of handwavium and just abbreviate the rest, for example into "Metal", "Gas", "Rare Minerals" and "Fossil Fuels".
I suppose the correct assumption so far is that any possible Stealth is temporary, giving time to run away or attack first, but not a cloak that allows you to survey a system completely unseen for a month.
Because if we calculate with futuristic fantasy materials and possibilities, there's gotta be damn strong sensors on the other side.


Part of the reason for the unobtanium minerals is to encourage exploration. Otherwise, there would probably be enough of everything else in the Sol system and no need to explore. While the amount of the minerals on some Aurora planets may seem huge, a few million tons of most metals, rare minerals, fossil fuels, etc is a tiny fraction of what would be readily available in the Sol system.

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Offline byron

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Re: Newtonian Stealth
« Reply #44 on: October 18, 2011, 03:51:55 PM »
Part of the reason for the unobtanium minerals is to encourage exploration. Otherwise, there would probably be enough of everything else in the Sol system and no need to explore. While the amount of the minerals on some Aurora planets may seem huge, a few million tons of most metals, rare minerals, fossil fuels, etc is a tiny fraction of what would be readily available in the Sol system.

Steve
The solution to that is twofold:
1. There's only a very limited amount of handwavium in a given system.  This forces the exploration, while removing the "I have to move how many tons between systems?" issue.  A 10,000 ton ship takes 9,950 tons of metals and plastic and 50 tons of handwavium, but an average system only contains 500 tons of handwavium total.
2. Give planets a carrying capacity, and make it so that you have to explore and spread to thrive. 
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