Re: FT Taskforce and Fleet Actions

On Aug 07, Randall L Joiner <rljoiner@mindspring.com> wrote:
> 
> I'm not sure I agree with this radiant energy inefficient drive /
> only way to drive a machine is to light stuff on fire crud.

     Not quite correct. What I'm saying is that I'm assuming a 
reaction drive (ie a drive that operates in accordance with Newton's 
3rd law of action / reaction -- in order to accelerate forward, you 
HAVE to toss something else back). Any other drive violates 
conservation of momentum, conservation of angular momentum, and 
conservation of energy. I prefer not to introduce that unless I have 
to.

> While I'll admit, solar sails aren't as useful out of system, or in
> bound, they are an example of a difference.

     They're also VERY easy to detect. How does a solar sail work? By 
reflecting sunlight. That means it's a) as big as you can make it, 
and b) as reflective as you can make it. This means that it's VERY 
easy to detect (as much so as a high-thrust reaction drive? maybe 
not, but still dead easy for any nation that can build telescopes 
with today's technology).

> However, assuming a fission/fusion drive (take your pick, either are
> likely to be dirty) and a ship headed IN bound, with the right
> shielding (Absolutely necessary to some extent just to protect the
> crew) why would there be _any_ emmisions heading towards the
> system?  Last I checked EM radiation doesn't bend around corners
> without help or special very narrow appatures (and I would not
> qualify an SDN's main engine cone to be a narrow appature).

     Because the drive plume itself emits EM radiation. A drive is 
efficient in direct proportion to the temperature of the reaction 
mass emmitted. This means that a high-temperature exhaust mass allows 
you to go farther for the same fuel. For high-thrust you want to 
reduce the temperature somewhat from the optimum, but you still want 
a VERY hot reaction mass to allow you to get up to any reasonable 
speed without needing far too much fuel.
     This means that your drive plume is also expanding after it 
leaves your ship (at a velocity roughly proportional to its 
temperature). This means that the drive plume will be emmitting 
strongly (for any realistic high-thrust reaction drive, the 
emmissions will be up in the x-ray regions probably) and those 
emmissions will be coming from a plume that's probably several light-
seconds in length (definitely in the tens of thousands of kilometers) 
and at least a few hundred km in diameter. If your ship will occlude 
THAT, the defenders are screwed whether they detect it or not.
     Also, of course, you have to slow down eventually. At the half 
way point, actually. Once you do, your drive plume is pointing right 
at the place you're heading for. Even easier to detect.
     I hate to bring in another list, but the rough consensus on 
sfconsim-l (backed up by an astronomer, also the person who wrote 
the "definitive sensor rules" for Traveller's FFS2(?), Bruce 
Macintosh), is that a high-thrust, high-efficiency reaction drive 
would be naked-eye visible out probably to the asteroid belt (even 
with the ship in the way) and detectable by telescope significantly 
beyond Pluto's orbit (for reference: today's telescopes would allow 
us to detect the drive plume from the Space Shuttle's main engines as 
far out as Pluto, and its manuvering thrusters as far out as the 
asteroid belt).

> How about magnetic shielding that already goes on?  Shielding that
> contains plasma's?  Ones that can theoretically hold point
>-anomalies (not sure that's the proper vocabulary for a tiny black
> hole)?

     I'm not sure what you mean by this.

> However, if you insist that it does, why not use compressed gas?
> Gaussian marble throwing?  Both throw stuff, but neither emits
> anything really detectable beyond a very small bit of space...

     Compressed gas: at what temperature? If it's at a high 
temperature, it'll BE a drive plume (thus detectable). If at low 
temperature, then you will need incredible tankage volumes to have 
ANY delta v (required by laws of physics, not technological 
assumptions, unless you can create this 'compressed gas' from a 
vacuum).
     Gaussian marbles are even less efficient. To get even a 
100km/sec velocity out of them (with a mass driver tube of a mere 1km 
in length), with 99.999% efficient mass drivers, they'll emerge from 
the barrel with a temperature in the thousands of degrees (inductive 
heating). The strain on your railgun will also be considerable. And 
the thrust produced not all that much. I can do the math on this one, 
if you'd like (the others are a bit advanced to try without my 
reference books).

> Basically, I'm trying to understand how a species who invents
> hyperdrive, gravity control, "shields," can't think of a way to
> hide thier emissions.  Specifically, a species that's shown just
> how creative it can be when waging war on itself...  One that
> already knows the military value of being sneaky.

     The big reason is these pesky little things called the laws of 
physics. Unfortunately, they place limits on how well you can do 
things.
     The other big reason is that space is an INCREDIBLY sensor-
friendly environment. If the detectors and the countermeasures are at 
the same technology level, or even close, you can't hide. Sensor 
ranges will vastly exceed weapons ranges unless you assume an 
incredible advance in stealth with no advance in sensors (and 
probably break a few laws of physics while you're at it).