I see we've abandoned reality in the rules again. First I see the post
about the HEPLAR drive violating the conservation of energy. Then I see
Loren's post regarding the 1 kw required for a 60 km range on a radio.
 
Let's hit the radio first. Loren stays that the 60km is "short" range,
and that the range bands double until you reach extreme range at 240 km.
Sorry, but that won't work.  Amatuer radio operators are limited to 1
kw. And they *routinely* achieve "planetary" range at *AND BELOW* those
power levels. A *5* watt CB can routinely achieve 30 km ranges, given a
decent antenna. And when "skip" is a dactor, they can make
intercontinental contacts (not reliably though!).
 
So *two* changes need to be made for radio. First, the power levels
need to go *down*, or the ranges need to go up. Second, somewhere
between 20 and 100 MHZ, the signals quit bouncing off the ionosphere (if
the planet has one). At that point, range is *restricted* to
line-of-sight. Below it, you can reach whatever range you have the power
for. Oh yeah, the amount of interference has a *major* effect on
*usable* range. :-)
 
Now for the drive problem. This is a twofold problem also. Reaction drives give
 a vehicle velocity by imparting velocity to reaction mass, which goes in the
 other direction. So a constant power input gives a constant exhaust velocity,
 and a constant acceleration.
 
Reactionless drives are converting power plant energy into kinetic
energy (via some sort of magic, as this violates a couple of
conservation laws). But the problem here is that kinetic energy is
proportional to the velocity *squared*. So the amount of energy that it
takes to go from 100 m/s to 200 m/s is 4 times that required to go from
0 to 100 m/s. That means that you *can't* get a sustained acceleration
at a constant power output!
 
If you can convert power plant energy directly to *momentum*, then you
could get a constant acceleration from a constant input energy. But
you'd be breaking more laws.
 
Here's the kinetic energy of 1 ton at various speeds:
 
m/s     MJ
- ------- -------------
100       5
200      20
300      45
400      80
500     125
600     180
700     245
800     320
900     405
1e3     500
 
For a reaction drive, the acceleration is equal to:
 
sqrt(2*(power plant output)*(drive efficiency)/(mass of ship))
 
So a 1 megawatt plant in a 1 ton hull with a 100% efficient drive
will give:
 
Sqrt(2*1e6*1/1e3)=44.7 m/s^2 of acceleration.
 
That's about 4.6 gravities.
 
With a nore reasonable drive effieciency, things drop rapidly. (You *don't* want
 to know what the efficiency of an internal combustion engine is. :-)
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