Bad News from the Physics Frontier!

Hold on, no offense but you're acting like a physicist :-).
Your figure for the amount of energy from fusing 1 ton of
hydrogen into helium is about 2.6 MegaJoules.  Now, an
engineer :-) would look at that and say "We currently have
power plants that put out thousands of Megawatts, and they
certainly aren't fusing thousands of tons of hydrogen every
second.  I must have goofed."

I double checked and got:

Hydrogen: 1.00794 grams/mole    Helium 4.0026 grams/mole

4 H  -  1 He  =  0.02916 grams/mole of matter converted to energy

1 ton of Hydrogen is 992122.547 moles so there are

(992122.547 moles * 0.02916 grams/mole) = 28930.3 grams of
matter converted to energy.  Or 28.93kg since I hate cgs :-).

Use E= m * c^2 to get

E = (28.93 kg) * (3.0 x 10^11 m/s)^2 = 2.60 * 10^24 Joules

Your figure for the energy consumed by a scout ship accelerating
at 1G for 1 hour, 6.76 E 14 Joules, is correct.

So using the new figure for energy from fusing, this scout ship
will have consumed

[ 6.76 E14 Joules  /  ( 2.60 E24 Joules/ton of H fused)] =
        = 2.6 E-10 tons

or 260 micrograms of Hydrogen fused.  I think we have the
reverse problem!  This process is too efficient!  To burn
(how much does a scout ship hold?) 20(?) tons of hydrogen
in 4 weeks of constant use, we'd have to operate at, oh...
0.0000002% efficiency (within a couple orders of magnitude)
==
John H. Kim
[email removed]
[email removed]

Regarding your straightline vs. curve path for interplanetary travel: The
inefficiency factor is not worth considering as long as you actually have the
enrgy to do it...do you program an IBM compatible in machine language because
it gets you the extra performance?  No...because the performance that you get,
even wioth four layers of help programs and user interfaces that chew up a good
deal of machine speed and memory is still greater than most people can keep up
with.  (e.g. your word processeor input buffer won't overflow no matter how fast
you can type).  Do you turn off your car's engine when going downhill?  No,
because gas is (still) cheap enough to ignore minor economies like that.

If you were going to go Earth to Jupiter (refueling pattern) at 1-G constant
boost, it would take how long (assume an average distance between the two).
Less than two weeks?  If the actual variation in path in less than 10% of the
total lenght, I'd say ignore it for game purposes...now if you have an old
TL8 asteroid miner with an ion drive, and an acceleration in the .001s of
Gs, this would be a different matter entirely.  I figured recently that Earth
to Mars at a constant accelration of .001G would take something like 289days,
which is a poor approximation, because I used the shortest straightline
difference between the two, and a course at this sort of acceleration would
be a much longer curve.  The Hohmann transfer time for mean separation of
the planets would be 360+ days (I forget the exact number).  Intuitively,
I should be able to trim SOMETHING off that by constant boost, however small.

Sorry about the typing today.  Much too tired.

Rob Dean

Orcinus orca [email removed] writes:
> 4 H  -  1 He  =  0.02916 grams/mole of matter converted to energy
> .....
> I think we have the reverse problem!  This process is too efficient!

It's still wrong anyway.  You can't fuse 4 H (=4 protons) into a He (=2 protons
+ 2 neutrons); you need two deuteriums (an isotope of hydrogen with a proton
and a neutron) or an ordinary hydrogen and a Tritium (=proton + 2 neutrons).
You could also have some exotic reactions with 3 atoms, or perhaps involving
lithium.

I always assumed Trav refining plants were heavy hydrogen isotope extractors,
although why having too much ordinary hydrogen in the fuel should cause
misjumps is a mystery.

Unfortunately I don't have a molar weight for deuterium handy.
+-----------------------------------------------------------------------------+
  Tim Day        [email removed]       | I honestly think you should sit down
  Department of Insanity and Surveying | calmly, take a stress pill and think
  [address removed]                    | things over.               -HAL 9000
+-----------------------------------------------------------------------------+