message 0158

• Speculations on spaceship (esp. Rider) drive and fuel
• Where did the fleet get its ammunition?

>From: Onno Meyer <Onno.Meyer@arbi.informatik.uni-oldenburg.de>
>Subject: cherryhlist
>Date: Wed, 2 Jun 1993 10:51:49 +0200 (MET DST)

> > - "Raw" water can be heated (for example, by a fusion plant) and then
> >   ejected as water vapor: a simple but efficient rocket engine.
> 	It doesn't corespond to what we see in the books. Assuming the
> exhaust velocity of a ship's propellant was lightspeed the ship would
> have to eject twice its own mass in propellant to boost it up to
> lightspeed, under simple newtonian mechanics. Thus to carry out the
> maneuvers in the books the ship would have to have started off with
> about 98% of its mass as fuel. This doesn't match the picture of the
> Norway on "The Company War" (I have this in a GIF on FTP if anyone wants
> it) let alone descriptions of the ships.

This is a point in favour of a magic engine, but I'm still not convinced,
see my reasons below.
Is this the same picture that appears in the front of _DS_? (There is a
picture of Pell station, too.) If not, where do I get this GIF?
> 
> > - In _Hellburner_, the craft lost an significant part of it's mass
> >   in an instant because it fired and moved. The powerplant would 
> >   consume it's fuel in a more steady manner.
> 	I'd say that was more the weight of the armament. Taking the
> analogy of modern fighter/bombers their payload is a significant
> proportion of their mass. Thus when they exhaust their arms they
> become much more maneuverable.

That's possible. An almost unrelated problem: where did the fleet get    
the ammunition? They could use the same fuel merchanters use, the same
engine spare parts, if their engineers were creative, the same food, but
earth should have been the only source of advanced weapons, unless a
station constructed a whole new industry. Since the stations claimed
they were neutral (see the beginning of _DS_), I doubt this was the
case.
> 
> > - In one of the Chanur books (I boldly assume it's the same technology)
> >   a docking port is hit and someone said that if the "ugly" pipes
> >   hadn't been outside, they would all be dead. this _might_ have been
> >   fuel.
> 	This can be answered along with:
> > - If the engines were hydrogen-consuming plants, why haul all the
> >   unnecessary oxygen that is contained in the water.
> 	There was a long discussion on the Traveller Mailing List about
> how the fuel for the hydrogen-burning powerplants of Traveller was stored.
> It was always assumed to be liquid hydrogen (H2). All the physists came out of
> the closet, though, and pointed out that water (H2O) was nearly as efficient
> a way of storing hydrogen as in its liquified form. It also doesn't need
> special storage. Methane (CH4) apparently wasn't that great but ammonia
> (NH3) was better than water. Perhaps some of the Compact ships (more
> technologically advanced) burn Ammonia rather than Water, assuming
> fusion plants.
> 	Of course in Traveller only the *volume* of the ship is considered
> when computing drive speed rather than *mass*. There is a much lower
> %weight of hydrogen in water/methane/ammonia than pure hydrogen.
> 

But we know that both sublight acceleration and jumpspeed depend on
the ratio of ships mass and engine power. This Idea of a volume/speed
relation is convenient for a game ("With 200 tons of cargo and 70% fuel    
we have an acceleration of, err, ... ,just a moment, ...") but it violates
both physics as we know it and physics as described in the books.

And, if the fuel was needed for an fusion plant, the plant would have
to be really big to use a significant quantity of fuel. I've found a
physics book that said if the Tokamak(?) design should work, a
30.000 MW plant would use 10kg of fuel every day. With such a plant
no starship should have to rely on station power, but the compact 
ships routinely hook up to station power lines.
> 
> 				Jo
>