[Spaceships] TL9 Military Spaceships

[thtraveller]

Originally Posted by Langy

The Neil Armstrong class of spacecraft carrier

[5] Advanced Fusion Pulse Drive (0.005G Acceleration, 20 Delta-V/Tank)

Nuclear pellets are very expensive in G:Spaceships. This craft uses $3B of fuel per trip.

A much cheaper alternative, though with somewhat less dV, would be to use a fusion rocket. This would knock $1B off the price tag and drop the fuel cost per journey down to a mere $60M.

[Langy]

Admittedly, the cost of the nuclear pellets is a problem - but when you take into consideration the Von Braun's fabricator, it becomes somewhat less of a problem. A Von Braun is able to construct nuclear pellets from asteroids, taking fifty hours to refill one five thousand ton fuel tank. It takes just under two weeks to refill a single Von Braun or Neil Armstrong-class ship.

For a mission into the main asteroid belt, a fusion rocket-based Armstrong class ship would take two weeks longer to get into the belt and would need to leave two weeks earlier due to the delta-V hit. Going out to any of the other outer planets means an even larger time penalty.

When you take this into account, the fusion pulse drives are much, much more attractive - the extra delta-V translates into extra time on station, which the logistics supply ship will use to refill the tanks while the parasite ships will carry out their mission. The only benefit, then, is to the reduced cost of the original ship or to large, multi-ship task groups which go to one location, do their thing, and then leave quickly.

There are benefits to both types of ship, of course - the Armstrong-class of ships, however, is more for a mobile base than a ship that makes hit-and-run style attacks.


EDIT: Oh, and yeah, you're right about the missile pod's tactical array. It doesn't belong in the Core section - I should probably switch that out with something else, but I honestly can't think of what I'd want it to be right now.

[David Johnston2]

Originally Posted by Langy

Admittedly, the cost of the nuclear pellets is a problem - but when you take into consideration the Von Braun's fabricator, it becomes somewhat less of a problem. A Von Braun is able to construct nuclear pellets from asteroids, .

Only of course if it can find asteroids rich in fissionables. That would likely be months of prospecting.

[Langy]

Er, no. The Fusion Pulse Drive doesn't use fissionables. Nuclear pellets are made from hydrogen isotopes and the like, not uranium or anything like that. It should be relatively easy to find the stuff required for the fusion pulse drive, while the external pulsed plasma drives for the smaller craft need small enough amounts of fissionables that I think they can get them from asteroids easily enough.

[thtraveller]

In TS (Deep Beyond p 152) there is a pellet factory - it takes 5000 tons of rock and 5 pounds of He3 to make 84 tons of nuclear pellets in a month (and lots of interesting by-products).

[Langy]

I don't have the Transhuman Space books, so that doesn't really help - especially without knowing how large the pellet factory is. Also, without knowing what an actual nuclear pellet would be made from or what the actual average asteroid's composition is, it's impossible to say how many asteroids would be needed. I made some estimates on asteroid composition using the rules for raw material costs in Spaceships 2 and what I could find about asteroid composition through a google search, coming up with each ton of asteroid being worth four thousand dollars, which makes it so a ship with mining and refining modules can directly supply that ship's fabricator's raw material requirements for maximum-speed production.

[joelbf]

Originally Posted by Langy

Move: 2G/28.8 mps [2]
LWt.: 30 Tons

With a pod attached this becomes 1G/14,4 mps right?

[Langy]

That's right - doubling the mass halves the acceleration and delta-V.

[thtraveller]

Originally Posted by Boobis

With a pod attached this becomes 1G/14,4 mps right?

Generally I don't think so. The fuel tank delta-V multiplier is based off what proportion of the ship's mass is fuel. Doubling the mass halves the proportion of the ship that is fuel mass. So your number of tanks delta-V multiplier would reduce as if you had half that number of tanks.

Of course if you have less than 6 tanks to start with it makes no difference.

[joelbf]

Originally Posted by thtraveller

Generally I don't think so. The fuel tank delta-V multiplier is based off what proportion of the ship's mass is fuel. Doubling the mass halves the proportion of the ship that is fuel mass. So your number of tanks delta-V multiplier would reduce as if you had half that number of tanks.

Of course if you have less than 6 tanks to start with it makes no difference.

Good point, its probably easiest to halve the number of tanks and calculate dV from there.