Spaceship Tech in your Setting

[Fred Brackin]

Originally Posted by Rupert

Rotary reactionless drives are probably sufficient to make HEDM, etc. uneconomic and unnecessary.

No, rotary reactionless only provides 0.1 G per unit. Getting off Earth or a world with similar gravity would require 11 units and Phantasm specified that in his setting they may not be placed in a Central Hull location.

[Anthony]

Originally Posted by Fred Brackin

No, rotary reactionless only provides 0.1 G per unit. Getting off Earth or a world with similar gravity would require 11 units and Phantasm specified that in his setting they may not be placed in a Central Hull location.

It might be possible to fly to orbit with wings, though it's a bit nasty.

[Fred Brackin]

Originally Posted by Anthony

It might be possible to fly to orbit with wings, though it's a bit nasty.

You probably can't do it with Spaceships. With 0.5-0.6 Gs your atmospheric max is going to be extremely low. To dupilicate X-15 performance you'd need 6 Gs and an X-15 can't actually make it to orbit.

[ericthered]

Originally Posted by Anthony

It might be possible to fly to orbit with wings, though it's a bit nasty.

Yeah, we had a big thread on that pulling out all of the mathmatical stops from vehicles. The conclusion was that if you can get off the ground with your thrust and lift, and we don't run into a weird speed at which lift stops working, you should be able to slowly ramp up your total speed and altitude with a reactionless drive until you are in orbit.



I think it took 16 hours or something silly like that.

[Anthony]

Originally Posted by ericthered

I think it took 16 hours or something silly like that.

The problem is mostly that you have to remain in the upper atmosphere until you are going fast enough that you can skip up and not return to atmosphere before you hit orbital velocity, which may mean trying to fly at mach 20 or something.

[Rupert]

Originally Posted by Fred Brackin

No, rotary reactionless only provides 0.1 G per unit. Getting off Earth or a world with similar gravity would require 11 units and Phantasm specified that in his setting they may not be placed in a Central Hull location.

My bad - I was going by memory and thought it was 0.5G per unit. Yeah, that's going to make life difficult without CG.

[lugaid]

Originally Posted by Anthony

more than 30c in deep space (G=1e-10m/s).

When you get to G that low, you're probably also going to want to calculate the G of the ship itself. Figure the mass as a fraction of Earth mass (5.878e21 tons) and the nominal radius* as a fraction of Earth's radius (6.975e6 yards), then use the normal gravity equation (Gs=M/R^2, where Gs is "surface" gravity, M is Earth masses, and R is Earth radii). For instance, an SM+8 ship massing 1000 tons and 50 yards long comes to M=1.7012589316093909493024838380401e-19 Earth masses, R=3.5842293906810035842293906810036e-6 Earth radii, Gs=1.3242769649540660088465464443688e-8G or about 1.2977914256549846886696155154814e-7m/s^2, which you will note is nearly 1300 times greater than your deep space gravity figure.

(With the exception of acceleration, where I used meters/s^2 to match the unit of acceleration in the quoted post, I used standard, non-metric units to conform with GURPS units, for simplicity. I used whatever precision Google returned for the constants related to M and R, and whatever precision my calculator provided otherwise.)

*Call it half the length for simplicity. The difference is actually very small between different human-scale ships.

[mstlaurent]

I actually had a germ of an idea for a setting, might get developed, might not, who knows. The basic idea was that NASA develops a working FTL warp drive in 1982. All other technology remains the same. The power requirements are low enough that you can run it with a fission reactor, but it's very slow by the usual science fiction standards, 12-16c tops. So a trip to Alpha Centauri takes 3-4 months, and an expedition to Tau Ceti takes a couple of years round trip. Project Timberwind is a huge success, so advanced fission drives are the pinnacle of reaction engines. Starships look like what we might imagine a long-term Jupiter mission would look like: large, expensive ships with spin habitats, closed-cycle life support systems, greenhouses, etc. Many of them custom-built for their missions. Still lots of brushed metal panels and white insulating fabric.

[RedMattis]

Originally Posted by Greg 1

The GURPS Spaceships design system offers various alternatives for what is technologically possible, even at a given tech level. Most obviously, decisions have to be made about how spaceships travel faster than light, and what weapons can exist.

What choices did you make (or would you make) regarding what technology is used for spaceships?

Have you tried converting ships other people have made that use different technology? How hard was it?

On a related note, does anyone know of any online GURPS Spaceships collections?

I honestly didn't end up using it. I'm running the kind of Star Wars type of world where buying little space-ship shuttle capable of flying off from a planet and entering 'hyperspace' isn't much more expensive than buying a big car.

Spaceship battles are also mostly a Star Wars-style dogfight unless it is big ships sniping stations or each other with artillery.

I don't have GURPS Spaceships currently, but from what I've read it is fairly realistic even with using "^"-tech, and I'm guessing it wouldn't be useful for my setting where small ships fight like WWII airplanes (fighters, bombers, ...) and the big ones are more like various (naval) ships of war that might (depending on the ship's design) even fly right up to other big space-ships and give them a broadside.

[Jack Sawyer]

Not exactly tech in 'my' setting but given I stumbled across this recently and people may find it interesting...

https://www.afrl.af.mil/Portals/90/D...nce_number.pdf

Its a discussion of the potential course of directed energy technologies (weapons especially) at least as far as the air force is concerned.


I may post things of interest if I can find them. Two of the ideas (and how I stumbled on it) was news articles about the near future viability of Ultrashort pulse lasers by both the air force and army (meaning we're a step closer from just CW lasers to actual atomic-rockets style laser weapons.. perhaps as soon as next year by some claims I've seen) And the idea that certain kinds of directed energy technology might create a sort of 'localized forcefield' pinpoint defense - not so much a bubble shield ala Star Trek but more like Macross/Independence War pinpoint barriers or Babylon 5 interceptors.

Which is still awesome because knowing what is possible or plausible is a big step to defining what you want as internally consistent technology in your setting. Or at least, in mine.