SFRPG

Just as a thought experiment and gearhead 'What If' ...

Using Traveller rules (any flavor) as a starting point, does anyone have any thoughts on the plausibility of a TL 5 (1900-1940) Robert Goddard to VanBraun ('V2' or 'V4' rockets) space faring culture (interplanetary rather than interstellar). Could Dieselpunk form the start of a plausible or interesting setting?

I would start by suggesting a smallest practical earth-like world ... would size 4 hold an atmosphere?
This reduces the gravity well to a level that makes access to orbit more practical.
I once read that a beanstalk from the lunar surface to orbit could be done with standard commercial steel cable available off the shelf at most industrial TLs. I wonder if you could haul objects to orbit on a Size 4 world at TL 5?

So any thoughts or opinions?
Am I the only one who thinks Steampunk (TL 4) and Dieselpunk (TL 5) in space is interesting?

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I really love Classic Traveller, especially without the Imperium ... There, I said it.
Now pass me a laser carbine and a couple of extra battery clips.

I think any world capable of retaining oxygen and water vapor will probably have surface grav of at least 0.5 or 0.6, depending. You've lowered escape velocity in that case by half, which would probably make rocket science a lot easier. Maybe SSTO right from the start?

Interesting. Liquid-fuel rockets are almost exact contemporaries with the jet engine, and they have similar engineering in a lot of ways. I'm not convinced that it's terribly plausible to have spaceships without jet aircraft, and perhaps that's getting us out of the diesel era. Rockets without transistors and integrated circuits do seem possible, though.

As for the small planet, the limit on retaining a bio-compatible atmosphere (i.e. one containing oxygen and water vapour) is determined jointly by the planet's escape velocity and the temperature of the upper atmosphere. You ought to estimate what is the coldest average surface temperature your planet can have, then give it the weakest greenhouse effect that is compatible with a moist and breatheable atmosphere, that will give you the lowest possible black-body temperature, which in turn will let you retain an atmosphere with the lowest possible escape velocity. The "basic World Design Sequence" in GURPS Space 4th ed. contains the tools you want. Examine particularly the boxed text on p.85 ("Turning Up the Heat") and that on p.86 ("Worlds Big and Little").

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— Brett Evill

My SFRPG setting, Flat Black

© My posts on SFRPG must not be reproduced beyond the board except with explicit permission from me.

Not exactly! Escape velocity is proportional to SQRT (M/r) = SQRT (ρ r^3/r) = r SQRT(ρ). But surface gravity is proportional to ρr. So if your light gravity comes from a low density and not a small radius that doesn't help as much as if it comes from small radius. But in any case it is escape velocity (and exosphere temperature) that determines the retention of gases against Jeans escape, not surface gravity. And that means that what you want to combine a moist breathable atmosphere with low escape velocity is not a small planet but a cold one.

_________________
— Brett Evill

My SFRPG setting, Flat Black

© My posts on SFRPG must not be reproduced beyond the board except with explicit permission from me.

I'm sceptical about that. Since the Moon rotates synchronously with its orbit around the Earth, anything in stationary orbit around the Moon would be stationary with respect to the Earth-Moon system, which is the definition of the Lagrange points. A lunar beanstalk would have to have its centre of mass at L1, L2, L4, or L5.

Perhaps the author of what you wrote meant a world the size of the Moon, not the actual Moon itself.


Speaking of which, another planetary characteristic that would help make space travel easy early is fast rotation, i.e. a short day.

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— Brett Evill

My SFRPG setting, Flat Black

© My posts on SFRPG must not be reproduced beyond the board except with explicit permission from me.

Thanks for the input on world design.

For 'Jet Engine/Rocket Engine' design, what about ...



... although your question about whether or not this is still Dieselpunk, is valid.

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I really love Classic Traveller, especially without the Imperium ... There, I said it.
Now pass me a laser carbine and a couple of extra battery clips.

Well, that's even worse. I think you have to go to solid-fuel rockets to get any earlier that.

_________________
— Brett Evill

My SFRPG setting, Flat Black

© My posts on SFRPG must not be reproduced beyond the board except with explicit permission from me.

To get a pure Dieselpunk Space would probably require a piston engine driven Aether Propeller ... of course, Aether is more Victorian Steampunk than Dieselpunk ... so I guess that a compromise will be needed somewhere along the way.

I would start with these very early pulse-jet engines for clues about TL 5 metalworking capabilities and for graphic clues about what form a Dieselpunk Rocket Engine might take.
I was looking at a three stage to orbit for manned launches ...
[Stage 1] [USS Akron]-like hydrogen airship drop launches an X1-like pulse-jet second stage at altitude.
[Stage 2] Small improved Congrave-like solid rockets boost the craft to critical velocity to start the pulse-jet. Pulse jet carries the third stage on a sub-orbital trajectory and releases it at apogee.
[Stage 3] a V2-engine rocket boosts the craft to stable LEO.

Like the saying goes, once you are in orbit, you are halfway to anywhere.

Interplanetary, I see solid-fuel cargo flights and liquid-fuel manned flights with H2O2 teakettle thrusters for fine control.
I would follow a small steps plan for travel ... Station in LEO, Station at Lagrange Point, Station at destination orbit ... special rocket from surface to LEO Station, space taxi orbit-Lagrange-orbit, special rocket orbit to surface (moon of gas giant?).
Perhaps there is an Asteroid Station to support asteroid mining?
If we get to low enough gravity, I would start to look at a tower from the surface to orbit ... or a cable from stationary orbit to planetary surface (the devil will be in the details).

Aesthetically, we get Art Deco and the Streamlined Era for structures and vehicles ... flight suits and coveralls and goggles for clothes.

[EDIT: Corrected name of Aircraft Carrier Airship.]

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I really love Classic Traveller, especially without the Imperium ... There, I said it.
Now pass me a laser carbine and a couple of extra battery clips.

But rockets have been around since the first invention of gunpowder, so postulating a rocket within a Dieselpunk setting would make sense, as long as you explained it properly.

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My friends call me Richard. You can call me Sir.
www.XmasDragon.com

Part of the fun/challenge is figuring out what they should look like.
At TL 4 (roughly 1860-1900 in real life) the actual working rockets were black powder tubes and Sci-Fi authors planned on shooting a capsule out of a giant canon.
By the late 1940's and the V2, we are setting the stage for the 1950's 'Atomic Age' science-fiction where rockets all look like a V2 with a ladder.

So technologically and aesthetically, what falls in between the two?
What do the 1920's to 1930's in space look like?

What about a solid fuel rocket with a liquid oxidizer? A binary fuel to allow the solid fuel to be turned on and off?

Tell me the image of air launching a rocket by dropping it from an airship isn't just plain interesting.

_________________
I really love Classic Traveller, especially without the Imperium ... There, I said it.
Now pass me a laser carbine and a couple of extra battery clips.