Weinbaum atomic engines

[ffutures]

Re. space travel in the Weinbaum RPG, I'm going with nuclear engines that give about 0.01-0.02g acceleration in sustained flight, which are the best fit for the travel times mentioned in the stories.

Now obviously this isn't going to be much use for takeoffs and landings, and I can either go with auxilliary engines that have higher power output but can't be run for a sustained time, or with an "emergency / takeoff / landing" setting on the main engines, like using the afterburners on a jet. A lot more power, but it burns through fuel extremely fast, say 200 times as much fuel for 100 times as much thrust. E.g. to get 2g for 10 minutes uses as much fuel as .02g for 2000 minutes, about 33 hours. And 33 hours at 0.02g will take you a LOT further than 10 minutes at 2g.

Does this sound reasonable for game purposes?

Later: To clarify this, my best guess for travel times is a few weeks for Earth-Mars and Earth-Venus, with Saturn to Neptune and beyond just on the edge of the possible. In The Red Peri they imply that Saturn-Pluto (about a billion miles) can be done in three months or possibly less, but they don't give exact times.

Assuming that it'll take three months for the 1 billion mile trip under normal circumstances, that's about 0.01g cruising acceleration /deceleration. Plugging in a range of values gives 1 billion mile trip times of:

0.01g = 93.7 days
0.015g = 76.5
0.02g = 66.3
0.025g = 59.3
0.03g = 54.1

And Earth-Mars times at conjunction of:

0.01g = 20.2 days
0.015g = 16.5
0.02g = 14.3
0.025g = 12.8
0.03g = 11.7

I think I'm going to go with 0.01g for the earlier ships in e.g. A Martian Odyssey, 0.02g to 0.03g for later ships.

Comments

[gonzo21.livejournal.com]

Sounds fine. A little complicated for my liking, but then I was never one for rules.

[ffutures.livejournal.com]

Well, it is rocket science, but it can mostly be handled by spreadsheet templates.

[jordan179.livejournal.com]

That's actually quite consistent with the real-world performance of a high-energy ion drive (the kind that is essentially shooting out an electron beam rather than charged metals). A low-energy ion drive (like the ones we actually have now) would yield about a tenth the acceleration).

Weinbaum's ships are obviously atomic-powered (probably fission, to the extent that 1930's concepts of "atomic power" relate to the real thing). So they could probably thrust continuously, even though they might instead boost out of orbit and then boost back into orbit. I'm not enough of an astrogator to say much about which would be more fuel-efficient. I'd guess that they would have discovered and used all real-world techniques such as Hohmann transfer orbits and slingshotting.

I don't recall Weinbaum explaining the avionics of his spaceships. Like most pre-1960's authors, he probably didn't expect electronic computers to advance anywhere near as far as they did, and I don't remember him writing a lot about robots or robot brains. This would be consistent with a non-transistor world, though they probably have at least good electromechanical or vacuum-tube-based automatic calculators and controls to help their astrogators and pilots. Plus, of course, the Trusty Old Slide Rules :)

The "high throttle" setting for landings and takeoffs makes the most sense as I do not recall Weinbaum ever mentioning using two separate drives, one for planetary use and one for interplanetary use, as would be the case if there were both chemical and nuclear rockets on the ships. There's also a clear example of a "hot-shotted" nuclear power system in use in the stories -- the disposable-crystal energy pistols -- presumably you'd want something a little smoother for landings and takeoffs, of course.

[johnreiher.livejournal.com]

If you haven't been to this web site, and I think you have, take a look at the Atomic Rocket Page! There is a lot of information here. In particular:

Blast off!

and

Engines

I also know that the folks on the SFConsim-l would love to help you out on this as well. They are made crazy over Atomic Rockets. It is a Yahoo Group, but these folks live for this kind of stuff.

[ffutures.livejournal.com]

That's pretty much my own chain of thought including the pistols - some of the ships are mentioned as having "underjets" but they are invariably craft designed for exploratory flights where they will be flying around in atmosphere for extended periods. The nearest thing I can find to a modern computer in any of his stories is the automaton of The Ideal, which is VERY primitive, so I think we're still using slide rules, astrogation tables, etc.

[ffutures.livejournal.com]

I have had so many problems with Yahoo groups that I really don't want to go there, I'm afraid. I've seen the atomic rocket page, it's useful but Weinbaum's version of atomic power doesn't bear very close comparison with the real world, and there will be a certain amount of hand waving at the more technical stages.

[jordan179.livejournal.com]

I think I'm going to go with 0.01g for the earlier ships in e.g. A Martian Odyssey, 0.02g to 0.03g for later ships.

If you do that, then you can create a rough functional correspondence with maritime "knots" of speed. 0.001 g = 1 knot, meaning that the first crude ships of the late 20th / early 21st centuries are doing the equivalent of 5-12 knots (like the early steamships. Sometime around the mid to late 21st century you could have the equivalent of the "turbine revolution" leading to ships doing the equivalent of 15-20, and eventually as much as 30-40, knots during the 22nd century.

At some point the "airplane" (plasma or fusion rocket) could be invented and things transcend to new orders of speed. That would be in the future of the Weinbaum universe.

[ffutures.livejournal.com]

Maybe, but I probably won't speculate on that much; given the lack of computers etc. it might take a long time to advance the technology much.

[jordan179.livejournal.com]

Maybe, but I probably won't speculate on that much; given the lack of computers etc. it might take a long time to advance the technology much.

Yeah ... if such a technology did come to pass it would probably be some special crystal inherently channeling the magnetic fields, much like the crystals in the flame-guns can store and discharge immense energies (perhaps through some nuclear process), rather than the way we'd do it (through actively controlling the force fields at electronic/photonic speeds).

As I'm sure you've noticed, there is a potential source of all sorts of weird wonders -- the prehuman civilization or civilizations that attained interplanetary travel. Tweerl's folk, and the Loonies, and maybe more.

[ffutures.livejournal.com]

Definitely - I've got the Slinkers (which appear to be the same species as the Martian rats) pegged as the Big Bad responsible for wiping out earlier civilizations. Somewhat like the little Moties, perhaps?

I don't want to do too much with prehistoric Tech - Traveller and other games mined this one to death, they'd find another bit of Ancient tech whenever it suited the plot, and it got to be really annoying.

[jordan179.livejournal.com]

One thing the atomic rocket page is good for is outlining the challenges of spaceflight -- which, in an early-to-mid-20th century SF universe, might be met with very different technologies, possibly based on different physical assumptions. Of course, in some universes, even the challenges might be different.

When it comes to nuclear physics, by the way, I'm far from convinced that we've figured out everything, in a science only about 100 and technology only about 65 years old. I don't think that we'll necessarily ever get anything like Golden Age "atomic converters" (feed any mass in, get out emm cee squared energy), but I wouldn't rule it out, either.

The astrophysical differences can be harder to explain logically. What I do is make a "parallel pasts" game using "resonance effects" to explain, for example, that Jane Austen wrote Pride and Prejudice in our world, Weinbaum's world, and Stapledon's world, even though the pasts and futures of those worlds, once you step beyond the period of history known to the writer.

[jordan179.livejournal.com]

Definitely - I've got the Slinkers (which appear to be the same species as the Martian rats) pegged as the Big Bad responsible for wiping out earlier civilizations. Somewhat like the little Moties, perhaps?

Hmm ... you're right, to the point that I wonder if Niven & Pournelle were inspired to this by Weinbaum?

Continuing the Motie Watchmaker analogy, what if the Slinkers were either a tool (or caste) of something worse, or they metastasize into something worse when they reach some critical level of technology or population density?

I don't want to do too much with prehistoric Tech - Traveller and other games mined this one to death, they'd find another bit of Ancient tech whenever it suited the plot, and it got to be really annoying.

True. Though it is in the pulp tradition :)

The key is, I think, to not let it overshadow the story of the "present-day" human civilization.

[ffutures.livejournal.com]

I'm actually writing a sidebar on Martians tonight (there will be a lot more later in the book), which says that they are believed to have used chemical rockets - Weinbaum says that they have plantlike features, so it doesn't seem impossible that they took years rather than months per flight, spending most of the time rooted.

[idaho-smith.livejournal.com]

Except for one afternoon about 4 years ago, I haven't played an RPG for nearly 12 years....

You probably know this already, but R.A. Heinlein wrote about about constant-acceleration ships quite often, accelerate halfway-there, deccelerate the other half. In "Expanded Universe" he revealed the number crunching on the issue and revealed that it was possible to travel to the more outermost planets at "tea-clipper" time-scales. IIRC he was talking about 0.05g or 0.1g, as these would also give a nearly decent cabin-"gravity". I could pull out the articel for you, but I won't recalculate the figures, I'm too busy the next few w/ends.

As for take-off/landing you'll spend a lengthy & stressful while rising from a planet in a ship that only does 0.01g; how about lightweight chemical (or double-talk) fuelled "landing boats"?

[ffutures.livejournal.com]

The number crunching is pretty easy - I wrote a spreadsheet for it a long while back when I had much more faster continuous acceleration ships in an earlier release of the game - it's here:

http://www.forgottenfutures.org/game/templts/index.htm

The only thing is that some of the columns are too narrow for the long travel times at 0.01g etc

Weinbaum makes it clear that the big ships do take off and land, it's a major plot point in a couple of his stories. There don't seem to be any space stations or separate landing craft, it's one of the things I'm going to have to explain and I'm not looking forward to it. The ships do appear to have a high-power setting for takeoff and landing, they just can't use it all the time. The first Martian expedition does carry a couple of smaller exploratory craft for use in atmosphere, but they're also atomic - that's another one I'll need to explain.

[ffutures.livejournal.com]

Forgot to say that the travel time spreadsheet is based on Heinlein's article - only I cheated and used metric behind the scenes because it's so much easier to work with.

[idaho-smith.livejournal.com]

Metric easier? Hell yes!