[Space] Steampunk Firefly Idea

[Daigoro]

Originally Posted by Peter Knutsen

Really? I'm surprised at this. It's been my impression that if, e.g., Earth's gravity had been just 5% lower, getting up into orbit would have been much easier. Still requiring a 3-stage rocket, probably, but much cheaper, and with much less of having to stretch TL7 engineering to its absolute limits.

Following the formula, escape velocity goes with the square root of the gravity "g", so halving the gravity would give 0.7 of the escape velocity. Note though that distance from the centre of mass "r" is also a factor, so a smaller moon would have a lower escape velocity than just the difference in gravity would indicate.

[Fred Brackin]

Originally Posted by scc

I've built surface to orbit spaceplane, 23.2 tons cargo, 64.5 tons Hydrogran-Oxygen fuel, $51,600 to refuel, interface rates of $2,224.137931 per ton, or under $1.20 per pound, or $2.40 after putting in a generous allowance for other costs, very cheap. Trans-Lunar shipping costs are probably about the same, so a shipper being charged $5 per pound and charging $10 per pound is probably the prices for moving goods

How do the astronauts get _back_ from the new moon they visit?. There is very unlikely to be a long, smooth runway for any spaceplane you brought up in pieces and attached to a trans-lunar tug.

So no safe landing an no take-off afterwards.

[scc]

Swap out one of the cargo holds for a soft landing system? But the point I'm aiming for will probably be 50 years AFTER the establishment of the first trans-lunar colony, making it a moot issue for the most part

[malloyd]

Originally Posted by Daigoro

Following the formula, escape velocity goes with the square root of the gravity "g", so halving the gravity would give 0.7 of the escape velocity. Note though that distance from the centre of mass "r" is also a factor, so a smaller moon would have a lower escape velocity than just the difference in gravity would indicate.

But that can be quite a significant drop in difficulty, because delta-V goes as the log of the mass ratio. For example if the gravity of the Earth were 0.9 g, the mass ratio for a near ideal kerosene burning rocket falls from 12.2 to 9.5, you maybe *could* cut a stage. If it were 0.7 g, it falls to 5.8 and single stage to orbit starts to look plausible.

[Fred Brackin]

Originally Posted by scc

Swap out one of the cargo holds for a soft landing system? But the point I'm aiming for will probably be 50 years AFTER the establishment of the first trans-lunar colony, making it a moot issue for the most part

<shrug> Okay, we won't look at the rocket engineer behind the curtain. I just wanted to point out that you didn't really have viable colonization ability at a hard science TL7.

[Daigoro]

I don't know how far you've progressed with history or anything, but this is what I might do with the idea.

I'd have conjunctions, perhaps with the help of an uninhabitable intermediary moon, that make transfer between the inhabited moon and one of the other moons easier, but only occurring every few decades. This allows for the occasional wave of lower tech colonisation events to have happened in the past, by the setting's mad scientists, religious cults, or now-defunct superpowers (think of Portugal today).

The setting's modern tech allows freer transport between the worlds and so they are just coming to grips with the secret settlements and power bases that were established decades or even centuries ago.

[Anders]

Originally Posted by malloyd

But that can be quite a significant drop in difficulty, because delta-V goes as the log of the mass ratio. For example if the gravity of the Earth were 0.9 g, the mass ratio for a near ideal kerosene burning rocket falls from 12.2 to 9.5, you maybe *could* cut a stage. If it were 0.7 g, it falls to 5.8 and single stage to orbit starts to look plausible.

So what we need is an enormous cheese-slicer to slim down Mother Earth.

[scc]

Originally Posted by Fred Brackin

<shrug> Okay, we won't look at the rocket engineer behind the curtain. I just wanted to point out that you didn't really have viable colonization ability at a hard science TL7.

What exactly is the problem as you see it then?

[Anaraxes]

Somehow the phrase "hard science TL7" got into a thread titled "Steampunk Firefly".

[scc]

Both Steampunk and Firefly are pretty hard sci-fi