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O'Neill Colonies (L5)

The nauvoo in the expanse was built for acceleration at first, since at a constant 1 g it would take 6 months to get up to .5 lightspeed, 350 days for lightspeed.. Technically.. then on its coasting phase it would be rebuilt for spin for the coasting then rebuilt for decel.
At minimal accel it would take 100s if not thousand years to get to another system. Then you'd have to worry about crap breaking ob the trip.

I remember a Voyager book where they encounter a o'neill hybrid system ship with many cylinders connected , maybe 20? And they were trying to outrun there sun going nova.
 
The Epstein drive has an insanely and unrealistically high specific impulse (Isp) and thrust in any case. According to The Exanse wiki, the Rocinante has a thrust of 6.37MN and an Isp of 1,927,000 seconds in vacuo. That's just shy of the thrust of a single F-1 rocket engine used on the Saturn V first stage (7.77MN in vacuo) but about 6,400 times the Isp (304s in vacuo). One design for the 10m diameter Orion nuclear pulse propulsion engine had a thrust of 3.5MN and an Isp of 2,000s, which is still 1,000 times smaller than the Epstein drive.

Note: Isp is a measure of how effectively a rocket uses propellant. The holy grail is high thrust and high Isp.

Anyway, if there are sufficient resources in the solar system, why take the risk and expense of travelling to other stellar systems while the Sun will keep shining for another 5 billion years? Gravity wells - who needs 'em?
 
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XCV330 said:
...It's like the people assigned to repaint the Eiffel Tower. they never actually stop repainting it. It's just a multigenerational job.
Click to expand...
That same myth is said about the Golden Gate Bridge. But, in fact, the Eiffel Tower only gets repainted about once every seven years (link) and, since it's painted by hand, that takes about 3 years each time. That means 57% of the time it's not being worked on (I assume except for maintenance if any of the paitn gets chipped off).
 
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The NERVA XE had a design thrust of about 250kN and an Isp of about 840s in vacuo compared with 1MN and 420s for the Rocketdyne J-2 used on the Saturn V second and third stages. People will probably still not be happy with the risks associated with nuclear material being launched into space but to me it does seem a much better use for it than sitting around decaying in the warheads of strategic deterrents.
 
Agreed. I want all fissile material off world.

We have to focus on large structures in space.

Imagine that every researcher on Earth had to do science while in boot camp followed by a decathlon. That is ISS for you—and the time is scripted like a professional wrestling match.

With shirtsleeve conditions zero gravity is a walk—not a launch—away.

You CANNOT put a price tag on that spontaneity.

I am glad to see LV growth, but I think it is time to focus not on reusability (Musk has that) but with LVs designed around payloads.

Each country designs different LV concepts so as to avoid duplication of effort.

China still uses hypergolics-so be it. So I think they should focus on OTRAG.

This allows very wide payloads to fit on top.
But then I think—why must that be so?

Imagine an OTRAG dual cluster—the two cookies of an ice cream sandwich.

The ice cream IS the length wise payload— a flat plate many meters on a side, with the few OTRAG “bars” that remain harvested as wet stage rods also for construction.

SPSS and colonies can be built fast this way
 
publiusr said:
Agreed. I want all fissile material off world.

We have to focus on large structures in space.

Imagine that every researcher on Earth had to do science while in boot camp followed by a decathlon. That is ISS for you—and the time is scripted like a professional wrestling match.

With shirtsleeve conditions zero gravity is a walk—not a launch—away.

You CANNOT put a price tag on that spontaneity.

I am glad to see LV growth, but I think it is time to focus not on reusability (Musk has that) but with LVs designed around payloads.

Each country designs different LV concepts so as to avoid duplication of effort.

China still uses hypergolics-so be it. So I think they should focus on OTRAG.

This allows very wide payloads to fit on top.
But then I think—why must that be so?

Imagine an OTRAG dual cluster—the two cookies of an ice cream sandwich.

The ice cream IS the length wise payload— a flat plate many meters on a side, with the few OTRAG “bars” that remain harvested as wet stage rods also for construction.

SPSS and colonies can be built fast this way
Click to expand...

OTRAG had a poor mass fraction. The only people in recent memory who looked at it seriously were Armadillo, and as cool a group as they were, they were all over the place. And it only takes one catastrophic failure on one of those Otrag units to cause LOV and most likely LOC.

It's easier and cheaper to make turbopumps than before, or highly efficient electronic pumps. OTRAG isn't going to happen. Anyway, I'm not sure what it has to do with O'neill cylinders. Most of the mass for one of these has to come from lunar and asteroidal materials. solar system tugs could make good use of NERVA, but not otrag.
 
Asbo Zaprudder said:
The NERVA XE had a design thrust of about 250kN and an Isp of about 840s in vacuo compared with 1MN and 420s for the Rocketdyne J-2 used on the Saturn V second and third stages. People will probably still not be happy with the risks associated with nuclear material being launched into space but to me it does seem a much better use for it than sitting around decaying in the warheads of strategic deterrents.
Click to expand...
Yeah, I would be curious to what we could have done if they actually had NERVA's up there, and of course how much we could have refined them over time, a ship powered by these could indeed move stuff around, not only for space habitats but for asteroid mining and everything else you can think of.
 
If one is going to drag OTRAG into the discussion, one might as well throw Orion NPP and Sea Dragon in there as well. More interesting to me is the minimum amount of stuff needed to seed self-sustaining resource exploitation of space without requiring big dumb boosters to haul megatonnes of material off the surface of the Earth.
 
The modular nature of something like OTRAG meant that (perhaps) wife panels many meters on a side could be lofted as one big piece...that could help with construction.

How about the idea of a “hollow” rocket?
Imagine an LV that is really just a tall torus with a long narrow payload that is the length of the LV. There would be strap-on boosters to detach...and once the payload for station construction is out—you have a double hull tube that can now be filled with water and other shielding/working fluids.

The idea is to go beyond just sticking a limited payload atop a standard rocket. I really think a colony will be built with Earth resources first. Asteroid mining in the near term? Not so much.

The idea of wet stages made to be part of floor space as opposed to flying back—that needs to be looked at.

Over at Harvard SEAS lab there is talk about balloons that open up to a pre-selected shape due to kirigami creases/cuts...from Lishuai Jin, and aerogels with silver nanowires and cellulose (maybe from Duckweed and melanin) is the lightest rad shielding yet.
 
publiusr said:
The modular nature of something like OTRAG meant that (perhaps) wife panels many meters on a side could be lofted as one big piece...that could help with construction.

How about the idea of a “hollow” rocket?
Imagine an LV that is really just a tall torus with a long narrow payload that is the length of the LV. There would be strap-on boosters to detach...and once the payload for station construction is out—you have a double hull tube that can now be filled with water and other shielding/working fluids.

The idea is to go beyond just sticking a limited payload atop a standard rocket. I really think a colony will be built with Earth resources first. Asteroid mining in the near term? Not so much.

The idea of wet stages made to be part of floor space as opposed to flying back—that needs to be looked at.

Over at Harvard SEAS lab there is talk about balloons that open up to a pre-selected shape due to kirigami creases/cuts...from Lishuai Jin, and aerogels with silver nanowires and cellulose (maybe from Duckweed and melanin) is the lightest rad shielding yet.
Click to expand...

If settlements cant be build with lunar and asteroidal resources, they probably don't need to be built.
 
publiusr said:
Well, you need large structures first— and they can be used for asteroid mining platforms.
Click to expand...
We're closer to having the beginnings of lunar infrastructure than we've ever had. I am optimistic that lunar manufacturing could begin before 2050 on habitat structures.

Mining https://en.wikipedia.org/wiki/162173_Ryugu could give you a lot of the other materials needed that the moon cannot provide. It would make a very good early candidate for mining.
 
I guess we can 3D print a lot of stuff in space even metal parts like rocket engine bits, start small and with 3D printed bits build machines that can build larger and larger stuff, we didn't have tech like that in the old days, I think that new materials and techniques could really make space habitats possible and maybe not even that expensive if you can start building the needed machinery in space instead of hauling it up from this big gravity well.
 
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