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[Max™]

Meh, just go with loop/fountains until we get enough exp to buy the ultramaterials dlc and unlock mass production of various -ene arrays suited for elevator nonsense.

[Trekkin]

To me, the obvious solution is either a combination of launch-loop or lightcraft ground based first stage ascent, with nuclear final ascent. At least if we are talking "Super heavy lift vehicle launching a colony ship or permanent space habitat" type scenario.  Those would get very infrequent launches (due to costs of building the thing to launch as well as the costs of launching it themselves), so nuclear propulsion is less of a long-term problem, especially very high up in LEO.

Would not stop the morons NIMBY types from complaining about nuclear propulsion though.  In terms of delta-v per pound it is very hard to beat old school proposal for Orion.

The biggest problem with that is that both launch loops and laser arrays have a finite maximum payload capacity built into the structure, and it's more expensive to increase than for a launch pad. Unless we're regularly launching vehicles of that mass into space, much of that excess infrastructure is going to do little more than cost money to maintain, and as you point out, we wouldn't be.

Additionally, I should point out that the launch loop is designed to take care of what I presume you mean by "final ascent" for the payload, which is why it's so long; the only kicker motor absolutely required is for circularization. Lightcraft have the advantage of freedom of trajectory, but they do suffer more losses in air as the craft gains altitude so the "final ascent" would actually need to begin at some point in the middle of the zero-lift turn, particularly if we assume the limiting factor on low-altitude acceleration is max Q. (Since we can always build more lasers, this seems likely to me.) That's still lighting a nuclear engine in the atmosphere, which means running it during launch to have it hot -- and while several engines can handle that we can't say the same of hippies.

My first guess at an optimal solution would be to spread out the payload by loop load in whatever size chunks our rotor will accommodate and limit rocket launch to anything too big for the loop, which makes the expense of large rockets easier to accommodate; at that point, we have the spare payload to up-armor an orbital nuclear fuel carrier beyond all reason and can deliver the fuel for the Hohmann transfer stage into LEO by bog-standard, reassuring RP-1/LOX rocket. You could do a similar thing with a space fountain, but then you need to chemically remove the entire very big thing away to minimum safe distance before transfer ignition, so the gains are minimal. They're a great place to stick momentum exchange tethers for recovering the kickers, though.

[Max™]

Full honesty: fountain just seems easier to me because I juggle, loops have the kicking shit out to orbit ready velocities going for them but it's like some fiendish mishmash of doing lasso tricks with a fly-fishing rod as you rattle off rhymes and jump double-dutch.

[wierd]

Launch Loop is basically a high tech trebuchet, with a wind-up before the pitch.

There are potentially fatal G-forces during the wind-up and pitch phases though, which makes them potentially troublesome for crew launch.

That is one of the areas where a lightcraft might be better suited; Crew launch as seperate launch. One big launch with lots of crew aboard, rendezvousing with the loop-launched starship in orbit. 

[Trekkin]

Launch Loop is basically a high tech trebuchet, with a wind-up before the pitch.

There are potentially fatal G-forces during the wind-up and pitch phases though, which makes them potentially troublesome for crew launch.

No, there aren't. This is literally the whole reason Lofstrom gave it the dimensions he did: they're suitable for launch into orbit, albeit with atmospheric perigee, while limiting acceleration to 3 g, the same as astronauts go through during a rocket launch. EDIT: Or your average Gravitron rider. 3g eyes-in isn't potentially fatal unless you're already in poor health.

It's also not really at all like a trebuchet in any way, so I'm wondering if we're talking about the same thing.

[wierd]

I could have sworn...  what I am seeing now when I google launch loop is not what I remember seeing or reading when I looked them up in the 90s. (Clearly the design has changed considerably.) 

What I remember seeing was more a closed track composed of a large, wide turn section, a straight away, then a sudden, tight turn.  The payload is attached to a tether, is accelerated on the large loop section, diverted on the straight away, then "whipped" around the tight turn, and detached at the right moment.  That is VERY DIFFERENT from what I am seeing here.  The expected G-force on the "launch" portion would be extreme in the version I remember reading about. (Like, liquefy the humans kind.)

Another alternative I have just now seen is a "Slingatron"-- which would likely produce lots of vomit from human passengers as well. (It is a spiral shaped magnetic acceleration ramp/tube, with the craft being essentially chucked out like a discus, as the craft "rolls" along the wall of the launch rail.)

[scourge728]

PTW

[Max™]

Yeah Lofstrom (cool guy btw. used to bs with him on the xkcd forums) proposed shit that would be difficult because it's like building a bridge across the pacific, full of electromagnets whooshing around fast enough that the loop is actually lifted away from the surface into a fairly flat topped arch by their inertia.

Ocean spanning because it would be !!Fun!! if one came apart over any sort of inhabitated continent.

[McTraveller]

I still like the railguns up the side of various mountain chain ideas. Long, straight, and you can get them kind of close to equatorial to get the free 400-or-so-m/s free velocity in the direction of Earth's rotation.  The high Himalayan mountains are nice and high and in rarified air, but are all about 30 degrees north.  So if you can tolerate that kind of orbital inclination, the Himalayas are a good choice.  If you need equatorial you could try Kilimanjaro, although that is a volcano...

Railguns are also nice because you don't have to worry about Isp limitations of rockets.

[Max™]

A Launch Loop is like that but replacing the mountain with so much gun part of it swells and rises up so it stands free from the surface, erect and majestic, throbbing with barely restrained potential as it beckons the bold to climb atop it and hang on for an out of this world ride with an explosive finish!

[ChairmanPoo]

Do you people think Elon Musk is musky?

[Max™]

You're thinking of Elon Muskrat, who is ironically a ferret and oh my god what have I just made?

[Trekkin]

Railguns are also nice because you don't have to worry about Isp limitations of rockets.

You do need to worry about the impulse, though, and consequent aerodynamic forces on the projectile. Rockets have the advantage of traveling faster through thinner air, but railguns must do exactly the opposite, and that would demand even more shielding on the projectile than we currently add for reentry. And, of course, it's not possible to ship anything living.

[Hanslanda]

Ptw cuz !!SCIENCE!!

[Egan_BW]

And, of course, it's not possible to ship anything living.

...What if we pack them really good?