Siber wrote:Personally, I'd rather put my bet on Orion or even just massed chemical launches than an elevator. Yes, we've made good strides lately, but we're still very far from being able to make that cable, and there's no way of knowing how long it'll before we can, if we ever can. Orion was considered feasible,if challenging, with 50s tech, if the money and will were there I'd expect we could get it working very fast. For that matter, if the money and will were there you could get a lot done by simply ramping up existing chemical rocket development and production as fast as possible. Probably not anywhere fast enough to evacuate a significant fraction of living humans, but I'd be shocked if it wasn't enough to preserve the species in 70 years.
The reason I'm more in favor of a space elevator than Orion or chemical launches is because of how much extra construction they require, especially in the case of Orion. Getting a ship into and out of our atmosphere has historically always been the most dangerous part of spaceflight. Just ask
Challenger and
Columbia. To perform a terrestrial Orion launch, you need a ship that can not only survive the stress of launch but also survive its own deadly exhaust (it is sitting on a nuke, after all). That's a lot of over-engineering that could be bypassed if we had an elevator. Still, the usefulness of Orion vehicles as heavy-lifters should never be underestimated.
Since we're probably going to want those carbon nanotubes to build our Generation Ships anyway, a feasibility study wouldn't hurt our escape effort much.
Absalom wrote:The 70-year answer to space elevators, I think, is to think differently: instead of a space elevator, use a sky-hook. It wouldn't be quite as convenient, but it would be easier to implement, and quasi- or semi-conventional aircraft could provide the initial launch-bootstrap. If one felt like being thorough, then the lighter-than-air waystation idea could be used in conjunction, thereby allowing a specialized upper-atmosphere aircraft to rondevou with the sky-hook.
I agree that the Skyhook or a
Launch Loop would be a good compromise. Reusable or disposable vehicles could get resources into space without the expense of building a one-way vehicle strong enough to get millions of tons into space and still survive the trip.
Besides, who says we can't use multiple methods simultaneously? A space elevator, Skyhook, or loop could be used for lighter materials, while a smaller number of Orion launch vehicles could take everything that can't be easily hooked into space. We can have multiple chemical launches, Orion launches, and elevator/hook/loops payloads going up all at the same time.
This is Armageddon, I think we'd be trying everything short of flapping our arms and wishing to get as many people and materials into space as possible.
Absalom wrote:I haven't done studies on it or anything, but I expect that the first step would be to ensure that the exterior is sufficiently simple that there's little to break. You'll want docking access of course, but if you build your docking structure correctly then both dock and vehicles will be completely shielded from exterior line-of-site, and thus from most impactors. Two slowly rotating and one fixed "gates" might be of utility in this, with the "open" portions only intersecting two at a time, and never three at a time. From there, presumably it would be a matter of dividing and conquer (e.g. the pressure hull should be double-or-more hulled to reduce or eliminate atmospheric losses, and should ideally be filled with inert gasses, to reduce corrosion: non-pressure interior hulls can thus deal with e.g. corrosive atmospheres). Also, it would have to be designed with the assumption that maintenance will be performed: because it wil, and without the benefit of an external docking facility.
I'm less worried about interstellar impacts and more about routine breakdowns. Apollo 13's famous oxygen tank rupture was caused by damaged Teflon insulation. Soyus 11 was lost to a ventilation valve that got knocked open. If one of our extrasolar vehicles has one of those problems (or any of a hundred other mechanical issues that are sure to pop up in a decades/centuries long voyage), we can't order a new part sent or try an emergency landing. We need these things to be as fail-proof as humanly possible.
Grayhome wrote:Excellent link Joestej, thank you for it.
Thank you! Atomic Rockets has been my go-to for any Hard Scifi facts I need in my writing. The tone is casual enough that you don't need a physics degree to understand how something works, but they've got the numbers to prove what they say.
Incidentally they've already taken a look at the problem of moving large payloads to orbit, and have a
whole page dedicated to different launch methods.
From what they provide, it seems that the Lofstrom loop I mentioned previously is the cheapest method, per kg. HOWEVER, they agree with Siber in that, if you don't care about the planet you live on (we don't, provided enough people survive to make it on the extra-solar ships), Orion is hands down the best way to get lots of stuff into space fast. A 1080 bomb Super Orion can lift more in one launch than a Lofstrom loop can in a year. It can almost boost an entire L5 colony into orbit BY ITSELF. They couldn't calculate the cost per kg on the Orions because no one has ever figured out how much one of those suckers would cost to build, but with the End of the World coming we only care about cost to figure out how many we can make before Last Call.