Another mag lev approach

Orbital assembly may be better served by multiple deliveries.
One big delivery (OBD) to a construction site does not make projects more economical. The OBD becomes a warehouse in space with an ever shifting center of gravity - the load shifts. Modules help this a bit better, but for ISS the initial lack of experience on adding modules and shortage of astroworkers required a one-at-a-time approach instead of OBD if only for safety reasons.
OBD is always an option. However, for multiple deliveries other methods such as just-in-time (JIT) delivery to space is complementary to launch-on-demand (LOD). Both methods are needed if only for emergencies. Even for an OBD, there may be *something required* missing in the module or needing upgrading quickly. Or damage goods that need to be replaced. Perhaps even an emergency shield craft during peak solar periods.
100s of launches will require the FAA, not NASA. FAA handles hundreds of thousands of flights annually (over 100 per day at many airports). If NASA were to staff a control center for every plane like they do manned rockets, there would be tens of millions of folks just watching the plane not only in flight but during loading and unloading. NASA is better at insight and oversight up to 100, and the big stuff.
So OBD may be where NASA can really apply it's skill sets. However, as we have seen in the past 100 years with airplanes, commercial flights to space will need other groups to manage the logistics and traffic.
Besides, NASA has it's hands full with the rest of the universe.
D

Cc: Space Settlers maillist

While launching a lot of small payloads might help the economics on the launch side, I wonder how it would affect the economics in orbit.

If you are building something up there, in the beginning it all has to be lifted, and the smaller the launch payload the more parts that have to be joined in orbit. The larger the payload, the smaller the number of parts that need to be joined.

Consider the ISS there will have been 40 assembly flights by the time it's finished. So far that's involved 159 spacewalks for more than 1000 hours EVA.

If instead of 40 flights there had been 400 or 1000 flights (depending on how small a payload you want to go to) that would have increased the amount of on orbit construction required and most likely have increased the number of hours EVA significantly. How much more expensive and time consuming would that have made construction ?

Alternatively if a launcher the size of the Sea Dragon had ever been made the ISS could have been launched in one flight (albeit in a different configuration) which should have simplified construction and made it less time consuming.

There is not much point in making launch cheap and frequent, if you are going to end up making construction expensive and time consuming. It should be possible to work out some kind of balance between launch and orbital construction to keep the costs and construction time at a reasonable level.

It should be considered a necessary consideration if wanting to build something the size of a Satellite Solar Power Station, or a space hotel, or a mining facility, all of which will be much larger than the ISS.

B

On 13/03/2012 05:42, Combs, Mike wrote: Any kind of electromagnetic launcher ought to have advantages over rockets. That said, Ill have to admit that since I wrote The Bridge to Space back in 1995 Ive heard an interesting assertion made in regard to the advantages of EM launchers over rockets. It was pointed out that most economic analyses of EM launchers assume an extraordinary launch rate (typically many per day). The question is then asked how much more economical rocket launches would be if we launched at the rate of several a day every day. Rand Simberg sometimes talks of an analysis he participated in where they examined just about every technology imaginable, and found that the affect the different technologies had was minor compared to the affect of launch rate. In other words, a technology far from optimal launching at a rate of several times a day would undersell a much more advanced technology launching at once a month. It was all about the launch rate. So EM launchers may or may not be the panacea for reducing launch costs that some might have thought. Star Trams superconductive cables are to provide lift to the far end of the launcher, which permanently resides in the upper atmosphere. Electromagnetic repulsion between superconducting cables on the ground and attached to the launch tube suspends the tube against the pull of gravity.
Regards,

Mike Combs