Hey Mike, have you heard of Star Tram? They have a variation of your balloon supported maglev, w/o the balloons,,,
http://www.startram.com/resources

> *Hey Mike, have you heard of Star Tram? They have a variation of your
> balloon supported maglev, w/o the balloons,,,*
> *
> *http://www.startram.com/resources

Yes, I was powerfully reminded of Sky Bridge when I saw this proposal. Never would have envisioned that electromagnetic repulsion could be that effective over a distance of tens of miles. Of course the rub there is obtaining many miles of superconductive cable economically.
Regards,

> I've now skimmed the paper... I intend to read it more carefully when I
> get the chance, but so far, the most questionable part to me would be
> the "MHD window".

Please explain to me as I haven't understoodcompletely.What's the advantage of this Star Tram over other systems? And what are the superconductive cables for? Maglev?
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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
The launch rate would depend on power available and launch to launch time.Just the time in preparing a launch tube for the next launch could be considerable.
So multiple launch tubes need to be part of the facility design solution. Facilities can be built in phases but in this case, any drilling would increase the risk of a launch especially for humans and other vertebrates.
Constructing a number of tubes might amortize the cost further.Two tubes at a time would ensure a backup.One could envision multiple sites with at least two tubes each. Maintenance alone would require multiple sites with multiple tubes.
From the business or consumer side, the ticket cost will depend on the costs of the design/build of launch facilities, operations/maintenance, and mission (destination/path/time in space). Since the ground facilities will be the greatest cost without regard to specific mission, that is where any business plan for space needs to focus. The ground facilities will require an international airport (50 to 100 miles of surface land with subway tunnels to the loading zone.
Dollars per pound tries to reduce all the various costs to one figure. In reality, it's the dollars per pound per mission. An up and back mission to LEO in one day is quite different than a two week orbital mission. The rough estimate begins with the weight of the humans. Add to that ten times (10x) the weight for food and air per week.
Given the launch rate and the facility requirements, whole cities would need to be built just to house the workers and guests.
David

Thanks for the explanation.
Revisa mi Blog!: http://lacuevadellobo.blogspot.com/

As fas as building a city for the workers,,,perhaps you're not familiar with the "city" we built in the Arabian desert when we were constructing the natural gas plant at Jubail Berri. It was mostly 2 room prefabs with a shared bathroom between, a mess hall, library, pool room,,,all from prefabs and,,,very cheap,,,
I don't see why an airport would require a hundred sq miles,,,the refinery at Ras Tanura, Saudi Arabia was built mainly from sea transport and,,,a single airstrip in Dhahran.
We don't have to build cities to service this system, at least, not initially, though I expect as business picked up, those amenities would follow of their own accord. In other words, THAT expense is not a part of the start up infrastructure costs,,,
Gary Ansorge

Saudi Arabia has the largest commercial airport in the world at 484 miles. The largest landlocked spaceport is White Sands Missile Range at 3200 square miles.
The largest US aiport is Denver International, a mere 53 square miles. Denver has 6 runways in a pinwheel configuration. The initial construction took over 10,000 workers. When DIA opened, 32 million passengers went thru the gates in one year. The airport is building towards 110 million passengers per year.
So if the airport trend continues, a spaceport will be over 1,000 square miles and perhaps as much as 10,000 square miles (100 miles on a side. The spaceport will probably be at the center of 4 to 16 small cities around the edge which have their own international airports and perhaps launch tube sets for suborbital flights. These cities and the spaceport will require infrastructure such as water, electricity, natural gas, gasoline, waste, sewer and telecommunications.
Most likely, there will be a suborbital facility separate from the orbit and beyond facilities. National, international and interplanetary concourses will have their own security, customs, and decontamination efforts. Shopping and shipping will be in the common area along with the food courts and restaurants. Wifi will be everywhere...
It's all about people...It's not just about the size it takes to launch a vehicle or passenger terminals. How many people will use the facility over the years?Someone has to feed the folks.People need to shop ...and perhaps play while waiting.For a spaceport...every corporation will want to have a presence in the immediate area. Every shipper will want tohave access. Every government will want some sort of office if not a consulate.
The host government will consider it a valued asset and have security from the local Sheriff to the airport police and TSA to perhaps a full military presence. After all, the military will want separate launch tubes. Have them build the tubes first, and as more tubes are built for them, convert the old ones to regular use.
I wonder what the decibel level will be for a vehicle leaving the tube? Probably will need a noise reducing system that can survive the high use overpressure of a Mach launch transition.
David

Joe, the MHD window is just one proposal. A mylar film caping the tube end with a quick closing mechanical seal some distance before that could limit any atmospheric invasion into the tube.
GAry Ansorge

Only the payload launchers have a problem with sonic booms, since they launch at ground level. The design for a human launcher is the biggie and ejects the vehicle at 60,000 feet, with little sonic boom intensity,,,
Gary Ansorge

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.

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