With apologies to all, I am a "techie," however I play the stockmarket as a passionate hobby. I do believe that the technology can drive the fundamentals, and historically has.
I would like to make one last comment on fuel (and I promise I will shut up about it after that). By the way, if anybody wants to check my numbers (and please do because sometimes I make misteaks), you can get the equations in any orbital dynamics book and work thru the numbers. Fuel consumption is based on changing a velocity and maintaining a 3-axis stabilized satellite in LEO takes about 15 to 75 m/s per year. This equates to about 0.5 Kg of fuel. To change altitude from a typical drop off point to get acceleration into a plane takes about 3600 to 4000 m/s which equates to about 30 Kg of fuel. This obviously varies with the altitude, and I just did this for an example at 800 Km from about 375 Km. Typically, less than 10% of the propellant mass is used for attitude control.
Moving on to the electronics, from what I have read about Iridium, I understand that they can program their computers, so software upgrades are very possible. Obviously they cannot change fundamentals that are hardware limited, like the number of tuners which ultimately limits capacity. However, while G* does not have the same limitations, they also have limitations in hardware which ultimately limits capacity. But my guess would be that what limits these systems in capacity more than anything else is the amount of spectrum they have allocated. I am sure that bandwidth drove a lot of design decisions for both systems.
One other point, there are a lot of advantages to CDMA in terrestrial systems. Not all of these advantages can be realized when you take that system in to space. For example, power control in a terrestrial system is based on a few microseconds of time passing between the user and the base station, while in space this is in the tens of milliseconds. Response times and power control do impact capacity and that is one of the reasons I think the G* capacity values are overstated. Taking this to the next level, lower capacity means higher prices and while I do not think G* costs are as high as Iridium's, I am not as wildly optimistic about their ability to sell cheap minutes and make a profit as some.
These are just my opinions and I welcome criticism and debate.
CSM |
