Space Solar Power

[93143]

Did you read the article? A Solaren executive is quoted as saying four or five launches of 25 tons each would do it, with automated docking on-orbit. If you're going to claim this estimate is unrealistic you should have a reason beyond just "I said so". They claim they have a "revolutionary" design, and for that number of EELV launches to result in that quantity of installed power, they'd better be right, but you haven't shown any indication that you actually have good reason to believe they aren't.

[MSimon]

Did you read the article? A Solaren executive is quoted as saying four or five launches of 25 tons each would do it, with automated docking on-orbit. If you're going to claim this estimate is unrealistic you should have a reason beyond just "I said so". They claim they have a "revolutionary" design, and for that number of EELV launches to result in that quantity of installed power, they'd better be right, but you haven't shown any indication that you actually have good reason to believe they aren't.

If they were a real business they should have disclosed how they intend to accomplish this revolution. Otherwise it is just another blue sky job.

After all we do have the outlines (if not the details) of how a BFR will work. Where does Solaren explain how they will accomplish their magic?

And how about a few technical details of how they plan to handle power reception? Thermal might not be bad. Except for the Carnot hit.

[93143]

I'm not saying I think it's going to work. I have insufficient information (and, to be honest, motivation) to form an opinion, so I have no opinion.

I'm just taking exception to kurt9's unsupported assertion that 25 mT launch capacity is not sufficient, when Solaren has specifically stated that it is.

[Betruger]

I'm pretty sure I saw some link, somewhere on the net, with at least some of the details.. I can't recall where though.
http://hobbyspace.com/nucleus/?itemid=11847
This is all I could trace my way back to.

[KitemanSA]

Thats exactly the point. We need ~100 launches a year total for the whole world. Not hundreds a day. That includes the launches of the world wide military. Yeah, they are all going to use the same launch system. There just is not a market for a system like that.

Right, as long as things stay the same. But the SPS folks are proposing (what was that, 4?) 25Mg shots to launch this thing. And if successful, they will probably need to launch 100,000 of them? (100Mw per with a world desired capacity of 10+ Terawatts) With a ram accelerator that has a capacity of maybe 25kg a shot, that would be 4 hundred MILLION shots. Different scale all together. But as I said to begin with, I prefer the KITE-HASTOL launch combo.

[Soylent]

There's the small problem of $11 000/kg costs of putting anything in geostationary orbit.

And there's of course the pesky need for a ~1 km diameter 2.4 GHz antenna in orbit. The rectenna on Earth would need to be about ~10 km; you could make it smaller but then the transmitting antenna in orbit would have to be larger. This is true whether you want to transmit 1 W or 100 GW; it's diffraction limited and if you want tolerable efficiency that's how big it needs to be.

The pattern of the radiation is an airy disk and the "lobes" will extend quite far outside of the rectenna. Since any kind of electromagnetic radiation except for visible light is "evil" and must be tightly regulated whether ionizing or not you're going to have to set aside a good 10-20 km border around the antenna or you'll be tied up in litigation forever. When you're done it will be about the size of the Chernobyl exclusion zone.

[TallDave]

It's a shame no one developed Sea Dragon...

Sigh. I remember reading about that one... when I was a kid. And it was old then.

500mT, that would have been nice.

[MSimon]

There's the small problem of $11 000/kg costs of putting anything in geostationary orbit.

And there's of course the pesky need for a ~1 km diameter 2.4 GHz antenna in orbit. The rectenna on Earth would need to be about ~10 km; you could make it smaller but then the transmitting antenna in orbit would have to be larger. This is true whether you want to transmit 1 W or 100 GW; it's diffraction limited and if you want tolerable efficiency that's how big it needs to be.

The pattern of the radiation is an airy disk and the "lobes" will extend quite far outside of the rectenna. Since any kind of electromagnetic radiation except for visible light is "evil" and must be tightly regulated whether ionizing or not you're going to have to set aside a good 10-20 km border around the antenna or you'll be tied up in litigation forever. When you're done it will be about the size of the Chernobyl exclusion zone.

Those rectennas are going to need a LOT of diodes at 1 mW each. About 1E11 of them for 100 MW. Assume 1 mm sq of silicon for each. That is about 1E6 300mm silicon wafers. That is roughly 1% of world wide yearly 300 mm wafer production. And then there is the factory required to turn all that silicon into rectennas. They have to turn them out at the rate of 2 million an hour 24/7 365 for 5 1/2 years. And then ramp that up if they are going to get power in the GW range. To keep costs reasonable they have to be able to make the rectennas plus diodes for .1 cent per mW or less. Preferably much less. To get 1 nuke plant equivalent a year they have to produce rectennas at 50X the above rate.

I'd love to see the plans for the rectenna factory. In fact I'd love to see the cost allocations for the whole plan.

[KitemanSA]

There's the small problem of $11 000/kg costs of putting anything in geostationary orbit.

Applying current costs to future endeavors of majorly diiferent situations is a mug's game.

Different assumptions (many copies of Gigawatt satellites) will eventually lead to different processes and different cost structures. The ENERGY cost to geosync is about $1/kg. Anything above that is waste or profit.

[D Tibbets]

There's the small problem of $11 000/kg costs of putting anything in geostationary orbit.

Applying current costs to future endeavors of majorly diiferent situations is a mug's game.

Different assumptions (many copies of Gigawatt satellites) will eventually lead to different processes and different cost structures. The ENERGY cost to geosync is about $1/kg. Anything above that is waste or profit.

I'll assume you are basing your cost on a rail gun that consumes $1 per kg to accelerate a payload to ~ 15,000 MPH (needed to reach GEO altitude on a ballistic corse?). Ignoring the cost to build and maintain the rail gun, the paylod would be in a GE transfer orbit, not a circular GEO. The paragee might be 35,000 km but the apogee would be the ground (or do I have that reversed?). To avoid the fate of sounding rockets, ICBM,s etc. the payload would have to have an engine to begin significant circularizing of the orbit within the first orbit so that the payload does not reenter the atmosphere. This would preclude the use of high efficiency, but low thrust ion engins. By aiming the rail gun at as shallow of an angle as possible, the thrust needed to circularize would be minimized, but still significant thrust would have to be aviable within that first orbit. And launching at a shallow angle would mean the payload ploughs through the dense atmosphere for a longer time, resulting in alot of decellerating and heating friction. A robust protective shroud would be needed. Launching from the equatorial Andes mountains would help some (are there any other high mountains on the equater?).

What all this means is that the cost of the electricity to power the rail gun is only a drop in the bucket compared to the total launch costs.

Dan Tibbets

[MSimon]

This may be a peaceful application for Brilliant Pebble Engines.

[KitemanSA]

What all this means is that the cost of the electricity to power the rail gun is only a drop in the bucket compared to the total launch costs.

To many assumptions. delta V to geosync on the order of 10km/sec. At $0.07/kwH this comes out to ~$1 of kinetic energy.

Which is my point, there is a LOT of waste going on here. Engineering, in general, is the process of removing waste; doing things better-faster-cheaper. So assuming $11,000/kg to geosync for assessing the long term economic viability of SPS is to assume all engineers have instantly stopped thinking. Don't know about you, but I don't plan to stop.

[MSimon]

What all this means is that the cost of the electricity to power the rail gun is only a drop in the bucket compared to the total launch costs.

To many assumptions. delta V to geosync on the order of 10km/sec. At $0.07/kwH this comes out to ~$1 of kinetic energy.

Which is my point, there is a LOT of waste going on here. Engineering, in general, is the process of removing waste; doing things better-faster-cheaper. So assuming $11,000/kg to geosync for assessing the long term economic viability of SPS is to assume all engineers have instantly stopped thinking. Don't know about you, but I don't plan to stop. :D

There is a lot of thinking between $11,000 and $1.

[Soylent]

Applying current costs to future endeavors of majorly diiferent situations is a mug's game.

You don't understand, they want to start working as soon as they get funding and plan to have it ready by 2016. Like it or not it will cost on the order of $11 000 per kg and they will be using plane old chemical rockets.

[KitemanSA]

Applying current costs to future endeavors of majorly diiferent situations is a mug's game.

You don't understand, they want to start working as soon as they get funding and plan to have it ready by 2016. Like it or not it will cost on the order of $11 000 per kg and they will be using plane old chemical rockets.

Mayhaps I do understand. Despite some of the publicity, I suspect they will lose a bit of money on the first one or two (or dozen). Then they will start SERIOUSLY reducing those costs and shazaam, it MAY actually become commercially viable.

A most exciting proposition, no?