Category Archives: Space

Business, Economics, Space, Technology and Society

How Do The Numbers Work?

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Sorry, but I just can’t buy this:

PG&E is pledging to buy the power at an agreed-upon rate, comparable to the rate specified in other agreements for renewable-energy purchases, company spokesman Jonathan Marshall said. Neither PG&E nor Solaren would say what that rate was, due to the proprietary nature of the agreement. However, Marshall emphasized that PG&E would make no up-front investment in Solaren’s venture.

“We’ve been very careful not to bear risk in this,” Marshall told msnbc.com.

Smart move.

Solaren’s chief executive officer, Gary Spirnak, said the project would be the first real-world application of space solar power, a technology that has been talked about for decades but never turned into reality.

“While a system of this scale and exact configuration has not been built, the underlying technology is very mature and is based on communications satellite technology,” he said in a Q&A posted by PG&E. A study drawn up for the Pentagon came to a similar conclusion in 2007. However, that study also said the cost of satellite-beamed power would likely be significantly higher than market rates, at least at first.

In contrast, Spirnak said Solaren’s system would be “competitive both in terms of performance and cost with other sources of baseload power generation.”

I just can’t see how. Unless there are going to be many satellites, the system has to be in GEO to provide baseload power to any given region on earth. They talk about putting up a 200 MW system with “four or five” “heavy lift” launches (where this is apparently defined as 25 tons).

Suppose the conversion efficiency of the cells is a generous 30%, the DC-MW conversion is 90%, the transmission efficiency is 90% and the MW-AC conversion efficiency is 90% (generous numbers all, I think). That gives an overall efficiency of 22% from sunlight to the grid. The solar constant in space is 1.4kW/m2, so that means you need 650,000 square meters of panels to deliver 200 MW to the grid. Suppose you can build the cells (including necessary structure to maintain stiffness) for half a kilo per square meter. That means that just for the solar panels alone, you have a payload of 325 metric tons. Generously assuming that their payload of 25 tons is to GEO (if it’s to LEO, it’s probably less than ten tons in GEO), that would require over a dozen launches for the solar panels alone.

That doesn’t include the mass of the conversion electronics, basic satellite housekeeping systems (attitude control, etc.) and the transmitting antenna, which has to be huge to get that much power that distance at a safe power density.

So even ignoring the other issues (e.g. regulatory, safety studies, etc.) that Clark mentions, I think this is completely bogus until I see their numbers. And probably even then.

Political Commentary, Space

Getting It Half Right

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Yes, Congress is a problem for NASA. But not because it doesn’t give it enough money. As Clark notes, NASA has plenty of money, if it wanted to, and were allowed to spend it sensibly. The problem with Congress it that it won’t let NASA do so, even if it wanted to. It will always be more important to Congress where the money is spent than how it is spent, which is why government space programs are so cost ineffective (and that was true going all the way back to Apollo). Apollo succeeded because it did have huge bales of cash thrown at it, but it certainly wasn’t politically sustainable or affordable, any more than redoing it will be.

History, Media Criticism, Political Commentary, Space

The Beginning Of The Myth

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I missed noting it yesterday, but it was the fiftieth anniversary of the announcement of the Mercury 7. It set the pattern for the mythology of the NASA astronaut (with two minor variations — the first in the sixties when it was no longer necessary to be a test pilot, and in the late seventies, when women were allowed into the club). I may have more thoughts later, but to me, it was one of the key events that led us off on a very wrong path that has resulted in the space quagmire we’re in to this day.

Science And Society, Space, Technology and Society

Geoengineering

7 Comments

I have to say that I’m (slightly) encouraged that the new science advisor is willing to consider planetary modification as a solution to global warming, in the event that it actually turns out to be a problem bigger than the current preferred cure. But I think that Mickey Kaus infers too much, unless he’s seen more specific proposals than appear in the WSJ piece:

If shooting particles in the air can semipermanently change the climate of the entire planet … well, in the hands of well-meaning people it would be a risky, last-ditch policy to combat global warming. In the hands of less benevolent people it could become a heavy duty terrorist weapon, no? … If you have the missiles, is it that much easier to develop nukes?

Well, first of all, having missiles doesn’t help at all with developing nukes. They are entirely independent technologies. It might help in delivering nukes, if (as I pointed out in the New York Times) you can build the nukes small enough to fit on the missiles, and if you can also build an entry vehicle that can deliver it to a desired target (and yes, I know that the guidance doesn’t have to be that precise to simply take out a city, as opposed to a silo).

But even more to the point, nowhere did I see the suggestion that it would be done with “missiles.” I had an argument with an idiot at Free Republic a year or two ago when this notion (putting particulates in the upper atmosphere to block the sun) came up. He pooh poohed it, on the basis that rockets cost far too much, and made a stupidly ridiculous cost estimate based on Titans (which no longer even exist).

But if this were to be done, it wouldn’t use missiles. As I point out in the previous linked post, this would be an excellent market for reusable suborbital transports. And if you’re worried about suborbital transports as terrorist or rogue-nation weapons, you don’t understand their nature (at least for the short distances that satisfy either tourism or seeding particulates in the upper atmosphere). They would actually be less useful than aircraft, as a result of their limited range and payload.