There’s an interesting piece at the Journal today on “tomorrow’s winners” in new technologies. Several of them will be familiar to regular readers of this site:
Space Travel and Habitation
“Commercialized space travel will see a lot of innovation,” says Jeffrey Baumgartner, founder of the JPB innovation consultancy.
“Much of it will be incremental in nature, but the result—low-cost, easy travel to space and potential bases on the moon and, in the longer term, Mars—will involve substantial innovation.”
Some firms to watch, says Mr. Baumgartner, are Space Exploration Technologies Corp., known as SpaceX, Virgin Galactic LLC and Bigelow Aerospace LLC.
Human habitation in space so far has taken place in rigid vehicles like the International Space Station. Bigelow, based in North Las Vegas, Nev., is developing inflatable modules that should be easier and cheaper to launch. Bigelow already is orbiting two unmanned, expandable prototypes and says it is planning assembly of four new spacecraft by 2015.
“The key here,” says Mr. Baumgartner, “is that aeronautics is leaving government control and being taken over by industry, where cost-cutting and profitability, rather than contractors milking the state for as much as they can get, will lead to a lot of innovation, affordability and efficiency.”
Heavy-Lift Launching
A critical obstacle to any sort of space-based future is getting some rather sizable objects beyond the reach of the Earth’s gravity.
But Langdon Morris, a partner with the InnovationLabs LLC consulting firm, notes that while state-invested companies in the U.S., Russia and Europe have developed “heavy lift” launch capabilities, one private firm is moving to surpass them all in terms of payload capacity—an innovation that could slash launch prices and make larger payloads commercially viable.
SpaceX, of Hawthorne, Calif., says it hopes for a 2013 launch of its Falcon 9 Heavy rocket, which is designed to carry payloads of up to 70,000 pounds into low Earth orbit, about one-third more than the Space Shuttle, which is the largest-capacity launch vehicle now in operation.
“Cost-effective heavy-lift launch will enable new space commerce industries,” says Mr. Morris.
Space-Based Solar Power
“Once heavy-lift launch is solved, space solar power will be close behind,” says Mr. Morris. “Space solar power could transform the Earth’s economy.”
The idea is for satellites in geostationary orbit to collect the sun’s energy and convert it into radio waves for transmission to surface stations, where it will be converted into electricity for local power grids.
Mr. Morris thinks there are several companies that could achieve this.
One is Manhattan Beach, Calif.-based Solaren Corp., which last year reached an agreement to sell 200 megawatts of electricity a year to California’s largest utility, Pacific Gas & Electric Co., for 15 years, starting in 2016. Solaren says it plans to test key systems and deployments in space in 2014, and launch its Space Solar Power Plant into geostationary orbit in 2016.
A competitor, Switzerland-based Space Energy Group, says it hopes to launch a test satellite within three years, assuming it gets expected funding.
Emphasis mine. I have higher hopes for the space transportation companies that the power satelliters, but more power to all of them. So to speak.
I worked with space solar power for a few years, and I just don’t see them making that timeline for a 200MW system. Not to mention “200MW of electricty a year” is confusing. Wattage is a rate of energy use. Are they on contract to sell 200MW for an entire year? That is a lot of Joules!
There are still so many engineering and architecture questions that need to be answered. An array sizeable enough to produce 200MW is going to be huge, even with the state of the art in space-capable solar cells. Or are they just redirecting sunlight to the ground with a huge mirror (which would still be huge as you’ll only get to ~96% for such wideband reflectivity, not to mention the difficulties of creating a reflective optic that big)? I doubt they could fit the bus + all that array in any launcher available today. Are they constructing on orbit via multiple launches (I’ll applaud the effort but 2016 seems a little rosy). The structure is going to be something we’ve never seen before in space to accomplish all this. Are they flying sun-syn to maximize solar collection? Going to need some huge capacitors and a powerful ability to dump that energy to the ground when you get your pass over CA. If you’re flying GEO to minimize power storage and distribution (not to mention receiving) needs, your structure will have some issues maintaining the pintpoint accuracy your downlink will need in order to not waste energy (and money) by missing your target (not to mention angering the locals), while you have these enormous solar arrays flopping about. With a currently not-existing 40% solar cell (which would be a dream in 6 years) you’d still need over a 0.36 km^2 surface area for your array. You could use collectors to up the efficiency of the cells a bit, but you’re still going to need surface area 1000s of times larger than anything that has ever been built in space. Even if your structure and solar cells were a fantastical 1kg per m^2 of array, you’d still be lifting 366Mg to your intended orbit. If SpaceX can get you to say $600/kg to GEO (which I dont know if they can reach) with their F9 heavy you’re still looking at half a trillion dollars just to launch the array (not to mention the bus to manage all this) and 36+ launches. What is your energy sunk-cost getting all this stuff to orbit (this is REALLY a lot of Joules) – how fast will this energy debt get paid off? Quicker than the lifetime on your electronics and solar cells? With all the incredible accuracy and power you’ll need to pump this energy to the ground, what’s to keep X, Y, and Z countries from considering you a weapon? Radio waves are destructive at sufficient power – just ask the birds that fly in front of our early-warning radar stations.
I hope they have some great ideas (that don’t involve taxpayer slavery) to make it work, but it sounds like serious overpromising to me.
For large scale space based solar power, I just can’t see photovoltaics being used. Solar Thermal makes a lot more sense – a 3 Kelvin shadow drives the Carnot limit up past 99% for a sunlit side of 300 Kelvin or more; any hotter and you just get more nines.
The bulk of the mass of a solar thermal satellite would be heat exchangers, turbines, generators, radiators, flywheels/gyroscopes, and a microwave antenna, and the bulk of the surface area would be a simple reflector, such as aluminized Mylar with inflatable tubes for structural support. One or two launches for your central structure, and a few more launches for your reflector, and you’re in business.
Losses would be in working fluid viscosity, mechanical losses, conversion loss from electricity to microwave, microwave transmission losses, conversion losses at the rectenna, and then the usual transmission losses in the grid.* Being generous I’d estimate a total of 50% efficiency in power delivered to the grid. So, let’s see how big the reflector array would have to be if solar thermal was 10% efficient in delivering 200MW to the grid:
Solar insolation @ GEO: ~1370W/(m^2)
200MW/ 10% efficiency = 2GW
2e9/1370 ~1.46 million square meters
let’s say a pessimistic 100g/(m^2) –> 146 tonnes ~ 161 tons
If the heat exchangers and turbines and generators and antenna and so forth mass 40 tons, then you’re looking at 210 tons to GEO. And that’s being pessimistic; an increase in efficiency from 10% to 50% brings the reflector mass down to 32 tons, and also reducing the mass of the reflector to 33g/m^2 brings the reflector down to 11 tons. There’s lots of tradeoffs available.
It’s doable.
(*If the transmitting antenna is large enough, the rectennae can be small enough to fit in a cell phone or car, eliminating the need for a grid altogether. However that would be an enormous antenna — maybe two satellites beaming at a large metro area could form a very large virtual antenna, like the very large baseline array?)