Enormous orbiting solar raygun power plants touted
Trusty scientifiction staple gets another outing
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Many years ago, in Galaxy magazine, Jerry Pournelle devoted his A Step Farther Out column to describing how satellites could be used to harvest solar energy on a scale impossible underneath Earth’s atmosphere.
The idea never really went away, but it’s been mostly out of the spotlight. Now, Reuters is reporting a study by the International Academy of Astronautics (IAA) which touts orbital power as being technically feasible.
NASA’s former head of concepts John Mankins (now head of Artemis Innovation Management Solutions of California) is quoted as saying “solar power derived from space could play a tremendously important role in meeting the global need for energy during the 21st century” (“could” simultaneously meaning “if someone finds the money”, “if the engineering is as feasible as we think it is”, “if we don’t have a disaster that fries someone Earth-side”, and “if some whacko protest movement doesn’t run up a handy conspiracy theory to bring an end to the whole idea” - El Reg).
Certainly the engineering challenges would be formidable: power would be transferred from satellites to Earth as very high-powered microwave signals to be captured by a network of large antennas.
The satellites, at around 1km across, would be too large to be launched in one shot, so they would need to be assembled in space (the IAA report recommends using low-cost reusable launchers in the long term, with part of the budget for this idea to be spent on spaceship development). And as has been clear ever since Pournelle discussed the idea, control over the satellites and the power-carrying beam would need to be very precise.
Mankins told Reuters a moderate scale demonstration could be accomplished “for tens of billions of dollars less than previously projected”.
The advantages are that in addition to getting much more sunlight than is available under the atmosphere, the “solar satellites” could – space junk permitting – be positioned to operate 24 hours a day.
The 248-page study took two years to complete. ®
COMMENTS
Rail guns?
| "TBH I don't know why a giantic magnetic rail gun / catapult
| into space to shoot things up there hasnt been built yet."
To get into (and stay in) LEO, an object needs to be traveling at about 17,500 mph when it reaches its orbital slot.
A rocket gets there by starting off traveling slowly down where the air resistance (and hence friction) is heaviest and accelerates as it rises into less dense/less compressible/less friction-inducing atmosphere.
On the other hand, atmospheric friction and compression is used when decelerating out of orbit. This generates thousands of degrees of heat which needs to be dissipated/shielded against.
Now take your rail gun. Assuming as a starting point that it is long enough -- some number of miles maybe* -- that the acceleration to escape velocity doesn't pancake every structure in your launch vehicle and payload, there is still the issue that being at the bottom of a gravity well requires that your projectile be going at well OVER orbital speed when it leaves the muzzle.** Otherwise,just as with a thrown rock, gravity will start slowing it down as soon as the driving force is off. If it doesn't reach orbital height at orbital velocity -- just like that rock -- back to earth it falls.
So your railgun launcher has to -- slowly enough not to destroy the projectile -- accelerate it to something in the 20,000 mph range... at sea level... in order to still be at orbital velocity when it finally reaches its intended altitude... And once fired into flight, the projectile has to be sufficiently heat-resistant that it isn't instantly immolated by friction/compression-heated atmospheric values above anything that humankind has ever built. (Bear in mind that -- while, granted, its thermal protection had been compromised -- the temperatures and stresses that destroyed the shuttle Columbia happened when it was decelerating from the arbitrary "edge" of the atmosphere at 75 miles above sea level down to final breakup at about 40 miles up.)
...And you want to shoot your payload out of a cannon at HIGHER speeds than the Columbia was traveling, in atmosphere that is DENSER by a couple of orders of magnitude than she was traveling through, and hope to get it to orbit intact...?
Good luck with that.
A long-enough catapult might POSSIBLY be useful for accelerating something akin to a SCRAMjet to operational speed, which could then accelerate through much of the atmosphere before handing off to a rocket engine for orbital insertion, but a catapult to orbit setup without any other motive force...? SO not happening. And I see no way that a catapult/scramjet/rocket combination isn't going to be MORE complex and expensive than what we have now,
No, I'm afraid that (absent any completely new science like antigravity) until we get the first beanstalk built, rockets are pretty much going to be the only way into orbit.
--------------------
* The difficulty of building a miles-long, precision-engineered railgun in an utterly straight line tangent to your starting point on the surface of the earth (You can't just put a ski-jump at the end if you're launching something at Mach 27 or so) is left as an exercise for the reader.
** Ditto the effects of a Mach 27 sonic boom on surrounding organisms and structures (including your miles-long, precision-engineered etc. etc.).
>"they will be pushed by the solar wind out of their orbital positions"
Well, that's a big problem. If only this orbital power station had... I dunno... some source of power, that it could use to drive engines to maintain its orbit with?
Not this s--t again...
The problem isn't the death-rays-from-space, or the panel-turning-into-a-solar-sail: It's the insane cost of getting something into orbit and assembled. We already have large solar panels in space - They're on the ISS, and if you look at STS-115 it works out at half a billion USD for 70Kw.
It would be cheaper to get 1,400 Chinese people running on treadmills for 40 USD per day. Or suck down the FUD and build some nuclear reactors, already.
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