Wednesday, November 26, 2008

Sorting Out Engineering Reality

A recurring problem I have in my line of work is judging what’s “true” and what’s not. It’s not so much that I think people are lying to me about what’s going on in the space business, it’s just that I was too lazy in junior high, high school, and college to get myself a serious education in science, technology, engineering, and mathematics (STEM). This is a problem for me and, I fear, for many more Americans, as more and more of our nation’s future choices will be STEM-based. This is part of the reason I’m such a fan of
Darlene the Science Cheerleader: she’s a strong advocate for science education among the non-scientific masses, and gosh knows we all need it.

Now mind you, the space business has, as one of my previous employers put it, “plenty of engineers; what we need is a writer.” So that’s been my role: technical writer. I translate Engineerish into English. I’m able to do this without understanding the work 100% because I understand how words work. They aren’t paying me to understand it all. I do my level best, of course, to educate myself so that I do understand it. And I understand enough about political philosophy and policy to be an advocate.

Sometimes, however, it’s difficult to know which technologies, among the many I’ve supported over the past 8 years, stands a solid chance of succeeding. That leaves me the option of taking things on faith or getting myself a better education. The following narrative, then, is a review of the hot technologies space advocates support, how they’re supposed/claimed to work, and what the objections to them are. I can explain them clearly, as you’ll see, but I can’t for the life of me sort out all this.

Space Solar Power (SSP) / Solar Power Satellites (SPS) / Space-Based Solar Power (SBSP)
How It’s Supposed to Work
A solar power satellite is a large array of solar cells—say, a mile across—placed in orbit. Because it is above the atmosphere and in the sunlight for longer periods of time, the theory is that the SPS would collect more solar energy than ground-based solar. The energy collected from these solar cells would then be transmitted, projected, or beamed down (pick your verb) to a rectifying antenna (
rectenna) on the ground. The power would then go out from the rectenna to a nearby electrical grid. The potential output of such a system would be in the 1-10 gigawatt range.

The Arguments Against It

  • It’s too expensive to get the hardware into orbit.
  • Even if you could bring down launch costs, the operating costs would still not make SSP commercially competitive with any ground-based energy source, including ground-based solar.
  • Even if you could get the hardware up there cheaply and get it to provide power competitively, any usefully scaled SPS is too big to fit on any known launcher (except, maybe, Ares V).
  • Even if you could get the hardware up there cheaply and on a properly sized rocket, it wouldn’t work for the following reasons:
    --Beam attenuation; i.e., the microwave or laser transmitting power to the ground rectenna would lose too much energy to be worthwhile.
    --The SPS would be so big and so lightweight that solar radiation pressure alone would cause it to keep drifting along its orbit. This is how one powers solar sails, which are meant to travel.
    Even if you could get the hardware to work, it would never be accepted by the public because:
    o Environmental activists would go bonkers protesting it because it uses radiation as its primary output (even if that same radiation is also used to power ground-based solar cells).
    o Government environmental regulations would stifle the technology somehow, with or without encouragement from the environmental lobby.
    o “Someone could use it as a weapon.” (See the James Bond flick “
    Goldeneye” for a sample of what that might look like.)
    o It wouldn’t provide much more energy than ground-based solar power.

Fine. I would submit a bit of my own hardheaded criticism, if I may: All of these objections come before anyone has even tried to build, field, and test a single SPS. We should at least try the bloody thing before trashing it or dismissing it out of hand. The cynics and skeptics might be right, but I’d feel more confident of their verdict if they had hard data to back up their assertions.

Reusable Launch Vehicles (RLVs) / Single Stage To Orbit (SSTO) / Two Stage To Orbit (TSTO)
How It’s Supposed to Work
A Reusable Launch Vehicle (RLV) is just what it sounds like: a rocket for getting to space that you can fly more than once. An RLV is supposed to be completely reusable, operating like an aircraft. No stages are dropped into the ocean, the vehicle flies multiple times, and costs are thereby reduced through mass production and repeat flight cycles.
The Arguments Against It
NASA has spent a great deal of time and money trying to develop precursor technologies or actual RLVs for the last 20 years or so. The Space Shuttle system, designed in the early 1970s, is partially reusable. Its solid rocket boosters return to Earth by parachute and splash down into the ocean. The orbiter, which houses the crew and cargo, lifts off like a rocket, its fuel tank is discarded and dropped into the Indian Ocean, and the orbiter then completes its mission, reenters the Earth’s atmosphere, and comes in to land like a glider. The orbiter is then refurbished and refitted for another mission.

The failed or incomplete RLV or partial RLV programs include the
National AeroSpace Plane (NASP), Space Launch Initiative (SLI), Orbital Space Plane (OSP), DC-XA, X-33/VentureStar, and X-34. For want of budgetary support or technological feasibility or both, NASA has not been able to do it. Does that mean RLVs are impossible? No, but they are really damned difficult, and the work has been attempted by some very bright people, both inside and outside the world’s premier space agency. Jerry Pournelle is more optimistic on this score than I am. He believes that the problem with RLV/SSTO has not been the technology so much as the organizations running the programs. He believes if the old NACA “X program” model is followed, then technology development could happen—not immediately, and not with billions and billions of dollars spread around a number of big contractors and important states—but with single contractors, small budgets, shorter timeframes, and more humble goals. Unfortunately, I don’t think our government is up for small and humble anymore.

Space Elevators
How It’s Supposed to Work
space elevator (also called an “orbital tower” or “skyhook”) is a structure that stretches from a point on Earth all the way out to geosynchronous orbit. The centrifugal force of the Earth’s rotation counteracts the elevator’s tendency to fall, so the tower stands straight out from the planet like a giant radio tower. The structure becomes an “elevator” when you attach climber vehicles capable of transporting people or cargo up and down the tower’s surface—the most common imagined climber would be a maglev (magnetic levitation) train. The maglev climber would require only electrical power to move, and would not produce sonic booms or require explosive chemicals, as rockets do.
The Arguments Against It
The structural materials strong enough to build a self-supporting elevator were only theoretical until the late 20th century. Then companies began experimenting with artificial diamonds, carbon “whiskers,” and now carbon nanotubes. Unfortunately, no one has made enough carbon nanotubes (which are molecule-sized) to build load-bearing structures. At present, they’re simply too expensive to mass produce.

Another interesting argument I’ve heard is that the elevator would act as a massive short circuit for the entire planet’s ionosphere, which would essentially fry, melt, or disintegrate the tower. The argument here is that the large amount of charged particles in the Van Allen Belts would follow the elevator all the way down to the Earth, becoming the world’s largest lightning rod.

The last argument against the elevator comes from my own experience
observing the Space Elevator Games in Las Cruces in 2006. These Games are sponsored by NASA as a means of generating competition to create technologies that could lead to a space elevator. Rather than a typical wound cable (the original concept for the elevator), these experimental crawlers all had to make their way up a six-inch-wide, 60-meter (~197 feet) tall industrial belt suspended from a crane. We were in the desert, mind you, so winds tend to be a little fickle, but the best guess was that winds were gusting to 10-15 miles per hour. Even in that slight breeze, the belt was whipping about in the wind like a crazed sail or weather flag in a full gale. Several teams had difficulty just attaching their crawler to the belt, much less getting their vehicle to climb the twisting belt. My verdict: even at great tension, atmospheric effects on the Earthbound side of the elevator would prevent any vehicle from traversing the distance safely, to say nothing of what sorts of oscillations might develop when moving through orbital space.

Asteroid Mining
How It’s Supposed to Work
Planetary science professor John S. Lewis makes a pretty compelling
case for mining the metals of nickel-iron asteroids to fulfill resource needs here on Earth or for building settlements in space. These asteroids include massive amounts of iron (obviously), platinum-group metals (useful for fuel cells), water and ammonia “volatiles,” and the equivalent of natural stainless steel.
The Arguments Against It
We’ve landed a couple of robotic spacecraft on asteroids. They weren’t designed for that, but the gravity on asteroids is so small (measured in thousandths of a gravity) that they could just about turn off their thrusters and drop onto them without a jar. That microgravity will be a problem for humans working there, of course, as we’re
learning from the International Space Station.

Next, we have never developed the technical tools for mining, extracting, and refining materials in micro- or zero gravity. (An obvious answer, of course, is “why don’t we?”) However, most mining and refining processes done here on Earth require high heat and gravity effects to separate different components from each other.

Finally, returning to Lewis’s book, he made a point that if all of the useful metals and other materials were mined from a single Amon-class asteroid and sold on Earth at current market prices, their value would be $20 trillion. It’s a great theory that ignores economic reality. Let’s say we found an asteroid that really did make platinum as common as sand on Miami Beach. Even if the platinum were put to work building catalysts for a worldwide fleet of
fuel cells, the price of the commodity would drop to about what you’d expect to pay for a handful of sand in Miami Beach. The materials of the Asteroid Belt may be abundant, but they’ll have to make people rich in space because they sure as heck won’t be on Earth.

Space Tourism / Personal Spaceflight
How It’s Supposed to Work
Civilian excursions into suborbital space by Virgin Galactic, Blue Origin, etc., could generate enough demand and traffic to produce mass-produced rockets, experience in operating RLVs (see above), and capital for a functioning space economy in orbit.
The Arguments Against It
Space tourism has been “just around the corner” since 2004, and it looks like it’ll be another year or two before Virgin Galactic is able to fly paying customers aboard their Burt Rutan-built Spaceship Twos. A lot of operations have folded since the X Prize was won. Others are working in secret. Many things can go wrong, and the American public is not quite as willing to embrace risk as it was 40-50 years ago. One bad accident, and some believe that lawsuits will all but kill the “personal spaceflight” movement.

The more sarcastic individuals within NASA are quick to point out that SpaceShipOne did not make it to orbit, but “repeated something the X-15 was able to do 40 years ago, and Rutan did it using technology developed by NASA.” Aside from the sour-grapes and elitism in those comments, they are technically correct. Yet work on personal spaceflight continues because there still are people willing to shell out the big bucks ($250,000 for a flight on Virgin Galactic, if and when) to fulfill their dreams of space travel.


And these are just some of the issues to be addressed in the space business. I haven’t even touched on the Ares vs. EELV or DIRECT/Jupiter 120 debate (nor will I comment publicly on activities where I have a vested employment interest). I know a little more about the government vs. private sector debate, but feel that that’s an argument for another night. In any case, this evening I wanted to focus on technical issues because these are the bigger questions that I do not have enough basis in theory or practice to answer properly. Political questions are another matter.

So, seriously: if there are any technical folks out there who know a reasonably quick way to get smart on the big engineering questions floating around the space business today, I’d be happy to hear it. In the meantime, I can only help the ones who DO know the facts and theories behind their pet projects frame their arguments in better language. The rest, unfortunately, I have to take on faith.

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