Monday, November 07, 2005

Solar Heating Lowers Construction Costs

Solar Energy is a grim business. Usually, folks who decide to buy a solar system make some sort of projection about their fuel or electricity costs and then figure out how much the solar system is going to cost. The trouble is, these comparisons take thought, and are dependent on unknowns like the rising future cost of power, effective interest rates in the future, and structure depreciation. No wonder solar systems are a hard sell.

Well, things are changing in sunny California. Our Title 24 law sets energy efficiency standards for most buildings. A new revision of this law has come into effect as of October. Among other things, the law sets standards for window thermal resistance.

Essentially, California has mandated that you are going to save energy, relative costs be damned, but at least you get to pick how to do it. I could write a blog entry on how I feel about this kind of regulation versus simply changing the price of energy... but no. Today I want to talk about the solar industry.

The big news for the solar industry is that instead of comparing solar collectors to just burning fuel, people now get to compare solar collectors to better insulating windows. It's a much easier comparison, since you pay for both things when you build the house, and solar collectors come off looking very good in comparison. When the tract home developers figure this out, they're going to slap solar panels on any place they'll fit.

How's that? Well, consider a standard 4.5 foot by 3.5 foot sliding glass window.

A good aluminum-framed version will cost a few hundred dollars, and have a U-value of 0.61, which means that it leaks 0.61 BTUs an hour, per square foot, per degree F temperature difference. In San Francisco, where we have 3458 degree-days of heating each year, that's 797,345 BTUs a year -- about ten bucks.

As of October 1, California requires a U-value of 0.38 on most windows. These are pretty nice windows. To get that U value, you need double panes of low-E glass with argon fill, wood or vinyl frames, or high-end aluminum frames with thermal breaks. This window will cost a couple of hundred dollars more than the aluminum-framed window, and it'll leak about 300,000 BTUs a year less than the aluminum-framed version.

So here's the thing. A rooftop solar thermal system can supply those 300,000 BTUs a year for about $120. (That $4068 kit with 2 Gobi 408 collectors will pull down 80 to 120 therms a year.) And California will let you use inexpensive aluminum windows if you have a solar thermal collector to supply the extra heat.

Now some people are going to want the wood-framed window look, and so for those people this comparison doesn't much matter. But developers are the kind of folks (cheapskates, and I use that word endearingly) that will save a couple of bucks per house by using skinnier electrical wire. Saving $100 a window while being able to sell the resulting house as "green" is a fad they can embrace with enthusiasm.

But developers are also the kind of folks that prefer to suceed doing things they've seen other people succeed at. So, if you live in California and are building a new house, do your part and stick on a solar thermal collector. It won't take long to get the fad going.

Tuesday, November 01, 2005

Why Merlin?

My anonymous commentor is getting at a very interesting point. Why does SpaceX do their own engines when clearly better engines are available from Russia? The Russian engines have far better Isp, burn the same practical fuel mix, are available for known and probably reasonable amounts of money, and are known to work now (which takes a lot of schedule uncertainty out of SpaceX's plans).

Using Russian engines was Kistler's plan. Kistler spent five times as much money as SpaceX has without building a complete vehicle. Maybe it was their recovery system. Maybe it was their basing plan.

I suspect that using a Russian engine puts a big Chinese wall in the middle of the company, for both intellectual property and ITAR reasons. Enough of the vehicle design is tied to the engine design that what you end up with is a company that, to a noticeable extent, resells Russian launch services at the whim of international relations.

How big a deal can this be? The Atlas-V uses Russian engines, and is intended to be used by the military for sensitive launches. If Lockheed can do it, why not SpaceX?

According to Astronautix, Atlas V has launched 4 communication satellites, only one of which was a U.S. satellite, which was commercial. By comparison, Delta IV has launched 2 U.S. military commsats and a european commsat. My sense is that the U.S. military is averse to relying on a launcher using unsubstitutable components from a major overseas competitor, and funds the Atlas solely as a backup to the Delta.

I think SpaceX knows it will be dependent on launching U.S. military payloads, and knows it can't do that with Russian engines.

If SpaceX is sucessful, I expect an EELV, probably Atlas, to get cancelled by 2010. Delta will become the backup launcher, subsidized by the military and flying in very low numbers.

And seven years from now, I think the boost competition will not be United Space Alliance versus Ariane versus SpaceX. I think it will be SpaceX versus at least one Russian company (perhaps marketed by a western company e.g. SeaLaunch) versus the Chinese. SpaceX will get the U.S. military business by default. To win the international competition, SpaceX may need to figure out reuse.

Wednesday, October 26, 2005

Dry Launch 2: LH2 vs Kerosene

I had been expecting that LOX-LH2 would be less expensive than LOX-kerosene for a LEO-out boost.

At some goading by "anonymous", I reran the numbers assuming a different mission profile. (I really appreciate good criticism, by the way. Thanks.)

This time, lets assume SpaceX sends up Falcons whose top stages have been stretched to carry just extra LOX. The first mission leaves the top stage in orbit, later missions lift extra LOX to it, and we end up with a big LOX tank in orbit.

The LEO-out booster is launched from an EELV, e.g. Atlas. The idea is to use something that uses the dual-engine Centaur upper stage. You might want to consider a Falcon-Centaur, but then you have to deal with paying for all that integration and LH2 infrastucture when Boeing and Lockheed have already done it for you. My guess is that until there looks like a solid market for LEO-out boost, SpaceX will have nothing to do with Centaur.

Here are the numbers: An Atlas 551 can put 20,050 kg into LEO. If we assume an incremental tankage ratio of 25 (like the Space Shuttle external tank), we get a modified Centaur with enormously stretched tanks, 5.9x for the hydrogen tank, 4.9x for the oxygen tank. The Centaur launches with a full hydrogen tank and a nearly empty oxygen tank. After achieving LEO, the oxygen tank is empty and the hydrogen tank still has 83% of it's initial load. The Centaur picks up 86,240 kg of LOX from the Falcon tanker. This Falcon would have loaded LOX from 9 other Falcon flights. The stretched Centaur would then be able to add 4000 m/s delta-V to a 58680 kg payload. Burn time: 73 minutes.

That's a bit more than a third of the max payload of my earlier LOX-kerosene all-SpaceX proposal. Cost would be $270 M (SpaceX), perhaps $200 M (Atlas). Interestingly, the cost per kg ($8000/kg) isn't different from the all-SpaceX proposal ($8035/kg).

This didn't come out like I thought it would. First, note that the LEO-out booster performance is not terribly sensitive to the controversial tankage ratio, because the empty booster doesn't weigh all that much compared to it's payload, even if the tankage ratio gets cut in half. That's because 4000 m/s is not an amazing amount of delta-V if you have all day to burn your propellants. Maximum payload is affected, of course, and that has a big impact on the LOX-LH2 cost.

The fully fuelled LOX-kerosene LEO-out booster is heavier than the LOX-LH2 booster, but this big disadvantage is neatly balanced by the high cost of ground-to-LEO launch of the hydrogen.

The LOX-kerosene proposal assumes transfer of both LOX and kerosene, where the LOX-LH2 proposal requires the transfer of just one. My assumption is that the extra bother of kerosene transfer is not a deal breaker.

Here is a deal-breaker though: SpaceX uses an ablatively cooled combustion chamber and throat. Regenerative cooling is probably a requirement for this application, due to the ridiculously long burn times. I'm sure that regenerative cooling would be a major development headache for SpaceX. This makes a LOX-kerosene LEO-out booster unlikely unless SpaceX wants to develop long-burn engines for some other reason.  [Update: SpaceX has switched to using regeneratively cooled Merlins, so no deal-breaker any more.]

A LOX-LH2 LEO-out heavy booster would probably be better if a high-volume operator (like SpaceX hopes to be) were to pursue it. Assuming just a few uses, the choice is trickier. The LOX-LH2 option has less technical risk, as it requires no engine development and transfers just one propellant.

Saturday, October 22, 2005

Dry Launch

Jon Goff has posted the idea of launching a LEO-to-wherever booster into LEO, and then fuelling it with subsequent flights. This makes me wonder how big a dry launch / on-orbit refuel booster can SpaceX put up, with just Falcon 9?

First, we need a bunch of assumptions.

  • Let's assume the complete but empty booster has to go up in one flight, so no seperate launch of fuel and oxidizer. Seperate tanks should almost double the resulting booster size and launch/fuelling cost. Using a Falcon 9S9 with the big strapons would nearly triple the booster size and launch/fuelling cost.

  • Assume insulated tanks are 2% of fuel mass. Payload size is highly sensitive to this number, which I just pulled out of a handy nearby orifice.

  • Assume that both the fuelling rockets and the LEO-out booster are just Falcon 9 upper stages outfitted with larger tanks and (in the booster's case) lots of insulation.

  • Assume that without the fairing and payload interface bits the Falcon 9 can boost 10,000 kg to LEO. Assume 300 kg for fuel transfer hardware.

  • The resulting super-stretched Falcon upper stage / LEO-out booster should hold 475,000 kg of propellant, making it about twice the size of the Falcon 9 lower stage. If built with the same tank diameter (3.6m), it would be about 56m long. At launch, the whole thing would be about 89m long, with an aspect ratio of 25, which is pretty skinny but probably doable.

    Such a booster could give 4,000 m/s delta-V to a vehicle with a empty mass of 168,000 kg. That's enough delta-V to get out of Earth orbit to L5, low moon orbit, and at least near Mars, see this handy cheat sheet. It's also just a bit more mass than the Saturn V rocket put into Low Earth Orbit -- not excessive for a manned excursion to anywhere dramatic.

    It would require 49 fuelling flights, with a total cost (just for the booster) of $1.35 billion dollars with SpaceX's published prices. SpaceX's prices are for single launches, assuming no hardware recovery/reuse. 50 total launches would get them a lot of experience with recovery, and change the whole cost dynamic. It would also take at least of year of fairly amazing launch activity.

    An equivalent booster, launched with the Shuttle-Derived Heavy lifter, would require about 3 launches, as it uses liquid hydrogen, which really helps this application. Shuttle launches are hard to account for, but probably around $500M each, and if the SDH is similar, it would cost $1.5B for this booster, not counting amortized development costs.

    I don't think anyone would start an Artic expedition that required 50 plane trips just to build a cache of dog food, so I don't think this version of the idea is going to fly. Perhaps liquid hydrogen is inevitable for this application. Alternatively, SpaceX's Merlin 2-based launcher may get launch prices down enough that Kerosene and LOX make sense even for a big out-of-LEO booster.

    [Note: the next post answers comments.]

    Saturday, October 15, 2005

    Gun Launch

    It's said that people never publish negative results. Well, in response to a comment on the previous post, here's mine.

    Most every engineer who has looked at a rocket launch has been appalled at the horrible efficiency of a rocket coming off the pad. At the moment of launch, the rocket is using as much propellant per second as it can, throwing away nearly all that energy in gravity losses, and getting very little velocity with the rest. Almost anything can convert propellant energy into projectile velocity more efficiently than a rocket just off the launch pad.

    One of the best things, it turns out, is a cannon. A cannon with reasonable muzzle velocity uses the earth or the cannon as the reaction mass, where a rocket just uses the propellant itself. More mass means more efficiency. So many folks have wondered, why not use a cannon to launch a rocket?

    It's been done, of course. Back in the 1960s, and 1970s, and finally 1980s, Gerald Bull looked into using cannons to launch rockets. I've looked at Gerald Bull's work. His is a sad story -- the guy got so taken by the promise of his research that he eventually let his ethics slide. When the U.S. military cancelled his funding, he started doing work for nearly anyone who would pay for his research. Near the end, he was doing work for Saddam Hussein, at which point he was assassinated, maybe by Israel, but maybe not.

    But nevermind about Mr. Bull, what about gun launch?

    Cannons convert propellant energy into projectile kinetic energy well when the muzzle velocities are well below the Ve for the propellant combination -- around 2000 m/s for solid propellants, and 3000 m/s for liquids (liquids have better oxidizers, see wikipedia). Most guns have muzzle velocities much smaller than that, so you see very good payload/propellant ratios, as my commenter "fred" stated. (Fred should check his numbers, though. A 1000 m/s rifle round has a payload/propellant ratio closer to 2 than 100.)

    Low-energy gun launch has been done too. An MX missile launch from a silo starts by blowing the missile 100 feet out of the silo with compressed air, and then air-starting the rocket. This is done to make the silo cheaper, not to give the missile any substantial delta-V. One could conceivably boost a satellite launcher this way as well, but the delta-V is probably limited to 100 m/s or so, which isn't enough to help the rocket much. And it's certainly less safe than starting a set of liquid-fuelled engines while bolted down, checking for correct operation, then releasing.

    High-energy gun launch only makes sense for bulk payloads like fuel. High value payloads like comsats and people are never going to take the accelerations from any cannon anyone can afford to build. But still, one wonders, maybe just for bulk loads....

    Guns really get expensive when muzzle velocities approach Ve. Essentially, the propellant gases run out of energy by the time they expand enough to act on the base of the projectile. To even get close to Ve, the gun has to accelerate a good fraction of the propellant before it burns, and now we're talking about a rocket inside a gun barrel. And we enter the realm of rocket-like payload/propellant ratios, but with a very nasty twist.

    Lots of propellant isn't a problem by itself (the propellant is cheap). The problem is processing all that propellant. More propellant requires more stuff (plumbing, pumps, thrust chambers, or gun barrel) to contain and process it. Launch guns process all the propellant in a very short period of time (tenths of a second), which means they need two orders of magnitude more stuff than a rocket to process the same amount of propellant. Sure, it's simple stuff (a gun barrel), but there is just too much of it.

    A few years ago I thought I'd had a clever idea here. Since a gun doesn't have to contain the blast for very long, I figured you might be able to build a thin barrel and then immerse it in the mud at the bottom of a lake (or any other high density fluid). When the gun fires, the barrel attempts to explode, but to do that it has to move the mud out of the way. This is inertial confinement: the mud can't move away fast enough, so instead it compresses. The gun propellant deflagration turns into a pressure wave in the mud, which can be arranged not to crush the barrel after the barrel pressure returns to normal. You get to make a big cheap gun, that is horribly difficult to point at different things, and so pretty much worthless as a weapon. Sounded good to me.

    I wrote some simulators, and faced the following choice: after gun launch, would the projectile have one stage or two? (I assumed liquid propellants. Bull used multiple-stage solid propellant rockets.)

    If the projectile is a single stage, then you need a muzzle velocity of at least 2500 m/s. That's fast enough that the round inside the gun ends up looking like a big solid rocket -- one that burns it's fuel in a fraction of a second. Since solid fuels burn at centimeters per second, you end up with a highly perforated fuel grain and a very nasty ignition problem (all that surface area has to simultaneously jump a thousand degrees C in a few milliseconds). Also, this fuel grain itself has to survive hundreds or thousands of Gs of acceleration, and to do that you end up using carbon fibers as the fuel rather than HTPB or something more standard (and higher energy).

    Then comes the brutal comparison. If you were going to do all that work to put the rocket in the gun barrel, how does it compare to just having an ordinary solid rocket first stage? Answer: the ordinary stage has way lower capital costs, isn't much bigger, and doesn't subject the payload and avionics to brutal accelerations.

    Okay, so what about a medium-energy gun lauch of a two-stage rocket? Starting with 1000 m/s or so really does help the payload quite a bit. But the massive acceleration requires building that rocket to be very sturdy, so most of the payload ends up being structure. And a two-stage liquid-fuelled rocket can get to orbit just fine without a gun launch to start, while being so much simpler.

    In short, rockets may seem horrible coming right off the pad, but they don't spend much time at low speeds. They get up to canon-muzzle-velocity-like speeds in 30 to 50 seconds, and then they get to keep using that engine hardware to go a whole lot faster.

    The best optimization yet found for the first 30 seconds of flight is strap-on solid rocket motors: they're cheap, fairly reliable, small, and require few changes to the support infrastructure. If the rocket has some delta-V margin and positive acceleration even if the strap-ons fail to ignite, then failure of one of the strap-ons can be survivable.

    Wednesday, October 05, 2005

    False choice

    You don't have to be an Evangelical Christian to be fed up with the way science is taught in the primary and high school classroom these days.

    Science is different from Belief. There is a process to science. Some folks propose hypotheses, with which anyone can make predictions (otherwise the hypotheses are useless and mostly ignored). Those predictions are then tested.

    Over time, we get some confidence in old theories that haven't been proved false. Confidence comes from checking theories on your own, and it comes from confidence in other people checking theories. We develop confidence in the journals where their papers are published from the occasional well-publicized mistakes. People who cheat are found out, and that news gives you confidence that the system is checking claims being made. Some scientists make great names for themselves, but their theories are still checked and contrary evidence is received with skepticism, but if validated, fanfare.

    New science has not yet earned this confidence. For example, string theory is not yet well accepted, but much of quantum mechanics is. It's fun, and the continuous stream of claims and counterclaims is not surprising once you understand that these are younger and untested theories.

    Belief, on the other hand, is not about making falsifiable predictions. Belief is about understanding yourself, what you should and should not do. It's about morality and emphathy.

    To science, there is no difference between Mendel experimenting on peas and Mengele experimenting on Jews. It's just data (in both cases, unscientifically falsified to try to prove a point). There is a huge moral difference, of course, and that's where Belief comes in.

    The trouble I see is that most science education doesn't teach science. Instead, science education teaches something like Belief in scientific theories. The result is neither science nor religion, but a glib materialism that assaults religion and cherishes a lack of critical thinking. I think many conservative religious leaders are right to think that science is being taught as an alternative to religion. Many people, me included, would like to see this kind of teaching banished from the classroom. I'd like to see reporting with the same mindset laughed out of the mainstream media while we're at it.

    That doesn't mean I want to see equal time in the classroom for Intelligent Design. I know Intelligent Design is not well accepted. More worrisome, I have heard of no actual hypotheses with which independent labs can make testable predictions. The alternative theory, evolution, has a long productive history, during which many papers have been written and a great deal of elaboration and independent verification has taken place. There is no such productive history in the scientific literature for Intelligent Design, and so I have no confidence in it.

    Religious leaders appear foolish when they attempt to construct alternative science, because they appeal to authority rather than verification. Usually this happens when people interpret ancient texts too literally. Genesis says the world was created in 7 days several thousand years ago, and all the animals were created at one time. Unfortunately for literalists, we have a lot of physical evidence that says this planet was created 4.5 billion years ago, and has experienced an evolving population of fauna subject to periodic mass extinctions. I have confidence in much of that evidence and the generally accepted scientific interpretation of it.

    On the other hand, Jesus is reported to have said, "do unto others as you would have them do unto you". This shows up in the mathematical literature under game theory, which frankly hasn't given me a whole lot of insight or motivated my compassion for other human beings. But I've always enjoyed listening to sermons on this kind of thing, I love the singing in church, and I often find I have a refreshed appreciation for the condition of others after a good service.

    As an aside, I don't really understand this need to interpret texts so literally. The need for continuous discussion and contemplation of morality is not based on the number of days it took for the world to form, either according to physical laws or divine will expressed any other way. The need for morality comes from our being intelligent social creatures living in crowded conditions.

    If we are to have a debate about the seperation of Church and State in the classroom, let's have it about what gets taught in Civics. Civics teaches what you ought to do and ought not to do in civil society. It requires us to agree on a common set of beliefs. Since many religious leaders around the world regard the existence of other religions as anything from irritating to blasphemy to a justification of murder, this is clearly an area deserving of robust public debate and continuous refinement.

    Meantime, let's see some real science being taught in the science classroom. Kids should be taught to check theories, but they should also be taught to check primary sources in the literature. They should learn about the process, read reasonable-sounding theories that were disproved, and how. This way we can grow their confidence in older and more accepted theories. This way they can learn to listen with skepticism to the endless litany of new claims brought forth by medical researchers testing small groups. This kind of education can help prepare them for the world.

    Monday, October 03, 2005

    Men in Space

    I read the Washington Post editorial. They don't like the costs and lack of results from putting people in space. I think they don't much like space exploration at all.

    So, why astronauts?

  • Science. Some claim that people can do things that robots cannot. It's true. But it's also true that robots have staying power, and people do not. Right now, the balance is overwhelmingly on the side of staying power. Michael Griffin himself has admitted that space science not focussed on people is best pursued without people.

    Consider: Apollo used a noticeable fraction of the U.S. GDP to put six pairs of men on the moon for a total of a couple of man-weeks. For three to four orders of magnitude less money, the Spirit and Opportunity Mars rovers have gone much farther, and seen more, and are still working away more than a year after they landed. Apollo returned samples, which we have not yet done from Mars (but have from deep space). The thing is, sample return does not require people.

    The choice is not robots versus people, it's robots versus robots-and-people. Consider just the fingers of a glove of a space suit suitable for use on the moon. The stiffness from the pressure difference is so high that the hands of serious athletes are cramping and exhausted within hours. Next generation space suits may use mechanical hands outside the suit, operated from within. Such waldoes are already standard practice in many kinds of surgery, deep sea research subs, and some hazardous materials operations. Notice that the control for that waldo can go in the space suit, or in a vehicle, or in a spaceship, or in an office in downtown Houston. One of those doesn't require a mission-critical life-support system.

    In fact, there is no choice. There will be robots now, and there will be robots and people later. In between, we can launch people if we like, but they won't do much.

  • Prestige. Which event gained more international and domestic attention: Shuttle mission STS-113 to the ISS (which installed the P1 truss), or the Deep Impact comet probe rendezvous? Which cost more?

    The problem with manned spaceflight right now is that the next step is really hard. It will be a long time before we are able to do something obviously new and exciting. But for unmanned probes, there are dozens, perhaps hundreds of interesting places to go, all within reach of rockets we have today.

  • Destiny. Sigh. The claim here is that humans will eventually populate other places, so we should do it now. I'm really bothered by this kind of reasoning. Karl Marx said that communism was the inevitable end of the evolution of nations. When the inevitable seemed like it was taking too long, Lenin and Stalin tried to hurry it up a lot, eventually by starving the peasants, destroying their economy, and nearly destroying the Russian culture.

    Our destiny will arrive on its own schedule. People will work in space when it makes economic sense to do so. Eventually those workers will have significant needs and desires of their own, best satisfied in space, and... off they go.

  • NASA's Mission. NASA's original mission was not to launch people into space. NASA's original mission (as NACA) was to do basic research on atmospheric flight. The goal of this research was to develop technologies that, while potentially useful to the U.S. as a whole, would not be pursued by private companies that need predictability and exclusivity to satisfy shareholders.

    When the U.S. and the Soviet Union began competing for world mindshare by pulling ever-larger stunts with rockets, NASA got the job of putting men on the moon (and returning them safely).

    The prestige mission of men in space can be retired, just as the B-1 bomber fleet was retooled to carry conventional weapons instead of nuclear ones. It was useful, and it is over. NASA should get back to doing basic space science. Telescopes, nuclear power and propulsion, extraterrestrial geology, that sort of thing. They will eventually find the killer app up there. They have not yet, but there is no need to be impatient. Meantime, we should enjoy the pretty pictures and exciting discoveries.

    P.S. If Michael Griffin ever reads this blog, can you please point out to your mission designers that the most important instrument on every probe is the high-resolution camera? The images returned are the data best interpreted by the people who are paying for all this science -- the U.S. public. The other science is important too but none of it matters if it doesn't matter to Joe Sixpack. Mission designers who do not agree should feel free to get private funding of their probes.
  • Tuesday, September 27, 2005

    LH2: Love it or hate it?

    Jon Goff has an absolutely fantastic post here at LH2: Love it or hate it?

    LH2 seems most clearly stupid for a first stage fuel. Hydrogen engines have low thrust-to-weight, low thrust-to-cost, and big tanks which can cause a lot of atmospheric drag. Hydrogen first stages also see larger gravity losses than hydrocarbon first stages.

    Both the Shuttle and the Delta IV use LH2/LOX engines off the pad. The Shuttle uses hydrogen because those engines are ground-ignited second stage engines, so it has at least some excuse. But the Delta IV is a simple two stage rocket with both stages being LH2/LOX. Why? Did they need to be different than the Atlas V?

    Thursday, September 22, 2005


    I just read a fantastic article in The New Republic. In it, Husain Haqqani & Daniel Kimmage comment on a series of 430 short biographies of Iraqi insurgents. At the end, they have a suggestion I really like:

    Imagine how the biography of the "hero" Al Shammari would read if it were juxtaposed with the biographies of the people he killed? What might readers in Saudi Arabia, Syria, and elsewhere in the Arab world make of a companion volume to "The Martyrs" in which each suicide bomber faced his victims, not as statistics in a war against the infidels, but as individuals in their own right?

    Friday, September 09, 2005

    Falcon 9 Upper Stage Recovery

    The SpaceX annoucement is fluffy. Their big engine is late, and they're going to try to push their Merlin 1 based product a bit past its economic sweet spot.

    Significantly, SpaceX has not specified the upper stage. The upper stage for a plain Falcon 9 to LEO lift will require at least two and perhaps three Merlin engines. The upper stage for a Falcon 9-S9 to LEO lift (required to deliver a Space Shuttle cargo to the ISS) will require at least five Merlins, which means it will actually be a Falcon 5 first stage, but with large expansion ratio nozzles and some ability to do in-space restarts (propellant settling, multi-use igniters, RCS without gimballing the main engine). If they are going to recover that stage, though, they'll need more than just the F5's parachutes, they'll need some really wonderful ablatives, somehow spread under all the delicate engine bits.

    If you ignore the upper stage reuseability, the business scheme seems wonderful. NASA needs 20+ heavy LEO launches to lift the rest of the ISS. SpaceX builds a fleet of identical airframes and engines. Four airframes and 32 engines go up, three and 27 come back. They build about 25 airframes and 140 engines over several years, and each airframe gets an average of three flights, and each engine gets four or five. They might charge NASA $1.5B for the whole launch set and make a ton of money, and save you and me (i.e. the average taxpayer) about 75 bucks apiece.

    But what's this about Full reuseability? Full reuseability is not a press mistake. The SpaceX press release says explicitly that

    Falcon 5 and Falcon 9 will be the world's first launch vehicles where all stages are designed for reuse.

    (Except Kistler's design, of course.)

    This is crazy. If they take over lifting the ISS segments, they'll have a nice steady stream of launches. Over time, they're going to learn how to manufacture their engines better (more thrust, better reliability, lower manufacturing costs), and the later engines will be better than the earlier ones. The steep learning curve makes the early hardware depreciate fast, which makes spending more money to recover it less attractive. Throwing away the upper stage is a great way to clear out the obsolete inventory.

    Heck, at some point (2007?) they're going to deliver the Merlin 2. My guess is that this will be a 600,000-lbf-thrust engine. Their next-gen EELV-class launcher will lift 25,000 kg to the ISS without strapons, with four Merlin 2's as the bottom stage and four or five Merlin 1's as the top stage. Why use the Merlin 1's in the upper stage? Because their business plan requires each engine to get used a bunch of times. The last thing they want to do is introduce a new rocket which obsoletes $60 million dollars worth of engine inventory. Instead of recovering a brand-new engine from the upper stage, it will be cheaper for them to use and expend their Merlin 1 inventory in the upper stages of their launches.

    I bet the upper stage reusability verbiage is just there to appease some group at NASA. SpaceX may actually attempt a controlled upper stage reentry with ablatives when launching some slightly more lightweight ISS segment. They may get some interesting data from such experiments. But I can't see them pushing upper stage reuseability very hard. They need to concentrate on the easier and more lucrative problem of recovering their lower stages first.

    My Own Vision for Space Exploration

    Since I think Bush's Vision for Space Exploration is screwed up, I thought I'd offer my own.

    Unmanned exploration

    I would initiate a steady program of planetary probes, a common interplanetary communication system, and space-based observatories.

    Budget: $4B/year for about 6 probes a year over 2006-2016
    about 30 heavy and 30 medium launches
    Budget: $8B for 3 observatories over 2009-2016.
    about 10 heavy launches

    Exploration infrastructure

    Most probes are limited by their ability to transmit data back to Earth. That ability is limited by the power available to transmit. For the planets beyond Earth (or perhaps Mars), power is limited because solar cells do not have significant yield. I would fully fund the Prometheus project, which is developing a small nuclear reactor for use in space.

    Beyond finishing the development of nuclear reactors in space, existing technology is already comfortably close to the limits of what can be transmitted for a given amount of power. It makes sense, then, to have multiple probes in close proximity use the same communication system. This is already done to some extent at Mars, with Mars Odyssey and Mars Global Surveyor relaying signals for ground rovers.

    I would initiate a program to launch a nuclear-reactor-powered long-range communication satellites into orbit around each of Venus, Mars, Jupiter, Saturn, and Uranus, and (probably) one roving satellite in the asteroid belt. These satellites would primarily be responsible for relaying high data rate bit streams to earth from local probes. They would be built for a useful lifetime of 25 years. They would also carry a modest scientific payload.

    Budget: Prometheus: $4B over 2006-2010
    Budget: Comsats: $12B for 6 comsats over 2011-2016
    about 20 heavy launches

    Orbital Assembly Development

    Observatories and comsats, and to some extent probes, have one thing in common: very large communication dishes or imaging reflectors. Observatories and especially the extraterrestrial comsats will also be very heavy. All of these missions can benefit from orbital assembly. I do not forsee intricate assembly of the sort requiring people, nor do I see the ISS as a good place to do this assembly, as it will likely involve close proximity to very large amounts of propellant. I would fund one assembly robot in low earth orbit.

    Budget: $2B for one assembly robot over 2006-2010.
    2 heavy launches

    Transportation development

    The extraterrestrial comsats in particular and long-range probes in general have large propellant requirements. To avoid the need for seldom-used massive launchers and their infrastructure, these probes should be boosted to their destinations by the same stage that put them into low earth orbit, but refueled in orbit by other rockets, so that multiple launches can assemble the mass to be launched out of LEO.

    To help the nascent boost industry, NASA would be required to fit all payloads into the standardized EELV payload masses and sizes. Payloads intended to fit in the Shuttle for ISS delivery will fit into Heavy EELV boosters.

    The Shuttle program would be summarily dumped. If ATK thinks that solid rocket boosters are a good match to LEO delivery (as they may well be), they are welcome to collaborate on an EELV booster to compete with the existing 2 (Delta 4 and Atlas 5) and potential 1 other (Falcon 9).

    NASA would develop a Crew Transfer Vehicle. This vehicle would be a capsule carrying about six that would ride as one of the smaller EELV payloads (perhaps the 9000 kg class). If t/Space thinks they can drop-kick people to the ISS for less money, I'd entertain a proposal.

    Budget: $2B over 2006-2008 to develop the CXV.

    Manned spaceflight

    The International Space Station would be completed with EELV Heavy launches over the next several years.

    Budget: $4B over 2006-2010 (just for cargo launches)
    about 20 heavy launches (ISS segments cargo only)

    As well as assembling the station, crews would be sent up fairly often to perform science experiments.

    Budget: $1B/year over 2006-2016 (just for the launches)
    5 medium launches per year.

    Manned exploration

    There isn't going to be any of this in the next 20 years. Instead, NASA would spend some portion of it's budget learning how to live, work and do science in space. In the meantime, all the probes launched would find out what we actually want people to look at.

    Budget: $2B/year over 2006-2016


    My total yearly budget ends up about 70% of what NASA spends today. Probably I have no idea how much things cost. In particular, I left out ISS operational and future segment build costs.

    I don't see any massive increase in the launch rate. Over the next
    11 years, I see about 160 launches with a total price tag of about
    $12B. A billion dollars a year seems like enough money to keep
    perhaps two players going -- with just 1000 employees each.

    Heavy: 82 @ $100M/each
    Medium: 80 @ $ 40M/each

    Thursday, September 08, 2005

    SpaceX choices

    SpaceX has just announced a new, bigger launch vehicle. It has a number of configurations, some of which are roughly the size of some of the Evolved Expendable Launch Vehicle (EELV) sizes. The EELV program was a Defense Department-funded program to develop two launch vehicles independent of the Shuttle for military payloads, started after the Shuttle fleet was grounded after the Challenger accident.

    Q: What is the Falcon 9 intended for?

    A: The Falcon 9 is intended for three missions:

  • Steal payloads from the other two EELV boosters: Delta 4 and Atlas 5. These payloads are mostly military, and the Pentagon would very much like to have a reasonable fallback if they have to cut funding to one of the two subsidized EELV launchers. The Pentagon likes this idea so much they are spending real money on it: Falcon 9's first launch is a defense department satellite.

  • Replace NASA's "Stick" booster.

  • Lift the remaining ISS sections.

    Q: Why has SpaceX announced Falcon 9 now?

    A: SpaceX wants to stick a crowbar into the public debate over NASA's two new boost vehicles. I'm sure the competing camps at NASA have been fully aware of SpaceX's Falcon 9 plans for a while, and probably driving them to some extent. But NASA's decisionmaking is not entirely internal -- they have to convince policymakers to fund their plans, and quite a lot of that convincing is done by attempting to frame the public's perception of those plans.

    The ATK/Morton Thiokol lobbyists, and their camp within NASA, have been pushing two new mostly expendable launch vehicles, one to launch a 21 - 26 metric ton crew capsule and resupply ship to the International Space Station, and one to launch Very Heavy Things (110 metric tons) needed for manned lunar or Mars expeditions. Both would use solid rockets derived from the Shuttle SRBs. The big launcher might throw away four reusable SSME engines per launch, which is expensive.

    The push isn't going well right now. Developing two vehicles will cost more than NASA is spending now, and that looks very bad to legislators spending hard-won tax dollars on the non-pork-barrel Iraq war and the $700 million/day cleanup of Katrina.

    Jumping into the fray now lets SpaceX grab some of the public's mindset before it gets solidified by the ATK camp. They have a launch coming up soon. If it succeeds, John Q Public is going to wonder why NASA can't use the reliable SpaceX booster instead of developing a nearly brand-new launcher.

    NASA's designs for a Shuttle-derived Shuttle replacement center around the idea that the technology development, supply chains, and infrastructure it has developed for the Space Shuttle are valuable in their own right. Because the Shuttle is nearing retirement, all three of these things are in danger. For instance, if there is no future vehicle to use a Shuttle/SRB-like solid rocket booster, ATK will have to shutter its plant for assembling these monsters. NASA is absolutely right in realizing that a unique capability that only exists within the U.S. will vanish if that happens.

    But the hard question is: are those capabilities actually useful? The ATK boosters, for instance, produce 3.3 million pounds of thrust each, and cost about $40 million per launch. A simplistic analysis of SpaceX's launch prices put an end-user cost of $2.25 million per launch on each Merlin engine, each of which produces 85,000 pounds of thrust. The solid rockets are a much better deal for straight liftoff thrust, at $12.12/pound rather than the $26.47/pound of the Merlins. (The price difference is mitigated significantly but not reversed by the better Isp of the Merlins.) The as-yet-unfulfilled promise of SpaceX is that they are going to recover their engines or even most of the vehicle after each launch, and then will reduce their prices. And, of course, prices in the launch market are flimsy: I read wildly different estimates for costs and have not done my own accounting of NASA's costs, which I assume are public record.

    I think the SpaceX entry is great for SpaceX. I had lamented earlier that the Falcon V was just not big enough for ISS resupply. Falcon 9 solves that. This gives SpaceX an obvious and fairly large launch market (I'm guessing three-plus launches a year), which should give them an operating profit with which to fund future development. It should also give them a launch history. It's up to them, of course, to make that launch history one to be proud of.

    One hopes that launch market is also an elastic market: since SpaceX's prices are quite low, NASA might get to eventually rotate more of its astronauts through the ISS and actually do some science up there.

    I think the SpaceX entry is great for NASA. It gives them the excuse to retire the Shuttle early. It gives them a cost-effective way to assemble the ISS without the Shuttle. With some foresight, they may be able to focus on the in-space aspects of putting people on the Moon or Mars instead of spending all their money on ground handling of launchers.

    Lingering problem #1: How does NASA kill off the Shuttle-derived Heavy Launcher? NASA's standing army can't be dismissed until that thing is dead, gone, and maybe replaced. Or perhaps, the folks at NASA will let go of the need for big heavy launchers. I can see this happening for missions with large fuel requirements (launch the fuel seperately).

    Lingering problem #2: SpaceX needs to launch a bunch of Falcon 9s before anyone should be confident that they are safe enough for people. What are they going to launch? Possible answer: ISS cargo-only resupply missions. Stretch goal: launch astronauts on Soyuz, and launch ISS sections on big Falcons. It might take a lot longer to assemble the ISS with just 4 people on board, but it might still be doable.

    Finally, SpaceX's F9-S9 launcher has no less than 27 2.25-million-dollar engines at the bottom, and their launch prices are about $3000/kg to LEO. Maybe those engines are going to get cheaper if they start cranking them off the production line. But it seems to me SpaceX needs a bigger engine (and a larger diameter standard fuselage), because the current scheme isn't going to scale up much larger. Elon Musk promised that such an engine is in development, but it must not be well enough developed to enter into the current debate, as SpaceX is going to have enough difficulty getting credibility for even the Falcon 9. SpaceX development is late, and they are starting to reap the costs of being late.
  • Tuesday, August 30, 2005


    Yesterday on KQED's Forum program Michael Krasny hosted a panel talking about Graffiti in San Francisco. I thought a lot of these folks were talking around the right idea without nailing it.

    One panelist had previously been a graffiti artist and was now a professor of Chicano studies. He thought we needed to engage the kids more (I thought, yep), give them avenues to express themselves (uh oh). Then he got off on a diatribe about how our culture oppresses these kids, is private property really moral, that sort of thing. Michael cut him off and he didn't go there again. It's a shame. I think the issue of private property is the right one. Kids join gangs to get power. Gangs are tribes. We want to belong to tribes.

    Most of us, especially teenage boys, want to find our place in the world. We want to assert control. We want to find out who we boss around, and who we are going to have to obey.

    Prehistorically, we joined tribes to gain power. A small tribe can have a readily understood structure, so you can figure out how to improve your position in the tribe. Then you can improve the tribe's wealth by asserting ownership of the environment. If that stuff is currently owned by someone else, you steal it. Sometimes this involves tribal warfare, like going to a nearby tribe and killing all the men and boys there (drive-by shootings). This take-and-take-back is what establishes tribal boundaries. It appears to have worked well enough in the past with Amazon-jungle-like population densities.

    Here we are in the modern world, where this kind of behavior involves unsustainable mass slaughter (e.g. Iraq). Nowadays, there is an awfully big mega-tribe with an unfathomable structure. I'm trying hard to find my place within this mega-tribe. It's not fair, the power structure excludes lots of people who aren't born into the right families.

    Lots of those people are trying to find a way around the mega-tribe. The tribe will tolerate some of this behavior. It will absorb some of it, changing the tribe itself, changing the identities of the winners and losers within the tribe. Heck, Open Source is like that, a subversion of the intellectual property regime that has served so many others so well.

    But the tribe can't change too fast, or too many tribe members lose out. That's not in our interests. If you want to change the rules on private property, if you want to be a squatter, or a graffiti artist, or (for that matter) a Chinese businessman who sells unlicensed copies of designs originated elsewhere, you'll affect too many comfortable tribe members and we will come down on you, hard.

    It seems petty to arrest and jail a ten-year-old tagging the side of a Safeway in San Francisco. One panelist talked about councelling for these kids. Sounds good, but any councelling is going to have to involve waking them up to a set of unpleasant realities, so they can get on with working within the structure of the mega-tribe:

  • They really are oppressed. This condition will not change in their lifetimes.

  • We really will keep sticking them in jail if they try to assert their rights over the ones we unjustly inherited.

  • The system for remedying their situation ("democracy") is malfunctioning badly, and there is very little they can do about it without a lot of thought and selfless action. The latter is not going to improve their personal situation.

  • There is no obvious legal route for them to get rich. If they work hard within the existing system, they can join the middle class, get a mortgage, and become indentured to the international capital system like the rest of us. And they'll be discriminated against the whole way.

    For those of us born to better circumstances, we need a clear-eyed understanding that we can't afford to discriminate against very many other people for very long. Eventually they'll figure out how to organize against the existing structure. We need more of the people of the world, especially those who live closer to me, to have a clearer path to at least some measure of personal fulfillment. Since there isn't enough material wealth to go around, and our media spends at minimum 20 minutes of every hour hammering home the message that unlimited material wealth is a baseline requirement for happiness, it seems to me that the message that our media is sending is opposed to my interests, and those of most owners of private property.

    I doubt I'm the first one to figure this out. Maybe this is why the sons and daughters of the rich have a greater tendency towards philanthropy: it's better to give some of it away than have all of it taken from you.

    And of course, it sure isn't all the media's fault. I just can't think of anything else right now.

    Mood: grumpy.

    Side note: remember to pray for those folks in Louisiana tonight. Maybe when they rebuild New Orleans they can put the whole city on piers, like Venice. Seems more reliable than pumps, and as Venice shows it's quite romantic.
  • Wednesday, August 24, 2005

    Hydrogen from nuclear reactors

    I used to think this was part of the Hydrogen Economy scam. Now I think it might be a good idea, but it appears to be justified to the public as part of the Hydrogen Economy scam.

    Here's the idea: electrolysis of water to make hydrogen is expensive (about $2.46/kg at $.05/kW-hr), because electricity is expensive. But electrolysis at very high temperatures takes much less electricity, since the heat supplies much of the energy. Nuclear reactors can supply that heat cheaply. New gas-cooled high-temperature reactors can supply heat at 850 C. General Atomics has published a report that claims hydrogen could be produced from high-temp reactor steam for $1.53/kg.

    Yawn. In 2003, hydrogen from natural gas cost $1.40/kg. Sounds like a boondoggle for the nuclear industry, combined with some Hydrogen Economy crap that generally makes my skin crawl. Buuut...

  • At May 2005 natural gas prices, hydrogen costs $2.70/kg.

  • The domestic U.S. consumption of hydrogen is huge: about 11 million metric tons per year. Half gets used to make ammonia (fertilizer), the other half is used to hydrocrack heavy hydrocarbons into lighter, fuel-grade stuff. World production of hydrogen is growing at 10% per year. Growth is probably faster in the U.S.

    Bottom line: The U.S. spends $30 billion per year to make hydrogen, most of that is the cost of imported natural gas. The dollar volume is going up very fast as consumption increases and gas prices rise. Billions of dollars a year can be saved by making the stuff at nuclear reactors, and that is billions of dollars directly diverted from importing natural gas.

    Near term future: We're going to need a lot more hydrogen as the hydrocarbon stocks we process for fuel get heavier, for instance, if we start using oil from Canada's Athabasca tar sands. Note that hydrocracking is not a clever way to get ordinary cars to run on hydrogen: Refineries will use the minimum amount of $1.60/kg hydrogen necessary to convert and sell their $0.30/kg crude as gasoline for $1.50/kg.

    I'd think these reactors would be more appealing for their operator than the current offerings. Instead of being stuck with base load electricity prices, they can make electricity during the day, when prices are higher, and make hydrogen at night, when prices fall. It's expensive to store hydrogen, but you can probably store a few day's worth before you pipe it to the refinery down the street. And as long as these reactors are just down the street from oil refineries, there's a good chance the refinery can use some process heat from the reactor, too.

    Finally, there is an international market for any such nuclear reactors, as well as the ammonia that we can produce from them.

    The market seems big enough: hydrogen consumption is growing fast enough that you could build 5 new one-gigawatt reactors each year just to keep up with the growth, assuming each makes hydrogen 24x7.

    So why should the U.S. government subsidize these reactor designs?

  • Macroeconomy: Because a billion dollar subsidy can reduce our balance of trade by $30 billion.

  • National Security: Because it can reduce our dependence on oil (in two ways) by a useful amount, and this is a noticeable step towards energy independence.

    P.S. But none of this means that running cars directly on hydrogen is anything but stupid. It's just too expensive for that. If Governor Schwartzenegger gets a clue maybe he can dump the hydrogen-fueled Hummer and help secure licenses for 6 more 1100 MW units at Diablo Canyon.
  • Tuesday, August 23, 2005


    Nuclear disarmament is a good thing. Reducing the weapons stockpiles in the U.S. and Russia has left both countries with large stockpiles of highly-enriched bomb-grade uranium and plutonium. Every terrorist in the world wants to get some, some terrorists are rich, and some 40-year-old nuclear workers in Russia are living hand-to-mouth. It's a dangerous situation.

    In 1991, Senators Nunn and Lugar had a good idea. The government-owned U.S. Enrichment Corporation (USEC), which operates enrichment facilities in the U.S. to provide fuel for commercial reactors, would buy a portion of Russia's nuclear stockpile so that it could be burned in U.S. commercial reactors. This is a great idea, and a pretty good summary can be found here. There is a snag, however:

    Russia wasn't going to send bomb grade material directly to the U.S., because that would be like actually selling us nuclear weapons. Instead, they mixed the bomb grade stuff with Russian natural uranium, so that the result was 4.4% U-235 -- just right for a commercial reactor. The overall flow of reactor-grade material would have replaced a good chunk of domestic U.S. uranium demand.

    Domestic U.S. uranium suppliers didn't like that. Together, the U.S. and Russia have about 2000 metric tons of bomb-grade material, equivalent to 12 times annual world mine production. By the time the U.S. civilian reactors had burned through Russia's half of this stockpile, the domestic U.S. uranium suppliers would be out of business and Russia would end up being the majority uranium supplier to the U.S.

    So the deal was that Russia would buy the American natural uranium from the miners that was displaced by the Russian imports. This uranium would be stockpiled in the U.S. in USEC's custody. The U.S. goverment got two commercial reactor operators to promise to buy the Russian uranium eventually. Russia would sell the rest off over sufficient time.

    Realistically, it's going to take many decades to work through that stockpile. Now that they've been paid off, the domestic U.S. miners have mostly stopped digging, which will help. Getting this stockpile is yet another good reason to build more nuclear powerplants (though not the strongest, of course).

    The notion of U.S. mining interests delaying such an incredibly important piece of national security work so that they could protect their bottom lines still strikes me as... treasonous. But it appears that negotiators at our government have managed to pay off these people, so that we can get on with the business of paying off Russia for the knives held to our throats.

    Monday, August 22, 2005

    Escape rockets for unmanned satellites

    Re: Is an EELV safe enough to launch people without "man-rating" it first?

    In a May 2003 hearing (before he was head of NASA), Griffin commented “What, precisely, are the precautions that we would take to safeguard a human crew that we would deliberately omit when launching, say, a billion-dollar Mars Exploration Rover (MER) mission? The answer is, of course, ‘none’. While we appropriately value human life very highly, the investment we make in most unmanned missions is quite sufficient to capture our full attention.”

    Since then, he's had a change of heart. NASA's line right now is that man-rating an EELV booster is more expensive than designing a new shuttle-derived vehicle.

    I agree with the change of heart, at least. Unmanned satellites generally don't have reentry and landing systems packaged with them, as manned vehicles must. If a satellite did have a reentry and landing system, for the expensive portion of the satellite, seperately engineered to be fail-safe for other reasons, I suspect the insurance companies would be quite interested in adding escape rockets to the launcher, to recover the billion-dollar-satellite in the case that the $100-million-dollar launcher blows up or simply fails to get it into a reasonable orbit.

    So escape rockets are a good example of something we would deliberately omit from the Mars Exploration Rover. Ironically, the MER does have a reentry and landing system, but one designed to work in the thin atmosphere of Mars. It would have been much different, e.g. heavier and more expensive, if it were also required to get the rover down, safely, into the mid-Atlantic after a failed booster shot.

    Friday, August 19, 2005

    Slime Farms

    The Set America Free folks have the right idea. Their proposal is a series of legislative steps that we can take now that will have the effect of reducing our oil imports through a combination of better fuel efficiency and generation of oil substitutes.

    I'm not 100% in agreement with these folks. They'd still fund hydrogen fuel cell research to the tune of $2 billion over the next 4 years, and they pay lip service to biodiesel research. I'd whack that fuel cell research completely, and put steady money into biodiesel for at least two decades -- $300M/year into biodiesel from crops (this will help work out the bugs in delivering biodiesel through our supply chain and any vehicle use issues), $100M/year into biodiesel from existing microalgae (to develop and debug the infrastructure for growing and processing for millions of tons of algae), and maybe $100M/year to $200M/year into engineered microalgae.

    The oil business is so huge, and leverages such a massive prehistoric biological mechanism, that replacing our oil imports will eventually involve re-engineering our environment in the same way that we have done with building big dams, draining big swamps, and farming the prairie. We are never going to produce meaningful amounts of fuel from farm crops, because there is not enough land, not enough fresh water, and land plants produce too much non-fuel mass to sort through. When Big Oil gets into biodiesel, we'll end up extending Louisiana, Texas, and Florida with dikes extending into the shallows of the Gulf of Mexico. Within those dikes will be massive brackish algae ponds pumped to saturation with the CO2 from coal-fired powerplants. Millions of gallons of oil every day will be extracted from algae separated from those ponds. Environmentalists will be outraged at the devastation wrought on the delicate marine environment. Folks living on those coastlines will protest the change in their views (but will probably welcome the new jobs).

    And negotiations with fundamentalist regimes in the mideast who wish to have nuclear weapons will have a decidedly different tone. Without the U.S. dependent on Iranian and Saudi oil, without their ability to tweak our economy with simple price changes, without the constant flow of Westerners who must tend to their oil fields, without the massive influx of cash that keeps their corrupt governments in power and able to support expensive research into WMDs... things will be vastly different. Conditions will be more like Afghanistan and less like Saudi Arabia. More like Afghanistan but without the subsidized madrasas. But that is their problem, not ours.

    But none of this is possible now because nobody really knows how to grow a lot of algae cheaply, just like nobody knew how to use steam and CO2 injection to profitably leach oil out of a recalcitrant well 100 years ago. It is a U.S. national security priority to develop extensive domestic energy supplies, and that is why the U.S. government should fund biodiesel research. We had a decent program going for about a dozen years, called the "Aquatic Species Program", started during Reagan's tenure, which was canned by the Clinton administration. Here's their report. (300+ pages, check the table of contents and the last couple of sections for the good stuff.)

    So there is a lot of research and development to do.

    I should say that by engineered microalgae, I mean crop development the way it's been traditionally done for thousands of years: grow a lot of algae, select the stuff that produces the most oil, propagate that strain and wipe out the rest. Iterate hundreds or thousands of times. Set up multiple centers across the U.S., so that various strains can be developed independently, optimized for the local environment, adapted to the highly acidic environment we want to grow this stuff in, with different approaches to optimization by different teams. Given the rate at which microalgae grow, I think we should be able to get the iteration time down to a week at maximum. One iteration a day would be significantly better. I'd expect some decent results within a decade. If illiterate people can take wild maize and transform it into corn in a millenium with just one or two crops a year, we can turn wild microalgae into a serious oil producer in a decade.

    I wouldn't hold out much hope for actual genetic engineering of the microalgae. Genetic engineering is good at turning off particular pathways inside cells. It might be useful for adding pathways that wouldn't exist otherwise, say, if you want to produce a particular drug in carefully sterilized bacterial fermenters. But the problem is that any tinkering we do is going to make the resulting species less well adapted to its environment. Algae in the wild live in a very competitive environment. Algae farms are going to be cheap places, not well-controlled places -- we probably can't afford to even put thin plastic film over the ponds to cut down on evaporation and CO2 loss. So we can't protect specially engineered algae from competitors.

    I think there is a lot we can do in the next decade to turn around our crummy national security situation and maybe improve our economy as well. We need to get Congress on board, define the problem, and eliminate distractions.

    Monday, August 08, 2005

    Shuttle replacements

    NASA is mulling two vehicles to replace the Shuttle. Both are based on Shuttle components. This post is really about three things: one, why the proposed NASA designs are about as good as they can do; two, how the proposed designs are worse than the alternatives, and three, what would have to happen for the U.S. to use a better alternative.

    The claimed reason for basing on Shuttle components is reduction of development cost, infrastructure build cost, and time-to-reliability. This last issue is not to be taken lightly -- the flight histories of much of the Shuttle hardware, along with the years of tweaking of that hardware, are irreplaceable. If we're going to launch people on a new rocket, we want to be in a position to say with familiarity that the rocket is safe, and we can only say that about a rocket with a long flight history. Nothing else is going to have a long flight history by 2010. Well, almost nothing, and I'll get to that near my conclusion.

    The other reason for basing the new vehicles on Shuttle components is jobs. The Shuttle program currently employs many tens of thousands of people at NASA and its subcontractors. Those people and their employers want to stay in business, and they have gained quite a bit of leverage on their representatives in Washington.

    Considerations like this are what make NASA's proposed vehicles so sad in comparison to a clean-sheet design. It's not so much that the NASA vehicles are more dangerous or less capable than the alternatives, but that that NASA will do so much less with them than they could do with the alternatives, for the same amount of money. My current favorite clean-sheet design is the one being pursued by SpaceX, and I think it's interesting to compare the two.

    Before I go any further, I should note that unlike NASA and its prime contractors Boeing and Lockheed-Martin, SpaceX hasn't launched any hardware yet (first launch is scheduled for the end of September, 2 months from now). What they do have is 100 or so employees almost all of whom have experience putting stuff in orbit. Assuming SpaceX gets the contract to haul supplies to the International Space Station via their as-yet-unbuilt Falcon V, and assuming they establish regular flights by 2008, they still won't have a long flight history by 2010.

    But back to the comparison. Both NASA and SpaceX are pursuing a two stage to LEO design. Both first stages are reusable (they parachute back into the ocean), both upper stages are expendable, both use capsules to recover the crew and have little ability to return large masses from orbit. All of these are good choices.

    The limitations of the comparison are that the NASA "Stick" design is supposed to lift 20000 kg to the ISS, and the SpaceX Falcon V lifts 5450 kg. So if NASA were to use SpaceX to send people to the ISS, it would have to be three people at a time instead of six, and the capsule would have to be simpler than the full-blown Crew Expeditionary Vehicle they envisage today. Also, SpaceX hasn't yet announced a crew capsule development for the Falcon V. They are going to man-rate the booster, and I think they intend to use it for people after developing a good flight history with cargo.

    Both the SpaceX stages burn liquid oxygen and kerosene. Such engines are well understood, and give predictable, respectable but not spectacular performance. Because the engines are liquid fuelled, they can be throttled and shut down at will. And crucially, kerosene is benign (basically like the gasoline you put in your car) and liquid oxygen is not terribly difficult or expensive to handle. SpaceX uses recently developed materials, manufacturing techniques, and avionics to achieve larger payload per dollar than has historically been possible with this propellant combination. As a result, the SpaceX rocket can be handled by a small team of people and manufactured for small amounts of money.

    NASA's first stage is a stretched version of the solid rocket booster currently used by the Shuttle. That SRB costs about as much to recover, refurbish, and refuel as it does to build a new one, so the reusability is cosmetic. The proposed first stage cannot be shut down early (for instance, if the cabin loses pressure). It cannot be throttled, and the thrust is somewhat unpredictable (which means the whole rocket structure has to be built with more margin to sustain higher peak G and aerodynamic loads, and the upper stage needs more delta-V margin to recover when there is less delivered velocity).

    The SRB is a low performance first stage. It is heavier than the SpaceX hardware: The aluminum-lithium SpaceX booster has a mass fraction of 94%, where the steel SRB has a mass fraction of 85%, and the SpaceX booster has a higher exhaust velocity, 2980 m/s versus the SRB's 2636 m/s (measured at sea level air pressure). The result is that the SRB has to be much bigger per kg of payload as the SpaceX design.

    There is a school of thought in the rocket design community that espouses the Big Dumb Booster. Their point is that a larger rocket is just fine, so long as it costs less. Cost is mostly related to things other than size, like the number of people necessary to build, transport, and launch the rocket. But the Shuttle SRB is so big that its size implies complexity. Pouring single grains of propellant that large requires enormous facilities to mix and cure the components. The entire SRB is too large to pour or transport as a single piece, so it is poured as four pieces, seperately transported to Cape Canaveral, then assembled there. And while the clevis and tang joints between the sections have now been sufficiently engineered to be safe, they impose handling restrictions (NASA cannot leave the Shuttle out in the cold), and cost more money.

    As a result of all this complexity, each Shuttle SRB costs $40M per flight (that's half of the first stage, with no guidance or communication system). A two-stage SpaceX Falcon V sells for $15.9M (that's everything but the capsule on top) [number has been updated - thanks, Jon]. For a sense of how cost scales with size, note that the Falcon V lifts almost ten times the payload of the Falcon I, but costs a little more than three times as much. Each SRB has a bit more than 7 times the thrust of the Falcon V first stage.

    NASA faces a difficult choice for the upper stage. There is only one man-rated engine suitable for upper-stage use in production in the U.S., and that is the Shuttle's SSME. That engine is complete overkill for an upper stage engine, because it's designed to work in the lower atmosphere too, which makes everything more complicated. Throwing it away each flight will cost a lot. Any other engine (i.e. the in-development Cobra or the in-production RS-68) will require at least some development money and time to certify as man-rated, but will cost less per launch.

    All the engines NASA is considering for the second stage burn both liquid hydrogen and liquid oxygen. This decision alone pushes the cost of the NASA solution far away from nearly anything else. LH2 will give better performance than kerosene (4300 m/s exhaust velocity versus 3330 m/s, measured in a vacuum), and thus a smaller rocket, but the relevant difference is cost. NASA can't go with a lower cost propellant combination because there are no US-manufactured man-rated engines which burn anything less costly.

    Now that we know why NASA is mulling an expensive crew vehicle, and what a less expensive vehicle looks like, and interesting question is, how could we end up with the cheaper alternative? I assume, in particular, that the SpaceX honchos think about this problem relatively often. I also think that Michael Griffin, the NASA chief administrator, thinks about this fairly often as well.

    It's a political problem. NASA has to get crews to the international space station after the Shuttle is retired. The Russians have complained about being solely responsible for launching crews for the last few years, but that is because we weren't paying enough for the launches. If we were willing to pay, the Russians would be happy to provide launch services (they recently asked for $63M per launch). They have a very dependable launcher, which costs a fraction of a Shuttle launch. Buying time to design and build a better, cheaper U.S. launcher would be cheaper than building the stopgap crew launcher currently envisaged.

    We would then be faced with the smaller problem of launching the ISS portions originally intended to go up on the Shuttle. Both EELV boosters have the mass capability to launch these cargoes (though NASA would have to rework each piece to sit in the EELV payload fairing rather than in the Shuttle payload bay). EELV launches are expensive (around $254M), but they're half of a Shuttle launch, and don't endanger crews.

    Michael Griffin is going to take the expensive but politically necessary route. He'll pay the big NASA prime contractors many billions of dollars to develop a stopgap launcher, while ensuring that SpaceX and perhaps t/Space and Kistler get sufficient funding to get launch histories. Eventually, perhaps after his tenure, it will become clear that the startup U.S. launch companies are safe enough and obviously cheaper enough to mothball those horribly expensive launchers. This comparison will have to be painfully real, immediately obvious, and undeniable. Only then can the NASA prime contractors be fired and the money formerly used for their support used instead for space exploration.