Neal Stephenson On Rockets and Innovation

Dr. Gamera writes "Science-fiction author Neal Stephenson gives us his perspective on the history of the development of rocketry. He uses that history to illustrate the phenomena of path dependence and lock-in."

Comments

Why not, indeed?

[rickb928]

Stepheson makes this point late in the article:

"There is no shortage of proposals for radically innovative space launch schemes that, if they worked, would get us across the valley to other hilltops considerably higher than the one we are standing on now—high enough to bring the cost and risk of space launch down to the point where fundamentally new things could begin happening in outer space. But we are not making any serious effort as a society to cross those valleys. It is not clear why."

It's somewhat clearer why, to me.

I want to buy a more fuel-efficient car, and keep my current, less-efficient car. My current car is useful for many things, but commuting to work could be done by another, more efficient one. Here, however, is the rub. Despite the improvement in fuel economy, it is still a net increase in cost to me for a fairly long time. Acquisition, insurance, and upkeep consume most of the fuel savings. Yes, it would be better for he environment also, but that doesn't immediately or directly impact my costs very much. So I put off buying that car.

Our current methods of delivering object into space work well enough, and the alternatives are both unproven and not sufficiently advantageous to warrant immediate adoption.

However, as we re-enter manned space exploration, we will be looking for heavy-lift options that don't actually exist today, and those present the opportunity to develop new methods. Avoiding the vertical portion of a rocket launch also avoids the need for massive thrust to overcome gravity that directly. Stephenson alludes to this, and 'space planes' are the current focus, along with some multi-mode concepts. NASA'a failing Ares program is a fair example of lock-in that Stephenson is writing about. Being more open to the development of ultra-high-speed vehicles and their engines might offer both better alternatives and true advances. But that takes ingenuity and a willingness to risk that NASA doesn't seem to possess right now. Bad climate to propose trillion-dollar space programs, though we've been willing to propose trillion-dollar stimulus packages for more mundane projects, such as propping up failed financial institutions.

Imagine the impact of a trillion-dollar space plane project. Would US students consider a career in engineering if they saw both the opportunity to be part of a cool new future, and the employment options as well? Would this give US aerospace companies something else to sell instead of weapons systems, and is that a good thing? Would it spur international competition, and is that good? Would it divert China's resources into something besides crushing the world's manufacturing competitors? Does that matter? Would a trillion dollars given to this project do more good than giving it to the bankers? Will the bankers also flourish in the glow of this project?

Why aren't we trying something new? No unobtanium

[edremy]

Alternates fail simply due to the lack of materials.

• Spaceplane? The Lockheed VentureStar fits all the bills- except that there's no tank material that can hold LH2 at the needed temperatures and still be light enough to get to orbit on a single stage.
• Elevator? Unobtanium all the way. Some theoretical studies show that carbon nanotubes *might* have the needed tensile strength, but given that we can't reliably grow flawless ones a millimeter long the 22,000 mile thing is a bit of a tough problem.
• Big gun? Workable, but you can't send anything fragile, including people

I think if he looks a bit more deeply it has very little to do with lock in and everything to do with the fact all the wonderful SF ideas out there simply can't be built with our current level of technology.

Physics

[RogerWilco]

I think the article is ignoring some basic physics that has driven us to these outcomes, both his rocket and his oil dependency example.

To get anything into orbit needs a very good weight/energy ratio. The only thing that can provide this itself are your typical rocket fuels. There's two other options:

- Atomic: this usually goes out the window when you consider manned vehicules due to the weight of shielding, and for unmanned vehicules the environmental effects.

- Cheat by leaving a significant part of your mechanism on the ground. Space cannons, magnetic rails and the like. The problem here might indeed be one of technology. even a very fast car (Thrust SC2), might go about at the speed of sound. Sounds pretty fast? It's still nowhere near enough what you'd need. The escape velocity is about 11 km/s, the speed of sound about 300 m/s. Now we need to think in energy, so we need to use E = 1/2 mV^2. Or in other words we need to compare the square of the velocities. 300^2/11000^2 = 0.00074 or about 0.075% of the energy required.
Going much faster and the friction with the atmophere melt your vehicule.
So to get anywhere with a space cannon type system, it needs to be on a very high platform, probably 10km or more, and then be big enough to accellerate a payload to 10-20 times the speed of sound.

When you look at the basic physics, you very quickly end up with rocket-like devices.

A similar thing holds true for our dependency on oil. It again boils down to weight/energy ratio, but with much bigger safety, usability and logistics constraints.
The math is not as straigthforeward, as it's mostly economics, but only rocket fuels give much more power to weight ratio then the conventional fossile fuels.

Re:Physics

[slashqwerty]

Now we need to think in energy, so we need to use E = 1/2 mV^2. Or in other words we need to compare the square of the velocities. 300^2/11000^2 = 0.00074 or about 0.075% of the energy required.

The big problem with rockets is that the fuel has to travel with the vessel. I haven't done the math but I have heard roughly half of the fuel is spent accelerating the other half to the speed of sound. If you have a land-based system that accelerates the vessel to the speed of sound you can make the vessel half the size (or replace half the fuel with payload).

Speaking of the fuel, most of the weight comes from the oxidizer. With a hydrogen-oxygen rocket you need one oxygen atom for every two hydrogen. Oxygen has an atomic weight of 16 while hydrogen has an atomic weight of 1. So 89% (16/18) of the mass is oxygen.

Imagine if you had a railgun that accelerates a ram-jet past the speed of sound, the ram-jet burns oxygen from the air and accelerates to nearly orbital velocity, finally a rocket takes over to reach orbit. If we could get that working we would have much better access to space.

It is worth noting Burt Rutan uses a mother ship to launch his space craft. The mother ship gets up to speed by burning oxygen from the air in standard jet engines. The spacecraft then drops off and launches with a substantial head start.

Re:Stephenson & Rocket?

[zrbyte]

It's also worth mentioning here that science and technology has some "Tahrir square moments", that nobody expects. The paradigm shifts and disruptive technologies. 20th century physics and technology is full of these moments. These have the strength to break through the "lock-in". Oh and most of the disruptive ideas etc. have come from the "developed world" of the day. Quantum mechanics and internet? Come on Neal, gimme a break.

Just another example, regarding the "globalization effect" he's talking about: Thorium based reactors that the US doesn't give a rat's ass about, but may well play a major part in solving the energy crysis and how China is thinking about building them.

Re:Odd, unsatisfying conclusion

[Rei]

Even in theory, "maybe". The strongest single SWNTs measured thusfar are just over 60GPa, a far cry from the predicted 120+ GPa. That may sound like a small difference, but the taper factor means that's a geometric increase in the mass of a space elevator; you really need at least 100GPa for the bulk fiber for it to be even worth consideration. And that's for *bulk fiber*, not for individual tubes, which are always going to be a lot stronger than a bulk fiber.

Plus, space elevators have all sorts of other problems -- inefficient power transport, slow transit times and thus throughput, major undampened oscillations, and on and on. Launch loops are a much better choice in pretty much every regard, and could be built with today's materials and technology. Oh, sure, they're not as glamorous, not as much a staple of sci-fi. But that doesn't change what's the best way to get into space.