Mass Paradigm

October 21, 2014 1 Comment

One of the most interesting things to think about with respect to the near-future of space travel is the removal of limited mass as a paradigm. That is to say, right now the predominate design constraint for spacecraft is mass, because rockets are very expensive, so each kilogram of payload must be put to best use. Unfortunately, this means that the design and construction costs for spacecraft are very high, as much effort is put towards shaving off grams by using exotic materials and efficient designs.

But soon the current launch vehicle renaissance will result in launch costs low enough to demolish the limited-mass paradigm. There is a tipping point where it is economical to cut design costs and take the hit on launch costs. There will also see a growing emphasis on tough and reliable systems that last a long time, rather than fragile, light, efficient systems. Combined with lower fuel costs from asteroid mining and improved refueling technologies, the predominant modus operandi will be repairing spacecraft rather than replacing spacecraft. Designing for reusability and, more importantly, refurbishment will be critical.

We’re already seeing a shift towards this paradigm with SpaceX. Their launch vehicles use redundant systems to make up for their cheaper designs — their avionics electronics, for example, are not rad-hardened but instead redundant in triplicate. The mass penalty is minimal, however they also make up for it by using modern electronics concepts. For instance, instead of running numerous copper wires up and down the length of their rockets, they run a single ethernet cable and use a lot of multiplexing.

This kind of change is just the beginning, however. There will be a time when it makes sense to loft a big bundle of steel rods into orbit and have workers weld them into a frame for a spaceship. This has a number of benefits: the frame doesn’t have to be fit into a fairing, it can be reconfigured on the fly, and it doesn’t have to endure the acceleration and acoustic stresses of launch. Additionally, lifting big bundles of steel makes best use of the volume in a launch vehicle fairing.

I think the only two questions about the future of space travel are: How much will it be dominated by robots? and Where will the money come from? But those are questions for another time.

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On the SLS

February 7, 2014 Leave a comment

NASA has always built its house on political sand, not rock. While they can get lots of funding at the political high-tide, they can also get bogged down to failure. For instance, the ill-fated Space Shuttle program (or STS) was a result of shifting goals and influences on design from disparate sectors.

Similarly, the new Space Launching System (or SLS) is the brainchild of political forces. Its first stage is an extended Space Shuttle External Tank, and its first-stage engines are Space Shuttle Main Engines. Its solid boosters are STS-derived. This means that most of the STS tooling can be kept, and thus constituencies keep their jobs. I have to admit, this re-use reduces design times, but it is not the most efficient way to build a heavy launch vehicle, especially since the technology is more intricate than it needs to be (jacking up production costs).

The SLS is designed to launch the Orion capsule, which was designed as part of the under-funded Constellation program. The Orion spacecraft uses the Apollo architecture, and NASA helps this comparison by painting the SLS with white-and-black roll patterns reminiscent of the famous Saturn V rocket. Combined with the use of STS systems, the SLS threatens to become one big nostalgic mash. Unfortunately for NASA, this means its shortcomings will be overlooked in the future, much like the Space Shuttle program.

For instance, nobody is quite sure what to do with the damn thing after we’ve designed and built it. NASA has recently released that instead of a circum-lunar flyby, the first manned mission of the Orion/SLS will visit an asteroid that will be tugged into orbit around the Moon. After that, everyone seems to throw up their hands and say, “Mars? I guess?”

Criticisms aside, its good that we are developing any sort of heavy-lift manned capacity, because eventually it will enable deep-space missions. I’m just worried that the SLS program isn’t coherent enough to survive shifts in funding or vision. Not that NASA is particularly gifted in either of those departments. With their limited funding, I’m more interested in their robotic missions (or potential thereof — submarine to Europa, anyone?), because any manned program in the near future will consist of paddling around in the metaphorical kiddy pool.

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Say “No” to Manned Spaceflight

January 7, 2014 Leave a comment

I like the idea of people walking around on other planets as much as the next guy, but at the end of the day I can’t go away with a clear conscience without making this point. There is no reason for a manned space program, either now or in the immediate future. In fact, it would be quite irresponsible of us to go mucking around on other balls of dirt.

Much like the archaeologists of the past who used ancient scrolls to keep their fires going, any serious presence or in-situ resource utilization could be inadvertently destroying priceless research subjects. Imagine if we started harvesting ice from asteroids, and then discovered that very old ice tends can contain detailed records of proto-stellar conditions in the Solar System. Even things like rolling robots across Mars or slamming probes into the Moon are calculated risks. We’re pretty sure we won’t mess up anything important, but we aren’t sure. Paradoxically, we can’t be sure what we’re missing without taking some of these risks.

Nonetheless, sending advanced primates to do the job of fast, clean, accurate robots is as irresponsible as it is stupid. Animals are hosts to trillions of bacteria, and if even one strain gets onto the surface of Mars, say, and adapts to the not-so-inhospitable conditions, it’s all over. We rely on the hard vacuum of space to kill off any potential infection vectors on robotic spacecraft, but we can’t do the same for humans. If we’re going to be sending humans to any place remotely capable of developing life, we need to be almost 100% sure there is no life there to begin with, or that the presence of invasive species of bacteria won’t eliminate it.

Even if we make sure to within reasonable doubt that there is no longer or never was life on Mars, we might be screwing ourselves in the long run by sending humans to colonize. If a mutant strain of bacteria spreads to cover the planet like the stromatolites of ancient Earth, and starts eating up what little oxygen is left, then any terraforming efforts could be foiled before they begin. Imagine if our engineered bacteria produces oxygen as a byproduct, and a rogue strain works in the other way. We’d have created a widespread stable ecosystem that leaves us asphyxiating out in the cold.

The two arguments in favor of long-range manned spaceflight have never held much water for me, even if I wanted them to. First, the “putting our eggs in one basket”. Now, current manned spaceflight has nothing to do with the colonization of space. If we were serious about spreading a permanent, self-sustaining presence to another planet, we would have to completely reorganize the existing attitude and institutions surrounding manned spaceflight. Currently, the world’s collective manned spaceflights are a road to nowhere. The ISS is a good sandbox for learning about long-term missions, but we don’t really use it like that.

The second argument is economic. I’ve gone over this is previous posts, but the short of it is that it will be a long time before its profitable to go off-world for resources — unless, that is, there is an exterior source of funding. It’s conceivable that a mild industry might build up around mining space ice for fuel and 3D-printing components. However, at some point funding has to be provided by someone interested in scientific exploration or the intrinsic value of space exploration. A self-contained space economy with Earth as the main buyer is not viable. Perhaps there exists a chicken-egg dilemma: a permanent off-world colony needs industry to survive, and industry needs off-world colonies to thrive.

That’s the cold, hard reality of the matter. I don’t want to have this opinion, but avoiding the truth about manned space exploration isn’t doing anybody any good.

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