Mass Paradigm

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.