Monday, September 22, 2014

Stepping stone is earth-centric thinking

Jeff Greason, in a great talk on space settlement that everyone should hear, calls it the island hopping approach but it's the same thing.

Often you do have to take a breather, regroup and marshal your forces before moving on and space does require some of that. The difference is lack of friction. Bodies don't stay in motion on earth as they do in space. Stepping stones in space can make it harder to make progress rather than easier. Not just harder but hinder. When you are absolutely certain about how things should be done, along comes somebody with blitzkrieg to show the fallacy. Jeff knows his history.

Delta V is a big thing in space. Small is better. Stepping stones increase it along with costs, including opportunity cost. My belief is that the opportunity cost to the next century is huge the longer we delay establishing an independent industrial colony on mars and there is really nothing preventing us from doing it now with just private funds (if non-private funds are available it may be foolish not to take advantage.)

If mars were a step too far, that would be an issue, but it's not. There are steps, but we should not add any that are not going to make it cheaper or easier. Many don't while sounding like they may.

There are three ways to get to mars. One step, two steps, or three steps.

MCT is one step approach. Launch direct from earth to the surface of mars.

Two steps would be either going directly to mars orbit then transferring to landers; Or, go from earth orbit directly to the mars surface.

Three steps takes you to earth orbit and refuel, then mars orbit to transfer to landers.

Stepping stones are four or more steps of uncertain duration putting a halt to actually learning how to live on mars. We have wasted enough time and money already. Even Jeff would admit the cost of these islands. Unresolved is the question of if they would save money down the road. I believe there is no question that they will cost us time (especially if I'm correct about opportunity costs.)

Of course, if mars colonization is not an objective, we'd have to revisit this speculation. Island hopping gives me the uncomfortable feeling that it's more about dividing up the pie than accomplishing settlement.


Joseph said...

Well... It depends on what you're lacking. If delta-V is limited then stepping stones don't make much sense but if mass is limited, they do.

ken_anthony said...

Thanks for your comment Joseph. Let's clarify 'mass is limited.'

Delta V is limited by specific impulse and quantity of fuel. If you refuel in space Delta V is never limited.

I assume you are referring to fuel mass rather than ship mass. Ship mass should be limited. At this stage there is absolute no reason for a ship to mass more than what today's LV can lift to LEO. With refueling fuel mass is not limited because you don't need massive structures in space just to hold fuel.

So stepping stones make no sense now. They do when economics comes to play with greater markets. Which both a colony and ship refueling provides.