The Reference Mission

This blog will talk about what it would take to go to the stars.   The intent is to explore what it would take using current physics -- though perhaps more advanced technology.  This first article discusses our reference mission.   Here we are discussion 'going' to the stars, i.e., a mission that might establish a human -- or perhaps post-human - presence.  A simple reconnaissance by some tiny capsule doesn't qualify though doubtless it would precede any mission of the type we discuss here.

There are three basic quantities we need to define for our reference mission:  what are we going to deliver, how far away is it going and how long will it take.   I define the reference mission in terms of three numbers:  the mass, M, for the payload; the distance, D, of our target and the time T for the total mission.

For our reference mission, I take M to be 1000 tons, or about 2 1/2 times the weight of fully loaded 747.  This is a significant mass, but it seems very unlikely that using anything derivable from conventional technology is going to let us do with less.   It's certainly true that we can pack a lot into today's machines, but the facilities that we use to create microchips aren't small, so it's a bit early to assume we can make van Neumann machines. So we have M = 1000 tons or 10⁶kg.

While it might makes sense to use the actual distance to Alpha Centauri (a bit over 4 light years or 1 and a third parsecs) to get the make things easier, we'd have to be pretty lucky to get an appropriate target planet there.  To give us a little bit of choice, lets try 10 light years or about 3 parsecs.  This corresponds to just about D=10¹⁷ meters.

Finally how long can we allow for the mission...  If we ask how long the largest engineering projects last we have examples of cathedrals being built over centuries, but typically that was in fits and starts. Just a few days ago though we had an example of LIGO which was developed over more than 40 years before detecting gravitational radiation. So lets take a factor of two more, or about 100 years as the duration of our flight. Particularly if we need to rely upon any support infrastructure from Earth this seems reasonable. With only a bit of advances in biology it corresponds to about 1 human lifetime. My expectations are that most if not all of any crew will not be active during the flight -- our 1000 tons will seem very small  then.  So we have 100 years or about 3 billion seconds.  T = 3 x 10⁹ seconds.

So the reference mission is

    Mass: M = 106kg
    Time: T = 3 x 109s
    Distance: D = 1017m