inching.
  *moving slowly/small degree of progress.*

As in “Elon is *inching* his way towards Mars”. 

“Metering closer to his goal” sounds … totally off. So how do I avoid using arguably antiquated measurements (which has [contributed towards the loss of one space mission][1]) without sounding totally crazy? Are there equivalent expressions using metric units, or do we need a work-around, or ...?

[1]: http://edition.cnn.com/TECH/space/9909/30/mars.metric.02/