Methane is simpler in some ways -- no helium, for example. The big question marks here are composites and aerospike. Aerospikes have been tested but have not (

Methane is simpler in some ways -- no helium, for example. The big question marks here are composites and aerospike. Aerospikes have been tested but have not (as far as I know) flown. Composites haven't flown at this scale as far as I know. So yeah they have their work cut out for them! BTW: SpaceX has done some revolutionary things around reusability, but I mostly agree -- other than their reusability efforts everything else they've done is good old fashioned rocket science + cost control.