$\begingroup$ @RussellBorogove Yes, I agree. I was (attempting to) address the "fact" that it is 'sold' as a 'spaeplane' but not as a planetary surface craft - as addressed in the discussion to the question re possible voting to close. On Terra the wings are "useful". On Mars, hardly at all. On Mercury, not at all. On Venus you don't want to find out :-) - but you can easily go there and back again (with or without Hobbits). I have not looked at how short an eg Mars return may be achievable pulling its max 2g each way for as long as possible on the available high Isp fuel capacity, but ... :-) $\endgroup$ – Russell McMahon May 28 '19 at 21:57