Nels:
Careful. Cost will *eventually* be dominated by propellant, but it is very
unlikely any rocket being built today will still be operational when that
day arrives.
Further. the relative cost of kerosene and methane today are no basis for
estimating which to choose for a century from now.... Propellant choices
today ought to be made based on today's economics; if we assume that is
what is occurring, then methane is being chosen over kerosene today because
it confers some advantage, today.
Or it could just be fashion....
Bill
On Mon, Feb 12, 2018 at 2:16 PM, <Nels.Anderson@xxxxxxx> wrote:
Gesendet: Montag, 12. Februar 2018 um 04:04 Uhr
Von: "Henry Vanderbilt" <hvanderbilt@xxxxxxxxxxxxxx>
I take both SpaceX and Blue's methane plans as primarily reflecting
long-term plans for refueling with in-situ propellant sources.
As you point out, performancewise methane versus kerosene is a wash.
At the IAC, Musk has indeed made clear that ISRU is one of methane's major
advantages. But I wouldn't imagine that's such a big factor for BO, which
has had little to say about Mars and is interested in hydrogen too. My
guess is that methane's chemical stability (you can't do FRSC with
kerosene) and low viscosity are significant factors. Musk also seems to
think costs could ultimately be dominated by propellant, in which case
methane beats kerosene.