Which was bill's point: getting to 50/lb is easy. All you have to do is
achieve commercial aircraft levels of reuse and operations. And stop using
expensive fuels.
On Sep 21, 2016, at 8:02 PM, Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
On Wed, 21 Sep 2016, David Gregory wrote:
Indeed the Falcon 9 propellant cost comes in at about $40/lb of payload with
expensive RP. Commercial airlines do about 50% of their costs as fuel.
It's more traditionally quoted as "operating cost three times fuel cost", and
even that can be low depending on which year you're looking at and what you
include. It's some small multiplier, anyway.
Moreover, rocketry ought to be *better*. Magically doubling the fuel
capacity of an airliner would not double its operating costs; a lot of the
non-fuel part is fixed overheads, or multiples of *dry* mass, that don't
scale much with fuel use. And our vehicles are far more fuel-intensive than
airliners, so fuel ought to be a larger part of our costs. Max Hunter
thought that rocket vehicles ought to be able to operate at circa 1.2x fuel
cost eventually.
However, it's abundantly clear that we're a long way from that operating
regime. Launch costs are overwhelmingly dominated by overheads and ops
manpower (and replacement of expendable hardware); fuel costs are down in the
noise for any launcher except maybe a few oddballs. (Twenty years ago, Jeff
Greason's analysis said that Titan IV was the only US rocket whose fuel cost
was actually noticeable. Today, hmm, perhaps Delta IV, because of all that
LH2, although that's nowhere near as costly as solids and toxic hypergolics.)
Fixing this requires reusable hardware, much-less-manpower-intensive launch
operations, and much higher launch rates (so fixed overheads don't dominate,
as they do for *anything* that flies only a few times a year).
Henry
