Kuznets>> а почему?
Старый> Потому что метан не имеет преимуществ перед керосином.
я почему спрашиваю,
It would not really make sense to leave your spaceships on
Mars; you would want to build a propellant plant on Mars and
send the ships back. Mars happens to work out well for that
because it has a CO2 atmosphere, it has water-ice in the soil,
and with H2O and CO2, you can produce methane (CH4) and
Picking the right propellant is also important. There are
three main choices, and they each have their merits (Table 4).
First, there is kerosene, or rocket propellant-grade kerosene,
essentially a highly refined form of jet fuel. It helps keep the
vehicle size small, but because it is a very specialized form
of jet fuel, it is quite expensive. Its reusability potential
is lower. It would be very difficult to make this on Mars
because there is no oil. Propellant transfer is pretty good but
Hydrogen, although it has a high specific impulse, is very
expensive, and it is incredibly difficult to keep from boiling
off because liquid hydrogen is very close to absolute zero as a
liquid. Therefore, the installation required is tremendous, and
the energy cost on Mars of producing and storing hydrogen
would be very high.
Therefore, when we looked at the overall system optimization,
it was clear that methane was the clear winner.
Methane would require from 50% to 60% of the energy on
Mars to refill propellant using the propellant depot, and the
technical challenges are a lot easier. We therefore think
methane is better almost across the board.