In article <
dc17b34b-0dd5-486c-8333-0a9e42595d9f@googlegroups.com>,
pedro1492@lycos.com says...
On Wednesday, November 23, 2016 at 2:26:32 AM UTC+8, David E. Powell wrote:
http://lunar.xprize.org/news/blog/weekly-space-news-spacex-test-mars
<http://lunar.xprize.org/news/blog/weekly-space-news-spacex-test-mars>
The big unanswered question, for me, is how to get the rocket up off Mars again? Leaving the Moon to return to Earth was doable in 1969 because of the low Lunar gravity. While Mars' gravity is not as high as Earth's, it is a lot bigger than the
gravitational pull of the Moon is.
Presumably it will require several trips to send the life-support and
return rocket. Then if all the bits land safely on Mars, you can send
a few humans up.
In Musk's plan, the vehicle to get you there is the return vehicle.
What you need to send first is the propellant factory and power plant
which turns CO2 from the atmosphere and H2 brought from earth into LOX
and liquid methane. The LOX and liquid methane refuel the ship for the
return to earth.
Later missions could use locally found water instead of bringing H2 from
earth. But early missions likely won't want to depend on finding water.
Jeff
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