In article om,
says...

On 2016-01-04 16:16, Fred J. McCall wrote:

The salt water and that the heat shield apparently isn't as good as
what's being used on Dragon V2. Dragon V2 is supposed to be able to
fly 10 times or so before it needs major refurbishment.

I was under the impression they'd be spraying a new ablative heat shield
before every flight ?

Nope, should be good for 10 flights without *any* refurbishment. Here
is a quote from Elon (made at the Dragon V2 unveiling):

How many flights can Dragon v2 fly without any refurbishment?
We're aiming for ten flights without any significant refurbishment
and then the thing that would have to be refurbished is the main
heat shield, but that remains to be seen. The heat shield material
is called PICA-X version three, which is a phenolic impregnated
carbon ablator. With each version we've been able to reduce the
amount of recession that occurs in the heat shield. You can think
of the heat shield like it's a giant brake pad, basically. The
better that material technology gets, the more uses it can go
through - just like a brake pad on a car, eventually it does need
to be replaced, but I think we can eventually get up to, maybe,
100 flights or something like that.

Is there a point in making the shield thick enough
for 10 flights since that is bound to add weight to the capsules for the
early flights ? (why carry the portion of the blative shield that will
be used 9 flights later ?)

Minimizing mass to razor thin margins is the "old space" way of doing
things and tends to be rather expensive. SpaceX does not do that, which
is why Falcon 9 is sized quite a bit bigger than it needs to be. The
extra size allows the first stage to land at the launch site. An "old
space" engineer would see this as waste, but then an "old space"
engineer was never concerned about the economics of reuse.

How hard do you think the thing is hitting? They'll make them
reusable by designing it in at the start. They land under power. How
much 'structural impact' is there to airplanes landing on land?

Plane lands on tires on runway with shock absorbers and at a very low
descent rate.

Unless they land on that mattress factory in Gotham City (the one that
allowed Batman and Robin to land safely after their helicopter failed),
there is bound to be some shock and scrapes as it touches ground. When
you look at soyuz, they need perfectly contoured seats for each occupant
to widthstand that landing.

Wrong.

Or will dragon have much mreo powerful landing rockets to provide
smoother landing ?

Completely different than Soyuz. Soyuz fires small rockets to cushion a
parachute landing. During a nominal landing, Dragon V2 will land under
power using the Super Dracos and the parachutes will *not* be deployed.
The landing should be quite gentle for Dragon V2 because of this.

The Super Dracos are powerful enough to double as launch escape rockets
in an emergency. Don't you remember the Dragon V2 launch escape test?
That thing took off of the ground like a banshee (under Super Draco
power), deployed its parachutes, and safely splashed down in the ocean.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer