In article ,
says...

On 2021-04-18 07:26, Jeff Findley wrote:

Lunar Starship still need Raptors to get into earth orbit and to perform
the TLI burn.
Likely possible, but surely inefficient due to cosine losses.


Since it would this only once, and never need raptors again in its
Gateway-Moon trips, is this inefficiency for that once in a lifetime
worth not having to haul the raptors and refocus the tanks on those new
side thursters?

Almost certainly, otherwise SpaceX wouldn't do it. And SpaceX does
propose reusing lunar Starship by refueling it in high lunar orbit.
Cite:

MAY 01, 2020 - NASA SELECTS LUNAR OPTIMIZED STARSHIP
https://www.spacex.com/updates/nasa-...ized-starship/

From above:

A lunar optimized Starship can fly many times between the surface
of the Moon and lunar orbit without flaps or heat shielding
required for Earth return.

On the other hand, once SLS is killed, SpaceX can turn Lunar Starship
into both the lunar lander as well as the Earth-Moon flight at which
point you need the raptors to land back on Earth. (and with tiles etc).

The possibility of being able to replace SLS for Earth-Moon transit is
likely why SpaceX won over the other more specialized solutions.

That's not correct. There have been articles published talking about
the selection.

The other two had serious problems with their proposals. Blue Origin's
proposal was disqualified because they essentially asked for payments
before reaching milestones (not allowed). Dynetics changed their design
to eliminate the drop tanks on their lander which caused it to be
overweight so that the design didn't close.

Also, the SpaceX proposal was the only one that fit the paltry HLS
funding that NASA is currently getting from Congress.

Lunar Starship development is just a variant of the Starship that SpaceX
is currently developing on its own dime.

But the lunar mission doesn't require landing on earth. It requires real
landing legs to land on uneven terrain. Totally different engines for
landing on moon.

A lunar landing Starship doesn't require it. But it will never get to
high lunar orbit without being refueled. And the tanker Starships need
to land on earth so they can be refilled and launched again. So the
program does require full reuse of both tanker Starship and Super
Booster.

So there are diverging priorities from the current
Starship development.

Disagree. Starship is more than just lunar landing Starship. You need
a tanker Starship to actually fly lunar landing missions, so earth
landing is still the #1 priority of Starship development.

Will be interestng to see how far the current iterative tests go before
we start to *see* lunar models being tested. I get the feeling that the
lunar model isn't getting "iterative design" and they'll do more
conventional engineering and design to work instead of test until it
works. For one thing, if they can't simulate moon landing, they can't
really do iterative design.

They can test all the components on earth and then fly an uncrewed lunar
landing test, which is in the NASA contract. Next they would fly a
crewed lunar landing test, which is also in the NASA contract.

Vertical landing of lunar landing Starship isn't a big unknown. Many
different vehicles have landed on the moon.

Big question is whether the lunar landing legs will be same or very
similar to the ones for landing on Earth, or totally different. (lunar
legs don't worry about re-entry so could be attached to the outside so
they can have greater span for stability when landing.

See the renderings on the SpaceX website.

Jeff

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