In article ,
says...

Jeff Findley wrote:

In article ,
says...

But the current thing is a diversion from going to Mars since NASA is
developping stuff that won't be of use to Mars, and hasn't yet
developped a plan to get to Mars, and hence can't begin to implement
that plan.

I'm still not convinced NASA is going back to the moon. SLS hasn't been
canceled yet to free up the funding to design and build a lander.


What good is a lander if they cancel the rocket that is supposed to
get them there?


We don't need SLS at all if we do EOR with in orbit refueling.


But now you're talking additional launches, which runs the price up.
And you still need a really high energy upper stage to send the whole
works somewhere.

Falcon Heavy's launch costs are ridiculously low. Also SpaceX has a
launch cadence for Falcon 9 that's 10x that of SLS's predicted maximum
launch cadence. By the time SLS flies with humans on top, it wouldn't
surprise me if SpaceX had its Texas launch site operational, giving it
even more launch capacity.

The "additional launches" problem simply won't be a problem in a few
years, unless we stick with the max two launches per year SLS.


Falcon
Heavy ought to be able to loft a quite capable lunar lander. ULA ought
to be able to provide ACES upper stage(s) needed to get the stack to
lunar orbit. Either Boeing or SpaceX can provide the space "taxi". SLS
is just sucking up resources better spent on actual missions.


I'm going to use payload to trans-Mars Injection, because those are
the only 'constant' figures I have. Falcon Heavy is 16.8 tonnes to
TMI. SLS Block 2 is 45 tonnes to TMI. None of the ULA launchers give
either TLI or TMI figures, however, none of the come close to the LEO
capability of Falcon Heavy so it's a fair bet they'd be well under
that trying to boost to someplace farther out. BFR is in a class all
by itself, of course, and will probably be ready before the DSG is
done. Dragon V2 is around 10 tonnes with a 1 week duration, so Falcon
Heavy could certainly send that to the moon. It can't land, though,
because it doesn't carry enough fuel (only about 1.5 tonnes of fuel).
Falcon Heavy doesn't have enough grunt to send an Orion stack to the
Moon, much less an Orion stack plus a lander.

The other possibility is Falcon Heavy with the (now downsized) Raptor
powered upper stage. That would most certainly do the job. SpaceX has
been getting USAF funding for this:

Air Force adds more than $40 million to SpaceX engine contract
by Jeff Foust, October 21, 2017
http://spacenews.com/air-force-adds-...ion-to-spacex-
engine-contract/

From above:

Musk said in his IAC presentation that the engine will now
generate about 380,000 pounds-force of thrust

That's a bit more thrust than the J-2X which was rated at 294,000 lbf
thrust. One J-2X would have powered the Ares V launched EDS, so a
single Raptor engine powering a Falcon Heavy upper stage ought to be
quite impressive.

The conclusion is that you sort of need SLS or something with similar
capability. It may be a poor design and expensive, but it's what
there is.

We'll have to agree to disagree. By the time SLS flies, either SpaceX
or Blue Origin (which already has a high energy LOX/LH2 engine) will
have fielded launch vehicles capable of replacing SLS, as long as NASA
doesn't deliberately design a lunar lander "too big" for them, just like
Mike Griffin did for CEV/Orion.

Jeff
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