If I understand correctly—which I am not certain I do—the upper stage has a
delta-v capability of about Mach 22, not including landing propellant.
That would appear to explain the trans-pacific sub-orbital capability and
the ability to conduct a lunar landing and return if fully fueled in LEO as
well as being consistent w/ a LEO SSTO capability w/o recovery (because the
landing propellant is consumed on ascent).
Assuming that about a third of the first stage propellant is used in
fly-back and landing, it appears that the first stage has far more
propellant than required to get the upper stage to Mach 3-4 condition
needed to get to orbit empty. Thus it appears that the first stage is
sized either for a much higher overall delta-v than is required to reach
LEO or is intended to place the upper stage in LEO with significant
propellant reserves.
Bill
On Mon, Sep 30, 2019 at 10:40 AM Robert Steinke <robert.steinke@xxxxxxxxx>
wrote:
So it looks like Elon's Starship plans are shaking out like this:
VTVL
Incremental development from suborbital hopper to TSTO
Full reusability from the beginning, then add orbital performance, not the
other way around.
I could swear I've seen that kind of plan somewhere before ;)