On the other hand, Falcon clustering Merlins isn't a big deal, and they're
(M1D) ~ 140,000 LBT at sea level.
Serial production. Can be had preintegrated into in a fully reusable stage,
even...
-george
Sent from my iPhone
On Feb 4, 2018, at 3:22 PM, Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
On Sun, 4 Feb 2018, John Stoffel wrote:
LOX/Kero boosters I'm pretty sure we're thought of, but did they have
the thrust/weight ratio to really work well?
There's no question that it can be done -- note that Energia/Buran, the
Soviet shuttle equivalent, used LOX/kerosene boosters -- but there's a
problem in that the US doesn't currently have any big LOX/kerosene engines on
hand. The RS-27A (Delta II core) is the biggest that's been in US production
recently, and it's rather small for the job. The US production line for the
RD-180 never materialized. The F-1 tooling is long gone, and any attempt to
rebuild it could all too easily turn into another J-2X fiasco: it's tempting
to revise the design some for easier production, but that's a very slippery
slope. The BE-4 isn't yet flight-ready and has the minor disadvantage of
burning methane (which is a bit bulky, although not nearly as bad as LH2 in
that department).
I see so many current and even new designs using SRBs in varying counts that
they must just be considered the best solution to a tough problem, even with
the risks.
Technically they're not a good solution, given their ugly failure modes, but
they do have the advantage of being available off the shelf. And they have
established Congressional support, whereas nobody knows just which
Congressional districts a big new competitively-procured LOX/kerosene engine
would be built in.
Do you think they'll ever man-rate a system with solid boosters again? I
just can't see it happening, even if they're smaller ones that produce much
less of the total thrust at liftoff.
NASA man-rating today is a very political process. (Just look at the
differences between NPR 8705.2A -- the man-rating spec that was used to
reject launching Orion on the EELVs -- and NPR 8705.2B -- the "update" that
appeared when MSFC started trying to clear Ares I for manned launches.)
There is no realistic doubt that if SLS survives long enough to be ready for
a manned launch, it will be decreed to be man-rated.
Henry