[AR] changing hardware (was Re: Re: Re spacex falcon 9 landing)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Mon, 28 Dec 2015 16:43:33 -0500 (EST)
On Mon, 28 Dec 2015, Ian Woollard wrote:
Whereas, the Shuttle *couldn't* change much.
The shuttle hardware changed quite a bit over time. There was a certain
amount of inertia, yes, but that was mostly budgetary limitations, plus an
inefficient organization that made changes very costly. There was a long
list of desired changes, but funding them was always a struggle. Some got
made only when they had become unavoidable, e.g. the cockpit-display
upgrade forced its way into the budget because the old hardware was long
out of production and spares stocks were running out. Some things that
would have substantially reduced ops costs -- notably, a switch to
nontoxic RCS/OMS propellants -- never made it in, not because there was
any fundamental obstacle, but because it was always cheaper to carry on
with the existing design a little longer.
(And if you imagine that such issues never come up for expendables, you're
dreaming. There's a lot of very old hardware and software still in
service on today's expendables.)
...the maximum payload climbed from ~20 tonnes to over 30 tonnes, but
IRC (and I may not) some of that was changes to the external tank- an
expendable part!
It was fundamentally difficult to improve payload mass much by changing
the orbiters, because the orbiter had already been scrubbed thoroughly for
incremental payload improvements, due to weight-growth crises during
development. The original post-Challenger intent was that ASRM -- the SRB
rebuild -- would provide enough performance boost for station launches;
the lighter ET started to feature in plans only when it became clear that
ASRM was in serious budget trouble.
Full reusability, in many ways, is a trap, at the current launch rates.
So what? Building even an *expendable* new launcher is almost impossible
to economically justify at current launch rates. Anyone building even a
partially-reusable launcher is doing it in hopes of new markets and much
higher launch rates.
Henry
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