[AR] Re: shuttle SRBs (was Re: Re: Phenolic regression rate)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sun, 4 Feb 2018 18:22:43 -0500 (EST)
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
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