[AR] Re: ESAS Safety Concerns about Small SRMs
- From: Lars Osborne <lars.osborne@xxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Mon, 16 Apr 2018 11:09:10 -0700
Both Atlas and Delta single-engine upper stages fly highly lofted
trajectories, which can produce high deceleration loads on the crew during
an abort and, in some cases, can exceed crew load limits as defined by NASA
STD 3000, Section 5. Depressing the trajectories flown by these vehicles
will require additional stage thrust to bring peak altitudes down to levels
that reduce crew loads enough to have sufficient margins for off-nominal
conditions.
Is this why starliner will fly on a DEC?
Lars
Thanks,
Lars Osborne
On Mon, Apr 16, 2018 at 10:59 AM, <Nels.Anderson@xxxxxxx> wrote:
I happened to notice the following expression of concern about the safety
of small SRMs in Section 1.5.2.1 of NASA's ESAS report of 2005 (the one
that defined Constellation's 1.5-launch architecture):
"The EELV options examined for suitability for crew transport were those
derived from the Delta IV and Atlas V families. The study focused on the
heavy-lift versions of both Delta and Atlas families, as it became clear
early in the study that none of the medium versions of either vehicle had
the capability to accommodate CEV lift requirements. Augmentation of the
medium-lift class systems with solid strap-on boosters does not provide
adequate capability and poses an issue for crew safety regarding small
strap-on Solid Rocket Motor (SRM) reliability, as determined by the Orbital
Space Plane-ELV (OSP–ELV) Flight Safety Certification Study report, dated
March 2004.
"Both Atlas and Delta derived systems required new upper stages to meet
the lift and human-rating requirements. Both Atlas and Delta single-engine
upper stages fly highly lofted trajectories, which can produce high
deceleration loads on the crew during an abort and, in some cases, can
exceed crew load limits as defined by NASA STD 3000, Section 5. Depressing
the trajectories flown by these vehicles will require additional stage
thrust to bring peak altitudes down to levels that reduce crew loads enough
to have sufficient margins for off-nominal conditions. Neither Atlas V or
Delta IV with their existing upper stages possess the performance
capability to support CEV missions to ISS, with shortfalls of 5 mT and 2.6
mT, respectively."
What was the issue with small SRMs identified by the OSP report? The
second paragraph quoted makes clear that it's not just an oblique way of
referring to the infamous non-existent "black zones".
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