Re: Why is the CEV so heavy?

Tom Cuddihy wrote:
> This seems like a different enough topic to warrant a new thread.
> George William Herbert pointed out that the ATK-SAIC reliability study
> apparently had as one of its founding assumptions that CEV mass is
> going to be somewhere greater than 30,000 lbs, conveniently just out of
> reach for single core EELVs:
>
> http://www.boom.net/~jake/atk_docs/ATK_Thiokol_SRB.J_2S_PRA.pdf
>
> <<the footnotes read:>>
> [1]Current estimates of the CEV mass requirement indicate a mass of
> 50,000 pounds. This value
> is in excess of the indicated single core capability for EELVs such as
> the Atlas V and Delta IV,
> which have a capacity of approximately 25,000 pounds.
> [2] SAIC assumed that all worse case accidents, that is, case burst
> events, would not be
> survivable.
>
> As Damon Hill said, just why is it going to be so darn heavy? When
> Scott Horowitz talked at NPS, he alluded to thinking in the astronaut
> office in 2002 that EELV based designs were not going to work, just
> because of overall system complexity--comments on that?

NASA's CEV spec called for a 20 metric ton
(44,000 lb) liftoff mass - which would include
the escape system. This is roughly the mass of
an earth-orbital Apollo CSM (Apollo 7, Skylab,
ASTP), so that must have been NASA's starting
point for CEV. Recently, Griffin has been
talking about 30 metric tons (66,000 lbs), but
that seems to be for lunar missions (and would
also be in-line with Apollo lunar mission CSM
masses).

BTW, I have a BIG problem accepting the premise
of this SAIC study on SRB-J2S reliabilty. It
says that 1 out of 226 SRBs have failed. It
then goes on to say that based on this history,
and on some other figuring done by someone sitting
at a desk somewhere, the SRB-J2S launch vehicle
would have an expected "loss of vehicle" failure
rate of only 1/483. No mention of the fact that
the world's most proven, most reliable launch
vehicles, the ones that have actually flown more
than at least one hundred times, have only managed
no better than about 1/30 to 1/50 over the long
haul.

(An aside: I have personally witnessed about 20
space launches during my lifetime. I saw two of
those blow apart about a minute after liftoff.
A third reached an improper orbit. I'm sorry,
but my personal experience prevents me from
accepting that 1/483 statistical hogwash.)

The study also assumes, BTW, that an SRB CATO
would be nonsurvivable, but that it would only
happen 1 out of every 13,858 launches.

How much did SAIC bill for this nonsense?!

- Ed Kyle

.

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