Re: Air Force Signs Off on SRB-CEV


Brian Thorn wrote:
> On 16 Aug 2005 07:42:00 -0700, "Ed Kyle" <edkyle99@xxxxxxxxxxx> wrote:
>
> >I think Boeing did this comparison several years ago
> >and decided to keep Delta II and cancel Delta IV Light
> >(I'm assuming that is what you mean by "small upper
> >stage"). But even a Delta IV Light would have 1.5
> >times or so more dry mass than a Delta 7920, so the
> >odds are that it would have higher marginal costs.
>
> Is dry mass relevant, though? Since Delta II uses nine solids, and
> there is no such thing as an unfueled solid, its hard to figure out
> the bird's dry mass. But a fueled Delta IV-Lite (guessing about PAM as
> an upper stage) would seem to compare favorably to a fueled nine-solid
> Delta II (especially II-H).

An Alliant GEM solid rocket motor weighs 1,310 kg
with no propellant loaded. (It weighs 13,080 kg
loaded with solid propellant.) The "dry", or
empty, mass of a Delta 7920 is as follows.

Nine ATK GEM-46 SSRMs 11,790 kg
XLET Thor First Stage: 5,678 kg
Second Stage (AJ10-118K engine): 950 kg
Payload Fairing (Approximate): 900 kg
-------------------------------------------
Total Delta 7920 Dry Mass: 19,318 kg

Assuming that the Delta 7920 second stage
would be minimally modified for use by a
Delta IV Light variant, a Delta IV Light
would have the following dry mass budget:

CBC First Stage: 26,760 kg
Second Stage (AJ10-118K engine): 950 kg
Payload Fairing (Approximate): 900 kg
--------------------------------------------
Total Delta IV Dry Mass: 28,610 kg

So a Delta IV Light would have about 1.5 times
more dry mass (about 9.3 tonnes (20,500 lbs)
more metal, fiberglass, etc.) than a Delta 7920,
but it would only provide about 1.2 times more
payload lifting ability. In 1998, Michael
Griffin said that a launch vehicle's production
cost is roughly equal to $1,000 per pound of dry
mass. If true, a Delta IV Light would cost about
$20.5 million more to build than a Delta 7920.

- Ed Kyle

.

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