SA-214, the Last Cluster Booster

Ed Kyle wrote:

The S-IB stage wasn't as heavy as it looked. It actually compares
well with the Zenit 3 first stage - which can be considered a modern
equivalent in that it uses the same propellants and delivers about the
same total impulse. S-IB had a propellent mass ratio of about 0.907.
The Zenit first stage propellent ratio is about 0.909.


Yeah, but look at the actual physical size of the two stages:
S-1B was 6.52 m. in diameter by 24.48 m. long, and weighed in at 448,648
kg. fully fueled.
Zenit's first stage is 3.90 m. in diameter by 32.90 m. long and weighs
in at 354,300 kg. fully fueled.
Although using the Jupiter and Redstone tankage tooling made for a quick
way to make a large rocket stage (the S-1B stage consisted of a large
diameter central LOX tank based on the Jupiter tooling, surrounded by a
total of eight smaller diameter tanks based on the Redstone tooling,
four of which held LOX and four kerosene) without much new tooling
needed, it wasn't a very efficient design from an internal volume vs.
overall size viewpoint due to the empty spaces between the clustered tanks.
For a really clunky design, compare the R-7 Semyorka to Atlas for size
and weight.
Both the stage and a half Atlas D (such as used to launch Mercury) and
central core and four strap-ons R-7-8A91 (such as used for Sputnik 3)
could carry about the same payload into orbit. Atlas D weighed in at
120,000 kg. fully fueled and the R-7-8A91 at 269,973 kg. fully fueled.
Hoorah for balloon tankage.

And although it is not a fair comparison (because different propellents

are used), it is still interesting to note that SRB and Delta 4 CBC are

both "heavier", relatively speaking, than S-IB. SRB has a 0.846
propellant mass ratio, Delta 4 CBC has a 0.882 ratio.



That is to be expected given the lower isp of the SRB's fuel as well as
its need for a heavy pressure resistant casing and the low density of
the LH2 used in the Delta 4 with its need for large insulated tankage.

As for the probability of catastrophic engine failure, it would be
interesting to compare the probability of a CATO in an H-1 cluster
with the probability of a CATO in an SRB.


Tricky to do...we probably have a fair amount of data on the reliability
of the H-1 due to so many Thor and Delta flights, but we only have the
one SRB failure on Challenger to use for the SRB reliability
figures...and the design has been improved since then.

Pat