F2/H2 vs H2/O2 specific impulse: why fluorine is higher ?

In article ,
James Wentworth wrote:
Didn't Vanguard's first stage use LOX/UDMH? -- Jason

No, it was a LOX/kerosene upgrade of the LOX/alcohol Viking sounding
rocket.

You're thinking of Jupiter C (aka Juno I), whose first stage burned LOX
and "Hydyne", a UDMH-based mixture (again, a performance upgrade from the
LOX/alcohol Redstone).

The Vanguard second stage, a heavily upgraded Aerobee-Hi, burned WFNA and
UDMH, the only US hardware which used that combination.

(Interestingly enough, Kurt Stehling -- Vanguard's head of propulsion --
observed in his book that Vanguard was sold partly on the basis that it
*was* mostly an Aerobee-Hi on top of a Viking, and that if the project had
done exactly that, it could probably have been doing flight tests in late
1956 with a satellite launched in early 1957. The only really new part --
the solid third stage -- was developed very quickly and gave no trouble at
all. The only problem was that a Viking/Aerobee-Hi Vanguard would have
had an orbital payload of only 5-10lb, which was not enough for the fancy
multi-instrument satellite design. It was the upgrades to the first and
second stages, more than anything else, which turned the project into a
protracted nightmare.)
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |