Last time we stopped our review at the first of the Delta rockets proper, the Delta-A. The Delta-B was the next variant of the Delta family, and was very similar, with a lengthened second stage and an upgraded second stage engine, the AJ-10-118D. The Delta-A used the AJ-10-118.
The AJ-10-118D burns unsymmetrical dimethylhydrazine (UDMH) as a fuel, and inhibited red fuming nitric acid (IRFNA) as an oxidizer, instead of UDMH and white fuming nitric acid (WFNA), which is what the AJ-10-118 used. Variants of the AJ-10 have been used on the Apollo program, the Space Shuttle program, and are planned to be used on the Orion program.
Fuming nitric acid is more concentrated than concentrated nitric acid (>86% vs ~68%), and WFNA is nearly pure nitric acid. It makes lab gloves burst into flames.
WFNA and IRFNA are both hypergolic with UDMH. IRFNA has slightly higher performance than WFNA, however it is also considerably more dangerous, as in addition to being corrosive to almost everything, it is also more toxic and gives off nitrogen dioxide fumes. IRFNA has an inhibitor added to prevent it from being quite as corrosive. If you want to read more about this kind of thing, I can't recommend Ignition! highly enough.
Delta-B launched nine times, with one failure. The Delta-C increased the fairing size, and used an upgraded 3rd stage. It launched 13 times, with one failure.
The Delta-D, aka the Thrust Augmented Delta, added 3 strap-on Castor I solid boosters to the first stage. The Delta-E was known as the Thrust Augmented Improved Delta, with Castor 2 solid boosters, and increased the thrust of the first stage engine, the MB-3 (in this case, MB-3-III), which is part of the LR-79 family. Some sources say that the upgrade to the MB-3-III was on the Delta-D, but most say Delta-E. The second stage was made restartable, and was enlarged, along with the fairing. The third stage was changed again, and another third stage was available as an option, with which it was known as the Delta-E1.
Delta-F would have been similar to the Delta-E, but without the solid boosters, but was never built. Delta-G was a one-off, built for just two launches, Biosatellite 1 and 2, and lacking the third stage. Delta-H was similar to the Delta-G, but without the solid boosters, but was never built. Delta-I was never built, likely to avoid confusion with a possible future Delta One. Delta-J had yet another third stage, and launched just once. Delta-K was a design for a Delta with a liquid oxygen/liquid hydrogen upper stage, and was never built.
Delta-L introduced the Extended Long Tank first stage, which was longer, and not tapered. Delta-M and -N were very similar, but with different third stages. There were variants of the Delta-M and -N, known as Delta-M6 and -N6, which had six, rather than three solid boosters.
In 1972, Delta numbering systems changed from the old letter system to a four-digit numbering system. Next time, I'll cover everything under that system.
