- In chapter 7, Alma says, “The Titan II rockets used
liquid hydrogen for the upper stages, but they used kerosene
for the first stage.” This is completely wrong. The
Titan II was a two stage rocket and used the same hypergolic
propellants (hydrazine fuel and dinitrogen tetroxide oxidiser)
in both the first and second stages.
- In chapter 30 it is claimed “While the first stage
of a Titan II rocket could be powered by kerosene, the
second and third stages needed a fuel with a higher
specific impulse in order to reach escape velocity of
25,000 miles per hour.” Oh dear—let's take
this point by point. First of all, the first stage of
the Titan II was not and could not be powered by
kerosene. It was designed for hypergolic fuels, and its
turbopumps and lack of an igniter would not work with kerosene.
As described below, the earlier Titan I used kerosene, but
the Titan II was a major re-design which could not be
adapted for kerosene. Second, the second stage of the Titan
II used the same hypergolic propellant as the first stage, and
this propellant had around the same specific impulse as
kerosene and liquid oxygen. Third, the Titan II did not have
a third stage at all. It delivered the Gemini spacecraft into
orbit using the same two stage configuration as the
ballistic missile. The Titan II was later adapted to use
a third stage for unmanned space launch missions, but a third stage
was never used in Project Gemini. Finally, the mission of
the Iron Dragon, like that of the Titan II
launching Gemini, was to place its payload in low Earth orbit
with a velocity of around 17,500 miles per hour, not
escape velocity of 25,000 miles per hour. Escape velocity
would fling the payload into orbit around the Sun, not on
an intercept course with the target in Earth orbit.
- In chapter 45, it is stated that “Later versions
of the Titan II rockets had used hypergolic fuels,
simplifying their design.” This is incorrect:
the
Titan I
rocket used liquid oxygen and kerosene
(not liquid hydrogen), while the
Titan II,
a substantially
different missile, used hypergolic propellants from
inception. Basing the Iron Dragon's design
upon the Titan II and then using liquid hydrogen and
oxygen makes no sense at all and wouldn't work. Liquid
hydrogen is much less dense than the hypergolic fuel used
in the Titan II and would require a much larger fuel tank
of entirely different design, incorporating insulation
which was unnecessary on the Titan II. These changes would
ripple all through the design, resulting in an entirely
different rocket. In addition, the low density of liquid
hydrogen would require an entirely different turbopump design
and, not being hypergolic with liquid oxygen, would require
a different pre-burner to drive the turbopumps.
- A few sentences later, it is said that “Another difficult
but relatively straightforward problem was making the
propellant tanks strong enough to be pressurized to
5,000 psi but not so heavy they impeded the rocket's
journey to space.” This isn't how tank pressurisation
works in liquid fuelled rockets. Tanks are pressurised to increase
structural rigidity and provide positive flow into the
turbopumps, but pressures are modest. The pressure needed
to force propellants into the combustion chamber comes from
the boost imparted by the turbopumps, not propellant
tank pressurisation. For example, in the Space Shuttle's
External
Tank, the flight pressure of the liquid hydrogen tank
was between 32 and 34 psia, and the liquid oxygen tank 20 to 22
psig, vastly less than “5,000 psi”. A fuel tank
capable of withstanding 5,000 psi would be far too heavy to
ever get off the ground.
- In chapter 46 we are told, “The Titan II had been
adapted from the Atlas intercontinental ballistic
missile….” This is completely incorrect.
In fact, the Titan I was developed as a backup
to the Atlas in case the latter missile's innovative
technologies such as the pressure-stabilised “balloon
tanks” could not be made to work. The Atlas and
Titan I were developed in parallel and, when the Atlas
went into service first, the Titan I was quickly
retired and replaced by the hypergolic fuelled Titan II,
which provided more secure basing and rapid response to
a launch order than the Atlas.
- In chapter 50, when the Iron Dragon takes off,
those viewing it “squinted against the blinding glare”.
But liquid oxygen and liquid hydrogen (as well as the hypergolic
fuels used by the original Titan II) burn with a nearly
invisible flame. Liquid oxygen and kerosene produce a brilliant
flame, but these propellants were not used in this rocket.
- And finally, it's not a matter of the text, but what's
with that cover illustration, anyway? The rocket ascending
in the background is clearly modelled on a Soviet/Russian
R-7/Soyuz
rocket, which is nothing like what the
Iron Dragon is supposed to be. While
Iron Dragon is described as a two stage
rocket burning liquid hydrogen and oxygen, Soyuz is a
LOX/kerosene rocket (and the illustration has the
characteristic bright flame of those propellants), has
four side boosters (clearly visible), and the spacecraft
has a visible launch escape tower, which Gemini did not
have and was never mentioned in connection with the
Iron Dragon.
Fixing all of these results in the
Iron Dragon's being
a two stage (see the start of chapter 51) liquid hydrogen fuel,
liquid oxygen oxidiser rocket of essentially novel design, sharing
little with the Titan II. The present-day rocket which most
resembles it is the
Delta IV, which
in its baseline (“Medium”) configuration is a two
stage LOX/hydrogen rocket with more than adequate payload
capacity to place a Gemini capsule in low Earth orbit. Its first
stage
RS-68 engines
were designed to reduce complexity and cost, and would be
a suitable choice for a project having to start from scratch.
Presumably the database which provided the specifications of
the Titan II would also include the Delta IV, and adapting it to
their requirements (which would be largely a matter of simplifying
and derating the design in the interest of reliability and
ease of manufacture) would be much easier than trying to transform
the Titan II into a LOX/hydrogen launcher.
