FIRST STEPS TOWARD SPACE - Smithsonian Institution Libraries

46 SMITHSONIAN ANNALS OF FLIGHT
combustion chamber C; all lined with insulating refractory
material, contained at its bottom a crucible
filled with pellets of refractory material. The crucible
was electrically brought to a deep red temperature,
after which the current was turned off
and the monopropellant injection through the injector
was started. The resulting gases were evacuated
through a small nozzle and collected in a
gasometer G, after cooling and separation of the
condensed fraction.
The nitroglycerin mixture responded exactly according
to the predictions of the thermochemical
calculations, proving my point (if, indeed, it needed
proof!). More important, it provided a hint of the
practical possibilities of liquid monopropellants.
However, this particular monopropellant was considered
to be unsafe because of the possibility of
separation, either by evaporation or by water addition,
of the two components. Indeed, we had ourselves
experienced a delayed explosion in the feeding
line of Figure 18 which could be attributed to
FIGURE 20.—Demonstration turbine for operation with
nitromethane.
FIGURE 19.—Nitromethane engine.
this reason. Hence Dr. Corelli prepared a list of
possible organic solvents, presumably better than
methanol with respect to separation, and I started
the thermochemical calculations using each of them
as a diluent. This was the path that made me accidentally
stumble on the exceptional properties of
mononitromethane.
I was indeed surprised to find that while, according
to my calculations, other solvents provided
results comparable to those of methanol, the outcome
for nitromethane was well in excess of the
others from the point of view of the overall heat of
reaction and combustion temperature. Then,
performing the calculations for nitromethane alone,
I found this compound to be in itself an excellent
monopropellant, better than any of the safe nitroglycerin
mixtures. Of course, this was a surprise,
since the explosive character of nitromethane had
never, to our knowledge, been pointed out.
It is natural that after this find our research concentrated
on nitromethane. Dr. Corelli prepared
a good amount of it in our own laboratory because
it was not commercially available in Italy, although
at about that time it became available in U.S.A.
as a solvent of nitrocellulose. To protect secrecy we
baptized nitromethane with the name of Ergol. (By
a strange coincidence this name was also used a few
years later in Germany to indicate any liquid propellant.)
We studied carefully its stability against
mechanical shocks, which makes it very difficult to
detonate, and its resistance to thermal decomposition.
We measured its vapor pressure up to 200 °C.
We determined its thermal stability by dropping
into baths of molten metal with increasingly higher
temperatures small sealed capsules containing nitromethane,
so designed that they would explode only
if thermal decomposition took place. The lower