6.1.3
Ballistics
A program was cevised whereby trajectories for the instrumented carriers
are calculated on the T3M 704 EDPM.° The progras vas flexible enwwga ta accom
mocate both the single- and two-stage carriers aad to allow also for changes ia
vehicle parameters such as weight, impulse, ami Launching coodicions.
The save
prozrzm is used for predicting the trajectory for a given wind structure.
Trajectory calculations are based on equations of motion of the wehicle in
a rectangular coordiaate system on a nonrotating earth.
Since all trajectories
are nearly wertical or short-ranged, error resulting from use of rectangular
covrdinates is small.
The effects of Coriolis were computed for theoretical,
no-~drag trajectsries and are added as correctisns to the IBM TOs resuils.
A
monthly average for ataospheric temperature and Jensity above Johnston Island
was used.
This was sufficiently accurate, in that the difference in the effect
of two extreme ataospheres on che altitude is approzicstely 2 percent.
Drag
coefficients were determined from wind-tunnel tests and have been corrected
with results obtained from several deveicpmental singie-stage firings.
The
earth's gravity potential is assumed to decrease with altitude from the local
value at the surface,
For a given rocket engine, nominal total impul-e in the IBM program is
corrected by a factor dependenr on the propellant weight of the rocket as compared to a nominal propellant weight.
Loss in impulse during the boost phase
of the two-stage rockets caused by early separation is allowed for, as is also
the added impulse of the second stage caused by burning under lower ambient
pressure conditions.
during burning.
The mass of the rocket is assumed to decrease linearly
Effects of varying the parameters of weight, launch angle,
and impulse are given in Table 8.1.
The effect of winds on the trajectory is attributable mainly to the weather-
vaning effect and, to a lesser extent, wind drift.
For the calculations, con-
sideration is given to the effect of weather vaning during burning, but drift
is neglected.
Direction and magnitude of wind vectors at wariocus intervals of
altitude are inserted in the IBM progras.
The major portion of the wind effect
for the Johnston Island wind struccure was expected to taxe place in the region
just above the surface.
In addition, consideration is given to the effect of
wind drift on the parachute during tke recovery phase of the trajectory.
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VES