Space trajectories Program studies the motion of a space probe confined to the solar system and influenced by the nonspherical Earth and Moon, and the point masses defined by the Sun, Venus, Mars, and Jupiter. It is written in the FORTRAN Assembly Program language

Holdridge, D. B.

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June 1967	 Brief 67-10172 
NASA TECH BRIEF ia 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Space Trajectories Program for IBM 7090 
The Space Trajectories Program is designed for the 
study of the motion of a space probe confined to the 
solar system and influenced by the nonspherical Earth 
and Moon, and the point masses defined by the Sun, 
Venus, Mars, and Jupiter. The program may also be 
employed in other applications, of which the follow-
ing are some examples. 
A simplified power-flight arc may be simulated 
which assumes a constant thrust, constant burning 
rate motor with thrust direction fixed in space. Any 
of the above mentioned bodies may serve as the 
reference body at the injection epoch, and stepwise 
numerical integration of the equations of motion ap-
propriate to either a Cowell or an Encke scheme 
serves to step the probe along its flight path to one 
of the bodies, which then serves as a target. 
Standard-type trajectories injecting near the Earth, 
and having as target one of the bodies Earth, Moon, 
Venus, or Mars, have been given special treatment 
to reduce the volume of input necessary for execution. 
The injection conditions may be input in Cartesian or 
spherical coordinates based on one of four reference 
frames: mean equator and equinox of 1950.0, mean 
equinox and ecliptic of 1950.0, true equator and 
equinox of date, and the true equinox and ecliptic of 
date. For the Earth as injection body, the Earth-fixed 
spherical set, based on a rotating Earth, is available; 
for the Moon as injection body, the selenographic 
(Moon-fixed spherical) coordinate set, which takes 
into account the rotation of the Moon, may be used. 
For injection conditions taken with reference to the 
Earth, a quasi-orbital element set for escape hyper-
bolas, known as the energy-asymptote option, has been 
made available.
For output, any of the above quantities may be 
obtained at will, along with ephemeris information 
expressed in any one of the four Cartesian or 
spherical coordinate systems; conic output may be 
called for which expresses the osculating two-body 
orbit in many sets of orbital elements referred to 
one of the standard Cartesian frames; all manner of 
the principal angles between the probe and the bodies 
may be displayed; up to a maximum of 15 tracking 
stations may be used to observe the probe in topo-
centric spherical coordinates; or view periods of the 
stations may be determined by the program and dis-
played in the form of rise, maximum elevation, and 
set prints. 
Notes: 
1. The program has been written in the Fortran 
Assembly Program language and vou1d require 
reprogramming for runs on machines other than 
the IBM 7090. 
2. After the necessary transformation of the injection 
conditions to the Cartesian coordinates based on 
the mean equator and equinox of 1950.0, the 
Space Trajectories Program is controlled primarily 
by the subroutine MARK which performs the 
stepwise numerical integration of the equations of 
motion to obtain the solution at desired points 
along the trajectory. The trajectory is divided into 
phases to permit control of output format and 
print frequency and of the numerical integration 
process itself. Each phase is characterized by a 
set of phase parameters which are interpreted be-
fore the numerical integration proceeds. 
(continued overleaf) 
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https://ntrs.nasa.gov/search.jsp?R=19670000172 2020-03-11T20:52:30+00:00Z
3. The output of the Space Trajectories Program dis-
plays for each trajectory the fundamental astro-
nomical constants used in the calculation, the 
injection conditions which serve as a starting 
point for the trajectory, and the desired output 
groups which are requested principally as a func-
tion of time. 
4. Additional details are contained in, "Space Tra-
jectories Program for the IBM 7090 Computer," 
by D. B. Holdridge, Technical Report No. 32-223, 
Revision No. 1, September 1, 1962, Jet Propul-
sion Laboratory, which is available from: 
COSMIC 
Computer Center 
University of Georgia 
Athens, Georgia 30601 
Reference: B67-10172
Patent status: 
No patent action is contemplated by NASA. 
Source: D. B. Hoidridge 
Jet Propulsion Laboratory 
(NPO-10125) 
Brief 67-10172	 Category 06


Space trajectories program for IBM 7090

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