Computer program enables study of one-way transfers, single and double planet flybys, single and double planet stopovers, or mixed flyby and stopover trajectories. In each operation it first computes the heliocentric conic which connects the centers of the launch and target planets and requires a given trip time

Davis, D. A.

Gussow, D. G.

English

NASA Technical Reports Server

February 1968	 Brief 68-10033 
NASA TECH BRIEF 
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. 
Computer Program for Interplanetary Conic Patching 
A computer program has been designed that makes 
possible the study of one-way transfers, single planet 
flybys, double planet flybys, single planet stopovers, 
double planet stopovers, or mixed flyby and stopover 
trajectories. 
This program is capable of the rapid calculation of 
interplanetary trajectories applicable to parametric 
studies. One such trajectory is the one-way transfer 
whose parameters are useful either as approximations 
for inputting to high accuracy trajectory programs 
which use numerical integration schemes or as figures 
of merit for one-way transfers of the Mariner type. 
The program can also use the gravitational influence 
of a planet during planetary passage to alter the 
probe's trajectory about the sun to insure intercep-
tion with a selected target. Missions of this latter type 
are referred to in this program as "flybys". It is possi-
ble through judicious use of such maneuvers to obtain 
significant reductions in the incremental velocity 
requirements compared to those associated with direct 
transfers: The program can also calculate the velocity 
change needed to put the vehicle into a specified orbit 
about a planet for a preselected time, with such 
orbital stops referred to as "stopovers". An option 
also exists allowing broken leg maneuvers to be per-
formed whenever a transfer plane becomes excessively 
inclined to a planetary ecliptic. For all trajectories 
the program uses the relevant velocity increments to 
calculate the weight needed in orbit at the start of each 
leg. Trajectories whose incremental velocities exceed 
the associated input limits will be rejected by the 
program. It can also calculate the weights associated 
with these missions.
In all modes of operation this program first com-
putes the heliocentric conic which connects the cen-
ters of the launch and target planets and requires a 
given trip time. This calculation is performed by 
making use of an extension of Lambert's theorem. 
That theorem, first formulated in 1761, states: "The 
transfer time between any two points on an ellipse is 
a function of the sum of the distances of each point 
from the focus, the distance between the points, and 
the semimajor axis of the ellipse." Functionally. this 
is expressed as t = t(rL + rt, c, a), where r L is the 
radius to the launch planet from the focus measured at 
the time of launch, r t is the radius to the target planet 
measured at the time of arrival, c is the distance 
between the two planets, and a is the semimajor axis 
of an ellipse connecting the two points and requiring 
trip time t. 
Notes: 
I. This program is written in Fortran IV and MAP 
for use on the IBM 7094 computer. 
2. Inquiries concerning this program may be made to: 
COSMIC 
Computer Center 
University of Georgia 
Athens, Georgia 30601 
Reference: B68-10033 
Patent status: 
No patent action is contemplated by NASA. 
Source: D. A. Davis and D. G. Gussow 
of The Boeing Company 
under contract to 
Marshall Space Flight Center 
(M FS- 14296) 
Category 06 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19680000033 2020-03-12T05:47:07+00:00Z


Computer program for interplanetary conic patching

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server