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This HP program can be used to calculate ballistic interplanetary trajectories between the Earth and Mars. The orbit transfer is modelled as a two-body system with an impulsive delta-v at departure and arrival.

The user can provide an Earth departure calendar date and a Mars arrival calendar date. The following is the "hard-wired" data for the attached example.

// departure calendar date

month := 6;

day := 1;

year := 2003;

// departure utc julian day

jd_depart := julian(month, day, year);

// earth is the departure planet

ip_depart := 3;

sv_depart := planet(ip_depart, jd_depart);

for i from 1 to 6 do

oev_depart(i) := sv_depart(i + 6);

end;

// arrival calendar date

month := 12;

day := 27;

year := 2003;

// arrival utc julian day

jd_arrive := julian(month, day, year);

// mars is the arrival planet

ip_arrive := 4;

sv_arrive := planet(ip_arrive, jd_arrive);