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Update orbital target far zone simulatio to include leading J3 gravity effects

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Thorsten Renk 2019-01-14 13:47:29 +02:00
parent 7719bcee7c
commit 59f0bfc5ca
1 changed files with 100 additions and 20 deletions
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120
Nasal/orbital_target.nas
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@ -1,7 +1,7 @@
###########################################################################
# simulation of a faraway orbital target (needs handover to spacecraft-specific
# code for close range)
# Thorsten Renk 2016
# Thorsten Renk 2016 - 2019
###########################################################################
var orbitalTarget = {
@ -17,14 +17,21 @@ var orbitalTarget = {
t.l_vec = [math.sin(t.inc_rad), 0.0, math.cos(t.inc_rad)];
t.node_longitude = node_longitude;
t.nl_rad = t.node_longitude * math.pi/180.0;
t.initial_nl_rad = t.nl_rad;
var l_tmp = t.l_vec[0];
t.l_vec[0] = -math.sin(t.nl_rad) * l_tmp;
t.l_vec[1] = math.cos(t.nl_rad) * l_tmp;
t.anomaly = anomaly;
t.anomaly_rad = t.anomaly * math.pi/180.0;
t.initial_anomaly_rad = t.anomaly_rad;
t.delta_lon = 0.0;
t.update_time = 0.1;
t.running_flag = 0;
t.elapsed_time = 0.0;
t.node_drift = -4361.26 * 1./math.pow(t.radius/1000.0 ,2.0) * math.cos(t.inc_rad);
print ("Drift rate: ", t.node_drift);
return t;
},
@ -62,34 +69,91 @@ var orbitalTarget = {
}
me.anomaly = me.anomaly_rad * 180.0/math.pi;
me.delta_lon = me.delta_lon + dt * 0.00418333333333327;
me.node_longitude = me.node_longitude + me.node_drift * dt;
me.nl_rad = me.node_longitude * math.pi/180.0;
},
get_inertial_pos: func {
# movement around equatorial orbit
var x = me.radius * math.cos(me.anomaly_rad);
var y = me.radius * math.sin(me.anomaly_rad);
var z = 0;
return me.compute_inertial_pos(me.anomaly_rad, me.nl_rad);
# tilt with inclination
z = y * math.sin(me.inc_rad);
y = y * math.cos(me.inc_rad);
# rotate with node longitude
var xp = x * math.cos(me.nl_rad) - y * math.sin(me.nl_rad);
var yp = x * math.sin(me.nl_rad) + y * math.cos(me.nl_rad);
return [xp, yp, z];
},
get_future_inertial_pos: func (time) {
var anomaly_rad = me.anomaly_rad + time/me.period * 2.0 * math.pi;
get_inertial_pos_at_time: func (time) {
var anomaly_rad = me.initial_anomaly_rad + time/me.period * 2.0 * math.pi;
while (anomaly_rad > 2.0 * math.pi)
{
anomaly_rad = anomaly_rad - 2.0 * math.pi;
}
var nl_rad = me.initial_nl_rad + me.node_drift * time * math.pi/180.0;
return me.compute_inertial_pos(anomaly_rad, nl_rad);
},
get_inertial_speed: func () {
# obtain via numerical discretization from two points
var anomaly_rad = me.anomaly_rad;
while (anomaly_rad > 2.0 * math.pi)
{
anomaly_rad = anomaly_rad - 2.0 * math.pi;
}
var pos1 = me.compute_inertial_pos(anomaly_rad, me.nl_rad);
anomaly_rad = me.anomaly_rad + 0.1/me.period * 2.0 * math.pi;
while (anomaly_rad > 2.0 * math.pi)
{
anomaly_rad = anomaly_rad - 2.0 * math.pi;
}
var pos2 = me.compute_inertial_pos(anomaly_rad, me.nl_rad);
var vx = (pos2[0] - pos1[0])/0.1;
var vy = (pos2[0] - pos1[0])/0.1;
var vz = (pos2[0] - pos1[0])/0.1;
return [vx, vy, vz];
},
get_inertial_speed_at_time: func (time) {
# obtain via numerical discretization from two points
var anomaly_rad = me.initial_anomaly_rad + time/me.period * 2.0 * math.pi;
while (anomaly_rad > 2.0 * math.pi)
{
anomaly_rad = anomaly_rad - 2.0 * math.pi;
}
var nl_rad = me.initial_nl_rad + me.node_drift * time * math.pi/180.0;
var pos1 = me.compute_inertial_pos(anomaly_rad, nl_rad);
anomaly_rad = me.initial_anomaly_rad + (time + 0.1)/me.period * 2.0 * math.pi;
while (anomaly_rad > 2.0 * math.pi)
{
anomaly_rad = anomaly_rad - 2.0 * math.pi;
}
nl_rad = me.initial_nl_rad + me.node_drift * (time+0.1) * math.pi/180.0;
var pos2 = me.compute_inertial_pos(anomaly_rad, nl_rad);
var vx = (pos2[0] - pos1[0])/0.1;
var vy = (pos2[0] - pos1[0])/0.1;
var vz = (pos2[0] - pos1[0])/0.1;
return [vx, vy, vz];
},
compute_inertial_pos: func (anomaly_rad, nl_rad) {
# movement around equatorial orbit
var x = me.radius * math.cos(anomaly_rad);
var y = me.radius * math.sin(anomaly_rad);
@ -99,13 +163,28 @@ var orbitalTarget = {
z = y * math.sin(me.inc_rad);
y = y * math.cos(me.inc_rad);
# rotate with node longitude
var xp = x * math.cos(me.nl_rad) - y * math.sin(me.nl_rad);
var yp = x * math.sin(me.nl_rad) + y * math.cos(me.nl_rad);
var xp = x * math.cos(nl_rad) - y * math.sin(nl_rad);
var yp = x * math.sin(nl_rad) + y * math.cos(nl_rad);
# this is a good bit of trickery to capture leading J3 dynamics
var corr_200 = -2.6e-5 * me.inclination + 1.00321;
var corr = corr_200 * (1.0 + (me.altitude/1000.0-200.0) * 6e-7);
corr = 1.0 + (0.64 * (corr -1.0));
#print ("Corr200 is now:", corr_200);
#print ("Corr is now:", corr);
#print ("Altitude: ", me.altitude);
z /= corr;
return [xp, yp, z];
},
get_latlonalt: func {
var coordinates = geo.Coord.new();
@ -120,6 +199,7 @@ var orbitalTarget = {
if (me.running_flag == 1) {return;}
me.running_flag = 1;
me.run();
},
stop: func {
me.running_flag = 0;