Project Low-Thrust Trajectory Planner

[boogabooga]

So, I've been working on an ion propulsion mission. I used the tool to get the following plan to 90 Antiope:

----- Search Parameters -----
Minimum Departure Date: 58100
Maximum Departure Date: 58760
Minimum Cruise Time After Launch: 7 days
Minimum Cruise Time Between Burns: 1 days
Minimum Cruise Time After Final Burn: 1 days
Maximum Cruise Time After Final Burn: 30 days
Calculation Step: 0.5 days
Velocity Importance: 0
Launch Date Modifier: 0.1
Launch DeltaV Modifier: 1
Burn Date Modifier: 0.1
Burn Velocity Modifier: 0.1


----- Spacecraft Info -----
Mass: 735 kg
Fuel: 850 kg
Isp: 28439.285
Thrust: 0.154 N

----- Launch Info -----
Departure: Earth
Target: 90 Antiope
Eject Date: 58202.3127787221
Prograde Velocity: 447.503120577385 m/s
Outward Velocity: 1544.58936824455 m/s
Plane Velocity: -1189.11086134953 m/s

----- Burn 1-----
Burn Start Date: 58209.6563281135
Burn Duration: 632.135990148286 days
Prograde Velocity: 5824.15009521243 m/s
Outward Velocity: 752.25514091036 m/s
Plane Velocity: 101.721464200755 m/s

----- Burn 2-----
Burn Start Date: 59231.1892933028
Burn Duration: 445.73234868337 days
Prograde Velocity: 5017.42275410841 m/s
Outward Velocity: 69.787244977017 m/s
Plane Velocity: 0.240430282390507 m/s

----- Burn 3-----
Burn Start Date: 59685.4463112521
Burn Duration: 0.16614863568803 days
Prograde Velocity: 0.472566696549829 m/s
Outward Velocity: 1.80466061169118 m/s
Plane Velocity: 0.839462717828264 m/s

----- Estimated Arrival Info -----
Arrival Date: 59715.8127787221
Arrival Distance: 0.508690237912773 km
Arrival Velocity: 9148.41663015385 m/s
Remaining Fuel: 345.647067076352 kg

I tried the mission and got to within about 40Gm.

One thing I noticed was that I was passing way south of the asteroid.

I used IEAT MFD to fly the mission. Since it uses constant pitch and yaw, it is compatible with the IMFD "Velocity Frame" in the Delta Velocity program. I see that the outputs of this planner program are the TransX standard, and I flipped the sign of the outward velocity when I input to IMFD Delta Velocity. However, I'm not sure if the conversion is that simple. The "Velocity Frame" has different properties than the TransX frame. For example, the plane change velocity component in "Velocity Frame" does NOT affect the resultant energy or semi-major axis of an orbit. It does in TransX, since your final velocity is the vector sum of the components.

Anyone have any insights? I'm not that familiar with the frame of reference being used in TransX. Is it like the IMFD "ApolloP30LVLH" frame?

If there turns out to be a difference, I suggest that the future version of this planner output in the IMFD "Velocity Frame" so that missions can be flown with IEAT MFD.

[ame="http://www.orbithangar.com/searchid.php?ID=3815"]IEAT MFD[/ame]

Another suggestion would be to include the heliocentric orbital elements after each burn so that the user knows if they performed the burn correctly.

 

[Piper]

Ya, I've been playing with this program a lot lately, and I realised that I programmed the plane change inputs backwards if you are using TransX (the program I was going to use for orienting the spacecraft, as the pointing function in it is far more accurate than IMFD's). I also believe I must have done something wrong in programming the launch portion of it, beyond just pointing one of the vectors the wrong way. That, or I'm calculating the position of the spacecraft wrong as it moves through space. Either way, it basically means the program isn't usable until I finish translating it to VB2010, and fix whatever is throwing off the trajectories.

For the frame of reference, I was actually thinking of programming it to allow the user to select either the IMFD reference, or TransX's frame of reference.

 

[boogabooga]

Wait, what?

AFAIK, IEAT MFD is the only MFD to allow pointing at 100 000x time acceleration. I don't understand how you could use either IMFD or TransX alone, as it would take months of real time to complete the mission.

If it helps, the trajectory looks good in Celestia...

Actually, the probe arrives a bit ahead of the asteroid, but the plane alignment seems okay. Perhaps I should see if the ephemeris are the same between this tool, Orbiter, and Celestia.

 

[BrianJ]

One thing I noticed was that I was passing way south of the asteroid.

Hmmm, this gives me a feeling that it maybe IEATMFD pointing function that is in error.
Let me check the code and get back to you.

EDIT:-
Nope, all is good with IEATMFD pointing. I had a niggling feeling that the reference orbit-normal vector was actually ecliptic-normal - but it really is orbit-normal, as it should be.