Learning Forum

[grace.cardarelli]

It seems like the heat rates are not being recalculated during my transient case set – am I missing anything obvious? A radiator surface on my satellite rotates (using a symbol that's updated based on TIMEN) towards the sun and then back to its original position, but the temperatures are not rising like I would expect.

• The orbit is one single position at 0.0
• In my case set, I have an rk calculation (internal surfaces), a hr calculation (external surfaces/Orbit), and an art calculation (external surfaces/Orbit).
• The symbol that rotates the satellite is set in the Case Set>SINDA>REGISTER dialog box. When I plot this during the run, I can see it change in value, but the radiator temperatures do not increase as I would expect.
• (timen<=600)? (-(2/60)*timen) : ((timen<=1200)? ((2/60)*timen-40) : 0)

[Doug Bell]

Since the heating rates and other radiation tasks are calculated before the solution, and the Sinda registers are updated during the solution, the rotation is not included in the radiation tasks. Here are some guidelines:

• For updates based on orbits and heating environments, use hrTimeSec (always in seconds) instead of TIMEN or TIMEM (which are the solution times and not available during radiation tasks). Other heating rate symbols can be used if the update is not time-based.
• Include the expression in a symbol definition
• Use that symbol to define the rotation (whether for an assembly or the orbit).
• Use enough orbit positions to capture the movement to the detail that you need. Be careful about trying to capture too many orbit positions. 

You will probably want to review the orbital maneuvers tutorial, currently found on the CRTech website. That shows how to update assembly rotations and orbit position rotations (entire vehicle)

Let me know if you found this helpful or have other questions or concerns.

Kind regards,

Doug

 

[grace.cardarelli]

That does make sense, thank you. I replaced TIMEN with hrTimeSec in my if statement, and I'm using that to define the symbol in the Case Set. When I plot the symbol for tilt angle, I don't see it updating during the run - but is that just because the tilt angle isn't being updated with solution time as you mentioned? And that it's just updating the radk calculations for each time step?

I'm thinking I'm still not getting the solar loading I want at each time step, but maybe it's my orbital positions? I essentially just want the satellite to sit at L1, so I'm using two orbital positions at 0 and 360 to keep the satellite between the earth and sun (using a constant altitude above the earth). But is that the best way to represent the orbit?