Flyaround the lazy way

October 16th, 2009
With the Introduction of SP4.10 we have gotten a new set of tricks up our SSM sleeve. one of them is flying the flyaround in a very fun and easy way which might help out newcomers, authenticity enthusiasts (just look at the NASA checklists :)) and just lazy folks, like myself, that are constantly looking for ways to make life easy. 🙂
Our little endeavor starts with the new/old/reworked SPEC 20 (DAP settings) display.
as you can see I have set up the DAP prior to docking  to allow me a 0.75 deg/s rotation for the RPM and the other one to 0.1 deg/s rate for the TORVA. we will just stay with those on the TORF as well, because the 0.1 Deg/s rate is good for us here as well..
Spec20 - for ISS OPS
Now we, will make sure our DAP is set properly for the maneuver.
based on this DAP config, we will need to make sure you are on DAP A, VERN.
in addition we will set X & Z translations to NORM and leave the Y translation on PULSE.
DAP set for ISS ops
so far so good. Now comes the new trick… 🙂
UNIV PTG!!
lets switch over to that – hit OPS201PRO on the aft keypad.
we are going to use the Target track mode of the DAP (ITEM 19).
so lets start.
We will now switch the DAP to AUTO and hit ITEM 19 EXEC on the aft keypad (it’s important to switch the DAP to AUTO first, or you’ll get ERR from the GPC).
The shuttle will now automatically start the maneuver and constantly maintain the Z axis (the up/down axis of the shuttle) pointing on the target CG (in this case the ISS). Note that the rate of the motion never exceeds the DAP rate setting and that 0.1 Deg/s is the rate we need to maintain, which makes our job very easy, all we need are X translations to keep the cross in the PL1 cam on the ISS. if we go too fast, the pitch rate will not be enough to “chase down” the ISS and it will move. on the other hand, if we are too slow, then the shuttle will not be constantly pitching down, but will rather do pitch pulses every time we hit the dead-band limit for the tracker. So we are basically trying to achieve a constant 0.1 Deg/s pitch while maintaining a constant ISS position relative to the shuttle.
ISS as seen on MON1 before initiating TORF
Only thing to remember is that -Z thrusts are also a key issue, after initiating the +X burn, most of the work would be maintaining a good range and closure rate to the ISS – as required by each phase of the flyaround.
Once the flyaround is completed, switch the DAP back to LVLH, this will automatically cancel the target tracking.
Have a go at it, it’s fun!
Uri

Posted by uri_ba

Comments are closed.