May 12 report - I tried a run this morning & successfully landed:
- MECO was about 13.5 km/sec;
- successfully aligned with WIN and used the agentgonzo/dgatsoulis "point straight down" braking technique;
- however, I waited *far* too long to perform the braking - I was at 2500 km away from WIN and in hindsight should have done it at 2600 km;
- due to a slow initiation of the braking maneouver starting at 2500 km from WIN, I had to be very careful not to descend too fast - my wing temperatures in the XR-2 got into red and stayed there for uncomfortably long periods;
- therefore, I wasn't able to slow down quickly enough and overshot the base by about 40 km. Then I had to turn around and descend - but hey, it was a very gentle landing as I had plenty of time to align to the runway and bleed off speed!
- wheel stop something above 22 minutes, if I recall correctly. If I *had* been able to slow down, it might have been slightly north of 18 minutes, which is much faster than my previous record of 19:05.
I should note that I've been editing dgatsoulis' LUA script that he included as part of his KSC-WIN scenario download. It has been a good education in programming. One tool I've added helps on the ascent phase - if you are going up (vertical vel positive) but accelerating towards the ground, it uses the formulae [time = v0/accel; distance = (v0 * time) + (0.5 * accel * time^2)] to get the vertical "ceiling" we will reach. This allows for a nice ascent curve because if you invert around (say) 55-60km altitude, you want to gradually slow down so your vertical velocity is zero at around 70-71 km.
If I can clean up the code I will post my own starting scenario which will include the edited dgatsoulis LUA script...
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May 13 report (added/edited):
- tried an additional run, again with MECO of 13.5 km/sec and same technique to brake as yesterday
- much better aligned with runway, but came down way too hard (20 m/s or more vertical down, which smashed the landing gear) - unfortunately this is not therefore a legitimate run. :-(
- as soon as the gear smashed, I checked MET and it said 17:35.
- so this means I can probably do a survivable sub 18-minute run if I am careful not to make any mistakes. From now on, I will try to record the flight.
Based on my experiences on May 12-13, I can really say that at this point the *hardest* thing for me to do is to make sure that the flight heading alignment and deceleration gets you right where you want to be for final approach. The other elements of flying this race are now relatively routine and I can usually repeat the necessary steps. Even a few kilometers left/right or overshoot can add quite a few seconds to the flight, because at that point you are flying <1000 m/s so it takes a while to make the correction as you bank & turn.
What I find is that Aerobrake, though an awesome tool, doesn't quite give a precise target graphic down to within 10 km - I really have to squint to guess where that final target square ends up. I have considered trying to use GlideSlope2 for getting better runway precision... Any ideas welcome
, I didn't bother to post anything related to it, nor change the record table at the top of the thread... if you want details, let me know. Otherwise, good luck on any KSC-WIN runs for the rest of 2015!
