Challenge Earth → Moon → Earth in less than 24 hours using default XR-2

interpird

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After significant experimentation and practice I managed to perform a sub 24 hour Cape Canaveral → Brighton Beach → Cape Canaveral flight using the default XR-2 Ravenstar (this is a significant detail as it would be much easier if you use the "trip to jupiter" ISP settings instead). The run includes a direct Brighton Beach landing at an approach speed of 7.8 km/s, a quick refuel, and a direct reentry to Cape Canaveral at a wopping 14.9 km/s at reentry interface. Flown with cargo slot 1 empty, slot 2 main fuel, slot 3 main fuel. Important MFDs not included with default Orbiter: IMFD, BaseLandAutopilot, Glideslope. Parameter settings: all enabled except Atmospheric wind effects.


There is still room for improvement and it could probably de done in as little as 21-22 hours:
  1. The ascent could be flown a little more efficiently. This leaves more dV for accelerating+braking.
  2. The TLI is ideally performed immediately after / as a part of the launch, saving some time.
  3. A manual BB landing could probably be more fuel efficient compared to BaseLandAutopilot, again leaving more dV for accelerating+braking.
  4. I think the almost full orbit around the Moon before TEI is not strictly necessary.
  5. Earth reentry velocity could be even higher. I think as fast at 16.00 km/s should be possible. No matter how fast you’re going, as long as you can find a reentry altitude where A) you don’t burn op and B) inverted flight generates enough negative lift to keep you at said altitude, you should (at least in principle) be able to make it work.
  6. Reentry/gliding could be more aggressive (Glideslope profile is not the best for this).
Another problem is that IMFD lacks the ability to set the desired PeT when doing BaseApproach→Reentry. You instead have to use BaseAppraoch→Orbit Insert, but this doesn’t guarantee you’ll arive at the correct anticipation angle, and therefore require some trial and error. I think LunarTransferMFD might be able to do this, but I haven’t yet looked into this enough.

If you'd like to try yourself, basically the only rule is that you should use the default XR-2 Ravenstar settings.
Also many thanks to both David Courtney and Dgatsoulis for their tutorials, I got a number of different concepts and ideas for this run from their video series.

All in all this was a fun challenge and I'm curious to hear what you think.
 

Marijn

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Did you have any Orbiter experience prior to august? Seems like you're picking it up really fast. Good job!
 

interpird

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Did you have any Orbiter experience prior to august? Seems like you're picking it up really fast. Good job!

Hi, thanks. Yes I did have some prior experience, although I never used Glideslope or AeroBrakeMFD before, and also never really mastered IMFD beyond 'target intercept' before picking Orbiter up again in august.
 

interpird

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Very cool flight. It's like the controlled version of "point towards it and burn" way of getting there. That reentry was toasty, I would not have the balls to fly that. What made you choose to use Glideslope over Aerobrake? I have yet to try Glideslope, it was cool seeing the reentry flown with something other than the typical Aerobrake.
Thanks! Yes exactly, as long as you don't care about efficiency I think it's the fastest/best way to go. And yes that inverted reentry is the trickiest part and I burned up more times then I can count. It's not easy but it's also not as hard as it looks once you get the hang of it. In fact, I think I actually took a bit more risk even than required (redlining the temperatures) because I did not want to overshoot the base. You can stay a bit higher up in the atmosphere and achieve similar braking when there are no time constraints. Although I also like/use AeroBrake, in this particular case I had some trouble getting lined up with the base using it, so I decided to use Glideslope instead. I think Glideslope gives you a bit more information (which specific altitude, velocity, bearing, should I have at a particular distance from the base).
 

Marijn

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You can save a bit of fuel by activating the airspeed hold autopilot right after take-off. It will then throttle down a bit. Then turn towards your launch heading and disengage the autopilot and throttle up to the max. Or leave the ap on. When you pitch up further, it will also throttle up to the max.
 

dgatsoulis

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Thanks for this challenge!
Managed to get the first leg in under 12 hours (11:38). Took 5 tries to home in on the efficiency improvements.
 

interpird

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Here's a faster run:

Cape Canaveral → Brighton Beach → Cape Canaveral in 18h54m using the default XR-2 Ravenstar.


See YouTube description for time stamps and some explanations.
 
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