Challenge Hall Base to Olympus

[blixel]

You are in the XR2 at Hall Base on Phobos. Take off from the base and land as close to Olympus as you can within the allotted time.

The usual challenge rules apply:

• Do not refuel the vessel
• Do not add any more LOX or APU fuel
• Do not egress any of the crew
• Must keep the CHM in the XR2 at all times

The clock starts ticking as soon as you turn off External Cooling. You have 2 hours and 35 minutes to land.

I don't have any LUA scripting to go along with this challenge, so we're on the "honor system" here.

Good Luck Commander!

Requirements:

• XR2 Ravenstar
• [ame="http://orbithangar.com/searchid.php?ID=5867"]Hall Base[/ame]

Installation: Unzip the zip file to your main Orbiter directory. (There are 2 files. One is the scenario file, the other is an xrcfg file.)

Success will look something like this:

-----------------------------------------------------------------SCOREBOARD----------------------------------------------------------

Top |

XR2 Ravenstar​

| Pilots

#​

|

Name​

|

Time​

#1 |

SanderBuruma​

|

1h 10m 25s​

#2 |

dgatsoulis​

|

1h 56m 45s​

#3 |

blixel​

|

2h 24m 55s​

#4 |

​

|

​

#5 |

​

|

​

 

[dgatsoulis]

Thanks for this challenge blixel. Quite an interesting setup with limited time and fuel to get to the base. Here is the result of my first attempt:

1 hour 56 minutes 45 secs. Wheels stop ~600 meters away from the base with a (sloppy) deadstick rollout landing. Will give it another try tomorrow. :tiphat:

 

[blixel]

1 hour 56 minutes 45 secs....

WOW! When I set this up, I thought my time was really close to the best possible time. Great job!

 

[SanderBuruma]

please forgive me my act of necromantic impudence if it is, but I tried this challenge and managed to find a ReA of 25° hitting 25km altitude in about 1h 4m of flight time and touching the earth at 800m/s ground speed a few minutes later. Top vertical velocity was -1.7km/s and not crashing into the martian surface required putting the game at 0.1x timewarp and starting at an AoA of 17° and gradually increasing to keep wing load skimming just a tad away from critical while increasing drag as much as possible until the point where the craft was down to a manageable vertical and horizontal velocity.

I'm not a skilled XR2 lander, especially not on Mars and this time was no different unfortunately. I probably should have killed more ground speed before landing, when I did I kept bouncing off the surface and couldn't break with my gears.
If I recall I touched land 12km east of the base and kept on gliding on and on and on because my gears eventually broke off skidding and skidding till I was 125km+ away.

ps. I hope I correctly attached the playback

 

[blixel]

please forgive me my act of necromantic impudence if it is,

No worries. The necropost policy doesn't apply to challenges

but I tried this challenge and managed to find a ReA of 25° hitting 25km altitude in about 1h 4m of flight time and touching the earth at 800m/s ground speed a few minutes later. Top vertical velocity was -1.7km/s and not crashing into the martian surface required putting the game at 0.1x timewarp and starting at an AoA of 17° and gradually increasing to keep wing load skimming just a tad away from critical while increasing drag as much as possible until the point where the craft was down to a manageable vertical and horizontal velocity.

I'm not a skilled XR2 lander, especially not on Mars and this time was no different unfortunately. I probably should have killed more ground speed before landing, when I did I kept bouncing off the surface and couldn't break with my gears.
If I recall I touched land 12km east of the base and kept on gliding on and on and on because my gears eventually broke off skidding and skidding till I was 125km+ away.

That was a great run! Wow ... 1 hour 7 minutes and some change!! Are you kidding me!?!?

 

[SanderBuruma]

now how did you manage to actually land?? I still cant manage it without losing my landing gear!

I gave it another go this morning and came to a stop 3km east of the base. I retracted my gear for some improvised lithobraking to go from 200m/s to 0m/s, at which point I used hovers to gain altitude to deploy the landing gear again ^^. I ended up within walking distance of the base, which was visible on the horizon. Phobos -> Olympus took about 1h 10m. How do you make it so you can actually use your wheel brakes?

 

[blixel]

now how did you manage to actually land?? I still cant manage it without losing my landing gear!

I gave it another go this morning and came to a stop 3km east of the base. I retracted my gear for some improvised lithobraking to go from 200m/s to 0m/s, at which point I used hovers to gain altitude to deploy the landing gear again ^^. I ended up within walking distance of the base, which was visible on the horizon. Phobos -> Olympus took about 1h 10m. How do you make it so you can actually use your wheel brakes?

Sounds great! So you got it down without folding the gear, right? At 1h 10m? I'll put that in the score list as the best time if that's the case.

Press . (period) and , (comma) to use the wheel brakes. Note that braking is directly tied to your frame rate. The higher your FPS, the less braking you get. In the Video tab for Orbiter, I uncheck "Disable vertical sync." which locks my FPS to my monitor's refresh rate. That forces my FPS to not go any higher than 60 which gives me a lot more braking than I normally get when my FPS is at 400-600 or whatever.

Hopefully in Orbiter 2014, the braking won't be tied to the FPS.

Anyway, here's a video a made when I did this flight. Your time is WAY better, but perhaps you'll still find it interesting.

 

[SanderBuruma]

IMFD BaseApproach can plot a course that'll take you to 25km altitude 8° West of Olympus at a ReA of 25° in about 59m 14s for a dV of 1.455km/s. The time can not be much shorter. An Olympus landing should be theoretically possible within 8min of touching the atmosphere, pushing all the limits to the max.

I'm a little concerned with the realism of braking on the Mars surface though... considering its not a uniform featureless surface IRL.

1h 30m is probably more realistic for a retro/hover landing considering whats possible with what you've got.

Thanks for your video, I think I saw what I need in order to make a proper landing.

I noticed you overshot your target in the video, I think if you like math as much as I do you can use V^2/2Acc (Velocity squared/twice your acceleration or decceleration) to calculate how far you'll go if you slow down at a constant rate, even on the fly once you get familiar with it. If you know velocity and your breaking rate you can calculate before when you need to start braking, the formula is simple enough to use even on the fly.

The math I did on the fly for this challenge was 2.2km/s squared divided by 2*0.105km/s vertical acceleration... giving about 25km, this is just about enough to not hit the surface since you can reach that VAcc rate at about 25km. If you make this single calculation in advance you can use math logic to determine whether you're on track to hit or not hit the surface by checking your altitude once you lose 30% of vertical speed (which is the square root of 1/2). (at the 1.56km/s mark). If it is half of 23km, you're perfectly on track to merely brush the martian surface.

 

[dgatsoulis]

@SanderBuruma

Very nicely done! :thumbup:

My best run was about 1h 20min using a similar method, but I had some trouble figuring out the correct altitude to perform the aerobrake.
That [math]\frac{V_{vert}^2}{2 \cdot V_{acc}}[/math] formula is pretty handy.
The hard part of this mission in not getting quickly at Olympus. You can get ~10°-15° away within 1 hour from launch. It's the stopping in time part that's difficult.

 

[SanderBuruma]

I'll agree with that, the thin atmosphere makes it hard!

 

[SanderBuruma]

I tried again and this time I think I may have made a new record.


Barely didn't make it onto the pad, and I broke off my radiator at some point I don't recall, I hope this doesn't disqualify me from making the high score list.

 

[blixel]

I tried again and this time I think I may have made a new record.
View attachment 12900

Barely didn't make it onto the pad, and I broke off my radiator at some point I don't recall, I hope this doesn't disqualify me from making the high score list.

New record for sure! No worries about the broken radiator. Small technicality but definitely not a crash. What happened in the first playback? Did you fall asleep at the computer?

Great flying, thanks for your interest in this challenge. I made this challenge before I knew how to use IMFD, and with TransX, you don't seem to get a lot of information from the MFD itself.

BTW - if you enjoyed this challenge, I think you would really like dgatsoulis's Martian moons tour challenge as well. It's right up your alley.

 

[SanderBuruma]

the first time through something went wonky with the attitude AP and I crashed so I played the playback through to that point and tried several dozens time again from that point until I got to my final successful attempt.