Question Post your built-in challenge scores

[Zamzara]

Challenge 1 (Launch and Dock): 5927.23 kg used
Challenge 2 (Earth-Luna OB1): 2579.04 kg used
Challenge 3 (Earth-Luna OB1): 3338.85 kg used
Challenge 4 (Reentry): 387.5 kg used (0 kg main / 3.7 kg RCS remaining)

 

[Tommy]

Haven't had time to spend on these yet, so haven't done challenge 2 and only had time for one try at one and three. Challenge four took a few tries to get right, though.

#!: 5498.1190888824 kg used
#3: 2591.8406060728 kg used
#4: 332.61403053105 kg used

I'm pretty sure I could improve on these scores with some practice, though.

BTW, Congratulations on successfully completing challenge #4, It took me five tries just to get back to earth, and missed the runway by about 50k the first time. The script accepts that, but the score I posted is for a "true" win with a safe runway landing.

 

[ivan_w]

#1 : 5829.47

Not an exceptional score.. But it was my 4th attempt at docking with the ISS - (2 failed miserably, 1 test run.. And 1 in the Challenge)

Here is what I do now :
- Start with a low profile ascent (~100K Alt, 380K AP at MECO)
- Adjust Ecc at next AP (350/380 usually good enough)
- Align planes (Takes 1 orbit if launch was done right)
- Sync orbits At PE if in front or target, AP if behind target
-- Adjust PEa/APa on next AP/PE to match target Alt
-- Adjust APa/PEa for timing (until <1 Sec) and then wait.. (Or rather Time warp). - When distance <150k, turn to XPDR Docking mode
- 30 Secs to RDV, nullify Delta V.. Should be ~2k or so from ISS
- Docking : Go within 300m of ISS lined up with docking path, Kill Delta V in RCS Lin mode, Adjust alignment in RCS Rot mode
- Then forward in RCS Lin mode until docking.. (I couldn't believe how happy I was when it worked the 1st time !)

 

[Tommy]

#1 : 5829.47

Not an exceptional score.. But it was my 4th attempt at docking with the ISS - (2 failed miserably, 1 test run.. And 1 in the Challenge)

That's a very respectable score for a newer pilot. You have obviously managed to avoid making many of the common mistakes (ie, poor launch plane or azimuth, etc).

Your score should improve with a bit of practice - one of the reasons for my score is that I've gotten good at reaching orbit with less than a half degree of RInc.

Might I also suggest an even lower ascent profile? I usually have MECO at about 70k, with a PeA just over 200k. I'll stay in the 200k parking orbit until about 1/6 orbit behind the ISS, then I'll raise my ApA to meet the ISS's PeA (or there abouts - I use non-spherical gravity sources, so things wander a bit). Also, ALWAYS play "catch-up". To let the ISS catch up to you means raising your orbit above the ISS, then lowering it back down to rendezvous, which is a bit wasteful.

 

[ivan_w]

I haven't turned on 'oblate earth' mode yet. I'm going to stick with a round earth for the time being I think (PS : I *did* watch the 2010P1 demo with non spherical rendez-vous.. but I'm not there yet !)

Frankly hadn't though of launching late (or rather behind) and then just keeping a low orbit to play catch up - which should obviously save some fuel since I won't have to go that high. Then going into a low Ecc orbit and raising APa to target's PEa when being opposite to target's PEa - Not only does it save a step, but it also saves fuel!

I was just worried about synchronizing the orbits - but then again it's just a matter of tweaking my own PEa (probably just with RCS in trans mode) then when reaching my own APa - which should target's PEa at that point.

.. You can tell I'm new to this.. Just starting to get my hands on orbital dynamics - Or rather Orbiter Sim's image of it (which as far as I have read seems pretty accurate) - And all of its counter-intuitive stuff - like you have to accelerate to go for a longer time around & stuff like that.

Frankly, I pretty much use all the MFDs at hand (Map for launch, Orbit for ascent and then Planar Alignment, Orbit Sync, NAV & Docking + HUD readouts (because I always get the controls backwards otherwise)).. So I still have a lot to go when I read people pretty much doing it by hand or in their head.

Anyway.. Thanks for the heads up!

--Ivan

 

[Tommy]

You are definitely on the right track. One tip that may help is using AlignPlanesMFD to determine launch time. Select ISS as the target, and watch the TN. Keep in mind that Sync is assuming both you and the target are in orbit. Since you are landed, the TN (Time to Node) displayed will NOT be accurate, but it's still fairly consistent in it's "error". In other words, just because TN displayed is, say, 300 seconds doesn't mean you will reach the node in 300 seconds (it will actually take a bit longer). However, as I said, it's consistent. Therefore TN can still be used as a reference. I find that launching when TN = 300 provides quite good results (less than 1/2 degree RInc) with the stock DG (about 360 for Atlantis). Launching into an orbit with very low RInc is the single most crucial element to getting a good score on this challenge. From the score you posted, you are already doing pretty good at this!

I can promise you that there are more than a few people here who consider themselves "advanced Orbinauts" that couldn't score as well as you did.

 

[dgatsoulis]

Lazy Sunday morning today. I found some time to give the challenges a go.
The only one i had tried before, was challenge #4.

Here are my scores:
#1: 5688.64 (second attempt)
#2: 2389.32 (first attempt)
#3: 2801.78 (first attempt, the second one was close to that too).
#4: 384.34 (Stopped counting after the 8th or 9th attempt, :lol: )

@Tommy: WOW! 5498,119 on the first challenge!? Amazing work!:thumbup:

 

[Tommy]

Tommy: WOW! 5498,119 on the first challenge!

Thanks. I've made well over a hundred ascents and dozens of "test" flights to gather drag data while coming up with my ascent profile - it's nice to see that the effort has paid off. Managing to get the launch perfectly in plane certainly didn't hurt either! Also, you'd be surprised how much fuel the AP's can waste - you can easily save over a dozen KG by orienting the vessel by hand before engaging an AP.

 

[dgatsoulis]

@Tommy: I have to admit that when i first saw your score on challenge #1, I thought that there might be a slight chance, that you have misspelled "1" (!) with "@"... :lol: )... (my hopes were up!)
At first... i didn't think that ANYTHING below 5600 kg could ever work. That's simply because.... there's NOT ENOUGH fuel! (according to FUELmfd. - which of course, is designed for bodies without an atmosphere).

Thank you for the tips!
(That 70k X 200k orbit was particularly helpful!)
I haven't managed to beat your score... (eventhough... i've spent most of the day trying...) but i did get really close! ) A mere 30 kg.

P.S.: My girlfriend is -again- "officially" breaking up with me...
:lol:

 

[Tommy]

Thank you for the tips!

You are more than welcome. Thank you for trying my advice, I feel vindicated. I've been advocating this ascent profile for months - and meeting a lot of skepticism. "Common Wisdom" seems to dictate that you want to get out of the atmosphere as quickly as possible, and ascent profiles are quite a bit steeper than mine. Most people seem to think you want to maintain a high pitch angle until over 30k, and are usually still at about 30 - 40 degrees at 100k.

Countless test flights have shown me that a high pitch angle is only good for the first 10k altitude, followed by a gradual transition to about 5 - 10 degrees by 25k alt. It's actually quite close to the ascent profile used in a scram ascent in an XR-2, perhaps 5k higher at any given velocity. In fact, I only pay attention to pitch angles during the initial pitch-up (to 75 - 80 degrees). After that I pay attention to the VS, not the pitch. Generally speaking, VS targets are about 200ms by 25k, 150ms by 30k, and about 100ms over 35k alt.

This post outlines some of the reasoning behind my ascent profile:

http://orbiter-forum.com/showpost.php?p=203022&postcount=33


EDIT:

This thread contains a better description of the ascent profile I've been developing. It's a bit dated, and the profile has been tweaked slightly since then, but this is close:

http://www.orbiter-forum.com/showthread.php?t=9587

 

[jthill]

I get pretty close to the same ascent profile (about 75k MECO and 7.5k fuel remaining in the catch-up orbit) by paying attention to DNP - the idea being DNP and velocity have to support VAcc (which is nothing but excess lift). The lowest sustainable DNP will provide the least sustainable drag. Once you're in the stratosphere VAcc and DNP will keep each other in line and you can just trim it full up and hit T if you don't want to get fussy. It's surprisingly forgiving.

The DG likes 14 DNP or so in the troposphere -- I try to peg that during initial climbout and anticipate it through the boundary layers at 10 and 20 km. The DGex likes 8 or so, the DG4 about 10.

 

[Jaws]

Thanks Tommy

Just managed a score of 5495.0097405413 on my second try using your suggestion. Found that if you boost up to orbit just below the ISS (like 1km or so) then hit fast forward one will eventually catch up to the other. This might take many months in real time but you get there eventually.

Without using any RCS whatsoever after reaching this orbit, I somehow managed to coast to within 12km of the ISS with a closing velocity of only 9 m/s.

Thanks again for the tip! :thumbup:

 

[flytandem]

Challenge 3. 2575.95 Kg used. A fun 45 minutes with Orbiter. Larger MCCs than I had hoped for. Maybe I'll try it again.
edit: 2nd try challenge 3= 2503.91 Kg. Definitely fewer errors. Hard to shave much more than that I think. Maybe 2450 is possible??

 

[Tommy]

Looks like I'll have to try #3 again. IIRC I had room for improvement on getting my plane aligned with OB-1 - used more fuel for the PlC than I would have liked. I'll need to figure out a way to place the node in a more efficient place.

 

[hribek]

Challenge #4 - about 310 kg used. The playback should show something like 316kg (biggest inaccuracy is due to the gradual engine cutoff). I haven't used more than 1 kg of fuel from the RCS tank for the entire flight (attitude change usually takes 0.05 kg tops, since you have plenty of time).

The playback contains IMFD delta velocity plan, with IMFD Map program showing the predicted trajectory. It's a lunar gravity assist, PeA down to ~2M, then on the second orbit it gets down to 80km as predicted (I guess the Moon being on the opposite side of the Earth and high orbit ecccentricity might have something to do with that, plus Sun). The only course correction I made was PeA adjustment from 80km to 70km. then I only used a fraction of a kilo of propellant for killrot and two attitude adjustments on entry (first for the inverted circularization and suborbital skip, second for "regular" entry over the Gulf of Mexico). Touchdown was a few minutes before midnight (GMT) 26/27 January.

With this trajectory plan, it is possible to return to Earth on the first orbit using a 10 m/s burn at perilune.

View attachment Challenge_4_dv1104.32.zip
Required addons: IMFD

 

[dgatsoulis]

Challenge #4 - about 310 kg used.

Very, very impressive! :thumbup:
My latest best effort was 320.77079492952 kg of fuel used. (and about 7 more kg used in the playback)
Right now, i'm trying to reproduce your plan in TransX, and see if i can do any better.
But in the attempt to do that, i saw this: How about instead of going around the Moon, we get close enough to the Moon's gravity pull, to get our Pe as close to Earth as possible?
My first couple of flights got me as close as to 1.1M with only 1053 dV. (i time-warped to the next node).

 

[Tommy]

How about instead of going around the Moon, we get close enough to the Moon's gravity pull, to get our Pe as close to Earth as possible?

That's the method I used - and a very short second burn just as I left the Moon's Soi to further reduce the PeA (sort of "seat of the pants" for the attitude, but generally in an Earth Retrograde direction.

 

[dgatsoulis]

Thanks to hribek's excellent example of the IMFD's Delta Velocity and Map programs, i was able to complete this challenge using only 298.47kg of fuel.

The whole flight was done in a single burn (1061 m/s), no corrections were needed.
First, i used TransX, to find a cheap plan to the moon with a PeD of about 6.500M back at Earth. Then, i reproduced that plan on IMFD, so that i could see more accurately, my trajectory at Earth Periapsis.

I'm attaching the playback here, which also has the IMFD plans.
Fuel used in the actual flight: 298.47 kg
Fuel shown on the playback : 302.30 kg

Have fun, happy orbiting


CLARIFICATION: This flight was made with the "Gravity-gradient torgue" and "Non spherical gravity sources" checked, in the Orbiter launchpad.

 

[flytandem]

(snip)The whole flight was done in a single burn (1061 m/s), no corrections were needed.(snip)

bingo.:thumbup: that's what was intended as the best way to maximize efficiency of this challenge. It's actually the simplest of all the challenges as far as how much "piloting" is needed, but the most complicated as far as navigating. my guess is that if it's done with less deltav, it will only be by a couple of Kg.

 

[dgatsoulis]

I had another go at challenge 3, result: 2460.89 kg of fuel used. (2480 in the playback). Definitely room for improvement there. I think it can be done with about 10-15 kg less. Playback attached.

CLARIFICATION: This flight was made with the "Gravity-gradient torgue" and "Non spherical gravity sources" checked, in the Orbiter launchpad.