The KSP StarRally 2012 - The Great Orbital Rendezvous Race!

[Cykyrios]

Aaaaaand that\'s it, I did it!

Thanks for the tips, though I used my own spreadsheet to calculate rendezvous timings.

I also had a bit of luck for the KSO checkpoint, which saved a lot of time and fuel.

Checkpoints and final time in the spoiler:

The craft I used, that I named 'Orbital Racer'.

Timing the launch to save precious minutes/hours (my best time is around 25 min):

After a transfer to KSO, I managed to rendezvous with checkpoint 2:

Mun orbit insertion, and my spreadshit allowed me to meet checkpoint 3 after a bit more than 2 full orbits:

I was ready to go back to Kerbin as soon as I passed this checkpoint, pretty neat:

Jeb: 'We\'re outta here!'

Bill & Bob: 'AAAAAAAAAAAAH'

Closing in towards the finish line (once again using calculus).

And the total time is 1:06:24:36.

Using the remaining (not enough, though) fuel to land near KSC.

Once again, thank you for this challenge, it\'s been pretty fun and I even managed to get and pretty good time.

Have you tried any of your bonus checkpoints yet? They seem to require a pretty big rocket to get them.

[sal_vager]

Well done thats a really good time, I haven\'t tried the bonus rings yet, I really must though, I don\'t know how big a ship I\'ll need yet

I think I\'ll need at least 3 RCS tanks, as I don\'t need RCS for landing on the Mun, and hopefully it shouldn\'t take too much extra fuel, all I need to do is fly to the edge of the system, back to the Mun to land, take off again and then get in a 45 degree orbit then back to the finish line ???

Edit:

I\'m actually feeling pretty chuffed that you had a go at my challenge, I was worried it would be ignored, then Kosmo-not and yourself have shown me my work making this wasn\'t for nothing, thank you.

[Cykyrios]

I think the lack of more people trying this is due to the complex nature of the challenge, but once you get the hang of rendezvous, it\'s more of a 'can you control your ship' problem (however, using rendezvous tables helps tremendously, but I think not too many people want to do this when they play).

I may go for 1 or 2 of the bonus checkpoints tomorrow, but I\'ll need some more powerful rocket first.

[Geeny]

Where did you guys learn how to do this rendezvous thing? And the tables?

[Kosmo-not]

Where did you guys learn how to do this rendezvous thing? And the tables?

If they are referring to the spreadsheet I made, then you can get it here.

[Geeny]

Thank you!

[Cykyrios]

I learned rendezvous on my own, burning when I got the feeling that I would end up close to the target (I still do this a lot).

I have made my own spreadsheet that allows me to rendezvous with a ship on a circular orbit at Ap/Pe after a full (elliptic) orbit, using the (approximate) angle between me and my target.

For instance, to rendezvous at 150 km when I\'m ahead of target at Pe, and the angle is 60°, I put my Ap around 312 km.

This may not be very fuel-efficient, but gets the rendezvous done quite fast.

[sal_vager]

Cykyrios, would you be willing to share your spreadsheet?

[Kosmo-not]

Cykyrios, would you be willing to share your spreadsheet?

If he\'s not, I\'ll be willing to make and share one.

[Cykyrios]

Sure, though I didn\'t make it with sharing it in mind, so it may not be that easy to understand/use. And it relies on your ability to guess angles from the orbital map

A few orbits are listed, but you can edit the yellowish cells to get a custom value. I\'ll try to explain it better if you don\'t get it.

EDIT: Updated the spreadsheet to make it easier to use.

[sal_vager]

Thanks Cykyrios, this may help others with the course, I\'ll put a link to it, and to yours Kosmo-not, in the original post.

Tools like this are great, as you can still get that sense of achievement that is lost when relying on Mechjeb and Rincomp.

[Cykyrios]

I edited the spreadsheet to make it easier to use.

I also tried the bonus 1 ring with my new rocket, and the game crashed...

I\'ll try to improve my time on the standard course then =P

[sal_vager]

I hope it wasn\'t the ringship being way out there that caused the crash, I can load it up fine with no explosions or lockups, but KSP does crash for me too at random times.

I have to keep clearing out the crash reports.

Good luck on your times, maybe you can beat me

[PakledHostage]

Well here\'s my entry. I managed 1 day, 2 hours, 14 minutes and 53 seconds with my 'Ker-Blue I' rocket. I used the 'Lite' persistence file because my computer isn\'t powerful enough to load the waypoint rings of the standard file and still maintain any sort of useable frame rate.

I think I could have shaved a bit more time if I\'d dropped back down to low Kerbin orbit after Waypoint 2 to fly my trans-munar insertion from there. As it was, I had to wait about 4 hours between rendezvousing with Waypoint 2 and my TMI. I also could have shaved a few minutes getting to Waypoint 1 if I\'d launched right way rather than fiddling around taking screen shots.

And it sounds like I used a different method than the rest of you for planning my orbital transfers. I used patched conics when planning my TMI and TKI burns, and I used very slightly eccentric parking orbits (i.e. circular ± about 0.5 km - just enough so that the PE and AP icons don\'t wiggle) to time my transfers from those parking orbits to the three waypoints. To do this, I recorded the times that the target and my spacecraft transited the major axis (i.e. when the PE, AP and target or spacecraft were lined up). I then calculated the time of my burns so that I\'d intercept my target at apoapsis/periapsis.

The standard 2-body equations were all I needed for planning rendezvous with all but waypoint 2. I used numerical integration when planning my transfer to Waypoint 2 because the angular error introduced as a result of the non-instantaneous delta-V is significant. I expected that I\'d have to resort to trial and error (or a time consuming intermediate orbit) for this transfer if I assumed instantaneous delta-V.

Here are my screen shots:

[img width=800 height=590]

http://i.imgur.com/zx2U0.png

Edit: Fixed a broken link to first screen shot.

[sal_vager]

Wow well done PakledHostage, I\'m impressed and I\'m really glad to see you made it.

All stock pilots so far as well, I think it adds to the challenge but I\'d like to see someone like NovaSilisko try this with one of his designs, you\'d have thought someone would have used Mechjeb by now too.

Your system is probably too complex for me to follow, I took a risk by swinging round Kerbin at 100km after Checkpoint 2 and got lucky with my orbit at the Mun, so if you try dropping back as well I think you could easily make it in less than 24 hours.

Most important thing though is did you enjoy it? And do you have any pointers on how I could improve the next race?

[PakledHostage]

Most important thing though is did you enjoy it? And do you have any pointers on how I could improve the next race?

Yes! Thanks for all your work putting it together. It was one of the best that I\'ve done.

It was a bit of a marathon challenge but that added to the enjoyment. Between all of calculations, manoeuvring and real-life distractions, it took me most of a week to finish. But that added to the enjoyment; it introduced a level of anxiety where, after all the work you\'ve done, you don\'t want to screw up the next stage of the mission.

As for a suggestion for future challenges? What about a 'scramble'? So far, most of us have concentrated on getting around the main race course, while ignoring the bonus waypoints. What if you were to put up waypoints in a variety of orbital inclinations and altitudes (maybe even one or two in elliptical orbits) and let players decide which order to do them in? The only condition would be that they\'d have to rendezvous with all of them before returning to the finish. Maybe also keep it to three or four waypoints?

[Kosmo-not]

I\'ll have to get back into this and make a new time for myself.

[NeoHoltsky]

Woah, nice challenge. Some of the times posted are pretty amazing so far, it\'s a bit lacking in the mod section though. I think it\'s about time we got a C7 user in here. 8) Now to go make a rather gigantic space-plane... oh god don\'t start crying computer.

[sal_vager]

I\'m looking forwards to seeing you go NeoHoltsky, don\'t forget to PM me when you\'re done just in case I don\'t see your entry here

[NeoHoltsky]

Well... derp on me. Finally got my master craft done, and did most of the challenge. Got all the way to checkpoint 3, decoupled my drop tank system that carries my main RCS system, got myself in an orbital rendevous position with the finish, and found out I forgot to put RCS on my actual Spaceplane... yeah. Ran out of fuel trying to do it with the main engine. It\'s always the little details that get me, I swear.

Great challenge by the way, really enjoyed it, most fun I\'ve had in KSP in awhile. I\'ll try again tomorrow, but for now, I think I\'ll retire to the nice, soft rectangle we call a bed.

[Cykyrios]

Well, it required a LOT of trial and error, but I finally managed to get a 'flight plan' for my rocket, which requires precise control and fast rendezvous, but it was worth it!

Using a 70 km high slingshot from KSO, and burning a few seconds after the periapsis, I managed to get to the Mun in no time at all, and finished the course in 22:15:42!

I had to adjust my orbit upon reaching KSO altitude to catch up with the 2nd ring:

I originally planned to go back around 400 km for my TMI burn, but I saw the Mun in a good spot, so I rushed just above the atmosphere to slingshot and got there pretty fast:

Only 12 hours after passing Checkpoint 2, while my original TMI was supposed to be 7-hour long, not taking the time to get down into account...

Back to Kerbin, Periapsis at 70 km, calculating a 530 km high Apoapsis:

This got me within 8 km of the finish line, so it was time to adjust my orbit again.

The thing is, when I decoupled from the 4 empty tanks, I accidentally jettisoned my RCS tanks and thrusters on the way, so I had to finish with the liquid engine:

EDIT: Forgot the picture of the craft on the launchpad; here is the Zensoku:

[PakledHostage]

Nice work and congratulations! Looks like you made up all of your time on the return to Kerbin and finish line rendezvous. My time to Waypoint 3 was 15 minutes faster than yours, but I then took over 10 hours to get from there back to Kerbin to rendezvous with the finish line.

[Cykyrios]

To be honest, your times from checkpoints 1 to 2 and 2 to 3 still impress me. I thought I made a really decent time to get to KSO, but you managed to get there alsmot 2 hours faster than me.

And if it weren\'t for that slingshot, I think I wouldn\'t even have beaten my previous time.

On my way back to Kerbin though, I put my Pe directly at 70 km and used my spreadsheet so that I would need only one orbit to catch up with the finish line (it was about 200° late from my Pe). Fortunately I guessed that angle quite well.

Anyway, if anyone manages to beat my time, I guess I won\'t try again, because things are getting pretty difficult to manage ??? (and this whole trial-and-error thing tired me a bit, too)

Edit: I just remembered how I lost time for the 2nd checkpoint: my orbital plane was a bit off, so I had to make 2 'align burns' along with a bit of letting the 2 ships get close to each other.

I\'m quite curious about how you got to the Mun in your run, too.

[PakledHostage]

To be honest, your times from checkpoints 1 to 2 and 2 to 3 still impress me. I thought I made a really decent time to get to KSO, but you managed to get there alsmot 2 hours faster than me.

The transfer from 150 km up to 2868 km only takes about 1 hour and 25 minutes from PE to AP. I used the rest of the time en route between Checkpoint 1 and 2 to measure my spacecraft’s angular displacement from checkpoint 2 and to calculate the timing of my burn based on that angular displacement. The only tricky part (and this is why I used numerical integration to plan this burn) is that the angular position of the spacecraft\'s periapsis precesses eastward by about 7.3 degrees during the burn. (The amount of this precession varies depending on the thrust-to-mass ratio of the spacecraft so it won’t be the same for you.) This has to be taken into account because even just 0.1 degrees of angular displacement error at Checkpoint 2\'s altitude equals over 5 km of separation.

For the rendezvous itself, I set my AP about 1 km higher than Checkpoint 2 to give myself a bit more 'hang time' at AP, then timed my circularisation burn to begin when Checkpoint 2 was about 8 km away. It was closing at about 400 m/s but a little grade 10 physics allowed me to work out that if I started my burn when it was about 8 km away, I\'d be up to the requisite 1009 m/s by the time Checkpoint 2 was nearing its closest approach. The calculations worked and it was just over 2 km way when I finished circularising my orbit at 2868 km.

As for the transfer to the Mun, I waited until the Mun was 86 degrees ahead of my spacecraft at my altitude of 2868 km then boosted my AP to about 13300 km. (I timed this burn by recording the time that the Mun rose over Kerbin then calculating the time required from that instant until I was 86 degrees behind the Mun.) This burn results, upon crossing into the Mun\'s SOI, in a prograde hyperbolic trajectory with Munar PE of about 70 km.

[Cykyrios]

So you stayed at 2868 km for your TMI burn. This was a bit of a concern for me as I didn\'t check whether the Mun would be at a good angle by the time I reached Checkpoint 2, so I chose to go back to LKO first (luckily I didn\'t have to circularize down there).

As for the transfer to KSO, it would seem I\'m not that bad approximating it, as I rarely end up more than 100 km away with my method (which is and has always been an approximation). I then tweak my orbit by burning neither prograde nor retrograde, but I try different angles to see the effect on the orbit, and the result can often be pretty interesting (such as moving Ap and Pe without changing their altitude by more than a few kilometers).

I\'m a bit reluctant to dive into calculations for a game, even though most of them are simple enough not to spend hours on it, but I admire the dedication you put to it