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Old 12-06-2008, 06:54 AM   #1
Arrowstar
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Default KSC to Ascension

I preparation for the Orbiter Rocket Racing League, I felt it necessary to begin honing my technique for this particular flight (KSC -> ASC). I'm happy to report that after a number of tries, I successfully made the flight. Though, I have to say, Altea is not going to be happy... three of their new XR2s are now at the bottom of the ocean in pieces.

Take Off
Take off was from KSC using one of the Skin scenarios with the XR2. At loaded my payload bay with some main engine fuel and unloaded the other two slots. I then punched the throttle, rotated shortly after Vr, and immediately came to heading with Ascension. After lining up, I cranked back on the stick in order to get some altitude under me.

ScramAfter achieving Mach 3 and 40-50KM, I opened up the SCRAM doors and punched the throttle there. Why so early? Turns out you won't use the entirety of the fuel as it is. Might as well burn it.

Cruise
I managed to get into a suborbital trajectory at 80 KM with a speed of 6.8 KM/s. I opened the payload bay doors, dumped my fuel container (now empty), and opened the radiator for a bit. I also dumped the rest of my SCRAM fuel, deciding that the wieght reduction would help more with reentry.

Reentry #1
Things began to heat up here and I managed to reduce my speed to about 5 KM/s. At this point I was really getting pretty close to ASC, so it was about time. I was sitting at 60 deg AOA for most of the re-entry, primarily because I found I was getting too hot and the only way to counter that was to punch the throttle and reduce descent rate. It worked out, however, and I survived. Not without a few of the temperature readings going red for a few seconds, however...

Reentry #2
After coasting a bit, I began to reenter again. By the end I had my speed down to about 3 KM/s or so. Somewhere in the middle of this re-entry I had to pull the same nose-up trick and hit the throttle to save myself. I didn't quite manage it and took a fair amount of structural damage on the port wing, including the aileron (this actually failed and went gimpy on me). Limping now, I managed to line up with the runway some distance off.

Final Approach and Landing
Bouncing around with my broken wing made things a bit harder, but ultimately I managed to keep my speed up around Mach 2 and my altitude around 5 Km for the remainder of the flight. As soon as I got into range with the ILS, I let the throttle out and began descent. Landing was a bit difficult, as I didn't have a left aileron to assist in bank, but I stilled touched down slightly left of the center line and headed mostly straight. Airbrakes were out of the question, as the left brake would not deploy. I did scoot off the runway at the end, but I put that down to my vessel's steering and not my piloting.

Ulimately, I made the run in 2190 seconds. How does that compare to anyone else's run? Also, does anyone see any way I can improve my flights?

I found the biggest challenge was keeping speed as high as possible (hence flying above the atmosphere for most of the trip) while also taking into consideration the immense thermal issues you see in the XR2 on this kind of flight. It's all about energy management.

Ultimately a great flight that really challenges you to go fast (but not too fast). I'm looking forward to working on getting that time down!
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Old 12-06-2008, 11:21 AM   #2
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I just made it in 2292 seconds. I'll try out some different ways now.
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Old 12-06-2008, 11:47 AM   #3
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Ah great to see some people tackling this flight, sounds like you really tried to stretch the envelope! I think your flight, arrowstar, is a great example of the challenge the KSC-Ascension holds and the potential for fine tuning.

Be interested to see other's attempts here too.

Once Wideawake International is released (tomorrow), i will turn my thoughts and limited dev time to the ORRL stuff.

cheers and good luck all.
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Old 12-06-2008, 12:51 PM   #4
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I've got 2021 seconds now.

After the launch from KSC with two main fuel tanks (removed from payload bay when empty) I used scram and main engines to get up to 75 km at 7,400 km/s. After that I used the hovers to maintain that altitude. About 1800 km away from Ascension I turned retrograde to brake with the main engines. I lowered the hover throttle a bit to get down slowly. After crossing the base the main fuel was depleted and I closed all doors to get down, speed was about 400 m/s. Wheel stop was at 2021 seconds.
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Old 12-06-2008, 03:31 PM   #5
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Not bad at all. I think the key really is to get above the atmosphere, punch the throttle as much as you're able, and then kill all that speed at just the right time so your re-entry angle doesn't kill you. Like I said, I flew my sub-orbital trajectory at 6.8 Km/s, but by flying at 7.4, maybe you saved 100 seconds or so.

My 3rd attempt of this flight (above described was 4th) was at 7.4 Km/s, but I didn't get the re-entry right and I died.

Quote:
Ah great to see some people tackling this flight, sounds like you really tried to stretch the envelope! I think your flight, arrowstar, is a great example of the challenge the KSC-Ascension holds and the potential for fine tuning.
Yes, needless to say, my personal XR2 has some, um, burn marks on it now. This is what happens when flying with the hull temperature red is SOP.
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Old 12-06-2008, 04:05 PM   #6
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At least yours is still in one piece. There is a mounting spacecraft graveyard in the South Atlantic due my repeatedly failed attempts!
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Old 12-06-2008, 04:16 PM   #7
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well I just tried it but I failed I opened the Retro Thruster door
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Old 12-06-2008, 07:09 PM   #8
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Yeah, door management is pretty intense in this flight too. SCRAM doors especially. Keep 'em open until they overheat, but if you don't get them closed ASAP, you'll lose them. My second flight died from SCRAM explosion. I've used the retro doors a little bit, but primarily you need to get it right with the mains the first time or you're dead anyways.


-----Post Added-----


I just completed the Ascension run in 1780 seconds! That's ~400 seconds shorter than my last run! Woo hoo! Screenshot and some explanation of technique to follow.

Woo!

See attached screenshot.

My trick here was weight reduction. Before took off I reduced my O2 supply to 11 percent (it squawks at you at 10, I or it would have been lower ), my SCRAM to 50 percent, and my RSC to 30 percent. APU was also reduced to 30 percent. (I almost ran out!) I kept main fuel full plus added one main fuel container to the payload bay. I apogee was around 80 KM and max speed was 7.55 KM/s. I spent the last half of the flight in nothing but thermal management mode, trying to keep my hull temperature down. I was running high greens for the most part. In the last few minutes of my flight as I approached ASC closely, I was moving at 1.4 KM/s at 5 KM in altitude... you get toasty moving at that speed! Needless to say, I have never dove to the runway at over 1 KM/s before... those speedbrakes sure do come in handy!

This was easily the hottest run I've EVER done in the XR2. But ultimately a lot of fun. There were definately some tense moments around 50 KM when I seriously thought I was going to break up. But I survived nonetheless. Looking forward to the League!

EDIT: I just realized I have some proof on that screenshot for how fast I was coming in. You can see I took the screenie at wheelstop... look at my temperature readings!
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KSC_to_ASC_in_1780s.jpg  
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Old 12-06-2008, 07:41 PM   #9
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Whoa thats fast! I have to try out it again.
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Old 12-06-2008, 09:10 PM   #10
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Quote:
Originally Posted by Arrowstar View Post
 Reentry #1
Things began to heat up here and I managed to reduce my speed to about 5 KM/s. At this point I was really getting pretty close to ASC, so it was about time. I was sitting at 60 deg AOA for most of the re-entry, primarily because I found I was getting too hot and the only way to counter that was to punch the throttle and reduce descent rate. It worked out, however, and I survived. Not without a few of the temperature readings going red for a few seconds, however...

Reentry #2
After coasting a bit, I began to reenter again. By the end I had my speed down to about 3 KM/s or so. Somewhere in the middle of this re-entry I had to pull the same nose-up trick and hit the throttle to save myself. I didn't quite manage it and took a fair amount of structural damage on the port wing, including the aileron (this actually failed and went gimpy on me). Limping now, I managed to line up with the runway some distance off.
Maximum lift is around 15 degrees or so, beyond that, pitching up actually decreases lift. So pitching up to 60 degrees to try to reduce decent rate is a very bad idea. Punching the throttle is probably what saved you, but a better idea would have been to hold things as close to 15 degrees AOA as you could get without putting too many g's on the ship.
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Old 12-06-2008, 09:15 PM   #11
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Well, at that point I was trying to get my engines into position to fire. The most effective angle of attack for lift was not really what I was going for.
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Old 12-06-2008, 09:28 PM   #12
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I just made it in 1645 seconds! These 135 seconds shorter seem to be because of removing the whole crew and only leaving Comander and Pilot onboard.
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Old 12-06-2008, 09:33 PM   #13
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Originally Posted by astrosammy View Post
 I just made it in 1645 seconds! These 135 seconds shorter seem to be because of removing the whole crew and only leaving Comander and Pilot onboard.
I just made it in 1671 myself. I know I can do better, because this flight had some issues (see screenie). Primarily, I overshot and had to turn around. This put me off the track for the runway and I had to re-align and whatnot. Also took left-wing and left-SCRAM damage on this flight. But that's what you get for pushing the envelope...

My conclusion is that this can be done by a highly skilled pilot in 1300 seconds. I was well on track for that before I made a mistake or two. Apparently I am not skilled enough yet.
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Old 12-06-2008, 10:07 PM   #14
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And here we are with a new best time of 1658 seconds. See screen shot. Honestly I'm at a loss as how to go faster. I may end up retracting my 1300 seconds statement up there. I was cruising at 8 KM/s for a good portion of this trip, and I dare not go too much faster. I'm already having issues stopping on target as it is!
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Old 12-06-2008, 10:28 PM   #15
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Originally Posted by Arrowstar View Post
 Well, at that point I was trying to get my engines into position to fire. The most effective angle of attack for lift was not really what I was going for.
I think you'd likely get more upward force from a good AOA than from the engines, unless the XR2's engines can put out at least 3 or 4 g's. I've not been able to get the XR2 to work on my machine. What kind of accel does it get?
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