My Jool 5 challenge attempt

[burn_at_zero]

Made it to orbit:

Getting back, not so much:

Believe it or not, I actually got subsonic without the cockpit. If my landing gear hadn't cooked off I might have been able to land it after this. I ended up impacting at about 240 m/s and -35 m/s vertical. Takeoff speed is about 135 m/s and I have not yet been able to land it, so while it's nice to get to orbit I'm not sure this is the right track.

[burn_at_zero]

Thank you for the craft.

The first one is interesting, but a bit small. I had trouble getting off the runway but it flew quite well.

The second one is about right, but it's unstable. It has some of the same problems I've been struggling with, but I think the length and balance is better. Some fairly minor adjustments might make that one a contender.

[Nefrums]

I think that you still have to much wings and control surfaces.  

I put together a small ship that easily makes orbit with 2000 dV left in the tanks.

craft file

Control surfaces authority limiter is put to about 30%.

The flight profile i used was to turn on sas, point ship to a 10 degree climb, then at ~15km put sas to prograde lock and at 20km turn on nerv.  

This is stock, so no FAR etc..

 

 

Edited October 9, 2016 by Nefrums

[TwinKerbal]

14 hours ago, DerekL1963 said:

Hm....  Maybe you want to wait for 1.2 and the new science container?

?

Wat?

[DerekL1963]

2 minutes ago, TwinKerbal said:

?

KSP version 1.2 (which comes out Tuesday, the 11th) has a new stock science container which can basically hold an unlimited number of unique science reports.  It's a .625 meter part and weighs basically nothing.

[burn_at_zero]

Thank you for the craft.

FAR makes a pretty significant difference in aircraft behavior. The one you posted doesn't get off the runway below 240 m/s and tends to break up below 5km and above 400 m/s due to uncontrollable yaw. I tried throttling back to 20% immediately after takeoff and was able to get to about 6km and 280 m/s before losing control. {edit: I was able to get to 19km and 1100 m/s on one attempt before spinning out. Might be putting too much thrust into it; it didn't happen until shortly after I throttled back up from 30%.}

For the craft I showed above that made orbit, I started with one pair of wings and no controls. I added more surface area until I was able to take off. There are only two ailerons, which combined with torque is enough to get over 10° AoA; I had to have three tailfins or it was too difficult to keep it straight. I've tried to use two sabres and one nuke but it's not enough thrust to circularize before reentry; the four sabre + two nuke craft still struggles but can get it done.

Looks like the next challenge is something that can re-enter without losing anything important.

Edited October 9, 2016 by burn_at_zero

[burn_at_zero]

Another successful orbit, this time with nearly 1km/s of dV in the tank:

I actually landed too:

Sort of, anyway. Not bad for a crash  emergency landing at around 170 m/s and -10 m/s vertical with no front landing gear or nosecone.

[burn_at_zero]

Success. I reverted to an earlier design with more lift and a lot more vertical surface (4 rapier, 2 nuke, 1.5 shock cones per rapier), one of the craft I had gotten to orbit before.

I tilted the tail horizontal surfaces downward a few degrees, which had a pervasive effect on stability derivatives and level flight angle. It also seems to have moved the aero center further back, allowing me to place canards for better control. Upgraded the landing gear to medium, threw on a ladder and it did the job.

In short, I was able to reach a ~100km orbit and return, do a chute-assisted landing in hills, take off, reach mach 2.5, then land again without parachute assist.

Flight path was about 40° until 12km, then gradually level out until 0° at about 20km. Altitude dips a bit while building speed, but recovers quickly. Kicked on nukes around 22km, then mode switch at about 24km and 1.0 km/s. Closed-cycle got me an apoapsis of ~80km, so I kept the nukes on and brought AP up to 95km then let mechjeb circularize.

The key to landing was to start very early and set a PE of about 40km. I used mechjeb's advanced mode to hold pitch at 90° and gradually pitch down to 45° at 30km through the descent. Radiators were able to keep up with reentry heating throughout the descent. Once the air got thicker I dropped to 30°; I'd overshot KSC by several hundred km, so I had to circle a bit to find land. I tried my chutes and found the balance to be good enough.

Takeoff from medium hills while nearly empty was easy. Landing was a bit harder; I had trouble with a long slope that ended in a sharp rise and had to pitch up pretty hard. At the end of it I was able to hit the ground at about 170m/s and -5m/s vertical. Braking spun me around a bit but it stayed on the ground.

From here I'll probably see if I can decrease part count or mass anywhere, but that seems unlikely given the months I've already spent on the craft. I still need to put together a new mothership, and I'm seriously considering switching to ISRU. I have to recover the old mothership and parts so I can get my kerbals and my funds back as well, which won't be fun at all.

Lots of work, but at least it's straightforward work.

[burn_at_zero]

I've completed science collection on Laythe. The poles were a giant pain, since I completely forgot to build in enough dV for two 90° plane changes. I have about 240 screenshots so far, but that will be a couple hours' work to crop, transcode, annotate and upload.

Some general observations:

First, changing the landing gear turned out to cause trouble. The medium aircraft gear can't steer, so I had to change direction on the ground with RCS or short jet bursts.
Second, the parachutes were not ideal for full-fuel condition on Laythe. They were arranged 1:2:2 with one behind the cockpit, two on the engine nacelles (at CoM) and two at the rear of the fuselage. This led to about a 45° tail-first descent. I had to cut three of them to get a horizontal landing, which pushed my impact speed to about 18 m/s. The nukes give an alarming wobble but everything survives.
Third, in 1.1.3 kerbals experience re-entry heating even inside a closed cargo bay. Upper-atmosphere EVA reports are awkward and dangerous but possible. Don't expect to be able to walk around inside said bay; put all your instruments within reach of the kerbal while still hanging onto the door.
Fourth, it is possible to go from equatorial to 60°+ inclination with aero surfaces in the upper atmosphere. I saved about 1500 m/s of plane change dV by dropping from an elliptical orbit to 40km peri; entered and stayed rolled to the left and pitched back about 30°. Had to fly the rest on rapiers, which sucked down quite a bit of fuel (~600 LF). If I had the patience and foresight I could have chosen a higher peri and made multiple high-altitude passes; there was probably enough energy in the orbit to get all the way to a pole.
Fifth, my modular lander turns out to be a great rescue tug. It's autonomous but has three seats. T/W is good and it has about 4800m/s dV. I didn't put any RCS on it, which was terribly annoying. I've had to rescue the spaceplane twice now, as I didn't want to waste the fuel to put the mothership into low orbit and the plane just doesn't have the dV to reach a high elliptical orbit. That polar inclination change is just brutal.

Can't wait to finish the last of the Laythe maneuvers so I can ditch the planes. I'll leave them docked to each other in Laythe orbit, but the two of them represent something like 40% of my parts at this point. Looking forward to the FPS improvements.

I wish I would have brought some other modular parts, like maybe an x16 LF tank with docking ports and a simple single-nuke propulsion module. I brought way more oxidizer than I'll need, but not nearly enough RCS fuel. (I was expecting to make four Laythe landings at 880 O each, but I only needed two landings and one of them reached orbit without using any O.)

[burn_at_zero]

Completed Laythe cleanup. 201 science reports are sitting in the main lab. There are definitely things I missed, but I've gotten a lot of data from every biome.

The two spaceplanes (66 tons of mass between them) are in elliptical Laythe orbit. I left them with enough monoprop to dock with a tanker later, if I don't fix their design issues and send new ones.

Transferring out of this orbit took only 7 m/s. I had to look ahead a bit, as the MechJeb porkchop plotter doesn't play nice if the orbit isn't round. Still, I got a Tylo intercept in under a week. Didn't notice until after the burn that it was a *retrograde* tylo orbit, so I burned another ~350m/s to correct. Regardless, I'm now in an elliptical Tylo orbit. Still way under the ~1300 m/s indicated by the dV maps, though there are added propellant costs for the landers. I'll probably use this approach in the future if I ever have a complex mission and simply plan for some extra lander dV; the propellant savings for a large mothership should more than offset the extra consumption for a small lander.

Next steps are to assemble a lander with boosters and use the other lander to deliver it to 30km circular (~800 m/s each way). Then I'll land, collect data, lift off, stage, circularize, dock and rendezvous with the mothership. Hopefully I can hit a biome boundary so I can collect samples from a couple of places, because I only have enough boosters for two landings. It was always a long shot to hit every Tylo biome even with a rover, so we'll have to see how that affects the final tally of science. Given what i went through on Laythe there's almost no chance of pulling off a Poles landing on Tylo.

Little did I know, my boosters are welded to the docking ports on the mothership. No amount of save file tweaking will release them. Looks like my somewhat unorthodox construction techniques make ships very sad. I tried installing stockbugfix which is supposed to have a 'force undock' option in addition to other docking port fixes, but no luck. I've spent about two hours trying to manually map the ports together properly. Next chance I get to play I'll probably have to HyperEdit boosters into position and use the cheat menu to destroy the 'stuck' ones. Hopefully that's not a disqualifying act; normally I'd post the save file and ask for help but it's something like 270,000 lines of config and 67 docking ports to muck through. I've already tried the obvious things like changing state to Docked from Active, making sure each port is referred to by at most one other port and setting the active flag to true for the undock action.

Once the big beast is out of the way I'll have to decide whether to base from Tylo or relocate.