nelso

Congrats, 3000m/s at 3:48 is definitely a sign this is record breaking early on, and 24:32 is by far the best. I would give you a recommendation for that. Think it could do even better though, perhaps by 30 seconds by not doing the loop at the end. I also did another run with a craft that can carry 32 passengers, in under 30 minutes. Trying to optimize takeoffs and landings, and getting decent at quick landings. This craft has all the requirements of OP but it's a little hard to board passengers from the ladder.

In my experience the descent is really critical and can shave 1-2 minutes from the time. It's also possible a reverse powered descent is optimal, which would mean the backward-moving COM isn't so bad. It is a more complex maneuver and closer to what spacex wants to do with the starship. I've also considered using an inflatable heat shield as a nose cone.. superior heat resistance (3500k) but don't know about the aerodynamics. Also if inflated it can't be deflated. Very nice and congrats. I was trying an automatic takeoff for my most recent huge craft, but I couldn't get the right attack angle in the 10000-15000m range to maximize airbreathing fuel usage, while also getting above that range when I reached an optimal speed.

Those are some good ideas. I did not know that about MK2 parts. I did manage to roughly tie your time (about 26:29) with a vertical ascent and landing craft and cruise maxing out at 3250.5m/s (at ~18:48) (with comfortable heating, just didn't have the fuel and thrust to go faster). It lands on the tail, not quite on the runway but close. I had shock cone intakes closer to the central axis of the craft which I believe greatly reduces the heat. For the nuclear engines, I used shock cones and 2 ncs adapters cause of their heat tolerance. There is another optimization which is to use ion engines to get just a little more thrust. The nuclear engines provide enough electric charge to run some of them, but I didn't use this.

Very nice and congrats! I guess you fly upside down because the drag from the tail fin helps rotate down, and optimized drag to maximize the use of the nerv. Craft looks great too and it looks like you really tweaked it. Guess I will have to try some new approaches to get faster than that, but it will certainly be tough.

Thanks, this was fairly challenging and took quite some time (many failed approaches in ship design), although after a while I got a sense of how fast I needed to be going early in the run: 2650m/s at 3 minutes was my goal, with about 20 minutes of nuclear fuel remaining. My goal was less about going faster during the cruise - every 50m/s faster is only about 30 seconds off the final time, but consumes a lot more fuel. Also note this was 43 tons so in the higher mass category. It was easier to balance numbers of engines, intakes, fuel/engine weight balance, and aerodynamics, and had a higher mass to drag ratio, so a quicker descent and presumably better aerodynamics in cruise. I think it's possible to shave off another 2 minutes using a powerful rocket for ascent, that's probably the 80+ ton category. You said you were having trouble with kRPC. I found kOS language awkward, but no reliability problems, just had to restart the script when loading a save. Here is my script, it's a "PD" control of orbital energy (factoring in speed and altitude) and another PD control for altitude. This already has the particular issues worked out like disabling SAS while using it, and giving back control to the player when exiting (by pressing any key). It's configured to retrograde, but changing the 270 to 90 will allow prograde. PRINT 1234. SET gui TO GUI(200). gui:SHOW(). LOCAL label IS gui:ADDLABEL("Low Orbit Autopilot"). SET label:STYLE:ALIGN TO "CENTER". SET label:STYLE:HSTRETCH TO True. gui:ADDLABEL("Altitude"). LOCAL field1 IS gui:ADDTEXTFIELD("33000"). gui:ADDLABEL("Orbital Speed"). LOCAL gui_speed IS gui:ADDTEXTFIELD("2360"). UNTIL SHIP:ALTITUDE > 4000000 { //PRINT SHIP:VELOCITY:ORBIT:MAG. SAS OFF. SET targheight TO field1:TEXT:TONUMBER(33000). SET targspeed TO gui_speed:TEXT:TONUMBER(2360). SET targthrottle TO (targspeed^2-SHIP:VELOCITY:ORBIT:MAG^2+(targheight-SHIP:ALTITUDE)*20)*.0005. LOCK THROTTLE TO targthrottle. SET pitch to MAX(-14,MIN(14,(targheight-SHIP:ALTITUDE-ship:VERTICALSPEED*80)*.01)). LOCK STEERING TO HEADING(270, pitch). //PRINT ship:VERTICALSPEED*50. PRINT throttle+" "+ pitch. //LOCK STEERING TO HEADING(90, 0). //PRINT SHIP:ALTITUDE. // pid:update() is given the input time and input and returns the output. gforce is the input. if terminal:input:haschar { break. } WAIT 0.1. } SAS ON. UNLOCK STEERING. UNLOCK THROTTLE. SET SHIP:CONTROL:PILOTMAINTHROTTLE TO 0.

My best yet: 28:45. 43 tons starting mass. I went retrograde, used 2 nuclear engines and 4 rapier engines which I used for orbital insertion and brief boosts at takeoff, and I found rapiers to be the best for this purpose. Instead of a nose cone at the front I used a fairing which has higher heat resistance for this critical part. Mainly it was a combination of a good ascent and descent, and going retrograde which lessens lift needed to keep below 35k, allowing significantly higher speeds for the same thrust. I only recorded a video, which does have an edit for an autosave towards the end. Thanks, this was very helpful.

I gave it a test in reverse and got significant savings on fuel, approximately 40% less at cruising for the same surface speed (@ around 2560 m/s surface, circular orbit ~33km). I was able to test this precisely with my kos script. It does take stronger engines to get into orbit, since you need to go faster to start feeling weightless, but the fuel consumption is so much less for the cruise, it enables options like using higher power rocket engines for the ascent. Question for more experienced players - do wings create any drag if they are headed straight in the prograde direction (any helpful threads would be appreciated)? Below would've been my best run (crash landed at 32:00, and this included doing a 180 turn after takeoff), except I blew up the nose cone on descent. It used an aerospike instead of nuclear because of better thrust, lower weight, and decent enough ISP. During cruising I was thrusting about 8 kN.. with the same craft going prograde orbit, it was about 14kn.

My best with actual landing: 34:19. I wrote a kOS script to maintain a near perfect flight for nuclear engine types, much better than Mechjeb was doing. It sets throttle based on an estimate of orbital energy, and has a quite stable altitude control. I only used half the fuel so it may need a redesign. More in this album https://imgur.com/a/LPmim7w and video of kOS altitude maintenance and landing. I went into a few intentional spins to slow down to land: Similar thoughts here, and air speed appears to be the ultimate limit, so to get beyond that, as you said, is fast takeoff and landing. Good job on 30 minutes. I can post the kOS script as well if you want.

For anyone wondering how to do nuclear engines for this and approach the 33 minute range, here's a video of an ascent and getting auto throttle control. The craft is kinda cheaty, with the nuclear engine inside the main fuel tank, and was very unstable when the fuel ran out. The mechjeb autopilot can work for speed, but takes some babysitting to manage altitude.

Nice! That is a nice optimization to put everything inline and put the nuke backwards. There is another potential time save, by going into retrograde orbit instead of prograde, so KSC gets closer to you while in flight instead of farther. It means going ~340m/s faster relative to the air, and a harder ascent, but by rough calculations it would reduce time by 3 minutes. It would use more fuel but that is hardly a concern since while in orbit, the only loss is drag and mass doesn't matter very much.

The heat was a problem, but mainly the craft was too heavy to keep the height up. With a small redesign, I was able to get into "orbit" with help from rocket mode from the rapier engines. This orbit was ~2166 m/s surface speed at ~34k, so to go any faster it would have to thrust downward to keep from going into space. At this point I could use very little thrust to maintain speed. Just based on kepler's laws, it should be a significant amount faster than kerbin orbit in space). I did manage an actual run in about 35 minutes, though I got my altitude too high at some points, I overshot the runway by a lot, then sorta landed at 38 minutes, but this was mainly a test. I got decent results by using aircraft autopilot, hold vertical speed at 0 and hold speed at 2166, and manually adjusting occasionally to keep under 35k altitude. It also said I had about 3 hr - 1 day worth of fuel at this thrust level, so it can clearly get away with a lot less fuel. The majority of the fuel usage was getting to to orbit in the first 5 minutes, exactly as logic would say - this is like launching and maintaining the orbit of a low satellite. You can see me overshoot here

Not an official run (no command seat), just experimented with using nuclear engines and RAPIER. 57 minutes roughly. I used the nuclear engine to jump out of thicker atmosphere repeatedly (up to 35k), thinking it would allow higher speeds. The nuclear also helped quicken the initial ascent, as well as some spare oxidizer. I'd turn off the nuclear when the RAPIERS turned back on, and flew it all manually. The nuclear is tilted downward slightly, the theory being the plane could point forward and the nuclear would keep it up, but my assumption is probably wrong there. More pics: https://imgur.com/a/ODKV0IH Great job everyone else.

I did this at level 4, trying to be smart about it, using rhino engines for the majority of the burns (better ISP than vectors), and with ISRU on Gilly and on Eve. Used a powered descent to Eve, and using default game settings. For the initial launch from Kerbin, I took advantage of all the Vector engines needed for the eventual Eve ascent and could put some enormous tanks on. I took 3 kerbals, the big ore converter and 2 drills. I also took a module to allow a surface sample, though that didn't work out. Didn't do any docking so that meant taking more mass on the whole trip. I initially designed it around taking 3 kerbals. Should be 1700 points: Level 4: +1250, Mass 1361 tons: +100, Funds 815k: +100, Mission completed in 500+ days: +25, ISRU used: +225 First screenshot is the actual Eve landing stage with the Rhino engines activated. Not all the screenshots are from the actual run. The actual launch vehicle. Launch screenshots from a previous vehicle but pretty close to the one I used. It's asparagus staging with the huge tanks transferring to the main vehicle. Refuel at gilly with actual vehicle and had barely enough delta V to land and refuel for insertion and descent to Eve. Descending to Eve and transferring fuel to lower center of mass The Rhino engines had burnt of in descent but that was a good thing since I didn't need them anyway. The parachutes got me to about 8m/s and it was an easy landing. THIS DID NOT WORK. I wanted to use this thing to land on Eve for a surface sample, then shoot straight up, go EVA and parachute back to the main vehicle. Unfortunately I did not balance it well enough and I ended up shooting it off (without a kerbal of course). Eve liftoff after discarding ISRU equipment (can see one part to the left). Center stage has 7 vector engines, outer stages have 2 vector engines per side. Still going vertical on the central stage with 7 vector engines, and trying to balance the losses from air friction and gravity. Rhino stage for much better ISP in upper altitudes. Final stage is a NERVA engine that would finish the ascent from Eve take this home to Kerbin. Actually had a ton of delta V to spare. Landing at kerbin after intentionally burning up all the liquid fuel to lighten it. Might do it again and design it more for lightness and more delta V.

Found an old screenshot from 2014 in version .23, think it was meant to drop the orange fuel tanks on things.

After about 150 more attempts and lots of craft redesign, I got down to about 1:00.7 (judging from the first frame I got in the desired orbit). This was pretty hard to get. I used 4 "boosters" in onion staging, each consisting of 2 mammoth engines and 2 kerbodyne s3-7200 fuel tanks (plus 1 nose cone, 1 strut, 1 fuel line, and 1 decoupler), to accelerate off the ground really fast but still have a good amount of fuel. I used a more vertical launch profile, and also cut the engines for a few seconds while approaching the point to start thrusting sideways/downwards to get into orbit, because using delta V vertically in this region has minimal benefit on total time. The craft only had 56.7 seconds of thrust time, so it was critical to use it well and I just barely did it, with many failed attempts. In a basic theory, the best launch profile of this challenge is go almost straight up to get out of the dense atmosphere quickly, then at a certain point thrust down/forward at a ~45 degree angle, so that the following 4 parameters reach their needed value simultaneously: the vertical speed reaches zero, the horizontal speed reaches a bit above orbital velocity, the current altitude reaches > 70km, and the craft runs out of fuel. I used something close to this profile. This is stock version 1.7.3. Also I wonder if additional categories are needed. What I did here is going to be hard to beat. Perhaps categories <20 parts or <80 parts, or under a certain mass would be good.