LN400

That... is... awesome! Does it fly well?

Apologies to TheGuyNamedAlan Anyway, I know I have gotten a few ideas out of this topic and hope TheGuyNamedAlan has too. Now how to source the time to get to those ideas.

This is a surprise to me. I rarely use 2.5 and above. Great find! The curious me wonder if there is a great difference in the thrust (or Isp or mass)/cross section ratio, generally speaking, between the two sizes. Time for me to fire up KSP and punch in some numbers. EDIT. Looking at the data for the T30 compared to the T45 mass thrust (atm/vac) Isp (atm/vac) TWR (atm/vac) T30 1.25 200.667/215 280/300 160.5/172 T45 1.5 168.75/200 270/320 112.5/133.3 I wonder if there is any gain in having less fuel in the first stage of my rocket (T30) to reach between 10000 and 15000 instead of 20000-35000, and more fuel in the second stage with a "vaccuum engine" seeing the Isp and thrust get pretty high towards max at around 15km. The way I figure, what I want is velocity and that comes down to TWR and burn time vs drag and gravity. Burn time is a function of thrust setting and Isp. Given identical tanks (stock 4.5t) and capping the T30 thrust to the closest I can get to the T45 (vaccuum values), the burn time for T30 58.9s for 199.95kN, Isp 300 TWR 3.54/11.65 T45 1m 2.8s for 200 kN, Isp 320 TWR 3.40/10.19 The question then is at what point does the longer burn time of one engine with a lower TWR give a higher velocity than a higher TWR, shorter burn time engine or rather where would the 2 graphs meet. This is going to be a long study.

A mountain, huh? You were lucky! We lived in a giant hole and every morning our dad sent us out to collect pebbles to fill the hole and build a mountain on top of it, then he had us tear down the mountain using nothing but stone tools we had to chip ourselves. When we were done, we had 5 minutes left of the day where we kicked this anti-ship mine! Try to tell the kids of today this....

Nice job indeed!

Ok, that thing is.... sizeable. How did it survive the reentry? And how did it slow down in time? Drogue chutes en masse?

I hear you, loud and clear EDIT: Set initial TWR to 1.50 atm (from 1.61), and adjusted the script to rotate 1* (set rot to -1, old value -2.75) and got remaining dv 425 m/s which is a jump up from the previous 375-ish from the previous script. Drag seems to be a factor to consider. One launch only but the jump was noticable.

Sorry, just saw this. As I understand it, having a bit of drag near the bottom together with a streamlined nose helps keeping the rocket on track. I removed the fins for a modified version of the rocket and will see how it behaves, same settings as before but 40kg lighter and no drag at the rear. EDIT: I can confirm that without the fins, the design is a nightmare to control. Fins going back on for 40kg.

That's affirmative. So, low speed? Hm I need to have a good look at this. Would very much be interested in any findings of yours. EDIT: In case you use kOS and want the same script as I use set rot to -2.75. set rot_vel to 15. set rot_vel_end to 35. set run_prg to true. declare steer to up + r(0,0,180). lock steering to steer. SAS OFF. when airspeed > rot_vel then { set steer to up + r(0,rot,180). when airspeed > rot_vel_end then { unlock steering. set run_prg to false. } } wait until run_prg = false. wait until altitude > 20000. SAS ON. I let it run and only tap the keys to keep the nose on target. It says speed for initial rotation is 15 but it takes a second or two before things happen so it reaches 20 before it tilts over.

Sorry, I should have mentioned. Speed gets real high at around 10000m (past 300 m/s) and around 500 at 14000. That's when it gets real crucial to be on the prograde but again, just the tiniest, quickest taps on the steering keys and it's sorted. The kOS script also auto engage SAS at 20,000m just before decoupling the lifter and from there on out steering is no issue at all. Temperature is though, KER showing close to 87-90% to critical temp at around 25000m and up to around 45000-50000. I tested 3.5 degrees but at 20m/s and only around 1.63 TWR, the rocket is about 10* above horizon at 20,000 m and first stage doesn't last more than up to around 18000.

Initial TWR at the moment is 1.61(3.55) atm, 1.73(3.80) vac. As for control authority, it is surprisingly easy to control as long as you don't allow the nose to wander off the prograde marker more than 1-2 degrees. I assume the aerodynamics and the reaction wheel together get the job done. Nose wander off more than 2 degrees and it gets hairy, 3 degrees and you're done for but keeping it on target is really no issue. I chose the T30 for the lower mass/greater thrust and since it's this easy to keep straight, I am reluctant to replace the engine on this particular design for one heavier with less thrust. I wonder, why ditch the fins? Drag or mass? As for the upper stage and increasing the capacity: You mean do that and reduce the capacity of the first tank? Reason I look at fuel and dv is I have a curious mind I am looking for a way to script the launch for kOS but I want to have a more thorough picture of what is going on. Even if it turns out to be less important I still would like to know. Beside, if I can get away with less fuel, then that means smaller tank and less mass which in turn can be traded for either more dv or a cheaper design. At least that's what I figure. EDIT: I must also mention that the initlai rotation happens at so low speed (20 m/s) the reaction wheel has no problem holding it there for the few seconds it needs to stabilise.

I like the style in that pic! It really stands out.

from top to bottom: Mk 16 parachute M-315 Probe Core (mod: kOS) Kerbal Engineering System (mod: KER, flat and centered on the nose of the pod) Mk I Pod (no monopropellant) + 2x OX-STAT solar panels in symmetry. TR-18A Decoupler Procedural Liquid Tank (mod: procedural parts, 1.25m x 0.75 m) 0.625m "Sparkler" engine (mod: Modular Rocket System) Interstage Fairing Adapter (mod: procedural fairings, 2 nodes) + fuselage fairing SA-4 Fuel Tank (mod: KW Rocketry) 4x Basic Fin LV-T30 Engine

Cool. Tell us how it worked out. I'm sure more people would like to know.

Thanks and yeah, MS Paint can get you some cool pics. Some seriously gifted artists on youtube if you want to have a look at those. EDIT. Looking through these old pics, I found a couple more I thought came out alright. The eavesdropper "Really? My! You don't say..." The Show Must Go On

Do you have the original craft file? If so, you can try copying all entries in the ACTIONS { } section of each part you want to fix over to a copy of the new craft file. DISCLAIMER: I do not know if any of the commands there have been changed.

One issue I can't seem to sort out is that with max thrust at close to 4, the apo is several minutes ahead at altitudes as low as 25000m whether the prograde is at 45* or 15* above horizon. More testing needed here indeed.

I have been following that, and reading the links posted there for a couple of days now and it does indeed appear to be correct, albeit a bit counter intuitive that a shallower trajectory going "too fast" will actually save dv. Last test I did was, using kOS to handle the rotation, leaving the throttle at full, starting TWR 1.65, end twr over 3.75changed from 3+ rotation angle 3.5 degrees starting when the surface speed reached 20 m/s and held until the speed reached 45 m/s where the steering unlocked and aerodynamics took over. Remaining dv in orbit was 415 m/s. Now that doesn't mean much in itself but the previous test with locked twr and steeper climb had me in orbit with 195-205 remaining dv. I am still going to see if there is a way to get more savings by limiting the thrust somewhat. The engines were kicking but the acceleration didn't match in the lower atmosphere (up to around 25000 m). After that, the acceleration went nuts and I ended up with an apo too high 8 minutes ahead and still I ended up with more than twice the amount of dv remaining.

Some pics I made in MS Paint ages ago. Paying homage to classic horror movies Random stuff

What about losses due to traveling through dense atmosphere for a longer distance? I am curious about the sweet spot between that distance and speed to clear that area asap.

I take it that would be surface speed, correct?

Saturn V, hands down. The history, the background, the series of quantum leaps in tecnology just to get that thing going where it should go, the missions, the successes. A sure winner. ...followed by Delta 4 Heavy. That thing speaks business. "Aaarrr, I will get this payload into g**dd***ed space if it's the last thing I do". Respect.

I am experimenting with various trajectories on different rocket designs, trying to find the1 launch trajectory that will save me the most in fuel. I let kOS handle the throttle for a consistent TWR during the first part as well as the initial rotation for the g-turn. Target orbit is due east inclination 0 +/- 0.01*, apo between 71000m and 72000m, peri no more than 500 m below apo. So far, the best result for a selection of single engine 2 stage designs have been: TWR from launch until 30000m: 1.50 Rotation angle: 3* Altitude when g-turn hits 45* above horizon: 30000m Time to apo during ascent: 45-50s (not enough tests to narrow it down) reached no later than 24000m, no sooner than 20000m Altitude for attitude 0* above horizon: 60,000m-61.000m Time to apo before the final circularisation burn: No more than 2 minutes, no less than 1 minute. Now: Any suggestions on how to improve the trajectory? What are you looking for in a good launch trajectory? 1 if such a thing exists.

What WILL I do today? Relearn kOS and get this script flying. They told me coding is just like riding a bicycle. They don't know what a bicycle is.

Slooowly getting back into kOS and 1, I have forgotten most, and 2, there are some changes so my old scripts won't work. That's not an issue as I plan on fixing that BUT: I am attempting to code a very simple throttle control for launch and the first 20-30 km. The idea is to use throttle (locked variable), weight (locking the variable to mass * 9.81 which apparently works) and current thrust which for the life of me I can't get. Reading the documentation but with all the changes this is going to take a while so: Can someone please give me the snippet of code to gain access to current thrust to pass on to the variable? EDIT: I came up with this list engines in eng. set twr_set to 1.5. set g to 9.81. set thr to 1. lock weight to ship:mass*9.81. lock thrust to eng[1]:thrust. lock twr to thrust/weight. lock throttle to thr. until altitude > 30000 { if twr < twr_set and twr < 1 { set thr to thr+0.001. } if twr > twr_set and twr > 0 { set thr to thr-0.001. } } The problem here is the hardcoding of using engine 1 (a 2 stage rocket with engine 1 for the lifter stage and engine 0 for the ascending/injection stage). Is there a way to have the code look at whatever is the current engine, in a clever way that doesn't involve too much extra code as I intend to extend the code and need to keep it somewhat short.