Norcalplanner

OK, I've run some more tests, and it looks at this point like only the 1.25 TWR runs were affected by an initial turning speed higher than what was previously done. After I run a few more I'll have some more data to post, although it might be tomorrow.

Sounds fun. Let me know when it's up and running and I'll make an entry.

Sounds reasonable, although you may still want to give some thought to payload weight classes. The way the physics and part pricing interacted with the scoring system tended to skew the results in favor of larger payloads, which began to have limited applicability to typical game play. Of course, opening it up to parts mods may end up making things more attractive for smaller payloads again, particularly with larger SRBs in some parts packs. One thing I would definitely do - prohibit Real Scale Boosters. The costs aren't well balanced, and the weights and thrusts are based on RL examples, and therefore blow stock (and other mods) out of the water. Unless you want to do a Real Scale Boosters leaderboard, which would be interesting, but far removed from anything else.

As part of my testing, I also did runs at what seems to be the most typical advice, which is "up to 50 m/s, then tilt east 5 or 10 degrees". I wanted to see what sort of results I would get with the three thrust levels on the test rocket. As a reminder, this rocket is not flying a true gravity turn. It's actively steering to remain locked on the prograde vector, first in a surface reference, then in an orbital reference. A rocket flying a true gravity turn, depending on aero forces to turn the uncontrolled rocket after the initial controlled tilt, is going to have different results, as will a rocket without SRBs. With those disclaimers out of the way, here are the results. Results of 5-10 degrees at 50 m/s TWR Turn Steering Aero Gravity Delta V Spent Delta V Left 1.25 5 deg @ 50 m/s -8.6 m/s -54.2 m/s -1,295.2 m/s 3,395.9 m/s 2,614 m/s 1.25 10 deg @ 50 m/s -5.4 m/s -106.5 m/s -1,062.4 m/s 3,212.1 m/s 2,794 m/s 1.41 5 deg @ 50 m/s -26.3 m/s -47.9 m/s -1,403.8 m/s 3,525.4 m/s 2,541 m/s 1.41 10 deg @ 50 m/s -7.1 m/s -55.4 m/s -1,199.5 m/s 3,302.1 m/s 2,762 m/s 1.57 5 deg @ 50 m/s -54.4 m/s -46.3 m/s -1,444.4 m/s 3,598.2 m/s 2,501 m/s 1.57 10 deg @ 50 m/s -16.9 m/s -51.2 m/s -1,289.8 m/s 3,404.4 m/s 2,668 m/s So the takeaway from these results is that if you're not performing a true gravity turn, where you need to get going a certain speed so that your fins can "bite" the air effectively, waiting until 50 m/s is going to increase your delta V expenditure to orbit. For an actively steered rocket, turning earlier in the ascent should be more effective, particularly at higher TWRs. Edit: So in looking at this chart, compared to the one in the original post, I now see that for a TWR of 1.25, 10 degrees @ 50 m/s (second line) is actually more efficient than what I thought was the best entry, which was 5 degrees @ 40 m/s. I'll need to re-run some tests and see how well larger turns do at slightly faster initial velocities, then update the results accordingly.

I've done that in the past, but I've found that it only works well for rockets up to a certain size. It also breaks immersion for me a little bit to see anything that doesn't look like a Little Joe or Black Brant sitting at an angle on the pad.

I just love how this challenge keeps going even though it was only supposed to be for 1.0. Just goes to show how special the Apollo program was. I'm on the fence about whether to do a new entry, since I'm in RSS these days.

We could certainly crank it up again for 1.1.3, but I don't think there have been any significant changes in part costs or capabilities which would lead to significantly different results. The only things that might be interesting (to me at least) would be to establish payload weight classes and/or create a modded division. My free time for KSP is more uneven these days, so I don't feel I can give such a challenge the attention it deserves. If you or someone else who's participated in the 1.0.5 challenge wants to resurrect it for 1.1.3, be my guest. I would only ask that the name be kept similar and that the OP contain a link to this thread.

Thanks. I think that you've hit the nail on the head - the main point with these tests (at least in my mind) is this: Once you've got a halfway decent rocket design that can make it to orbit, play around with the ascent profile to see if it can be flown more efficiently. The initial turn angle and speed can affect your ascent delta v expenditure by hundreds of m/s.

Here's some more info showing how much the ascent profile plays a part. Methodology was the same for each run, as mentioned in the OP. Comparative Ascent Profiles - Identical 1.57 TWR TWR Turn Steering Aero Gravity Delta V Spent Delta V Left 1.57 5 deg @ 10 m/s -3.6 m/s -60.4 m/s -1,057.3 m/s 3,160.2 m/s 2,935 m/s 1.57 6 deg @ 10 m/s -2.8 m/s -67.1 m/s -994.7 m/s 3,103.1 m/s 2,990 m/s 1.57 7 deg @ 10 m/s -2.5 m/s -77.1 m/s -941.2 m/s 3,059.1 m/s 3,033 m/s 1.57 8 deg @ 10 m/s -2.4 m/s -103.4 m/s -884.2 m/s 3,030.6 m/s 3,061 m/s 1.57 9 deg @ 10 m/s -2.4 m/s -263.1 m/s -866.9 m/s 3,161.9 m/s 2,932 m/s 1.57 10 deg @ 10 m/s DNF DNF DNF DNF DNF With this TWR, there was a definite crossover point between 8 degrees and 9 degrees. The latter ascent was so flat that the Ap reached 100 km while the rocket was going sideways at 27 km altitude. It stayed down in comparatively draggy atmosphere for several minutes, requiring occasional bursts of acceleration to raise the Ap back over 100 km. While not the most dramatic results, these clearly show that making a small change in the initial tip angle (8 degrees instead of 5 degrees) can save 130 m/s in getting the craft to orbit.

They're specific to this particular 2.5m rocket, with its particular aero and thrust profile. The takeaways are that a) higher TWRs are generally more efficient, even if mass is exactly the same, and b) you can frequently get higher performance out of a rocket by altering the ascent profile, typically by turning earlier and/or more aggressively. I'll post some more comparative data shortly where the only variable is the ascent profile.

Thanks, typo fixed. Talking about limiting vertical velocity, visible in the upper left info window in the screenshots. Really upset with imgur's recent changes...

New comparative ascent data for stock Kerbin is now up:

Here's some comparative data from the best runs at each thrust level. Comparative TWR Ascent Data TWR Turn Steering Aero Gravity Delta V Spent Delta V Left 1.25 5 deg @ 40 m/s -5.2 m/s -76.0 m/s -1,123.4 m/s 3,234.4 m/s 2,773 m/s 1.41 5 deg @ 20 m/s -3.1 m/s -101.2 m/s -961.9 m/s 3,102.6 m/s 2,957 m/s 1.57 8 deg @ 10 m/s -2.4 m/s -103.4 m/s -884.2 m/s 3,030.6 m/s 3,061 m/s Everything is fairly self-explanatory - initial SL TWR, initial eastward turn angle and speed, steering losses, aero losses, gravity losses, total delta V spent, and delta V remaining in the tank of the craft's upper stage.

The new thread with stock Kerbin results is now up, although imgur is being cantankerous again.

This is a continuation of my previous study on TWR, ascent profiles, and aero drag vs. gravity losses begun in a previous thread, A Degree Makes a Difference - or How I Learned to Stop Worrying About Drag and Concentrate on Gravity Losses. That previous post was performed in RSS, and while many found it interesting, it wasn't directly applicable to a stock game. To remedy this, I've flown a bunch of ascents on stock Kerbin, and tabulated the results. As before, I created a basic rocket, but this time used only two Kickbacks because of stock's lower delta V requirements. The Kickbacks were then thrust limited to 70%, 85%, and finally 100%. After an initial tip to the east, MechJeb's SmartASS function would hold the craft on a surface prograde vector. Once the navball switches to an orbital reference, SmartASS is told to hold orbital prograde until the Ap is over 100 km. MechJeb is then told to circularize at Ap. Here's a picture of the rocket, which is all stock: After conducting over 20 runs, I've created albums with the best runs at each thrust level, and pasted links to them below. Remember, the only difference in these runs is the thrust level and the ascent profile. The rocket itself is identical. Most of the previous tips still apply, so I'll put them here again with some tweaks applicable to stock: 1. Launch with an initial TWR of at least 1.4. Piloting gets more difficult when it's over 1.7. 2. Don't worry about drag - gravity losses are much larger and more important, unless you reach orbital velocity below 30 km.. 3. Ignore the flame effects. Pay attention to the temperature gauges. 4. At higher thrust levels, crank it to the east immediately after launching, but be precise about it. 5. Try to keep vertical velocity below 500 m/s. If it's over 700 m/s, you're going to have noticeably higher gravity losses. 6. Getting a rocket to orbit in stock for less than 3,200 m/s of delta V is very doable. Using less than 3,100 m/s is a harder but still achievable goal.

If you look at the tutorial linked in my sig, you'll see that I'm not a big fan of the Reliant due to its inability to gimbal. I also have a rule of thumb that LFO lifter engines should be run as long as possible, generally at least two minutes, to maximize return on the investment in the engine. So I guess I would recommend adding fuel to your bottom stage, at least until the initial pad TWR gets down to 1.5 or so. I'll be unavailable most of today, so it may be awhile before I post again.

25+ runs complete, including some with 1.25m rockets. Spent more time varying initial velocity for the gravity turn this time. Initial impressions: No big surprises with the 2.5m rocket. Very possible to get to orbit for less than 3,100 m/s with an initial TWR of 1.57. Not worth cranking it over more than 10 degrees under any reasonable scenario. 1.25m rockets are a whole other kettle of fish. Really difficult to get below 3,300 m/s to get to orbit with a serially-staged rocket. A bit easier using 0.625m SRBs from SpaceY, making a smaller version of the 2.5m rocket configuration. One thing that does appear to make a difference- you can save a bit of delta V by moving those two solar panels off of the capsule and on to the top fuel tank. Less likely to explode this way too. It's definitely going to be tomorrow before I put together an imgur album and tally the numbers.

I should have some new runs on stock Kerbin done later today or tomorrow with various TWRs and ascent profiles.

Fins should only come off if the Reliant is replaced with a Swivel. I can only imagine how the Reliant was without them...

I'll be sure to run some with a 1.25m rocket - all of my tests so far have been 2.5m, so that may be part of the discrepancy.

Those speeds actually seem low to me. I'm frequently at 700 m/s at 10 km. Just to confirm, you're running 1.1.3?

I'll have to play with this when I get home tonight. So if I'm hearing you right, things get unstable starting around 3 degrees off prograde. At what speed? Is it possible to crank the rocket over 5 or 6 degrees starting at 10 m/s without losing control, and then lock to prograde after it recovers from the turn? It will probably be a few hours before I can give this my full attention, but it's certainly interesting. And to answer your other questions, I'd remove the fins to save mass, drag, and cost. And I would increase fuel in the bottom stage for the Reliant, not the upper stage - sorry if that wasn't clear.

Interesting - very little control authority and a high TWR. Probably makes it challenging to pilot. What's the initial atmospheric TWR? Off the top of my head, my inclination would be to put in a Swivel instead of the Reliant, ditch the fins, and increase the first stage fuel tankage by 25 or 50 percent. And is there a reason you're focusing on fuel used? Many people are more concerned about total cost, payload mass fraction, or cost per ton to orbit.

What does your rocket look like? Could you describe it or post a picture?

I think that it's time to do some more testing in stock to get some non-RSS info on aero vs gravity losses. I'll put it in a new thread as soon as it's done, either later today or tomorrow.