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WildDoktor

1.6 vanilla career: getting to orbit

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Hey all; I'm back after a long time. Last time I was here I had loaded 1.3.1 and Real this / Real that (can't even remember now!), worked through many many install issues, got it all running, then life happened.

Now, I'm kind of back to square one, and not sure yet that life won't "happen" again, so I decided to just update to vanilla 1.6 and start a career mode from scratch...and just have a little fun rather than stress.

Actually, I'm not entirely sure if this install is really "vanilla"; I somehow have mechjeb 2.6.1 and kerbal engineer redux 1.1.3.0 installed and running...though they both say they're not compatible with 1.6 on the load screen. Yet they seem to work fine in game with the right parts installed on the craft. :/

So, my question is: What's the "best" (most automated) way to get to orbit these days?

This is the "guide" that I either wrote to myself or found somewhere around here a long time ago, and have been using the last few days. It's very manual and tedious:

  • By 100m/s: pitch to 85 (95 if you need to orbit the other way 'round)
  • By 10k: be pitched to 75 (105)
  • 20k: 65 (115)
  • 30k: 55 (125)
  • 40k: 45 (135)
  • 50k: 40 (145)
  • By this time AP should be 70k or higher. Cut engine, coast to within 25 seconds of AP (more or less depending on engine efficiency)
  • Pitch prograde
  • Throttle up to circularize orbit

If I use MJ Smart A.S. and the above guide, I go to the launchpad, open Smart A.S., click SURF, then SURF; I launch the rocket, and at 50m/s I click the minus sign for PIT once...putting my pitch at 89. At 60m/s, click down once. 88. Rinse, repeat. So by 100m/s I'm at 85. Then every 1000m (altitude), I click the minus sign once, and do that until I get to 50k (altitude).

I know later in the career I can unlock the ascent autopilot thingy in MJ, but I'm not there yet.

So. Is this a viable way to get to orbit? Is there (hopefully) an "easier" way? A way with less clicking, and more enjoying the scenery? The novelty of launch to orbit is already wearing off; in real life they don't manually fly to orbit...I'd rather have it automated, too. :-)

Any help is appreciated. Thanks!

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I thought there was a button in MJ that said "get me into orbit"?

In any case, after you've done the "pitch to 85" step, the easiest next thing to do is turn on your SAS, click prograde, then click to map mode and watch your Ap rise to 70km. But maybe you have to stage, too.

But your numbers are wrong for the current version. You want to be at 45 degrees by 8km to 10km. WAY below 40km.

 

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Posted (edited)
4 hours ago, WildDoktor said:
  • By 100m/s: pitch to 85 (95 if you need to orbit the other way 'round)
  • By 10k: be pitched to 75 (105)
  • 20k: 65 (115)
  • 30k: 55 (125)
  • 40k: 45 (135)
  • 50k: 40 (145)
  • By this time AP should be 70k or higher. Cut engine, coast to within 25 seconds of AP (more or less depending on engine efficiency)
  • Pitch prograde
  • Throttle up to circularize orbit

I much prefer:

  • TWR somewhere around 1.2-1.5
  • At 50m/s: pitch to 85, ignore your altitude and watch your Apoapsis.
  • From 2km-20km, slowly go to 40 degrees. You want to be heading East at 40 degrees when your Ap hits 20km.
  • Ap 30km, 30 degrees.
  • Ap 40km, 20 degrees.
  • Ap 50km, 10 degrees.
  • Ap 60km+, 0 degrees.
  • Ap at target altitude, cut throttle, coast, circularize, etc.
  • At some point, assuming you have the TWR, your time to Ap will rise past 1 minute. When it does that, I throttle back to 2/3. If it goes up to 90 seconds, I throttle back to 1/3. I'm still not convinced this is super necessary but it mimics a bit what the Mod GravityTurn does.
Edited by 5thHorseman
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Posted (edited)
6 hours ago, WildDoktor said:

If I use MJ Smart A.S. and the above guide, I go to the launchpad, open Smart A.S., click SURF, then SURF; I launch the rocket, and at 50m/s I click the minus sign for PIT once...putting my pitch at 89. At 60m/s, click down once. 88. Rinse, repeat. So by 100m/s I'm at 85.

That's a good start, IMO. I've been doing it like this for a long time now, haven't touched the launch autopilot in years.

A simple recipe:

  1. I do the clicky-clicky thing so that I reach 70° when I'm going 200m/s
  2. then hit the "SVEL +" button to follow prograde.
  3. keep an eye on "time to apoapsis", try to hold it between 30 and 60 seconds
    • if TTA becomes too low, use the +1 clicky to pitch up
    • if TTA gets too large, throttle down
  4. when apoapsis reaches the desired altitude, shut down the engines and coast to apoapsis.

Some notes:
For initiating the turn, "pitch@airspeed" is a much more useful metric than "pitch@altitude". It compensates for TWR to some degree and 70°@200m/s works well for many rockets.

In SVEL+ mode, the clicky acts relative to surface prograde. So if you enter +2 for pitch, you will keep your nose 2 degrees above prograde. I find that's an incredibly convenient way to steer a rocket.

It's not strictly necessary that time-to-apoapsis is always increasing. On many of my rockets it drops slowly at first, then picks up again later. How fast and how far it can drop before user intervention is required is a matter of experience. But ideally you should be able to just follow prograde until you're well above 25km. Otherwise, start with a steeper or shallower turn.

Flying by time-to-apoapsis is another measure that compensates for TWR; keeping it between 30 and 60 seconds will give a steeper or shallower trajectory as required for your rocket. You may eventually start to use different numbers, but this is supposed to be a simple recipe, and those two should give acceptable results with most rockets.

Edited by Laie
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To make a SSTO:

1. Place a Mk1 Command pod and get rid of the monopropellant

2. Place a Mk16 parachute on top of it

3. Place a Sviwel engine at the bottom

4. Stack FL-T400 tanks between the engine and the pod until TWR becomes ~=>1

5. Place a FL-T200 tank between fuel tanks and the engine

6. Rotate the craft 90* to the right

7. Launch

8. It should go to orbit

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Thanks all! I'm currently trying all these options with the stock AeroEquus model that I've attached KER and MJ2 modules to. As I'm only at the "45 science points" tier of the tech tree, I still only have basic functionallity from those mods. That's fine, it's fun to start simple!

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Posted (edited)

Just adding one more option to the excellent suggestions above. here's how I do it:

  1. Build your booster TWR between 1.2 and 1.5 and you're second stage around a TWR of 1
  2. Set SAS to hold and launch straight up to around 90-100 m/s - This will vary depending on your launch TWR, but it's easy to tweak
  3. Tip your nose Eastward to 80 degrees  - your prograde marker will start to tilt in the same direction
  4. Wait for your Prograde marker to hit 80 degrees then switch SAS to Prograde - now your nose will follow prograde and your rocket will start slowly tipping as it goes through a gravity turn
  5. You want your altitude to be between 8km and 12km when you're angled 45 degrees to the horizon. - If you want to fine tune this you can restart the launch and change the speed at which you do your initial tip-over. The higher your initial TWR the sooner you want to perform tip-over. 
    1. Pro Tip: note your altitude at 60 degrees, this will be pretty close to half the altitude you'll hit when you get to 45 degrees, so you can tell early if you're on the right path or not.
  6. Stage as necessary and keep accelerating until you've reached your target AP then cut engines and coast.
    1. Depending on how deep in the atmosphere you are you may want to overshoot your AP by a 1km or 2 because the atmospheric drag will slow you down a little.
  7. When you're approaching your AP, plot a maneuver using the maneuver node to circularize your orbit
  8. Burn according to the maneuver you plotted.
  9. You're in orbit!!!

As a final note, there are many variants for these launch parameters used my many skilled players. I've been doing a bunch of testing - higher vs lower TWR, earlier vs later initial tip-over, throttling vs letting engines run full out, etc. The changes I've tried definitely can affect the final DV expenditure, but I've found that most of these variants fall into a range of plus or minus 100 DV. When you consider that your total launch DV is around 3000(ish) that's only a 3.3% variance in total DV. Considering NASA had a 1-1.5% variance on their real-life "lives are on the line" accuracy for Saturn V you're doing pretty well - so, have fun optimizing, but don't sweat it too much  :) 

 

Edited by Tyko

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Thanks again everybody! I'm particularly beginning to like the "tilt to 80 degrees then SAS to prograde", but it took me working through the other options to become comfortable with this.

I'm lothe to leave space junk, especially in early career, so I'm now beginning to learn to optimize my stages so that I drop the stage that gets me close to circular (so it falls to Kerbin), then use the next stage to burn to orbit and to Mun. Then I drop that stage so it hits the Mun, and use the "lander" stage to land on the Mun and return to Kerbin.

It's a work in progress. :-) I just can't seem to get enough DV in that last stage to take a ton of science *and* return to Kerbin. I'm soooo close, though; within about 150dv. So I've been playing with all the things @Tyko mentioned: higher vs lower TWR, earlier vs later initial tip-over, throttling vs letting engines run full out, etc.

I'll get there! Oh...and back. Can't forget that part. :-)

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