Rodhern

Launch "Kerbal 1-5" to LKO

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Save fuel by flying a stock gravity turn to orbit

This is a competition in KSP version 1.2.1 to launch the stock "Kerbal 1-5" from the KSC launch pad to low Kerbin orbit, with as much fuel left over as possible.

 

Motivation for challenge

My interest for this topic recently rearose when this question was asked and discussed.

I haven't played much recently, but I remember how difficult I found it to estimate the fuel needed to get to orbit back in KSP ver. 1.0.4. According to the guides and forum posts you are supposed to fly a gravity turn to save as much fuel as possible. Most of the posts I found however aren't necessarily entirely up to date to the newest KSP versions. We will soon get KSP ver. 1.2, and then while the modders are busy updating mods I thought I would get someone to answer the above question, by kerbally kunningly masking it as a 'challenge'.

In short, I am curious how much fuel I should expect to have left once the Kerbal 1-5 reaches LKO.

At first I had less than 30 units of liquid fuel left (the near vertical approach). Now I am up to a shade over 40 units. It can probably be improved substantially still.

I will soon add detailed rules (none of the easy tricks, like adjusting the thrust limiter, are allowed), and explain the scoring (a slight variation on the number of unused liquid fuel units).

 

Vanilla rules

The idea is to find out just how much fuel the stock "Kerbal 1-5" rocket model has left, when flown to low Kerbin orbit as suggested by the design. When I say suggested by the design, I mean that the strange extra docking port should stay on, and the thrust limiters should stay in place too.

  • Attempts should be flown in KSP version 1.2.1 1.2 without any physics changing mods.
  • Difficulty settings that may affect the flight must be at the default values; i.e. re-entry heating must be at 100 %, and changes in the debug menus are not allowed.
  • The launch takes place from the KSC launch pad. Any time of day is acceptable as the launch time. The vessel is the stock "Kerbal 1-5" manned by one kerbal.
  • Changes to staging is not allowed; neither is manually staging/ejecting/activating the staged parts.
  • You may not tweak the stock vessel in any way; in particular you must leave the thrust limiters in place.
  • An exception to the above rule is that you are allowed to lock and unlock the engine gimbals (and/or change the gimbal limits). You are also allowed to change, disable and enable the reaction wheel mode to suit your flying style.
  • You are not allowed to use the RCS; all of the monopropellant must be spared. Neither are you allowed to go on EVA or bump into other crafts.
  • The target orbit is an eastbound equatorial orbit of Kerbin at 80 km ASL. Your orbit is, however, allowed to be any orbit of Kerbin with periapsis and apoapsis both at or above 80'000 m.
  • You may manipulate the throttle as you wish, and you may take any path to space/orbit that you think best, as long as you don't leave the Kerbin SoI.
  • You are allowed to take advantage of SAS, autopilot mods and custom instruments (e.g. time to apoapsis and inclination read outs).

 

Challenge participation reports and scoring

When submitting results please report all of the following.

  • The challenge entry category.
    • "Vanilla": The main/nominal category. The one described in this section.
    • "FAR": Using the FAR (aerodynamics) mod. See below.
    • "GOaP": The "Get Out and Push" category. See below.
  • Any control automation used.
    • "AP": If you utilized an autopilot of sorts. Please tell us about the settings you chose, particular if you manage to find a particular efficient gravity turn strategy.
    • "SAS": If you did not use an autopilot, but did engage the stock SAS.
    • "Manual": If you flew the entire mission by hand (and without SAS).
  • The number of liquid fuel units left on board, once in orbit.
  • The periapsis and apoapsis of your orbit.
  • Visible heating during flight. I don't think the stock Kerbal 1-5 is prone to heat issues, but maybe visible heat effects are a byproduct of an optimal gravity turn. Please let us know if you notice heat effects, and try to describe their 'severity'.
  • Anything out of the ordinary. Are you for instance launching at a particular time of day to take advantage of the hot (and less dense) atmosphere.

Your score is based on the amount of liquid fuel left (in your FL-T400 fuel tank) when your orbit is established.

In the nominal category ("Vanilla"), the score is adjusted slightly for your actual achieved periapsis and apoapsis, and given as a percentage. A percentage score is the more action packed option for a competition! The score formula is presented in a thread of its own, so that it may be discussed separately.

The score formula for the stock configured Kerbal 1-5 will give you a score of roughly 15 % if you have 15 units of liquid fuel left (poor efficiency), and roughly 70 % if you have 70 units left (outstanding efficiency). The scale is not linear. Getting into (80 km) orbit with no fuel left is enough to score above 3 %, and a shade over 90 units are required to get a perfect, and probably impossible, score of 100 %. [Note: the score formula may yet be adjusted to accommodate changes introduced in KSP ver. 1.2; the score formula is updated for KSP ver. 1.2.1].

The corrections for actual periapsis and apoapsis is given for periapsis above 80 km and below 100 km and apoapsis above 80 km and below 120 km. The idea is that if your gravity turn happens to have a build-in overshoot, then you will not have wasted all of that overshoot energy (i.e. fuel) in regards to your score. All else being equal you will loose some points though, compared to a tighter cheaper alternative. The corrections are made because the challenge should not primarily be about who can hit 80 km with the greatest precision.

Entries in the "FAR" and "GOaP" categories are not adjusted for periapsis or apoapsis. The unadjusted scores ("FAR" and "GOaP") are exactly the number of liquid fuel units left in orbit. The percentage score formula is used only for entries in the nominal ("Vanilla") category.

 

FAR ladder rules

Spoiler

 

Ok, this one is going to be easy. The FAR ladder rules are the same as the vanilla rules with the following exceptions.

  • Any KSP version will do. Please report the KSP version number in your entry.
  • The FAR mod is allowed. Please report the FAR version number in your entry.
  • Default FAR parameters should be used (so that we can compare entries on a fair basis).
  • Your score is the number of liquid fuel units remaining once the (80 km) orbit is established.

 

 

GOaP intro

There are already a few good (and surprisingly sane) entries in the "Get Out and Push" (GOaP) category, so let us write some 'formal' rules for the GOaP challenge part.

A group of dry and boring optimizer consultants have visited the Kerbal Space Center recently. Their report suggests to reduce the number of Rapid Unplanned Disassembly events and to layoff Kerbals. After reading the report Max L. Kerman quickly drew up calculations showing that the savings necessary to solve the current funding crisis can be achieved by a combination of flying more efficient gravity turns and a bit of creative tinkering.

It is now up to you to show that the Sunday launches of the Kerbal 1-5 are not just leisure trips to orbit, but in fact important "In Orbit Fuel Contingency Reserve" missions. You do that by displaying that the Kerbal 1-5 has a viable amount of fuel, that it may function as an orbital refueler, i.e. have as much fuel as possible left over once in orbit.

Not all of the tinkering is quite aboveboard, so there are restrictions as to which actions you may perform below 1000 m above sea level.


GOaP rules

Spoiler

 

  • No (physics) performance enhancing drugs mods (but visuals, read outs, auto pilots et cetera are ok). Also, no tweaking of re-entry heating, and similar (physics) settings. Entries from KSP versions 1.1.3, 1.2 and 1.2.1 are welcome.
  • The launch takes place from the launch pad. You may change the staging sequence of the Kerbal 1-5 while on the pad, but you may not discard anything at this stage (not even the extra docking port).
  • You may not 'right-click change' anything on the launch pad, except for the gimbal locks of the engines (you are allowed to lock the gimbals if you want), and your are allowed to toggle the reaction wheel to what ever mode you prefer.
  • The goal is to reach a 80 km orbit of Kerbin. Any orbit of Kerbin with periapsis and apoapsis at or above 80'000 m is acceptable.
  • Once at or above 1'000 m above sea level you may mess around with the thrust limiters, the parachute, you may ditch the extra docking port, go on EVAs, engage the RCS system and basically almost anything your creativity lets you think of. Please tell us what fantastic tricks you come up with.
  • In the GOaP category your score is the number of liquid fuel units remaining when the desired orbit is reached.

 


Leader board (vanilla template)

  1. Eidahlil; 39.22 %; KSP 1.2
  2. Gordon Fecyk; 37.66 %; KSP 1.2.1 (video included)
  3. tg626; 33.37 %; KSP 1.2 (a touch below 80 km)
  4. emaier138; 31.32 %; KSP 1.2
  5. tseitsei89; 41.37 %; KSP 1.1.3 (score suspended)
  6. mk1980; 41.29 %; KSP 1.1.3 (score suspended)
  7. "Name"; "Efficienty score"; Comment

 

Leader board (FAR and GOaP)

Spoiler

(sorted by entry date)

  1. Signo; 49u; almost vanilla.
  2. GoSlash27; 53u; there is a picture there, so let's call it an entry.
  3. Reactordrone; 73u; the effects of better TWR.
  4. Rodhern; 53u; flown in FAR.
  5. surge; 52u; doing the kOS fiddly-thing.
  6. JAFO; 40u; scientific vanilla (score 36.79 %).
  7. Gordon Fecyk; 68u; the effects of better TWR.

 

Edited by Rodhern
update for KSP ver. 1.2.1

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I am not sure this is the right craft to use as an example about that question because of its "peculiarities".

I took the craft as is, no parts were tweaked or moved. 

I saved 48.80 units on my first try and I am sure there is still edge because I realized the "peculiarities" a few seconds too late. 

hWNPVcL.png

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I just took a stab at it and got 34.39 fuel remaining on what I'd consider a "nominal" launch (prograde gravity turn).

onefive_zpsfbapowv4.jpg

 

Just out of curiosity, what's supposed to be "wrong" with this launcher?

Best,
-Slashy

Edited by GoSlash27

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To me nothing wrong - just that I figured out that we are still looking to settle down the old feud about gravity turn: I used mono to circularize (that is the "peculiarity", I may even be disqualified for this I think) and it is virtually impossible (at least to me) to do that without a gravity turn.

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10 minutes ago, Signo said:

To me nothing wrong - just that I figured out that we are still looking to settle down the old feud about gravity turn: I used mono to circularize (that is the "peculiarity", I may even be disqualified for this I think) and it is virtually impossible (at least to me) to do that without a gravity turn.

Gotcha.

 I played mine 100% straight (no RCS)  and gave it one try cold. My KSP locked up while composing the last reply, so I was forced to recover Jeb. It ran the whole mission without needing any adjustments, so I'm kinda puzzled as to why this is a stock craft. Normally stock craft have intentional flaws designed into them.

*edit* Yeah, I can see how you could substantially improve on this figure if you intentionally use the RCS instead of fuel for circ. I ran it again and hit 72x43 suborbital with 53 fuel left. The RCS could easily circ this.

 

Best,
-Slashy

Edited by GoSlash27

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17 minutes ago, GoSlash27 said:

Normally stock craft have intentional flaws designed into them.

You are right - this one is almost flawless. 

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In fact...

onefive2_zpsutg01igh.jpg

If you study the pic, I think you can puzzle out how I managed to achieve this. Didn't adjust anything, just ran my operations in a different order.

Seems cheaty to me, tho'... :/

*edit* I've decided to unilaterally disqualify this entry. If the goal is to figure out how much DV it takes to orbit, chucking entire assemblies overboard before launch and burning RCS just confuses the issue. I'll just go with my first submission.

-Slashy

Edited by GoSlash27

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Are you allowed to ditch the docking port? Also, if Val got out and pushed you could probably circularize with a hair lower PE, saving a unit or so of fuel. 

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4 minutes ago, MaxL_1023 said:

Are you allowed to ditch the docking port? Also, if Val got out and pushed you could probably circularize with a hair lower PE, saving a unit or so of fuel. 

I dunno, as the rules aren't clearly stated on the matter. I ditched my docking port on the pad on the second run. Didn't think about using the GOAP method.

Best,
-Slashy

33 minutes ago, Signo said:

You are right - this one is almost flawless. 

Oh, I bet I know what's wrong: 3 RCS quads instead of 4. That makes docking a real PITA.

Best,
-Slashy

Edited by GoSlash27

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Thank you for the great entries. It tells me that we need three leader boards. The nominal one for stock, without any fiddling with thrust limiters, reentry heat, RCS, staging, EVA and such, then a FAR one to see how much of a difference that makes (is FAR stable at the moment?). And we are so going to need the third one, the "Get Out and Push" (GOaP) leader board.

And particularly thank you to GoSlash27 for giving it a try cold. While the maximum performance is nice to know, it is certainly nice to have an idea what to reasonably expect from a cold try.

 

17 hours ago, MaxL_1023 said:

Are you allowed to ditch the docking port? Also, if Val got out and pushed you could probably circularize with a hair lower PE, saving a unit or so of fuel. 

No reason we can't start the GOaP already in ver. 1.1.3. So what should be the rules for GOaP? Still no fiddling with thrust limiters, but free staging, ejections, EVAs et cetera? With a target of 80 km orbit?

Edit: GOaP rules added to challenge post. (Some thrust limiter fiddling allowed.)

Edited by Rodhern
quoted MaxL_1023

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A few tries using the vehicle "as is" I was getting 30-40 units of liquid fuel left. After upping the thrust on the solid boosters and lowering the main engine thrust at take off I was able to get 73 units of fuel left using some of the RCS fuel for circularization. The game crashed to desktop while I was preparing the screenshots, but from memory I had the boosters tweaked up to 63.5% thrust and got the ship up to 2200m/s at 64km using the LV-909 before switching to RCS.

 

kerbal1-5_zpsuenoz03e.jpg

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This small dude can prolly go circum-munar with a free return if piloted carefully. 

I am really impressed by the craft. 

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11 hours ago, GoSlash27 said:

Oh, I bet I know what's wrong: 3 RCS quads instead of 4. That makes docking a real PITA.

Almost :wink: 

Cheers.

Edited by Signo
Sorry for the double post - I messed up with notifications.

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Theoretically you could get that ship to Eeloo orbit if you got out and pushed. You would need to use one of those spiral trajectories developed for ion drives, but it would work if you were patient enough. It has saved me a couple times when I was starting out and while I got into orbit, had no fuel to get back down!

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Let me kick the FAR challenge part off by entering my attempt.

  • Challenge category: "FAR". FAR ver 0.15.7.2 "Lanchester" in KSP ver. 1.1.3.
  • Control: "Manual" (no SAS).
  • Periapsis and apoapsis: 80'107 m / 80'315 m.
  • Heating: I did not notice any heat effects.
  • Notes: My intention was a gravity turn, but I ended up doing a lot of poor quality manual inputs to keep the nose pointed in a reasonable direction.
  • Fuel left (score): 53.04 u.

I have noticed in this and other threads that it is customary to post images :)

FAR_FuelLeft_1.jpg

FAR_PeriApo_1.jpg

So I guess it is reasonably obvious that it is easier to get to orbit through the FAR atmosphere, compared to flying through the stock atmosphere. I did not know that for sure until now.

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interesting challenge! here's my entry:

launched with full throttle, nudged rocket about 5° at 20 m/s, switched to "hold prograde". pretty much "hands off" from there except for the staging and cutting engines after AP was at 80km. probably went a bit too shallow. PE was already at +10km when AP reached 80km. don't know if that's ideal.

unchanged stock rocket, stock aero, no RCS use - 44.9 LF, 54.88 Oxi after circularization

EDIT: i reduced the gimbal of the swivel and terrier "on the fly". that's allowed by the rules if i read them correct (?)

Z5Z9O4k.jpg

Edited by mk1980

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19 hours ago, mk1980 said:

interesting challenge! here's my entry:

launched with full throttle, nudged rocket about 5° at 20 m/s, switched to "hold prograde". pretty much "hands off" from there except for the staging and cutting engines after AP was at 80km. probably went a bit too shallow. PE was already at +10km when AP reached 80km. don't know if that's ideal.

unchanged stock rocket, stock aero, no RCS use - 44.9 LF, 54.88 Oxi after circularization

EDIT: i reduced the gimbal of the swivel and terrier "on the fly". that's allowed by the rules if i read them correct (?)

Thank you for participating. Your score is 41.29 % (score method thread).

I have put a note next to your name that this entry is from before KSP ver. 1.2 is released. If aerodynamics and physics don't change from now to then, I guess it makes sense to keep 'old' entries - we will see then.

You are correct that you are allowed to change the gimbal limits as you wish (even in flight). I have added a short sentence to the rules to clarify that you may change gimbal limits.

 

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On Saturday, September 03, 2016 at 3:21 AM, GoSlash27 said:It ran the whole mission without needing any adjustments, so I'm kinda puzzled as to why this is a stock craft. Normally stock craft have intentional flaws designed into them.

How come? The Kerbal X has no flaws I can personally identify either.

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45.09 LF left :D Done in 1.1.3 version http://imgur.com/a/K8LFo

Small increase is still an increase :P

 

EDIT: all gimbals set to 0 on launch. Gimbals only cause steering losses and you can "steer" enough with the reaction wheel of the pod. The trick is to guess the correct amount of tilt in the beginning so that after you hit prograde you can just stage and see you reaching 45 degrees at ~11-12km. Then you know you are doing just fine :) The tilt needed is just a few degrees...

Edited by tseitsei89

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13 hours ago, tseitsei89 said:

45.09 LF left :D Done in 1.1.3 version http://imgur.com/a/K8LFo

Small increase is still an increase :P

 

EDIT: all gimbals set to 0 on launch. Gimbals only cause steering losses and you can "steer" enough with the reaction wheel of the pod. The trick is to guess the correct amount of tilt in the beginning so that after you hit prograde you can just stage and see you reaching 45 degrees at ~11-12km. Then you know you are doing just fine :) The tilt needed is just a few degrees...

Thank you. Your score is 41.37 % (assuming no physics changes in KSP v. 1.2).

Yup, a small increase is still an increase. The fact that it takes more and more effort to save a little extra fuel might indicate that we are getting close to the best performance we can expect from the (stock configured) Kerbal 1-5.

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18 hours ago, Rodhern said:

Thank you. Your score is 41.37 % (assuming no physics changes in KSP v. 1.2).

Yup, a small increase is still an increase. The fact that it takes more and more effort to save a little extra fuel might indicate that we are getting close to the best performance we can expect from the (stock configured) Kerbal 1-5.

I'm not sure what is this 1.2 version you are talking about? Maybe 1.1.2?

I'm using the newest version currently in the store and for me it says KSP 1.1.3. And yes, no physics are changed.

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On 9/12/2016 at 1:29 PM, tseitsei89 said:

I'm not sure what is this 1.2 version you are talking about? Maybe 1.1.2?

There have been a lot of talk of the soon upcoming KSP version 1.2 on these fora (e.g. update 1.2 has entered experimental testing). We anticipate that once KSP version 1.2 is released a lot of the mods that players use will need updates. Also, the links for gravity turn tutorials I have seen are all written for older versions of KSP. All in all, it seems like a good opportunity, that while the mod players sit around in stock KSP ver. 1.2 waiting for their favourite mods to be updated, we can use the time to get familiarised with optimal gravity turn strategies.

The caveat about physics changes is to say that I may decide to exclude results obtained in KSP version 1.1.3 from the leader board. Then on the other hand, I might not exclude the entries. Previous KSP updates have shown that it is not uncommon that little tweaks are made here and there. We have for instance seen changes to the Kerbin atmospheric properties, the rotation speed of Kerbin (which affects eastbound ascents to orbit) and the effectiveness of engines (indirectly reduced ISP).

Edit: It was just revealed in this thread that "the aerodynamic simulation model has been tweaked" in KSP version 1.2. I will therefore exclude vanilla entries flown prior to version 1.2; after all the vanilla rules in the original post do state that only KSP version 1.2.0 will do. The FAR and GOaP categories remain open to KSP ver. 1.1.3 entries.

Edited by Rodhern
News about KSP version 1.2.

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Slapping a kOS unit (weighing 0.03t) on the side and using my launch ascent guidance script gave 52.22LF, 68.83OX for a 80.556kmx79.591km orbit. (No pictures, since google screwed up their photo website, sorry). Orbital mass was 2.879t.

Boosters were set to 50%. Transition turn ended at 10km @ 45°. monopropellant used only for minor steering. I should have turned off the reaction wheels, but I forgot. Oh, and includes a 10° safety turn at launch.

It could probably do better if I could be bothered fiddling more, or better yet, figure out how to calculate things like optimal transition turn angles, launch TWR (the script used ~1.3 by throttling the sustainer engine), etc.

Feel free to disqualify for not being stock, but I'm hoping you figure out that stuff for me with the results of this challenge; sounds a bit like you know your maths :)

Edited by surge

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Hi surge.

One of the points of the nominal (vanilla) category is to learn more about the effects of varying trajectories to orbit, in particular the effect on the amount of fuel used. I prefer to avoid 'cluttering' the nominal category with anything but the most stringent attempts to genuinely display the optimal yet practically achievable path to orbit.

I think your entry fits well with the spirit of the Kerbal shenanigans of the GOaP ("Go Out and Push") category. I will list your entry as a GOaP entry. Now that you know you are in GOaP territory feel free to fiddle further and resubmit improved results.

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Well if we can adjust the boosters, then here's one I prepared earlier. 100% thrust on the boosters and don't start the core engine up until booster burn out. No mono used, 72.82 fuel left.

kerbal%201-5%20no%20mono_zpsjlmhjb0f.jpg

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