Heavy SSTO Efficiency Challenge

[Mikki]

@icedown
 Your challenge, your rules. 
I am still refurbishing my "Double Jumbo", getting the fuelload lower is rather tricky... next time with proper landing...  

[Lothsahn]

Okay, so I've been trying to use my stock lifter SSTO (which I normally only use to get to LKO) to do this challenge.  I find it interesting that its design is very similar to TaxiService, but it needs massively more engines and fuel--and even with my best attempts runs out of fuel de-orbiting.

Granted, I'm not using nuclear engines, but I'm wondering if anyone has any tips on how to tune it--or why it's so much less efficient than TaxiService.  I'd rather not use Nukes, as I avoid Nuclear Engines and RTGs due to the massive nuclear protests on Kerbal... </roleplaying>  Is that the main reason for the difference?  Is avoiding nukes THAT big of a penalty?

Do I have too little lift? Too many parts?  Thoughts?  I'm pretty sure I could remove the Minmus VTOL thrusters and finish the challenge, but I'd really like my stock taxi to manage without modifications.

Craft File (Right click and Save As...)

 

 

[TaxiService]

6 hours ago, Lothsahn said:

Okay, so I've been trying to use my stock lifter SSTO (which I normally only use to get to LKO) to do this challenge.  I find it interesting that its design is very similar to TaxiService, but it needs massively more engines and fuel--and even with my best attempts runs out of fuel de-orbiting.

Granted, I'm not using nuclear engines, but I'm wondering if anyone has any tips on how to tune it--or why it's so much less efficient than TaxiService.  I'd rather not use Nukes, as I avoid Nuclear Engines and RTGs due to the massive nuclear protests on Kerbal... </roleplaying>  Is that the main reason for the difference?  Is avoiding nukes THAT big of a penalty?

Do I have too little lift? Too many parts?  Thoughts?  I'm pretty sure I could remove the Minmus VTOL thrusters and finish the challenge, but I'd really like my stock taxi to manage without modifications.

Craft File (Right click and Save As...)

 

 

I got good news for you. Your stock plane does not need any modification as I managed to fly yours to 300x300km orbit, lose the payload, deorbit and land it on KCS. Once I got out of the atmosphere, I turned off all the RAPIERS except for two RAPIERS to conserve the fuels. Though, I notice the four RAPIERS at the bottom of your plane are not linked to any set actions and I didn't use them throughout the flight.

 

 

I have to go now. I will come back in 8 hours to add more details if you request.

P.S. Your plane has overkill of thrust and I had to adjust my ascent profile to prevent wing tearoff at absurd speed (cutting back the throttle). 

Edited June 25, 2016 by TaxiService
More details

[Lothsahn]

5 hours ago, TaxiService said:

I got good news for you. Your stock plane does not need any modification as I managed to fly yours to 300x300km orbit, lose the payload, deorbit and land it on KCS. Once I got out of the atmosphere, I turned off all the RAPIERS except for two RAPIERS to conserve the fuels. Though, I notice the four RAPIERS at the bottom of your plane are not linked to any set actions and I didn't use them throughout the flight.

 

 

I have to go now. I will come back in 8 hours to add more details if you request.

P.S. Your plane has overkill of thrust and I had to adjust my ascent profile to prevent wing tearoff at absurd speed (cutting back the throttle). 

So I actually just completed the mission by replacing the ramp air intakes with nose cones.  It appears I also have more intakes than needed, which is just unnecessary drag, right?  I never have a problem with overthrust, and I do use the 4 engines below.  That specific version of the craft file had an issue where the 4 engines on the bottom both aren't linked to action groups and are incorrectly set to automatic mode.

Questions:

1) What was your ascent profile?  I'd love to remove engines--in a previous version, I had roughly 8 less engines, but I never could get to orbit in 1.1 so I added more engines.  I usually climb at 25-30 degrees until 8km, 15 degrees until 12km, then level off at 10 degrees for the remainder of the climb.  Should I be doing it differently?

2) Why is using less rapiers out of atmo more efficient?  I thought faster burns would be more efficient for orbital maneuvers, as long as the engines have the same ISP.

3) Any other tuning thoughts?

 

 

My official entry:

Craft File

 

Spoiler

Score:

18418 LF(.8)+13183 Ox(.18)=14734.4+2372.94=17,107.34

Edited June 25, 2016 by Lothsahn

[TaxiService]

Quote

It appears I also have more intakes than needed, which is just unnecessary drag, right?

Yes, one nose cone has fixed drag units, when compared to the multiple intakes AND Quad-Adapter of fixed drag units. It is possibly why you fought against so much drag during your original ascent to 12km.

4 hours ago, Lothsahn said:

Questions:

1) What was your ascent profile?  I'd love to remove engines--in a previous version, I had roughly 8 less engines, but I never could get to orbit in 1.1 so I added more engines.  I usually climb at 25-30 degrees until 8km, 15 degrees until 12km, then level off at 10 degrees for the remainder of the climb.  Should I be doing it differently?

2) Why is using less rapiers out of atmo more efficient?  I thought faster burns would be more efficient for orbital maneuvers, as long as the engines have the same ISP.

3) Any other tuning thoughts?

1) My ascent profile is directly derived from Val's profile for his Skylon SSTO below (with 350m/s instead of 450m/s).

Spoiler

Note: My downloaded Skylon is no longer working in KSP 1.1 due to the atmosphere changes (insufficient thrust at sea level).

The reasoning of my ascent profile is to channel most of the thrust energy into the horizontal speed and drag overcome while let the wing lift fight the gravity in the lower atmosphere of dense air. At the higher altitude of <22km, where the air is too thin for the drag to be effective, I pitch up to "throw myself as high as possible into the air" like a baseball off the bat before I activate the rocket mode when I no longer can gain any more speed.

Your ascent profile seems to be based on a different idea - get out of the lower atmosphere asap and do the majority of the work above 12km. I don't know if it is the efficient one but it should be good enough for an over-engineered SSTO plane.

2) You are right after I gave it some more thought. It should not matter how many RAPIERS to use as long as ISP remains unchanged. Please discard my statement about the two RAPIERS in my previous post.

3) One major feature to consider when designing a SSTO plane like this is to check how much drag is produced like this pic below during an ascent. Try to streamline the fuselage as much as possible. This includes the wings that have drags too.

Spoiler

Another thing to consider is if you find yourself gain speed too fast during an ascent, it is possible to have overkill acceleration. You could try lose one pair of engines without sacrificing the acceleration much. 

I don't really have other tuning thoughts as they are much dependent on the SSTO design like CoL at CoM/CoL behind CoM or one more engine but more "deadweight" fuel to carry?

Edited June 25, 2016 by TaxiService
More details

[MarvinKitFox]

On 2016/06/09 at 1:34 PM, icedown said:

Rules:

1.  
2. The craft must lift off horizontally from the runway and land the same way, as with a normal aircraft. Parachutes are allowed for assistance stopping.
3.  
4. The craft must have functional RCS to allow for docking and a usable docking port
5.  
6.  
7.  

 

These two rules have absolutely nothing to do with SSTO, or the role of fueltank-cargo-delivery that is being tested.

What if I want to design a paracute-landing vehicle?

What if I want to use vernier engines, or Ant motors, or whatever for my fine control?

Putting in rules like this is like saying I should design a good F1 racing car, any type I want, but it must be red and have a ferrari badge on it.

[icedown]

@Lothsahn That looks a lot like most of my designs

I will have the leader board updated in the next day or 2, work has been hell these last 2 weeks.

[foamyesque]

I don't have a full set of docs for this -- wasn't actually sure it'd work so I wasn't screenshotting things :v

 

Landed:

Tanks in orbit (taken after I landed the ship):

 

I make that as 10571 LF used, 7679 oxidizer, and 3.74 monoprop, for a score of 10571 * 0.8 + 7679 * 0.18 + 3.74 * 1.2 =  8456.8 + 1382.2 + 4.49 = 9843.5.

 

Not as good as some of the earlier ones, but I'll take it.

[RuBisCO]

I made the Xylan as a simple to fly heavy lifting SSTO, with very little modification it can do this challenge. So I added a few extra tanks and called it the "Xylan C". I used mechjeb to show performance and simplify flying with Smart SASS.

	Full	w/o cargo tanks	After landing	Consumed	Score
Fuel	18670	12910	342	12568	10054.4
Ox	16918	9878	397	9481	1706.58
				Total	11760.98

Flight Profile

1. Take off at full power to 150 m/s then pitch up

2. Retract landing gear

3. Maintain 20° pitch until reaching 400 m/s then pitch down to 15°.

4. Maintain 15° pitch until reaching 800 m/s then pitch down to 10°.

5. Maintain 10° pitch until reaching 20 km altitude then pitch up to 15°

6. Switch most engines to rocket mode at 21 km altitude (Key #1)

7. When final engine switches automatically close intakes (Key #2)

8. Once reaching >80 km apoapsis, coast at 10° pitch.

9. Change apoapsis to 300 km once reaching 80 km apoapsis.

10. Circularized at 300 km.

11. Released Cargo tanks.

12. Set periapsis to 20 km just a few hundred km in front of the space port,

13. Hit atmosphere at 20° pitch, skip along the atmosphere almost circumnavigating Kerbin.

14. If you set your periapsis point right you should be able to glide to the space port without using the engines.

- Remember to turn on intakes if you need engines (Key #2), set to jet mode (Key #1) and use just 4 engines (Key #3)

Craft file:

https://www.dropbox.com/s/3mt02v91yt8q916/Xylan Heavy SSTO.zip?dl=0

https://dropfile.to/H7UrxO5

Edited July 18, 2016 by RuBisCO

[Batz_10K]

This is one that I'm experimenting with. Not terribly efficient, but designed to carry cargo (externally) that is larger or awkwardly shaped which wouldn't fit in a cargo bay.

 

 

[parzr]

Here is my run, 10558.78

http://imgur.com/a/5KR5H

Edited July 24, 2016 by parzr

[mk1980]

On 24.7.2016 at 3:54 AM, parzr said:

Here is my run, 10558.78

http://imgur.com/a/5KR5H

that's a 70km orbit. the challenge is about flying the fuel tank to a 300km orbit.

[parzr]

13 hours ago, mk1980 said:

that's a 70km orbit. the challenge is about flying the fuel tank to a 300km orbit.

missed that part, I'll re-fly it.

http://imgur.com/a/5KR5H

Re-flew it to the proper altitude, 11560.24 and a slightly modified version at 11424.62

Edited July 26, 2016 by parzr

[timmers_uk]

Hello all,

Despite my best efforts, I've not yet got an entry for this challenge, but I have at least got far enough to have an attempt which is worthy of posting up so people can scoff at its failures.

The only reason I feel this is actually different enough to be worth posting up despite not getting past the winning line yet, is I've done the damn thing on PS4. (strictly speaking, I designed and tested a craft on PC, then tried to replicate said design on PS4, but the PS4 design ended up diverging in some significant ways).

I'll grab some stills if they are decent quality and push up an album in a bit, but for now here's the uncut VOD from twitch.

 

Let me see ...

Rules:

1. The craft must not lose any parts during any phase of the flight with the exception of the jettisoning of the two(2) FULL Rockomax Jumbo-64 Fuel Tanks at the 300km orbit.  This does not have to be done but the craft must be capable of it.Nope ... used the better part of 1 whole Jumbo-64 tank to circularise
2. The craft must lift off horizontally from the runway and land the same way, as with a normal aircraft. Parachutes are allowed for assistance stopping. Tick? I took off and landed horizontally, but my landing was nowhere near KSC.
3. The craft must reach an orbit of 300km +-5km both AP/PE After failing #1, whilst I had enough fuel to manage 300x300, I don't think I raised my orbit this high, but I certainly could have
4. The craft must have functional RCS to allow for docking and a usable docking port. Docking port yes, functional RCS, not so much - need to add those RCS thrusters
5. All fuel tanks, wings, engines, and external parts must be stock, no tweakscale either. Tick! Yeah ... non-stock parts would be lovely ... but ... console
6. Craft must be capable of sustaining its own power requirements through either solar panels or fuel cells (Fuel cell fuel burn will count against score) Tick1 - 2 1x6 solar panels
7. KJR is allowed.Tick! Again ... but ... console

[timmers_uk]

Ok ... having had my savegame corrupted again on PS4 I've switched back over to PC for now, and I'm pleased to say the concept I had was definitely workable (and flew 4x faster on PC due to staying 'in the green' almost entirely, which was nice).

As I've been pushing down the reusability road, the vehicle itself is entirely reusable, both refuellable and re-cargoable, using my patented cargo trolley + 'squat dock' technique

Not the most efficient launch in terms of fuel, but I am happy to have completed the challenge I think, even if I'm not going to be up there with the top-flight entries.

Starting Fuel (after refuelling) - 22650LF, 13750 LOx (including payload). 16890 LF, 6710 LOx (excluding payload)

Fuel remaining on landing (it was on landing, right? not at 300k x 300k orbit) - 256LF, 1039 LOx

Fuel usage - 16634 LF, 5761 LOx.

Points - 0.8 * 16634 + 0.18 * 5761 = 14327.98 (I think?)

No monoprop because I used vernors for RCS.

Will grab the summary pics and punt them to imgur after work.

Ascent profile :-

Take Off, hold altitude below 1000m until 400m/s reached, pitch up to 10deg. 5000m altitude light the nukes. 6000-10000m nose 1 deg per 1000m. Hold pitch at 5deg until thrust tail-off or overheating, raise nose to lessen heat-load. Switch to closed cycle ~1450m/s. Drop nose to prograde when possible. Burn till apo ~70km and time to apo > 2min. Shutdown rapiers. Burn prograde till apo reaches 300km, then circularise at 300km.

Landing Profile :- 

Reduce orbit to 80km x 80km. Retro burn to ~ -18km peri. Hold attitude about 20deg during re-entry. Light airbreathing rapiers to tweak for direct arrival at KSC runway 09.

 

Rules:

1. The craft must not lose any parts during any phase of the flight with the exception of the jettisoning of the two(2) FULL Rockomax Jumbo-64 Fuel Tanks at the 300km orbit.  This does not have to be done but the craft must be capable of it. Looks good to me - we'll not talk about the refuelling dolly self-destructing on the runway. That wasn't part of the craft
2. The craft must lift off horizontally from the runway and land the same way, as with a normal aircraft. Parachutes are allowed for assistance stopping. Tick - I try not to use the drogue chute, but landed nearer the wrong end than I'd like, as I now need to build a cherry picker to be able to get a kerbal to repack it at KSC.
3. The craft must reach an orbit of 300km +-5km both AP/PE. Tick
4. The craft must have functional RCS to allow for docking and a usable docking port. Tick and tick - docking port used while refuelling, Vernors for LFO RCS
5. All fuel tanks, wings, engines, and external parts must be stock, no tweakscale either. Tick - used smart A.S.S. for attitude control, and maneouvre planner for circ, just to leap into that controversy with both feet, but parts are all stock
6. Craft must be capable of sustaining its own power requirements through either solar panels or fuel cells (Fuel cell fuel burn will count against score) Tick - One 1x6 solar panel
7. KJR is allowed.Didn't use KJR. Used many struts instead.

Hope I haven't missed anything - its been fun attempting this challenge, and it has inspired me to have a little 'fun' with it, which I may get a chance to do over the next week

 

Timmers