Low throttle to orbit!

[Pds314]

Mission

Get a Kerbal to orbit with as low a thrust limiter setting as possible.

The scoring will be done by dividing 1000 by your thrust limiter and the natural log of your cost in the VAB/SPH.

If you have multiple engines with different limiter settings, the highest thrust limiter will be counted for the final value.

Score = 1000 / (Thrust Limiter*ln(cost))

 

Rules

0. Stock, DLC, and informational mods only.

1. No reactionless drives, Kerbal EVA packs,  KAL-9000 outside slider range bug, or abuse of heat shield lifting properties.

2. Lander leg cannons or similar are prohibited.

3. If I feel decouplers are providing you hundreds or thousands of meters per second of delta-V, I may ask you to redo the run with the force percent at whatever your thrust limiter is supposed to be. This really should only affect exploitative designs.

4. You may choose whatever stock launch site you wish, and may takeoff vertically or horizontally, but remember, recovery does not affect score.

Edited November 27, 2020 by Pds314

[ralanboyle]

Okay, I'm not sure if I'm supposed to add the cost and thrust limit, or multiply. And I'm not sure if the thrust is 20, or 0.2. So I'll let you do that math. 

Cost is 13,343. All staged are thrust limited to 20%.  

 

[EveMaster]

Throttle is 10%. Funds is 83,526. The craft has three stages. The last stage has only a ladder for the kerbal to grab onto to save the weight of the external command seat.

Spoiler

 

Edited November 25, 2020 by EveMaster

[Pds314]

Nice. Yeah sorry about the confusion scoring method.

@ralanboyle your score is 5.26.  I like the choice of using all SRBS until the upper stage. They definitely have both the TWR and the cost for this challenge.

@EveMaster your score is 8.82. I like the idea of the ladder upper stage. Reminds me of interplanetary missions in the Caveman challenge. Do be careful not to push against a wall with Kerbals on ladders or they will generate phantom thrust, but this one is clearly fine. It is kinda amazing how strong the vectors and mammoths are for this challenge, but I guess the cost does sorta offset that at least a little bit. As the natural log of your cost is 11.3 vs like 8 or 9 for a cheap craft.

Edited November 26, 2020 by Pds314

[ralanboyle]

@Pds314 your math is too strong for me. I thought for sure being 7 times cheaper would earn a higher score. Oh well, I'll go at it again with an expensive craft and see what I can do. 

[Pds314]

21 minutes ago, ralanboyle said:

@Pds314 your math is too strong for me. I thought for sure being 7 times cheaper would earn a higher score. Oh well, I'll go at it again with an expensive craft and see what I can do. 

Yeah it's deliberately designed to make cost a very subtle factor. The difference between a craft costing 1000, probably the cheapest that could reach orbit, and 1000000, some giant monstrosity of mammoth spam, is a factor of 2 because it scales logarithmically. The idea is more "subtle encouragement not to overdesign" than "cost is as important as thrust limiter." Think of cost as a tie breaker. 

Edited November 26, 2020 by Pds314

[camacju]

You may want to add a rule to prevent a Kal 9000 fuel or thrust glitch since you're permitting DLC

[Pds314]

4 hours ago, camacju said:

You may want to add a rule to prevent a Kal 9000 fuel or thrust glitch since you're permitting DLC

True yeah. Added to rule 1.

[EveMaster]

On 11/26/2020 at 2:12 AM, Pds314 said:

It is kinda amazing how strong the vectors and mammoths are for this challenge, but I guess the cost does sorta offset that at least a little bit. As the natural log of your cost is 11.3 vs like 8 or 9 for a cheap craft.

 

On 11/26/2020 at 2:47 AM, Pds314 said:

Yeah it's deliberately designed to make cost a very subtle factor. The difference between a craft costing 1000, probably the cheapest that could reach orbit, and 1000000, some giant monstrosity of mammoth spam, is a factor of 2 because it scales logarithmically. The idea is more "subtle encouragement not to overdesign" than "cost is as important as thrust limiter." Think of cost as a tie breaker. 

Since no one has done so far, I will post another submission that involves Mammoth/Vector spam. I mostly used Vector instead of Mammoth, even though four Vectors weight one ton more than one Mammoth, because Vectors are more compact. I noticed that the sepatrons can give a good boost for the upper stage because of their high TWR ratio. The twitch engines are also a better for the upper stage than the spark engine. The slightly better ISP of the spark does not make up for the worse TWR. I kept clipping at a minimum. All Mammoth engines are beefed up by an additional 6 Vector engines. I used normal struts in addition to autostruts to keep the first stage stable.

Total cost is 4,064,423, thrust limit is 7%. So my total score is 9.39. The weight is 1,150 tons.

The craft has 7 stages:

• Stage 1: 170 Vector
• Stage 2: 5 Mammoth + 30 Vector
• Stage 3: 1 Mammoth + 6 Vector
• Stage 4: 1 Vector
• Stage 5: 1 Aerospike
• Stage 6: 8 Sepatron + 4 Twitch
• Stage 7: 4 Twitch (same engines as in stage 6)

The mass of the craft splits up as follows:

• 78% engine
• 18% propellant
• 4.6% structural
• 0.0082% payload (1 Kerbal)

I start the ascent vertically and start to tilt slightly at the end of stage 2. Throttle is at maximum all the time (No need to reduce the throttle even further than the 7 percent ) The decoupler between stage 4 and stage 5 is set to allow fuel transfer. 1/3 of the fuel of stage 5 is burned by the vector stage, otherwise the low thrust of stage 5 would last too long. At the end, 550 m/s of fuel is left. This is enough to deorbit safely when using also the EVA pack and the Kerbal parachute.

Pictures of the ascent:

Spoiler

 

[Pds314]

13 hours ago, EveMaster said:

 

Since no one has done so far, I will post another submission that involves Mammoth/Vector spam. I mostly used Vector instead of Mammoth, even though four Vectors weight one ton more than one Mammoth, because Vectors are more compact. I noticed that the sepatrons can give a good boost for the upper stage because of their high TWR ratio. The twitch engines are also a better for the upper stage than the spark engine. The slightly better ISP of the spark does not make up for the worse TWR. I kept clipping at a minimum. All Mammoth engines are beefed up by an additional 6 Vector engines. I used normal struts in addition to autostruts to keep the first stage stable.

Total cost is 4,064,423, thrust limit is 7%. So my total score is 9.39. The weight is 1,150 tons.

The craft has 7 stages:

• Stage 1: 170 Vector
• Stage 2: 5 Mammoth + 30 Vector
• Stage 3: 1 Mammoth + 6 Vector
• Stage 4: 1 Vector
• Stage 5: 1 Aerospike
• Stage 6: 8 Sepatron + 4 Twitch
• Stage 7: 4 Twitch (same engines as in stage 6)

The mass of the craft splits up as follows:

• 78% engine
• 18% propellant
• 4.6% structural
• 0.0082% payload (1 Kerbal)

I start the ascent vertically and start to tilt slightly at the end of stage 2. Throttle is at maximum all the time (No need to reduce the throttle even further than the 7 percent ) The decoupler between stage 4 and stage 5 is set to allow fuel transfer. 1/3 of the fuel of stage 5 is burned by the vector stage, otherwise the low thrust of stage 5 would last too long. At the end, 550 m/s of fuel is left. This is enough to deorbit safely when using also the EVA pack and the Kerbal parachute.

Pictures of the ascent:

  Hide contents

 

Wow that's even lower thrust than my designs for separatron only entries.

[EveMaster]

On 12/13/2020 at 2:57 PM, Pds314 said:

Wow that's even lower thrust than my designs for separatron only entries.

I now managed to get to orbit with only 4% thrust. The trick was to build a multi staged Vector powered space plane. This way I could get away with a TWR of less than 1 for most of the ascent. To get to a suborbital trajectory I used a stage with 72 sepatrons to achieve a TWR of over 1 for most of this stage. To circularize, a stage with a TWR less than 1 was enough.

Cost: 624,718

Thrust limiter: 4%

Score: 18.73

Mission report: https://imgur.com/gallery/po6XmIC

Craft file: https://kerbalx.com/EveMaster/4PercentThrustToOrbit

Edited March 13, 2021 by EveMaster