Tylo Lowest twr Lander Challenge!

[Arecibo Kerman]

Landing on Tylo is hard. Because of the high gravity a high twr is recommended for landers. 

I ask you to do the opposite and design a Tylo lander with the lowest twr you can.

                        Tylo in all its Glory

Your aim is to make the lowest twr Tylo lander possible, there are 3 categories:

 

Stock:

Build a lander using stock + DLC parts.

Prohibited Mods: Part mods, Any mod that changes physics, Any mod that alters Tylo (visuals ok).

 

Modded:

Build a lander using appropriate part mods.

Prohibited Mods: Futuristic part mods, Any mod that changes physics, Any mod that alters Tylo (visuals ok). 

 

Go wild:

Anything goes! (except altering Tylo)

Prohibited Mods:  Any mod that alters Tylo (visuals ok).

 

Rules:

1. NO PROHIBITED MODS !

2. No excessive clipping of functional parts.

3. The lander's final stage must be whole upon touchdown.

4. Land at a suitable speed (under 15m/s).

5. The Kerbal has to be in a pressurised container, no chairs or ladders.

6. No exploiting game bugs of physics.

7. If you do find a loophole to the rules and it is used in your entry is will be put in the "Rouges Gallery".

8. No deliberate extra weight, everything needs to have a purpose.

9. There must be engines attached once landed.

10. Prohibited mods: Futuristic tech, Near Future Propulsion, Anything that changes the Jool system.

11. No Orion Drives from anywhere.

12. No stock exploits.

13. Apoapsis has to be below 30km.

 

To Submit:

Credit to @dnbattley

Take a screenshot in low Tylo orbit showing the Twr and burn time.

Then take a screenshot of the twr and full fuel usage just before jettisoning each stage.

After jettisoning each stage show the full burn time of that stage. 

Take a screenshot of the lander safely on the surface of Tylo. In one piece.

The burn time and twr readouts come form the stock DeltaV indicator.

 

Scoring:

Also credit to @dnbattley 

((1-maxTWR_stage) x net burn time_stage)

i.e. a 3 stage lander which operates at (0.5x rising to 0.7x) TWR for 100s, (0.6x rising to 0.9x) for 30s, then (1.0x rising to 1.3x at landing) for 95s would score 0.3x100 + 0.1*30 -0.3x95 = 30+3-28.5 = +4.5

 

Tips:

1. You can cheat the lander to Tylo orbit if you want. Kudos if you don't.

2. No need to go home or back to orbit. Again Kudos if you do.

 

Leaderboard:

Modded:

Stock:

Go Wild:

Rouges Gallery (This is where all the entries that don't quite fit the rules go): 

 

Other Stuff:

The smaller the better.

DLCs count as stock.

 

Good Luck!

Arecibo,

Edited September 3, 2021 by Arecibo Kerman
Scoring system

[Arecibo Kerman]

Reserved

[ManEatingApe]

This is fun challenge! I can think of 2 different strategies that could result in a lander with a final TWR of 1 (wrt Tylo local gravity).
Both approaches will require top notch piloting skills and nerves of steel...

Constant Altitude Burn

Good description and discussion in these threads:

• What is the most efficient way to deorbit+land?
• Most Efficient Way to Land: Suicide Burn, good. Constant Altitude, better... Gravity Turn... Best?

A constant altitude burn is more delta-v efficient than a suicide burn as TWR drops. In a nutshell the approach is:

• Enter circular orbit at the same altitude as the location that you want to land at (e.g on top of a handy mountain)
• Thrust mostly parallel to the surface, pitching up just enough to keep vertical velocity zero and altitude constant (hence the name of the maneuver)
• In theory with a TWR of 1, come to a perfect landing with the craft vertical (hovering against gravity) and horizontal velocity at zero.

Brake Pad Insanity Burn

This second approach is slightly more Kerbal:

• Find a nice flat patch of ground
• Come screeching in at ~2,300 m/s, using engines to keep vertical velocity zero
• Brake to a halt using wheels

Edited June 13, 2021 by ManEatingApe

[dnbattley]

I may have to review my official Jool 5 submission lander for this challenge, as (for mission design reasons) I recall it had an abysmal TWR that started at 0.9x, and only struggled up to something like a respectable 1.5x by the time it landed...

[king of nowhere]

twr changes as the rocket burns fuel. what's the value that matters? before deorbiting? I can make a heavy lander with lot of mass that will be ejected lately. In the moment of touchdown? I can make a good lander that jettisons engines shortly before landing. rules of challenge must be more specific.

[Arecibo Kerman]

4 hours ago, king of nowhere said:

twr changes as the rocket burns fuel. what's the value that matters? before deorbiting? I can make a heavy lander with lot of mass that will be ejected lately. In the moment of touchdown? I can make a good lander that jettisons engines shortly before landing. rules of challenge must be more specific.

Yeah I noticed that edited it now 

Edited June 13, 2021 by Arecibo Kerman

[Arecibo Kerman]

5 hours ago, ManEatingApe said:

Brake Pad Insanity Burn

This second approach is slightly more Kerbal:

• Find a nice flat patch of ground
• Come screeching in at ~2,300 m/s, using engines to keep vertical velocity zero
• Brake to a halt using wheels

Yes, that is very Kerbal 

But... rule 4 states: 4. Land at a suitable speed (under 15m/s).

So that would be in the Rogues gallery.

But I would like to see a attempt in that manner!

I'd give it a go anyway.

 

Edited June 13, 2021 by Arecibo Kerman

[Arecibo Kerman]

4 hours ago, dnbattley said:

I may have to review my official Jool 5 submission lander for this challenge, as (for mission design reasons) I recall it had an abysmal TWR that started at 0.9x, and only struggled up to something like a respectable 1.5x by the time it landed...

Looked at the album and found values 0.9 and 1.47 or a score of 2.37. Good one!

[Teilnehmer]

On 6/13/2021 at 6:31 PM, Arecibo Kerman said:

Your score is your Finishing twr + Starting twr.

What about the TWR in between?

One can build a 3-staged lander with a big high-TWR middle stage and tiny low-TWR 1ˢᵗ and 3ʳᵈ stages just for the score.

I’d suggest a score system based on the max TWR during the flight.

[Arecibo Kerman]

fair point 

12 hours ago, Teilnehmer said:

What about the TWR in between?

One can build a 3-staged lander with a big high-TWR middle stage and tiny low-TWR 1ˢᵗ and 3ʳᵈ stages just for the score.

I’d suggest a score system based on the max TWR during the flight.

any other ideas for scoring systems

[EveMaster]

2 minutes ago, Arecibo Kerman said:

any other ideas for scoring systems

Max TWR seems to be the best option.

For the max twr definition there are two options:

• Based on the readouts in the vehicle assembly building and standard gravity, assuming all stages are used
• Based on the flight profile, the local gravity and the remaining fuel at landing

I'm unsure which of these options is better. Both have their pros and cons.

[dnbattley]

5 hours ago, EveMaster said:

Max TWR seems to be the best option.

<edit> I misread your initial suggestion. I agree with this and would suggest the following scoring:

1. an initial reading (screenshot) be submitted at the chosen point of descent (i.e. when pE is ~0m) using the stock dV calculator showing TWR and burn time

2. a screenshot be required immediately prior to and after jettisoning each stage, demonstrating i) full use of prior stage fuel and max TWR of the prior stage and ii) max burn time of the following stage

3. scoring is defined as:

SUM ((1-maxTWR_stage) x net burn time_stage)

i.e. a 3 stage lander which operates at (0.5x rising to 0.7x) TWR for 100s, (0.6x rising to 0.9x) for 30s, then (1.0x rising to 1.3x at landing) for 95s would score 0.3x100 + 0.1*30 -0.3x95 = 30+3-28.5 = +4.5

Edited June 16, 2021 by dnbattley

[Arecibo Kerman]

Sorry but I seem to have abandoned, will rectify immediately.

I am going with @dnbattley's scoring suggestion.

[Space Kerbalisation Tech]

On 6/13/2021 at 7:31 PM, Arecibo Kerman said:

Then take a screenshot of the twr and full fuel usage just before jettisoning each stage.

 

I just found something that could be a loophole: by taking a screenshot of the twr and fuel thing, i presume you mean from something like the stock delta v readouts or a mod readout like MechJeb or KER

But, there are some unusual mod parts that are engines but the TWR dosen’t show up on the readout. The mod I was saying about is this 

 

The engines in this mod uses NUCLEAR BOMBS to produce thrust so it should have high TWR, but it produces impulse instead of continuous thrust so KSP doesn’t recognise  it, therefore showing 0 delta v and most importantly, 0.0 TWR

Does this count?

[Arecibo Kerman]

@Space Kerbalisation Tech

Ok updated rules but will check.

(11. No Orion Drives from anywhere.)

Edited August 16, 2021 by Arecibo Kerman

[AlpacaMall]

Regarding rule 3: What counts as the “final stage” of a lander? For example:

* I have a large, high-TWR stage I eject a meter above the ground

* I lithobrake with a stage, but eject it before coming to a halt

I’m assuming that the first one is fine and the second one isn’t, but where’s the line between the two?

 

Also, what’s the point of rule 8? 

[vyznev]

11 minutes ago, AlpacaMall said:

Regarding rule 3: What counts as the “final stage” of a lander? For example:

* I have a large, high-TWR stage I eject a meter above the ground

* I lithobrake with a stage, but eject it before coming to a halt

I’m assuming that the first one is fine and the second one isn’t, but where’s the line between the two?

I can't speak for the OP, but I assume the intent of rule 3 is something like: "No destructive lithobraking. You can discard used stages and have them crash on the surface, but that must happen well away from your actual lander. The lander itself, or anything in contact with it, must not hit the ground hard enough to break any parts."

(Also, rule 4 puts additional constraints on both destructive and non-destructive lithobraking, and I assume it's also intended to apply to anything in contact with the lander at the moment of impact.)

Anyway, lithobraking on Tylo has been done already by @sturmhauke. (Not from full orbital velocity, though, which you'd kind of need to do if you wanted to aim for TWR ≈ 0. But TWR < 1 with lithobraking seems doable to me. Just not in this challenge.)

[sturmhauke]

To clarify, that mission involved burning to a halt at 20km above the landing zone and then dropping straight down, unpowered. Impact speed was 557.2 m/s, and there were multiple layers of ablative struts and wheels.

[CFYL]

On 6/13/2021 at 7:31 PM, Arecibo Kerman said:

((1-maxTWR_stage) x net burn time_stage)

I believe this scoring rule is useful but has a loophole. If I somehow use an ion engine (i.e. RTG-powered low TWR ion thruster(s)) to slow down from an absurdly high orbit to low Tylo orbit, and then do a landing with a few stages all with appropriate TWR, this will get a heck lot of points out of the scoring rule, but will also spoil the fun. The solution may be "Everyone just do the challenge as what it was supposed to be and do not exploit anything."

[EveMaster]

10 hours ago, AllenLi said:

I believe this scoring rule is useful but has a loophole. If I somehow use an ion engine (i.e. RTG-powered low TWR ion thruster(s)) to slow down from an absurdly high orbit to low Tylo orbit, and then do a landing with a few stages all with appropriate TWR, this will get a heck lot of points out of the scoring rule, but will also spoil the fun. The solution may be "Everyone just do the challenge as what it was supposed to be and do not exploit anything."

I thought about that at first, too. But the time starts when the periapsis is at 0m. So unless you raise the periapsis up again into a proper orbit, that limits how long you can maintain the ultra low twr. Raising the periapses back above 0m once the descent has started should not be allowed in my opinion.

[vyznev]

On 8/17/2021 at 10:26 PM, EveMaster said:

I thought about that at first, too. But the time starts when the periapsis is at 0m. So unless you raise the periapsis up again into a proper orbit, that limits how long you can maintain the ultra low twr. Raising the periapses back above 0m once the descent has started should not be allowed in my opinion.

Even so, falling from high orbit takes a loooooooong time.

IMO, the simplest fix would be to just specify a reasonable maximum starting apoapsis altitude. Maybe 30 km? (And, yes, forbid raising periapsis above 0 m after timing has started.)

[ManEatingApe]

Let's get the ball rolling with an actual entry!

The first task is to find a suitable spot to land. A kOS script scans Tylo's equator looking for the highest point. At longitude -73.7927 it finds a nice mountain at 9,074m elevation. There are higher spots elsewhere on Tylo but choosing a location on the equator makes targeting a precise landing easier.

Next task is to design a suitable craft. A second kOS script simulates a constant altitude landing burn, predicting the final TWR, burn duration and delta-v needed, so that the craft design can iterate quickly without needing trial and error.

Lastly, let's fly the mission. A third kOS script controls the craft, performing a precision landing at our desired location.

Let's see how the simulation compared against the actual mission.

	Predicted	Actual
Duration	434s	450s
Delta-V	3,266 m/s	3,383 m/s
Initial TWR	0.63	0.63
Final TWR	0.95	0.97

Not too shabby! The main difference is that the simulation ignores the final vertical landing phase for simplicity, causing a slight discrepancy.

For anyone considering an entry, please feel free to use, tweak, modify and improve the scripts linked in this post.

[Klapaucius]

@ManEatingApe I love the fact that despite needing to keep mass down to a minimum, you still found room for fireworks.  I like your priorities.

[Arecibo Kerman]

On 8/17/2021 at 10:10 AM, AllenLi said:

The solution may be "Everyone just do the challenge as what it was supposed to be and do not exploit anything."

exactly 

I really don't have time to find every loophole