goduranus

VAB horizontal landing challenge

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Posted (edited)

We see VAB landings by VTOLs or with parachutes regularly. But a real challenge would be a conventional landing. So here's a challenge for that

Score will be based on the horizontal flight capabilities of the craft used in the attempt, rewarding craft size and speed. A speed requirement is set to prevent excess wing spam, and also a no-detachment rule is set so that the configuration used to clock max speed is the same as the configuration used for landing.

Scoring:

  • Score = (Mass of craft in tons after landing) * (Maximum clocked speed of the craft in atmosphere in km/s)
  • The whole craft must land intact on top the the VAB
  • Please provide a screenshot of the F3 menu after clocking speed, and also a screenshot of the craft landed on VAB plus some description of how you've managed the feat

Rules:

  1. Stock Parts only for simplicity
  2. All engines point straight to the back
  3. Landing attempt done at no more than 45 degree pitch up from the horizon
  4. Only jet engines
  5. No parachutes
  6. No reaction wheels except those built into cockpits or probe cores, max of 1 cockpit and 1 probe core
  7. Limit of 100 parts, so better PCs won't be at an advantage
  8. No parts should be detached after takeoff
  9. No editing the craft file with text editor or mods to squeeze out extra performance.
  10. No altering of Kerbin's properties with Alt-F12 menu to reduce gravity or increase drag etc.

Some tips

  • The challenge gets much easier if you put something small on top of the VAB and target it during your approach, so your know exactly where the VAB roof is by looking at the Navball, and can keep your velocity vector lined up with it. Eyeballing this landing is almost impossible.
  • It's probably a good idea to set each landing gear's braking force to max or you won't stop in time, and also make sure to use a landing gear that has brakes, as some of them don't.
  • I think the trick to accomplishing this is to get up to about 2km high and 5-6 km away from the KSC, then throttle down to about 1/4 and pitch up until you get to a comfortably low speed and your velocity vector on the Navball is pointed right at the target you placed on the VAB, then control your descent rate with throttle, and engage brakes right as you touch down.

My attempt:

Sorry no screenshot, I pitched up too much during the approach, engines hit the helipad, causing the plane to bounce, which then settled on the roof beneath the helipad after also losing a nosecone. Someone had done it on YouTube, but with a wing-spamming plane dropping almost straight down onto the VAB with no VTOL engines or parachutes, but wingspam is unrealistic so I put in top speed as a part of the score, 

 

Leaderboard:

  1. @AeroGav 49.16 points (34.62tons*1.42km/s https://forum.kerbalspaceprogram.com/index.php?/topic/164298-vab-horizontal-landing-challenge/&tab=comments#comment-3170162)
  2. @zolotiyeruki 31.03 points (19.794 tons *1.568km/s https://forum.kerbalspaceprogram.com/index.php?/topic/164298-vab-horizontal-landing-challenge/&do=findComment&comment=3172691)
  3. @qzgy 20.625 points (16.5 tons*1.25km/s http://forum.kerbalspaceprogram.com/index.php?/topic/164298-vab-horizontal-landing-challenge/&do=findComment&comment=3145933)
  4. @Eidahlil 13.01 points (13.69 t x 0.95 km/s, http://forum.kerbalspaceprogram.com/index.php?/topic/164298-vab-horizontal-landing-challenge/&do=findComment&comment=3145668)
  5. @Eidahlil 8.46 points ( 8.46 t x 1.00 km/s)

 

Unsuccessful attempts

  1. goduranus 10.53 points (8.56 ton craft at top speed of 1.23 km/s, lost an engine and a nosecone)

 

Edited by goduranus

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You don't mention it but I suppose no autopilot mod. Also think is a good idea to define your instance aboout info mods to avoid confusion.

Seen like a fun challenge that I'd like to participate. Unfortunately I don't foresee timr available for it.

 

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Posted (edited)

A few rules questions:

1. Can we use indestructible buildings? With heavier craft, the slightest bump causes VAB to collapse (not used in the attempts below).

2. When is the 45 pitch rule calculated? Can the plane do a loop before landing (like below)? Can it do a cobra right before landing?

Aerobatic attempt - 8.46 t x 1.00 km/s = 8.46 points:

Low wing loading attempt - 13.69 t x 0.95 km/s = 13.01 points (craft download http://kerbalx.com/juzeris/Bigfrid-Civilian.craft )

 

Edited by Eidahlil

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Wow Eidahlil, nice flying, you made it look easy!

To answer your questions

1. Yes absolutely enable indestructible buildings, I didn't even consider the possibility that a plane so heavy can be landed on it, but now it looks like that can be done.

2. The 45 degrees rule is calculated at the moment your plane touch the VAB, it's just to prevent a plane from landing on its tail as a psuedo VTOL, doing a loop is absolutely allowed.

@Spricigo I am not sure if autopilot mod would make it easier, as I never tried any of those, I guess autopilot is allowed, but using non-stock parts is not allowed. So if it needs a part like mechjeb does please don't use it.

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Posted (edited)

Well, not sure about how MJ fare but Kramax or KOS certanly make things easier (IMHO a lot).

In any case, as I see it, is more a matter of how much 'computer aid' you feel acceptable. Your chalenge, your decision.

Btw. MJ can be setup to not require non-stock parts. In my limited knowledge seems to be the general rule for this kind of mod.

 

Edited by Spricigo

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Posted (edited)

So I gave this a shot.

Speed run

7gJ3a7H.png

Max speed of 1.25 km/s

Landing

z2tfh2o.png

Zl19P6x.png

Ewj7F0G.png

Tonnage - 16.5

16.5*1.25 = 20.625

 

Note: Part clipping was used. I have two wheesleys also inside of the space where the whiplash is. Wing spamming was not done. The speed run and landing were done in two seperate launches, however, nothing was changed between those. I simply reverted back to launch

Edited by qzgy

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20 minutes ago, D.U.N.E said:

One question, can you do a 360* landing?

I want to know this too. I also want to know if we can use reverse thrust.

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1 hour ago, sevenperforce said:

I want to know this too. I also want to know if we can use reverse thrust.

I used reverse thrust on my entry. I'm pretty sure he's fine with it.

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Can we use the rapier in non-rocket mode/ use the aerospike? Also are air-brakes against the rules? They feel like you might class them as a parachute idea, but for certain wing widths they can be essential.

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What's a 360 landing, one where you spin horizontally? It's fine as long your craft isn't a dedicated spinner. Reverse thrust, airbrakes, and air-breathing rapiers are fine. Don't use aerospike though, that's a rocket and doesn't have a rampup time.

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This really wasn't a good idea, about the worst possible thing you could try and put on anyone's roof.      Anyway, after over 30 attempts I finally got this 34.62 Ton monstrosity up there.

https://www.dropbox.com/s/2vr88jeylc53awi/stol 2.craft?dl=0

Top speed? I'm working on that part..      Uploading is a bit slow,  and I'm not entirely sure the best way to measure it..  you'll see what i mean..

Edited by AeroGav

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OK,  here's the speed part.   Yeah  , I managed to bork the takeoff as well, but we got there.

Spoiler

2294 m/s at the end of the video, with another 2707 m/s delta V in the tank.    No ISRU or gravity assists because that's cheating :-)

Tips and Findings

1.   Approaching the VAB  from the ocean is better as you can use the crawlerway to line up on well before the VAB is big enough to see properly.

2.  The crawlerway and VAB are orientated on the same heading as the runway -  270deg due west.    So, if your airplane's heading is 267, then it's gradually going to drift left of the helipad even if you fly straight and level.  Conversely, if you're heading 273, you'll be drifting to the left.

3.  Modifying an existing ssto for this job was a bad, bad idea.   Particularly, having 3 ton nukes hanging off each wingtip gives huge roll inertia compared with having them as far inboard as possible.     This is compounded by lack of aileron authority at low speed.

4. Furthermore,  when the airplane is at a high angle of attack, and you move an aileron to pick up a wing, that aileron gets an even higher angle of attack and produces huge drag , and therefore yawing moment, on that side.   As a result when you turn in one direction the nose initially yaws the opposite way.   I recommend fitting the largest ailerons possible, but turn down their authority in the tweakables, this lowers the deflection angle to something less yaw-inducing.  Also, at low speed the effectiveness of the tail surfaces to damp these yaw excursions is reduced, as you can see i ended up fitting larger and larger vertical fins on the airplane.

5. This adverse yaw can lead to a cycle of overcontrolling.   You want to turn right, but the nose yaws left, which makes you roll harder to the right until you overshoot etc.  I learned to ignore what the nose was pointing at and follow the prograde marker instead.   And yes, if only i'd put a flag on the helipad i could just keep my eyes fixed on the navball !

6.  Toggling the Panthers in and out of afterburner mode allows instant adjustment in engine power without spoolup delay, albeit this does limit you to just two states.   I don't regard that as a cheat, since I know the F-18 can turn on its afterburner, obviously at a reduced fuel rate,  at idle rpm.

 

Taking off and going to orbit  - nothing to write, though as i was at this point flying an untested prototype.    I ended up improvising and discovered a new way to keep the plane level on the speedrun !

Think a custom design would be best, for anyone wanting to emulate this.   The engine combo worked well but cluster them in tight either side of the cockpit and then stack biplane wings above and below , to make something more nimble.

Edited by AeroGav

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One problem: you need to say that editing the physics in anyway (including editing the physics config) is banned. You only said from the altf12 menu.

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Adding the scores, @AeroGav's  top speed for scoring will be only 1420 because as he used rockets after this.

 

 

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