FlyingPete

Unpowered atmo limbo

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The concept is simple. Re-entry from orbit, get as close to the ground as possible and return to space. No engine firing allowed while in atmo.

So this will take efficient aerodynamics to get back into space, and good cooling design to prevent from being cooked.

Any kind of ship design is allowed as long as engines are off once you enter the atmosphere.

 Separate limbo categories for:

Planet Record  Gained By
Duna 888m Kulebron
Laythe    
Kerbin 12,965m Kulebron
Eve    
Jool    

 

Edited by FlyingPete
New records

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Well on Kerbin for example, getting 5m below 70km and coasting back out again would count, and the record would then be set at 69.995km. There's no set target, but the lower the better!

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Reentry means slowing down your craft, we're talking about a slowdown from 2000m/s speed into around 500m/s speed. Without engines to provide a means of propulsion to regain speed, are you really sure we can get as close to the ground as possible and climb straight back to the space 50-70km above, unpowered? If this is possible, then we already did this a loooong time ago because why bother building complex spaceplanes? When unpowered gliding can take you to space alone? Mind you, at around 50km above, atmosphere is so thin that it barely provides any lift whatsoever. Yes, at lower atmosphere you can gain altitude by gliding, but at higher atmosphere, you cannot do that since no air to provide lift. What you are talking in example is basically aerobraking, and we already did that on regular basis in interplanetary travel

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I don't mean re-entry as in slowing down to <1000m/s, rather an orbit or flyby with a Pe inside the atmosphere, and coasting through and back out into space. Obviously slowing right down and getting back to space without engine firing isn't possible- you need to carry enough speed through to get back into space.

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1 hour ago, FlyingPete said:

I don't mean re-entry as in slowing down to <1000m/s, rather an orbit or flyby with a Pe inside the atmosphere, and coasting through and back out into space. Obviously slowing right down and getting back to space without engine firing isn't possible- you need to carry enough speed through to get back into space.

Hmmmm, very interesting.

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2 hours ago, CairoJack said:

Can you prove that this challenge is possible ?

Don't be silly, of course it's possible. Can't you at least try to understand the challenge before posting the submission guide at people?

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I turned off re-entry heating to find out how many gees you can pull and discovered that clockwise orbit around the sun + kerbin intercept with PE of 30km = still has escape velocity. Re-entry heating glitched out though and believed the craft was dead before the solar panels broke off. Boo.

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Hmmm. Lots of ore ballast in a Mk3 Cargo bay, pointy tip & tail - > hardly any slowdown due to drag. Starting at 1080km to a 30km PE, I returned to a 1070km AP even though the nose burned off at 31km.

@FlyingPete: you should probably make clear a) if it is OK to lose parts, b) if heatshields may be used.

Without losing parts and heat shields, it's probably down to the 2400K heat resistance of the best tips.

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Here's my attempt. This one reached slightly below 20 km in Kerbin's atmosphere.

fhv3Igt.png

RcmobSK.png

2PqdqYn.png

Video:

I used Alt+F12 to cheat the vessel into orbit. I assume that's OK for this challenge? There's no real reason why I couldn't have launched it from KSC, but that would've just made the process more tedious.

Anyway, my approach was to just try to punch as straight through the atmosphere as possible with a massive but narrow ship. I used the 10m heat shield on the front, since in its uninflated form it's got a particularly nice combination of low drag and high heat tolerance. Unfortunately it's not an ablative heat shield, so it can't soak up as much heat as the other heat shield types, and this flight pushed it pretty close to its limit.

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Getting your spacecraft into the relevant orbit is allowed by any means you like as that's not relevant to the challenge. Heat shields (or anything else used as ablative armour) and staging are also fine unless said staging is used for nefarious purposes like providing significant thrust through decoupler spam. You could throw an asteroid at a planet an use that if you wanted to. Ballistic trajectories and aerodynamic craft are treated equally.

Looks like the Kerbin record is currently held by vyznev at 19,965m according to the video.

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Here's my entry. I think I can get lower still, but 14,857 meters is nothing to sneeze at.

screenshot67.png

Full album:

Spoiler


screenshot65.png
screenshot67.png
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screenshot101.png

At first I thought this would be about heat management, but it's not. It gets hot, of course, but the big issue is energy management -- maintaining enough momentum to make it up and out of the atmosphere. You can do that by getting a lot of speed (a hyperbolic flyby), or by having a LOT of mass at somewhat lower speeds. 

Adding speed makes for more heat; adding mass does not. So, I used a very very long, very very heavy vehicle with a moderately eccentric low Kerbin orbit -- apoapse up around 300 km, periapse at 17 km. 

Spent a lot longer in the atmosphere than with a hyperbolic flyby, but the way KSP handles heat, it was definitely better than the alternative.

I have a capsule, some reaction wheels, and some batteries inside the fairing. I cheated the craft into orbit and used infinite fuel to put the orbit where I wanted it, but everything else was set to normal during the actual passthrough.

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Hyperedited the craft into target orbit, everything else was nominal.

13,639 m

 

screenshot130.png < = heat shield temperature = 3456°K

Screenshots:

https://ibb.co/b8x7SG
https://ibb.co/c3VSSG
https://ibb.co/drMqgb
https://ibb.co/bSEXuw
https://ibb.co/eBpMnG
https://ibb.co/bE7Vgb 
https://ibb.co/ehai1b
https://ibb.co/jGg1nG
https://ibb.co/gxOsuw

edit: my mistake, these were copypasted from the next attempt. Here are the first attempt screenshots:

http://ibb.co/f7B0Uw
http://ibb.co/cG1yZw
http://ibb.co/mHhqUw
http://ibb.co/mTMOhG
http://ibb.co/kdDO1b
http://ibb.co/b48fUw
http://ibb.co/jd2GMb
http://ibb.co/d8MOhG
http://ibb.co/dQLupw
http://ibb.co/mm0ihG
http://ibb.co/jVbOhG  

Edited by Kulebron

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12,965 m.

screenshot210.png

Notice the heatshield @ 3474°K, 26 degrees from exploding :0.0:

All screenshots:

https://ibb.co/b8x7SG
https://ibb.co/c3VSSG
https://ibb.co/drMqgb
https://ibb.co/bSEXuw
https://ibb.co/eBpMnG
https://ibb.co/bE7Vgb
https://ibb.co/ehai1b 
https://ibb.co/jGg1nG
https://ibb.co/gxOsuw

Edited by Kulebron

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12 hours ago, Kulebron said:

So Kulebron's efforts with a near-explosive heat shield make 12,965m the new Kerbin record.

Any takers for the other planets? Eve and Jool should be interesting..

Edited by FlyingPete

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4 hours ago, FlyingPete said:

So Kulebron's efforts with a near-explosive heat shield make 12,965m the new Kerbin record.

Any takers for the other planets? Eve and Jool should be interesting..

I'll come back and beat Kulebron soon enough, then tackle the other planets.

You should reformat the leaderboard so it has 1, 2, and 3 spots (at least) for each planet.

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3 hours ago, Kulebron said:

This is already almost impossible to beat as u either need to know the surface in the area where the periapsis is or u need to be really frickin' lucky not to hit anything while passing by at such low altitude.

 

 

Might try and get involved in this too.

 

Well, so much for my participation. Can't get any lower than Kulebron without having my whole craft explode from heat either close to reaching the Periapsis or shortly after that. I even tried to only have a single ore tank survive the whole thing and coast back into space but nu-uh, not a single part survives. And the heatshields that are supposed to protect the craft and give away one after another can't even do their job properly coz some part holding them in place goes first and they fall off, leaving the rest completely unprotected. Under these circumstances why should I bother participating?

Edited by DualDesertEagle

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I think the Duna record is going to take some beating- especially with a height above ground of 47m!

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3 minutes ago, The solid fuel chemist said:

if hyperedit is allowed, couldn't you just clip thru the planet at a unreasonable speed?

Well, the idea is to fly this for real. ...And when I was tweaking the orbit, I was changing the params slowly to not put the ship close to periapsis. Couple of times it happened, and the ship exploded earlier than I moved the mouse to the mean anomaly slider.

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